/src/ntp-dev/ntpd/ntp_crypto.c

Source
/*
 * ntp_crypto.c - NTP version 4 public key routines
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef AUTOKEY
#include <stdio.h>
#include <stdlib.h> /* strtoul */
#include <sys/types.h>
#include <sys/param.h>
#include <unistd.h>
#include <fcntl.h>

#include "ntpd.h"
#include "ntp_stdlib.h"
#include "ntp_unixtime.h"
#include "ntp_string.h"
#include "ntp_random.h"
#include "ntp_assert.h"
#include "ntp_calendar.h"
#include "ntp_leapsec.h"

#include "openssl/asn1.h"
#include "openssl/bn.h"
#include "openssl/crypto.h"
#include "openssl/err.h"
#include "openssl/evp.h"
#include "openssl/opensslv.h"
#include "openssl/pem.h"
#include "openssl/rand.h"
#include "openssl/x509.h"
#include "openssl/x509v3.h"
#include "libssl_compat.h"

#ifdef KERNEL_PLL
#include "ntp_syscall.h"
#endif /* KERNEL_PLL */

/*
 * calcomp - compare two calendar structures, ignoring yearday and weekday; like strcmp
 * No, it's not a plotter.  If you don't understand that, you're too young.
 */
static int calcomp(struct calendar *pjd1, struct calendar *pjd2)
{
  int32_t diff; /* large enough to hold the signed difference between two uint16_t values */

  diff = pjd1->year - pjd2->year;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  /* same year; compare months */
  diff = pjd1->month - pjd2->month;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  /* same year and month; compare monthday */
  diff = pjd1->monthday - pjd2->monthday;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  /* same year and month and monthday; compare time */
  diff = pjd1->hour - pjd2->hour;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  diff = pjd1->minute - pjd2->minute;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  diff = pjd1->second - pjd2->second;
  if (diff < 0) return -1; else if (diff > 0) return 1;
  /* identical */
  return 0;
}

/*
 * Extension field message format
 *
 * These are always signed and saved before sending in network byte
 * order. They must be converted to and from host byte order for
 * processing.
 *
 * +-------+-------+
 * |   op  |  len  | <- extension pointer
 * +-------+-------+
 * |    associd    |
 * +---------------+
 * |   timestamp   | <- value pointer
 * +---------------+
 * |   filestamp   |
 * +---------------+
 * |   value len   |
 * +---------------+
 * |               |
 * =     value     =
 * |               |
 * +---------------+
 * | signature len |
 * +---------------+
 * |               |
 * =   signature   =
 * |               |
 * +---------------+
 *
 * The CRYPTO_RESP bit is set to 0 for requests, 1 for responses.
 * Requests carry the association ID of the receiver; responses carry
 * the association ID of the sender. Some messages include only the
 * operation/length and association ID words and so have length 8
 * octets. Ohers include the value structure and associated value and
 * signature fields. These messages include the timestamp, filestamp,
 * value and signature words and so have length at least 24 octets. The
 * signature and/or value fields can be empty, in which case the
 * respective length words are zero. An empty value with nonempty
 * signature is syntactically valid, but semantically questionable.
 *
 * The filestamp represents the time when a cryptographic data file such
 * as a public/private key pair is created. It follows every reference
 * depending on that file and serves as a means to obsolete earlier data
 * of the same type. The timestamp represents the time when the
 * cryptographic data of the message were last signed. Creation of a
 * cryptographic data file or signing a message can occur only when the
 * creator or signor is synchronized to an authoritative source and
 * proventicated to a trusted authority.
 *
 * Note there are several conditions required for server trust. First,
 * the public key on the server certificate must be verified, which can
 * involve a hike along the certificate trail to a trusted host. Next,
 * the server trust must be confirmed by one of several identity
 * schemes. Valid cryptographic values are signed with attached
 * timestamp and filestamp. Individual packet trust is confirmed
 * relative to these values by a message digest with keys generated by a
 * reverse-order pseudorandom hash.
 *
 * State decomposition. These flags are lit in the order given. They are
 * dim only when the association is demobilized.
 *
 * CRYPTO_FLAG_ENAB Lit upon acceptance of a CRYPTO_ASSOC message
 * CRYPTO_FLAG_CERT Lit when a self-digned trusted certificate is
 *      accepted.
 * CRYPTO_FLAG_VRFY Lit when identity is confirmed.
 * CRYPTO_FLAG_PROV Lit when the first signature is verified.
 * CRYPTO_FLAG_COOK Lit when a valid cookie is accepted.
 * CRYPTO_FLAG_AUTO Lit when valid autokey values are accepted.
 * CRYPTO_FLAG_SIGN Lit when the server signed certificate is
 *      accepted.
 * CRYPTO_FLAG_LEAP Lit when the leapsecond values are accepted.
 */
/*
 * Cryptodefines
 */
#define TAI_1972  10  /* initial TAI offset (s) */
#define MAX_LEAP  100 /* max UTC leapseconds (s) */
#define VALUE_LEN (6 * 4) /* min response field length */
#define MAX_VALLEN  (65535 - VALUE_LEN)
#define YEAR    (60 * 60 * 24 * 365) /* seconds in year */

/*
 * Global cryptodata in host byte order
 */
u_int32 crypto_flags = 0x0; /* status word */
int crypto_nid = KEY_TYPE_MD5; /* digest nid */
char  *sys_hostname = NULL;
char  *sys_groupname = NULL;
static char *host_filename = NULL;  /* host file name */
static char *ident_filename = NULL; /* group file name */

/*
 * Global cryptodata in network byte order
 */
struct cert_info *cinfo = NULL; /* certificate info/value cache */
struct cert_info *cert_host = NULL; /* host certificate */
struct pkey_info *pkinfo = NULL; /* key info/value cache */
struct value hostval;   /* host value */
struct value pubkey;    /* public key */
struct value tai_leap;    /* leapseconds values */
struct pkey_info *iffkey_info = NULL; /* IFF keys */
struct pkey_info *gqkey_info = NULL; /* GQ keys */
struct pkey_info *mvkey_info = NULL; /* MV keys */

/*
 * Private cryptodata in host byte order
 */
static char *passwd = NULL; /* private key password */
static EVP_PKEY *host_pkey = NULL; /* host key */
static EVP_PKEY *sign_pkey = NULL; /* sign key */
static const EVP_MD *sign_digest = NULL; /* sign digest */
static u_int sign_siglen; /* sign key length */
static char *rand_file = NULL;  /* random seed file */

/*
 * Cryptotypes
 */
static  int crypto_verify (struct exten *, struct value *,
            struct peer *);
static  int crypto_encrypt  (const u_char *, u_int, keyid_t *,
            struct value *);
static  int crypto_alice  (struct peer *, struct value *);
static  int crypto_alice2 (struct peer *, struct value *);
static  int crypto_alice3 (struct peer *, struct value *);
static  int crypto_bob  (struct exten *, struct value *);
static  int crypto_bob2 (struct exten *, struct value *);
static  int crypto_bob3 (struct exten *, struct value *);
static  int crypto_iff  (struct exten *, struct peer *);
static  int crypto_gq (struct exten *, struct peer *);
static  int crypto_mv (struct exten *, struct peer *);
static  int crypto_send (struct exten *, struct value *, int);
static  tstamp_t crypto_time  (void);
static  void  asn_to_calendar   (const ASN1_TIME *, struct calendar*);
static  struct cert_info *cert_parse (const u_char *, long, tstamp_t);
static  int cert_sign (struct exten *, struct value *);
static  struct cert_info *cert_install (struct exten *, struct peer *);
static  int cert_hike (struct peer *, struct cert_info *);
static  void  cert_free (struct cert_info *);
static  struct pkey_info *crypto_key (char *, char *, sockaddr_u *);
static  void  bighash   (BIGNUM *, BIGNUM *);
static  struct cert_info *crypto_cert (char *);
static  u_int exten_payload_size(const struct exten *);

#ifdef SYS_WINNT
int
readlink(char * link, char * file, int len) {
  return (-1);
}
#endif

/*
 * session_key - generate session key
 *
 * This routine generates a session key from the source address,
 * destination address, key ID and private value. The value of the
 * session key is the MD5 hash of these values, while the next key ID is
 * the first four octets of the hash.
 *
 * Returns the next key ID or 0 if there is no destination address.
 */
keyid_t
session_key(
  sockaddr_u *srcadr,   /* source address */
  sockaddr_u *dstadr,   /* destination address */
  keyid_t keyno,    /* key ID */
  keyid_t private,  /* private value */
  u_long  lifetime  /* key lifetime */
  )
{
  EVP_MD_CTX *ctx;  /* message digest context */
  u_char dgst[EVP_MAX_MD_SIZE]; /* message digest */
  keyid_t keyid;    /* key identifer */
  u_int32 header[10]; /* data in network byte order */
  u_int hdlen, len;

  if (!dstadr)
    return 0;
  
  /*
   * Generate the session key and key ID. If the lifetime is
   * greater than zero, install the key and call it trusted.
   */
  hdlen = 0;
  switch(AF(srcadr)) {
  case AF_INET:
    header[0] = NSRCADR(srcadr);
    header[1] = NSRCADR(dstadr);
    header[2] = htonl(keyno);
    header[3] = htonl(private);
    hdlen = 4 * sizeof(u_int32);
    break;

  case AF_INET6:
    memcpy(&header[0], PSOCK_ADDR6(srcadr),
        sizeof(struct in6_addr));
    memcpy(&header[4], PSOCK_ADDR6(dstadr),
        sizeof(struct in6_addr));
    header[8] = htonl(keyno);
    header[9] = htonl(private);
    hdlen = 10 * sizeof(u_int32);
    break;
  }
  ctx = digest_ctx;
  EVP_DigestInit(ctx, EVP_get_digestbynid(crypto_nid));
  EVP_DigestUpdate(ctx, (u_char *)header, hdlen);
  EVP_DigestFinal(ctx, dgst, &len);
  memcpy(&keyid, dgst, 4);
  keyid = ntohl(keyid);
  if (lifetime != 0) {
    MD5auth_setkey(keyno, crypto_nid, dgst, len, NULL);
    authtrust(keyno, lifetime);
  }
  DPRINTF(2, ("session_key: %s > %s %08x %08x hash %08x life %lu\n",
        stoa(srcadr), stoa(dstadr), keyno,
        private, keyid, lifetime));

  return (keyid);
}


/*
 * make_keylist - generate key list
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 *
 * This routine constructs a pseudo-random sequence by repeatedly
 * hashing the session key starting from a given source address,
 * destination address, private value and the next key ID of the
 * preceeding session key. The last entry on the list is saved along
 * with its sequence number and public signature.
 */
int
make_keylist(
  struct peer *peer,  /* peer structure pointer */
  endpt *dstadr   /* interface */
  )
{
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;  /* NTP timestamp */
  struct autokey *ap; /* autokey pointer */
  struct value *vp; /* value pointer */
  keyid_t keyid = 0;  /* next key ID */
  keyid_t cookie;   /* private value */
  long  lifetime;
  u_int len, mpoll;
  int i;

  if (!dstadr)
    return XEVNT_ERR;
  
  /*
   * Allocate the key list if necessary.
   */
  tstamp = crypto_time();
  if (peer->keylist == NULL)
    peer->keylist = eallocarray(NTP_MAXSESSION,
              sizeof(keyid_t));

  /*
   * Generate an initial key ID which is unique and greater than
   * NTP_MAXKEY.
   */
  while (1) {
    keyid = ntp_random() & 0xffffffff;
    if (keyid <= NTP_MAXKEY)
      continue;

    if (authhavekey(keyid))
      continue;
    break;
  }

  /*
   * Generate up to NTP_MAXSESSION session keys. Stop if the
   * next one would not be unique or not a session key ID or if
   * it would expire before the next poll. The private value
   * included in the hash is zero if broadcast mode, the peer
   * cookie if client mode or the host cookie if symmetric modes.
   */
  mpoll = 1U << min(peer->ppoll, peer->hpoll);
  lifetime = min((1UL << sys_automax), NTP_MAXSESSION * mpoll);
  if (peer->hmode == MODE_BROADCAST)
    cookie = 0;
  else
    cookie = peer->pcookie;
  for (i = 0; i < NTP_MAXSESSION; i++) {
    peer->keylist[i] = keyid;
    peer->keynumber = i;
    keyid = session_key(&dstadr->sin, &peer->srcadr, keyid,
        cookie, lifetime + mpoll);
    lifetime -= mpoll;
    if (auth_havekey(keyid) || keyid <= NTP_MAXKEY ||
        lifetime < 0 || tstamp == 0)
      break;
  }

  /*
   * Save the last session key ID, sequence number and timestamp,
   * then sign these values for later retrieval by the clients. Be
   * careful not to use invalid key media. Use the public values
   * timestamp as filestamp. 
   */
  vp = &peer->sndval;
  if (vp->ptr == NULL)
    vp->ptr = emalloc(sizeof(struct autokey));
  ap = (struct autokey *)vp->ptr;
  ap->seq = htonl(peer->keynumber);
  ap->key = htonl(keyid);
  vp->tstamp = htonl(tstamp);
  vp->fstamp = hostval.tstamp;
  vp->vallen = htonl(sizeof(struct autokey));
  vp->siglen = 0;
  if (tstamp != 0) {
    if (vp->sig == NULL)
      vp->sig = emalloc(sign_siglen);
    ctx = digest_ctx;
    EVP_SignInit(ctx, sign_digest);
    EVP_SignUpdate(ctx, (u_char *)vp, 12);
    EVP_SignUpdate(ctx, vp->ptr, sizeof(struct autokey));
    if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
      INSIST(len <= sign_siglen);
      vp->siglen = htonl(len);
      peer->flags |= FLAG_ASSOC;
    }
  }
  DPRINTF(1, ("make_keys: %d %08x %08x ts %u fs %u poll %d\n",
        peer->keynumber, keyid, cookie, ntohl(vp->tstamp),
        ntohl(vp->fstamp), peer->hpoll));
  return (XEVNT_OK);
}


/*
 * crypto_recv - parse extension fields
 *
 * This routine is called when the packet has been matched to an
 * association and passed sanity, format and MAC checks. We believe the
 * extension field values only if the field has proper format and
 * length, the timestamp and filestamp are valid and the signature has
 * valid length and is verified. There are a few cases where some values
 * are believed even if the signature fails, but only if the proventic
 * bit is not set.
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_LEN  bad field format or length
 */
int
crypto_recv(
  struct peer *peer,  /* peer structure pointer */
  struct recvbuf *rbufp /* packet buffer pointer */
  )
{
  const EVP_MD *dp; /* message digest algorithm */
  u_int32 *pkt;   /* receive packet pointer */
  struct autokey *ap, *bp; /* autokey pointer */
  struct exten *ep, *fp;  /* extension pointers */
  struct cert_info *xinfo; /* certificate info pointer */
  int macbytes; /* length of MAC field, signed by intention */
  int authlen;  /* offset of MAC field */
  associd_t associd;  /* association ID */
  tstamp_t fstamp = 0;  /* filestamp */
  u_int len;    /* extension field length */
  u_int code;   /* extension field opcode */
  u_int vallen = 0; /* value length */
  X509  *cert;    /* X509 certificate */
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  keyid_t cookie;   /* crumbles */
  int hismode;  /* packet mode */
  int rval = XEVNT_OK;
  const u_char *puch;
  u_int32 temp32;

  /*
   * Initialize. Note that the packet has already been checked for
   * valid format and extension field lengths. First extract the
   * field length, command code and association ID in host byte
   * order. These are used with all commands and modes. Then check
   * the version number, which must be 2, and length, which must
   * be at least 8 for requests and VALUE_LEN (24) for responses.
   * Packets that fail either test sink without a trace. The
   * association ID is saved only if nonzero.
   */
  authlen = LEN_PKT_NOMAC;
  hismode = (int)PKT_MODE((&rbufp->recv_pkt)->li_vn_mode);
  while ((macbytes = rbufp->recv_length - authlen) > (int)MAX_MAC_LEN) {
    /* We can be reasonably sure that we can read at least
     * the opcode and the size field here. More stringent
     * checks follow up shortly.
     */
    pkt = (u_int32 *)&rbufp->recv_pkt + authlen / 4;
    ep = (struct exten *)pkt;
    code = ntohl(ep->opcode) & 0xffff0000;
    len = ntohl(ep->opcode) & 0x0000ffff;
    // HMS: Why pkt[1] instead of ep->associd ?
    associd = (associd_t)ntohl(pkt[1]);
    rval = XEVNT_OK;
    DPRINTF(1, ("crypto_recv: flags 0x%x ext offset %d len %u code 0x%x associd %d\n",
          peer->crypto, authlen, len, code >> 16,
          associd));

    /*
     * Check version number and field length. If bad,
     * quietly ignore the packet.
     */
    if (((code >> 24) & 0x3f) != CRYPTO_VN || len < 8) {
      sys_badlength++;
      code |= CRYPTO_ERROR;
    }

    /* Check if the declared size fits into the remaining
     * buffer. We *know* 'macbytes' > 0 here!
     */
    if (len > (u_int)macbytes) {
      DPRINTF(1, ("crypto_recv: possible attack detected, associd %d\n",
            associd));
      return XEVNT_LEN;
    }

    /* Check if the paylod of the extension fits into the
     * declared frame.
     */
    if (len >= VALUE_LEN) {
      fstamp = ntohl(ep->fstamp);
      vallen = ntohl(ep->vallen);
      /*
       * Bug 2761: I hope this isn't too early...
       */
      if (   vallen == 0
          || len - VALUE_LEN < vallen)
        return XEVNT_LEN;
    }
    switch (code) {

    /*
     * Install status word, host name, signature scheme and
     * association ID. In OpenSSL the signature algorithm is
     * bound to the digest algorithm, so the NID completely
     * defines the signature scheme. Note the request and
     * response are identical, but neither is validated by
     * signature. The request is processed here only in
     * symmetric modes. The server name field might be
     * useful to implement access controls in future.
     */
    case CRYPTO_ASSOC:

      /*
       * If our state machine is running when this
       * message arrives, the other fellow might have
       * restarted. However, this could be an
       * intruder, so just clamp the poll interval and
       * find out for ourselves. Otherwise, pass the
       * extension field to the transmit side.
       */
      if (peer->crypto & CRYPTO_FLAG_CERT) {
        rval = XEVNT_ERR;
        break;
      }
      if (peer->cmmd) {
        if (peer->assoc != associd) {
          rval = XEVNT_ERR;
          break;
        }
        free(peer->cmmd); /* will be set again! */
      }
      fp = emalloc(len);
      memcpy(fp, ep, len);
      fp->associd = htonl(peer->associd);
      peer->cmmd = fp;
      /* fall through */

    case CRYPTO_ASSOC | CRYPTO_RESP:

      /*
       * Discard the message if it has already been
       * stored or the message has been amputated.
       */
      if (peer->crypto) {
        if (peer->assoc != associd)
          rval = XEVNT_ERR;
        break;
      }
      INSIST(len >= VALUE_LEN);
      if (vallen == 0 || vallen > MAXHOSTNAME ||
          len - VALUE_LEN < vallen) {
        rval = XEVNT_LEN;
        break;
      }
      DPRINTF(1, ("crypto_recv: ident host 0x%x %d server 0x%x %d\n",
            crypto_flags, peer->associd, fstamp,
            peer->assoc));
      temp32 = crypto_flags & CRYPTO_FLAG_MASK;

      /*
       * If the client scheme is PC, the server scheme
       * must be PC. The public key and identity are
       * presumed valid, so we skip the certificate
       * and identity exchanges and move immediately
       * to the cookie exchange which confirms the
       * server signature.
       */
      if (crypto_flags & CRYPTO_FLAG_PRIV) {
        if (!(fstamp & CRYPTO_FLAG_PRIV)) {
          rval = XEVNT_KEY;
          break;
        }
        fstamp |= CRYPTO_FLAG_CERT |
            CRYPTO_FLAG_VRFY | CRYPTO_FLAG_SIGN;

      /*
       * It is an error if either peer supports
       * identity, but the other does not.
       */
      } else if (hismode == MODE_ACTIVE || hismode ==
          MODE_PASSIVE) {
        if ((temp32 && !(fstamp &
            CRYPTO_FLAG_MASK)) ||
            (!temp32 && (fstamp &
            CRYPTO_FLAG_MASK))) {
          rval = XEVNT_KEY;
          break;
        }
      }

      /*
       * Discard the message if the signature digest
       * NID is not supported.
       */
      temp32 = (fstamp >> 16) & 0xffff;
      dp =
          (const EVP_MD *)EVP_get_digestbynid(temp32);
      if (dp == NULL) {
        rval = XEVNT_MD;
        break;
      }

      /*
       * Save status word, host name and message
       * digest/signature type. If this is from a
       * broadcast and the association ID has changed,
       * request the autokey values.
       */
      peer->assoc = associd;
      if (hismode == MODE_SERVER)
        fstamp |= CRYPTO_FLAG_AUTO;
      if (!(fstamp & CRYPTO_FLAG_TAI))
        fstamp |= CRYPTO_FLAG_LEAP;
      RAND_bytes((u_char *)&peer->hcookie, 4);
      peer->crypto = fstamp;
      peer->digest = dp;
      if (peer->subject != NULL)
        free(peer->subject);
      peer->subject = emalloc(vallen + 1);
      memcpy(peer->subject, ep->pkt, vallen);
      peer->subject[vallen] = '\0';
      if (peer->issuer != NULL)
        free(peer->issuer);
      peer->issuer = estrdup(peer->subject);
      snprintf(statstr, sizeof(statstr),
          "assoc %d %d host %s %s", peer->associd,
          peer->assoc, peer->subject,
          OBJ_nid2ln(temp32));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Decode X509 certificate in ASN.1 format and extract
     * the data containing, among other things, subject
     * name and public key. In the default identification
     * scheme, the certificate trail is followed to a self
     * signed trusted certificate.
     */
    case CRYPTO_CERT | CRYPTO_RESP:

      /*
       * Discard the message if empty or invalid.
       */
      if (len < VALUE_LEN)
        break;

      if ((rval = crypto_verify(ep, NULL, peer)) !=
          XEVNT_OK)
        break;

      /*
       * Scan the certificate list to delete old
       * versions and link the newest version first on
       * the list. Then, verify the signature. If the
       * certificate is bad or missing, just ignore
       * it.
       */
      if ((xinfo = cert_install(ep, peer)) == NULL) {
        rval = XEVNT_CRT;
        break;
      }
      if ((rval = cert_hike(peer, xinfo)) != XEVNT_OK)
        break;

      /*
       * We plug in the public key and lifetime from
       * the first certificate received. However, note
       * that this certificate might not be signed by
       * the server, so we can't check the
       * signature/digest NID.
       */
      if (peer->pkey == NULL) {
        puch = xinfo->cert.ptr;
        cert = d2i_X509(NULL, &puch,
            ntohl(xinfo->cert.vallen));
        peer->pkey = X509_get_pubkey(cert);
        X509_free(cert);
      }
      peer->flash &= ~TEST8;
      temp32 = xinfo->nid;
      snprintf(statstr, sizeof(statstr),
          "cert %s %s 0x%x %s (%u) fs %u",
          xinfo->subject, xinfo->issuer, xinfo->flags,
          OBJ_nid2ln(temp32), temp32,
          ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Schnorr (IFF) identity scheme. This scheme is
     * designed for use with shared secret server group keys
     * and where the certificate may be generated by a third
     * party. The client sends a challenge to the server,
     * which performs a calculation and returns the result.
     * A positive result is possible only if both client and
     * server contain the same secret group key.
     */
    case CRYPTO_IFF | CRYPTO_RESP:

      /*
       * Discard the message if invalid.
       */
      if ((rval = crypto_verify(ep, NULL, peer)) !=
          XEVNT_OK)
        break;

      /*
       * If the challenge matches the response, the
       * server public key, signature and identity are
       * all verified at the same time. The server is
       * declared trusted, so we skip further
       * certificate exchanges and move immediately to
       * the cookie exchange.
       */
      if ((rval = crypto_iff(ep, peer)) != XEVNT_OK)
        break;

      peer->crypto |= CRYPTO_FLAG_VRFY;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr), "iff %s fs %u",
          peer->issuer, ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Guillou-Quisquater (GQ) identity scheme. This scheme
     * is designed for use with public certificates carrying
     * the GQ public key in an extension field. The client
     * sends a challenge to the server, which performs a
     * calculation and returns the result. A positive result
     * is possible only if both client and server contain
     * the same group key and the server has the matching GQ
     * private key.
     */
    case CRYPTO_GQ | CRYPTO_RESP:

      /*
       * Discard the message if invalid
       */
      if ((rval = crypto_verify(ep, NULL, peer)) !=
          XEVNT_OK)
        break;

      /*
       * If the challenge matches the response, the
       * server public key, signature and identity are
       * all verified at the same time. The server is
       * declared trusted, so we skip further
       * certificate exchanges and move immediately to
       * the cookie exchange.
       */
      if ((rval = crypto_gq(ep, peer)) != XEVNT_OK)
        break;

      peer->crypto |= CRYPTO_FLAG_VRFY;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr), "gq %s fs %u",
          peer->issuer, ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Mu-Varadharajan (MV) identity scheme. This scheme is
     * designed for use with three levels of trust, trusted
     * host, server and client. The trusted host key is
     * opaque to servers and clients; the server keys are
     * opaque to clients and each client key is different.
     * Client keys can be revoked without requiring new key
     * generations.
     */
    case CRYPTO_MV | CRYPTO_RESP:

      /*
       * Discard the message if invalid.
       */
      if ((rval = crypto_verify(ep, NULL, peer)) !=
          XEVNT_OK)
        break;

      /*
       * If the challenge matches the response, the
       * server public key, signature and identity are
       * all verified at the same time. The server is
       * declared trusted, so we skip further
       * certificate exchanges and move immediately to
       * the cookie exchange.
       */
      if ((rval = crypto_mv(ep, peer)) != XEVNT_OK)
        break;

      peer->crypto |= CRYPTO_FLAG_VRFY;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr), "mv %s fs %u",
          peer->issuer, ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;


    /*
     * Cookie response in client and symmetric modes. If the
     * cookie bit is set, the working cookie is the EXOR of
     * the current and new values.
     */
    case CRYPTO_COOK | CRYPTO_RESP:

      /*
       * Discard the message if invalid or signature
       * not verified with respect to the cookie
       * values.
       */
      if ((rval = crypto_verify(ep, &peer->cookval,
          peer)) != XEVNT_OK)
        break;

      /*
       * Decrypt the cookie, hunting all the time for
       * errors.
       */
      if (vallen == (u_int)EVP_PKEY_size(host_pkey)) {
        RSA *rsa = EVP_PKEY_get1_RSA(host_pkey);
        u_int32 *cookiebuf = malloc(RSA_size(rsa));
        if (!cookiebuf) {
          rval = XEVNT_CKY;
          break;
        }

        if (RSA_private_decrypt(vallen,
            (u_char *)ep->pkt,
            (u_char *)cookiebuf,
            rsa,
            RSA_PKCS1_OAEP_PADDING) != 4) {
          rval = XEVNT_CKY;
          free(cookiebuf);
          break;
        } else {
          cookie = ntohl(*cookiebuf);
          free(cookiebuf);
        }
        RSA_free(rsa);
      } else {
        rval = XEVNT_CKY;
        break;
      }

      /*
       * Install cookie values and light the cookie
       * bit. If this is not broadcast client mode, we
       * are done here.
       */
      key_expire(peer);
      if (hismode == MODE_ACTIVE || hismode ==
          MODE_PASSIVE)
        peer->pcookie = peer->hcookie ^ cookie;
      else
        peer->pcookie = cookie;
      peer->crypto |= CRYPTO_FLAG_COOK;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr),
          "cook %x ts %u fs %u", peer->pcookie,
          ntohl(ep->tstamp), ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Install autokey values in broadcast client and
     * symmetric modes. We have to do this every time the
     * sever/peer cookie changes or a new keylist is
     * rolled. Ordinarily, this is automatic as this message
     * is piggybacked on the first NTP packet sent upon
     * either of these events. Note that a broadcast client
     * or symmetric peer can receive this response without a
     * matching request.
     */
    case CRYPTO_AUTO | CRYPTO_RESP:

      /*
       * Discard the message if invalid or signature
       * not verified with respect to the receive
       * autokey values.
       */
      if ((rval = crypto_verify(ep, &peer->recval,
          peer)) != XEVNT_OK) 
        break;

      /*
       * Discard the message if a broadcast client and
       * the association ID does not match. This might
       * happen if a broacast server restarts the
       * protocol. A protocol restart will occur at
       * the next ASSOC message.
       */
      if ((peer->cast_flags & MDF_BCLNT) &&
          peer->assoc != associd)
        break;

      /*
       * Install autokey values and light the
       * autokey bit. This is not hard.
       */
      if (ep->tstamp == 0)
        break;

      if (peer->recval.ptr == NULL)
        peer->recval.ptr =
            emalloc(sizeof(struct autokey));
      bp = (struct autokey *)peer->recval.ptr;
      peer->recval.tstamp = ep->tstamp;
      peer->recval.fstamp = ep->fstamp;
      ap = (struct autokey *)ep->pkt;
      bp->seq = ntohl(ap->seq);
      bp->key = ntohl(ap->key);
      peer->pkeyid = bp->key;
      peer->crypto |= CRYPTO_FLAG_AUTO;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr), 
          "auto seq %d key %x ts %u fs %u", bp->seq,
          bp->key, ntohl(ep->tstamp),
          ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;
  
    /*
     * X509 certificate sign response. Validate the
     * certificate signed by the server and install. Later
     * this can be provided to clients of this server in
     * lieu of the self signed certificate in order to
     * validate the public key.
     */
    case CRYPTO_SIGN | CRYPTO_RESP:

      /*
       * Discard the message if invalid.
       */
      if ((rval = crypto_verify(ep, NULL, peer)) !=
          XEVNT_OK)
        break;

      /*
       * Scan the certificate list to delete old
       * versions and link the newest version first on
       * the list.
       */
      if ((xinfo = cert_install(ep, peer)) == NULL) {
        rval = XEVNT_CRT;
        break;
      }
      peer->crypto |= CRYPTO_FLAG_SIGN;
      peer->flash &= ~TEST8;
      temp32 = xinfo->nid;
      snprintf(statstr, sizeof(statstr),
          "sign %s %s 0x%x %s (%u) fs %u",
          xinfo->subject, xinfo->issuer, xinfo->flags,
          OBJ_nid2ln(temp32), temp32,
          ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * Install leapseconds values. While the leapsecond
     * values epoch, TAI offset and values expiration epoch
     * are retained, only the current TAI offset is provided
     * via the kernel to other applications.
     */
    case CRYPTO_LEAP | CRYPTO_RESP:
      /*
       * Discard the message if invalid. We can't
       * compare the value timestamps here, as they
       * can be updated by different servers.
       */
      rval = crypto_verify(ep, NULL, peer);
      if ((rval   != XEVNT_OK          ) ||
          (vallen != 3*sizeof(uint32_t))  )
        break;

      /* Check if we can update the basic TAI offset
       * for our current leap frame. This is a hack
       * and ignores the time stamps in the autokey
       * message.
       */
      if (sys_leap != LEAP_NOTINSYNC)
        leapsec_autokey_tai(ntohl(ep->pkt[0]),
                rbufp->recv_time.l_ui, NULL);
      tai_leap.tstamp = ep->tstamp;
      tai_leap.fstamp = ep->fstamp;
      crypto_update();
      mprintf_event(EVNT_TAI, peer,
              "%d seconds", ntohl(ep->pkt[0]));
      peer->crypto |= CRYPTO_FLAG_LEAP;
      peer->flash &= ~TEST8;
      snprintf(statstr, sizeof(statstr),
         "leap TAI offset %d at %u expire %u fs %u",
         ntohl(ep->pkt[0]), ntohl(ep->pkt[1]),
         ntohl(ep->pkt[2]), ntohl(ep->fstamp));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      break;

    /*
     * We come here in symmetric modes for miscellaneous
     * commands that have value fields but are processed on
     * the transmit side. All we need do here is check for
     * valid field length. Note that ASSOC is handled
     * separately.
     */
    case CRYPTO_CERT:
    case CRYPTO_IFF:
    case CRYPTO_GQ:
    case CRYPTO_MV:
    case CRYPTO_COOK:
    case CRYPTO_SIGN:
      if (len < VALUE_LEN) {
        rval = XEVNT_LEN;
        break;
      }
      /* fall through */

    /*
     * We come here in symmetric modes for requests
     * requiring a response (above plus AUTO and LEAP) and
     * for responses. If a request, save the extension field
     * for later; invalid requests will be caught on the
     * transmit side. If an error or invalid response,
     * declare a protocol error.
     */
    default:
      if (code & (CRYPTO_RESP | CRYPTO_ERROR)) {
        rval = XEVNT_ERR;
      } else if (peer->cmmd == NULL) {
        fp = emalloc(len);
        memcpy(fp, ep, len);
        peer->cmmd = fp;
      }
    }

    /*
     * The first error found terminates the extension field
     * scan and we return the laundry to the caller.
     */
    if (rval != XEVNT_OK) {
      snprintf(statstr, sizeof(statstr),
          "%04x %d %02x %s", htonl(ep->opcode),
          associd, rval, eventstr(rval));
      record_crypto_stats(&peer->srcadr, statstr);
      DPRINTF(1, ("crypto_recv: %s\n", statstr));
      return (rval);
    }
    authlen += (len + 3) / 4 * 4;
  }
  return (rval);
}


/*
 * crypto_xmit - construct extension fields
 *
 * This routine is called both when an association is configured and
 * when one is not. The only case where this matters is to retrieve the
 * autokey information, in which case the caller has to provide the
 * association ID to match the association.
 *
 * Side effect: update the packet offset.
 *
 * Errors
 * XEVNT_OK success
 * XEVNT_CRT  bad or missing certificate
 * XEVNT_ERR  protocol error
 * XEVNT_LEN  bad field format or length
 * XEVNT_PER  host certificate expired
 */
int
crypto_xmit(
  struct peer *peer,  /* peer structure pointer */
  struct pkt *xpkt, /* transmit packet pointer */
  struct recvbuf *rbufp,  /* receive buffer pointer */
  int start,    /* offset to extension field */
  struct exten *ep, /* extension pointer */
  keyid_t cookie    /* session cookie */
  )
{
  struct exten *fp; /* extension pointers */
  struct cert_info *cp, *xp, *yp; /* cert info/value pointer */
  sockaddr_u *srcadr_sin; /* source address */
  u_int32 *pkt;   /* packet pointer */
  u_int opcode;   /* extension field opcode */
  char  certname[MAXHOSTNAME + 1]; /* subject name buffer */
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  tstamp_t tstamp;
  struct calendar tscal;
  u_int vallen;
  struct value vtemp;
  associd_t associd;
  int rval;
  int len;
  keyid_t tcookie;

  /*
   * Generate the requested extension field request code, length
   * and association ID. If this is a response and the host is not
   * synchronized, light the error bit and go home.
   */
  pkt = (u_int32 *)xpkt + start / 4;
  fp = (struct exten *)pkt;
  opcode = ntohl(ep->opcode);
  if (peer != NULL) {
    srcadr_sin = &peer->srcadr;
    if (!(opcode & CRYPTO_RESP))
      peer->opcode = ep->opcode;
  } else {
    srcadr_sin = &rbufp->recv_srcadr;
  }
  associd = (associd_t) ntohl(ep->associd);
  len = 8;
  fp->opcode = htonl((opcode & 0xffff0000) | len);
  fp->associd = ep->associd;
  rval = XEVNT_OK;
  tstamp = crypto_time();
  switch (opcode & 0xffff0000) {

  /*
   * Send association request and response with status word and
   * host name. Note, this message is not signed and the filestamp
   * contains only the status word.
   */
  case CRYPTO_ASSOC:
  case CRYPTO_ASSOC | CRYPTO_RESP:
    len = crypto_send(fp, &hostval, start);
    fp->fstamp = htonl(crypto_flags);
    break;

  /*
   * Send certificate request. Use the values from the extension
   * field.
   */
  case CRYPTO_CERT:
    memset(&vtemp, 0, sizeof(vtemp));
    vtemp.tstamp = ep->tstamp;
    vtemp.fstamp = ep->fstamp;
    vtemp.vallen = ep->vallen;
    vtemp.ptr = (u_char *)ep->pkt;
    len = crypto_send(fp, &vtemp, start);
    break;

  /*
   * Send sign request. Use the host certificate, which is self-
   * signed and may or may not be trusted.
   */
  case CRYPTO_SIGN:
    (void)ntpcal_ntp_to_date(&tscal, tstamp, NULL);
    if ((calcomp(&tscal, &(cert_host->first)) < 0)
    || (calcomp(&tscal, &(cert_host->last)) > 0))
      rval = XEVNT_PER;
    else
      len = crypto_send(fp, &cert_host->cert, start);
    break;

  /*
   * Send certificate response. Use the name in the extension
   * field to find the certificate in the cache. If the request
   * contains no subject name, assume the name of this host. This
   * is for backwards compatibility. Private certificates are
   * never sent.
   *
   * There may be several certificates matching the request. First
   * choice is a self-signed trusted certificate; second choice is
   * any certificate signed by another host. There is no third
   * choice. 
   */
  case CRYPTO_CERT | CRYPTO_RESP:
    vallen = exten_payload_size(ep); /* Must be <64k */
    if (vallen == 0 || vallen >= sizeof(certname) ) {
      rval = XEVNT_LEN;
      break;
    }

    /*
     * Find all public valid certificates with matching
     * subject. If a self-signed, trusted certificate is
     * found, use that certificate. If not, use the last non
     * self-signed certificate.
     */
    memcpy(certname, ep->pkt, vallen);
    certname[vallen] = '\0';
    xp = yp = NULL;
    for (cp = cinfo; cp != NULL; cp = cp->link) {
      if (cp->flags & (CERT_PRIV | CERT_ERROR))
        continue;

      if (strcmp(certname, cp->subject) != 0)
        continue;

      if (strcmp(certname, cp->issuer) != 0)
        yp = cp;
      else if (cp ->flags & CERT_TRUST)
        xp = cp;
      continue;
    }

    /*
     * Be careful who you trust. If the certificate is not
     * found, return an empty response. Note that we dont
     * enforce lifetimes here.
     *
     * The timestamp and filestamp are taken from the
     * certificate value structure. For all certificates the
     * timestamp is the latest signature update time. For
     * host and imported certificates the filestamp is the
     * creation epoch. For signed certificates the filestamp
     * is the creation epoch of the trusted certificate at
     * the root of the certificate trail. In principle, this
     * allows strong checking for signature masquerade.
     */
    if (xp == NULL)
      xp = yp;
    if (xp == NULL)
      break;

    if (tstamp == 0)
      break;

    len = crypto_send(fp, &xp->cert, start);
    break;

  /*
   * Send challenge in Schnorr (IFF) identity scheme.
   */
  case CRYPTO_IFF:
    if (peer == NULL)
      break;   /* hack attack */

    if ((rval = crypto_alice(peer, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send response in Schnorr (IFF) identity scheme.
   */
  case CRYPTO_IFF | CRYPTO_RESP:
    if ((rval = crypto_bob(ep, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send challenge in Guillou-Quisquater (GQ) identity scheme.
   */
  case CRYPTO_GQ:
    if (peer == NULL)
      break;   /* hack attack */

    if ((rval = crypto_alice2(peer, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send response in Guillou-Quisquater (GQ) identity scheme.
   */
  case CRYPTO_GQ | CRYPTO_RESP:
    if ((rval = crypto_bob2(ep, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send challenge in MV identity scheme.
   */
  case CRYPTO_MV:
    if (peer == NULL)
      break;   /* hack attack */

    if ((rval = crypto_alice3(peer, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send response in MV identity scheme.
   */
  case CRYPTO_MV | CRYPTO_RESP:
    if ((rval = crypto_bob3(ep, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send certificate sign response. The integrity of the request
   * certificate has already been verified on the receive side.
   * Sign the response using the local server key. Use the
   * filestamp from the request and use the timestamp as the
   * current time. Light the error bit if the certificate is
   * invalid or contains an unverified signature.
   */
  case CRYPTO_SIGN | CRYPTO_RESP:
    if ((rval = cert_sign(ep, &vtemp)) == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Send public key and signature. Use the values from the public
   * key.
   */
  case CRYPTO_COOK:
    len = crypto_send(fp, &pubkey, start);
    break;

  /*
   * Encrypt and send cookie and signature. Light the error bit if
   * anything goes wrong.
   */
  case CRYPTO_COOK | CRYPTO_RESP:
    vallen = ntohl(ep->vallen);  /* Must be <64k */
    if (   vallen == 0
        || (vallen >= MAX_VALLEN)
        || (opcode & 0x0000ffff)  < VALUE_LEN + vallen) {
      rval = XEVNT_LEN;
      break;
    }
    if (peer == NULL)
      tcookie = cookie;
    else
      tcookie = peer->hcookie;
    if ((rval = crypto_encrypt((const u_char *)ep->pkt, vallen, &tcookie, &vtemp))
        == XEVNT_OK) {
      len = crypto_send(fp, &vtemp, start);
      value_free(&vtemp);
    }
    break;

  /*
   * Find peer and send autokey data and signature in broadcast
   * server and symmetric modes. Use the values in the autokey
   * structure. If no association is found, either the server has
   * restarted with new associations or some perp has replayed an
   * old message, in which case light the error bit.
   */
  case CRYPTO_AUTO | CRYPTO_RESP:
    if (peer == NULL) {
      if ((peer = findpeerbyassoc(associd)) == NULL) {
        rval = XEVNT_ERR;
        break;
      }
    }
    peer->flags &= ~FLAG_ASSOC;
    len = crypto_send(fp, &peer->sndval, start);
    break;

  /*
   * Send leapseconds values and signature. Use the values from
   * the tai structure. If no table has been loaded, just send an
   * empty request.
   */
  case CRYPTO_LEAP | CRYPTO_RESP:
    len = crypto_send(fp, &tai_leap, start);
    break;

  /*
   * Default - Send a valid command for unknown requests; send
   * an error response for unknown resonses.
   */
  default:
    if (opcode & CRYPTO_RESP)
      rval = XEVNT_ERR;
  }

  /*
   * In case of error, flame the log. If a request, toss the
   * puppy; if a response, return so the sender can flame, too.
   */
  if (rval != XEVNT_OK) {
    u_int32 opcode_bits;

    opcode_bits = CRYPTO_ERROR;
    opcode |= opcode_bits;
    fp->opcode |= htonl(opcode_bits);
    snprintf(statstr, sizeof(statstr),
        "%04x %d %02x %s", opcode, associd, rval,
        eventstr(rval));
    record_crypto_stats(srcadr_sin, statstr);
    DPRINTF(1, ("crypto_xmit: %s\n", statstr));
    if (!(opcode & CRYPTO_RESP))
      return (0);
  }
  DPRINTF(1, ("crypto_xmit: flags 0x%x offset %d len %d code 0x%x associd %d\n",
        crypto_flags, start, len, opcode >> 16, associd));
  return (len);
}


/*
 * crypto_verify - verify the extension field value and signature
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_FSP  bad filestamp
 * XEVNT_LEN  bad field format or length
 * XEVNT_PUB  bad or missing public key
 * XEVNT_SGL  bad signature length
 * XEVNT_SIG  signature not verified
 * XEVNT_TSP  bad timestamp
 */
static int
crypto_verify(
  struct exten *ep, /* extension pointer */
  struct value *vp, /* value pointer */
  struct peer *peer /* peer structure pointer */
  )
{
  EVP_PKEY *pkey;   /* server public key */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp, tstamp1 = 0; /* timestamp */
  tstamp_t fstamp, fstamp1 = 0; /* filestamp */
  u_int vallen;   /* value length */
  u_int siglen;   /* signature length */
  u_int opcode, len;
  int i;

  /*
   * We are extremely parannoyed. We require valid opcode, length,
   * association ID, timestamp, filestamp, public key, digest,
   * signature length and signature, where relevant. Note that
   * preliminary length checks are done in the main loop.
   */
  len = ntohl(ep->opcode) & 0x0000ffff;
  opcode = ntohl(ep->opcode) & 0xffff0000;

  /*
   * Check for valid value header, association ID and extension
   * field length. Remember, it is not an error to receive an
   * unsolicited response; however, the response ID must match
   * the association ID.
   */
  if (opcode & CRYPTO_ERROR)
    return (XEVNT_ERR);

  if (len < VALUE_LEN)
    return (XEVNT_LEN);

  if (opcode == (CRYPTO_AUTO | CRYPTO_RESP) && (peer->pmode ==
      MODE_BROADCAST || (peer->cast_flags & MDF_BCLNT))) {
    if (ntohl(ep->associd) != peer->assoc)
      return (XEVNT_ERR);
  } else {
    if (ntohl(ep->associd) != peer->associd)
      return (XEVNT_ERR);
  }

  /*
   * We have a valid value header. Check for valid value and
   * signature field lengths. The extension field length must be
   * long enough to contain the value header, value and signature.
   * Note both the value and signature field lengths are rounded
   * up to the next word (4 octets).
   */
  vallen = ntohl(ep->vallen);
  if (   vallen == 0
      || vallen > MAX_VALLEN)
    return (XEVNT_LEN);

  i = (vallen + 3) / 4;
  siglen = ntohl(ep->pkt[i]);
  ++i;
  if (   siglen > MAX_VALLEN
      || len - VALUE_LEN < ((vallen + 3) / 4) * 4
      || len - VALUE_LEN - ((vallen + 3) / 4) * 4
        < ((siglen + 3) / 4) * 4)
    return (XEVNT_LEN);

  /*
   * Check for valid timestamp and filestamp. If the timestamp is
   * zero, the sender is not synchronized and signatures are
   * not possible. If nonzero the timestamp must not precede the
   * filestamp. The timestamp and filestamp must not precede the
   * corresponding values in the value structure, if present.
   */
  tstamp = ntohl(ep->tstamp);
  fstamp = ntohl(ep->fstamp);
  if (tstamp == 0)
    return (XEVNT_TSP);

  if (tstamp < fstamp)
    return (XEVNT_TSP);

  if (vp != NULL) {
    tstamp1 = ntohl(vp->tstamp);
    fstamp1 = ntohl(vp->fstamp);
    if (tstamp1 != 0 && fstamp1 != 0) {
      if (tstamp < tstamp1)
        return (XEVNT_TSP);

      if ((tstamp < fstamp1 || fstamp < fstamp1))
        return (XEVNT_FSP);
    }
  }

  /*
   * At the time the certificate message is validated, the public
   * key in the message is not available. Thus, don't try to
   * verify the signature.
   */
  if (opcode == (CRYPTO_CERT | CRYPTO_RESP))
    return (XEVNT_OK);

  /*
   * Check for valid signature length, public key and digest
   * algorithm.
   */
  if (crypto_flags & peer->crypto & CRYPTO_FLAG_PRIV)
    pkey = sign_pkey;
  else
    pkey = peer->pkey;
  if (siglen == 0 || pkey == NULL || peer->digest == NULL)
    return (XEVNT_ERR);

  if (siglen != (u_int)EVP_PKEY_size(pkey))
    return (XEVNT_SGL);

  /*
   * Darn, I thought we would never get here. Verify the
   * signature. If the identity exchange is verified, light the
   * proventic bit. What a relief.
   */
  ctx = digest_ctx;
  EVP_VerifyInit(ctx, peer->digest);
  EVP_VerifyUpdate(ctx, (u_char *)&ep->tstamp, vallen + 
       sizeof(ep->tstamp) + sizeof(ep->fstamp) +
       sizeof(ep->vallen));
  if (EVP_VerifyFinal(ctx, (u_char *)&ep->pkt[i], siglen,
      pkey) <= 0) {
    return (XEVNT_SIG);
  }

  if (peer->crypto & CRYPTO_FLAG_VRFY)
    peer->crypto |= CRYPTO_FLAG_PROV;
  return (XEVNT_OK);
}


/*
 * crypto_encrypt - construct vp (encrypted cookie and signature) from
 * the public key and cookie.
 *
 * Returns:
 * XEVNT_OK success
 * XEVNT_CKY  bad or missing cookie
 * XEVNT_PUB  bad or missing public key
 */
static int
crypto_encrypt(
  const u_char *ptr,  /* Public Key */
  u_int vallen,   /* Length of Public Key */
  keyid_t *cookie,  /* server cookie */
  struct value *vp  /* value pointer */
  )
{
  EVP_PKEY *pkey;   /* public key */
  RSA* rsa;   /* public key */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;  /* NTP timestamp */
  u_int32 temp32;
  u_char *puch;

  /*
   * Extract the public key from the request.
   */
  pkey = d2i_PublicKey(EVP_PKEY_RSA, NULL, &ptr, vallen);
  if (pkey == NULL) {
    msyslog(LOG_ERR, "crypto_encrypt: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_PUB);
  }

  /*
   * Encrypt the cookie, encode in ASN.1 and sign.
   */
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = hostval.tstamp;
  vallen = EVP_PKEY_size(pkey);
  vp->vallen = htonl(vallen);
  vp->ptr = emalloc(vallen);
  puch = vp->ptr;
  temp32 = htonl(*cookie);
  rsa = EVP_PKEY_get1_RSA(pkey);
  if (RSA_public_encrypt(4, (u_char *)&temp32, puch, rsa,
      RSA_PKCS1_OAEP_PADDING) <= 0) {
    msyslog(LOG_ERR, "crypto_encrypt: %s",
        ERR_error_string(ERR_get_error(), NULL));
    free(vp->ptr);
    EVP_PKEY_free(pkey);
    return (XEVNT_CKY);
  }
  EVP_PKEY_free(pkey);
  pkey = NULL;
  RSA_free(rsa);
  rsa = NULL;
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, vallen);
  if (EVP_SignFinal(ctx, vp->sig, &vallen, sign_pkey)) {
    INSIST(vallen <= sign_siglen);
    vp->siglen = htonl(vallen);
  }
  return (XEVNT_OK);
}


/*
 * crypto_ident - construct extension field for identity scheme
 *
 * This routine determines which identity scheme is in use and
 * constructs an extension field for that scheme.
 *
 * Returns
 * CRYTPO_IFF IFF scheme
 * CRYPTO_GQ  GQ scheme
 * CRYPTO_MV  MV scheme
 * CRYPTO_NULL  no available scheme
 */
u_int
crypto_ident(
  struct peer *peer /* peer structure pointer */
  )
{
  char    filename[MAXFILENAME];
  const char *  scheme_name;
  u_int   scheme_id;

  /*
   * We come here after the group trusted host has been found; its
   * name defines the group name. Search the key cache for all
   * keys matching the same group name in order IFF, GQ and MV.
   * Use the first one available.
   */
  scheme_name = NULL;
  if (peer->crypto & CRYPTO_FLAG_IFF) {
    scheme_name = "iff";
    scheme_id = CRYPTO_IFF;
  } else if (peer->crypto & CRYPTO_FLAG_GQ) {
    scheme_name = "gq";
    scheme_id = CRYPTO_GQ;
  } else if (peer->crypto & CRYPTO_FLAG_MV) {
    scheme_name = "mv";
    scheme_id = CRYPTO_MV;
  }

  if (scheme_name != NULL) {
    snprintf(filename, sizeof(filename), "ntpkey_%spar_%s",
        scheme_name, peer->ident);
    peer->ident_pkey = crypto_key(filename, NULL,
        &peer->srcadr);
    if (peer->ident_pkey != NULL)
      return scheme_id;
  }

  msyslog(LOG_NOTICE,
      "crypto_ident: no identity parameters found for group %s",
      peer->ident);

  return CRYPTO_NULL;
}


/*
 * crypto_args - construct extension field from arguments
 *
 * This routine creates an extension field with current timestamps and
 * specified opcode, association ID and optional string. Note that the
 * extension field is created here, but freed after the crypto_xmit()
 * call in the protocol module.
 *
 * Returns extension field pointer (no errors)
 *
 * XXX: opcode and len should really be 32-bit quantities and
 * we should make sure that str is not too big.
 */
struct exten *
crypto_args(
  struct peer *peer,  /* peer structure pointer */
  u_int opcode,   /* operation code */
  associd_t associd,  /* association ID */
  char  *str    /* argument string */
  )
{
  tstamp_t tstamp;  /* NTP timestamp */
  struct exten *ep; /* extension field pointer */
  u_int len;    /* extension field length */
  size_t  slen = 0;

  tstamp = crypto_time();
  len = sizeof(struct exten);
  if (str != NULL) {
    slen = strlen(str);
    INSIST(slen < MAX_VALLEN);
    len += slen;
  }
  ep = emalloc_zero(len);
  if (opcode == 0)
    return (ep);

  REQUIRE(0 == (len    & ~0x0000ffff));
  REQUIRE(0 == (opcode & ~0xffff0000));

  ep->opcode = htonl(opcode + len);
  ep->associd = htonl(associd);
  ep->tstamp = htonl(tstamp);
  ep->fstamp = hostval.tstamp;
  ep->vallen = 0;
  if (str != NULL) {
    ep->vallen = htonl(slen);
    memcpy((char *)ep->pkt, str, slen);
  }
  return (ep);
}


/*
 * crypto_send - construct extension field from value components
 *
 * The value and signature fields are zero-padded to a word boundary.
 * Note: it is not polite to send a nonempty signature with zero
 * timestamp or a nonzero timestamp with an empty signature, but those
 * rules are not enforced here.
 *
 * XXX This code won't work on a box with 16-bit ints.
 */
int
crypto_send(
  struct exten *ep, /* extension field pointer */
  struct value *vp, /* value pointer */
  int start   /* buffer offset */
  )
{
  u_int len, vallen, siglen, opcode;
  u_int i, j;

  /*
   * Calculate extension field length and check for buffer
   * overflow. Leave room for the MAC.
   */
  len = 16;       /* XXX Document! */
  vallen = ntohl(vp->vallen);
  INSIST(vallen <= MAX_VALLEN);
  len += ((vallen + 3) / 4 + 1) * 4; 
  siglen = ntohl(vp->siglen);
  len += ((siglen + 3) / 4 + 1) * 4; 
  if (start + len > sizeof(struct pkt) - MAX_MAC_LEN)
    return (0);

  /*
   * Copy timestamps.
   */
  ep->tstamp = vp->tstamp;
  ep->fstamp = vp->fstamp;
  ep->vallen = vp->vallen;

  /*
   * Copy value. If the data field is empty or zero length,
   * encode an empty value with length zero.
   */
  i = 0;
  if (vallen > 0 && vp->ptr != NULL) {
    j = vallen / 4;
    if (j * 4 < vallen)
      ep->pkt[i + j++] = 0;
    memcpy(&ep->pkt[i], vp->ptr, vallen);
    i += j;
  }

  /*
   * Copy signature. If the signature field is empty or zero
   * length, encode an empty signature with length zero.
   */
  ep->pkt[i++] = vp->siglen;
  if (siglen > 0 && vp->sig != NULL) {
    j = siglen / 4;
    if (j * 4 < siglen)
      ep->pkt[i + j++] = 0;
    memcpy(&ep->pkt[i], vp->sig, siglen);
    /* i += j; */ /* We don't use i after this */
  }
  opcode = ntohl(ep->opcode);
  ep->opcode = htonl((opcode & 0xffff0000) | len); 
  ENSURE(len <= MAX_VALLEN);
  return (len);
}


/*
 * crypto_update - compute new public value and sign extension fields
 *
 * This routine runs periodically, like once a day, and when something
 * changes. It updates the timestamps on three value structures and one
 * value structure list, then signs all the structures:
 *
 * hostval  host name (not signed)
 * pubkey public key
 * cinfo  certificate info/value list
 * tai_leap leap values
 *
 * Filestamps are proventic data, so this routine runs only when the
 * host is synchronized to a proventicated source. Thus, the timestamp
 * is proventic and can be used to deflect clogging attacks.
 *
 * Returns void (no errors)
 */
void
crypto_update(void)
{
  EVP_MD_CTX *ctx;  /* message digest context */
  struct cert_info *cp; /* certificate info/value */
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  u_int32 *ptr;
  u_int len;
  leap_result_t leap_data;

  hostval.tstamp = htonl(crypto_time());
  if (hostval.tstamp == 0)
    return;

  ctx = digest_ctx;

  /*
   * Sign public key and timestamps. The filestamp is derived from
   * the host key file extension from wherever the file was
   * generated. 
   */
  if (pubkey.vallen != 0) {
    pubkey.tstamp = hostval.tstamp;
    pubkey.siglen = 0;
    if (pubkey.sig == NULL)
      pubkey.sig = emalloc(sign_siglen);
    EVP_SignInit(ctx, sign_digest);
    EVP_SignUpdate(ctx, (u_char *)&pubkey, 12);
    EVP_SignUpdate(ctx, pubkey.ptr, ntohl(pubkey.vallen));
    if (EVP_SignFinal(ctx, pubkey.sig, &len, sign_pkey)) {
      INSIST(len <= sign_siglen);
      pubkey.siglen = htonl(len);
    }
  }

  /*
   * Sign certificates and timestamps. The filestamp is derived
   * from the certificate file extension from wherever the file
   * was generated. Note we do not throw expired certificates
   * away; they may have signed younger ones.
   */
  for (cp = cinfo; cp != NULL; cp = cp->link) {
    cp->cert.tstamp = hostval.tstamp;
    cp->cert.siglen = 0;
    if (cp->cert.sig == NULL)
      cp->cert.sig = emalloc(sign_siglen);
    EVP_SignInit(ctx, sign_digest);
    EVP_SignUpdate(ctx, (u_char *)&cp->cert, 12);
    EVP_SignUpdate(ctx, cp->cert.ptr,
        ntohl(cp->cert.vallen));
    if (EVP_SignFinal(ctx, cp->cert.sig, &len, sign_pkey)) {
      INSIST(len <= sign_siglen);
      cp->cert.siglen = htonl(len);
    }
  }

  /*
   * Sign leapseconds values and timestamps. Note it is not an
   * error to return null values.
   */
  tai_leap.tstamp = hostval.tstamp;
  tai_leap.fstamp = hostval.fstamp;

  /* Get the leap second era. We might need a full lookup early
   * after start, when the cache is not yet loaded.
   */
  leapsec_frame(&leap_data);
  if ( ! memcmp(&leap_data.ebase, &leap_data.ttime, sizeof(vint64))) {
    time_t   now    = time(NULL);
    uint32_t nowntp = (uint32_t)now + JAN_1970;
    leapsec_query(&leap_data, nowntp, &now);
  }

  /* Create the data block. The protocol does not work without. */
  len = 3 * sizeof(u_int32);
  if (tai_leap.ptr == NULL || ntohl(tai_leap.vallen) != len) {
    free(tai_leap.ptr);
    tai_leap.ptr = emalloc(len);
    tai_leap.vallen = htonl(len);
  }
  ptr = (u_int32 *)tai_leap.ptr;
  if (leap_data.tai_offs > 10) {
    /* create a TAI / leap era block. The end time is a
     * fake -- maybe we can do better.
     */
    ptr[0] = htonl(leap_data.tai_offs);
    ptr[1] = htonl(leap_data.ebase.d_s.lo);
    if (leap_data.ttime.d_s.hi >= 0)
      ptr[2] = htonl(leap_data.ttime.D_s.lo +  7*86400);
    else
      ptr[2] = htonl(leap_data.ebase.D_s.lo + 25*86400);
  } else {
    /* no leap era available */
    memset(ptr, 0, len);
  }
  if (tai_leap.sig == NULL)
    tai_leap.sig = emalloc(sign_siglen);
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&tai_leap, 12);
  EVP_SignUpdate(ctx, tai_leap.ptr, len);
  if (EVP_SignFinal(ctx, tai_leap.sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    tai_leap.siglen = htonl(len);
  }
  crypto_flags |= CRYPTO_FLAG_TAI;

  snprintf(statstr, sizeof(statstr), "signature update ts %u",
      ntohl(hostval.tstamp)); 
  record_crypto_stats(NULL, statstr);
  DPRINTF(1, ("crypto_update: %s\n", statstr));
}

/*
 * crypto_update_taichange - eventually trigger crypto_update
 *
 * This is called when a change in 'sys_tai' is detected. This will
 * happen shortly after a leap second is detected, but unhappily also
 * early after system start; also, the crypto stuff might be unused and
 * an unguarded call to crypto_update() causes a crash.
 *
 * This function makes sure that there already *is* a valid crypto block
 * for the use with autokey, and only calls 'crypto_update()' if it can
 * succeed.
 *
 * Returns void (no errors)
 */
void
crypto_update_taichange(void)
{
  static const u_int len = 3 * sizeof(u_int32);

  /* check if the signing digest algo is available */
  if (sign_digest == NULL || sign_pkey == NULL)
    return;

  /* check size of TAI extension block */
  if (tai_leap.ptr == NULL || ntohl(tai_leap.vallen) != len)
    return;

  /* crypto_update should at least not crash here! */
  crypto_update();
}

/*
 * value_free - free value structure components.
 *
 * Returns void (no errors)
 */
void
value_free(
  struct value *vp  /* value structure */
  )
{
  if (vp->ptr != NULL)
    free(vp->ptr);
  if (vp->sig != NULL)
    free(vp->sig);
  memset(vp, 0, sizeof(struct value));
}


/*
 * crypto_time - returns current NTP time.
 *
 * Returns NTP seconds if in synch, 0 otherwise
 */
tstamp_t
crypto_time(void)
{
  l_fp  tstamp;   /* NTP time */

  L_CLR(&tstamp);
  if (sys_leap != LEAP_NOTINSYNC)
    get_systime(&tstamp);
  return (tstamp.l_ui);
}


/*
 * asn_to_calendar - convert ASN1_TIME time structure to struct calendar.
 *
 */
static
void
asn_to_calendar (
  const ASN1_TIME *asn1time,  /* pointer to ASN1_TIME structure */
  struct calendar *pjd  /* pointer to result */
  )
{
  size_t  len;    /* length of ASN1_TIME string */
  char  v[24];    /* writable copy of ASN1_TIME string */
  unsigned long temp; /* result from strtoul */

  /*
   * Extract time string YYMMDDHHMMSSZ from ASN1 time structure.
   * Or YYYYMMDDHHMMSSZ.
   * Note that the YY, MM, DD fields start with one, the HH, MM,
   * SS fields start with zero and the Z character is ignored.
   * Also note that two-digit years less than 50 map to years greater than
   * 100. Dontcha love ASN.1? Better than MIL-188.
   */
  len = asn1time->length;
  REQUIRE(len < sizeof(v));
  (void)strncpy(v, (char *)(asn1time->data), len);
  REQUIRE(len >= 13);
  temp = strtoul(v+len-3, NULL, 10);
  pjd->second = temp;
  v[len-3] = '\0';

  temp = strtoul(v+len-5, NULL, 10);
  pjd->minute = temp;
  v[len-5] = '\0';

  temp = strtoul(v+len-7, NULL, 10);
  pjd->hour = temp;
  v[len-7] = '\0';

  temp = strtoul(v+len-9, NULL, 10);
  pjd->monthday = temp;
  v[len-9] = '\0';

  temp = strtoul(v+len-11, NULL, 10);
  pjd->month = temp;
  v[len-11] = '\0';

  temp = strtoul(v, NULL, 10);
  /* handle two-digit years */
  if (temp < 50UL)
      temp += 100UL;
  if (temp < 150UL)
      temp += 1900UL;
  pjd->year = temp;

  pjd->yearday = pjd->weekday = 0;
  return;
}


/*
 * bighash() - compute a BIGNUM MD5 hash of a BIGNUM number.
 *
 * Returns void (no errors)
 */
static void
bighash(
  BIGNUM  *bn,    /* BIGNUM * from */
  BIGNUM  *bk   /* BIGNUM * to */
  )
{
  EVP_MD_CTX *ctx;  /* message digest context */
  u_char dgst[EVP_MAX_MD_SIZE]; /* message digest */
  u_char  *ptr;   /* a BIGNUM as binary string */
  u_int len;

  len = BN_num_bytes(bn);
  ptr = emalloc(len);
  BN_bn2bin(bn, ptr);
  ctx = digest_ctx;
  EVP_DigestInit(ctx, EVP_md5());
  EVP_DigestUpdate(ctx, ptr, len);
  EVP_DigestFinal(ctx, dgst, &len);
  BN_bin2bn(dgst, len, bk);
  free(ptr);
}


/*
 ***********************************************************************
 *                       *
 * The following routines implement the Schnorr (IFF) identity scheme  *
 *                       *
 ***********************************************************************
 *
 * The Schnorr (IFF) identity scheme is intended for use when
 * certificates are generated by some other trusted certificate
 * authority and the certificate cannot be used to convey public
 * parameters. There are two kinds of files: encrypted server files that
 * contain private and public values and nonencrypted client files that
 * contain only public values. New generations of server files must be
 * securely transmitted to all servers of the group; client files can be
 * distributed by any means. The scheme is self contained and
 * independent of new generations of host keys, sign keys and
 * certificates.
 *
 * The IFF values hide in a DSA cuckoo structure which uses the same
 * parameters. The values are used by an identity scheme based on DSA
 * cryptography and described in Stimson p. 285. The p is a 512-bit
 * prime, g a generator of Zp* and q a 160-bit prime that divides p - 1
 * and is a qth root of 1 mod p; that is, g^q = 1 mod p. The TA rolls a
 * private random group key b (0 < b < q) and public key v = g^b, then
 * sends (p, q, g, b) to the servers and (p, q, g, v) to the clients.
 * Alice challenges Bob to confirm identity using the protocol described
 * below.
 *
 * How it works
 *
 * The scheme goes like this. Both Alice and Bob have the public primes
 * p, q and generator g. The TA gives private key b to Bob and public
 * key v to Alice.
 *
 * Alice rolls new random challenge r (o < r < q) and sends to Bob in
 * the IFF request message. Bob rolls new random k (0 < k < q), then
 * computes y = k + b r mod q and x = g^k mod p and sends (y, hash(x))
 * to Alice in the response message. Besides making the response
 * shorter, the hash makes it effectivey impossible for an intruder to
 * solve for b by observing a number of these messages.
 * 
 * Alice receives the response and computes g^y v^r mod p. After a bit
 * of algebra, this simplifies to g^k. If the hash of this result
 * matches hash(x), Alice knows that Bob has the group key b. The signed
 * response binds this knowledge to Bob's private key and the public key
 * previously received in his certificate.
 *
 * crypto_alice - construct Alice's challenge in IFF scheme
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ID bad or missing group key
 * XEVNT_PUB  bad or missing public key
 */
static int
crypto_alice(
  struct peer *peer,  /* peer pointer */
  struct value *vp  /* value pointer */
  )
{
  const DSA *dsa;   /* IFF parameters */
  BN_CTX    *bctx;    /* BIGNUM context */
  EVP_MD_CTX  *ctx; /* signature context */
  tstamp_t  tstamp;
  u_int   len;
  const BIGNUM  *q;

  /*
   * The identity parameters must have correct format and content.
   */
  if (peer->ident_pkey == NULL) {
    msyslog(LOG_NOTICE, "crypto_alice: scheme unavailable");
    return (XEVNT_ID);
  }

  if ((dsa = EVP_PKEY_get0_DSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_alice: defective key");
    return (XEVNT_PUB);
  }

  /*
   * Roll new random r (0 < r < q).
   */
  if (peer->iffval != NULL)
    BN_free(peer->iffval);
  peer->iffval = BN_new();
  DSA_get0_pqg(dsa, NULL, &q, NULL);
  len = BN_num_bytes(q);
  BN_rand(peer->iffval, len * 8, -1, 1);  /* r mod q*/
  bctx = BN_CTX_new();
  BN_mod(peer->iffval, peer->iffval, q, bctx);
  BN_CTX_free(bctx);

  /*
   * Sign and send to Bob. The filestamp is from the local file.
   */
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(peer->ident_pkey->fstamp);
  vp->vallen = htonl(len);
  vp->ptr = emalloc(len);
  BN_bn2bin(peer->iffval, vp->ptr);
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx; 
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  return (XEVNT_OK);
}


/*
 * crypto_bob - construct Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_ID bad or missing group key
 */
static int
crypto_bob(
  struct exten *ep, /* extension pointer */
  struct value *vp  /* value pointer */
  )
{
  int retv;   /* return value */
  const DSA *dsa;   /* IFF parameters */
  DSA_SIG *sdsa;    /* DSA signature context fake */
  BN_CTX  *bctx;    /* BIGNUM context */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;  /* NTP timestamp */
  BIGNUM  *bn, *bk, *r;
  u_char  *ptr;
  u_int len;    /* extension field value length */
  const BIGNUM *p, *q, *g;
  const BIGNUM *priv_key;

  /*
   * If the IFF parameters are not valid, something awful
   * happened or we are being tormented.
   */
  if (iffkey_info == NULL) {
    msyslog(LOG_NOTICE, "crypto_bob: scheme unavailable");
    return (XEVNT_ID);
  }

  /* Initialize pointers that may need freeing in cleanup. */
  sdsa = NULL;

  dsa = EVP_PKEY_get0_DSA(iffkey_info->pkey);
  DSA_get0_pqg(dsa, &p, &q, &g);
  DSA_get0_key(dsa, NULL, &priv_key);

  /*
   * Extract r from the challenge.
   */
  len = exten_payload_size(ep);
  if (len == 0 || len > MAX_VALLEN)
    return (XEVNT_LEN);
  if ((r = BN_bin2bn((u_char *)ep->pkt, len, NULL)) == NULL) {
    msyslog(LOG_ERR, "crypto_bob: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }

  /*
   * Bob rolls random k (0 < k < q), computes y = k + b r mod q
   * and x = g^k mod p, then sends (y, hash(x)) to Alice.
   */
  bctx = BN_CTX_new(); bk = BN_new(); bn = BN_new();
  sdsa = DSA_SIG_new();
  BN_rand(bk, len * 8, -1, 1);    /* k */
  BN_mod_mul(bn, priv_key, r, q, bctx); /* b r mod q */
  BN_add(bn, bn, bk);
  BN_mod(bn, bn, q, bctx);    /* k + b r mod q */
  BN_mod_exp(bk, g, bk, p, bctx); /* g^k mod p */
  bighash(bk, bk);
  DSA_SIG_set0(sdsa, bn, bk);
  BN_CTX_free(bctx);
  BN_free(r);
#ifdef DEBUG
  if (debug > 1)
    DSA_print_fp(stdout, dsa, 0);
#endif

  /*
   * Encode the values in ASN.1 and sign. The filestamp is from
   * the local file.
   */
  len = i2d_DSA_SIG(sdsa, NULL);
  if (len == 0) {
    msyslog(LOG_ERR, "crypto_bob: %s",
        ERR_error_string(ERR_get_error(), NULL));
    retv = XEVNT_ERR;
    goto cleanup;
  }
  if (len > MAX_VALLEN) {
    msyslog(LOG_ERR, "crypto_bob: signature is too big: %u",
        len);
    retv = XEVNT_ERR;
    goto cleanup;
  }
  ZERO(*vp);
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(iffkey_info->fstamp);
  vp->vallen = htonl(len);
  ptr = emalloc(len);
  vp->ptr = ptr;
  i2d_DSA_SIG(sdsa, &ptr);
  if (0 == tstamp) {
    retv = XEVNT_OK;
    goto cleanup;
  }

  /* XXX: more validation to make sure the sign fits... */
  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  retv = XEVNT_OK;

    cleanup:
  DSA_SIG_free(sdsa);
  return retv;
}


/*
 * crypto_iff - verify Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_FSP  bad filestamp
 * XEVNT_ID bad or missing group key
 * XEVNT_PUB  bad or missing public key
 */
int
crypto_iff(
  struct exten *ep, /* extension pointer */
  struct peer *peer /* peer structure pointer */
  )
{
  const DSA *dsa;   /* IFF parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  DSA_SIG *sdsa;    /* DSA parameters */
  BIGNUM  *bn, *bk;
  u_int len;
  const u_char *ptr;
  int temp;
  const BIGNUM *p, *g;
  const BIGNUM *r, *s;
  const BIGNUM *pub_key;

  /*
   * If the IFF parameters are not valid or no challenge was sent,
   * something awful happened or we are being tormented.
   */
  if (peer->ident_pkey == NULL) {
    msyslog(LOG_NOTICE, "crypto_iff: scheme unavailable");
    return (XEVNT_ID);
  }
  if (ntohl(ep->fstamp) != peer->ident_pkey->fstamp) {
    msyslog(LOG_NOTICE, "crypto_iff: invalid filestamp %u",
        ntohl(ep->fstamp));
    return (XEVNT_FSP);
  }
  if ((dsa = EVP_PKEY_get0_DSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_iff: defective key");
    return (XEVNT_PUB);
  }
  if (peer->iffval == NULL) {
    msyslog(LOG_NOTICE, "crypto_iff: missing challenge");
    return (XEVNT_ID);
  }

  /*
   * Extract the k + b r and g^k values from the response.
   */
  bctx = BN_CTX_new(); bk = BN_new(); bn = BN_new();
  len = ntohl(ep->vallen);
  ptr = (u_char *)ep->pkt;
  if ((sdsa = d2i_DSA_SIG(NULL, &ptr, len)) == NULL) {
    BN_free(bn); BN_free(bk); BN_CTX_free(bctx);
    msyslog(LOG_ERR, "crypto_iff: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }

  /*
   * Compute g^(k + b r) g^(q - b)r mod p.
   */
  DSA_get0_key(dsa, &pub_key, NULL);
  DSA_get0_pqg(dsa, &p, NULL, &g);
  DSA_SIG_get0(sdsa, &r, &s);
  BN_mod_exp(bn, pub_key, peer->iffval, p, bctx);
  BN_mod_exp(bk, g, r, p, bctx);
  BN_mod_mul(bn, bn, bk, p, bctx);

  /*
   * Verify the hash of the result matches hash(x).
   */
  bighash(bn, bn);
  temp = BN_cmp(bn, s);
  BN_free(bn); BN_free(bk); BN_CTX_free(bctx);
  BN_free(peer->iffval);
  peer->iffval = NULL;
  DSA_SIG_free(sdsa);
  if (temp == 0)
    return (XEVNT_OK);

  msyslog(LOG_NOTICE, "crypto_iff: identity not verified");
  return (XEVNT_ID);
}


/*
 ***********************************************************************
 *                       *
 * The following routines implement the Guillou-Quisquater (GQ)        *
 * identity scheme                                                     *
 *                       *
 ***********************************************************************
 *
 * The Guillou-Quisquater (GQ) identity scheme is intended for use when
 * the certificate can be used to convey public parameters. The scheme
 * uses a X509v3 certificate extension field do convey the public key of
 * a private key known only to servers. There are two kinds of files:
 * encrypted server files that contain private and public values and
 * nonencrypted client files that contain only public values. New
 * generations of server files must be securely transmitted to all
 * servers of the group; client files can be distributed by any means.
 * The scheme is self contained and independent of new generations of
 * host keys and sign keys. The scheme is self contained and independent
 * of new generations of host keys and sign keys.
 *
 * The GQ parameters hide in a RSA cuckoo structure which uses the same
 * parameters. The values are used by an identity scheme based on RSA
 * cryptography and described in Stimson p. 300 (with errors). The 512-
 * bit public modulus is n = p q, where p and q are secret large primes.
 * The TA rolls private random group key b as RSA exponent. These values
 * are known to all group members.
 *
 * When rolling new certificates, a server recomputes the private and
 * public keys. The private key u is a random roll, while the public key
 * is the inverse obscured by the group key v = (u^-1)^b. These values
 * replace the private and public keys normally generated by the RSA
 * scheme. Alice challenges Bob to confirm identity using the protocol
 * described below.
 *
 * How it works
 *
 * The scheme goes like this. Both Alice and Bob have the same modulus n
 * and some random b as the group key. These values are computed and
 * distributed in advance via secret means, although only the group key
 * b is truly secret. Each has a private random private key u and public
 * key (u^-1)^b, although not necessarily the same ones. Bob and Alice
 * can regenerate the key pair from time to time without affecting
 * operations. The public key is conveyed on the certificate in an
 * extension field; the private key is never revealed.
 *
 * Alice rolls new random challenge r and sends to Bob in the GQ
 * request message. Bob rolls new random k, then computes y = k u^r mod
 * n and x = k^b mod n and sends (y, hash(x)) to Alice in the response
 * message. Besides making the response shorter, the hash makes it
 * effectivey impossible for an intruder to solve for b by observing
 * a number of these messages.
 * 
 * Alice receives the response and computes y^b v^r mod n. After a bit
 * of algebra, this simplifies to k^b. If the hash of this result
 * matches hash(x), Alice knows that Bob has the group key b. The signed
 * response binds this knowledge to Bob's private key and the public key
 * previously received in his certificate.
 *
 * crypto_alice2 - construct Alice's challenge in GQ scheme
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ID bad or missing group key
 * XEVNT_PUB  bad or missing public key
 */
static int
crypto_alice2(
  struct peer *peer,  /* peer pointer */
  struct value *vp  /* value pointer */
  )
{
  const RSA *rsa; /* GQ parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;
  u_int len;
  const BIGNUM *n;

  /*
   * The identity parameters must have correct format and content.
   */
  if (peer->ident_pkey == NULL)
    return (XEVNT_ID);

  if ((rsa = EVP_PKEY_get0_RSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_alice2: defective key");
    return (XEVNT_PUB);
  }

  /*
   * Roll new random r (0 < r < n).
   */
  if (peer->iffval != NULL)
    BN_free(peer->iffval);
  peer->iffval = BN_new();
  RSA_get0_key(rsa, &n, NULL, NULL);
  len = BN_num_bytes(n);
  BN_rand(peer->iffval, len * 8, -1, 1);  /* r mod n */
  bctx = BN_CTX_new();
  BN_mod(peer->iffval, peer->iffval, n, bctx);
  BN_CTX_free(bctx);

  /*
   * Sign and send to Bob. The filestamp is from the local file.
   */
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(peer->ident_pkey->fstamp);
  vp->vallen = htonl(len);
  vp->ptr = emalloc(len);
  BN_bn2bin(peer->iffval, vp->ptr);
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  return (XEVNT_OK);
}


/*
 * crypto_bob2 - construct Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_ID bad or missing group key
 */
static int
crypto_bob2(
  struct exten *ep, /* extension pointer */
  struct value *vp  /* value pointer */
  )
{
  const RSA *rsa;   /* GQ parameters */
  DSA_SIG *sdsa;    /* DSA parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;  /* NTP timestamp */
  BIGNUM  *r, *k, *g, *y;
  u_char  *ptr;
  u_int len;
  int s_len;
  const BIGNUM *n, *p, *e;

  /*
   * If the GQ parameters are not valid, something awful
   * happened or we are being tormented.
   */
  if (gqkey_info == NULL) {
    msyslog(LOG_NOTICE, "crypto_bob2: scheme unavailable");
    return (XEVNT_ID);
  }
  rsa = EVP_PKEY_get0_RSA(gqkey_info->pkey);
  RSA_get0_key(rsa, &n, &p, &e);

  /*
   * Extract r from the challenge.
   */
  len = exten_payload_size(ep);
  if (len == 0 || len > MAX_VALLEN)
    return (XEVNT_LEN);
  if ((r = BN_bin2bn((u_char *)ep->pkt, len, NULL)) == NULL) {
    msyslog(LOG_ERR, "crypto_bob2: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }

  /*
   * Bob rolls random k (0 < k < n), computes y = k u^r mod n and
   * x = k^b mod n, then sends (y, hash(x)) to Alice. 
   */
  bctx = BN_CTX_new(); k = BN_new(); g = BN_new(); y = BN_new();
  sdsa = DSA_SIG_new();
  BN_rand(k, len * 8, -1, 1);   /* k */
  BN_mod(k, k, n, bctx);
  BN_mod_exp(y, p, r, n, bctx); /* u^r mod n */
  BN_mod_mul(y, k, y, n, bctx); /* k u^r mod n */
  BN_mod_exp(g, k, e, n, bctx); /* k^b mod n */
  bighash(g, g);
  DSA_SIG_set0(sdsa, y, g);
  BN_CTX_free(bctx);
  BN_free(r); BN_free(k);
#ifdef DEBUG
  if (debug > 1)
    RSA_print_fp(stdout, rsa, 0);
#endif
 
  /*
   * Encode the values in ASN.1 and sign. The filestamp is from
   * the local file.
   */
  len = s_len = i2d_DSA_SIG(sdsa, NULL);
  if (s_len <= 0) {
    msyslog(LOG_ERR, "crypto_bob2: %s",
        ERR_error_string(ERR_get_error(), NULL));
    DSA_SIG_free(sdsa);
    return (XEVNT_ERR);
  }
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(gqkey_info->fstamp);
  vp->vallen = htonl(len);
  ptr = emalloc(len);
  vp->ptr = ptr;
  i2d_DSA_SIG(sdsa, &ptr);
  DSA_SIG_free(sdsa);
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  return (XEVNT_OK);
}


/*
 * crypto_gq - verify Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_FSP  bad filestamp
 * XEVNT_ID bad or missing group keys
 * XEVNT_PUB  bad or missing public key
 */
int
crypto_gq(
  struct exten *ep, /* extension pointer */
  struct peer *peer /* peer structure pointer */
  )
{
  const RSA *rsa;   /* GQ parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  DSA_SIG *sdsa;    /* RSA signature context fake */
  BIGNUM  *y, *v;
  const u_char *ptr;
  long  len;
  u_int temp;
  const BIGNUM *n, *e;
  const BIGNUM *r, *s;

  /*
   * If the GQ parameters are not valid or no challenge was sent,
   * something awful happened or we are being tormented. Note that
   * the filestamp on the local key file can be greater than on
   * the remote parameter file if the keys have been refreshed.
   */
  if (peer->ident_pkey == NULL) {
    msyslog(LOG_NOTICE, "crypto_gq: scheme unavailable");
    return (XEVNT_ID);
  }
  if (ntohl(ep->fstamp) < peer->ident_pkey->fstamp) {
    msyslog(LOG_NOTICE, "crypto_gq: invalid filestamp %u",
        ntohl(ep->fstamp));
    return (XEVNT_FSP);
  }
  if ((rsa = EVP_PKEY_get0_RSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_gq: defective key");
    return (XEVNT_PUB);
  }
  RSA_get0_key(rsa, &n, NULL, &e);
  if (peer->iffval == NULL) {
    msyslog(LOG_NOTICE, "crypto_gq: missing challenge");
    return (XEVNT_ID);
  }

  /*
   * Extract the y = k u^r and hash(x = k^b) values from the
   * response.
   */
  bctx = BN_CTX_new(); y = BN_new(); v = BN_new();
  len = ntohl(ep->vallen);
  ptr = (u_char *)ep->pkt;
  if ((sdsa = d2i_DSA_SIG(NULL, &ptr, len)) == NULL) {
    BN_CTX_free(bctx); BN_free(y); BN_free(v);
    msyslog(LOG_ERR, "crypto_gq: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }
  DSA_SIG_get0(sdsa, &r, &s);

  /*
   * Compute v^r y^b mod n.
   */
  if (peer->grpkey == NULL) {
    msyslog(LOG_NOTICE, "crypto_gq: missing group key");
    return (XEVNT_ID);
  }
  BN_mod_exp(v, peer->grpkey, peer->iffval, n, bctx);
            /* v^r mod n */
  BN_mod_exp(y, r, e, n, bctx); /* y^b mod n */
  BN_mod_mul(y, v, y, n, bctx); /* v^r y^b mod n */

  /*
   * Verify the hash of the result matches hash(x).
   */
  bighash(y, y);
  temp = BN_cmp(y, s);
  BN_CTX_free(bctx); BN_free(y); BN_free(v);
  BN_free(peer->iffval);
  peer->iffval = NULL;
  DSA_SIG_free(sdsa);
  if (temp == 0)
    return (XEVNT_OK);

  msyslog(LOG_NOTICE, "crypto_gq: identity not verified");
  return (XEVNT_ID);
}


/*
 ***********************************************************************
 *                       *
 * The following routines implement the Mu-Varadharajan (MV) identity  *
 * scheme                                                              *
 *                       *
 ***********************************************************************
 *
 * The Mu-Varadharajan (MV) cryptosystem was originally intended when
 * servers broadcast messages to clients, but clients never send
 * messages to servers. There is one encryption key for the server and a
 * separate decryption key for each client. It operated something like a
 * pay-per-view satellite broadcasting system where the session key is
 * encrypted by the broadcaster and the decryption keys are held in a
 * tamperproof set-top box.
 *
 * The MV parameters and private encryption key hide in a DSA cuckoo
 * structure which uses the same parameters, but generated in a
 * different way. The values are used in an encryption scheme similar to
 * El Gamal cryptography and a polynomial formed from the expansion of
 * product terms (x - x[j]), as described in Mu, Y., and V.
 * Varadharajan: Robust and Secure Broadcasting, Proc. Indocrypt 2001,
 * 223-231. The paper has significant errors and serious omissions.
 *
 * Let q be the product of n distinct primes s1[j] (j = 1...n), where
 * each s1[j] has m significant bits. Let p be a prime p = 2 * q + 1, so
 * that q and each s1[j] divide p - 1 and p has M = n * m + 1
 * significant bits. Let g be a generator of Zp; that is, gcd(g, p - 1)
 * = 1 and g^q = 1 mod p. We do modular arithmetic over Zq and then
 * project into Zp* as exponents of g. Sometimes we have to compute an
 * inverse b^-1 of random b in Zq, but for that purpose we require
 * gcd(b, q) = 1. We expect M to be in the 500-bit range and n
 * relatively small, like 30. These are the parameters of the scheme and
 * they are expensive to compute.
 *
 * We set up an instance of the scheme as follows. A set of random
 * values x[j] mod q (j = 1...n), are generated as the zeros of a
 * polynomial of order n. The product terms (x - x[j]) are expanded to
 * form coefficients a[i] mod q (i = 0...n) in powers of x. These are
 * used as exponents of the generator g mod p to generate the private
 * encryption key A. The pair (gbar, ghat) of public server keys and the
 * pairs (xbar[j], xhat[j]) (j = 1...n) of private client keys are used
 * to construct the decryption keys. The devil is in the details.
 *
 * This routine generates a private server encryption file including the
 * private encryption key E and partial decryption keys gbar and ghat.
 * It then generates public client decryption files including the public
 * keys xbar[j] and xhat[j] for each client j. The partial decryption
 * files are used to compute the inverse of E. These values are suitably
 * blinded so secrets are not revealed.
 *
 * The distinguishing characteristic of this scheme is the capability to
 * revoke keys. Included in the calculation of E, gbar and ghat is the
 * product s = prod(s1[j]) (j = 1...n) above. If the factor s1[j] is
 * subsequently removed from the product and E, gbar and ghat
 * recomputed, the jth client will no longer be able to compute E^-1 and
 * thus unable to decrypt the messageblock.
 *
 * How it works
 *
 * The scheme goes like this. Bob has the server values (p, E, q, gbar,
 * ghat) and Alice has the client values (p, xbar, xhat).
 *
 * Alice rolls new random nonce r mod p and sends to Bob in the MV
 * request message. Bob rolls random nonce k mod q, encrypts y = r E^k
 * mod p and sends (y, gbar^k, ghat^k) to Alice.
 * 
 * Alice receives the response and computes the inverse (E^k)^-1 from
 * the partial decryption keys gbar^k, ghat^k, xbar and xhat. She then
 * decrypts y and verifies it matches the original r. The signed
 * response binds this knowledge to Bob's private key and the public key
 * previously received in his certificate.
 *
 * crypto_alice3 - construct Alice's challenge in MV scheme
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ID bad or missing group key
 * XEVNT_PUB  bad or missing public key
 */
static int
crypto_alice3(
  struct peer *peer,  /* peer pointer */
  struct value *vp  /* value pointer */
  )
{
  const DSA *dsa;   /* MV parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;
  u_int len;
  const BIGNUM *p;

  /*
   * The identity parameters must have correct format and content.
   */
  if (peer->ident_pkey == NULL)
    return (XEVNT_ID);

  if ((dsa = EVP_PKEY_get0_DSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_alice3: defective key");
    return (XEVNT_PUB);
  }
  DSA_get0_pqg(dsa, &p, NULL, NULL);

  /*
   * Roll new random r (0 < r < q).
   */
  if (peer->iffval != NULL)
    BN_free(peer->iffval);
  peer->iffval = BN_new();
  len = BN_num_bytes(p);
  BN_rand(peer->iffval, len * 8, -1, 1);  /* r mod p */
  bctx = BN_CTX_new();
  BN_mod(peer->iffval, peer->iffval, p, bctx);
  BN_CTX_free(bctx);

  /*
   * Sign and send to Bob. The filestamp is from the local file.
   */
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(peer->ident_pkey->fstamp);
  vp->vallen = htonl(len);
  vp->ptr = emalloc(len);
  BN_bn2bin(peer->iffval, vp->ptr);
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  return (XEVNT_OK);
}


/*
 * crypto_bob3 - construct Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 */
static int
crypto_bob3(
  struct exten *ep, /* extension pointer */
  struct value *vp  /* value pointer */
  )
{
  const DSA *dsa;   /* MV parameters */
  DSA *sdsa;    /* DSA signature context fake */
  BN_CTX  *bctx;    /* BIGNUM context */
  EVP_MD_CTX *ctx;  /* signature context */
  tstamp_t tstamp;  /* NTP timestamp */
  BIGNUM  *r, *k, *u;
  u_char  *ptr;
  u_int len;
  const BIGNUM *p, *q, *g;
  const BIGNUM *pub_key, *priv_key;
  BIGNUM *sp, *sq, *sg;

  /*
   * If the MV parameters are not valid, something awful
   * happened or we are being tormented.
   */
  if (mvkey_info == NULL) {
    msyslog(LOG_NOTICE, "crypto_bob3: scheme unavailable");
    return (XEVNT_ID);
  }
  dsa = EVP_PKEY_get0_DSA(mvkey_info->pkey);
  DSA_get0_pqg(dsa, &p, &q, &g);
  DSA_get0_key(dsa, &pub_key, &priv_key);

  /*
   * Extract r from the challenge.
   */
  len = exten_payload_size(ep);
  if (len == 0 || len > MAX_VALLEN)
    return (XEVNT_LEN);
  if ((r = BN_bin2bn((u_char *)ep->pkt, len, NULL)) == NULL) {
    msyslog(LOG_ERR, "crypto_bob3: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }

  /*
   * Bob rolls random k (0 < k < q), making sure it is not a
   * factor of q. He then computes y = r A^k and sends (y, gbar^k,
   * and ghat^k) to Alice.
   */
  bctx = BN_CTX_new(); k = BN_new(); u = BN_new();
  sdsa = DSA_new();
  sp = BN_new(); sq = BN_new(); sg = BN_new();
  while (1) {
    BN_rand(k, BN_num_bits(q), 0, 0);
    BN_mod(k, k, q, bctx);
    BN_gcd(u, k, q, bctx);
    if (BN_is_one(u))
      break;
  }
  BN_mod_exp(u, g, k, p, bctx); /* A^k r */
  BN_mod_mul(sp, u, r, p, bctx);
  BN_mod_exp(sq, priv_key, k, p, bctx); /* gbar */
  BN_mod_exp(sg, pub_key, k, p, bctx); /* ghat */
  DSA_set0_key(sdsa, BN_dup(pub_key), NULL);
  DSA_set0_pqg(sdsa, sp, sq, sg);
  BN_CTX_free(bctx); BN_free(k); BN_free(r); BN_free(u);
#ifdef DEBUG
  if (debug > 1)
    DSA_print_fp(stdout, sdsa, 0);
#endif

  /*
   * Encode the values in ASN.1 and sign. The filestamp is from
   * the local file.
   */
  memset(vp, 0, sizeof(struct value));
  tstamp = crypto_time();
  vp->tstamp = htonl(tstamp);
  vp->fstamp = htonl(mvkey_info->fstamp);
  len = i2d_DSAparams(sdsa, NULL);
  if (len == 0) {
    msyslog(LOG_ERR, "crypto_bob3: %s",
        ERR_error_string(ERR_get_error(), NULL));
    DSA_free(sdsa);
    return (XEVNT_ERR);
  }
  vp->vallen = htonl(len);
  ptr = emalloc(len);
  vp->ptr = ptr;
  i2d_DSAparams(sdsa, &ptr);
  DSA_free(sdsa);
  if (tstamp == 0)
    return (XEVNT_OK);

  vp->sig = emalloc(sign_siglen);
  ctx = digest_ctx;
  EVP_SignInit(ctx, sign_digest);
  EVP_SignUpdate(ctx, (u_char *)&vp->tstamp, 12);
  EVP_SignUpdate(ctx, vp->ptr, len);
  if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
    INSIST(len <= sign_siglen);
    vp->siglen = htonl(len);
  }
  return (XEVNT_OK);
}


/*
 * crypto_mv - verify Bob's response to Alice's challenge
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_ERR  protocol error
 * XEVNT_FSP  bad filestamp
 * XEVNT_ID bad or missing group key
 * XEVNT_PUB  bad or missing public key
 */
int
crypto_mv(
  struct exten *ep, /* extension pointer */
  struct peer *peer /* peer structure pointer */
  )
{
  const DSA *dsa;   /* MV parameters */
  DSA *sdsa;    /* DSA parameters */
  BN_CTX  *bctx;    /* BIGNUM context */
  BIGNUM  *k, *u, *v;
  u_int len;
  const u_char *ptr;
  int temp;
  const BIGNUM *p;
  const BIGNUM *pub_key, *priv_key;
  const BIGNUM *sp, *sq, *sg;

  /*
   * If the MV parameters are not valid or no challenge was sent,
   * something awful happened or we are being tormented.
   */
  if (peer->ident_pkey == NULL) {
    msyslog(LOG_NOTICE, "crypto_mv: scheme unavailable");
    return (XEVNT_ID);
  }
  if (ntohl(ep->fstamp) != peer->ident_pkey->fstamp) {
    msyslog(LOG_NOTICE, "crypto_mv: invalid filestamp %u",
        ntohl(ep->fstamp));
    return (XEVNT_FSP);
  }
  if ((dsa = EVP_PKEY_get0_DSA(peer->ident_pkey->pkey)) == NULL) {
    msyslog(LOG_NOTICE, "crypto_mv: defective key");
    return (XEVNT_PUB);
  }
  DSA_get0_pqg(dsa, &p, NULL, NULL);
  DSA_get0_key(dsa, &pub_key, &priv_key);
  if (peer->iffval == NULL) {
    msyslog(LOG_NOTICE, "crypto_mv: missing challenge");
    return (XEVNT_ID);
  }

  /*
   * Extract the y, gbar and ghat values from the response.
   */
  bctx = BN_CTX_new(); k = BN_new(); u = BN_new(); v = BN_new();
  len = ntohl(ep->vallen);
  ptr = (u_char *)ep->pkt;
  if ((sdsa = d2i_DSAparams(NULL, &ptr, len)) == NULL) {
    msyslog(LOG_ERR, "crypto_mv: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_ERR);
  }
  DSA_get0_pqg(sdsa, &sp, &sq, &sg);

  /*
   * Compute (gbar^xhat ghat^xbar) mod p.
   */
  BN_mod_exp(u, sq, pub_key, p, bctx);
  BN_mod_exp(v, sg, priv_key, p, bctx);
  BN_mod_mul(u, u, v, p, bctx);
  BN_mod_mul(u, u, sp, p, bctx);

  /*
   * The result should match r.
   */
  temp = BN_cmp(u, peer->iffval);
  BN_CTX_free(bctx); BN_free(k); BN_free(u); BN_free(v);
  BN_free(peer->iffval);
  peer->iffval = NULL;
  DSA_free(sdsa);
  if (temp == 0)
    return (XEVNT_OK);

  msyslog(LOG_NOTICE, "crypto_mv: identity not verified");
  return (XEVNT_ID);
}


/*
 ***********************************************************************
 *                       *
 * The following routines are used to manipulate certificates          *
 *                       *
 ***********************************************************************
 */
/*
 * cert_sign - sign x509 certificate equest and update value structure.
 *
 * The certificate request includes a copy of the host certificate,
 * which includes the version number, subject name and public key of the
 * host. The resulting certificate includes these values plus the
 * serial number, issuer name and valid interval of the server. The
 * valid interval extends from the current time to the same time one
 * year hence. This may extend the life of the signed certificate beyond
 * that of the signer certificate.
 *
 * It is convenient to use the NTP seconds of the current time as the
 * serial number. In the value structure the timestamp is the current
 * time and the filestamp is taken from the extension field. Note this
 * routine is called only when the client clock is synchronized to a
 * proventic source, so timestamp comparisons are valid.
 *
 * The host certificate is valid from the time it was generated for a
 * period of one year. A signed certificate is valid from the time of
 * signature for a period of one year, but only the host certificate (or
 * sign certificate if used) is actually used to encrypt and decrypt
 * signatures. The signature trail is built from the client via the
 * intermediate servers to the trusted server. Each signature on the
 * trail must be valid at the time of signature, but it could happen
 * that a signer certificate expire before the signed certificate, which
 * remains valid until its expiration. 
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_CRT  bad or missing certificate
 * XEVNT_PER  host certificate expired
 * XEVNT_PUB  bad or missing public key
 * XEVNT_VFY  certificate not verified
 */
static int
cert_sign(
  struct exten *ep, /* extension field pointer */
  struct value *vp  /* value pointer */
  )
{
  X509  *req;   /* X509 certificate request */
  X509  *cert;    /* X509 certificate */
  X509_EXTENSION *ext;  /* certificate extension */
  ASN1_INTEGER *serial; /* serial number */
  X509_NAME *subj;  /* distinguished (common) name */
  EVP_PKEY *pkey;   /* public key */
  EVP_MD_CTX *ctx;  /* message digest context */
  tstamp_t tstamp;  /* NTP timestamp */
  struct calendar tscal;
  u_int len;
  const u_char *cptr;
  u_char *ptr;
  int i, temp;

  /*
   * Decode ASN.1 objects and construct certificate structure.
   * Make sure the system clock is synchronized to a proventic
   * source.
   */
  tstamp = crypto_time();
  if (tstamp == 0)
    return (XEVNT_TSP);

  len = exten_payload_size(ep);
  if (len == 0 || len > MAX_VALLEN)
    return (XEVNT_LEN);
  cptr = (void *)ep->pkt;
  if ((req = d2i_X509(NULL, &cptr, len)) == NULL) {
    msyslog(LOG_ERR, "cert_sign: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (XEVNT_CRT);
  }
  /*
   * Extract public key and check for errors.
   */
  if ((pkey = X509_get_pubkey(req)) == NULL) {
    msyslog(LOG_ERR, "cert_sign: %s",
        ERR_error_string(ERR_get_error(), NULL));
    X509_free(req);
    return (XEVNT_PUB);
  }

  /*
   * Generate X509 certificate signed by this server. If this is a
   * trusted host, the issuer name is the group name; otherwise,
   * it is the host name. Also copy any extensions that might be
   * present.
   */
  cert = X509_new();
  X509_set_version(cert, X509_get_version(req));
  serial = ASN1_INTEGER_new();
  ASN1_INTEGER_set(serial, tstamp);
  X509_set_serialNumber(cert, serial);
  X509_gmtime_adj(X509_getm_notBefore(cert), 0L);
  X509_gmtime_adj(X509_getm_notAfter(cert), YEAR);
  subj = X509_get_issuer_name(cert);
  X509_NAME_add_entry_by_txt(subj, "commonName", MBSTRING_ASC,
      hostval.ptr, strlen((const char *)hostval.ptr), -1, 0);
  subj = X509_get_subject_name(req);
  X509_set_subject_name(cert, subj);
  X509_set_pubkey(cert, pkey);
  temp = X509_get_ext_count(req);
  for (i = 0; i < temp; i++) {
    ext = X509_get_ext(req, i);
    INSIST(X509_add_ext(cert, ext, -1));
  }
  X509_free(req);

  /*
   * Sign and verify the client certificate, but only if the host
   * certificate has not expired.
   */
  (void)ntpcal_ntp_to_date(&tscal, tstamp, NULL);
  if ((calcomp(&tscal, &(cert_host->first)) < 0)
  || (calcomp(&tscal, &(cert_host->last)) > 0)) {
    X509_free(cert);
    return (XEVNT_PER);
  }
  X509_sign(cert, sign_pkey, sign_digest);
  if (X509_verify(cert, sign_pkey) <= 0) {
    msyslog(LOG_ERR, "cert_sign: %s",
        ERR_error_string(ERR_get_error(), NULL));
    X509_free(cert);
    return (XEVNT_VFY);
  }
  len = i2d_X509(cert, NULL);

  /*
   * Build and sign the value structure. We have to sign it here,
   * since the response has to be returned right away. This is a
   * clogging hazard.
   */
  memset(vp, 0, sizeof(struct value));
  vp->tstamp = htonl(tstamp);
  vp->fstamp = ep->fstamp;
  vp->vallen = htonl(len);
  vp->ptr = emalloc(len);
  ptr = vp->ptr;
  i2d_X509(cert, (unsigned char **)(intptr_t)&ptr);
  vp->siglen = 0;
  if (tstamp != 0) {
    vp->sig = emalloc(sign_siglen);
    ctx = digest_ctx;
    EVP_SignInit(ctx, sign_digest);
    EVP_SignUpdate(ctx, (u_char *)vp, 12);
    EVP_SignUpdate(ctx, vp->ptr, len);
    if (EVP_SignFinal(ctx, vp->sig, &len, sign_pkey)) {
      INSIST(len <= sign_siglen);
      vp->siglen = htonl(len);
    }
  }
#ifdef DEBUG
  if (debug > 1)
    X509_print_fp(stdout, cert);
#endif
  X509_free(cert);
  return (XEVNT_OK);
}


/*
 * cert_install - install certificate in certificate cache
 *
 * This routine encodes an extension field into a certificate info/value
 * structure. It searches the certificate list for duplicates and
 * expunges whichever is older. Finally, it inserts this certificate
 * first on the list.
 *
 * Returns certificate info pointer if valid, NULL if not.
 */
struct cert_info *
cert_install(
  struct exten *ep, /* cert info/value */
  struct peer *peer /* peer structure */
  )
{
  struct cert_info *cp, *xp, **zp;

  /*
   * Parse and validate the signed certificate. If valid,
   * construct the info/value structure; otherwise, scamper home
   * empty handed.
   */
  if ((cp = cert_parse((u_char *)ep->pkt, (long)ntohl(ep->vallen),
      (tstamp_t)ntohl(ep->fstamp))) == NULL)
    return (NULL);

  /*
   * Scan certificate list looking for another certificate with
   * the same subject and issuer. If another is found with the
   * same or older filestamp, unlink it and return the goodies to
   * the heap. If another is found with a later filestamp, discard
   * the new one and leave the building with the old one.
   *
   * Make a note to study this issue again. An earlier certificate
   * with a long lifetime might be overtaken by a later
   * certificate with a short lifetime, thus invalidating the
   * earlier signature. However, we gotta find a way to leak old
   * stuff from the cache, so we do it anyway. 
   */
  zp = &cinfo;
  for (xp = cinfo; xp != NULL; xp = xp->link) {
    if (strcmp(cp->subject, xp->subject) == 0 &&
        strcmp(cp->issuer, xp->issuer) == 0) {
      if (ntohl(cp->cert.fstamp) <=
          ntohl(xp->cert.fstamp)) {
        cert_free(cp);
        cp = xp;
      } else {
        *zp = xp->link;
        cert_free(xp);
        xp = NULL;
      }
      break;
    }
    zp = &xp->link;
  }
  if (xp == NULL) {
    cp->link = cinfo;
    cinfo = cp;
  }
  cp->flags |= CERT_VALID;
  crypto_update();
  return (cp);
}


/*
 * cert_hike - verify the signature using the issuer public key
 *
 * Returns
 * XEVNT_OK success
 * XEVNT_CRT  bad or missing certificate
 * XEVNT_PER  host certificate expired
 * XEVNT_VFY  certificate not verified
 */
int
cert_hike(
  struct peer *peer,  /* peer structure pointer */
  struct cert_info *yp  /* issuer certificate */
  )
{
  struct cert_info *xp; /* subject certificate */
  X509  *cert;    /* X509 certificate */
  const u_char *ptr;

  /*
   * Save the issuer on the new certificate, but remember the old
   * one.
   */
  if (peer->issuer != NULL)
    free(peer->issuer);
  peer->issuer = estrdup(yp->issuer);
  xp = peer->xinfo;
  peer->xinfo = yp;

  /*
   * If subject Y matches issuer Y, then the certificate trail is
   * complete. If Y is not trusted, the server certificate has yet
   * been signed, so keep trying. Otherwise, save the group key
   * and light the valid bit. If the host certificate is trusted,
   * do not execute a sign exchange. If no identity scheme is in
   * use, light the identity and proventic bits.
   */
  if (strcmp(yp->subject, yp->issuer) == 0) {
    if (!(yp->flags & CERT_TRUST))
      return (XEVNT_OK);

    /*
     * If the server has an an identity scheme, fetch the
     * identity credentials. If not, the identity is
     * verified only by the trusted certificate. The next
     * signature will set the server proventic.
     */
    peer->crypto |= CRYPTO_FLAG_CERT;
    peer->grpkey = yp->grpkey;
    if (peer->ident == NULL || !(peer->crypto &
        CRYPTO_FLAG_MASK))
      peer->crypto |= CRYPTO_FLAG_VRFY;
  }

  /*
   * If X exists, verify signature X using public key Y.
   */
  if (xp == NULL)
    return (XEVNT_OK);

  ptr = (u_char *)xp->cert.ptr;
  cert = d2i_X509(NULL, &ptr, ntohl(xp->cert.vallen));
  if (cert == NULL) {
    xp->flags |= CERT_ERROR;
    return (XEVNT_CRT);
  }
  if (X509_verify(cert, yp->pkey) <= 0) {
    X509_free(cert);
    xp->flags |= CERT_ERROR;
    return (XEVNT_VFY);
  }
  X509_free(cert);

  /*
   * Signature X is valid only if it begins during the
   * lifetime of Y. 
   */
  if ((calcomp(&(xp->first), &(yp->first)) < 0)
  || (calcomp(&(xp->first), &(yp->last)) > 0)) {
    xp->flags |= CERT_ERROR;
    return (XEVNT_PER);
  }
  xp->flags |= CERT_SIGN;
  return (XEVNT_OK);
}


/*
 * cert_parse - parse x509 certificate and create info/value structures.
 *
 * The server certificate includes the version number, issuer name,
 * subject name, public key and valid date interval. If the issuer name
 * is the same as the subject name, the certificate is self signed and
 * valid only if the server is configured as trustable. If the names are
 * different, another issuer has signed the server certificate and
 * vouched for it. In this case the server certificate is valid if
 * verified by the issuer public key.
 *
 * Returns certificate info/value pointer if valid, NULL if not.
 */
struct cert_info *    /* certificate information structure */
cert_parse(
  const u_char *asn1cert, /* X509 certificate */
  long  len,    /* certificate length */
  tstamp_t fstamp   /* filestamp */
  )
{
  X509  *cert;    /* X509 certificate */
  struct cert_info *ret;  /* certificate info/value */
  BIO *bp;
  char  pathbuf[MAXFILENAME];
  const u_char *ptr;
  char  *pch;
  int cnt, i;
  struct calendar fscal;

  /*
   * Decode ASN.1 objects and construct certificate structure.
   */
  ptr = asn1cert;
  if ((cert = d2i_X509(NULL, &ptr, len)) == NULL) {
    msyslog(LOG_ERR, "cert_parse: %s",
        ERR_error_string(ERR_get_error(), NULL));
    return (NULL);
  }
#ifdef DEBUG
  if (debug > 1)
    X509_print_fp(stdout, cert);
#endif

  /*
   * Extract version, subject name and public key.
   */
  ret = emalloc_zero(sizeof(*ret));
  if ((ret->pkey = X509_get_pubkey(cert)) == NULL) {
    msyslog(LOG_ERR, "cert_parse: %s",
        ERR_error_string(ERR_get_error(), NULL));
    cert_free(ret);
    X509_free(cert);
    return (NULL);
  }
  ret->version = X509_get_version(cert);
  X509_NAME_oneline(X509_get_subject_name(cert), pathbuf,
      sizeof(pathbuf));
  pch = strstr(pathbuf, "CN=");
  if (NULL == pch) {
    msyslog(LOG_NOTICE, "cert_parse: invalid subject %s",
        pathbuf);
    cert_free(ret);
    X509_free(cert);
    return (NULL);
  }
  ret->subject = estrdup(pch + 3);

  /*
   * Extract remaining objects. Note that the NTP serial number is
   * the NTP seconds at the time of signing, but this might not be
   * the case for other authority. We don't bother to check the
   * objects at this time, since the real crunch can happen only
   * when the time is valid but not yet certificated.
   */
  ret->nid = X509_get_signature_nid(cert);
  ret->digest = (const EVP_MD *)EVP_get_digestbynid(ret->nid);
  ret->serial =
      (u_long)ASN1_INTEGER_get(X509_get_serialNumber(cert));
  X509_NAME_oneline(X509_get_issuer_name(cert), pathbuf,
      sizeof(pathbuf));
  if ((pch = strstr(pathbuf, "CN=")) == NULL) {
    msyslog(LOG_NOTICE, "cert_parse: invalid issuer %s",
        pathbuf);
    cert_free(ret);
    X509_free(cert);
    return (NULL);
  }
  ret->issuer = estrdup(pch + 3);
  asn_to_calendar(X509_get0_notBefore(cert), &(ret->first));
  asn_to_calendar(X509_get0_notAfter(cert), &(ret->last));

  /*
   * Extract extension fields. These are ad hoc ripoffs of
   * currently assigned functions and will certainly be changed
   * before prime time.
   */
  cnt = X509_get_ext_count(cert);
  for (i = 0; i < cnt; i++) {
    X509_EXTENSION *ext;
    ASN1_OBJECT *obj;
    int nid;
    ASN1_OCTET_STRING *data;

    ext = X509_get_ext(cert, i);
    obj = X509_EXTENSION_get_object(ext);
    nid = OBJ_obj2nid(obj);

    switch (nid) {

    /*
     * If a key_usage field is present, we decode whether
     * this is a trusted or private certificate. This is
     * dorky; all we want is to compare NIDs, but OpenSSL
     * insists on BIO text strings.
     */
    case NID_ext_key_usage:
      bp = BIO_new(BIO_s_mem());
      X509V3_EXT_print(bp, ext, 0, 0);
      BIO_gets(bp, pathbuf, sizeof(pathbuf));
      BIO_free(bp);
      if (strcmp(pathbuf, "Trust Root") == 0)
        ret->flags |= CERT_TRUST;
      else if (strcmp(pathbuf, "Private") == 0)
        ret->flags |= CERT_PRIV;
      DPRINTF(1, ("cert_parse: %s: %s\n",
            OBJ_nid2ln(nid), pathbuf));
      break;

    /*
     * If a NID_subject_key_identifier field is present, it
     * contains the GQ public key.
     */
    case NID_subject_key_identifier:
      data = X509_EXTENSION_get_data(ext);
      ret->grpkey = BN_bin2bn(&data->data[2],
          data->length - 2, NULL);
      /* fall through */
    default:
      DPRINTF(1, ("cert_parse: %s\n",
            OBJ_nid2ln(nid)));
      break;
    }
  }
  if (strcmp(ret->subject, ret->issuer) == 0) {

    /*
     * If certificate is self signed, verify signature.
     */
    if (X509_verify(cert, ret->pkey) <= 0) {
      msyslog(LOG_NOTICE,
          "cert_parse: signature not verified %s",
          ret->subject);
      cert_free(ret);
      X509_free(cert);
      return (NULL);
    }
  } else {

    /*
     * Check for a certificate loop.
     */
    if (strcmp((const char *)hostval.ptr, ret->issuer) == 0) {
      msyslog(LOG_NOTICE,
          "cert_parse: certificate trail loop %s",
          ret->subject);
      cert_free(ret);
      X509_free(cert);
      return (NULL);
    }
  }

  /*
   * Verify certificate valid times. Note that certificates cannot
   * be retroactive.
   */
  (void)ntpcal_ntp_to_date(&fscal, fstamp, NULL);
  if ((calcomp(&(ret->first), &(ret->last)) > 0)
  || (calcomp(&(ret->first), &fscal) < 0)) {
    msyslog(LOG_NOTICE,
        "cert_parse: invalid times %s first %u-%02u-%02uT%02u:%02u:%02u last %u-%02u-%02uT%02u:%02u:%02u fstamp %u-%02u-%02uT%02u:%02u:%02u",
        ret->subject,
        ret->first.year, ret->first.month, ret->first.monthday,
        ret->first.hour, ret->first.minute, ret->first.second,
        ret->last.year, ret->last.month, ret->last.monthday,
        ret->last.hour, ret->last.minute, ret->last.second,
        fscal.year, fscal.month, fscal.monthday,
        fscal.hour, fscal.minute, fscal.second);
    cert_free(ret);
    X509_free(cert);
    return (NULL);
  }

  /*
   * Build the value structure to sign and send later.
   */
  ret->cert.fstamp = htonl(fstamp);
  ret->cert.vallen = htonl(len);
  ret->cert.ptr = emalloc(len);
  memcpy(ret->cert.ptr, asn1cert, len);
  X509_free(cert);
  return (ret);
}


/*
 * cert_free - free certificate information structure
 */
void
cert_free(
  struct cert_info *cinf  /* certificate info/value structure */ 
  )
{
  if (cinf->pkey != NULL)
    EVP_PKEY_free(cinf->pkey);
  if (cinf->subject != NULL)
    free(cinf->subject);
  if (cinf->issuer != NULL)
    free(cinf->issuer);
  if (cinf->grpkey != NULL)
    BN_free(cinf->grpkey);
  value_free(&cinf->cert);
  free(cinf);
}


/*
 * crypto_key - load cryptographic parameters and keys
 *
 * This routine searches the key cache for matching name in the form
 * ntpkey_<key>_<name>, where <key> is one of host, sign, iff, gq, mv,
 * and <name> is the host/group name. If not found, it tries to load a
 * PEM-encoded file of the same name and extracts the filestamp from
 * the first line of the file name. It returns the key pointer if valid,
 * NULL if not.
 */
static struct pkey_info *
crypto_key(
  char  *cp,    /* file name */
  char  *passwd1, /* password */
  sockaddr_u *addr  /* IP address */
  )
{
  FILE  *str;   /* file handle */
  struct pkey_info *pkp;  /* generic key */
  EVP_PKEY *pkey = NULL; /* public/private key */
  tstamp_t fstamp;
  char  filename[MAXFILENAME]; /* name of key file */
  char  linkname[MAXFILENAME]; /* filestamp buffer) */
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  char  *ptr;

  /*
   * Search the key cache for matching key and name.
   */
  for (pkp = pkinfo; pkp != NULL; pkp = pkp->link) {
    if (strcmp(cp, pkp->name) == 0)
      return (pkp);
  }  

  /*
   * Open the key file. If the first character of the file name is
   * not '/', prepend the keys directory string. If something goes
   * wrong, abandon ship.
   */
  if (*cp == '/')
    strlcpy(filename, cp, sizeof(filename));
  else
    snprintf(filename, sizeof(filename), "%s/%s", keysdir,
        cp);
  str = fopen(filename, "r");
  if (str == NULL)
    return (NULL);

  /*
   * Read the filestamp, which is contained in the first line.
   */
  if ((ptr = fgets(linkname, sizeof(linkname), str)) == NULL) {
    msyslog(LOG_ERR, "crypto_key: empty file %s",
        filename);
    fclose(str);
    return (NULL);
  }
  if ((ptr = strrchr(ptr, '.')) == NULL) {
    msyslog(LOG_ERR, "crypto_key: no filestamp %s",
        filename);
    fclose(str);
    return (NULL);
  }
  if (sscanf(++ptr, "%u", &fstamp) != 1) {
    msyslog(LOG_ERR, "crypto_key: invalid filestamp %s",
        filename);
    fclose(str);
    return (NULL);
  }

  /*
   * Read and decrypt PEM-encoded private key. If it fails to
   * decrypt, game over.
   */
  pkey = PEM_read_PrivateKey(str, NULL, NULL, passwd1);
  fclose(str);
  if (pkey == NULL) {
    msyslog(LOG_ERR, "crypto_key: %s",
        ERR_error_string(ERR_get_error(), NULL));
    exit (-1);
  }

  /*
   * Make a new entry in the key cache.
   */
  pkp = emalloc(sizeof(struct pkey_info));
  pkp->link = pkinfo;
  pkinfo = pkp;
  pkp->pkey = pkey;
  pkp->name = estrdup(cp);
  pkp->fstamp = fstamp;

  /*
   * Leave tracks in the cryptostats.
   */
  if ((ptr = strrchr(linkname, '\n')) != NULL)
    *ptr = '\0'; 
  snprintf(statstr, sizeof(statstr), "%s mod %d", &linkname[2],
      EVP_PKEY_size(pkey) * 8);
  record_crypto_stats(addr, statstr);
  
  DPRINTF(1, ("crypto_key: %s\n", statstr));
#ifdef DEBUG
  if (debug > 1) {
    if (EVP_PKEY_base_id(pkey) == EVP_PKEY_DSA)
      DSA_print_fp(stdout, EVP_PKEY_get0_DSA(pkey), 0);
    else if (EVP_PKEY_base_id(pkey) == EVP_PKEY_RSA)
      RSA_print_fp(stdout, EVP_PKEY_get0_RSA(pkey), 0);
  }
#endif
  return (pkp);
}


/*
 ***********************************************************************
 *                       *
 * The following routines are used only at initialization time         *
 *                       *
 ***********************************************************************
 */
/*
 * crypto_cert - load certificate from file
 *
 * This routine loads an X.509 RSA or DSA certificate from a file and
 * constructs a info/cert value structure for this machine. The
 * structure includes a filestamp extracted from the file name. Later
 * the certificate can be sent to another machine on request.
 *
 * Returns certificate info/value pointer if valid, NULL if not.
 */
static struct cert_info * /* certificate information */
crypto_cert(
  char  *cp   /* file name */
  )
{
  struct cert_info *ret; /* certificate information */
  FILE  *str;   /* file handle */
  char  filename[MAXFILENAME]; /* name of certificate file */
  char  linkname[MAXFILENAME]; /* filestamp buffer */
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  tstamp_t fstamp;  /* filestamp */
  long  len;
  char  *ptr;
  char  *name, *header;
  u_char  *data;

  /*
   * Open the certificate file. If the first character of the file
   * name is not '/', prepend the keys directory string. If
   * something goes wrong, abandon ship.
   */
  if (*cp == '/')
    strlcpy(filename, cp, sizeof(filename));
  else
    snprintf(filename, sizeof(filename), "%s/%s", keysdir,
        cp);
  str = fopen(filename, "r");
  if (str == NULL)
    return (NULL);

  /*
   * Read the filestamp, which is contained in the first line.
   */
  if ((ptr = fgets(linkname, sizeof(linkname), str)) == NULL) {
    msyslog(LOG_ERR, "crypto_cert: empty file %s",
        filename);
    fclose(str);
    return (NULL);
  }
  if ((ptr = strrchr(ptr, '.')) == NULL) {
    msyslog(LOG_ERR, "crypto_cert: no filestamp %s",
        filename);
    fclose(str);
    return (NULL);
  }
  if (sscanf(++ptr, "%u", &fstamp) != 1) {
    msyslog(LOG_ERR, "crypto_cert: invalid filestamp %s",
        filename);
    fclose(str);
    return (NULL);
  }

  /*
   * Read PEM-encoded certificate and install.
   */
  if (!PEM_read(str, &name, &header, &data, &len)) {
    msyslog(LOG_ERR, "crypto_cert: %s",
        ERR_error_string(ERR_get_error(), NULL));
    fclose(str);
    return (NULL);
  }
  fclose(str);
  free(header);
  if (strcmp(name, "CERTIFICATE") != 0) {
    msyslog(LOG_NOTICE, "crypto_cert: wrong PEM type %s",
        name);
    free(name);
    free(data);
    return (NULL);
  }
  free(name);

  /*
   * Parse certificate and generate info/value structure. The
   * pointer and copy nonsense is due something broken in Solaris.
   */
  ret = cert_parse(data, len, fstamp);
  free(data);
  if (ret == NULL)
    return (NULL);

  if ((ptr = strrchr(linkname, '\n')) != NULL)
    *ptr = '\0'; 
  snprintf(statstr, sizeof(statstr), "%s 0x%x len %lu",
      &linkname[2], ret->flags, len);
  record_crypto_stats(NULL, statstr);
  DPRINTF(1, ("crypto_cert: %s\n", statstr));
  return (ret);
}


/*
 * crypto_setup - load keys, certificate and identity parameters
 *
 * This routine loads the public/private host key and certificate. If
 * available, it loads the public/private sign key, which defaults to
 * the host key. The host key must be RSA, but the sign key can be
 * either RSA or DSA. If a trusted certificate, it loads the identity
 * parameters. In either case, the public key on the certificate must
 * agree with the sign key.
 *
 * Required but missing files and inconsistent data and errors are
 * fatal. Allowing configuration to continue would be hazardous and
 * require really messy error checks.
 */
void
crypto_setup(void)
{
  struct pkey_info *pinfo; /* private/public key */
  char  filename[MAXFILENAME]; /* file name buffer */
  char  hostname[MAXFILENAME]; /* host name buffer */
  char  *randfile;
  char  statstr[NTP_MAXSTRLEN]; /* statistics for filegen */
  l_fp  seed;   /* crypto PRNG seed as NTP timestamp */
  u_int len;
  int bytes;
  u_char  *ptr;

  /*
   * Check for correct OpenSSL version and avoid initialization in
   * the case of multiple crypto commands.
   */
  if (crypto_flags & CRYPTO_FLAG_ENAB) {
    msyslog(LOG_NOTICE,
        "crypto_setup: spurious crypto command");
    return;
  }

  /*
   * Load required random seed file and seed the random number
   * generator. Be default, it is found as .rnd in the user home
   * directory. The root home directory may be / or /root,
   * depending on the system. Wiggle the contents a bit and write
   * it back so the sequence does not repeat when we next restart.
   */
  if (!RAND_status()) {
    if (rand_file == NULL) {
      RAND_file_name(filename, sizeof(filename));
      randfile = filename;
    } else if (*rand_file != '/') {
      snprintf(filename, sizeof(filename), "%s/%s",
          keysdir, rand_file);
      randfile = filename;
    } else
      randfile = rand_file;

    if ((bytes = RAND_load_file(randfile, -1)) == 0) {
      msyslog(LOG_ERR,
          "crypto_setup: random seed file %s missing",
          randfile);
      exit (-1);
    }
    get_systime(&seed);
    RAND_seed(&seed, sizeof(l_fp));
    RAND_write_file(randfile);
    DPRINTF(1, ("crypto_setup: OpenSSL version %lx random seed file %s bytes read %d\n",
          OpenSSL_version_num(), randfile, bytes));

  }

  /*
   * Initialize structures.
   */
  gethostname(hostname, sizeof(hostname));
  if (host_filename != NULL)
    strlcpy(hostname, host_filename, sizeof(hostname));
  if (passwd == NULL)
    passwd = estrdup(hostname);
  memset(&hostval, 0, sizeof(hostval));
  memset(&pubkey, 0, sizeof(pubkey));
  memset(&tai_leap, 0, sizeof(tai_leap));

  /*
   * Load required host key from file "ntpkey_host_<hostname>". If
   * no host key file is not found or has invalid password, life
   * as we know it ends. The host key also becomes the default
   * sign key. 
   */
  snprintf(filename, sizeof(filename), "ntpkey_host_%s", hostname);
  pinfo = crypto_key(filename, passwd, NULL);
  if (pinfo == NULL) {
    msyslog(LOG_ERR,
        "crypto_setup: host key file %s not found or corrupt",
        filename);
    exit (-1);
  }
  if (EVP_PKEY_base_id(pinfo->pkey) != EVP_PKEY_RSA) {
    msyslog(LOG_ERR,
        "crypto_setup: host key is not RSA key type");
    exit (-1);
  }
  host_pkey = pinfo->pkey;
  sign_pkey = host_pkey;
  hostval.fstamp = htonl(pinfo->fstamp);
  
  /*
   * Construct public key extension field for agreement scheme.
   */
  len = i2d_PublicKey(host_pkey, NULL);
  ptr = emalloc(len);
  pubkey.ptr = ptr;
  i2d_PublicKey(host_pkey, &ptr);
  pubkey.fstamp = hostval.fstamp;
  pubkey.vallen = htonl(len);

  /*
   * Load optional sign key from file "ntpkey_sign_<hostname>". If
   * available, it becomes the sign key.
   */
  snprintf(filename, sizeof(filename), "ntpkey_sign_%s", hostname);
  pinfo = crypto_key(filename, passwd, NULL);
  if (pinfo != NULL)
    sign_pkey = pinfo->pkey;

  /*
   * Load required certificate from file "ntpkey_cert_<hostname>".
   */
  snprintf(filename, sizeof(filename), "ntpkey_cert_%s", hostname);
  cinfo = crypto_cert(filename);
  if (cinfo == NULL) {
    msyslog(LOG_ERR,
        "crypto_setup: certificate file %s not found or corrupt",
        filename);
    exit (-1);
  }
  cert_host = cinfo;
  sign_digest = cinfo->digest;
  sign_siglen = EVP_PKEY_size(sign_pkey);
  if (cinfo->flags & CERT_PRIV)
    crypto_flags |= CRYPTO_FLAG_PRIV;

  /*
   * The certificate must be self-signed.
   */
  if (strcmp(cinfo->subject, cinfo->issuer) != 0) {
    msyslog(LOG_ERR,
        "crypto_setup: certificate %s is not self-signed",
        filename);
    exit (-1);
  }
  hostval.ptr = estrdup(cinfo->subject);
  hostval.vallen = htonl(strlen(cinfo->subject));
  sys_hostname = hostval.ptr;
  ptr = (u_char *)strchr(sys_hostname, '@');
  if (ptr != NULL)
    sys_groupname = estrdup((char *)++ptr);
  if (ident_filename != NULL)
    strlcpy(hostname, ident_filename, sizeof(hostname));

  /*
   * Load optional IFF parameters from file
   * "ntpkey_iffkey_<hostname>".
   */
  snprintf(filename, sizeof(filename), "ntpkey_iffkey_%s",
      hostname);
  iffkey_info = crypto_key(filename, passwd, NULL);
  if (iffkey_info != NULL)
    crypto_flags |= CRYPTO_FLAG_IFF;

  /*
   * Load optional GQ parameters from file
   * "ntpkey_gqkey_<hostname>".
   */
  snprintf(filename, sizeof(filename), "ntpkey_gqkey_%s",
      hostname);
  gqkey_info = crypto_key(filename, passwd, NULL);
  if (gqkey_info != NULL)
    crypto_flags |= CRYPTO_FLAG_GQ;

  /*
   * Load optional MV parameters from file
   * "ntpkey_mvkey_<hostname>".
   */
  snprintf(filename, sizeof(filename), "ntpkey_mvkey_%s",
      hostname);
  mvkey_info = crypto_key(filename, passwd, NULL);
  if (mvkey_info != NULL)
    crypto_flags |= CRYPTO_FLAG_MV;

  /*
   * We met the enemy and he is us. Now strike up the dance.
   */
  crypto_flags |= CRYPTO_FLAG_ENAB | (cinfo->nid << 16);
  snprintf(statstr, sizeof(statstr), "setup 0x%x host %s %s",
      crypto_flags, hostname, OBJ_nid2ln(cinfo->nid));
  record_crypto_stats(NULL, statstr);
  DPRINTF(1, ("crypto_setup: %s\n", statstr));
}


/*
 * crypto_config - configure data from the crypto command.
 */
void
crypto_config(
  int item,   /* configuration item */
  char  *cp   /* item name */
  )
{
  int nid;

  DPRINTF(1, ("crypto_config: item %d %s\n", item, cp));

  switch (item) {

  /*
   * Set host name (host).
   */
  case CRYPTO_CONF_PRIV:
    if (NULL != host_filename)
      free(host_filename);
    host_filename = estrdup(cp);
    break;

  /*
   * Set group name (ident).
   */
  case CRYPTO_CONF_IDENT:
    if (NULL != ident_filename)
      free(ident_filename);
    ident_filename = estrdup(cp);
    break;

  /*
   * Set private key password (pw).
   */
  case CRYPTO_CONF_PW:
    if (NULL != passwd)
      free(passwd);
    passwd = estrdup(cp);
    break;

  /*
   * Set random seed file name (randfile).
   */
  case CRYPTO_CONF_RAND:
    if (NULL != rand_file)
      free(rand_file);
    rand_file = estrdup(cp);
    break;

  /*
   * Set message digest NID.
   */
  case CRYPTO_CONF_NID:
    nid = OBJ_sn2nid(cp);
    if (nid == 0)
      msyslog(LOG_ERR,
          "crypto_config: invalid digest name %s", cp);
    else
      crypto_nid = nid;
    break;
  }
}

/*
 * Get the  payload size (internal value length) of an extension packet.
 * If the inner value size does not match the outer packet size (that
 * is, the value would end behind the frame given by the opcode/size
 * field) the function will effectively return UINT_MAX. If the frame is
 * too short to hold a variable-sized value, the return value is zero.
 */
static u_int
exten_payload_size(
  const struct exten * ep)
{
  typedef const u_char *BPTR;
  
  size_t extn_size;
  size_t data_size;
  size_t head_size;

  data_size = 0;
  if (NULL != ep) {
    head_size = (BPTR)(&ep->vallen + 1) - (BPTR)ep;
    extn_size = (uint16_t)(ntohl(ep->opcode) & 0x0000ffff);
    if (extn_size >= head_size) {
      data_size = (uint32_t)ntohl(ep->vallen);
      if (data_size > extn_size - head_size)
        data_size = ~(size_t)0u;
    }
  }
  return (u_int)data_size;
}
# else  /* !AUTOKEY follows */
NONEMPTY_TRANSLATION_UNIT
# endif /* !AUTOKEY */

Coverage Report

Created: 2026-02-26 06:20