/*

 * authreadkeys.c - routines to support the reading of the key file

 */

#include <config.h>

#include <stdio.h>

#include <ctype.h>

//#include "ntpd.h" /* Only for DPRINTF */

//#include "ntp_fp.h"

#include "ntp.h"

#include "ntp_syslog.h"

#include "ntp_stdlib.h"

#include "ntp_keyacc.h"

#ifdef OPENSSL

#include "openssl/objects.h"

#include "openssl/evp.h"

#endif  /* OPENSSL */

/* Forwards */

static char *nexttok (char **);

/*

 * nexttok - basic internal tokenizing routine

 */

static char *

nexttok(

  char  **str

  )

{

  register char *cp;

  char *starttok;

  cp = *str;

  /*

   * Space past white space

   */

  while (*cp == ' ' || *cp == '\t')

    cp++;

  /*

   * Save this and space to end of token

   */

  starttok = cp;

  while (*cp != '\0' && *cp != '\n' && *cp != ' '

         && *cp != '\t' && *cp != '#')

    cp++;

  /*

   * If token length is zero return an error, else set end of

   * token to zero and return start.

   */

  if (starttok == cp)

    return NULL;

  if (*cp == ' ' || *cp == '\t')

    *cp++ = '\0';

  else

    *cp = '\0';

  *str = cp;

  return starttok;

}

/* TALOS-CAN-0055: possibly DoS attack by setting the key file to the

 * log file. This is hard to prevent (it would need to check two files

 * to be the same on the inode level, which will not work so easily with

 * Windows or VMS) but we can avoid the self-amplification loop: We only

 * log the first 5 errors, silently ignore the next 10 errors, and give

 * up when when we have found more than 15 errors.

 *

 * This avoids the endless file iteration we will end up with otherwise,

 * and also avoids overflowing the log file.

 *

 * Nevertheless, once this happens, the keys are gone since this would

 * require a save/swap strategy that is not easy to apply due to the

 * data on global/static level.

 */

static const u_int nerr_loglimit = 5u;

static const u_int nerr_maxlimit = 15;

static void log_maybe(u_int*, const char*, ...) NTP_PRINTF(2, 3);

typedef struct keydata KeyDataT;

struct keydata {

  KeyDataT *next;   /* queue/stack link   */

  KeyAccT  *keyacclist; /* key access list    */

  keyid_t   keyid;  /* stored key ID    */

  u_short   keytype;  /* stored key type    */

  u_short   seclen; /* length of secret   */

  u_char    secbuf[1];  /* begin of secret (formal only)*/

};

static void

log_maybe(

  u_int      *pnerr,

  const char *fmt  ,

  ...)

{

  va_list ap;

  if ((NULL == pnerr) || (++(*pnerr) <= nerr_loglimit)) {

    va_start(ap, fmt);

    mvsyslog(LOG_ERR, fmt, ap);

    va_end(ap);

  }

}

static void

free_keydata(

  KeyDataT *node

  )

{

  KeyAccT *kap;

  if (node) {

    while (node->keyacclist) {

      kap = node->keyacclist;

      node->keyacclist = kap->next;

      free(kap);

    }

    /* purge secrets from memory before free()ing it */

    memset(node, 0, sizeof(*node) + node->seclen);

    free(node);

  }

}

/*

 * authreadkeys - (re)read keys from a file.

 */

int

authreadkeys(

  const char *file

  )

{

  FILE  *fp;

  char  *line;

  char  *token;

  keyid_t keyno;

  int keytype;

  char  buf[512];   /* lots of room for line */

  u_char  keystr[32];   /* Bug 2537 */

  size_t  len;

  size_t  j;

  u_int   nerr;

  KeyDataT *list = NULL;

  KeyDataT *next = NULL;

  /*

   * Open file.  Complain and return if it can't be opened.

   */

  fp = fopen(file, "r");

  if (fp == NULL) {

    msyslog(LOG_ERR, "authreadkeys: file '%s': %m",

        file);

    goto onerror;

  }

  INIT_SSL();

  /*

   * Now read lines from the file, looking for key entries. Put

   * the data into temporary store for later propagation to avoid

   * two-pass processing.

   */

  nerr = 0;

  while ((line = fgets(buf, sizeof buf, fp)) != NULL) {

    if (nerr > nerr_maxlimit)

      break;

    token = nexttok(&line);

    if (token == NULL)

      continue;

    /*

     * First is key number.  See if it is okay.

     */

    keyno = atoi(token);

    if (keyno < 1) {

      log_maybe(&nerr,

          "authreadkeys: cannot change key %s",

          token);

      continue;

    }

    if (keyno > NTP_MAXKEY) {

      log_maybe(&nerr,

          "authreadkeys: key %s > %d reserved for Autokey",

          token, NTP_MAXKEY);

      continue;

    }

    /*

     * Next is keytype. See if that is all right.

     */

    token = nexttok(&line);

    if (token == NULL) {

      log_maybe(&nerr,

          "authreadkeys: no key type for key %d",

          keyno);

      continue;

    }

    /* We want to silently ignore keys where we do not

     * support the requested digest type. OTOH, we want to

     * make sure the file is well-formed.  That means we

     * have to process the line completely and have to

     * finally throw away the result... This is a bit more

     * work, but it also results in better error detection.

     */ 

#ifdef OPENSSL

    /*

     * The key type is the NID used by the message digest 

     * algorithm. There are a number of inconsistencies in

     * the OpenSSL database. We attempt to discover them

     * here and prevent use of inconsistent data later.

     */

    keytype = keytype_from_text(token, NULL);

    if (keytype == 0) {

      log_maybe(NULL,

          "authreadkeys: invalid type for key %d",

          keyno);

#  ifdef ENABLE_CMAC

    } else if (NID_cmac != keytype &&

        EVP_get_digestbynid(keytype) == NULL) {

      log_maybe(NULL,

          "authreadkeys: no algorithm for key %d",

          keyno);

      keytype = 0;

#  endif /* ENABLE_CMAC */

    }

#else /* !OPENSSL follows */

    /*

     * The key type is unused, but is required to be 'M' or

     * 'm' for compatibility.

     */

    if (!(*token == 'M' || *token == 'm')) {

      log_maybe(NULL,

          "authreadkeys: invalid type for key %d",

          keyno);

      keytype = 0;

    } else {

      keytype = KEY_TYPE_MD5;

    }

#endif  /* !OPENSSL */

    /*

     * Finally, get key and insert it. If it is longer than 20

     * characters, it is a binary string encoded in hex;

     * otherwise, it is a text string of printable ASCII

     * characters.

     */

    token = nexttok(&line);

    if (token == NULL) {

      log_maybe(&nerr,

          "authreadkeys: no key for key %d", keyno);

      continue;

    }

    next = NULL;

    len = strlen(token);

    if (len <= 20) { /* Bug 2537 */

      next = emalloc(sizeof(KeyDataT) + len);

      next->keyacclist = NULL;

      next->keyid   = keyno;

      next->keytype = keytype;

      next->seclen  = len;

      memcpy(next->secbuf, token, len);

    } else {

      static const char hex[] = "0123456789abcdef";

      u_char  temp;

      char  *ptr;

      size_t  jlim;

      jlim = min(len, 2 * sizeof(keystr));

      for (j = 0; j < jlim; j++) {

        ptr = strchr(hex, tolower((unsigned char)token[j]));

        if (ptr == NULL)

          break; /* abort decoding */

        temp = (u_char)(ptr - hex);

        if (j & 1)

          keystr[j / 2] |= temp;

        else

          keystr[j / 2] = temp << 4;

      }

      if (j < jlim) {

        log_maybe(&nerr,

            "authreadkeys: invalid hex digit for key %d",

            keyno);

        continue;

      }

      len = jlim/2; /* hmmmm.... what about odd length?!? */

      next = emalloc(sizeof(KeyDataT) + len);

      next->keyacclist = NULL;

      next->keyid   = keyno;

      next->keytype = keytype;

      next->seclen  = len;

      memcpy(next->secbuf, keystr, len);

    }

    token = nexttok(&line);

    if (token != NULL) { /* A comma-separated IP access list */

      char *tp = token;

      while (tp) {

        char *i;

        char *snp;  /* subnet text pointer */

        unsigned int snbits;

        sockaddr_u addr;

        i = strchr(tp, (int)',');

        if (i) {

          *i = '\0';

        }

        snp = strchr(tp, (int)'/');

        if (snp) {

          char *sp;

          *snp++ = '\0';

          snbits = 0;

          sp = snp;

          while (*sp != '\0') {

            if (!isdigit((unsigned char)*sp))

                break;

            if (snbits > 1000)

                break; /* overflow */

            snbits = 10 * snbits + (*sp++ - '0');       /* ascii dependent */

          }

          if (*sp != '\0') {

            log_maybe(&nerr,

                "authreadkeys: Invalid character in subnet specification for <%s/%s> in key %d",

                sp, snp, keyno);

            goto nextip;

          }

        } else {

          snbits = UINT_MAX;

        }

        if (is_ip_address(tp, AF_UNSPEC, &addr)) {

          /* Make sure that snbits is valid for addr */

            if ((snbits < UINT_MAX) &&

          ( (IS_IPV4(&addr) && snbits > 32) ||

            (IS_IPV6(&addr) && snbits > 128))) {

            log_maybe(NULL,

                "authreadkeys: excessive subnet mask <%s/%s> for key %d",

                tp, snp, keyno);

            }

            next->keyacclist = keyacc_new_push(

          next->keyacclist, &addr, snbits);

        } else {

          log_maybe(&nerr,

              "authreadkeys: invalid IP address <%s> for key %d",

              tp, keyno);

        }

      nextip:

        if (i) {

          tp = i + 1;

        } else {

          tp = 0;

        }

      }

    }

    /* check if this has to be weeded out... */

    if (0 == keytype) {

      free_keydata(next);

      next = NULL;

      continue;

    }

    INSIST(NULL != next);

    next->next = list;

    list = next;

  }

  fclose(fp);

  if (nerr > 0) {

    const char * why = "";

    if (nerr > nerr_maxlimit)

      why = " (emergency break)";

    msyslog(LOG_ERR,

      "authreadkeys: rejecting file '%s' after %u error(s)%s",

      file, nerr, why);

    goto onerror;

  }

  /* first remove old file-based keys */

  auth_delkeys();

  /* insert the new key material */

  while (NULL != (next = list)) {

    list = next->next;

    MD5auth_setkey(next->keyid, next->keytype,

             next->secbuf, next->seclen, next->keyacclist);

    next->keyacclist = NULL; /* consumed by MD5auth_setkey */

    free_keydata(next);

  }

  return (1);

  onerror:

  /* Mop up temporary storage before bailing out. */

  while (NULL != (next = list)) {

    list = next->next;

    free_keydata(next);

  }

  return (0);

}