/* $OpenBSD: ssh_api.c,v 1.28 2024/01/09 21:39:14 djm Exp $ */

/*

 * Copyright (c) 2012 Markus Friedl.  All rights reserved.

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include "includes.h"

#include <sys/types.h>

#include <stdio.h>

#include <stdlib.h>

#include "ssh_api.h"

#include "compat.h"

#include "log.h"

#include "authfile.h"

#include "sshkey.h"

#include "misc.h"

#include "ssh2.h"

#include "version.h"

#include "myproposal.h"

#include "ssherr.h"

#include "sshbuf.h"

#include "openbsd-compat/openssl-compat.h"

#include <string.h>

int _ssh_exchange_banner(struct ssh *);

int _ssh_send_banner(struct ssh *, struct sshbuf *);

int _ssh_read_banner(struct ssh *, struct sshbuf *);

int _ssh_order_hostkeyalgs(struct ssh *);

int _ssh_verify_host_key(struct sshkey *, struct ssh *);

struct sshkey *_ssh_host_public_key(int, int, struct ssh *);

struct sshkey *_ssh_host_private_key(int, int, struct ssh *);

int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *,

    u_char **, size_t *, const u_char *, size_t, const char *);

/*

 * stubs for the server side implementation of kex.

 * disable privsep so our stubs will never be called.

 */

int use_privsep = 0;

int mm_sshkey_sign(struct sshkey *, u_char **, u_int *,

    const u_char *, u_int, const char *, const char *, const char *, u_int);

#ifdef WITH_OPENSSL

DH  *mm_choose_dh(int, int, int);

#endif

int

mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,

    const u_char *data, u_int datalen, const char *alg,

    const char *sk_provider, const char *sk_pin, u_int compat)

{

  return (-1);

}

#ifdef WITH_OPENSSL

DH *

mm_choose_dh(int min, int nbits, int max)

{

  return (NULL);

}

#endif

/* API */

int

ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)

{

  char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };

  char *populated[PROPOSAL_MAX];

  struct ssh *ssh;

  char **proposal;

  static int called;

  int r;

  if (!called) {

    seed_rng();

    called = 1;

  }

  if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if (is_server)

    ssh_packet_set_server(ssh);

  /* Initialize key exchange */

  proposal = kex_params ? kex_params->proposal : myproposal;

  kex_proposal_populate_entries(ssh, populated,

      proposal[PROPOSAL_KEX_ALGS],

      proposal[PROPOSAL_ENC_ALGS_CTOS],

      proposal[PROPOSAL_MAC_ALGS_CTOS],

      proposal[PROPOSAL_COMP_ALGS_CTOS],

      proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]);

  r = kex_ready(ssh, populated);

  kex_proposal_free_entries(populated);

  if (r != 0) {

    ssh_free(ssh);

    return r;

  }

  ssh->kex->server = is_server;

  if (is_server) {

#ifdef WITH_OPENSSL

    ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;

    ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;

    ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;

    ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;

    ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;

    ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;

    ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;

# ifdef OPENSSL_HAS_ECC

    ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;

# endif

#endif /* WITH_OPENSSL */

    ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;

    ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;

    ssh->kex->load_host_public_key=&_ssh_host_public_key;

    ssh->kex->load_host_private_key=&_ssh_host_private_key;

    ssh->kex->sign=&_ssh_host_key_sign;

  } else {

#ifdef WITH_OPENSSL

    ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;

    ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;

    ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;

    ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;

    ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;

    ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;

    ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;

# ifdef OPENSSL_HAS_ECC

    ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;

# endif

#endif /* WITH_OPENSSL */

    ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;

    ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;

    ssh->kex->verify_host_key =&_ssh_verify_host_key;

  }

  *sshp = ssh;

  return 0;

}

void

ssh_free(struct ssh *ssh)

{

  struct key_entry *k;

  if (ssh == NULL)

    return;

  /*

   * we've only created the public keys variants in case we

   * are a acting as a server.

   */

  while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {

    TAILQ_REMOVE(&ssh->public_keys, k, next);

    if (ssh->kex && ssh->kex->server)

      sshkey_free(k->key);

    free(k);

  }

  while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {

    TAILQ_REMOVE(&ssh->private_keys, k, next);

    free(k);

  }

  ssh_packet_close(ssh);

  free(ssh);

}

void

ssh_set_app_data(struct ssh *ssh, void *app_data)

{

  ssh->app_data = app_data;

}

void *

ssh_get_app_data(struct ssh *ssh)

{

  return ssh->app_data;

}

/* Returns < 0 on error, 0 otherwise */

int

ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)

{

  struct sshkey *pubkey = NULL;

  struct key_entry *k = NULL, *k_prv = NULL;

  int r;

  if (ssh->kex->server) {

    if ((r = sshkey_from_private(key, &pubkey)) != 0)

      return r;

    if ((k = malloc(sizeof(*k))) == NULL ||

        (k_prv = malloc(sizeof(*k_prv))) == NULL) {

      free(k);

      sshkey_free(pubkey);

      return SSH_ERR_ALLOC_FAIL;

    }

    k_prv->key = key;

    TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);

    /* add the public key, too */

    k->key = pubkey;

    TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);

    r = 0;

  } else {

    if ((k = malloc(sizeof(*k))) == NULL)

      return SSH_ERR_ALLOC_FAIL;

    k->key = key;

    TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);

    r = 0;

  }

  return r;

}

int

ssh_set_verify_host_key_callback(struct ssh *ssh,

    int (*cb)(struct sshkey *, struct ssh *))

{

  if (cb == NULL || ssh->kex == NULL)

    return SSH_ERR_INVALID_ARGUMENT;

  ssh->kex->verify_host_key = cb;

  return 0;

}

int

ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)

{

  return sshbuf_put(ssh_packet_get_input(ssh), data, len);

}

int

ssh_packet_next(struct ssh *ssh, u_char *typep)

{

  int r;

  u_int32_t seqnr;

  u_char type;

  /*

   * Try to read a packet. Return SSH_MSG_NONE if no packet or not

   * enough data.

   */

  *typep = SSH_MSG_NONE;

  if (sshbuf_len(ssh->kex->client_version) == 0 ||

      sshbuf_len(ssh->kex->server_version) == 0)

    return _ssh_exchange_banner(ssh);

  /*

   * If we enough data and a dispatch function then

   * call the function and get the next packet.

   * Otherwise return the packet type to the caller so it

   * can decide how to go on.

   *

   * We will only call the dispatch function for:

   *     20-29    Algorithm negotiation

   *     30-49    Key exchange method specific (numbers can be reused for

   *              different authentication methods)

   */

  for (;;) {

    if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)

      return r;

    if (type > 0 && type < DISPATCH_MAX &&

        type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&

        ssh->dispatch[type] != NULL) {

      if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)

        return r;

    } else {

      *typep = type;

      return 0;

    }

  }

}

const u_char *

ssh_packet_payload(struct ssh *ssh, size_t *lenp)

{

  return sshpkt_ptr(ssh, lenp);

}

int

ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)

{

  int r;

  if ((r = sshpkt_start(ssh, type)) != 0 ||

      (r = sshpkt_put(ssh, data, len)) != 0 ||

      (r = sshpkt_send(ssh)) != 0)

    return r;

  return 0;

}

const u_char *

ssh_output_ptr(struct ssh *ssh, size_t *len)

{

  struct sshbuf *output = ssh_packet_get_output(ssh);

  *len = sshbuf_len(output);

  return sshbuf_ptr(output);

}

int

ssh_output_consume(struct ssh *ssh, size_t len)

{

  return sshbuf_consume(ssh_packet_get_output(ssh), len);

}

int

ssh_output_space(struct ssh *ssh, size_t len)

{

  return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));

}

int

ssh_input_space(struct ssh *ssh, size_t len)

{

  return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));

}

/* Read other side's version identification. */

int

_ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)

{

  struct sshbuf *input = ssh_packet_get_input(ssh);

  const char *mismatch = "Protocol mismatch.\r\n";

  const u_char *s = sshbuf_ptr(input);

  u_char c;

  char *cp = NULL, *remote_version = NULL;

  int r = 0, remote_major, remote_minor, expect_nl;

  size_t n, j;

  for (j = n = 0;;) {

    sshbuf_reset(banner);

    expect_nl = 0;

    for (;;) {

      if (j >= sshbuf_len(input))

        return 0; /* insufficient data in input buf */

      c = s[j++];

      if (c == '\r') {

        expect_nl = 1;

        continue;

      }

      if (c == '\n')

        break;

      if (expect_nl)

        goto bad;

      if ((r = sshbuf_put_u8(banner, c)) != 0)

        return r;

      if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)

        goto bad;

    }

    if (sshbuf_len(banner) >= 4 &&

        memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)

      break;

    debug_f("%.*s", (int)sshbuf_len(banner),

        sshbuf_ptr(banner));

    /* Accept lines before banner only on client */

    if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {

  bad:

      if ((r = sshbuf_put(ssh_packet_get_output(ssh),

          mismatch, strlen(mismatch))) != 0)

        return r;

      return SSH_ERR_NO_PROTOCOL_VERSION;

    }

  }

  if ((r = sshbuf_consume(input, j)) != 0)

    return r;

  /* XXX remote version must be the same size as banner for sscanf */

  if ((cp = sshbuf_dup_string(banner)) == NULL ||

      (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  /*

   * Check that the versions match.  In future this might accept

   * several versions and set appropriate flags to handle them.

   */

  if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",

      &remote_major, &remote_minor, remote_version) != 3) {

    r = SSH_ERR_INVALID_FORMAT;

    goto out;

  }

  debug("Remote protocol version %d.%d, remote software version %.100s",

      remote_major, remote_minor, remote_version);

  compat_banner(ssh, remote_version);

  if  (remote_major == 1 && remote_minor == 99) {

    remote_major = 2;

    remote_minor = 0;

  }

  if (remote_major != 2)

    r = SSH_ERR_PROTOCOL_MISMATCH;

  debug("Remote version string %.100s", cp);

 out:

  free(cp);

  free(remote_version);

  return r;

}

/* Send our own protocol version identification. */

int

_ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)

{

  char *cp;

  int r;

  if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_RELEASE)) != 0)

    return r;

  if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)

    return r;

  /* Remove trailing \r\n */

  if ((r = sshbuf_consume_end(banner, 2)) != 0)

    return r;

  if ((cp = sshbuf_dup_string(banner)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  debug("Local version string %.100s", cp);

  free(cp);

  return 0;

}

int

_ssh_exchange_banner(struct ssh *ssh)

{

  struct kex *kex = ssh->kex;

  int r;

  /*

   * if _ssh_read_banner() cannot parse a full version string

   * it will return NULL and we end up calling it again.

   */

  r = 0;

  if (kex->server) {

    if (sshbuf_len(ssh->kex->server_version) == 0)

      r = _ssh_send_banner(ssh, ssh->kex->server_version);

    if (r == 0 &&

        sshbuf_len(ssh->kex->server_version) != 0 &&

        sshbuf_len(ssh->kex->client_version) == 0)

      r = _ssh_read_banner(ssh, ssh->kex->client_version);

  } else {

    if (sshbuf_len(ssh->kex->server_version) == 0)

      r = _ssh_read_banner(ssh, ssh->kex->server_version);

    if (r == 0 &&

        sshbuf_len(ssh->kex->server_version) != 0 &&

        sshbuf_len(ssh->kex->client_version) == 0)

      r = _ssh_send_banner(ssh, ssh->kex->client_version);

  }

  if (r != 0)

    return r;

  /* start initial kex as soon as we have exchanged the banners */

  if (sshbuf_len(ssh->kex->server_version) != 0 &&

      sshbuf_len(ssh->kex->client_version) != 0) {

    if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||

        (r = kex_send_kexinit(ssh)) != 0)

      return r;

  }

  return 0;

}

struct sshkey *

_ssh_host_public_key(int type, int nid, struct ssh *ssh)

{

  struct key_entry *k;

  debug3_f("need %d", type);

  TAILQ_FOREACH(k, &ssh->public_keys, next) {

    debug3_f("check %s", sshkey_type(k->key));

    if (k->key->type == type &&

        (type != KEY_ECDSA || k->key->ecdsa_nid == nid))

      return (k->key);

  }

  return (NULL);

}

struct sshkey *

_ssh_host_private_key(int type, int nid, struct ssh *ssh)

{

  struct key_entry *k;

  debug3_f("need %d", type);

  TAILQ_FOREACH(k, &ssh->private_keys, next) {

    debug3_f("check %s", sshkey_type(k->key));

    if (k->key->type == type &&

        (type != KEY_ECDSA || k->key->ecdsa_nid == nid))

      return (k->key);

  }

  return (NULL);

}

int

_ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)

{

  struct key_entry *k;

  debug3_f("need %s", sshkey_type(hostkey));

  TAILQ_FOREACH(k, &ssh->public_keys, next) {

    debug3_f("check %s", sshkey_type(k->key));

    if (sshkey_equal_public(hostkey, k->key))

      return (0); /* ok */

  }

  return (-1); /* failed */

}

/* offer hostkey algorithms in kexinit depending on registered keys */

int

_ssh_order_hostkeyalgs(struct ssh *ssh)

{

  struct key_entry *k;

  char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;

  char **proposal;

  size_t maxlen;

  int ktype, r;

  /* XXX we de-serialize ssh->kex->my, modify it, and change it */

  if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)

    return r;

  orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];

  if ((oavail = avail = strdup(orig)) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  maxlen = strlen(avail) + 1;

  if ((replace = calloc(1, maxlen)) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  *replace = '\0';

  while ((alg = strsep(&avail, ",")) && *alg != '\0') {

    if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)

      continue;

    TAILQ_FOREACH(k, &ssh->public_keys, next) {

      if (k->key->type == ktype ||

          (sshkey_is_cert(k->key) && k->key->type ==

          sshkey_type_plain(ktype))) {

        if (*replace != '\0')

          strlcat(replace, ",", maxlen);

        strlcat(replace, alg, maxlen);

        break;

      }

    }

  }

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

    debug2_f("orig/%d    %s", ssh->kex->server, orig);

    debug2_f("replace/%d %s", ssh->kex->server, replace);

    free(orig);

    proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;

    replace = NULL; /* owned by proposal */

    r = kex_prop2buf(ssh->kex->my, proposal);

  }

 out:

  free(oavail);

  free(replace);

  kex_prop_free(proposal);

  return r;

}

int

_ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,

    struct sshkey *pubkey, u_char **signature, size_t *slen,

    const u_char *data, size_t dlen, const char *alg)

{

  return sshkey_sign(privkey, signature, slen, data, dlen,

      alg, NULL, NULL, ssh->compat);

}