예제 #1
0
int sftp_auth_hostbased(struct ssh2_packet *pkt, cmd_rec *pass_cmd,
    const char *orig_user, const char *user, const char *service,
    unsigned char **buf, uint32_t *buflen, int *send_userauth_fail) {
  struct passwd *pw;
  char *hostkey_algo, *host_fqdn, *host_user, *host_user_utf8;
  const char *fp = NULL;
  unsigned char *hostkey_data, *signature_data;
  unsigned char *buf2, *ptr2;
  const unsigned char *id;
  uint32_t buflen2, bufsz2, hostkey_datalen, id_len, signature_len;
  enum sftp_key_type_e pubkey_type;

  if (pr_cmd_dispatch_phase(pass_cmd, PRE_CMD, 0) < 0) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "authentication request for user '%s' blocked by '%s' handler",
      orig_user, (char *) pass_cmd->argv[0]);

    pr_cmd_dispatch_phase(pass_cmd, POST_CMD_ERR, 0);
    pr_cmd_dispatch_phase(pass_cmd, LOG_CMD_ERR, 0);

    *send_userauth_fail = TRUE;
    errno = EPERM;
    return 0;
  }

  hostkey_algo = sftp_msg_read_string(pkt->pool, buf, buflen);
  if (hostkey_algo == NULL) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "missing required host key algorithm, rejecting request");

    *send_userauth_fail = TRUE;
    errno = EINVAL;
    return 0;
  }

  hostkey_datalen = sftp_msg_read_int(pkt->pool, buf, buflen);
  hostkey_data = sftp_msg_read_data(pkt->pool, buf, buflen, hostkey_datalen);

  host_fqdn = sftp_msg_read_string(pkt->pool, buf, buflen);

  host_user_utf8 = sftp_msg_read_string(pkt->pool, buf, buflen);
  host_user = sftp_utf8_decode_str(pkt->pool, host_user_utf8);

  signature_len = sftp_msg_read_int(pkt->pool, buf, buflen);
  signature_data = sftp_msg_read_data(pkt->pool, buf, buflen, signature_len);

  pr_trace_msg(trace_channel, 9,
    "client sent '%s' host key, FQDN %s, and remote user '%s'",
    hostkey_algo, host_fqdn, host_user);

  if (strncmp(hostkey_algo, "ssh-rsa", 8) == 0) {
    pubkey_type = SFTP_KEY_RSA;

  } else if (strncmp(hostkey_algo, "ssh-dss", 8) == 0) {
    pubkey_type = SFTP_KEY_DSA;

#ifdef PR_USE_OPENSSL_ECC
  } else if (strncmp(hostkey_algo, "ecdsa-sha2-nistp256", 20) == 0) {
    pubkey_type = SFTP_KEY_ECDSA_256;

  } else if (strncmp(hostkey_algo, "ecdsa-sha2-nistp256", 20) == 0) {
    pubkey_type = SFTP_KEY_ECDSA_384;

  } else if (strncmp(hostkey_algo, "ecdsa-sha2-nistp256", 20) == 0) {
    pubkey_type = SFTP_KEY_ECDSA_521;
#endif /* PR_USE_OPENSSL_ECC */

  /* XXX Need to support X509v3 certs here */

  } else {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "unsupported host key algorithm '%s' requested, rejecting request",
      hostkey_algo);

    *send_userauth_fail = TRUE;
    errno = EINVAL;
    return 0;
  }

  if (sftp_keys_verify_pubkey_type(pkt->pool, hostkey_data, hostkey_datalen,
      pubkey_type) != TRUE) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "unable to verify that given host key matches given '%s' algorithm",
      hostkey_algo);

    *send_userauth_fail = TRUE;
    errno = EINVAL;
    return 0;
  }

#ifdef OPENSSL_FIPS
  if (FIPS_mode()) {
    fp = sftp_keys_get_fingerprint(pkt->pool, hostkey_data, hostkey_datalen,
      SFTP_KEYS_FP_DIGEST_SHA1);
    if (fp != NULL) {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "public key SHA1 fingerprint: %s", fp);

    } else {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "error obtaining public key SHA1 fingerprint: %s", strerror(errno));
    }

  } else {
#endif /* OPENSSL_FIPS */
    fp = sftp_keys_get_fingerprint(pkt->pool, hostkey_data, hostkey_datalen,
      SFTP_KEYS_FP_DIGEST_MD5);
    if (fp != NULL) {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "public key MD5 fingerprint: %s", fp);

    } else {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "error obtaining public key MD5 fingerprint: %s", strerror(errno));
    }
#ifdef OPENSSL_FIPS
  }
#endif /* OPENSSL_FIPS */

  pw = pr_auth_getpwnam(pkt->pool, user);
  if (pw == NULL) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "no account for user '%s' found", user);

    pr_log_auth(PR_LOG_NOTICE,
      "USER %s: no such user found from %s [%s] to %s:%d", user,
      session.c->remote_name, pr_netaddr_get_ipstr(session.c->remote_addr),
      pr_netaddr_get_ipstr(session.c->local_addr), session.c->local_port);

    *send_userauth_fail = TRUE;
    errno = ENOENT;
    return 0;
  }

  /* XXX Should we check the given FQDN here against the client's actual
   * DNS name and/or IP address?  Or leave that up to the keystore's
   * verify_host_key() function?
   */

  if (sftp_blacklist_reject_key(pkt->pool, hostkey_data, hostkey_datalen)) {
    *send_userauth_fail = TRUE;
    errno = EACCES;
    return 0;
  }

  /* The client signed the request as well; we need to authenticate the
   * host with the given key now.  If that succeeds, we use the signature to
   * verify the request.  And if that succeeds, then we're done authenticating.
   */

  if (sftp_keystore_verify_host_key(pkt->pool, user, host_fqdn, host_user,
      hostkey_data, hostkey_datalen) < 0) {
    *send_userauth_fail = TRUE;
    errno = EACCES;
    return 0;
  }

  /* Make sure the signature matches as well. */

  id_len = sftp_session_get_id(&id);

  /* XXX Is this buffer large enough?  Too large? */
  bufsz2 = buflen2 = 2048;
  ptr2 = buf2 = sftp_msg_getbuf(pkt->pool, bufsz2);

  sftp_msg_write_data(&buf2, &buflen2, id, id_len, TRUE);
  sftp_msg_write_byte(&buf2, &buflen2, SFTP_SSH2_MSG_USER_AUTH_REQUEST);
  sftp_msg_write_string(&buf2, &buflen2, orig_user);

  if (sftp_interop_supports_feature(SFTP_SSH2_FEAT_SERVICE_IN_HOST_SIG)) {
    sftp_msg_write_string(&buf2, &buflen2, service);

  } else {
    sftp_msg_write_string(&buf2, &buflen2, "ssh-userauth");
  }

  sftp_msg_write_string(&buf2, &buflen2, "hostbased");
  sftp_msg_write_string(&buf2, &buflen2, hostkey_algo);
  sftp_msg_write_data(&buf2, &buflen2, hostkey_data, hostkey_datalen, TRUE);
  sftp_msg_write_string(&buf2, &buflen2, host_fqdn);
  sftp_msg_write_string(&buf2, &buflen2, host_user_utf8);

  if (sftp_keys_verify_signed_data(pkt->pool, hostkey_algo, hostkey_data,
      hostkey_datalen, signature_data, signature_len, (unsigned char *) ptr2,
      (bufsz2 - buflen2)) < 0) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "failed to verify '%s' signature on hostbased auth request for "
      "user '%s', host %s", hostkey_algo, orig_user, host_fqdn);
    *send_userauth_fail = TRUE;
    return 0;
  }

  /* Make sure the user is authorized to login.  Normally this is checked
   * as part of the password verification process, but in the case of
   * hostbased authentication, there is no password to verify.
   */

  if (pr_auth_authorize(pkt->pool, user) != PR_AUTH_OK) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "authentication for user '%s' failed: User not authorized", user);
    pr_log_auth(PR_LOG_NOTICE, "USER %s (Login failed): User not authorized "
      "for login", user);
    *send_userauth_fail = TRUE;
    errno = EACCES;
    return 0;
  }

  return 1;
}
예제 #2
0
int sftp_auth_publickey(struct ssh2_packet *pkt, cmd_rec *pass_cmd,
    const char *orig_user, const char *user, const char *service, char **buf,
    uint32_t *buflen, int *send_userauth_fail) {
  int have_signature, pubkey_type;
  char *pubkey_algo = NULL, *pubkey_data;
  const char *fp = NULL;
  uint32_t pubkey_len;
  struct passwd *pw;

  if (pr_cmd_dispatch_phase(pass_cmd, PRE_CMD, 0) < 0) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "authentication request for user '%s' blocked by '%s' handler",
      orig_user, pass_cmd->argv[0]);

    pr_cmd_dispatch_phase(pass_cmd, POST_CMD_ERR, 0);
    pr_cmd_dispatch_phase(pass_cmd, LOG_CMD_ERR, 0);

    *send_userauth_fail = TRUE;
    errno = EPERM;
    return 0;
  }

  have_signature = sftp_msg_read_bool(pkt->pool, buf, buflen);

  if (sftp_interop_supports_feature(SFTP_SSH2_FEAT_HAVE_PUBKEY_ALGO)) {
    pubkey_algo = sftp_msg_read_string(pkt->pool, buf, buflen);
  }
  pubkey_len = sftp_msg_read_int(pkt->pool, buf, buflen);
  pubkey_data = sftp_msg_read_data(pkt->pool, buf, buflen, pubkey_len);

  if (pubkey_algo == NULL) {
    /* The client did not send the string identifying the public key algorithm.
     * Thus we need to extract the algorithm string from the public key data.
     */
    pubkey_algo = sftp_msg_read_string(pkt->pool, &pubkey_data, &pubkey_len);
  }

  pr_trace_msg(trace_channel, 9, "client sent '%s' public key %s",
    pubkey_algo, have_signature ? "with signature" : "without signature");

  if (strncmp(pubkey_algo, "ssh-rsa", 8) == 0) {
    pubkey_type = EVP_PKEY_RSA;

  } else if (strncmp(pubkey_algo, "ssh-dss", 8) == 0) {
    pubkey_type = EVP_PKEY_DSA;

  /* XXX This is where we would add support for X509 public keys, e.g.:
   *
   *  x509v3-ssh-dss
   *  x509v3-ssh-rsa
   *  x509v3-sign (older)
   *
   */

  } else {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "unsupported public key algorithm '%s' requested, rejecting request",
      pubkey_algo);

    *send_userauth_fail = TRUE;
    errno = EINVAL;
    return 0;
  }

  if (sftp_keys_verify_pubkey_type(pkt->pool, pubkey_data, pubkey_len,
      pubkey_type) != TRUE) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "unable to verify that given public key matches given '%s' algorithm",
      pubkey_algo);

    *send_userauth_fail = TRUE;
    errno = EINVAL;
    return 0;
  }

#ifdef OPENSSL_FIPS
  if (FIPS_mode()) {
    fp = sftp_keys_get_fingerprint(pkt->pool, pubkey_data, pubkey_len,
      SFTP_KEYS_FP_DIGEST_SHA1);
    if (fp != NULL) {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "public key SHA1 fingerprint: %s", fp);

    } else {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "error obtaining public key SHA1 fingerprint: %s", strerror(errno));
    }

  } else {
#endif /* OPENSSL_FIPS */
    fp = sftp_keys_get_fingerprint(pkt->pool, pubkey_data, pubkey_len,
      SFTP_KEYS_FP_DIGEST_MD5);
    if (fp != NULL) {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "public key MD5 fingerprint: %s", fp);

    } else {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "error obtaining public key MD5 fingerprint: %s", strerror(errno));
    }
#ifdef OPENSSL_FIPS
  }
#endif /* OPENSSL_FIPS */

  pw = pr_auth_getpwnam(pkt->pool, user);
  if (pw == NULL) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "no account for user '%s' found", user);

    pr_log_auth(PR_LOG_NOTICE,
      "USER %s: no such user found from %s [%s] to %s:%d", user,
      session.c->remote_name, pr_netaddr_get_ipstr(session.c->remote_addr),
      pr_netaddr_get_ipstr(session.c->local_addr), session.c->local_port);

    *send_userauth_fail = TRUE;
    errno = ENOENT;
    return 0;
  }

  if (!have_signature) {
    /* We don't perform the actual authentication just yet; we need to
     * let the client know that the pubkey algorithms are acceptable.
     */
    if (send_pubkey_ok(pubkey_algo, pubkey_data, pubkey_len) < 0) {
      return -1;
    }

    return 0;

  } else {
    const unsigned char *id;
    char *buf2, *ptr2, *signature_data;
    uint32_t buflen2, bufsz2, id_len, signature_len;

    /* XXX This should become a more generic "is this key data
     * usable/acceptable?" check (and take the pubkey_type parameter), so that
     * that is where we would check the validity/usability of an X509v3 cert
     * (if a cert), or if the key is on the blacklist (if a key).
     */

    if (sftp_blacklist_reject_key(pkt->pool, pubkey_data, pubkey_len)) {
      *send_userauth_fail = TRUE;
      errno = EPERM;
      return 0;
    }

    signature_len = sftp_msg_read_int(pkt->pool, buf, buflen);
    signature_data = sftp_msg_read_data(pkt->pool, buf, buflen, signature_len);

    /* The client signed the request as well; we need to authenticate the
     * user with the given pubkey now.  If that succeeds, we use the
     * signature to verify the request.  And if that succeeds, then we're
     * done authenticating.
     */

    /* XXX Need to pass the pubkey_type here as well, so that the
     * verification routines can handle different databases of keys/certs.
     * 
     * For X509v3 certs, we will want a way to enforce/restrict which
     * user names can be used with the provided cert.  Perhaps a database
     * mapping cert fingerprints to user names/UIDs?  Configurable callback
     * check (HOOK?), for modules to enforce.
     */

    if (sftp_keystore_verify_user_key(pkt->pool, user, pubkey_data,
        pubkey_len) < 0) {
      *send_userauth_fail = TRUE;
      return 0;
    }

    /* Make sure the signature matches as well. */

    id_len = sftp_session_get_id(&id);

    /* Make sure to allocate a buffer large enough to hold the publickey
     * signature and data we want to send back.
     */
    bufsz2 = buflen2 = pubkey_len + 1024;
    ptr2 = buf2 = sftp_msg_getbuf(pkt->pool, bufsz2);

    sftp_msg_write_data(&buf2, &buflen2, (char *) id, id_len, TRUE);
    sftp_msg_write_byte(&buf2, &buflen2, SFTP_SSH2_MSG_USER_AUTH_REQUEST);
    sftp_msg_write_string(&buf2, &buflen2, orig_user);

    if (sftp_interop_supports_feature(SFTP_SSH2_FEAT_SERVICE_IN_PUBKEY_SIG)) {
      sftp_msg_write_string(&buf2, &buflen2, service);

    } else {
      sftp_msg_write_string(&buf2, &buflen2, "ssh-userauth");
    }

    if (sftp_interop_supports_feature(SFTP_SSH2_FEAT_HAVE_PUBKEY_ALGO)) {
      sftp_msg_write_string(&buf2, &buflen2, "publickey");
      sftp_msg_write_bool(&buf2, &buflen2, TRUE);
      sftp_msg_write_string(&buf2, &buflen2, pubkey_algo);

    } else {
      sftp_msg_write_bool(&buf2, &buflen2, TRUE);
    }

    sftp_msg_write_data(&buf2, &buflen2, pubkey_data, pubkey_len, TRUE);

    if (sftp_keys_verify_signed_data(pkt->pool, pubkey_algo, pubkey_data,
        pubkey_len, signature_data, signature_len, (unsigned char *) ptr2,
        (bufsz2 - buflen2)) < 0) {
      (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
        "failed to verify '%s' signature on public key auth request for "
        "user '%s'", pubkey_algo, orig_user);
      *send_userauth_fail = TRUE;
      return 0;
    }
  }

  /* Make sure the user is authorized to login.  Normally this is checked
   * as part of the password verification process, but in the case of
   * publickey authentication, there is no password to verify.
   */

  if (pr_auth_authorize(pkt->pool, user) != PR_AUTH_OK) {
    (void) pr_log_writefile(sftp_logfd, MOD_SFTP_VERSION,
      "authentication for user '%s' failed: User not authorized", user);
    pr_log_auth(PR_LOG_NOTICE, "USER %s (Login failed): User not authorized "
      "for login", user);
    *send_userauth_fail = TRUE;
    errno = EACCES;
    return 0;
  }

  return 1;
}