int guac_common_ssh_verify_host_key()

in src/common-ssh/key.c [173:254]

• 57 lines of code
• 11 McCabe index (conditional complexity)

int guac_common_ssh_verify_host_key(LIBSSH2_SESSION* session, guac_client* client,
        const char* host_key, const char* hostname, int port, const char* remote_hostkey,
        const size_t remote_hostkey_len) {

    LIBSSH2_KNOWNHOSTS* ssh_known_hosts = libssh2_knownhost_init(session);
    int known_hosts = 0;

    /* Add host key provided from settings */
    if (host_key && strcmp(host_key, "") != 0) {

        known_hosts = libssh2_knownhost_readline(ssh_known_hosts, host_key, strlen(host_key),
                LIBSSH2_KNOWNHOST_FILE_OPENSSH);

        /* readline function returns 0 on success, so we increment to indicate a valid entry */
        if (known_hosts == 0)
            known_hosts++;

    }

    /* Otherwise, we look for a ssh_known_hosts file within GUACAMOLE_HOME and read that in. */
    else {

        const char *guac_known_hosts = "/etc/guacamole/ssh_known_hosts";
        if (access(guac_known_hosts, F_OK) != -1)
            known_hosts = libssh2_knownhost_readfile(ssh_known_hosts, guac_known_hosts, LIBSSH2_KNOWNHOST_FILE_OPENSSH);

    }

    /* If there's an error provided, abort connection and return that. */
    if (known_hosts < 0) {

        char* errmsg;
        int errval = libssh2_session_last_error(session, &errmsg, NULL, 0);
        guac_client_log(client, GUAC_LOG_ERROR,
            "Error %d trying to load SSH host keys: %s", errval, errmsg);

        libssh2_knownhost_free(ssh_known_hosts);
        return known_hosts;

    }

    /* No host keys were loaded, so we bail out checking and continue the connection. */
    else if (known_hosts == 0) {
        guac_client_log(client, GUAC_LOG_WARNING,
            "No known host keys provided, host identity will not be verified.");
        libssh2_knownhost_free(ssh_known_hosts);
        return known_hosts;
    }

    /* Check remote host key against known hosts */
    int kh_check = libssh2_knownhost_checkp(ssh_known_hosts, hostname, port,
                                            remote_hostkey, remote_hostkey_len,
                                            LIBSSH2_KNOWNHOST_TYPE_PLAIN|
                                            LIBSSH2_KNOWNHOST_KEYENC_RAW,
                                            NULL);

    /* Deal with the return of the host key check */
    switch (kh_check) {
        case LIBSSH2_KNOWNHOST_CHECK_MATCH:
            guac_client_log(client, GUAC_LOG_DEBUG,
                "Host key match found for %s", hostname);
            break;
        case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
            guac_client_log(client, GUAC_LOG_ERROR,
                "Host key not found for %s.", hostname);
            break;
        case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
            guac_client_log(client, GUAC_LOG_ERROR,
                "Host key does not match known hosts entry for %s", hostname);
            break;
        case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
        default:
            guac_client_log(client, GUAC_LOG_ERROR,
                "Host %s could not be checked against known hosts.",
                hostname);
    }

    /* Return the check value */
    libssh2_knownhost_free(ssh_known_hosts);
    return kh_check;

}