[WIP] Add SSH tunneling settings for Telnet.

src/protocols/telnet/Makefile.am

@@ -50,11 +50,13 @@ noinst_HEADERS = \
 
 libguac_client_telnet_la_CFLAGS = \
     -Werror -Wall -Iinclude       \
+    @COMMON_SSH_INCLUDE@          \
     @LIBGUAC_INCLUDE@             \
     @TERMINAL_INCLUDE@
 
 libguac_client_telnet_la_LIBADD = \
     @COMMON_LTLIB@                \
+    @COMMON_SSH_LTLIB@            \
     @LIBGUAC_LTLIB@               \
     @TERMINAL_LTLIB@
 

src/protocols/telnet/client.c

@@ -24,6 +24,13 @@
 #include "telnet.h"
 #include "user.h"
 
+#ifdef ENABLE_COMMON_SSH
+#include "common-ssh/sftp.h"
+#include "common-ssh/ssh.h"
+#include "common-ssh/tunnel.h"
+#include "common-ssh/user.h"
+#endif
+
 #include <langinfo.h>
 #include <locale.h>
 #include <pthread.h>
@@ -54,6 +61,10 @@ int guac_client_init(guac_client* client) {
     client->free_handler = guac_telnet_client_free_handler;
     client->leave_handler = guac_telnet_user_leave_handler;
 
+#ifdef ENABLE_COMMON_SSH
+    guac_common_ssh_init(client);
+#endif
+
     /* Register handlers for argument values that may be sent after the handshake */
     guac_argv_register(GUAC_TELNET_ARGV_COLOR_SCHEME, guac_telnet_argv_callback, NULL, GUAC_ARGV_OPTION_ECHO);
     guac_argv_register(GUAC_TELNET_ARGV_FONT_NAME, guac_telnet_argv_callback, NULL, GUAC_ARGV_OPTION_ECHO);
@@ -93,6 +104,25 @@ int guac_telnet_client_free_handler(guac_client* client) {
         telnet_free(telnet_client->telnet);
     }
 
+#ifdef ENABLE_COMMON_SSH
+    /* Free SFTP filesystem, if loaded */
+    if (telnet_client->sftp_filesystem)
+        guac_common_ssh_destroy_sftp_filesystem(telnet_client->sftp_filesystem);
+
+    /* Free SFTP session */
+    if (telnet_client->sftp_session)
+        guac_common_ssh_destroy_session(telnet_client->sftp_session);
+
+    /* Free SFTP user */
+    if (telnet_client->sftp_user)
+        guac_common_ssh_destroy_user(telnet_client->sftp_user);
+
+    if (telnet_client->ssh_tunnel)
+        guac_common_ssh_tunnel_cleanup(telnet_client->ssh_tunnel);
+
+    guac_common_ssh_uninit();
+#endif
+
     /* Free settings */
     if (telnet_client->settings != NULL)
         guac_telnet_settings_free(telnet_client->settings);

src/protocols/telnet/settings.c

@@ -21,6 +21,7 @@
 
 #include "argv.h"
 #include "common/defaults.h"
+#include "common-ssh/ssh-constants.h"
 #include "settings.h"
 #include "terminal/terminal.h"
 
@@ -66,6 +67,32 @@ const char* GUAC_TELNET_CLIENT_ARGS[] = {
     "wol-broadcast-addr",
     "wol-udp-port",
     "wol-wait-time",
+
+#ifdef ENABLE_COMMON_SSH
+    "enable-sftp",
+    "sftp-hostname",
+    "sftp-host-key",
+    "sftp-port",
+    "sftp-username",
+    "sftp-password",
+    "sftp-private-key",
+    "sftp-passphrase",
+    "sftp-directory",
+    "sftp-root-directory",
+    "sftp-server-alive-interval",
+    "sftp-disable-download",
+    "sftp-disable-upload",
+    "ssh-tunnel",
+    "ssh-tunnel-host",
+    "ssh-tunnel-port",
+    "ssh-tunnel-host-key",
+    "ssh-tunnel-username",
+    "ssh-tunnel-password",
+    "ssh-tunnel-private-key",
+    "ssh-tunnel-passphrase",
+    "ssh-tunnel-alive-interval",
+#endif
+
     NULL
 };
 
@@ -272,6 +299,137 @@ enum TELNET_ARGS_IDX {
      */
     IDX_WOL_WAIT_TIME,
 
+#ifdef ENABLE_COMMON_SSH
+    /**
+     * "true" if SFTP should be enabled for the connection, "false" or
+     * blank otherwise.
+     */
+    IDX_ENABLE_SFTP,
+
+    /**
+     * The hostname of the SSH server to connect to for SFTP. If blank, the
+     * hostname of the telnet server will be used.
+     */
+    IDX_SFTP_HOSTNAME,
+
+    /**
+     * The public SSH host key to identify the SFTP server.
+     */
+    IDX_SFTP_HOST_KEY,
+
+    /**
+     * The port of the SSH server to connect to for SFTP. If blank, the default
+     * SSH port of "22" will be used.
+     */
+    IDX_SFTP_PORT,
+
+    /**
+     * The username to provide when authenticating with the SSH server for
+     * SFTP.
+     */
+    IDX_SFTP_USERNAME,
+
+    /**
+     * The password to provide when authenticating with the SSH server for
+     * SFTP (if not using a private key).
+     */
+    IDX_SFTP_PASSWORD,
+
+    /**
+     * The base64-encoded private key to use when authenticating with the SSH
+     * server for SFTP (if not using a password).
+     */
+    IDX_SFTP_PRIVATE_KEY,
+
+    /**
+     * The passphrase to use to decrypt the provided base64-encoded private
+     * key.
+     */
+    IDX_SFTP_PASSPHRASE,
+
+    /**
+     * The default location for file uploads within the SSH server. This will
+     * apply only to uploads which do not use the filesystem guac_object (where
+     * the destination directory is otherwise ambiguous).
+     */
+    IDX_SFTP_DIRECTORY,
+
+    /**
+     * The path of the directory within the SSH server to expose as a
+     * filesystem guac_object. If omitted, "/" will be used by default.
+     */
+    IDX_SFTP_ROOT_DIRECTORY,
+
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically incremented to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    IDX_SFTP_SERVER_ALIVE_INTERVAL,
+    
+    /**
+     * If set to "true", file downloads over SFTP will be blocked.  If set to
+     * "false" or not set, file downloads will be allowed.
+     */
+    IDX_SFTP_DISABLE_DOWNLOAD,
+    
+    /**
+     * If set to "true", file uploads over SFTP will be blocked.  If set to
+     * "false" or not set, file uploads will be allowed.
+     */
+    IDX_SFTP_DISABLE_UPLOAD,
+
+    /**
+     * True if SSH tunneling should be enabled. If false or not set, SSH
+     * tunneling will not be used.
+     */
+    IDX_SSH_TUNNEL,
+
+    /**
+     * The hostname or IP address of the SSH server to use for tunneling.
+     */
+    IDX_SSH_TUNNEL_HOST,
+
+    /**
+     * The TCP port of the SSH server to use for tunneling.
+     */
+    IDX_SSH_TUNNEL_PORT,
+
+    /**
+     * If host key checking should be done, the public key of the SSH host
+     * to be used for tunneling.
+     */
+    IDX_SSH_TUNNEL_HOST_KEY,
+
+    /**
+     * The username for authenticating to the SSH hsot for tunneling.
+     */
+    IDX_SSH_TUNNEL_USERNAME,
+
+    /**
+     * The password to use to authenticate to the SSH host for tunneling.
+     */
+    IDX_SSH_TUNNEL_PASSWORD,
+
+    /**
+     * The private key to use to authenticate to the SSH host for tunneling,
+     * as an alternative to password-based authentication.
+     */
+    IDX_SSH_TUNNEL_PRIVATE_KEY,
+
+    /**
+     * The passphrase to use to decrypt the private key.
+     */
+    IDX_SSH_TUNNEL_PASSPHRASE,
+
+    /**
+     * The interval at which keepalive packets should be sent to the SSH
+     * tunneling server, or zero if keepalive should be disabled.
+     */
+    IDX_SSH_TUNNEL_ALIVE_INTERVAL,
+#endif
+
     TELNET_ARGS_COUNT
 };
 
@@ -530,6 +688,118 @@ guac_telnet_settings* guac_telnet_parse_args(guac_user* user,
         
     }
 
+#ifdef ENABLE_COMMON_SSH
+    /* SFTP enable/disable */
+    settings->enable_sftp =
+        guac_user_parse_args_boolean(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                IDX_ENABLE_SFTP, false);
+
+    /* If SFTP is not enabled, no reason to parse the rest. */
+    if (settings->enable_sftp) {
+        /* Hostname for SFTP connection */
+        settings->sftp_hostname =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_HOSTNAME, settings->hostname);
+
+        /* The public SSH host key. */
+        settings->sftp_host_key =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_HOST_KEY, NULL);
+
+        /* Port for SFTP connection */
+        settings->sftp_port =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_PORT, "22");
+
+        /* Username for SSH/SFTP authentication */
+        settings->sftp_username =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_USERNAME, "");
+
+        /* Password for SFTP (if not using private key) */
+        settings->sftp_password =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_PASSWORD, "");
+
+        /* Private key for SFTP (if not using password) */
+        settings->sftp_private_key =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_PRIVATE_KEY, NULL);
+
+        /* Passphrase for decrypting the SFTP private key (if applicable */
+        settings->sftp_passphrase =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_PASSPHRASE, "");
+
+        /* Default upload directory */
+        settings->sftp_directory =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_DIRECTORY, NULL);
+
+        /* SFTP root directory */
+        settings->sftp_root_directory =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_ROOT_DIRECTORY, GUAC_COMMON_SSH_SFTP_DEFAULT_ROOT);
+
+        /* Default keepalive value */
+        settings->sftp_server_alive_interval =
+            guac_user_parse_args_int(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_SERVER_ALIVE_INTERVAL,
+                    GUAC_COMMON_SSH_DEFAULT_ALIVE_INTERVAL);
+
+        settings->sftp_disable_download =
+            guac_user_parse_args_boolean(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_DISABLE_DOWNLOAD, false);
+
+        settings->sftp_disable_upload =
+            guac_user_parse_args_boolean(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SFTP_DISABLE_UPLOAD, false);
+    }
+
+    /* Parse SSH tunneling. */
+    settings->ssh_tunnel =
+        guac_user_parse_args_boolean(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                IDX_SSH_TUNNEL, false);
+    
+    /* Only parse remaining tunneling settings if it has been enabled. */
+    if (settings->ssh_tunnel) {
+
+        settings->ssh_tunnel_host =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_HOST, NULL);
+
+        settings->ssh_tunnel_port =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PORT, GUAC_COMMON_SSH_DEFAULT_PORT);
+
+        settings->ssh_tunnel_host_key =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_HOST_KEY, NULL);
+
+        settings->ssh_tunnel_username =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_USERNAME, NULL);
+
+        settings->ssh_tunnel_password =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PASSWORD, NULL);
+
+        settings->ssh_tunnel_private_key =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PRIVATE_KEY, NULL);
+
+        settings->ssh_tunnel_passphrase =
+            guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PASSPHRASE, NULL);
+
+        settings->ssh_tunnel_alive_interval =
+            guac_user_parse_args_int(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_ALIVE_INTERVAL,
+                    GUAC_COMMON_SSH_DEFAULT_ALIVE_INTERVAL);
+
+    }
+#endif
+
     /* Parsing was successful */
     return settings;
 
@@ -570,6 +840,23 @@ void guac_telnet_settings_free(guac_telnet_settings* settings) {
     free(settings->wol_mac_addr);
     free(settings->wol_broadcast_addr);
 
+    /* Free SSH and SFTP settings. */
+    free(settings->sftp_hostname);
+    free(settings->sftp_host_key);
+    free(settings->sftp_username);
+    free(settings->sftp_password);
+    free(settings->sftp_private_key);
+    free(settings->sftp_passphrase);
+    free(settings->sftp_directory);
+    free(settings->sftp_root_directory);
+    free(settings->ssh_tunnel_host);
+    free(settings->ssh_tunnel_host_key);
+    free(settings->ssh_tunnel_port);
+    free(settings->ssh_tunnel_username);
+    free(settings->ssh_tunnel_password);
+    free(settings->ssh_tunnel_private_key);
+    free(settings->ssh_tunnel_passphrase);
+
     /* Free overall structure */
     free(settings);
 

src/protocols/telnet/settings.h

@@ -269,6 +269,150 @@ typedef struct guac_telnet_settings {
      */
     int wol_wait_time;
 
+#ifdef ENABLE_COMMON_SSH
+    /**
+     * Whether SFTP should be enabled for the VNC connection.
+     */
+    bool enable_sftp;
+
+    /**
+     * The hostname of the SSH server to connect to for SFTP.
+     */
+    char* sftp_hostname;
+
+    /**
+     * The public SSH host key.
+     */
+    char* sftp_host_key;
+
+    /**
+     * The port of the SSH server to connect to for SFTP.
+     */
+    char* sftp_port;
+
+    /**
+     * The username to provide when authenticating with the SSH server for
+     * SFTP.
+     */
+    char* sftp_username;
+
+    /**
+     * The password to provide when authenticating with the SSH server for
+     * SFTP (if not using a private key).
+     */
+    char* sftp_password;
+
+    /**
+     * The base64-encoded private key to use when authenticating with the SSH
+     * server for SFTP (if not using a password).
+     */
+    char* sftp_private_key;
+
+    /**
+     * The passphrase to use to decrypt the provided base64-encoded private
+     * key.
+     */
+    char* sftp_passphrase;
+
+    /**
+     * The default location for file uploads within the SSH server. This will
+     * apply only to uploads which do not use the filesystem guac_object (where
+     * the destination directory is otherwise ambiguous).
+     */
+    char* sftp_directory;
+
+    /**
+     * The path of the directory within the SSH server to expose as a
+     * filesystem guac_object.
+     */
+    char* sftp_root_directory;
+
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically increased to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    int sftp_server_alive_interval;
+    
+    /**
+     * Whether file downloads over SFTP should be blocked.  If set to "true",
+     * the local client will not be able to download files from the SFTP server.
+     * If set to "false" or not set, file downloads will be allowed.
+     */
+    bool sftp_disable_download;
+    
+    /**
+     * Whether file uploads over SFTP should be blocked.  If set to "true", the
+     * local client will not be able to upload files to the SFTP server.  If set
+     * to "false" or not set, file uploads will be allowed.
+     */
+    bool sftp_disable_upload;
+
+    /**
+     * Whether to enable tunneling of this connection through the specified
+     * SSH server. If set to "true", guacd will attempt to connect to the SSH
+     * server and tunnel all of the traffic through the SSH connection. If
+     * set to "false" or not set, SSH tunneling will not be used.
+     */
+    bool ssh_tunnel;
+
+    /**
+     * The hostname or address of the host through which traffic should be
+     * tunneled over SSH. If tunneling is enabled, this is required, or the
+     * connection will be aborted.
+     */
+    char* ssh_tunnel_host;
+
+    /**
+     * The port on which to connect to the SSH server to tunnel traffic, if
+     * SSH tunneling is enabled. If not specified, this will default to 22, the
+     * normal SSH port.
+     */
+    char* ssh_tunnel_port;
+
+    /**
+     * The public key of the SSH host through which this connection will be
+     * tunneled. If unset, no host key checking will be done and the connection
+     * will be attempted regardless of the identity of the remote host.
+     */
+    char* ssh_tunnel_host_key;
+
+    /**
+     * The username to use when connecting to the SSH host to tunnel traffic.
+     * This is required if SSH tunneling is enabled.
+     */
+    char* ssh_tunnel_username;
+
+    /**
+     * The password to use when connecting to the SSH host to tunnel traffic,
+     * if password authentication is used.
+     */
+    char* ssh_tunnel_password;
+
+    /**
+     * The private key to use to authenticate to the SSH server to tunnel traffic,
+     * if key-based authentication is used.
+     */
+    char* ssh_tunnel_private_key;
+
+    /**
+     * The passphrase of the private key to use to decrypt the private key when
+     * using key-based authentication, if the key is encrypted.
+     */
+    char* ssh_tunnel_passphrase;
+
+    /**
+     * The interval at which keepalive messages will be sent to the SSH server
+     * over which the connection is being tunneled. The default is 0, meaning
+     * that keepalive messages will be disabled. The minimum value is 2 to avoid
+     * busy loop scenarios, and a value of 1 is automatically increased to 2 by
+     * the underlying libssh2 implementation.
+     */
+    int ssh_tunnel_alive_interval;
+
+#endif
+
 } guac_telnet_settings;
 
 /**

src/protocols/telnet/telnet.c

@@ -26,6 +26,7 @@
 #include <guacamole/client.h>
 #include <guacamole/protocol.h>
 #include <guacamole/recording.h>
+#include <guacamole/string.h>
 #include <guacamole/timestamp.h>
 #include <guacamole/wol.h>
 #include <libtelnet.h>
@@ -40,6 +41,7 @@
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/time.h>
+#include <sys/un.h>
 #include <unistd.h>
 
 /**
@@ -392,6 +394,120 @@ static telnet_t* __guac_telnet_create_session(guac_client* client) {
     guac_telnet_client* telnet_client = (guac_telnet_client*) client->data;
     guac_telnet_settings* settings = telnet_client->settings;
 
+    if (settings->ssh_tunnel) {
+
+        /* Allocate memory for the SSH tunnel data. */
+        telnet_client->ssh_tunnel = malloc(sizeof(guac_ssh_tunnel));
+
+        guac_client_log(client, GUAC_LOG_DEBUG,
+                "SSH tunneling is enabled, connecting via SSH.");
+
+        /* Associate the guac_client object with the tunnel. */
+        telnet_client->ssh_tunnel->client = client;
+
+        /* Abort if tunnel username is missing */
+        if (settings->ssh_tunnel_username == NULL) {
+            guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                    "An SSH tunnel-specific username is required if "
+                    "SSH tunneling is enabled.");
+            return NULL;
+        }
+
+        telnet_client->ssh_tunnel->user =
+            guac_common_ssh_create_user(settings->ssh_tunnel_username);
+
+        /* Import SSH tunnel private key, if given */
+        if (settings->ssh_tunnel_private_key != NULL) {
+
+            guac_client_log(client, GUAC_LOG_DEBUG,
+                    "Authenticating SSH tunnel with private key.");
+
+            /* Abort if SSH tunnel private key cannot be read */
+            if (guac_common_ssh_user_import_key(telnet_client->ssh_tunnel->user,
+                        settings->ssh_tunnel_private_key,
+                        settings->ssh_tunnel_passphrase)) {
+                guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                        "SSH tunnel private key unreadable.");
+                return NULL;
+            }
+
+        }
+
+        /* Otherwise, use specified SSH tunnel password */
+        else {
+
+            guac_client_log(client, GUAC_LOG_DEBUG,
+                    "Authenticating SSH tunnel with password.");
+
+            guac_common_ssh_user_set_password(telnet_client->ssh_tunnel->user,
+                    settings->ssh_tunnel_password);
+
+        }
+
+        /* Attempt SSH tunnel connection */
+        telnet_client->ssh_tunnel->session =
+            guac_common_ssh_create_session(client, settings->ssh_tunnel_host,
+                    settings->ssh_tunnel_port, telnet_client->ssh_tunnel->user,
+                    settings->ssh_tunnel_alive_interval,
+                    settings->ssh_tunnel_host_key, NULL);
+
+        /* Fail if SSH tunnel connection does not succeed */
+        if (telnet_client->ssh_tunnel->session == NULL) {
+            /* Already aborted within guac_common_ssh_create_session() */
+            return NULL;
+        }
+
+        guac_client_log(client, GUAC_LOG_DEBUG,
+                "SSH session created for tunneling, initializing the tunnel.");
+
+        /* Initialize the tunnel or fail. */
+        if (guac_common_ssh_tunnel_init(telnet_client->ssh_tunnel,
+                settings->hostname, strtol(settings->port, NULL, 10))) {
+            guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                    "Unable to initialize SSH tunnel, aborting connection.");
+            return NULL;
+        }
+
+        /* If tunnel socket is not returned, bail out. */
+        if (telnet_client->ssh_tunnel->socket_path == NULL) {
+            guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                    "Unable to obtain socket for SSH tunnel, aborting.");
+            return NULL;
+        }
+
+        /* Overwrite the hostname with the path to the socket and zero out port. */
+        settings->hostname = guac_strdup(telnet_client->ssh_tunnel->socket_path);
+        settings->port = 0;
+
+        guac_client_log(client, GUAC_LOG_DEBUG,
+                "SSH tunnel connection succeeded.");
+
+        fd = socket(AF_UNIX, SOCK_STREAM, 0);
+
+        if (fd < 0) {
+            guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                "Error opening UNIX socket for telnet connection: %s",
+                strerror(errno));
+            return NULL;
+        }
+
+        struct sockaddr_un socket_addr = {
+            .sun_family = AF_UNIX
+        };
+        strncpy(socket_addr.sun_path, telnet_client->ssh_tunnel->socket_path,
+                sizeof(socket_addr.sun_path) - 1);
+
+        if (connect(fd, (const struct sockaddr *) &socket_addr, sizeof(struct sockaddr_un))) {
+            guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR,
+                "Error connecting to UNIX socket for SSH tunnel: %s",
+                telnet_client->ssh_tunnel->socket_path);
+            return NULL;
+        }
+
+    }
+
+    /* SSH tunneling is not in use, so open the standard TCP socket. */
+    else {
         struct addrinfo hints = {
             .ai_family   = AF_UNSPEC,
             .ai_socktype = SOCK_STREAM,
@@ -455,6 +571,7 @@ static telnet_t* __guac_telnet_create_session(guac_client* client) {
 
         /* Free addrinfo */
         freeaddrinfo(addresses);
+    }
 
     /* Open telnet session */
     telnet_t* telnet = telnet_init(__telnet_options, __guac_telnet_event_handler, 0, client);

src/protocols/telnet/telnet.h

@@ -24,6 +24,13 @@
 #include "settings.h"
 #include "terminal/terminal.h"
 
+#ifdef ENABLE_COMMON_SSH
+#include "common-ssh/sftp.h"
+#include "common-ssh/ssh.h"
+#include "common-ssh/tunnel.h"
+#include "common-ssh/user.h"
+#endif
+
 #include <guacamole/recording.h>
 #include <libtelnet.h>
 
@@ -77,6 +84,29 @@ typedef struct guac_telnet_client {
      */
     guac_recording* recording;
 
+#ifdef ENABLE_COMMON_SSH
+    /**
+     * The user and credentials used to authenticate for SFTP.
+     */
+    guac_common_ssh_user* sftp_user;
+
+    /**
+     * The SSH session used for SFTP.
+     */
+    guac_common_ssh_session* sftp_session;
+
+    /**
+     * An SFTP-based filesystem.
+     */
+    guac_common_ssh_sftp_filesystem* sftp_filesystem;
+
+    /**
+     * The SSH tunnel data.
+     */
+    guac_ssh_tunnel* ssh_tunnel;
+#endif
+
+
 } guac_telnet_client;
 
 /**