[WIP] Add SSH tunneling settings for SSH.

src/protocols/ssh/client.c

@@ -22,6 +22,7 @@
 #include "argv.h"
 #include "client.h"
 #include "common-ssh/sftp.h"
+#include "common-ssh/tunnel.h"
 #include "ssh.h"
 #include "terminal/terminal.h"
 #include "user.h"
@@ -101,6 +102,9 @@ int guac_ssh_client_free_handler(guac_client* client) {
     if (ssh_client->recording != NULL)
         guac_recording_free(ssh_client->recording);
 
+    if (ssh_client->ssh_tunnel != NULL)
+        guac_common_ssh_tunnel_cleanup(ssh_client->ssh_tunnel);
+
     /* Free interactive SSH session */
     if (ssh_client->session != NULL)
         guac_common_ssh_destroy_session(ssh_client->session);

src/protocols/ssh/settings.c

@@ -22,6 +22,7 @@
 #include "argv.h"
 #include "client.h"
 #include "common/defaults.h"
+#include "common-ssh/ssh-constants.h"
 #include "settings.h"
 #include "terminal/terminal.h"
 
@@ -47,6 +48,15 @@ const char* GUAC_SSH_CLIENT_ARGS[] = {
     "sftp-disable-upload",
     "private-key",
     "passphrase",
+    "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",
 #ifdef ENABLE_SSH_AGENT
     "enable-agent",
 #endif
@@ -148,6 +158,55 @@ enum SSH_ARGS_IDX {
      */
     IDX_PASSPHRASE,
 
+    /**
+     * 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,
+
 #ifdef ENABLE_SSH_AGENT
     /**
      * Whether SSH agent forwarding support should be enabled.
@@ -418,6 +477,49 @@ guac_ssh_settings* guac_ssh_parse_args(guac_user* user,
         guac_user_parse_args_boolean(user, GUAC_SSH_CLIENT_ARGS, argv,
                 IDX_SFTP_DISABLE_UPLOAD, false);
 
+    /* Parse SSH tunneling. */
+    settings->ssh_tunnel =
+        guac_user_parse_args_boolean(user, GUAC_SSH_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_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_HOST, NULL);
+
+        settings->ssh_tunnel_port =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PORT, GUAC_COMMON_SSH_DEFAULT_PORT);
+
+        settings->ssh_tunnel_host_key =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_HOST_KEY, NULL);
+
+        settings->ssh_tunnel_username =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_USERNAME, NULL);
+
+        settings->ssh_tunnel_password =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PASSWORD, NULL);
+
+        settings->ssh_tunnel_private_key =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PRIVATE_KEY, NULL);
+
+        settings->ssh_tunnel_passphrase =
+            guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_PASSPHRASE, NULL);
+
+        settings->ssh_tunnel_alive_interval =
+            guac_user_parse_args_int(user, GUAC_SSH_CLIENT_ARGS, argv,
+                    IDX_SSH_TUNNEL_ALIVE_INTERVAL,
+                    GUAC_COMMON_SSH_DEFAULT_ALIVE_INTERVAL);
+
+    }
+
 #ifdef ENABLE_SSH_AGENT
     settings->enable_agent =
         guac_user_parse_args_boolean(user, GUAC_SSH_CLIENT_ARGS, argv,
@@ -427,7 +529,7 @@ guac_ssh_settings* guac_ssh_parse_args(guac_user* user,
     /* Read port */
     settings->port =
         guac_user_parse_args_string(user, GUAC_SSH_CLIENT_ARGS, argv,
-                IDX_PORT, GUAC_SSH_DEFAULT_PORT);
+                IDX_PORT, GUAC_COMMON_SSH_DEFAULT_PORT);
 
     /* Read-only mode */
     settings->read_only =
@@ -578,6 +680,15 @@ void guac_ssh_settings_free(guac_ssh_settings* settings) {
     /* Free SFTP settings */
     free(settings->sftp_root_directory);
 
+    /* Free tunnel settings */
+    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 typescript settings */
     free(settings->typescript_name);
     free(settings->typescript_path);

src/protocols/ssh/settings.h

@@ -26,12 +26,6 @@
 
 #include <stdbool.h>
 
-/**
- * The port to connect to when initiating any SSH connection, if no other port
- * is specified.
- */
-#define GUAC_SSH_DEFAULT_PORT "22"
-
 /**
  * The filename to use for the typescript, if not specified.
  */
@@ -178,6 +172,68 @@ typedef struct guac_ssh_settings {
      */
     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;
+
 #ifdef ENABLE_SSH_AGENT
     /**
      * Whether the SSH agent is enabled.

src/protocols/ssh/ssh.c

@@ -37,6 +37,7 @@
 #include <guacamole/client.h>
 #include <guacamole/recording.h>
 #include <guacamole/socket.h>
+#include <guacamole/string.h>
 #include <guacamole/timestamp.h>
 #include <guacamole/wol.h>
 #include <openssl/err.h>
@@ -226,6 +227,96 @@ void* ssh_client_thread(void* data) {
         return NULL;
     }
 
+    if (settings->ssh_tunnel) {
+
+        /* Allocate memory for the SSH tunnel data. */
+        ssh_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. */
+        ssh_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;
+        }
+
+        ssh_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(ssh_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(ssh_client->ssh_tunnel->user,
+                    settings->ssh_tunnel_password);
+
+        }
+
+        /* Attempt SSH tunnel connection */
+        ssh_client->ssh_tunnel->session =
+            guac_common_ssh_create_session(client, settings->ssh_tunnel_host,
+                    settings->ssh_tunnel_port, ssh_client->ssh_tunnel->user,
+                    settings->ssh_tunnel_alive_interval,
+                    settings->ssh_tunnel_host_key, NULL);
+
+        /* Fail if SSH tunnel connection does not succeed */
+        if (ssh_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(ssh_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 (ssh_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(ssh_client->ssh_tunnel->socket_path);
+        settings->port = 0;
+
+        guac_client_log(client, GUAC_LOG_DEBUG,
+                "SSH tunnel connection succeeded.");
+
+    }
+
     char ssh_ttymodes[GUAC_SSH_TTYMODES_SIZE(1)];
 
     /* Set up screen recording, if requested */

src/protocols/ssh/ssh.h

@@ -25,6 +25,7 @@
 #include "common/clipboard.h"
 #include "common-ssh/sftp.h"
 #include "common-ssh/ssh.h"
+#include "common-ssh/tunnel.h"
 #include "common-ssh/user.h"
 #include "settings.h"
 #include "terminal/terminal.h"
@@ -60,6 +61,11 @@ typedef struct guac_ssh_client {
      */
     pthread_t client_thread;
 
+    /**
+     * If SSH tunneling is enabled, this is the object that tracks the tunnel.
+     */
+    guac_ssh_tunnel* ssh_tunnel;
+
     /**
      * The user and credentials to use for all SSH sessions.
      */