From 3b33f63fc1de9e54fa2637edfffc3571c691a266 Mon Sep 17 00:00:00 2001 From: Virtually Nick Date: Sat, 18 Feb 2023 08:46:35 -0500 Subject: [PATCH] [WIP] Add SSH tunneling settings for VNC. --- src/protocols/vnc/client.c | 8 +++ src/protocols/vnc/settings.c | 114 ++++++++++++++++++++++++++++++++++- src/protocols/vnc/settings.h | 63 +++++++++++++++++++ src/protocols/vnc/vnc.c | 95 ++++++++++++++++++++++++++++- src/protocols/vnc/vnc.h | 6 ++ 5 files changed, 283 insertions(+), 3 deletions(-) diff --git a/src/protocols/vnc/client.c b/src/protocols/vnc/client.c index 638c14de..cb1df4c0 100644 --- a/src/protocols/vnc/client.c +++ b/src/protocols/vnc/client.c @@ -26,6 +26,7 @@ #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 @@ -62,6 +63,10 @@ int guac_client_init(guac_client* client) { client->leave_handler = guac_vnc_user_leave_handler; client->free_handler = guac_vnc_client_free_handler; +#ifdef ENABLE_COMMON_SSH + guac_common_ssh_init(client); +#endif + return 0; } @@ -121,6 +126,9 @@ int guac_vnc_client_free_handler(guac_client* client) { if (vnc_client->sftp_user) guac_common_ssh_destroy_user(vnc_client->sftp_user); + if (vnc_client->ssh_tunnel) + guac_common_ssh_tunnel_cleanup(vnc_client->ssh_tunnel); + guac_common_ssh_uninit(); #endif diff --git a/src/protocols/vnc/settings.c b/src/protocols/vnc/settings.c index a476b2c1..ce23c2ea 100644 --- a/src/protocols/vnc/settings.c +++ b/src/protocols/vnc/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 @@ -75,6 +76,15 @@ const char* GUAC_VNC_CLIENT_ARGS[] = { "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 "recording-path", @@ -284,6 +294,55 @@ enum VNC_ARGS_IDX { * "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 /** @@ -547,12 +606,13 @@ guac_vnc_settings* guac_vnc_parse_args(guac_user* user, /* SFTP root directory */ settings->sftp_root_directory = guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, - IDX_SFTP_ROOT_DIRECTORY, "/"); + 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_VNC_CLIENT_ARGS, argv, - IDX_SFTP_SERVER_ALIVE_INTERVAL, 0); + IDX_SFTP_SERVER_ALIVE_INTERVAL, + GUAC_COMMON_SSH_DEFAULT_ALIVE_INTERVAL); settings->sftp_disable_download = guac_user_parse_args_boolean(user, GUAC_VNC_CLIENT_ARGS, argv, @@ -561,6 +621,49 @@ guac_vnc_settings* guac_vnc_parse_args(guac_user* user, settings->sftp_disable_upload = guac_user_parse_args_boolean(user, GUAC_VNC_CLIENT_ARGS, argv, IDX_SFTP_DISABLE_UPLOAD, false); + + /* Parse SSH tunneling settings. */ + settings->ssh_tunnel = + guac_user_parse_args_boolean(user, GUAC_VNC_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_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_HOST, NULL); + + settings->ssh_tunnel_port = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_PORT, GUAC_COMMON_SSH_DEFAULT_PORT); + + settings->ssh_tunnel_host_key = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_HOST_KEY, NULL); + + settings->ssh_tunnel_username = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_USERNAME, NULL); + + settings->ssh_tunnel_password = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_PASSWORD, NULL); + + settings->ssh_tunnel_private_key = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_PRIVATE_KEY, NULL); + + settings->ssh_tunnel_passphrase = + guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_PASSPHRASE, NULL); + + settings->ssh_tunnel_alive_interval = + guac_user_parse_args_int(user, GUAC_VNC_CLIENT_ARGS, argv, + IDX_SSH_TUNNEL_ALIVE_INTERVAL, + GUAC_COMMON_SSH_DEFAULT_ALIVE_INTERVAL); + + } #endif /* Read recording path */ @@ -670,6 +773,13 @@ void guac_vnc_settings_free(guac_vnc_settings* settings) { free(settings->sftp_port); free(settings->sftp_private_key); free(settings->sftp_username); + 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); #endif #ifdef ENABLE_PULSE diff --git a/src/protocols/vnc/settings.h b/src/protocols/vnc/settings.h index 76139bd4..c0ee1241 100644 --- a/src/protocols/vnc/settings.h +++ b/src/protocols/vnc/settings.h @@ -231,6 +231,69 @@ typedef struct guac_vnc_settings { * 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 /** diff --git a/src/protocols/vnc/vnc.c b/src/protocols/vnc/vnc.c index 3b94d5e7..6d59008a 100644 --- a/src/protocols/vnc/vnc.c +++ b/src/protocols/vnc/vnc.c @@ -38,6 +38,7 @@ #ifdef ENABLE_COMMON_SSH #include "common-ssh/sftp.h" #include "common-ssh/ssh.h" +#include "common-ssh/tunnel.h" #include "sftp.h" #endif @@ -45,6 +46,7 @@ #include #include #include +#include #include #include #include @@ -297,6 +299,98 @@ void* guac_vnc_client_thread(void* data) { rfbClientLog = guac_vnc_client_log_info; rfbClientErr = guac_vnc_client_log_error; +#ifdef ENABLE_COMMON_SSH + /* If SSH tunneling is enabled, we set up the tunnel and redirect the connection. */ + if (settings->ssh_tunnel) { + + /* Allocate memory for the SSH tunnel data. */ + vnc_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. */ + vnc_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; + } + + vnc_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(vnc_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(vnc_client->ssh_tunnel->user, + settings->ssh_tunnel_password); + + } + + /* Attempt SSH tunnel connection */ + vnc_client->ssh_tunnel->session = + guac_common_ssh_create_session(client, settings->ssh_tunnel_host, + settings->ssh_tunnel_port, vnc_client->ssh_tunnel->user, + settings->ssh_tunnel_alive_interval, + settings->ssh_tunnel_host_key, NULL); + + /* Fail if SSH tunnel connection does not succeed */ + if (vnc_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(vnc_client->ssh_tunnel, + settings->hostname, settings->port)) { + 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 (vnc_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(vnc_client->ssh_tunnel->socket_path); + settings->port = 0; + + guac_client_log(client, GUAC_LOG_DEBUG, + "SSH tunnel connection succeeded."); + } +#endif + /* Attempt connection */ rfbClient* rfb_client = guac_vnc_get_client(client); int retries_remaining = settings->retries; @@ -330,7 +424,6 @@ void* guac_vnc_client_thread(void* data) { #endif #ifdef ENABLE_COMMON_SSH - guac_common_ssh_init(client); /* Connect via SSH if SFTP is enabled */ if (settings->enable_sftp) { diff --git a/src/protocols/vnc/vnc.h b/src/protocols/vnc/vnc.h index bdc62e6d..13fdcda9 100644 --- a/src/protocols/vnc/vnc.h +++ b/src/protocols/vnc/vnc.h @@ -39,6 +39,7 @@ #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 @@ -117,6 +118,11 @@ typedef struct guac_vnc_client { * An SFTP-based filesystem. */ guac_common_ssh_sftp_filesystem* sftp_filesystem; + + /** + * The data structure containing SSH tunnel-related information. + */ + guac_ssh_tunnel* ssh_tunnel; #endif /**