From 8394ef0ed639cd294e81dff15bf87923e5994e17 Mon Sep 17 00:00:00 2001 From: Virtually Nick Date: Sat, 18 Feb 2023 08:46:11 -0500 Subject: [PATCH] [WIP] Add SSH tunneling settings for SSH. --- src/protocols/ssh/client.c | 4 ++ src/protocols/ssh/settings.c | 113 ++++++++++++++++++++++++++++++++++- src/protocols/ssh/settings.h | 68 +++++++++++++++++++-- src/protocols/ssh/ssh.c | 91 ++++++++++++++++++++++++++++ src/protocols/ssh/ssh.h | 6 ++ 5 files changed, 275 insertions(+), 7 deletions(-) diff --git a/src/protocols/ssh/client.c b/src/protocols/ssh/client.c index 4a314f06..ca30ad85 100644 --- a/src/protocols/ssh/client.c +++ b/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); diff --git a/src/protocols/ssh/settings.c b/src/protocols/ssh/settings.c index 686ef637..57b15a55 100644 --- a/src/protocols/ssh/settings.c +++ b/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); diff --git a/src/protocols/ssh/settings.h b/src/protocols/ssh/settings.h index 103ff029..ac1db4e6 100644 --- a/src/protocols/ssh/settings.h +++ b/src/protocols/ssh/settings.h @@ -26,12 +26,6 @@ #include -/** - * 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. diff --git a/src/protocols/ssh/ssh.c b/src/protocols/ssh/ssh.c index 2ebe0687..db97fbb9 100644 --- a/src/protocols/ssh/ssh.c +++ b/src/protocols/ssh/ssh.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include #include @@ -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 */ diff --git a/src/protocols/ssh/ssh.h b/src/protocols/ssh/ssh.h index 1d1aae73..472a31c4 100644 --- a/src/protocols/ssh/ssh.h +++ b/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. */