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[WIP] Add SSH tunneling settings for Telnet.

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This commit is contained in:
Virtually Nick 2023-02-18 08:46:24 -05:00
parent 8394ef0ed6
commit ad751f109a
6 changed files with 657 additions and 47 deletions
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2
src/protocols/telnet/Makefile.am
View File

@ -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@

30
src/protocols/telnet/client.c
View File

@ -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);

287
src/protocols/telnet/settings.c
View File

@ -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);

144
src/protocols/telnet/settings.h
View File

@ -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;
/**

117
src/protocols/telnet/telnet.c
View File

@ -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);

30
src/protocols/telnet/telnet.h
View File

@ -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;
/**