/*
* client.c - SSH client functions
*
* This file is part of the SSH Library
*
* Copyright (c) 2003-2013 by Aris Adamantiadis
*
* The SSH Library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The SSH Library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the SSH Library; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#include "config.h"
#include <stdio.h>
#ifndef _WIN32
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
#include "libssh/priv.h"
#include "libssh/ssh2.h"
#include "libssh/buffer.h"
#include "libssh/packet.h"
#include "libssh/options.h"
#include "libssh/socket.h"
#include "libssh/session.h"
#include "libssh/dh.h"
#ifdef WITH_GEX
#include "libssh/dh-gex.h"
#endif /* WITH_GEX */
#include "libssh/ecdh.h"
#include "libssh/threads.h"
#include "libssh/misc.h"
#include "libssh/pki.h"
#include "libssh/kex.h"
#define set_status(session, status) do {\
if (session->common.callbacks && session->common.callbacks->connect_status_function) \
session->common.callbacks->connect_status_function(session->common.callbacks->userdata, status); \
} while (0)
/**
* @internal
* @brief Callback to be called when the socket is connected or had a
* connection error. Changes the state of the session and updates the error
* message.
* @param code one of SSH_SOCKET_CONNECTED_OK or SSH_SOCKET_CONNECTED_ERROR
* @param user is a pointer to session
*/
static void socket_callback_connected(int code, int errno_code, void *user){
ssh_session session=(ssh_session)user;
if (session->session_state != SSH_SESSION_STATE_CONNECTING &&
session->session_state != SSH_SESSION_STATE_SOCKET_CONNECTED)
{
ssh_set_error(session,SSH_FATAL, "Wrong state in socket_callback_connected : %d",
session->session_state);
return;
}
SSH_LOG(SSH_LOG_RARE,"Socket connection callback: %d (%d)",code, errno_code);
if(code == SSH_SOCKET_CONNECTED_OK)
session->session_state=SSH_SESSION_STATE_SOCKET_CONNECTED;
else {
session->session_state=SSH_SESSION_STATE_ERROR;
ssh_set_error(session,SSH_FATAL,"%s",strerror(errno_code));
}
session->ssh_connection_callback(session);
}
/**
* @internal
*
* @brief Gets the banner from socket and saves it in session.
* Updates the session state
*
* @param data pointer to the beginning of header
* @param len size of the banner
* @param user is a pointer to session
* @returns Number of bytes processed, or zero if the banner is not complete.
*/
static int callback_receive_banner(const void *data, size_t len, void *user)
{
char *buffer = (char *)data;
ssh_session session=(ssh_session) user;
char *str = NULL;
size_t i;
int ret=0;
if (session->session_state != SSH_SESSION_STATE_SOCKET_CONNECTED) {
ssh_set_error(session,SSH_FATAL,
"Wrong state in callback_receive_banner : %d",
session->session_state);
return SSH_ERROR;
}
for (i = 0; i < len; ++i) {
#ifdef WITH_PCAP
if (session->pcap_ctx && buffer[i] == '\n') {
ssh_pcap_context_write(session->pcap_ctx,
SSH_PCAP_DIR_IN,
buffer,i+1,
i+1);
}
#endif
if (buffer[i] == '\r') {
buffer[i] = '\0';
}
if (buffer[i] == '\n') {
int cmp;
buffer[i] = '\0';
/* The server MAY send other lines of data... */
cmp = strncmp(buffer, "SSH-", 4);
if (cmp == 0) {
str = strdup(buffer);
if (str == NULL) {
return SSH_ERROR;
}
/* number of bytes read */
ret = i + 1;
session->serverbanner = str;
session->session_state = SSH_SESSION_STATE_BANNER_RECEIVED;
SSH_LOG(SSH_LOG_PACKET, "Received banner: %s", str);
session->ssh_connection_callback(session);
return ret;
} else {
SSH_LOG(SSH_LOG_DEBUG,
"ssh_protocol_version_exchange: %s",
buffer);
ret = i + 1;
break;
}
}
/* According to RFC 4253 the max banner length is 255 */
if (i > 255) {
/* Too big banner */
session->session_state=SSH_SESSION_STATE_ERROR;
ssh_set_error(session,
SSH_FATAL,
"Receiving banner: too large banner");
return 0;
}
}
return ret;
}
/** @internal
* @brief Sends a SSH banner to the server.
*
* @param session The SSH session to use.
*
* @param server Send client or server banner.
*
* @return 0 on success, < 0 on error.
*/
int ssh_send_banner(ssh_session session, int server)
{
const char *banner = CLIENT_BANNER_SSH2;
const char *terminator = "\r\n";
/* The maximum banner length is 255 for SSH2 */
char buffer[256] = {0};
size_t len;
int rc = SSH_ERROR;
if (server == 1) {
if (session->opts.custombanner == NULL){
session->serverbanner = strdup(banner);
if (session->serverbanner == NULL) {
goto end;
}
} else {
len = strlen(session->opts.custombanner);
session->serverbanner = malloc(len + 8 + 1);
if(session->serverbanner == NULL) {
goto end;
}
snprintf(session->serverbanner,
len + 8 + 1,
"SSH-2.0-%s",
session->opts.custombanner);
}
snprintf(buffer,
sizeof(buffer),
"%s%s",
session->serverbanner,
terminator);
} else {
session->clientbanner = strdup(banner);
if (session->clientbanner == NULL) {
goto end;
}
snprintf(buffer,
sizeof(buffer),
"%s%s",
session->clientbanner,
terminator);
}
rc = ssh_socket_write(session->socket, buffer, strlen(buffer));
if (rc == SSH_ERROR) {
goto end;
}
#ifdef WITH_PCAP
if (session->pcap_ctx != NULL) {
ssh_pcap_context_write(session->pcap_ctx,
SSH_PCAP_DIR_OUT,
buffer,
strlen(buffer),
strlen(buffer));
}
#endif
rc = SSH_OK;
end:
return rc;
}
/** @internal
* @brief launches the DH handshake state machine
* @param session session handle
* @returns SSH_OK or SSH_ERROR
* @warning this function returning is no proof that DH handshake is
* completed
*/
static int dh_handshake(ssh_session session) {
int rc = SSH_AGAIN;
switch (session->dh_handshake_state) {
case DH_STATE_INIT:
switch(session->next_crypto->kex_type){
case SSH_KEX_DH_GROUP1_SHA1:
case SSH_KEX_DH_GROUP14_SHA1:
case SSH_KEX_DH_GROUP14_SHA256:
case SSH_KEX_DH_GROUP16_SHA512:
case SSH_KEX_DH_GROUP18_SHA512:
rc = ssh_client_dh_init(session);
break;
#ifdef WITH_GEX
case SSH_KEX_DH_GEX_SHA1:
case SSH_KEX_DH_GEX_SHA256:
rc = ssh_client_dhgex_init(session);
break;
#endif /* WITH_GEX */
#ifdef HAVE_ECDH
case SSH_KEX_ECDH_SHA2_NISTP256:
case SSH_KEX_ECDH_SHA2_NISTP384:
case SSH_KEX_ECDH_SHA2_NISTP521:
rc = ssh_client_ecdh_init(session);
break;
#endif
#ifdef HAVE_CURVE25519
case SSH_KEX_CURVE25519_SHA256:
case SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG:
rc = ssh_client_curve25519_init(session);
break;
#endif
default:
rc = SSH_ERROR;
}
break;
case DH_STATE_INIT_SENT:
/* wait until ssh_packet_dh_reply is called */
break;
case DH_STATE_NEWKEYS_SENT:
/* wait until ssh_packet_newkeys is called */
break;
case DH_STATE_FINISHED:
return SSH_OK;
default:
ssh_set_error(session, SSH_FATAL, "Invalid state in dh_handshake(): %d",
session->dh_handshake_state);
return SSH_ERROR;
}
return rc;
}
static int ssh_service_request_termination(void *s){
ssh_session session = (ssh_session)s;
if(session->session_state == SSH_SESSION_STATE_ERROR ||
session->auth.service_state != SSH_AUTH_SERVICE_SENT)
return 1;
else
return 0;
}
/**
* @internal
*
* @brief Request a service from the SSH server.
*
* Service requests are for example: ssh-userauth, ssh-connection, etc.
*
* @param session The session to use to ask for a service request.
* @param service The service request.
*
* @return SSH_OK on success
* @return SSH_ERROR on error
* @return SSH_AGAIN No response received yet
* @bug actually only works with ssh-userauth
*/
int ssh_service_request(ssh_session session, const char *service) {
int rc=SSH_ERROR;
if(session->auth.service_state != SSH_AUTH_SERVICE_NONE)
goto pending;
rc = ssh_buffer_pack(session->out_buffer,
"bs",
SSH2_MSG_SERVICE_REQUEST,
service);
if (rc != SSH_OK){
ssh_set_error_oom(session);
return SSH_ERROR;
}
session->auth.service_state = SSH_AUTH_SERVICE_SENT;
if (ssh_packet_send(session) == SSH_ERROR) {
ssh_set_error(session, SSH_FATAL,
"Sending SSH2_MSG_SERVICE_REQUEST failed.");
return SSH_ERROR;
}
SSH_LOG(SSH_LOG_PACKET,
"Sent SSH_MSG_SERVICE_REQUEST (service %s)", service);
pending:
rc=ssh_handle_packets_termination(session,SSH_TIMEOUT_USER,
ssh_service_request_termination, session);
if (rc == SSH_ERROR) {
return SSH_ERROR;
}
switch(session->auth.service_state) {
case SSH_AUTH_SERVICE_DENIED:
ssh_set_error(session,SSH_FATAL,"ssh_auth_service request denied");
break;
case SSH_AUTH_SERVICE_ACCEPTED:
rc=SSH_OK;
break;
case SSH_AUTH_SERVICE_SENT:
rc=SSH_AGAIN;
break;
case SSH_AUTH_SERVICE_NONE:
rc=SSH_ERROR;
break;
}
return rc;
}
/**
* @addtogroup libssh_session
*
* @{
*/
/**
* @internal
*
* @brief A function to be called each time a step has been done in the
* connection.
*/
static void ssh_client_connection_callback(ssh_session session)
{
int rc;
switch(session->session_state) {
case SSH_SESSION_STATE_NONE:
case SSH_SESSION_STATE_CONNECTING:
break;
case SSH_SESSION_STATE_SOCKET_CONNECTED:
ssh_set_fd_towrite(session);
ssh_send_banner(session, 0);
break;
case SSH_SESSION_STATE_BANNER_RECEIVED:
if (session->serverbanner == NULL) {
goto error;
}
set_status(session, 0.4f);
SSH_LOG(SSH_LOG_PROTOCOL,
"SSH server banner: %s", session->serverbanner);
/* Here we analyze the different protocols the server allows. */
rc = ssh_analyze_banner(session, 0);
if (rc < 0) {
ssh_set_error(session, SSH_FATAL,
"No version of SSH protocol usable (banner: %s)",
session->serverbanner);
goto error;
}
ssh_packet_register_socket_callback(session, session->socket);
ssh_packet_set_default_callbacks(session);
session->session_state = SSH_SESSION_STATE_INITIAL_KEX;
rc = ssh_set_client_kex(session);
if (rc != SSH_OK) {
goto error;
}
rc = ssh_send_kex(session, 0);
if (rc < 0) {
goto error;
}
set_status(session, 0.5f);
break;
case SSH_SESSION_STATE_INITIAL_KEX:
/* TODO: This state should disappear in favor of get_key handle */
break;
case SSH_SESSION_STATE_KEXINIT_RECEIVED:
set_status(session,0.6f);
ssh_list_kex(&session->next_crypto->server_kex);
if (session->next_crypto->client_kex.methods[0] == NULL) {
/* in rekeying state if next_crypto client_kex is empty */
rc = ssh_set_client_kex(session);
if (rc != SSH_OK) {
goto error;
}
rc = ssh_send_kex(session, 0);
if (rc < 0) {
goto error;
}
}
if (ssh_kex_select_methods(session) == SSH_ERROR)
goto error;
set_status(session,0.8f);
session->session_state=SSH_SESSION_STATE_DH;
if (dh_handshake(session) == SSH_ERROR) {
goto error;
}
/* FALL THROUGH */
case SSH_SESSION_STATE_DH:
if(session->dh_handshake_state==DH_STATE_FINISHED){
set_status(session,1.0f);
session->connected = 1;
if (session->flags & SSH_SESSION_FLAG_AUTHENTICATED)
session->session_state = SSH_SESSION_STATE_AUTHENTICATED;
else
session->session_state=SSH_SESSION_STATE_AUTHENTICATING;
}
break;
case SSH_SESSION_STATE_AUTHENTICATING:
break;
case SSH_SESSION_STATE_ERROR:
goto error;
default:
ssh_set_error(session,SSH_FATAL,"Invalid state %d",session->session_state);
}
return;
error:
ssh_socket_close(session->socket);
session->alive = 0;
session->session_state=SSH_SESSION_STATE_ERROR;
}
/** @internal
* @brief describe under which conditions the ssh_connect function may stop
*/
static int ssh_connect_termination(void *user){
ssh_session session = (ssh_session)user;
switch(session->session_state){
case SSH_SESSION_STATE_ERROR:
case SSH_SESSION_STATE_AUTHENTICATING:
case SSH_SESSION_STATE_DISCONNECTED:
return 1;
default:
return 0;
}
}
/**
* @brief Connect to the ssh server.
*
* @param[in] session The ssh session to connect.
*
* @returns SSH_OK on success, SSH_ERROR on error.
* @returns SSH_AGAIN, if the session is in nonblocking mode,
* and call must be done again.
*
* @see ssh_new()
* @see ssh_disconnect()
*/
int ssh_connect(ssh_session session) {
int ret;
if (session == NULL) {
return SSH_ERROR;
}
switch(session->pending_call_state){
case SSH_PENDING_CALL_NONE:
break;
case SSH_PENDING_CALL_CONNECT:
goto pending;
default:
ssh_set_error(session,SSH_FATAL,"Bad call during pending SSH call in ssh_connect");
return SSH_ERROR;
}
session->alive = 0;
session->client = 1;
if (session->opts.fd == SSH_INVALID_SOCKET &&
session->opts.host == NULL &&
session->opts.ProxyCommand == NULL) {
ssh_set_error(session, SSH_FATAL, "Hostname required");
return SSH_ERROR;
}
/* If the system configuration files were not yet processed, do it now */
if (!session->opts.config_processed) {
ret = ssh_options_parse_config(session, NULL);
if (ret != 0) {
ssh_set_error(session, SSH_FATAL,
"Failed to process system configuration files");
return SSH_ERROR;
}
}
ret = ssh_options_apply(session);
if (ret < 0) {
ssh_set_error(session, SSH_FATAL, "Couldn't apply options");
return SSH_ERROR;
}
SSH_LOG(SSH_LOG_PROTOCOL,
"libssh %s, using threading %s",
ssh_copyright(),
ssh_threads_get_type());
session->ssh_connection_callback = ssh_client_connection_callback;
session->session_state=SSH_SESSION_STATE_CONNECTING;
ssh_socket_set_callbacks(session->socket,&session->socket_callbacks);
session->socket_callbacks.connected=socket_callback_connected;
session->socket_callbacks.data=callback_receive_banner;
session->socket_callbacks.exception=ssh_socket_exception_callback;
session->socket_callbacks.userdata=session;
if (session->opts.fd != SSH_INVALID_SOCKET) {
session->session_state=SSH_SESSION_STATE_SOCKET_CONNECTED;
ssh_socket_set_fd(session->socket, session->opts.fd);
ret=SSH_OK;
#ifndef _WIN32
} else if (session->opts.ProxyCommand != NULL){
ret = ssh_socket_connect_proxycommand(session->socket,
session->opts.ProxyCommand);
#endif
} else {
ret=ssh_socket_connect(session->socket,
session->opts.host,
session->opts.port > 0 ? session->opts.port : 22,
session->opts.bindaddr);
}
if (ret == SSH_ERROR) {
return SSH_ERROR;
}
set_status(session, 0.2f);
session->alive = 1;
SSH_LOG(SSH_LOG_PROTOCOL,"Socket connecting, now waiting for the callbacks to work");
pending:
session->pending_call_state=SSH_PENDING_CALL_CONNECT;
if(ssh_is_blocking(session)) {
int timeout = (session->opts.timeout * 1000) +
(session->opts.timeout_usec / 1000);
if (timeout == 0) {
timeout = 10 * 1000;
}
SSH_LOG(SSH_LOG_PACKET,"Actual timeout : %d", timeout);
ret = ssh_handle_packets_termination(session, timeout, ssh_connect_termination, session);
if (session->session_state != SSH_SESSION_STATE_ERROR &&
(ret == SSH_ERROR || !ssh_connect_termination(session))) {
ssh_set_error(session, SSH_FATAL,
"Timeout connecting to %s", session->opts.host);
session->session_state = SSH_SESSION_STATE_ERROR;
}
}
else {
ret = ssh_handle_packets_termination(session,
SSH_TIMEOUT_NONBLOCKING,
ssh_connect_termination,
session);
if (ret == SSH_ERROR) {
session->session_state = SSH_SESSION_STATE_ERROR;
}
}
SSH_LOG(SSH_LOG_PACKET,"current state : %d",session->session_state);
if(!ssh_is_blocking(session) && !ssh_connect_termination(session)){
return SSH_AGAIN;
}
session->pending_call_state=SSH_PENDING_CALL_NONE;
if(session->session_state == SSH_SESSION_STATE_ERROR || session->session_state == SSH_SESSION_STATE_DISCONNECTED)
return SSH_ERROR;
return SSH_OK;
}
/**
* @brief Get the issue banner from the server.
*
* This is the banner showing a disclaimer to users who log in,
* typically their right or the fact that they will be monitored.
*
* @param[in] session The SSH session to use.
*
* @return A newly allocated string with the banner, NULL on error.
*/
char *ssh_get_issue_banner(ssh_session session) {
if (session == NULL || session->banner == NULL) {
return NULL;
}
return ssh_string_to_char(session->banner);
}
/**
* @brief Get the version of the OpenSSH server, if it is not an OpenSSH server
* then 0 will be returned.
*
* You can use the SSH_VERSION_INT macro to compare version numbers.
*
* @param[in] session The SSH session to use.
*
* @return The version number if available, 0 otherwise.
*
* @code
* int openssh = ssh_get_openssh_version();
*
* if (openssh == SSH_INT_VERSION(6, 1, 0)) {
* printf("Version match!\m");
* }
* @endcode
*/
int ssh_get_openssh_version(ssh_session session) {
if (session == NULL) {
return 0;
}
return session->openssh;
}
/**
* @brief Disconnect from a session (client or server).
* The session can then be reused to open a new session.
*
* @param[in] session The SSH session to use.
*/
void ssh_disconnect(ssh_session session) {
struct ssh_iterator *it;
int rc;
if (session == NULL) {
return;
}
if (session->socket != NULL && ssh_socket_is_open(session->socket)) {
rc = ssh_buffer_pack(session->out_buffer,
"bdss",
SSH2_MSG_DISCONNECT,
SSH2_DISCONNECT_BY_APPLICATION,
"Bye Bye",
""); /* language tag */
if (rc != SSH_OK){
ssh_set_error_oom(session);
goto error;
}
ssh_packet_send(session);
ssh_socket_close(session->socket);
}
error:
session->recv_seq = 0;
session->send_seq = 0;
session->alive = 0;
if (session->socket != NULL){
ssh_socket_reset(session->socket);
}
session->opts.fd = SSH_INVALID_SOCKET;
session->session_state=SSH_SESSION_STATE_DISCONNECTED;
while ((it=ssh_list_get_iterator(session->channels)) != NULL) {
ssh_channel_do_free(ssh_iterator_value(ssh_channel,it));
ssh_list_remove(session->channels, it);
}
if(session->current_crypto){
crypto_free(session->current_crypto);
session->current_crypto=NULL;
}
if (session->next_crypto) {
crypto_free(session->next_crypto);
session->next_crypto = crypto_new();
if (session->next_crypto == NULL) {
ssh_set_error_oom(session);
}
}
if (session->in_buffer) {
ssh_buffer_reinit(session->in_buffer);
}
if (session->out_buffer) {
ssh_buffer_reinit(session->out_buffer);
}
if (session->in_hashbuf) {
ssh_buffer_reinit(session->in_hashbuf);
}
if (session->out_hashbuf) {
ssh_buffer_reinit(session->out_hashbuf);
}
session->auth.supported_methods = 0;
SAFE_FREE(session->serverbanner);
SAFE_FREE(session->clientbanner);
if(session->ssh_message_list){
ssh_message msg;
while((msg=ssh_list_pop_head(ssh_message ,session->ssh_message_list))
!= NULL){
ssh_message_free(msg);
}
ssh_list_free(session->ssh_message_list);
session->ssh_message_list=NULL;
}
if (session->packet_callbacks){
ssh_list_free(session->packet_callbacks);
session->packet_callbacks=NULL;
}
}
const char *ssh_copyright(void) {
return SSH_STRINGIFY(LIBSSH_VERSION) " (c) 2003-2019 "
"Aris Adamantiadis, Andreas Schneider "
"and libssh contributors. "
"Distributed under the LGPL, please refer to COPYING "
"file for information about your rights";
}
/** @} */