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SSH agent forwarding implementation

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This commit is contained in:
montdidier 2014-12-30 10:44:31 +08:00
parent 10050c1748
commit aca4ba3286
4 changed files with 287 additions and 55 deletions
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165
phpseclib/Net/SSH2.php
View File

@ -99,6 +99,10 @@ define('NET_SSH2_MASK_WINDOW_ADJUST', 0x00000020);
define('NET_SSH2_CHANNEL_EXEC', 0); // PuTTy uses 0x100
define('NET_SSH2_CHANNEL_SHELL', 1);
define('NET_SSH2_CHANNEL_SUBSYSTEM', 2);
define('NET_SSH2_CHANNEL_AGENT_REQUEST', 3);
define('NET_SSH2_CHANNEL_AGENT_FORWARD', 4);
/**#@-*/
/**#@+
@ -840,6 +844,14 @@ class Net_SSH2
*/
var $windowRows = 24;
/**
* A System_SSH_Agent for use in the SSH2 Agent Forwarding scenario
*
* @var System_SSH_Agent
* @access private
*/
var $agent;
/**
* Default Constructor.
*
@ -2132,9 +2144,11 @@ class Net_SSH2
*/
function _ssh_agent_login($username, $agent)
{
$this->agent = $agent;
$keys = $agent->requestIdentities();
foreach ($keys as $key) {
if ($this->_privatekey_login($username, $key)) {
$this->agent->_on_login_success($this);
return true;
}
}
@ -2234,6 +2248,7 @@ class Net_SSH2
return false;
}
/**
* Set Timeout
*
@ -2311,6 +2326,7 @@ class Net_SSH2
if (!$this->_send_binary_packet($packet)) {
return false;
}
$response = $this->_get_binary_packet();
if ($response === false) {
user_error('Connection closed by server');
@ -2341,6 +2357,7 @@ class Net_SSH2
// "maximum size of an individual data packet". ie. SSH_MSG_CHANNEL_DATA. RFC4254#section-5.2 corroborates.
$packet = pack('CNNa*CNa*',
NET_SSH2_MSG_CHANNEL_REQUEST, $this->server_channels[NET_SSH2_CHANNEL_EXEC], strlen('exec'), 'exec', 1, strlen($command), $command);
if (!$this->_send_binary_packet($packet)) {
return false;
}
@ -2808,6 +2825,8 @@ class Net_SSH2
}
$payload = $this->_get_binary_packet();
}
default:
break;
}
// see http://tools.ietf.org/html/rfc4252#section-5.4; only called when the encryption has been activated and when we haven't already logged in
@ -2830,23 +2849,6 @@ class Net_SSH2
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
}
$payload = $this->_get_binary_packet();
break;
case NET_SSH2_MSG_CHANNEL_OPEN: // see http://tools.ietf.org/html/rfc4254#section-5.1
$this->_string_shift($payload, 1);
extract(unpack('Nlength', $this->_string_shift($payload, 4)));
$this->errors[] = 'SSH_MSG_CHANNEL_OPEN: ' . utf8_decode($this->_string_shift($payload, $length));
$this->_string_shift($payload, 4); // skip over client channel
extract(unpack('Nserver_channel', $this->_string_shift($payload, 4)));
$packet = pack('CN3a*Na*',
NET_SSH2_MSG_REQUEST_FAILURE, $server_channel, NET_SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED, 0, '', 0, '');
if (!$this->_send_binary_packet($packet)) {
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
}
$payload = $this->_get_binary_packet();
break;
case NET_SSH2_MSG_CHANNEL_WINDOW_ADJUST:
@ -2983,53 +2985,97 @@ class Net_SSH2
return '';
}
extract(unpack('Ctype/Nchannel', $this->_string_shift($response, 5)));
extract(unpack('Ctype', $this->_string_shift($response, 1)));
$this->window_size_server_to_client[$channel]-= strlen($response);
// resize the window, if appropriate
if ($this->window_size_server_to_client[$channel] < 0) {
$packet = pack('CNN', NET_SSH2_MSG_CHANNEL_WINDOW_ADJUST, $this->server_channels[$channel], $this->window_size);
if (!$this->_send_binary_packet($packet)) {
return false;
}
$this->window_size_server_to_client[$channel]+= $this->window_size;
if ($type == NET_SSH2_MSG_CHANNEL_OPEN) {
extract(unpack('Nlength', $this->_string_shift($response, 4)));
} else {
extract(unpack('Nchannel', $this->_string_shift($response, 4)));
}
switch ($this->channel_status[$channel]) {
case NET_SSH2_MSG_CHANNEL_OPEN:
switch ($type) {
case NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
extract(unpack('Nserver_channel', $this->_string_shift($response, 4)));
$this->server_channels[$channel] = $server_channel;
extract(unpack('Nwindow_size', $this->_string_shift($response, 4)));
$this->window_size_client_to_server[$channel] = $window_size;
$temp = unpack('Npacket_size_client_to_server', $this->_string_shift($response, 4));
$this->packet_size_client_to_server[$channel] = $temp['packet_size_client_to_server'];
return $client_channel == $channel ? true : $this->_get_channel_packet($client_channel, $skip_extended);
//case NET_SSH2_MSG_CHANNEL_OPEN_FAILURE:
default:
user_error('Unable to open channel');
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
// will not be setup yet on incoming channel open request
if (isset($channel) && isset($this->channel_status[$channel]) && isset($this->window_size_server_to_client[$channel])) {
$this->window_size_server_to_client[$channel]-= strlen($response);
// resize the window, if appropriate
if ($this->window_size_server_to_client[$channel] < 0) {
$packet = pack('CNN', NET_SSH2_MSG_CHANNEL_WINDOW_ADJUST, $this->server_channels[$channel], $this->window_size);
if (!$this->_send_binary_packet($packet)) {
return false;
}
break;
case NET_SSH2_MSG_CHANNEL_REQUEST:
switch ($type) {
case NET_SSH2_MSG_CHANNEL_SUCCESS:
return true;
case NET_SSH2_MSG_CHANNEL_FAILURE:
return false;
default:
user_error('Unable to fulfill channel request');
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
}
case NET_SSH2_MSG_CHANNEL_CLOSE:
return $type == NET_SSH2_MSG_CHANNEL_CLOSE ? true : $this->_get_channel_packet($client_channel, $skip_extended);
$this->window_size_server_to_client[$channel]+= $this->window_size;
}
switch ($this->channel_status[$channel]) {
case NET_SSH2_MSG_CHANNEL_OPEN:;
switch ($type) {
case NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
extract(unpack('Nserver_channel', $this->_string_shift($response, 4)));
$this->server_channels[$channel] = $server_channel;
extract(unpack('Nwindow_size', $this->_string_shift($response, 4)));
$this->window_size_client_to_server[$channel] = $window_size;
$temp = unpack('Npacket_size_client_to_server', $this->_string_shift($response, 4));
$this->packet_size_client_to_server[$channel] = $temp['packet_size_client_to_server'];
return $client_channel == $channel ? true : $this->_get_channel_packet($client_channel, $skip_extended);
//case NET_SSH2_MSG_CHANNEL_OPEN_FAILURE:
default:
user_error('Unable to open channel');
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
}
break;
case NET_SSH2_MSG_CHANNEL_REQUEST:
switch ($type) {
case NET_SSH2_MSG_CHANNEL_SUCCESS:
return true;
case NET_SSH2_MSG_CHANNEL_FAILURE:
return false;
default:
user_error('Unable to fulfill channel request');
return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
}
case NET_SSH2_MSG_CHANNEL_CLOSE:
return $type == NET_SSH2_MSG_CHANNEL_CLOSE ? true : $this->_get_channel_packet($client_channel, $skip_extended);
}
}
// ie. $this->channel_status[$channel] == NET_SSH2_MSG_CHANNEL_DATA
switch ($type) {
case NET_SSH2_MSG_CHANNEL_OPEN: // see http://tools.ietf.org/html/rfc4254#section-5.1
$data = $this->_string_shift($response, $length);
switch($data) {
case 'auth-agent':
case 'auth-agent@openssh.com':
if (!isset($this->agent)) {
break 2;
}
break;
default:
break 2;
}
$new_channel = NET_SSH2_CHANNEL_AGENT_FORWARD;
extract(unpack('Nserver_channel', $this->_string_shift($response, 4)));
extract(unpack('Nremote_window_size', $this->_string_shift($response, 4)));
extract(unpack('Nremote_maximum_packet_size', $this->_string_shift($response, 4)));
$this->packet_size_client_to_server[$new_channel] = $remote_window_size;
$this->window_size_server_to_client[$new_channel] = $remote_maximum_packet_size;
$this->window_size_client_to_server[$new_channel] = $this->window_size;
$packet_size = 0x4000;
$packet = pack('CN4',
NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, $server_channel, $new_channel, $packet_size, $packet_size);
$this->server_channels[$new_channel] = $server_channel;
$this->channel_status[$new_channel] = NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION;
if (!$this->_send_binary_packet($packet)) {
return false;
}
break;
case NET_SSH2_MSG_CHANNEL_DATA:
/*
if ($channel == NET_SSH2_CHANNEL_EXEC) {
@ -3042,6 +3088,15 @@ class Net_SSH2
*/
extract(unpack('Nlength', $this->_string_shift($response, 4)));
$data = $this->_string_shift($response, $length);
if ($channel == NET_SSH2_CHANNEL_AGENT_FORWARD) {
$agent_response = $this->agent->_forward_data($data);
if (!is_bool($agent_response)) {
$this->_send_channel_packet($channel, $agent_response);
}
break;
}
if ($client_channel == $channel) {
return $data;
}

153
phpseclib/System/SSH/Agent.php
View File

@ -1,4 +1,5 @@
<?php
/**
* Pure-PHP ssh-agent client.
*
@ -225,6 +226,29 @@ class System_SSH_Agent
*/
var $fsock;
/**
* Did we request agent forwarding
*
* @access private
*/
var $request_forwarding;
/**
* Buffer for accumulating forwarded authentication
* agent data arriving on SSH data channel destined
* for agent unix socket
*
* @access private
*/
var $socket_buffer = '';
/**
* Tracking the number of bytes we are expecting
* to arrive for the agent socket on the SSH data
* channel
*/
var $expected_bytes = 0;
/**
* Default Constructor
*
@ -310,4 +334,133 @@ class System_SSH_Agent
return $identities;
}
/**
* Request the remote server to forward authentication requests to the local SSH agent
*
* @param Net_SSH2 $ssh
* @return Boolean
* @access public
*/
function startSSHForwarding($ssh)
{
if (!$this->request_forwarding) {
$this->request_forwarding = true;
$this->_request_forwarding($ssh);
}
}
/**
* Request the remote server to stop forwarding authentication requests to the local SSH agent
*
* @param Net_SSH2 $ssh
* @return Boolean
* @access public
*/
function stopSSHForwarding($ssh)
{
if ($this->request_forwarding) {
$ssh->_close_channel(NET_SSH2_CHANNEL_AGENT_FORWARD);
$this->request_forwarding = false;
}
}
/**
* The worker function to make a request to a remote server
* asking it to forward authentication requests to the local SSH
* agent
*
* @param Net_SSH2 $ssh
* @return Boolean
* @access private
*/
function _request_forwarding($ssh)
{
$ssh->window_size_server_to_client[NET_SSH2_CHANNEL_AGENT_REQUEST] = $ssh->window_size;
$packet_size = 0x4000;
$packet = pack('CNa*N3',
NET_SSH2_MSG_CHANNEL_OPEN, strlen('session'), 'session', NET_SSH2_CHANNEL_AGENT_REQUEST, $ssh->window_size_server_to_client[NET_SSH2_CHANNEL_AGENT_REQUEST], $packet_size);
$ssh->channel_status[NET_SSH2_CHANNEL_AGENT_REQUEST] = NET_SSH2_MSG_CHANNEL_OPEN;
if (!$ssh->_send_binary_packet($packet)) {
return false;
}
$response = $ssh->_get_channel_packet(NET_SSH2_CHANNEL_AGENT_REQUEST);
if ($response === false) {
return false;
}
$packet = pack('CNNa*C',
NET_SSH2_MSG_CHANNEL_REQUEST, $ssh->server_channels[NET_SSH2_CHANNEL_AGENT_REQUEST], strlen('auth-agent-req@openssh.com'), 'auth-agent-req@openssh.com', 1);
$ssh->channel_status[NET_SSH2_CHANNEL_AGENT_REQUEST] = NET_SSH2_MSG_CHANNEL_REQUEST;
if (!$ssh->_send_binary_packet($packet)) {
return false;
}
$response = $ssh->_get_channel_packet(NET_SSH2_CHANNEL_AGENT_REQUEST);
if ($response === false) {
return false;
}
return true;
}
/**
* On Successful Login
*
* This method should be called upon successful SSH login if you
* wish to give the SSH Agent an opportunity to take further
* action. i.e. request agent forwarding
*
* @param Net_SSH2 $ssh
* @access private
*/
function _on_login_success($ssh)
{
if ($this->request_forwarding) {
$this->_request_forwarding($ssh);
}
}
/**
* Forward data to SSH Agent and return data reply
*
* @param String $data
* @return data from SSH Agent
* @access private
*/
function _forward_data($data)
{
if ($this->expected_bytes > 0) {
$this->socket_buffer .= $data;
$this->expected_bytes -= strlen($data);
} else {
$agent_data_bytes = current(unpack('N', $data));
$current_data_bytes = strlen($data);
$this->socket_buffer = $data;
if ($current_data_bytes != $agent_data_bytes + 4) {
$this->expected_bytes = ($agent_data_bytes + 4) - $current_data_bytes;
return false;
}
}
if (strlen($this->socket_buffer) != fwrite($this->fsock, $this->socket_buffer)) {
user_error('Connection closed attempting to forward data to SSH agent');
}
$this->socket_buffer = '';
$this->expected_bytes = 0;
$agent_reply_bytes = current(unpack('N', fread($this->fsock, 4)));
$agent_reply_data = fread($this->fsock, $agent_reply_bytes);
$agent_reply_data = current(unpack('a*', $agent_reply_data));
return pack('Na*', $agent_reply_bytes, $agent_reply_data);
}
}

22
tests/Functional/Net/SSH2AgentTest.php
View File

@ -27,5 +27,27 @@ class Functional_Net_SSH2AgentTest extends PhpseclibFunctionalTestCase
$ssh->login($this->getEnv('SSH_USERNAME'), $agent),
'SSH2 login using Agent failed.'
);
return array('ssh' => $ssh, 'ssh-agent' => $agent);
}
/**
* @depends testAgentLogin
*/
public function testAgentForward($args)
{
$ssh = $args['ssh'];
$agent = $args['ssh-agent'];
$hostname = $this->getEnv('SSH_HOSTNAME');
$username = $this->getEnv('SSH_USERNAME');
$this->assertEquals($username, trim($ssh->exec('whoami')));
$agent->startSSHForwarding($ssh);
$this->assertEquals($username, trim($ssh->exec("ssh " . $username . "@" . $hostname . ' \'whoami\'')));
$agent->stopSSHForwarding($ssh);
return $args;
}
}

2
travis/setup-secure-shell.sh
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@ -28,4 +28,6 @@ ssh-add "$HOME/.ssh/id_rsa"
# Allow the private key of the travis user to log in as phpseclib user
sudo mkdir -p "/home/$USERNAME/.ssh/"
sudo cp "$HOME/.ssh/id_rsa.pub" "/home/$USERNAME/.ssh/authorized_keys"
sudo ssh-keyscan -t rsa localhost > "/tmp/known_hosts"
sudo cp "/tmp/known_hosts" "/home/$USERNAME/.ssh/known_hosts"
sudo chown "$USERNAME:$USERNAME" "/home/$USERNAME/.ssh/" -R