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SSH agent forwarding implementation
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montdidier
parent
10050c1748
commit
aca4ba3286
@ -99,6 +99,10 @@ define('NET_SSH2_MASK_WINDOW_ADJUST', 0x00000020);
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define('NET_SSH2_CHANNEL_EXEC', 0); // PuTTy uses 0x100
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define('NET_SSH2_CHANNEL_SHELL', 1);
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define('NET_SSH2_CHANNEL_SUBSYSTEM', 2);
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define('NET_SSH2_CHANNEL_AGENT_REQUEST', 3);
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define('NET_SSH2_CHANNEL_AGENT_FORWARD', 4);
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/**#@-*/
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/**#@+
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@ -840,6 +844,14 @@ class Net_SSH2
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*/
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var $windowRows = 24;
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/**
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* A System_SSH_Agent for use in the SSH2 Agent Forwarding scenario
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*
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* @var System_SSH_Agent
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* @access private
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*/
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var $agent;
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/**
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* Default Constructor.
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*
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@ -2132,9 +2144,11 @@ class Net_SSH2
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*/
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function _ssh_agent_login($username, $agent)
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{
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$this->agent = $agent;
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$keys = $agent->requestIdentities();
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foreach ($keys as $key) {
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if ($this->_privatekey_login($username, $key)) {
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$this->agent->_on_login_success($this);
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return true;
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}
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}
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@ -2234,6 +2248,7 @@ class Net_SSH2
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return false;
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}
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/**
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* Set Timeout
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*
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@ -2311,6 +2326,7 @@ class Net_SSH2
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if (!$this->_send_binary_packet($packet)) {
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return false;
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}
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$response = $this->_get_binary_packet();
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if ($response === false) {
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user_error('Connection closed by server');
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@ -2341,6 +2357,7 @@ class Net_SSH2
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// "maximum size of an individual data packet". ie. SSH_MSG_CHANNEL_DATA. RFC4254#section-5.2 corroborates.
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$packet = pack('CNNa*CNa*',
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NET_SSH2_MSG_CHANNEL_REQUEST, $this->server_channels[NET_SSH2_CHANNEL_EXEC], strlen('exec'), 'exec', 1, strlen($command), $command);
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if (!$this->_send_binary_packet($packet)) {
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return false;
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}
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@ -2808,6 +2825,8 @@ class Net_SSH2
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}
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$payload = $this->_get_binary_packet();
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}
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default:
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break;
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}
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// 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
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@ -2830,23 +2849,6 @@ class Net_SSH2
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return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
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}
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$payload = $this->_get_binary_packet();
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break;
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case NET_SSH2_MSG_CHANNEL_OPEN: // see http://tools.ietf.org/html/rfc4254#section-5.1
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$this->_string_shift($payload, 1);
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extract(unpack('Nlength', $this->_string_shift($payload, 4)));
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$this->errors[] = 'SSH_MSG_CHANNEL_OPEN: ' . utf8_decode($this->_string_shift($payload, $length));
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$this->_string_shift($payload, 4); // skip over client channel
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extract(unpack('Nserver_channel', $this->_string_shift($payload, 4)));
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$packet = pack('CN3a*Na*',
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NET_SSH2_MSG_REQUEST_FAILURE, $server_channel, NET_SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED, 0, '', 0, '');
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if (!$this->_send_binary_packet($packet)) {
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return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
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}
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$payload = $this->_get_binary_packet();
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break;
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case NET_SSH2_MSG_CHANNEL_WINDOW_ADJUST:
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@ -2983,8 +2985,16 @@ class Net_SSH2
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return '';
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}
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extract(unpack('Ctype/Nchannel', $this->_string_shift($response, 5)));
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extract(unpack('Ctype', $this->_string_shift($response, 1)));
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if ($type == NET_SSH2_MSG_CHANNEL_OPEN) {
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extract(unpack('Nlength', $this->_string_shift($response, 4)));
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} else {
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extract(unpack('Nchannel', $this->_string_shift($response, 4)));
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}
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// will not be setup yet on incoming channel open request
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if (isset($channel) && isset($this->channel_status[$channel]) && isset($this->window_size_server_to_client[$channel])) {
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$this->window_size_server_to_client[$channel]-= strlen($response);
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// resize the window, if appropriate
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@ -2997,7 +3007,7 @@ class Net_SSH2
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}
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switch ($this->channel_status[$channel]) {
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case NET_SSH2_MSG_CHANNEL_OPEN:
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case NET_SSH2_MSG_CHANNEL_OPEN:;
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switch ($type) {
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case NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
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extract(unpack('Nserver_channel', $this->_string_shift($response, 4)));
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@ -3026,10 +3036,46 @@ class Net_SSH2
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case NET_SSH2_MSG_CHANNEL_CLOSE:
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return $type == NET_SSH2_MSG_CHANNEL_CLOSE ? true : $this->_get_channel_packet($client_channel, $skip_extended);
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}
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}
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// ie. $this->channel_status[$channel] == NET_SSH2_MSG_CHANNEL_DATA
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switch ($type) {
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case NET_SSH2_MSG_CHANNEL_OPEN: // see http://tools.ietf.org/html/rfc4254#section-5.1
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$data = $this->_string_shift($response, $length);
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switch($data) {
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case 'auth-agent':
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case 'auth-agent@openssh.com':
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if (!isset($this->agent)) {
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break 2;
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}
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break;
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default:
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break 2;
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}
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$new_channel = NET_SSH2_CHANNEL_AGENT_FORWARD;
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extract(unpack('Nserver_channel', $this->_string_shift($response, 4)));
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extract(unpack('Nremote_window_size', $this->_string_shift($response, 4)));
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extract(unpack('Nremote_maximum_packet_size', $this->_string_shift($response, 4)));
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$this->packet_size_client_to_server[$new_channel] = $remote_window_size;
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$this->window_size_server_to_client[$new_channel] = $remote_maximum_packet_size;
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$this->window_size_client_to_server[$new_channel] = $this->window_size;
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$packet_size = 0x4000;
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$packet = pack('CN4',
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NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, $server_channel, $new_channel, $packet_size, $packet_size);
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$this->server_channels[$new_channel] = $server_channel;
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$this->channel_status[$new_channel] = NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION;
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if (!$this->_send_binary_packet($packet)) {
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return false;
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}
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break;
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case NET_SSH2_MSG_CHANNEL_DATA:
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/*
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if ($channel == NET_SSH2_CHANNEL_EXEC) {
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@ -3042,6 +3088,15 @@ class Net_SSH2
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*/
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extract(unpack('Nlength', $this->_string_shift($response, 4)));
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$data = $this->_string_shift($response, $length);
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if ($channel == NET_SSH2_CHANNEL_AGENT_FORWARD) {
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$agent_response = $this->agent->_forward_data($data);
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if (!is_bool($agent_response)) {
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$this->_send_channel_packet($channel, $agent_response);
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}
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break;
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}
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if ($client_channel == $channel) {
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return $data;
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}
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@ -1,4 +1,5 @@
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<?php
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/**
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* Pure-PHP ssh-agent client.
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*
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@ -225,6 +226,29 @@ class System_SSH_Agent
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*/
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var $fsock;
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/**
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* Did we request agent forwarding
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*
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* @access private
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*/
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var $request_forwarding;
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/**
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* Buffer for accumulating forwarded authentication
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* agent data arriving on SSH data channel destined
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* for agent unix socket
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*
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* @access private
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*/
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var $socket_buffer = '';
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/**
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* Tracking the number of bytes we are expecting
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* to arrive for the agent socket on the SSH data
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* channel
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*/
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var $expected_bytes = 0;
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/**
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* Default Constructor
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*
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@ -310,4 +334,133 @@ class System_SSH_Agent
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return $identities;
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}
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/**
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* Request the remote server to forward authentication requests to the local SSH agent
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*
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* @param Net_SSH2 $ssh
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* @return Boolean
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* @access public
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*/
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function startSSHForwarding($ssh)
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{
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if (!$this->request_forwarding) {
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$this->request_forwarding = true;
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$this->_request_forwarding($ssh);
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}
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}
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/**
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* Request the remote server to stop forwarding authentication requests to the local SSH agent
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*
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* @param Net_SSH2 $ssh
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* @return Boolean
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* @access public
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*/
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function stopSSHForwarding($ssh)
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{
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if ($this->request_forwarding) {
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$ssh->_close_channel(NET_SSH2_CHANNEL_AGENT_FORWARD);
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$this->request_forwarding = false;
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}
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}
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/**
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* The worker function to make a request to a remote server
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* asking it to forward authentication requests to the local SSH
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* agent
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*
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* @param Net_SSH2 $ssh
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* @return Boolean
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* @access private
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*/
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function _request_forwarding($ssh)
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{
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$ssh->window_size_server_to_client[NET_SSH2_CHANNEL_AGENT_REQUEST] = $ssh->window_size;
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$packet_size = 0x4000;
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$packet = pack('CNa*N3',
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NET_SSH2_MSG_CHANNEL_OPEN, strlen('session'), 'session', NET_SSH2_CHANNEL_AGENT_REQUEST, $ssh->window_size_server_to_client[NET_SSH2_CHANNEL_AGENT_REQUEST], $packet_size);
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$ssh->channel_status[NET_SSH2_CHANNEL_AGENT_REQUEST] = NET_SSH2_MSG_CHANNEL_OPEN;
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if (!$ssh->_send_binary_packet($packet)) {
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return false;
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}
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$response = $ssh->_get_channel_packet(NET_SSH2_CHANNEL_AGENT_REQUEST);
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if ($response === false) {
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return false;
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}
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$packet = pack('CNNa*C',
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NET_SSH2_MSG_CHANNEL_REQUEST, $ssh->server_channels[NET_SSH2_CHANNEL_AGENT_REQUEST], strlen('auth-agent-req@openssh.com'), 'auth-agent-req@openssh.com', 1);
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$ssh->channel_status[NET_SSH2_CHANNEL_AGENT_REQUEST] = NET_SSH2_MSG_CHANNEL_REQUEST;
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if (!$ssh->_send_binary_packet($packet)) {
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return false;
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}
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$response = $ssh->_get_channel_packet(NET_SSH2_CHANNEL_AGENT_REQUEST);
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if ($response === false) {
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return false;
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}
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return true;
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}
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/**
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* On Successful Login
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*
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* This method should be called upon successful SSH login if you
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* wish to give the SSH Agent an opportunity to take further
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* action. i.e. request agent forwarding
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*
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* @param Net_SSH2 $ssh
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* @access private
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*/
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function _on_login_success($ssh)
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{
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if ($this->request_forwarding) {
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$this->_request_forwarding($ssh);
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}
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}
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/**
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* Forward data to SSH Agent and return data reply
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*
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* @param String $data
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* @return data from SSH Agent
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* @access private
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*/
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function _forward_data($data)
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{
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if ($this->expected_bytes > 0) {
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$this->socket_buffer .= $data;
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$this->expected_bytes -= strlen($data);
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} else {
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$agent_data_bytes = current(unpack('N', $data));
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$current_data_bytes = strlen($data);
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$this->socket_buffer = $data;
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if ($current_data_bytes != $agent_data_bytes + 4) {
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$this->expected_bytes = ($agent_data_bytes + 4) - $current_data_bytes;
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return false;
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}
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}
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if (strlen($this->socket_buffer) != fwrite($this->fsock, $this->socket_buffer)) {
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user_error('Connection closed attempting to forward data to SSH agent');
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}
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$this->socket_buffer = '';
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$this->expected_bytes = 0;
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$agent_reply_bytes = current(unpack('N', fread($this->fsock, 4)));
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$agent_reply_data = fread($this->fsock, $agent_reply_bytes);
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$agent_reply_data = current(unpack('a*', $agent_reply_data));
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return pack('Na*', $agent_reply_bytes, $agent_reply_data);
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}
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}
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@ -27,5 +27,27 @@ class Functional_Net_SSH2AgentTest extends PhpseclibFunctionalTestCase
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$ssh->login($this->getEnv('SSH_USERNAME'), $agent),
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'SSH2 login using Agent failed.'
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);
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return array('ssh' => $ssh, 'ssh-agent' => $agent);
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}
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/**
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* @depends testAgentLogin
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*/
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public function testAgentForward($args)
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{
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$ssh = $args['ssh'];
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$agent = $args['ssh-agent'];
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$hostname = $this->getEnv('SSH_HOSTNAME');
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$username = $this->getEnv('SSH_USERNAME');
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$this->assertEquals($username, trim($ssh->exec('whoami')));
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$agent->startSSHForwarding($ssh);
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$this->assertEquals($username, trim($ssh->exec("ssh " . $username . "@" . $hostname . ' \'whoami\'')));
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$agent->stopSSHForwarding($ssh);
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return $args;
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}
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}
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@ -28,4 +28,6 @@ ssh-add "$HOME/.ssh/id_rsa"
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# Allow the private key of the travis user to log in as phpseclib user
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sudo mkdir -p "/home/$USERNAME/.ssh/"
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sudo cp "$HOME/.ssh/id_rsa.pub" "/home/$USERNAME/.ssh/authorized_keys"
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sudo ssh-keyscan -t rsa localhost > "/tmp/known_hosts"
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sudo cp "/tmp/known_hosts" "/home/$USERNAME/.ssh/known_hosts"
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sudo chown "$USERNAME:$USERNAME" "/home/$USERNAME/.ssh/" -R
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