diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 999e4c1a..5376a104 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -1769,8 +1769,13 @@ class Net_SSH2
         }
 
         // although PHP5's get_class() preserves the case, PHP4's does not
-        if (is_object($password) && strtolower(get_class($password)) == 'crypt_rsa') {
-            return $this->_privatekey_login($username, $password);
+        if (is_object($password)) {
+            switch (strtolower(get_class($password))) {
+                case 'crypt_rsa':
+                    return $this->_privatekey_login($username, $password);
+                case 'system_ssh_agent':
+                    return $this->_ssh_agent_login($username, $password);
+            }
         }
 
         if (is_array($password)) {
@@ -2007,6 +2012,26 @@ class Net_SSH2
         return false;
     }
 
+    /**
+     * Login with an ssh-agent provided key
+     *
+     * @param String $username
+     * @param System_SSH_Agent $agent
+     * @return Boolean
+     * @access private
+     */
+    function _ssh_agent_login($username, $agent)
+    {
+        $keys = $agent->requestIdentities();
+        foreach ($keys as $key) {
+            if ($this->_privatekey_login($username, $key)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * Login with an RSA private key
      *
diff --git a/phpseclib/System/SSH_Agent.php b/phpseclib/System/SSH_Agent.php
new file mode 100644
index 00000000..32392a55
--- /dev/null
+++ b/phpseclib/System/SSH_Agent.php
@@ -0,0 +1,324 @@
+<?php
+/**
+ * Pure-PHP ssh-agent client.
+ *
+ * PHP versions 4 and 5
+ *
+ * Here are some examples of how to use this library:
+ * <code>
+ * <?php
+ *    include('System/SSH_Agent.php');
+ *    include('Net/SSH2.php');
+ *
+ *    $agent = new System_SSH_Agent();
+ *
+ *    $ssh = new Net_SSH2('www.domain.tld');
+ *    if (!$ssh->login('username', $agent)) {
+ *        exit('Login Failed');
+ *    }
+ *
+ *    echo $ssh->exec('pwd');
+ *    echo $ssh->exec('ls -la');
+ * ?>
+ * </code>
+ *
+ * LICENSE: Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @category  System
+ * @package   System_SSH_Agent
+ * @author    Jim Wigginton <terrafrost@php.net>
+ * @copyright MMXIV Jim Wigginton
+ * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
+ * @link      http://phpseclib.sourceforge.net
+ * @internal  See http://api.libssh.org/rfc/PROTOCOL.agent
+ */
+
+/**#@+
+ * Message numbers
+ *
+ * @access private
+ */
+// to request SSH1 keys you have to use SSH_AGENTC_REQUEST_RSA_IDENTITIES (1)
+define('SYSTEM_SSH_AGENTC_REQUEST_IDENTITIES', 11);
+// this is the SSH2 response; the SSH1 response is SSH_AGENT_RSA_IDENTITIES_ANSWER (2).
+define('SYSTEM_SSH_AGENT_IDENTITIES_ANSWER', 12);
+define('SYSTEM_SSH_AGENT_FAILURE', 5);
+// the SSH1 request is SSH_AGENTC_RSA_CHALLENGE (3)
+define('SYSTEM_SSH_AGENTC_SIGN_REQUEST', 13);
+// the SSH1 response is SSH_AGENT_RSA_RESPONSE (4)
+define('SYSTEM_SSH_AGENT_SIGN_RESPONSE', 14);
+/**#@-*/
+
+/**
+ * Pure-PHP ssh-agent client identity object
+ *
+ * Instantiation should only be performed by System_SSH_Agent class.
+ * This could be thought of as implementing an interface that Crypt_RSA
+ * implements. ie. maybe a Net_SSH_Auth_PublicKey interface or something.
+ * The methods in this interface would be getPublicKey, setSignatureMode
+ * and sign since those are the methods phpseclib looks for to perform
+ * public key authentication.
+ *
+ * @package System_SSH_Agent
+ * @author  Jim Wigginton <terrafrost@php.net>
+ * @version 0.1.0
+ * @access  internal
+ */
+class System_SSH_Agent_Identity
+{
+    /**
+     * Key Object
+     *
+     * @var Crypt_RSA
+     * @access private
+     * @see System_SSH_Agent_Identity::getPublicKey()
+     */
+    var $key;
+
+    /**
+     * Key Blob
+     *
+     * @var String
+     * @access private
+     * @see System_SSH_Agent_Identity::sign()
+     */
+    var $key_blob;
+
+    /**
+     * Socket Resource
+     *
+     * @var Resource
+     * @access private
+     * @see System_SSH_Agent_Identity::sign()
+     */
+    var $fsock;
+
+    /**
+     * Default Constructor.
+     *
+     * @param Resource $fsock
+     * @return System_SSH_Agent_Identity
+     * @access private
+     */
+    function System_SSH_Agent_Identity($fsock)
+    {
+        $this->fsock = $fsock;
+    }
+
+    /**
+     * Set Public Key
+     *
+     * Called by System_SSH_Agent::requestIdentities()
+     *
+     * @param Crypt_RSA $key
+     * @access private
+     */
+    function setPublicKey($key)
+    {
+        $this->key = $key;
+        $this->key->setPublicKey();
+    }
+
+    /**
+     * Set Public Key
+     *
+     * Called by System_SSH_Agent::requestIdentities(). The key blob could be extracted from $this->key
+     * but this saves a small amount of computation.
+     *
+     * @param String $key_blob
+     * @access private
+     */
+    function setPublicKeyBlob($key_blob)
+    {
+        $this->key_blob = $key_blob;
+    }
+
+    /**
+     * Get Public Key
+     *
+     * Wrapper for $this->key->getPublicKey()
+     *
+     * @param Integer $format optional
+     * @return Mixed
+     * @access public
+     */
+    function getPublicKey($format = null)
+    {
+        return !isset($format) ? $this->key->getPublicKey() : $this->key->getPublicKey($format);
+    }
+
+    /**
+     * Set Signature Mode
+     *
+     * Doesn't do anything as ssh-agent doesn't let you pick and choose the signature mode. ie.
+     * ssh-agent's only supported mode is CRYPT_RSA_SIGNATURE_PKCS1
+     *
+     * @param Integer $mode
+     * @access public
+     */
+    function setSignatureMode($mode)
+    {
+    }
+
+    /**
+     * Create a signature
+     *
+     * See "2.6.2 Protocol 2 private key signature request"
+     *
+     * @param String $message
+     * @return String
+     * @access public
+     */
+    function sign($message)
+    {
+        // the last parameter (currently 0) is for flags and ssh-agent only defines one flag (for ssh-dss): SSH_AGENT_OLD_SIGNATURE
+        $packet = pack('CNa*Na*N', SYSTEM_SSH_AGENTC_SIGN_REQUEST, strlen($this->key_blob), $this->key_blob, strlen($message), $message, 0);
+        $packet = pack('Na*', strlen($packet), $packet);
+        if (strlen($packet) != fputs($this->fsock, $packet)) {
+            user_error('Connection closed during signing');
+        }
+
+        $length = current(unpack('N', fread($this->fsock, 4)));
+        $type = ord(fread($this->fsock, 1));
+        if ($type != SYSTEM_SSH_AGENT_SIGN_RESPONSE) {
+            user_error('Unable to retreive signature');
+        }
+
+        $signature_blob = fread($this->fsock, $length - 1);
+        // the only other signature format defined - ssh-dss - is the same length as ssh-rsa
+        // the + 12 is for the other various SSH added length fields
+        return substr($signature_blob, strlen('ssh-rsa') + 12);
+    }
+}
+
+/**
+ * Pure-PHP ssh-agent client identity factory
+ *
+ * requestIdentities() method pumps out System_SSH_Agent_Identity objects
+ *
+ * @package System_SSH_Agent
+ * @author  Jim Wigginton <terrafrost@php.net>
+ * @version 0.1.0
+ * @access  internal
+ */
+class System_SSH_Agent
+{
+    /**
+     * Socket Resource
+     *
+     * @var Resource
+     * @access private
+     */
+    var $fsock;
+
+    /**
+     * Is Connected?
+     *
+     * @var Boolean
+     * @access private
+     */
+    var $is_connected = false;
+
+    /**
+     * Default Constructor
+     *
+     * @return System_SSH_Agent
+     * @access public
+     */
+    function System_SSH_Agent()
+    {
+        switch (true) {
+            case isset($_SERVER['SSH_AUTH_SOCK']):
+                $address = $_SERVER['SSH_AUTH_SOCK'];
+                break;
+            case isset($_ENV['SSH_AUTH_SOCK']):
+                $address = $_ENV['SSH_AUTH_SOCK'];
+                break;
+            default:
+                user_error('SSH_AUTH_SOCK not found', E_USER_NOTICE);
+                return false;
+        }
+
+        $this->fsock = fsockopen('unix://' . $address, 0, $errno, $errstr);
+        if (!$this->fsock) {
+            user_error("Unable to connect to ssh-agent (Error $errno: $errstr)");
+        }
+        $this->is_connected = true;
+    }
+
+    /**
+     * Request Identities
+     *
+     * See "2.5.2 Requesting a list of protocol 2 keys"
+     * Returns an array containing zero or more System_SSH_Agent_Identity objects
+     *
+     * @return Array
+     * @access public
+     */
+    function requestIdentities()
+    {
+        if (!$this->is_connected) {
+            return array();
+        }
+
+        $packet = pack('NC', 1, SYSTEM_SSH_AGENTC_REQUEST_IDENTITIES);
+        if (strlen($packet) != fputs($this->fsock, $packet)) {
+            user_error('Connection closed while requesting identities');
+        }
+
+        $length = current(unpack('N', fread($this->fsock, 4)));
+        $type = ord(fread($this->fsock, 1));
+        if ($type != SYSTEM_SSH_AGENT_IDENTITIES_ANSWER) {
+            user_error('Unable to request identities');
+        }
+
+        $identities = array();
+        $keyCount = current(unpack('N', fread($this->fsock, 4)));
+        for ($i = 0; $i < $keyCount; $i++) {
+            $length = current(unpack('N', fread($this->fsock, 4)));
+            $key_blob = fread($this->fsock, $length);
+            $length = current(unpack('N', fread($this->fsock, 4)));
+            $key_comment = fread($this->fsock, $length);
+            $length = current(unpack('N', substr($key_blob, 0, 4)));
+            $key_type = substr($key_blob, 4, $length);
+            switch ($key_type) {
+                case 'ssh-rsa':
+                    if (!class_exists('Crypt_RSA')) {
+                        include_once 'Crypt/RSA.php';
+                    }
+                    $key = new Crypt_RSA();
+                    $key->loadKey('ssh-rsa ' . base64_encode($key_blob) . ' ' . $key_comment);
+                    break;
+                case 'ssh-dss':
+                    // not currently supported
+                    break;
+            }
+            // resources are passed by reference by default
+            if (isset($key)) {
+                $identity = new System_SSH_Agent_Identity($this->fsock);
+                $identity->setPublicKey($key);
+                $identity->setPublicKeyBlob($key_blob);
+                $identities[] = $identity;
+                unset($key);
+            }
+        }
+
+        return $identities;
+    }
+}