Implement SSH Agent Forwarding Feature

src/Server/Builder.php

@@ -81,6 +81,17 @@ class Builder
         return $this;
     }
     
+    /**
+     * Using forward agent to authentication
+     * 
+     * @return \Deployer\Server\Builder
+     */
+    public function forwardAgent()
+    {
+        $this->config->setAuthenticationMethod(Configuration::AUTH_BY_AGENT);
+        return $this;
+    }
+
     /**
      * @param string $name
      * @param array|int|string $value

src/Server/Configuration.php

@@ -17,6 +17,8 @@ class Configuration
 
     const AUTH_BY_PEM_FILE = 3;
     
+    const AUTH_BY_AGENT = 4;
+
     /**
      * Type of authentication.
      * @var int

src/Server/Remote/PhpSecLib.php

@@ -11,6 +11,7 @@ use Deployer\Server\Configuration;
 use Deployer\Server\ServerInterface;
 use phpseclib\Crypt\RSA;
 use phpseclib\Net\SFTP;
+use \phpseclib\System\SSH\Agent;
 
 class PhpSecLib implements ServerInterface
 {
@@ -71,6 +72,13 @@ class PhpSecLib implements ServerInterface
 
                 break;
 
+            case Configuration::AUTH_BY_AGENT:
+                
+                $key = new Agent();
+                $this->sftp->login($serverConfig->getUser(), $key);
+                
+                break;
+            
             default:
                 throw new \RuntimeException('You need to specify authentication method.');
         }

src/Server/Remote/SshExtension.php

@@ -82,6 +82,10 @@ class SshExtension implements ServerInterface
 
                 throw new \RuntimeException('If you want to use pem file, switch to using PhpSecLib.');
                 
+            case Configuration::AUTH_BY_AGENT:
+
+                throw new \RuntimeException('If you want to use forward agent function, switch to using PhpSecLib.');
+
             default:
                 throw new \RuntimeException('You need to specify authentication method.');
         }

test/src/Server/BuilderTest.php

@@ -101,4 +101,17 @@ class BuilderTest extends \PHPUnit_Framework_TestCase
         $b = new Builder($config, $env);
         $b->env('name', 'value');
     }
+    
+    public function testForwardAgent()
+    {
+        $config = $this->getMockBuilder('Deployer\Server\Configuration')->disableOriginalConstructor()->getMock();
+        $config->expects($this->once())
+            ->method('setAuthenticationMethod')
+            ->with(Configuration::AUTH_BY_AGENT)
+            ->will($this->returnSelf());
+        $env = $this->getMock('Deployer\Server\Environment');
+
+        $b = new Builder($config, $env);
+        $b->forwardAgent();
+    }
 }