Introduce buffering to send channel packet for capability to resume across timeout

phpseclib/Net/SSH2.php

@@ -626,7 +626,7 @@ class SSH2
     protected $server_channels = [];
 
     /**
-     * Channel Buffers
+     * Channel Read Buffers
      *
      * If a client requests a packet from one channel but receives two packets from another those packets should
      * be placed in a buffer
@@ -637,6 +637,17 @@ class SSH2
      */
     private $channel_buffers = [];
 
+    /**
+     * Channel Write Buffers
+     *
+     * If a client sends a packet and receives a timeout error mid-transmission, buffer the data written so it
+     * can be de-duplicated upon resuming write
+     *
+     * @see self::send_channel_packet()
+     * @var array
+     */
+    private $channel_buffers_write = [];
+
     /**
      * Channel Status
      *
@@ -3446,6 +3457,8 @@ class SSH2
         $this->get_seq_no = $this->send_seq_no = 0;
         $this->channel_status = [];
         $this->channel_id_last_interactive = 0;
+        $this->channel_buffers = [];
+        $this->channel_buffers_write = [];
     }
 
     /**
@@ -4480,6 +4493,14 @@ class SSH2
      */
     protected function send_channel_packet($client_channel, $data)
     {
+        if (isset($this->channel_buffers_write[$client_channel])
+            && strpos($data, $this->channel_buffers_write[$client_channel]) === 0
+        ) {
+            // if buffer holds identical initial data content, resume send from the unmatched data portion
+            $data = substr($data, strlen($this->channel_buffers_write[$client_channel]));
+        } else {
+            $this->channel_buffers_write[$client_channel] = '';
+        }
         while (strlen($data)) {
             if (!$this->window_size_client_to_server[$client_channel]) {
                 // using an invalid channel will let the buffers be built up for the valid channels
@@ -4487,7 +4508,7 @@ class SSH2
                 if ($this->isTimeout()) {
                     throw new TimeoutException('Timed out waiting for server');
                 } elseif (!$this->window_size_client_to_server[$client_channel]) {
-                    throw new \RuntimeException('Client to server window was not adjusted');
+                    throw new \RuntimeException('Data window was not adjusted');
                 }
             }
 
@@ -4509,7 +4530,9 @@ class SSH2
             );
             $this->window_size_client_to_server[$client_channel] -= strlen($temp);
             $this->send_binary_packet($packet);
+            $this->channel_buffers_write[$client_channel] .= $temp;
         }
+        unset($this->channel_buffers_write[$client_channel]);
     }
 
     /**

tests/Unit/Net/SSH2UnitTest.php

@@ -8,8 +8,11 @@
 
 namespace phpseclib3\Tests\Unit\Net;
 
+use phpseclib3\Common\Functions\Strings;
 use phpseclib3\Exception\InsufficientSetupException;
+use phpseclib3\Exception\TimeoutException;
 use phpseclib3\Net\SSH2;
+use phpseclib3\Net\SSH2\MessageType;
 use phpseclib3\Tests\PhpseclibTestCase;
 
 class SSH2UnitTest extends PhpseclibTestCase
@@ -271,6 +274,116 @@ class SSH2UnitTest extends PhpseclibTestCase
         $this->assertEquals([0, 0], self::callFunc($ssh, 'get_stream_timeout'));
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
+    public function testSendChannelPacketNoBufferedData()
+    {
+        $ssh = $this->getMockBuilder('phpseclib3\Net\SSH2')
+            ->disableOriginalConstructor()
+            ->setMethods(['get_channel_packet', 'send_binary_packet'])
+            ->getMock();
+        $ssh->expects($this->once())
+            ->method('get_channel_packet')
+            ->with(-1)
+            ->willReturnCallback(function () use ($ssh) {
+                self::setVar($ssh, 'window_size_client_to_server', [1 => 0x7FFFFFFF]);
+            });
+        $ssh->expects($this->once())
+            ->method('send_binary_packet')
+            ->with(Strings::packSSH2('CNs', MessageType::CHANNEL_DATA, 1, 'hello world'));
+        self::setVar($ssh, 'server_channels', [1 => 1]);
+        self::setVar($ssh, 'packet_size_client_to_server', [1 => 0x7FFFFFFF]);
+        self::setVar($ssh, 'window_size_client_to_server', [1 => 0]);
+        self::setVar($ssh, 'window_size_server_to_client', [1 => 0x7FFFFFFF]);
+
+        self::callFunc($ssh, 'send_channel_packet', [1, 'hello world']);
+        $this->assertEmpty(self::getVar($ssh, 'channel_buffers_write'));
+    }
+
+    /**
+     * @requires PHPUnit < 10
+     */
+    public function testSendChannelPacketBufferedData()
+    {
+        $ssh = $this->getMockBuilder('phpseclib3\Net\SSH2')
+            ->disableOriginalConstructor()
+            ->setMethods(['get_channel_packet', 'send_binary_packet'])
+            ->getMock();
+        $ssh->expects($this->once())
+            ->method('get_channel_packet')
+            ->with(-1)
+            ->willReturnCallback(function () use ($ssh) {
+                self::setVar($ssh, 'window_size_client_to_server', [1 => 0x7FFFFFFF]);
+            });
+        $ssh->expects($this->once())
+            ->method('send_binary_packet')
+            ->with(Strings::packSSH2('CNs', MessageType::CHANNEL_DATA, 1, ' world'));
+        self::setVar($ssh, 'channel_buffers_write', [1 => 'hello']);
+        self::setVar($ssh, 'server_channels', [1 => 1]);
+        self::setVar($ssh, 'packet_size_client_to_server', [1 => 0x7FFFFFFF]);
+        self::setVar($ssh, 'window_size_client_to_server', [1 => 0]);
+        self::setVar($ssh, 'window_size_server_to_client', [1 => 0x7FFFFFFF]);
+
+        self::callFunc($ssh, 'send_channel_packet', [1, 'hello world']);
+        $this->assertEmpty(self::getVar($ssh, 'channel_buffers_write'));
+    }
+
+    /**
+     * @requires PHPUnit < 10
+     */
+    public function testSendChannelPacketTimeout()
+    {
+        $this->expectException(TimeoutException::class);
+        $this->expectExceptionMessage('Timed out waiting for server');
+
+        $ssh = $this->getMockBuilder('phpseclib3\Net\SSH2')
+            ->disableOriginalConstructor()
+            ->setMethods(['get_channel_packet', 'send_binary_packet'])
+            ->getMock();
+        $ssh->expects($this->once())
+            ->method('get_channel_packet')
+            ->with(-1)
+            ->willReturnCallback(function () use ($ssh) {
+                self::setVar($ssh, 'is_timeout', true);
+            });
+        $ssh->expects($this->once())
+            ->method('send_binary_packet')
+            ->with(Strings::packSSH2('CNs', MessageType::CHANNEL_DATA, 1, 'hello'));
+        self::setVar($ssh, 'server_channels', [1 => 1]);
+        self::setVar($ssh, 'packet_size_client_to_server', [1 => 0x7FFFFFFF]);
+        self::setVar($ssh, 'window_size_client_to_server', [1 => 5]);
+        self::setVar($ssh, 'window_size_server_to_client', [1 => 0x7FFFFFFF]);
+
+        self::callFunc($ssh, 'send_channel_packet', [1, 'hello world']);
+        $this->assertEquals([1 => 'hello'], self::getVar($ssh, 'channel_buffers_write'));
+    }
+
+    /**
+     * @requires PHPUnit < 10
+     */
+    public function testSendChannelPacketNoWindowAdjustment()
+    {
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('Data window was not adjusted');
+
+        $ssh = $this->getMockBuilder('phpseclib3\Net\SSH2')
+            ->disableOriginalConstructor()
+            ->setMethods(['get_channel_packet', 'send_binary_packet'])
+            ->getMock();
+        $ssh->expects($this->once())
+            ->method('get_channel_packet')
+            ->with(-1);
+        $ssh->expects($this->never())
+            ->method('send_binary_packet');
+        self::setVar($ssh, 'server_channels', [1 => 1]);
+        self::setVar($ssh, 'packet_size_client_to_server', [1 => 0x7FFFFFFF]);
+        self::setVar($ssh, 'window_size_client_to_server', [1 => 0]);
+        self::setVar($ssh, 'window_size_server_to_client', [1 => 0x7FFFFFFF]);
+
+        self::callFunc($ssh, 'send_channel_packet', [1, 'hello world']);
+    }
+
     /**
      * @return \phpseclib3\Net\SSH2
      */