Asymmetric decryption

lib/openpgp.php

@@ -568,7 +568,37 @@ class OpenPGP_Packet {
  * @see http://tools.ietf.org/html/rfc4880#section-5.1
  */
 class OpenPGP_AsymmetricSessionKeyPacket extends OpenPGP_Packet {
-  // TODO
+  public $version, $keyid, $key_algorithm, $encrypted_data;
+
+  function read() {
+    switch($this->version = ord($this->read_byte())) {
+      case 3:
+        $rawkeyid = $this->read_bytes(8);
+        $this->keyid = '';
+        for($i = 0; $i < strlen($rawkeyid); $i++) { // Store KeyID in Hex
+          $this->keyid .= sprintf('%02X',ord($rawkeyid{$i}));
+        }
+
+        $this->key_algorithm = ord($this->read_byte());
+
+        $this->encrypted_data = $this->input;
+        break;
+      default:
+        throw new Exception("Unsupported AsymmetricSessionKeyPacket version: " . $this->version);
+    }
+  }
+
+  function body() {
+    $bytes = ord($this->version);
+
+    for($i = 0; $i < strlen($this->keyid); $i += 2) {
+      $bytes .= chr(hexdec($this->keyid{$i}.$this->keyid{$i+1}));
+    }
+
+    $bytes .= chr($this->key_algorithm);
+    $bytes .= $this->encrypted_data;
+    return $bytes;
+  }
 }
 
 /**

lib/openpgp_crypt_aes_tripledes.php

@@ -6,21 +6,35 @@ require_once 'Crypt/TripleDES.php';
 
 class OpenPGP_Crypt_AES_TripleDES {
   public static function decryptSymmetric($pass, $m) {
+    $epacket = self::getEncryptedData($m);
+
     foreach($m as $p) {
       if($p instanceof OpenPGP_SymmetricSessionKeyPacket) {
+        if(strlen($p->encrypted_data) > 0) {
           list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($p->symmetric_algorithm);
           if(!$cipher) continue;
           $cipher->setKey($p->s2k->make_key($pass, $key_bytes));
 
-        if(strlen($p->encrypted_data) > 0) {
           $padAmount = $key_block_bytes - (strlen($p->encrypted_data) % $key_block_bytes);
           $data = substr($cipher->decrypt($p->encrypted_data . str_repeat("\0", $padAmount)), 0, strlen($p->encrypted_data));
-          list($cipher, $key_bytes, $key_block_bytes) = self::getCipher(ord($data{0}));
-          if(!$cipher) continue;
-          $cipher->setKey(substr($data, 1));
+          $decrypted = self::decryptPacket($epacket, ord($data{0}), substr($data, 1));
+        } else {
+          list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($p->symmetric_algorithm);
+          $decrypted = self::decryptPacket($epacket, $p->symmetric_algorithm, $p->s2k->make_key($pass, $key_bytes));
         }
 
-        $epacket = self::getEncryptedData($m);
+        if($decrypted) return $decrypted;
+      }
+    }
+
+    return NULL; /* If we get here, we failed */
+  }
+
+  public static function decryptPacket($epacket, $symmetric_algorithm, $key) {
+    list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($symmetric_algorithm);
+    if(!$cipher) return NULL;
+    $cipher->setKey($key);
+
     $padAmount = $key_block_bytes - (strlen($epacket->data) % $key_block_bytes);
 
     if($epacket instanceof OpenPGP_IntegrityProtectedDataPacket) {
@@ -49,10 +63,8 @@ class OpenPGP_Crypt_AES_TripleDES {
        } catch (Exception $ex) { $msg = NULL; }
        if($msg) return $msg; /* Otherwise keep trying */
     }
-      }
-    }
 
-    return NULL; /* If we get here, we failed */
+    return NULL; /* Failed */
   }
 
   public static function getCipher($algo) {

lib/openpgp_crypt_rsa.php

@@ -12,6 +12,9 @@
 // From http://phpseclib.sourceforge.net/
 require 'Crypt/RSA.php';
 
+require_once dirname(__FILE__).'/openpgp.php';
+@include_once dirname(__FILE__).'/openpgp_cryph_aes_tripledes.php'; /* For encrypt/decrypt */
+
 class OpenPGP_Crypt_RSA {
   protected $key, $message;
 
@@ -157,6 +160,64 @@ class OpenPGP_Crypt_RSA {
     return $packet;
   }
 
+  function decrypt($packet) {
+    if(!is_object($packet)) $packet = OpenPGP_Message::parse($packet);
+
+    if($packet instanceof OpenPGP_SecretKeyPacket || $packet instanceof Crypt_RSA
+       || ($packet instanceof ArrayAccess && $packet[0] instanceof OpenPGP_SecretKeyPacket)) {
+      $keys = $packet;
+      $message = $this->message;
+    } else {
+      $keys = $this->key;
+      $message = $packet;
+    }
+
+    if(!$keys || !$message) return NULL; // Missing some data
+
+    if(!($keys instanceof Crypt_RSA)) {
+      $keys = new self($keys);
+    }
+
+    foreach($message as $p) {
+      if($p instanceof OpenPGP_AsymmetricSessionKeyPacket) {
+        if($keys instanceof Crypt_RSA) {
+          $sk = self::try_decrypt_session($keys, $p->encyrpted_data);
+        } else if(strlen(str_replace('0', '', $p->keyid)) < 1) {
+          foreach($keys->key as $k) {
+            $sk = self::try_decrypt_session(self::convert_private_key($k), $p->encyrpted_data);
+            if($sk) break;
+          }
+        } else {
+          $key = $keys->private_key($p->keyid);
+          $sk = self::try_decrypt_session($key, substr($p->encrypted_data, 2));
+        }
+
+        if(!$sk) continue;
+
+        $r = OpenPGP_Crypt_AES_TripleDES::decryptPacket(OpenPGP_Crypt_AES_TripleDES::getEncryptedData($message), $sk[0], $sk[1]);
+        if($r) return $r;
+      }
+    }
+
+    return NULL; /* Failed */
+  }
+
+  static function try_decrypt_session($key, $edata) {
+    $key->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
+    $data = $key->decrypt($edata);
+    $sk = substr($data, 1, strlen($data)-3);
+    $chk = unpack('n', substr($data, -2));
+    $chk = reset($chk);
+
+    $sk_chk = 0;
+    for($i = 0; $i < strlen($sk); $i++) {
+      $sk_chk = ($sk_chk + ord($sk{$i})) % 65536;
+    }
+
+    if($sk_chk != $chk) return NULL;
+    return array(ord($data{0}), $sk);
+  }
+
   static function crypt_rsa_key($mod, $exp, $hash='SHA256') {
     $rsa = new Crypt_RSA();
     $rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1);

tests/phpseclib_suite.php

@@ -91,4 +91,16 @@ class Decryption extends PHPUnit_Framework_TestCase {
   public function testDecryptNoMDC() {
     $this->oneSymmetric("hello", "PGP\n", "symmetric-no-mdc.gpg");
   }
+
+  public function testDecryptAsymmetric() {
+    $m = OpenPGP_Message::parse(file_get_contents(dirname(__FILE__) . '/data/hello.gpg'));
+    $key = OpenPGP_Message::parse(file_get_contents(dirname(__FILE__) . '/data/helloKey.gpg'));
+    $m2 = (new OpenPGP_Crypt_RSA($key))->decrypt($m);
+    while($m2[0] instanceof OpenPGP_CompressedDataPacket) $m2 = $m2[0]->data;
+    foreach($m2 as $p) {
+      if($p instanceof OpenPGP_LiteralDataPacket) {
+        $this->assertEquals($p->data, "hello\n");
+      }
+    }
+  }
 }