openpgp-php/lib/openpgp_crypt_rsa.php

<?php
// This is free and unencumbered software released into the public domain.
/**
 * OpenPGP_Crypt_RSA.php is a wrapper for using the classes from OpenPGP.php with Crypt_RSA
 *
 * @package OpenPGP
 * @version 0.0.1
 * @author  Stephen Paul Weber <singpolyma@singpolyma.net>
 * @link    http://github.com/singpolyma/openpgp-php
 */

// From http://phpseclib.sourceforge.net/
require 'Crypt/RSA.php';

require_once dirname(__FILE__).'/openpgp.php';
@include_once dirname(__FILE__).'/openpgp_crypt_symmetric.php'; /* For encrypt/decrypt */

class OpenPGP_Crypt_RSA {
  protected $key, $message;

  // Construct a wrapper object from a key or a message packet
  function __construct($packet) {
    if(!is_object($packet)) $packet = OpenPGP_Message::parse($packet);
    if($packet instanceof OpenPGP_PublicKeyPacket || $packet[0] instanceof OpenPGP_PublicKeyPacket) { // If it's a key (other keys are subclasses of this one)
      $this->key = $packet;
    } else {
      $this->message = $packet;
    }
  }

  function key($keyid=NULL) {
    if(!$this->key) return NULL; // No key
    if($this->key instanceof OpenPGP_Message) {
      foreach($this->key as $p) {
        if($p instanceof OpenPGP_PublicKeyPacket) {
          if(!$keyid || strtoupper(substr($p->fingerprint, strlen($keyid)*-1)) == strtoupper($keyid)) return $p;
        }
      }
    }
    return $this->key;
  }

  // Get Crypt_RSA for the public key
  function public_key($keyid=NULL) {
    return self::convert_public_key($this->key($keyid));
  }

  // Get Crypt_RSA for the private key
  function private_key($keyid=NULL) {
    return self::convert_private_key($this->key($keyid));
  }

  // Pass a message to verify with this key, or a key (OpenPGP or Crypt_RSA) to check this message with
  // Second optional parameter to specify which signature to verify (if there is more than one)
  function verify($packet) {
    $self = $this; // For old PHP
    if(!is_object($packet)) $packet = OpenPGP_Message::parse($packet);
    if(!$this->message) {
      $m = $packet;
      $verifier = function($m, $s) use($self) {
        $key = $self->public_key($s->issuer());
        if(!$key) return false;
        $key->setHash(strtolower($s->hash_algorithm_name()));
        return $key->verify($m, reset($s->data));
      };
    } else {
      if(!($packet instanceof Crypt_RSA)) {
        $packet = new self($packet);
      }

      $m = $this->message;
      $verifier = function($m, $s) use($self, $packet) {
        if(!($packet instanceof Crypt_RSA)) {
          $key = $packet->public_key($s->issuer());
        }
        if(!$key) return false;
        $key->setHash(strtolower($s->hash_algorithm_name()));
        return $key->verify($m, reset($s->data));
      };
    }

    return $m->verified_signatures(array('RSA' => array(
      'MD5'    => $verifier,
      'SHA1'   => $verifier,
      'SHA224' => $verifier,
      'SHA256' => $verifier,
      'SHA384' => $verifier,
      'SHA512' => $verifier
    )));
  }

  // Pass a message to sign with this key, or a secret key to sign this message with
  // Second parameter is hash algorithm to use (default SHA256)
  // Third parameter is the 16-digit key ID to use... defaults to the key id in the key packet
  function sign($packet, $hash='SHA256', $keyid=NULL) {
    if(!is_object($packet)) {
      if($this->key) {
        $packet = new OpenPGP_LiteralDataPacket($packet);
      } else {
        $packet = OpenPGP_Message::parse($packet);
      }
    }

    if($packet instanceof OpenPGP_SecretKeyPacket || $packet instanceof Crypt_RSA
       || ($packet instanceof ArrayAccess && $packet[0] instanceof OpenPGP_SecretKeyPacket)) {
      $key = $packet;
      $message = $this->message;
    } else {
      $key = $this->key;
      $message = $packet;
    }

    if(!$key || !$message) return NULL; // Missing some data

    if($message instanceof OpenPGP_Message) {
      $sign = $message->signatures();
      $message = $sign[0][0];
    }

    if(!($key instanceof Crypt_RSA)) {
      $key = new self($key);
      if(!$keyid) $keyid = substr($key->key()->fingerprint, -16, 16);
      $key = $key->private_key($keyid);
    }
    $key->setHash(strtolower($hash));

    $sig = new OpenPGP_SignaturePacket($message, 'RSA', strtoupper($hash));
    $sig->hashed_subpackets[] = new OpenPGP_SignaturePacket_IssuerPacket($keyid);
    $sig->sign_data(array('RSA' => array($hash => function($data) use($key) {return array($key->sign($data));})));

    return new OpenPGP_Message(array($sig, $message));
  }

  // Pass a message with a key and userid packet to sign
  function sign_key_userid($packet, $hash='SHA256', $keyid=NULL) {
    if(is_array($packet)) {
      $packet = new OpenPGP_Message($packet);
    } else if(!is_object($packet)) {
      $packet = OpenPGP_Message::parse($packet);
    }

    $key = $this->private_key($keyid);
    if(!$key || !$packet) return NULL; // Missing some data

    if(!$keyid) $keyid = substr($this->key->fingerprint, -16);
    $key->setHash(strtolower($hash));

    $sig = $packet->signature_and_data();
    $sig = $sig[1];
    if(!$sig) {
      $sig = new OpenPGP_SignaturePacket($packet, 'RSA', strtoupper($hash)); 
      $sig->signature_type = 0x13;
      $sig->hashed_subpackets[] = new OpenPGP_SignaturePacket_KeyFlagsPacket(array(0x01, 0x02));
      $sig->hashed_subpackets[] = new OpenPGP_SignaturePacket_IssuerPacket($keyid);
      $packet[] = $sig;
    }

    $sig->sign_data(array('RSA' => array($hash => array($key, 'sign'))));

    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, substr($p->encyrpted_data, 2));
        } else if(strlen(str_replace('0', '', $p->keyid)) < 1) {
          foreach($keys->key as $k) {
            $sk = self::try_decrypt_session(self::convert_private_key($k), substr($p->encyrpted_data, 2));
            if($sk) break;
          }
        } else {
          $key = $keys->private_key($p->keyid);
          $sk = self::try_decrypt_session($key, substr($p->encrypted_data, 2));
        }

        if(!$sk) continue;

        $r = OpenPGP_Crypt_Symmetric::decryptPacket(OpenPGP_Crypt_Symmetric::getEncryptedData($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);
    $rsa->setHash(strtolower($hash));
    $rsa->modulus = new Math_BigInteger($mod, 256);
    $rsa->k = strlen($rsa->modulus->toBytes());
    $rsa->exponent = new Math_BigInteger($exp, 256);
    $rsa->setPublicKey();
    return $rsa;
  }

  static function convert_key($packet, $private=false) {
    if(!is_object($packet)) $packet = OpenPGP_Message::parse($packet);
    if($packet instanceof OpenPGP_Message) $packet = $packet[0];

    $mod = $packet->key['n'];
    $exp = $packet->key['e'];
    if($private) $exp = $packet->key['d'];
    if(!$exp) return NULL; // Packet doesn't have needed data

    $rsa = self::crypt_rsa_key($mod, $exp);

    if($private) {
      if($packet->key['p'] && $packet->key['q']) $rsa->primes = array($packet->key['p'], $packet->key['q']);
      if($packet->key['u']) $rsa->coefficients = array($packet->key['u']);
    }

    return $rsa;
  }

  static function convert_public_key($packet) {
    return self::convert_key($packet, false);
  }

  static function convert_private_key($packet) {
    return self::convert_key($packet, true);
  }

}

?>