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202 lines
5.3 KiB
PHP
202 lines
5.3 KiB
PHP
<?php
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/** @package php-gpg */
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/** require supporting files */
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require_once("GPG/Expanded_Key.php");
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require_once("GPG/Public_Key.php");
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require_once("GPG/AES.php");
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require_once("GPG/globals.php");
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/**
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* Pure PHP implementation of PHP/GPG encryption.
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* Supports RSA, DSA public key length of 2,4,8,16,512,1024,2048 or 4096
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* Currently supports only encrypt
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*
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* @package php-gpg::Encryption
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* @link http://www.verysimple.com/
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* @copyright 1997-2012 VerySimple, Inc.
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* @license http://www.gnu.org/licenses/gpl.html GPL
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* @todo implement decryption
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* @version 1.1
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*
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* @example
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* require_once 'libs/GPG.php';
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* $gpg = new GPG();
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* $pub_key = new GPG_Public_Key($public_key_ascii);
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* $encrypted = $gpg->encrypt($pub_key,$plain_text_string);
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*/
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class GPG
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{
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private $width = 16;
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private $el = array(3, 5, 9, 17, 513, 1025, 2049, 4097);
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private $version = "1.4.7";
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private function gpg_encrypt($key, $text) {
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$i = 0;
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$len = strlen($text);
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$iblock = array_fill(0, $this->width, 0);
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$rblock = array_fill(0, $this->width, 0);
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$ct = array_fill(0, $this->width + 2, 0);
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$cipher = "";
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if($len % $this->width) {
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for($i = ($len % $this->width); $i < $this->width; $i++) $text .= "\0";
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}
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$ekey = new Expanded_Key($key);
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for($i = 0; $i < $this->width; $i++) {
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$iblock[$i] = 0;
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$rblock[$i] = GPG_Utility::c_random();
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}
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$iblock = GPG_AES::encrypt($iblock, $ekey);
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for($i = 0; $i < $this->width; $i++) {
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$ct[$i] = ($iblock[$i] ^= $rblock[$i]);
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}
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$iblock = GPG_AES::encrypt($iblock, $ekey);
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$ct[$this->width] = ($iblock[0] ^ $rblock[$this->width - 2]);
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$ct[$this->width + 1] = ($iblock[1] ^ $rblock[$this->width - 1]);
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for($i = 0; $i < $this->width + 2; $i++) $cipher .= chr($ct[$i]);
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$iblock = array_slice($ct, 2, $this->width + 2);
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for($n = 0; $n < strlen($text); $n += $this->width) {
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$iblock = GPG_AES::encrypt($iblock, $ekey);
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for($i = 0; $i < $this->width; $i++) {
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$iblock[$i] ^= ord($text[$n + $i]);
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$cipher .= chr($iblock[$i]);
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}
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}
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return substr($cipher, 0, $len + $this->width + 2);
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}
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private function gpg_header($tag, $len)
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{
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$h = "";
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if ($len < 0x100) {
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$h .= chr($tag);
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$h .= chr($len);
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} else if ($len < 0x10000) {
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$tag+=1;
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$h .= chr($tag);
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$h .= $this->writeNumber($len, 2);
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} else {
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$tag+=2;
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$h .= chr($tag);
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$h .= $this->writeNumber($len, 4);
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}
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return $h;
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}
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private function writeNumber($n, $bytes)
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{
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// credits for this function go to OpenPGP.js
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$b = '';
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for ($i = 0; $i < $bytes; $i++) {
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$b .= chr(($n >> (8 * ($bytes - $i - 1))) & 0xff);
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}
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return $b;
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}
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private function gpg_session($key_id, $key_type, $session_key, $public_key)
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{
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$mod = array();
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$exp = array();
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$enc = "";
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$s = base64_decode($public_key);
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$l = floor((ord($s[0]) * 256 + ord($s[1]) + 7) / 8);
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$mod = mpi2b(substr($s, 0, $l + 2));
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if($key_type) {
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$grp = array();
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$y = array();
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$B = array();
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$C = array();
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$l2 = floor((ord($s[$l + 2]) * 256 + ord($s[$l + 3]) + 7) / 8) + 2;
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$grp = mpi2b(substr($s, $l + 2, $l2));
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$y = mpi2b(substr($s, $l + 2 + $l2));
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$exp[0] = $this->el[GPG_Utility::c_random() & 7];
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$B = bmodexp($grp, $exp, $mod);
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$C = bmodexp($y, $exp, $mod);
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} else {
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$exp = mpi2b(substr($s, $l + 2));
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}
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$c = 0;
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$lsk = strlen($session_key);
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for($i = 0; $i < $lsk; $i++) $c += ord($session_key[$i]);
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$c &= 0xffff;
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$lm = ($l - 2) * 8 + 2;
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$m = chr($lm / 256) . chr($lm % 256) .
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chr(2) . GPG_Utility::s_random($l - $lsk - 6, 1) . "\0" .
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chr(7) . $session_key .
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chr($c / 256) . chr($c & 0xff);
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if($key_type) {
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$enc = b2mpi($B) . b2mpi(bmod(bmul(mpi2b($m), $C), $mod));
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return $this->gpg_header(0x84,strlen($enc) + 10) .
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chr(3) . $key_id . chr(16) . $enc;
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} else {
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$enc = b2mpi(bmodexp(mpi2b($m), $exp, $mod));
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return $this->gpg_header(0x84, strlen($enc) + 10) .
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chr(3) . $key_id . chr(1) . $enc;
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}
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}
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private function gpg_literal($text)
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{
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if (strpos($text, "\r\n") === false)
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$text = str_replace("\n", "\r\n", $text);
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return
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$this->gpg_header(0xac, strlen($text) + 10) . "t" .
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chr(4) . "file\0\0\0\0" . $text;
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}
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private function gpg_data($key, $text)
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{
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$enc = $this->gpg_encrypt($key, $this->gpg_literal($text));
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return $this->gpg_header(0xa4, strlen($enc)) . $enc;
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}
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/**
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* GPG Encypts a message to the provided public key
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*
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* @param GPG_Public_Key $pk
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* @param string $plaintext
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* @return string encrypted text
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*/
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function encrypt($pk, $plaintext)
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{
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// normalize the public key
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$key_id = $pk->GetKeyId();
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$key_type = $pk->GetKeyType();
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$public_key = $pk->GetPublicKey();
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$session_key = GPG_Utility::s_random($this->width, 0);
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$key_id = GPG_Utility::hex2bin($key_id);
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$cp = $this->gpg_session($key_id, $key_type, $session_key, $public_key) .
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$this->gpg_data($session_key, $plaintext);
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$code = base64_encode($cp);
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$code = wordwrap($code, 64, "\n", 1);
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return
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"-----BEGIN PGP MESSAGE-----\nVersion: VerySimple PHP-GPG v".$this->version."\n\n" .
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$code . "\n=" . base64_encode(GPG_Utility::crc24($cp)) .
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"\n-----END PGP MESSAGE-----\n";
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}
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}
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?>
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