lib/tcpdf/tcpdfprotection.php

   1 <?php
   2 /****************************************************************************
   3 * Software: FPDF_Protection                                                 *
   4 * Version:  1.02                                                            *
   5 * Date:     2005/05/08                                                      *
   6 * Author:   Klemen VODOPIVEC                                                *
   7 * License:  Freeware                                                        *
   8 *                                                                           *
   9 * You may use and modify this software as you wish as stated in original    *
  10 * FPDF package.                                                             *
  11 *                                                                           *
  12 * Thanks: Cpdf (http://www.ros.co.nz/pdf) was my working sample of how to   *
  13 * implement protection in pdf.                                              *
  14 ****************************************************************************/
  15
  16 require_once('tcpdf.php');
  17
  18 class TCPDF_Protection extends TCPDF
  19 {
  20     var $encrypted;          //whether document is protected
  21     var $Uvalue;             //U entry in pdf document
  22     var $Ovalue;             //O entry in pdf document
  23     var $Pvalue;             //P entry in pdf document
  24     var $enc_obj_id;         //encryption object id
  25     var $last_rc4_key;       //last RC4 key encrypted (cached for optimisation)
  26     var $last_rc4_key_c;     //last RC4 computed key
  27
  28     function TCPDF_Protection($orientation='P',$unit='mm',$format='A4') {
  29         parent::TCPDF($orientation,$unit,$format);
  30
  31         $this->encrypted=false;
  32         $this->last_rc4_key='';
  33         $this->padding="\x28\xBF\x4E\x5E\x4E\x75\x8A\x41\x64\x00\x4E\x56\xFF\xFA\x01\x08".
  34                         "\x2E\x2E\x00\xB6\xD0\x68\x3E\x80\x2F\x0C\xA9\xFE\x64\x53\x69\x7A";
  35     }
  36
  37     /**
  38     * Function to set permissions as well as user and owner passwords
  39     *
  40     * - permissions is an array with values taken from the following list:
  41     *   copy, print, modify, annot-forms
  42     *   If a value is present it means that the permission is granted
  43     * - If a user password is set, user will be prompted before document is opened
  44     * - If an owner password is set, document can be opened in privilege mode with no
  45     *   restriction if that password is entered
  46     */
  47     function SetProtection($permissions=array(),$user_pass='',$owner_pass=null) {
  48         $options = array('print' => 4, 'modify' => 8, 'copy' => 16, 'annot-forms' => 32 );
  49         $protection = 192;
  50         foreach($permissions as $permission){
  51             if (!isset($options[$permission]))
  52                 $this->Error('Incorrect permission: '.$permission);
  53             $protection += $options[$permission];
  54         }
  55         if ($owner_pass === null)
  56             $owner_pass = uniqid(rand());
  57         $this->encrypted = true;
  58         $this->_generateencryptionkey($user_pass, $owner_pass, $protection);
  59     }
  60
  61 /****************************************************************************
  62 *                                                                           *
  63 *                              Private methods                              *
  64 *                                                                           *
  65 ****************************************************************************/
  66
  67     function _putstream($s) {
  68         if ($this->encrypted) {
  69             $s = $this->_RC4($this->_objectkey($this->n), $s);
  70         }
  71         parent::_putstream($s);
  72     }
  73
  74     function _textstring($s) {
  75         if ($this->encrypted) {
  76             $s = $this->_RC4($this->_objectkey($this->n), $s);
  77         }
  78         return parent::_textstring($s);
  79     }
  80
  81     /**
  82     * Compute key depending on object number where the encrypted data is stored
  83     */
  84     function _objectkey($n) {
  85         return substr($this->_md5_16($this->encryption_key.pack('VXxx',$n)),0,10);
  86     }
  87
  88     /**
  89     * Escape special characters
  90     */
  91     function _escape($s) {
  92         $s=str_replace('\\','\\\\',$s);
  93         $s=str_replace(')','\\)',$s);
  94         $s=str_replace('(','\\(',$s);
  95         $s=str_replace("\r",'\\r',$s);
  96         return $s;
  97     }
  98
  99     function _putresources() {
 100         parent::_putresources();
 101         if ($this->encrypted) {
 102             $this->_newobj();
 103             $this->enc_obj_id = $this->n;
 104             $this->_out('<<');
 105             $this->_putencryption();
 106             $this->_out('>>');
 107             $this->_out('endobj');
 108         }
 109     }
 110
 111     function _putencryption() {
 112         $this->_out('/Filter /Standard');
 113         $this->_out('/V 1');
 114         $this->_out('/R 2');
 115         $this->_out('/O ('.$this->_escape($this->Ovalue).')');
 116         $this->_out('/U ('.$this->_escape($this->Uvalue).')');
 117         $this->_out('/P '.$this->Pvalue);
 118     }
 119
 120     function _puttrailer() {
 121         parent::_puttrailer();
 122         if ($this->encrypted) {
 123             $this->_out('/Encrypt '.$this->enc_obj_id.' 0 R');
 124             $this->_out('/ID [()()]');
 125         }
 126     }
 127
 128     /**
 129     * RC4 is the standard encryption algorithm used in PDF format
 130     */
 131     function _RC4($key, $text) {
 132         if ($this->last_rc4_key != $key) {
 133             $k = str_repeat($key, 256/strlen($key)+1);
 134             $rc4 = range(0,255);
 135             $j = 0;
 136             for ($i=0; $i<256; $i++){
 137                 $t = $rc4[$i];
 138                 $j = ($j + $t + ord($k{$i})) % 256;
 139                 $rc4[$i] = $rc4[$j];
 140                 $rc4[$j] = $t;
 141             }
 142             $this->last_rc4_key = $key;
 143             $this->last_rc4_key_c = $rc4;
 144         } else {
 145             $rc4 = $this->last_rc4_key_c;
 146         }
 147
 148         $len = strlen($text);
 149         $a = 0;
 150         $b = 0;
 151         $out = '';
 152         for ($i=0; $i<$len; $i++){
 153             $a = ($a+1)%256;
 154             $t= $rc4[$a];
 155             $b = ($b+$t)%256;
 156             $rc4[$a] = $rc4[$b];
 157             $rc4[$b] = $t;
 158             $k = $rc4[($rc4[$a]+$rc4[$b])%256];
 159             $out.=chr(ord($text{$i}) ^ $k);
 160         }
 161
 162         return $out;
 163     }
 164
 165     /**
 166     * Get MD5 as binary string
 167     */
 168     function _md5_16($string) {
 169         return pack('H*',md5($string));
 170     }
 171
 172     /**
 173     * Compute O value
 174     */
 175     function _Ovalue($user_pass, $owner_pass) {
 176         $tmp = $this->_md5_16($owner_pass);
 177         $owner_RC4_key = substr($tmp,0,5);
 178         return $this->_RC4($owner_RC4_key, $user_pass);
 179     }
 180
 181     /**
 182     * Compute U value
 183     */
 184     function _Uvalue() {
 185         return $this->_RC4($this->encryption_key, $this->padding);
 186     }
 187
 188     /**
 189     * Compute encryption key
 190     */
 191     function _generateencryptionkey($user_pass, $owner_pass, $protection) {
 192         // Pad passwords
 193         $user_pass = substr($user_pass.$this->padding,0,32);
 194         $owner_pass = substr($owner_pass.$this->padding,0,32);
 195         // Compute O value
 196         $this->Ovalue = $this->_Ovalue($user_pass,$owner_pass);
 197         // Compute encyption key
 198         $tmp = $this->_md5_16($user_pass.$this->Ovalue.chr($protection)."\xFF\xFF\xFF");
 199         $this->encryption_key = substr($tmp,0,5);
 200         // Compute U value
 201         $this->Uvalue = $this->_Uvalue();
 202         // Compute P value
 203         $this->Pvalue = -(($protection^255)+1);
 204     }
 205 }
 206
 207 ?>