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admin/fpdf/fpdf_protection.php
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admin/fpdf/fpdf_protection.php
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<?php
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/****************************************************************************
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* Software: FPDF_Protection *
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* Version: 1.02 *
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* Date: 2005/05/08 *
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* Author: Klemen VODOPIVEC *
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* License: Freeware *
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* *
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* You may use and modify this software as you wish as stated in original *
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* FPDF package. *
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* *
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* Thanks: Cpdf (http://www.ros.co.nz/pdf) was my working sample of how to *
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* implement protection in pdf. *
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****************************************************************************/
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require('fpdf.php');
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class FPDF_Protection extends FPDF
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{
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var $encrypted; //whether document is protected
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var $Uvalue; //U entry in pdf document
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var $Ovalue; //O entry in pdf document
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var $Pvalue; //P entry in pdf document
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var $enc_obj_id; //encryption object id
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var $last_rc4_key; //last RC4 key encrypted (cached for optimisation)
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var $last_rc4_key_c; //last RC4 computed key
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function FPDF_Protection($orientation='P',$unit='mm',$format='A4')
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{
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parent::FPDF($orientation,$unit,$format);
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$this->encrypted=false;
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$this->last_rc4_key='';
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$this->padding="\x28\xBF\x4E\x5E\x4E\x75\x8A\x41\x64\x00\x4E\x56\xFF\xFA\x01\x08".
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"\x2E\x2E\x00\xB6\xD0\x68\x3E\x80\x2F\x0C\xA9\xFE\x64\x53\x69\x7A";
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}
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/**
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* Function to set permissions as well as user and owner passwords
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*
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* - permissions is an array with values taken from the following list:
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* copy, print, modify, annot-forms
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* If a value is present it means that the permission is granted
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* - If a user password is set, user will be prompted before document is opened
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* - If an owner password is set, document can be opened in privilege mode with no
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* restriction if that password is entered
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*/
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function SetProtection($permissions=array(),$user_pass='',$owner_pass=null)
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{
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$options = array('print' => 4, 'modify' => 8, 'copy' => 16, 'annot-forms' => 32 );
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$protection = 192;
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foreach($permissions as $permission){
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if (!isset($options[$permission]))
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$this->Error('Incorrect permission: '.$permission);
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$protection += $options[$permission];
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}
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if ($owner_pass === null)
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$owner_pass = uniqid(rand());
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$this->encrypted = true;
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$this->_generateencryptionkey($user_pass, $owner_pass, $protection);
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}
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/****************************************************************************
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* *
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* Private methods *
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* *
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****************************************************************************/
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function _putstream($s)
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{
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if ($this->encrypted) {
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$s = $this->_RC4($this->_objectkey($this->n), $s);
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}
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parent::_putstream($s);
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}
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function _textstring($s)
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{
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if ($this->encrypted) {
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$s = $this->_RC4($this->_objectkey($this->n), $s);
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}
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return parent::_textstring($s);
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}
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/**
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* Compute key depending on object number where the encrypted data is stored
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*/
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function _objectkey($n)
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{
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return substr($this->_md5_16($this->encryption_key.pack('VXxx',$n)),0,10);
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}
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/**
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* Escape special characters
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*/
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function _escape($s)
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{
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$s=str_replace('\\','\\\\',$s);
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$s=str_replace(')','\\)',$s);
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$s=str_replace('(','\\(',$s);
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$s=str_replace("\r",'\\r',$s);
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return $s;
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}
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function _putresources()
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{
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parent::_putresources();
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if ($this->encrypted) {
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$this->_newobj();
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$this->enc_obj_id = $this->n;
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$this->_out('<<');
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$this->_putencryption();
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$this->_out('>>');
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$this->_out('endobj');
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}
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}
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function _putencryption()
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{
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$this->_out('/Filter /Standard');
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$this->_out('/V 1');
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$this->_out('/R 2');
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$this->_out('/O ('.$this->_escape($this->Ovalue).')');
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$this->_out('/U ('.$this->_escape($this->Uvalue).')');
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$this->_out('/P '.$this->Pvalue);
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}
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function _puttrailer()
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{
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parent::_puttrailer();
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if ($this->encrypted) {
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$this->_out('/Encrypt '.$this->enc_obj_id.' 0 R');
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$this->_out('/ID [()()]');
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}
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}
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/**
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* RC4 is the standard encryption algorithm used in PDF format
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*/
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function _RC4($key, $text)
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{
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if ($this->last_rc4_key != $key) {
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$k = str_repeat($key, 256/strlen($key)+1);
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$rc4 = range(0,255);
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$j = 0;
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for ($i=0; $i<256; $i++){
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$t = $rc4[$i];
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$j = ($j + $t + ord($k{$i})) % 256;
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$rc4[$i] = $rc4[$j];
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$rc4[$j] = $t;
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}
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$this->last_rc4_key = $key;
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$this->last_rc4_key_c = $rc4;
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} else {
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$rc4 = $this->last_rc4_key_c;
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}
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$len = strlen($text);
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$a = 0;
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$b = 0;
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$out = '';
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for ($i=0; $i<$len; $i++){
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$a = ($a+1)%256;
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$t= $rc4[$a];
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$b = ($b+$t)%256;
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$rc4[$a] = $rc4[$b];
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$rc4[$b] = $t;
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$k = $rc4[($rc4[$a]+$rc4[$b])%256];
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$out.=chr(ord($text{$i}) ^ $k);
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}
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return $out;
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}
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/**
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* Get MD5 as binary string
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*/
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function _md5_16($string)
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{
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return pack('H*',md5($string));
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}
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/**
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* Compute O value
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*/
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function _Ovalue($user_pass, $owner_pass)
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{
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$tmp = $this->_md5_16($owner_pass);
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$owner_RC4_key = substr($tmp,0,5);
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return $this->_RC4($owner_RC4_key, $user_pass);
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}
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/**
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* Compute U value
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*/
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function _Uvalue()
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{
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return $this->_RC4($this->encryption_key, $this->padding);
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}
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/**
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* Compute encryption key
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*/
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function _generateencryptionkey($user_pass, $owner_pass, $protection)
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{
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// Pad passwords
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$user_pass = substr($user_pass.$this->padding,0,32);
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$owner_pass = substr($owner_pass.$this->padding,0,32);
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// Compute O value
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$this->Ovalue = $this->_Ovalue($user_pass,$owner_pass);
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// Compute encyption key
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$tmp = $this->_md5_16($user_pass.$this->Ovalue.chr($protection)."\xFF\xFF\xFF");
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$this->encryption_key = substr($tmp,0,5);
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// Compute U value
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$this->Uvalue = $this->_Uvalue();
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// Compute P value
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$this->Pvalue = -(($protection^255)+1);
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}
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}
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?>
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