Protection

This script allows to protect the PDF

Informations

Author: Klemen Vodopivec
License: FPDF

Description

This script allows to protect the PDF, that is to say prevent people from copying its content, print it or modify it.

Important: some PDF readers like Firefox ignore the protection settings, which strongly reduces the usefulness of this script.

SetProtection([array permissions [, string user_pass [, string owner_pass]]])

permissions: the set of permissions. Empty by default (only viewing is allowed).
user_pass: user password. Empty by default.
owner_pass: owner password. If not specified, a random value is used.

The permission array contains values taken from the following list:
  • copy: copy text and images to the clipboard
  • print: print the document
  • modify: modify it (except for annotations and forms)
  • annot-forms: add annotations and forms
The protection against modification is for people who have the full Acrobat product.

If you don't set any password, the document will open as usual. If you set a user password, the PDF viewer will ask for it before displaying the document. The master password, if different from the user one, can be used to get full access.

Note: protecting a document requires to encrypt it. The Mcrypt extension is used if available. If not, the encryption is done in PHP, which can increase the processing time significantly (especially if the document contains images or fonts).

Source

<?php /**************************************************************************** * Software: FPDF_Protection * * Version: 1.04 * * Date: 2015-12-06 * * Author: Klemen VODOPIVEC * * License: FPDF * * * * Thanks: Cpdf (http://www.ros.co.nz/pdf) was my working sample of how to * * implement protection in pdf. * ****************************************************************************/ require('fpdf.php'); if(function_exists('mcrypt_encrypt')) { function RC4($key, $data) { return mcrypt_encrypt(MCRYPT_ARCFOUR, $key, $data, MCRYPT_MODE_STREAM, ''); } } else { function RC4($key, $data) { static $last_key, $last_state; if($key != $last_key) { $k = str_repeat($key, 256/strlen($key)+1); $state = range(0, 255); $j = 0; for ($i=0; $i<256; $i++){ $t = $state[$i]; $j = ($j + $t + ord($k[$i])) % 256; $state[$i] = $state[$j]; $state[$j] = $t; } $last_key = $key; $last_state = $state; } else $state = $last_state; $len = strlen($data); $a = 0; $b = 0; $out = ''; for ($i=0; $i<$len; $i++){ $a = ($a+1) % 256; $t = $state[$a]; $b = ($b+$t) % 256; $state[$a] = $state[$b]; $state[$b] = $t; $k = $state[($state[$a]+$state[$b]) % 256]; $out .= chr(ord($data[$i]) ^ $k); } return $out; } } class FPDF_Protection extends FPDF { var $encrypted = false; //whether document is protected var $Uvalue; //U entry in pdf document var $Ovalue; //O entry in pdf document var $Pvalue; //P entry in pdf document var $enc_obj_id; //encryption object id /** * Function to set permissions as well as user and owner passwords * * - permissions is an array with values taken from the following list: * copy, print, modify, annot-forms * If a value is present it means that the permission is granted * - If a user password is set, user will be prompted before document is opened * - If an owner password is set, document can be opened in privilege mode with no * restriction if that password is entered */ function SetProtection($permissions=array(), $user_pass='', $owner_pass=null) { $options = array('print' => 4, 'modify' => 8, 'copy' => 16, 'annot-forms' => 32 ); $protection = 192; foreach($permissions as $permission) { if (!isset($options[$permission])) $this->Error('Incorrect permission: '.$permission); $protection += $options[$permission]; } if ($owner_pass === null) $owner_pass = uniqid(rand()); $this->encrypted = true; $this->padding = "\x28\xBF\x4E\x5E\x4E\x75\x8A\x41\x64\x00\x4E\x56\xFF\xFA\x01\x08". "\x2E\x2E\x00\xB6\xD0\x68\x3E\x80\x2F\x0C\xA9\xFE\x64\x53\x69\x7A"; $this->_generateencryptionkey($user_pass, $owner_pass, $protection); } /**************************************************************************** * * * Private methods * * * ****************************************************************************/ function _putstream($s) { if ($this->encrypted) $s = RC4($this->_objectkey($this->n), $s); parent::_putstream($s); } function _textstring($s) { if (!$this->_isascii($s)) $s = $this->_UTF8toUTF16($s); if ($this->encrypted) $s = RC4($this->_objectkey($this->n), $s); return '('.$this->_escape($s).')'; } /** * Compute key depending on object number where the encrypted data is stored */ function _objectkey($n) { return substr($this->_md5_16($this->encryption_key.pack('VXxx', $n)), 0, 10); } function _putresources() { parent::_putresources(); if ($this->encrypted) { $this->_newobj(); $this->enc_obj_id = $this->n; $this->_put('<<'); $this->_putencryption(); $this->_put('>>'); $this->_put('endobj'); } } function _putencryption() { $this->_put('/Filter /Standard'); $this->_put('/V 1'); $this->_put('/R 2'); $this->_put('/O ('.$this->_escape($this->Ovalue).')'); $this->_put('/U ('.$this->_escape($this->Uvalue).')'); $this->_put('/P '.$this->Pvalue); } function _puttrailer() { parent::_puttrailer(); if ($this->encrypted) { $this->_put('/Encrypt '.$this->enc_obj_id.' 0 R'); $this->_put('/ID [()()]'); } } /** * Get MD5 as binary string */ function _md5_16($string) { return pack('H*', md5($string)); } /** * Compute O value */ function _Ovalue($user_pass, $owner_pass) { $tmp = $this->_md5_16($owner_pass); $owner_RC4_key = substr($tmp, 0, 5); return RC4($owner_RC4_key, $user_pass); } /** * Compute U value */ function _Uvalue() { return RC4($this->encryption_key, $this->padding); } /** * Compute encryption key */ function _generateencryptionkey($user_pass, $owner_pass, $protection) { // Pad passwords $user_pass = substr($user_pass.$this->padding, 0, 32); $owner_pass = substr($owner_pass.$this->padding, 0, 32); // Compute O value $this->Ovalue = $this->_Ovalue($user_pass, $owner_pass); // Compute encyption key $tmp = $this->_md5_16($user_pass.$this->Ovalue.chr($protection)."\xFF\xFF\xFF"); $this->encryption_key = substr($tmp, 0, 5); // Compute U value $this->Uvalue = $this->_Uvalue(); // Compute P value $this->Pvalue = -(($protection^255)+1); } } ?>

Example

This example shows how to allow only printing.
<?php require('fpdf_protection.php'); $pdf = new FPDF_Protection(); $pdf->SetProtection(array('print')); $pdf->AddPage(); $pdf->SetFont('Arial'); $pdf->Write(10, 'You can print me but not copy my text.'); $pdf->Output(); ?>
View the result here.

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Quelle

http://www.fpdf.org/en/script/script37.php, zuletzt abgerufen 02.10.2016 05:36