% Copyright (C) 1996-1998 Geoffrey Keating. % Copyright (C) 2001 Artifex Software, Inc. % This file may be freely distributed with or without modifications, % so long as modified versions are marked as such and copyright notices are % not removed. % $Id: pdf_sec.ps,v 1.5.2.1 2002/04/02 13:57:27 mpsuzuki Exp $ % Implementation of security hooks for PDF reader. % This file contains the procedures that have to take encryption into % account when reading a PDF file. It replaces the stub version of this % file that is shipped with GhostScript. It requires GhostScript 7.01 % or later. % Documentation for using this file is available at % http://www.ozemail.com.au/%7Egeoffk/pdfencrypt/ % Modified by Alex Cherepanov to work with GS 6.60 and higher. % New versions of GS require explicit checks for /true , /false, and /null % in .decpdfrun . This fix is backward-compatible. % Modified by Raph Levien and Ralph Giles to use the new C % implementations of md5 and arcfour in ghostscript 7.01, and to % be compatible with PDF 1.4 128-bit encryption. /.setlanguagelevel where { pop 2 .setlanguagelevel } if .currentglobal true .setglobal /pdfdict where { pop } { /pdfdict 100 dict def } ifelse pdfdict begin % Older ghostscript versions do not have .pdftoken, so we use 'token' instead. /.pdftoken where { pop } { /.pdftoken /token load def } ifelse % take a stream and arc4 decrypt it. % arc4decodefilter /arc4decodefilter { 1 dict begin /Key exch def currentdict end /ArcfourDecode filter } bind def % arc4decode /arc4decode { %(key: ) print dup == (ct: ) print 1 index == 1 index length 0 eq { pop } { 1 index length string 3 1 roll arc4decodefilter exch readstring pop } ifelse } bind def /md5 { 16 string dup /MD5Encode filter dup 4 3 roll writestring closefile } bind def /pdf_padding_string <28bf4e5e4e758a41 64004e56fffa0108 2e2e00b6d0683e80 2f0ca9fe6453697a> def % Pad a key out to 32 bytes. /pdf_pad_key { % <key> pdf_pad_key <padded key> dup length 32 gt { 0 32 getinterval } if pdf_padding_string 0 32 3 index length sub getinterval concatstrings } bind def /pdf_xorbytes { % <iter-num> <key> pdf_xorbytes <xored-key> dup length dup string exch 1 sub 0 1 3 2 roll { % <iter-num> <key> <new-key> <byte-num> dup 3 index exch get 4 index xor % <iter-num> <key> <new-key> <byte-num> <byte> 3 copy put pop pop } for 3 1 roll pop pop } bind def % Get length of encryption key in bytes /pdf_key_length { % pdf_key_length <key_length> Trailer /Encrypt oget /Length knownoget { -3 bitshift } { 5 } ifelse } bind def % Algorithm 3.2 /pdf_compute_encryption_key { % <password> pdf_compute_encryption_key <key> % Step 1. pdf_pad_key % Step 2, 3. Trailer /Encrypt oget dup /O oget % <padded-key> <encrypt> <O> % Step 4. exch /P oget 4 string exch 2 copy 255 and 0 exch put 2 copy -8 bitshift 255 and 1 exch put 2 copy -16 bitshift 255 and 2 exch put 2 copy -24 bitshift 255 and 3 exch put pop % <padded-key> <O> <P> % Step 5. Trailer /ID oget 0 oget 3 { concatstrings } repeat md5 % Step 6. Trailer /Encrypt oget /R oget 3 eq { 50 { md5 } repeat } if % Step 7. 0 pdf_key_length getinterval } bind def % Algorithm 3.4 /pdf_gen_user_password_R2 { % <filekey> pdf_gen_user_password_R2 <U> % Step 2. pdf_padding_string exch arc4decode } bind def % Algorithm 3.5 /pdf_gen_user_password_R3 { % <filekey> pdf_gen_user_password_R3 <U> % Step 2. pdf_padding_string % Step 3. Trailer /ID oget 0 oget concatstrings md5 % Step 4. 1 index arc4decode % Step 5. 1 1 19 { 2 index pdf_xorbytes arc4decode } for exch pop } bind def /pdf_gen_user_password { % <password> pdf_gen_user_password <filekey> <U> % common Step 1 of Algorithms 3.4 and 3.5. pdf_compute_encryption_key dup Trailer /Encrypt oget /R oget dup 2 eq { pop pdf_gen_user_password_R2 } { dup 3 eq { pop pdf_gen_user_password_R3 } { (****This file uses an unknown standard security handler revision: ) print == flush /pdf_check_user_password cvx /undefined signalerror } ifelse } ifelse } bind def % Algorithm 3.6 /pdf_check_user_password { % <password> pdf_check_user_password <filekey> true % <password> pdf_check_user_password false pdf_gen_user_password Trailer /Encrypt oget /U oget 0 2 index length getinterval eq { true } { pop false } ifelse } bind def % Compute an owner key, ie the result of step 4 of Algorithm 3.3 /pdf_owner_key % <password> pdf_owner_key <owner-key> { % Step 1. pdf_pad_key % Step 2. md5 % 3.3 Step 3. Trailer /Encrypt oget /R oget 3 eq { 50 { md5 } repeat } if % Step 4. 0 pdf_key_length getinterval } bind def % Algorithm 3.7 /pdf_check_owner_password { % <password> pdf_check_owner_password <filekey> true % <password> pdf_check_owner_password false % Step 1. pdf_owner_key % Step 2. Trailer /Encrypt oget dup /O oget 2 index arc4decode % <encryption-key> <encrypt-dict> <decrypted-O> % Step 3. exch /R oget 3 eq { 1 1 19 { 2 index pdf_xorbytes arc4decode } for } if exch pop % <result-of-step-3> pdf_check_user_password } bind def % Process the encryption information in the Trailer. /pdf_process_Encrypt { Trailer /Encrypt oget /Filter oget /Standard eq not { (****This file uses an unknown security handler.\n) print flush /pdf_process_Encrypt cvx /undefined signalerror } if () pdf_check_user_password { /FileKey exch def } { /PDFPassword where { pop PDFPassword pdf_check_user_password { /FileKey exch def } { PDFPassword pdf_check_owner_password { /FileKey exch def } { (****Password did not work.\n) print flush /pdf_process_Encrypt cvx /invalidfileaccess signalerror } ifelse } ifelse } { (****This file requires a password for access.\n) print flush /pdf_process_Encrypt cvx /invalidfileaccess signalerror } ifelse } ifelse % Trailer /Encrypt oget /P oget 4 and 0 eq #? and % { (****This owner of this file has requested you do not print it.\n) % print flush % /pdf_process_Encrypt cvx /invalidfileaccess signalerror % } % if } bind def % Calculate the key used to decrypt an object (to pass to .decpdfrun or % put into a stream dictionary). /computeobjkey % <object#> <generation#> computeobjkey <keystring> { exch FileKey length 5 add string dup 0 FileKey putinterval exch % stack: gen# string obj# 2 copy 255 and FileKey length exch put 2 copy -8 bitshift 255 and FileKey length 1 add exch put 2 copy -16 bitshift 255 and FileKey length 2 add exch put pop exch 2 copy 255 and FileKey length 3 add exch put 2 copy -8 bitshift 255 and FileKey length 4 add exch put pop md5 0 FileKey length 5 add 2 index length .min getinterval } bind def % As .pdfrun, but decrypt strings with key <key>. /.decpdfrun % <file> <keystring> <opdict> .decpdfrun - { % Construct a procedure with the file, opdict and key bound into it. 2 index cvlit mark mark 5 2 roll { .pdftoken not { (%%EOF) cvn cvx } if dup xcheck { DEBUG { dup == flush } if 3 -1 roll pop 2 copy .knownget { exch pop exch pop exec } { exch pop dup /true eq { pop //true } { dup /false eq { pop //false } { dup /null eq { pop //null } { (%stderr) (w) file dup (****************Unknown operator: ) writestring dup 3 -1 roll .writecvs dup (\n) writestring flushfile } ifelse } ifelse } ifelse } ifelse } { exch pop DEBUG { dup ==only ( ) print flush } if dup type /stringtype eq { 1 index arc4decode DEBUG { (%Decrypted: ) print dup == flush } if } if exch pop } ifelse } aload pop .packtomark cvx /loop cvx 2 packedarray cvx { stopped /PDFsource } aload pop PDFsource { store { stop } if } aload pop .packtomark cvx /PDFsource 3 -1 roll store exec } bind def % Run the code to resolve an object reference. /pdf_run_resolve { /FileKey where { pop 2 copy computeobjkey dup 4 1 roll PDFfile exch resolveopdict .decpdfrun dup dup dup 5 2 roll % stack: object object key object object xcheck exch type /dicttype eq and { /StreamKey exch put } { pop pop } ifelse } { PDFfile resolveopdict .pdfrun } ifelse } bind def % Prefix a decryption filter to a stream if needed. % Stack: readdata? dict parms file/string filternames % (both before and after). /pdf_decrypt_stream { 3 index /StreamKey known { exch % Stack: readdata? dict parms filternames file/string 3 index /Length oget dup 0 eq { % Handle Length=0 case specially to avoid SubFileDecode semantics pop pop () } { () /SubFileDecode filter } ifelse 3 index /StreamKey get arc4decodefilter exch } if } bind def end % pdfdict .setglobal