% Copyright (C) 1996-1998 Geoffrey Keating. % 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. % pdf_sec.ps (version 1.0.4) % 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 version 4.02 % or later. % Documentation for using this file is available at % http://www.ozemail.com.au/%7Egeoffk/pdfencrypt/ /.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 % An implementation of an algorithm compatible with the RSA Data Security % Inc. RC4 stream encryption algorithm. % rc4setkey /rc4setkey { 6 dict begin /k exch def /a 256 string def 0 1 255 { a exch dup put } for /l k length def /j 0 def 0 1 255 { /i exch def /j a i get k i l mod get add j add 255 and def a i a j get a j a i get put put } for 3 dict dup begin /a a def /x 0 def /y 0 def end end } bind def % rc4 /rc4 { 1 index begin dup dup length 1 sub 0 exch 1 exch { /x x 1 add 255 and def /y a x get y add 255 and def a x a y get a y a x get put put % stack: string string index 2 copy get a dup x get a y get add 255 and get xor put dup } for pop end } bind def % take a stream and rc4 decrypt it. % rc4decodefilter /rc4decodefilter { currentglobal exch true setglobal dup length string copy rc4setkey exch setglobal exch 512 string % stack: { readstring pop rc4 exch pop } aload pop 8 array astore cvx 0 () /SubFileDecode filter } bind def % MD5 derived from RFC 1321, "The MD5 Message-Digest Algorithm", % R. Rivest, MIT, RSADSI; implemented in PostScript by Geoffrey Keating. % We construct the MD5 transform by a sort of inline expansion. % this takes up quite a bit of memory (around 17k), but gives a % factor-of-two speed increase. % This also allows us to take advantage of interpreters with 64-bit % wide integers. % This will not run on interpreters with 16-bit wide integers, if such % things exist. 20 dict begin /T [ 16#d76aa478 16#e8c7b756 16#242070db 16#c1bdceee 16#f57c0faf 16#4787c62a 16#a8304613 16#fd469501 16#698098d8 16#8b44f7af 16#ffff5bb1 16#895cd7be 16#6b901122 16#fd987193 16#a679438e 16#49b40821 16#f61e2562 16#c040b340 16#265e5a51 16#e9b6c7aa 16#d62f105d 16#02441453 16#d8a1e681 16#e7d3fbc8 16#21e1cde6 16#c33707d6 16#f4d50d87 16#455a14ed 16#a9e3e905 16#fcefa3f8 16#676f02d9 16#8d2a4c8a 16#fffa3942 16#8771f681 16#6d9d6122 16#fde5380c 16#a4beea44 16#4bdecfa9 16#f6bb4b60 16#bebfbc70 16#289b7ec6 16#eaa127fa 16#d4ef3085 16#04881d05 16#d9d4d039 16#e6db99e5 16#1fa27cf8 16#c4ac5665 16#f4292244 16#432aff97 16#ab9423a7 16#fc93a039 16#655b59c3 16#8f0ccc92 16#ffeff47d 16#85845dd1 16#6fa87e4f 16#fe2ce6e0 16#a3014314 16#4e0811a1 16#f7537e82 16#bd3af235 16#2ad7d2bb 16#eb86d391 ] def /F [ { c d /xor b /and d /xor } { b c /xor d /and c /xor } { b c /xor d /xor } { d /not b /or c /xor } ] def /R [ 16#0007 16#010c 16#0211 16#0316 16#0407 16#050c 16#0611 16#0716 16#0807 16#090c 16#0a11 16#0b16 16#0c07 16#0d0c 16#0e11 16#0f16 16#0105 16#0609 16#0b0e 16#0014 16#0505 16#0a09 16#0f0e 16#0414 16#0905 16#0e09 16#030e 16#0814 16#0d05 16#0209 16#070e 16#0c14 16#0504 16#080b 16#0b10 16#0e17 16#0104 16#040b 16#0710 16#0a17 16#0d04 16#000b 16#0310 16#0617 16#0904 16#0c0b 16#0f10 16#0217 16#0006 16#070a 16#0e0f 16#0515 16#0c06 16#030a 16#0a0f 16#0115 16#0806 16#0f0a 16#060f 16#0d15 16#0406 16#0b0a 16#020f 16#0915 ] def /W 1 31 bitshift 0 gt def /A W { /add } { /md5add } ifelse def /t W { 1744 } { 1616 } ifelse array def /C 0 def 0 1 63 { /i exch def /r R i get def /a/b/c/d 4 i 3 and roll [ /d/c/b/a ] { exch def } forall t C [ a F i -4 bitshift get exec a A /x r -8 bitshift /get A T i get A W { 1 32 bitshift 1 sub /and } if /dup r 31 and /bitshift /exch r 31 and 32 sub /bitshift /or b A /def ] dup length C add /C exch def putinterval } for 1 1 C 1 sub { dup 1 sub t exch get /def cvx eq {pop} {t exch 2 copy get cvx put} ifelse } for % If we could put t into a _packed_ array, its memory requirements % would go from about 13k to about 4k. Unfortunately, we'd need around % 1600 stack positions, around 3 times what we can expect to have % available---and if that kind of memory is available, we don't really % need to pack t. Sigh. % In fact, it's worse than that. You can't even determine what t will % be and write it in directly (something like % { /a c d xor b and d xor a md5add x 0 get md5add -680876936 md5add dup 7 % bitshift exch -25 bitshift or b md5add def /d b c xor a ... % ) because the scanner uses the operand stack to accumulate procedures. % So the only way to have md5transform as a single procedure is the above % trick. W /md5transform t end cvx bind def % Unfortunately, PostScript & its imitators convert large % integers to floating-point. Worse, the fp representation probably % won't have 32 significant bits. % This procedure accounts for about 35% of the total time on 32-bit % machines. not { /md5add { 2 copy xor 0 lt % if one is positive and one is negative, can't overflow { add } % if both are positive or negative { 16#80000000 xor add 16#80000000 xor } % same as subtracting (or adding) 2^31 and then subtracting (or % adding) it back. ifelse } bind def } { /md5add { add 16#0FFFFFFFF and } bind def } ifelse /md5 { 20 dict begin % initialise a,b,c,d,x /a 16#67452301 def /b 16#efcdab89 def /c 16#98badcfe def /d 16#10325476 def /x 16 array def % parameters /origs exch def /oslen origs length def % pad string to multiple of 512 bits /s oslen 72 add 64 idiv 64 mul dup /slen exch def string def s 0 origs putinterval s oslen 16#80 put s slen 8 sub oslen 31 and 3 bitshift put s slen 7 sub oslen -5 bitshift 255 and put s slen 6 sub oslen -13 bitshift 255 and put 0 64 slen 64 sub { dup 1 exch 63 add { s exch get } for 15 -1 0 { x exch 6 2 roll 3 { 8 bitshift or } repeat put } for a b c d md5transform d md5add /d exch def c md5add /c exch def b md5add /b exch def a md5add /a exch def } for 16 string [ [ a b c d ] { 3 { dup -8 bitshift } repeat } forall ] 0 1 15 { 3 copy dup 3 1 roll get 255 and put pop } for pop end } bind def % Pad a key out to 32 bytes. /pdf_pad_key % pdf_pad_key { dup length 32 gt { 0 32 getinterval } if <28bf4e5e4e758a41 64004e56fffa0108 2e2e00b6d0683e80 2f0ca9fe6453697a> 0 32 3 index length sub getinterval concatstrings } bind def % Try a user key for a PDF file. /pdf_try_key % pdf_try_key true % pdf_try_key false { Trailer /Encrypt oget dup /O oget 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 Trailer /ID oget 0 oget 3 { concatstrings } repeat md5 0 5 getinterval dup Trailer /Encrypt oget /U oget dup length string copy exch rc4setkey exch rc4 exch pop <28bf4e5e4e758a41 64004e56fffa0108 2e2e00b6d0683e80 2f0ca9fe6453697a> eq dup not { exch pop } if } 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_pad_key pdf_try_key { /FileKey exch def } { /PDFPassword where { pop PDFPassword pdf_pad_key pdf_try_key { true } { PDFPassword pdf_pad_key md5 0 5 getinterval rc4setkey Trailer /Encrypt oget /O oget dup length string copy rc4 exch pop pdf_try_key } ifelse { /FileKey exch def } { (****Password did not work.\n) print flush /pdf_process_Encrypt cvx /invalidfileaccess signalerror } ifelse } { (****This file has a user password set.\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 % computeobjkey { exch 10 string dup 0 FileKey putinterval exch % stack: gen# string obj# 2 copy 255 and 5 exch put 2 copy -8 bitshift 255 and 6 exch put 2 copy -16 bitshift 255 and 7 exch put pop exch 2 copy 255 and 8 exch put 2 copy -8 bitshift 255 and 9 exch put pop md5 0 10 getinterval } bind def % As .pdfrun, but decrypt strings with key . /.decpdfrun % .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 } { (%stderr) (w) file dup (****************Unknown operator: ) writestring dup 3 -1 roll .writecvs dup (\n) writestring flushfile pop } ifelse } { exch pop DEBUG { dup ==only ( ) print flush } if dup type /stringtype eq { exch rc4setkey exch rc4 } 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 () /SubFileDecode filter 3 index /StreamKey get rc4decodefilter exch } if } bind def end % pdfdict .setglobal