384 lines
11 KiB
Text
384 lines
11 KiB
Text
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% Copyright (C) 1996, 1997 Geoffrey Keating.
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% This file may be freely distributed with or without modifications,
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% so long as proper attribution is given and copyright notices are
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% not removed.
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% pdf_sec.ps (version 1.0.3)
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% Implementation of security hooks for PDF reader.
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% This file contains the procedures that have to take encryption into
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% account when reading a PDF file. It replaces the stub version of this
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% file that is shipped with GhostScript. It requires GhostScript version 4.02
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% or later.
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/.setlanguagelevel where { pop 2 .setlanguagelevel } if
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.currentglobal true .setglobal
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/pdfdict where { pop } { /pdfdict 100 dict def } ifelse
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pdfdict begin
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% Older ghostscript versions do not have .pdftoken, so we use 'token' instead.
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/.pdftoken where { pop } { /.pdftoken /token load def } ifelse
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% An implementation of an algorithm compatible with the RSA Data Security
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% Inc. RC4 stream encryption algorithm.
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% <string> rc4setkey <dict>
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/rc4setkey
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{
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6 dict begin
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/k exch def
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/a 256 string def
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0 1 255 { a exch dup put } for
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/l k length def
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/j 0 def
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0 1 255
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{
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/i exch def
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/j a i get k i l mod get add j add 255 and def
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a i a j get a j a i get put put
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} for
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3 dict dup begin
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/a a def
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/x 0 def
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/y 0 def
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end
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end
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} bind def
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% <rc4key> <string> rc4 <string> <rc4key>
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/rc4
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{
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1 index begin
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dup dup length 1 sub 0 exch 1 exch
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{
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/x x 1 add 255 and def
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/y a x get y add 255 and def
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a x a y get a y a x get put put
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% stack: string string index
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2 copy get
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a dup x get a y get add 255 and get
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xor put dup
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} for
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pop
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end
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} bind def
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% take a stream and rc4 decrypt it.
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% <stream> <key> rc4decodefilter <stream>
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/rc4decodefilter {
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currentglobal exch true setglobal
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dup length string copy rc4setkey
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exch setglobal
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exch 512 string
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% stack: <key> <stream> <string>
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{ readstring pop rc4 exch pop } aload pop
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8 array astore cvx 0 () /SubFileDecode filter
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} bind def
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% MD5 derived from RFC 1321, "The MD5 Message-Digest Algorithm",
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% R. Rivest, MIT, RSADSI; implemented in PostScript by Geoffrey Keating.
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% We construct the MD5 transform by a sort of inline expansion.
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% this takes up quite a bit of memory (around 17k), but gives a
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% factor-of-two speed increase.
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% This also allows us to take advantage of interpreters with 64-bit
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% wide integers.
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% This will not run on interpreters with 16-bit wide integers, if such
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% things exist.
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20 dict begin
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/T [
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16#d76aa478 16#e8c7b756 16#242070db 16#c1bdceee
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16#f57c0faf 16#4787c62a 16#a8304613 16#fd469501
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16#698098d8 16#8b44f7af 16#ffff5bb1 16#895cd7be
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16#6b901122 16#fd987193 16#a679438e 16#49b40821
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16#f61e2562 16#c040b340 16#265e5a51 16#e9b6c7aa
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16#d62f105d 16#02441453 16#d8a1e681 16#e7d3fbc8
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16#21e1cde6 16#c33707d6 16#f4d50d87 16#455a14ed
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16#a9e3e905 16#fcefa3f8 16#676f02d9 16#8d2a4c8a
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16#fffa3942 16#8771f681 16#6d9d6122 16#fde5380c
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16#a4beea44 16#4bdecfa9 16#f6bb4b60 16#bebfbc70
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16#289b7ec6 16#eaa127fa 16#d4ef3085 16#04881d05
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16#d9d4d039 16#e6db99e5 16#1fa27cf8 16#c4ac5665
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16#f4292244 16#432aff97 16#ab9423a7 16#fc93a039
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16#655b59c3 16#8f0ccc92 16#ffeff47d 16#85845dd1
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16#6fa87e4f 16#fe2ce6e0 16#a3014314 16#4e0811a1
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16#f7537e82 16#bd3af235 16#2ad7d2bb 16#eb86d391
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] def
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/F [
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{ c d /xor b /and d /xor } { b c /xor d /and c /xor }
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{ b c /xor d /xor } { d /not b /or c /xor }
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] def
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/R [
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16#0007 16#010c 16#0211 16#0316 16#0407 16#050c 16#0611 16#0716
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16#0807 16#090c 16#0a11 16#0b16 16#0c07 16#0d0c 16#0e11 16#0f16
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16#0105 16#0609 16#0b0e 16#0014 16#0505 16#0a09 16#0f0e 16#0414
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16#0905 16#0e09 16#030e 16#0814 16#0d05 16#0209 16#070e 16#0c14
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16#0504 16#080b 16#0b10 16#0e17 16#0104 16#040b 16#0710 16#0a17
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16#0d04 16#000b 16#0310 16#0617 16#0904 16#0c0b 16#0f10 16#0217
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16#0006 16#070a 16#0e0f 16#0515 16#0c06 16#030a 16#0a0f 16#0115
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16#0806 16#0f0a 16#060f 16#0d15 16#0406 16#0b0a 16#020f 16#0915
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] def
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/W 1 31 bitshift 0 gt def
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/A W { /add } { /md5add } ifelse def
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/t W { 1744 } { 1616 } ifelse array def
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/C 0 def
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0 1 63 {
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/i exch def
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/r R i get def
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/a/b/c/d 4 i 3 and roll [ /d/c/b/a ] { exch def } forall
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t C [
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a F i -4 bitshift get exec
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a A /x r -8 bitshift /get A T i get A
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W { 1 32 bitshift 1 sub /and } if
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/dup r 31 and /bitshift /exch r 31 and 32 sub /bitshift /or
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b A
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/def
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] dup length C add /C exch def putinterval
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} for
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1 1 C 1 sub {
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dup 1 sub t exch get /def cvx eq
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{pop}
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{t exch 2 copy get cvx put}
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ifelse
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} for
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% If we could put t into a _packed_ array, its memory requirements
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% would go from about 13k to about 4k. Unfortunately, we'd need around
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% 1600 stack positions, around 3 times what we can expect to have
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% available---and if that kind of memory is available, we don't really
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% need to pack t. Sigh.
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% In fact, it's worse than that. You can't even determine what t will
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% be and write it in directly (something like
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% { /a c d xor b and d xor a md5add x 0 get md5add -680876936 md5add dup 7
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% bitshift exch -25 bitshift or b md5add def /d b c xor a ...
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% ) because the scanner uses the operand stack to accumulate procedures.
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% So the only way to have md5transform as a single procedure is the above
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% trick.
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W /md5transform t end cvx bind def
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% Unfortunately, PostScript & its imitators convert large
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% integers to floating-point. Worse, the fp representation probably
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% won't have 32 significant bits.
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% This procedure accounts for about 35% of the total time on 32-bit
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% machines.
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not {
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/md5add {
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2 copy xor 0 lt
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% if one is positive and one is negative, can't overflow
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{ add }
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% if both are positive or negative
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{ 16#80000000 xor add 16#80000000 xor }
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% same as subtracting (or adding) 2^31 and then subtracting (or
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% adding) it back.
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ifelse
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} bind def
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} {
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/md5add {
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add 16#0FFFFFFFF and
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} bind def
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} ifelse
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/md5 {
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20 dict begin
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% initialise a,b,c,d,x
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/a 16#67452301 def
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/b 16#efcdab89 def
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/c 16#98badcfe def
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/d 16#10325476 def
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/x 16 array def
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% parameters
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/origs exch def
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/oslen origs length def
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% pad string to multiple of 512 bits
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/s oslen 72 add 64 idiv 64 mul dup /slen exch def string def
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s 0 origs putinterval
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s oslen 16#80 put
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s slen 8 sub oslen 31 and 3 bitshift put
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s slen 7 sub oslen -5 bitshift 255 and put
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s slen 6 sub oslen -13 bitshift 255 and put
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0 64 slen 64 sub {
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dup 1 exch 63 add { s exch get } for
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15 -1 0 { x exch 6 2 roll 3 { 8 bitshift or } repeat put } for
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a b c d
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md5transform
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d md5add /d exch def
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c md5add /c exch def
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b md5add /b exch def
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a md5add /a exch def
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} for
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16 string
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[ [ a b c d ] { 3 { dup -8 bitshift } repeat } forall ]
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0 1 15 {
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3 copy dup 3 1 roll get 255 and put pop
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} for
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pop
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end
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} bind def
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% Pad a key out to 32 bytes.
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/pdf_pad_key % <key> pdf_pad_key <padded key>
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{ dup length 32 gt { 0 32 getinterval } if
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<28bf4e5e4e758a41 64004e56fffa0108
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2e2e00b6d0683e80 2f0ca9fe6453697a>
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0 32 3 index length sub getinterval
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concatstrings
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} bind def
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% Try a user key for a PDF file.
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/pdf_try_key % <key> pdf_try_key <filekey> true
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% <key> pdf_try_key false
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{ Trailer /Encrypt oget
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dup /O oget exch
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/P oget 4 string exch
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2 copy 255 and 0 exch put
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2 copy -8 bitshift 255 and 1 exch put
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2 copy -16 bitshift 255 and 2 exch put
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2 copy -24 bitshift 255 and 3 exch put pop
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Trailer /ID oget 0 oget
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3 { concatstrings } repeat
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md5 0 5 getinterval
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dup
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Trailer /Encrypt oget /U oget dup length string copy exch
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rc4setkey exch rc4 exch pop
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<28bf4e5e4e758a41 64004e56fffa0108
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2e2e00b6d0683e80 2f0ca9fe6453697a> eq
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dup not { exch pop } if
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} bind def
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% Process the encryption information in the Trailer.
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/pdf_process_Encrypt
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{ Trailer /Encrypt oget
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/Filter oget /Standard eq not
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{ (****This file uses an unknown security handler.\n) print flush
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/pdf_process_Encrypt cvx /undefined signalerror
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}
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if
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() pdf_pad_key pdf_try_key
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{ /FileKey exch def }
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{ /PDFPassword where
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{ PDFPassword pdf_pad_key pdf_try_key
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{ true }
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{ PDFPassword pdf_pad_key md5 0 5 getinterval rc4setkey
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Trailer /Encrypt oget /O oget dup length string copy
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rc4 exch pop
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pdf_try_key
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}
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ifelse
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{ /FileKey exch def }
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{ (****Password did not work.\n) print flush
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/pdf_process_Encrypt cvx /invalidfileaccess signalerror
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}
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ifelse
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}
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{ (****This file has a user password set.\n) print flush
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/pdf_process_Encrypt cvx /invalidfileaccess signalerror
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}
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ifelse
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}
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ifelse
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Trailer /Encrypt oget /P oget 4 and 0 eq #? and
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{ (****This owner of this file has requested you do not print it.\n)
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print flush
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/pdf_process_Encrypt cvx /invalidfileaccess signalerror
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}
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if
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} bind def
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% Calculate the key used to decrypt an object (to pass to .decpdfrun or
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% put into a stream dictionary).
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/computeobjkey % <object#> <generation#> computeobjkey <keystring>
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{
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exch
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10 string
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dup 0 FileKey putinterval
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exch
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% stack: gen# string obj#
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2 copy 255 and 5 exch put
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2 copy -8 bitshift 255 and 6 exch put
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2 copy -16 bitshift 255 and 7 exch put
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pop exch
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2 copy 255 and 8 exch put
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2 copy -8 bitshift 255 and 9 exch put
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pop md5 0 10 getinterval
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} bind def
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% As .pdfrun, but decrypt strings with key <key>.
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/.decpdfrun % <file> <keystring> <opdict> .decpdfrun -
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{ % Construct a procedure with the file, opdict and key bound into it.
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2 index cvlit mark mark 5 2 roll
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{ .pdftoken not { (%%EOF) cvn cvx } if
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dup xcheck
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{ DEBUG { dup == flush } if
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3 -1 roll pop
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2 copy .knownget
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{ exch pop exch pop exec }
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{ (%stderr) (w) file
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dup (****************Unknown operator: ) writestring
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dup 3 -1 roll .writecvs dup (\n) writestring flushfile
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pop
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}
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ifelse
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}
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{ exch pop DEBUG { dup ==only ( ) print flush } if
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dup type /stringtype eq
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{ exch rc4setkey exch rc4 }
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if
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exch pop
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}
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ifelse
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}
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aload pop .packtomark cvx
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/loop cvx 2 packedarray cvx
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{ stopped /PDFsource } aload pop
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PDFsource
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{ store { stop } if } aload pop .packtomark cvx
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/PDFsource 3 -1 roll store exec
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} bind def
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% Run the code to resolve an object reference.
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/pdf_run_resolve
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{ /FileKey where
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{ pop
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2 copy computeobjkey dup 4 1 roll
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||
|
|
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
|