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-% 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.
-% <stream> <key> arc4decodefilter <stream>
-/arc4decodefilter {
- 1 dict begin
- /Key exch def
- currentdict end /ArcfourDecode filter
-} bind def
-
-% <ciphertext> <key> arc4decode <plaintext>
-/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