ActivePerl Documentation
Table of Contents
Getting Started
Welcome To ActivePerl Release Notes Readme ActivePerl Change Log Install Notes Linux Solaris Windows ActivePerl Components Overview PPM Windows Specifics OLE Browser PerlScript Perl for ISAPI PerlEZ ActivePerl FAQ Introduction Availability & Install Using PPM Docs & Support Windows Specifics Perl for ISAPI Windows 9X/NT/2000 Quirks Web Server Config Web programming Programming Modules & Samples Embedding & Extending Using OLE with Perl Windows Scripting Active Server Pages Windows Script Host Windows Script ComponentsCore Perl Documentation
perl perlfaq perltoc perlbook perlsyn perldata perlop perlreftut perldsc perllol perllexwarn perldebug perlrun perlfunc perlopentut perlvar perlsub perlmod perlpod perlstyle perlmodlib perlmodinstall perltrap perlport perlsec perlref perlre perlform perllocale perlunicode perlboot perltoot perltootc perlobj perlbot perltie perlipc perlnumber perlfork perlthrtut perldiag perlfaq1 perlfaq2 perlfaq3 perlfaq4 perlfaq5 perlfaq6 perlfaq7 perlfaq8 perlfaq9 perlcompile perlembed perlxstut perlxs perlguts perlcall perlfilter perldbmfilter perlapi perlintern perlapio perltodo perlhack perlhist perldelta perl5005delta perl5004delta perlamiga perlcygwin perldos perlhpux perlmachten perlos2 perlos390 perlvms perlwin32Pragmas
attributes attrs autouse base blib bytes charnames constant diagnostics fields filetest integer less lib locale lwpcook open ops overload perllocal re sigtrap strict subs utf8 vars warningsLibraries
ActivePerl DocTools TOC RDF AnyDBM_File Archive Tar AutoLoader AutoSplit B Asmdata Assembler Bblock Bytecode C CC Debug Deparse Disassembler Lint Showlex Stackobj Terse Xref Benchmark Bundle LWP ByteLoader Carp Heavy CGI Apache Carp Cookie Fast Pretty Push Switch Class Struct Compress Zlib Config CPAN FirstTime Nox Cwd Data Dumper DB Devel DProf Peek SelfStubber Digest HMAC HMAC_MD5 HMAC_SHA1 MD2 MD5 SHA1 DirHandle Dumpvalue DynaLoader English Env Errno Exporter Heavy ExtUtils Command Embed Install Installed Liblist MakeMaker Manifest Miniperl Mkbootstrap Mksymlists MM_Cygwin MM_OS2 MM_Unix MM_VMS MM_Win32 Packlist testlib Fatal Fcntl File Basename CheckTree Compare Copy CounterFile DosGlob Find Glob Listing Path Spec Functions Mac OS2 Unix VMS Win32 stat FileCache FileHandle FindBin Font AFM Getopt Long Std HTML AsSubs Element Entities Filter Form FormatPS Formatter FormatText HeadParser LinkExtor Parse Parser TokeParser TreeBuilder HTTP Cookies Daemon Date Headers Util Message Negotiate Request Common Response Status I18N Collate IO Dir File Handle Pipe Poll Seekable Select Socket INET UNIX IPC Msg Open2 Open3 Semaphore SysV LWP Debug MediaTypes MemberMixin Protocol RobotUA Simple UserAgent Math BigFloat BigInt Complex Trig MD5 MIME Base64 QuotedPrint NDBM_File Net Cmd Config Domain DummyInetd FTP hostent libnetFAQ netent Netrc NNTP PH Ping POP3 protoent servent SMTP SNPP Time O ODBM_File Opcode Pod Checker Find Html InputObjects Man Parser ParseUtils Plainer Select Text Color Termcap Usage POSIX PPM SOAPClient SOAPServer Safe SDBM_File Search Dict SelectSaver SelfLoader SHA Shell SOAP Defs Envelope EnvelopeMaker GenericHashSerializer GenericInputStream GenericScalarSerializer Lite OutputStream Packager Parser Transport HTTP Apache CGI Client Server LOCAL MAILTO POP3 TCP TypeMapper Socket Symbol Sys Hostname Syslog Term ANSIColor Cap Complete ReadLine Test Harness Text Abbrev ParseWords Soundex Tabs Wrap Thread Queue Semaphore Signal Specific Tie Array Handle Hash RefHash Scalar SubstrHash Time gmtime Local localtime tm UDDI Lite UNIVERSAL URI data Escape file Heuristic ldap URL WithBase User grent pwent Win32 AuthenticateUser ChangeNotify Clipboard Console Event EventLog File FileSecurity Internet IPC Mutex NetAdmin NetResource ODBC OLE Const Enum NEWS NLS TPJ Variant PerfLib Pipe Process Registry Semaphore Service Sound TieRegistry Win32API File Net Registry WWW RobotRules AnyDBM_File XML Element Parser Expat PPD PPMConfig ValidatingElement XSLoader|
Filter::decrypt - template for a decrypt source filter |
NAME
Filter::decrypt - template for a decrypt source filter
SUPPORTED PLATFORMS
- Linux
- Solaris
- Windows
SYNOPSIS
use Filter::decrypt ;
DESCRIPTION
This is a sample decrypting source filter.
Although this is a fully functional source filter and it does implement a very simple decrypt algorithm, it is not intended to be used as it is supplied. Consider it to be a template which you can combine with a proper decryption algorithm to develop your own decryption filter.
WARNING
It is important to note that a decryption filter can never provide complete security against attack. At some point the parser within Perl needs to be able to scan the original decrypted source. That means that at some stage fragments of the source will exist in a memory buffer.
The best you can hope to achieve by decrypting your Perl source using a source filter is to make it impractical to crack.
Given that proviso, there are a number of things you can do to make life more difficult for the prospective cracker.
- Strip the Perl binary to remove all symbols.
- Build the decrypt extension using static linking. If the extension is provided as a dynamic module, there is nothing to stop someone from linking it at run time with a modified Perl binary.
-
Do not build Perl with
-DDEBUGGING. If you do then your source can be retrieved with the-Dpcommand line option.The sample filter contains logic to detect the
DEBUGGINGoption. - Do not build Perl with C debugging support enabled.
- Do not implement the decryption filter as a sub-process (like the cpp source filter). It is possible to peek into the pipe that connects to the sub-process.
- Do not use the decrypt filter as-is. The algorithm used in this filter has been purposefully left simple.
If you feel that the source filtering mechanism is not secure enough you could try using the unexec/undump method. See the Perl FAQ for further details.
AUTHOR
Paul Marquess
DATE
19th December 1995
|
Filter::decrypt - template for a decrypt source filter |