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Re: Security techniques every programmer should know

by eyepopslikeamosquito (Bishop)
on Dec 29, 2004 at 02:06 UTC ( #417902=note: print w/replies, xml ) Need Help??

in reply to Security techniques every programmer should know

Writing secure programs. Wow, that's a huge topic. Where to start? :-)

I suppose with some basic Perl references. The Camel Chapter 23 "Security" provides an excellent (and much more detailed than perlsec) overview of fundamental Perl security issues. This chapter is broken into: Handling Insecure Data, Cleaning Up Your Environment, Accessing Commands and Files Under Reduced Privileges, Handling Timing Glitches (Unix Kernel Security Bugs, Race Conditions, Temporary Files), Handling Insecure Code (Safe module, Code Masquerading as Data).

The Perl Cookbook has recipes: 8.17 (Testing a File for Trustworthiness), 19.4 (Writing a Safe CGI Program), 19.5 (Executing Commands Without Shell Escapes).

Can anyone comment on how safe is the Safe module? Sorry, I've not used it, though it is described in the Camel. Update: apparently it's not safe according to considered unsafe?.

The venerable suidperl has apparently had all known insecurities plugged by Paul Szabo in Perl 5.8.4. However, "For new projects the core perl team would strongly recommend that you use dedicated, single purpose security tools such as sudo in preference to suidperl" (perl584delta).

Which leads me to an important general piece of security advice (simplifying outrageously): Keep up-to-date with the latest version of perl. Well, that's a bit over the top; keep an eye on security alerts and perldelta security bug fixes and upgrade your perl judiciously. Apart from Paul's heroic suidperl fixes, security bugs are being squashed all the time. For example, perl 5.8 introduced Hash Randomisation and ensuring that sort never goes O(n-squared). Despite these two important denial-of-service (DoS) improvements, Perl regular expressions remain a concern for DoS attacks, it being easy to write (and hard to detect) a regular expression that finishes after the heat death of the universe.

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