Potential security hazard, be careful

If you use any session manager that uses Data::Dumper like CGI::Session does, then remember that Data::Dumper is not writing out simple data and then reading it back in. Data::Dumper writes out Perl code that is evaluated when you de-serialize your data. That means that if anybody has an opportunity to mess with your data files while they are sitting on the file system then you have a huge potential security risk.

If you use Data::Dumper, be absolutely certain that nobody has write access to the data files that should not. I really don't like to use Data::Dumper for anything in CGI, partly for that reason and partly because it's just slow. You might want to look at using FreezeThaw. It's pure Perl so it doesn't require anything special, but it writes and reads data blocks instead of Perl code.

Comment on Potential security hazard, be careful

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Re: Potential security hazard, be careful by Aristotle (Chancellor) on Sep 06, 2002 at 04:42 UTC
This can be avoided using the Safe module. Build the compartment to evaluate the Perl-code configuration using `$compartment = new Safe; $compartment->permit_only(qw(:base_core :base_mem)); # very restrictiv +e $result = $compartment->reval($unsafe_code);` [download] and the evaluated code will not be able to do anything than build data structures. (See `perldoc Opcode` for a list of tags.) Makeshifts last the longest.	[reply] [d/l]

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Re: Potential security hazard, be careful
by Aristotle (Chancellor) on Sep 06, 2002 at 04:42 UTC

Safe

$compartment = new Safe;
$compartment->permit_only(qw(:base_core :base_mem)); # very restrictiv
+e
$result = $compartment->reval($unsafe_code);
[download]

perldoc Opcode

Makeshifts last the longest.

[reply]
[d/l]