This document discusses common security issues in Perl web applications and provides recommendations to address them. It covers input validation, SQL injections, cross-site scripting (XSS), cookies, CSRF, path traversal, Perl-specific issues like buffer overflows, tainting, system calls, eval, CGI parameters, regular expressions, and randomness. The document recommends using secure Perl modules from CPAN, following best practices, and using web scanners to test for vulnerabilities.

1. Security issues in Perl web apps
Viacheslav Tykhanovskyi
May 12, 2012

3. Common web security issues

4. Validate input data!

5. SQL injections
use DBI;
use DBIx::Class;
use Rose::DB::Object;
use ObjectDB;

6. XSS
Blind escaping <, >, ’, " and & is not enough!

7. XSS
Blind escaping <, >, ’, " and & is not enough!
Various HTML attributes (href, refresh meta
tag, ...)

8. XSS
Blind escaping <, >, ’, " and & is not enough!
Various HTML attributes (href, refresh meta
tag, ...)
Not validated JSON response

9. XSS
Blind escaping <, >, ’, " and & is not enough!
Various HTML attributes (href, refresh meta
tag, ...)
Not validated JSON response
Using template variables in JavaScript code

10. XSS
Blind escaping <, >, ’, " and & is not enough!
Various HTML attributes (href, refresh meta
tag, ...)
Not validated JSON response
Using template variables in JavaScript code
Escape taking context into account.

11. Cookies
Sign cookies

12. Cookies
Sign cookies
XSS preventing is hard. Set HttpOnly cookie
flag for better protection.

13. CSRF
Plack::Middleware::CSRF

14. Path traversal
../../../../../../etc/passwd

15. Path traversal
../../../../../../etc/passwd
Detect ..

16. Path traversal
../../../../../../etc/passwd
Detect ..
File::Spec->no_upwards(@paths);

17. Perl-specific security issues

18. No buffer overflow

19. No buffer overflow
Most system commands are embedded

20. No buffer overflow
Most system commands are embedded
Written by smart people

22. use strict;
use warnings;

23. Tainting
-T

24. sub is_tainted {
return !eval {
eval("#"
. substr(join("", @_), 0, 0)
);
1
};
}

25. system()
system("program $arg");
vs
system(’program’, $arg);

26. open()
open my $fh, ">$file";
vs
open my $fh, ’>’, $file;

27. eval()
eval "require $class";

28. eval()
eval "require $class";
load_class("Foo;print ’nice feature!’")

29. 0
0

30. 0
0
$file = "/bin/ls0 /etc|";
if (-e $file) {
open my $fh, $file;
}

31. CGI & ARGV
script.pl?foo

32. CGI & ARGV
script.pl?foo
...
$app->run(@ARGV);
...

33. Regular expressions
if ($string =~ m/$user_supplied_re/) {
...
}
vs
if ($string =~ m/Q$user_supplied_reE/) {
...
}

34. Unicode
utf8
vs
UTF-8

35. rand()
”rand()” is not cryptographically secure

36. How to make life easier?

37. How to make life easier?
Use modules from CPAN. Many of them are
time-proved

38. How to make life easier?
Use modules from CPAN. Many of them are
time-proved
Google ”OWASP”

39. How to make life easier?
Use modules from CPAN. Many of them are
time-proved
Google ”OWASP”
Follow Best Practices

40. How to make life easier?
Use modules from CPAN. Many of them are
time-proved
Google ”OWASP”
Follow Best Practices
Use scanners
nikto http://cirt.net/nikto2
skipfish http://code.google.com/p/skipfish/
w3af http://w3af.sourceforge.net/

41. Questions?