Re^2: One true regexp for untainting windows filenames?

It seems that despite the length of my post I still managed to leave out some pertinent information. Sorry! I use untaint_path() to check several filenames not just $^X. It just happens that this is the first test that encountered a weird path. So the question still stands even if $^X is safe.

On that topic, I am using the value of $^X in a qx// call. On Linux at least, if I don't untaint it, I get a nastygram about "insecure dependency." Should perl be a little smarter here?

As for the regexps themselves, I am embarrassed to say I just copied them from existing code. Now I will use the ones from File::Basename as cdarke suggested.

Thank you for your help.

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Comment on Re^2: One true regexp for untainting windows filenames?

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Re^3: One true regexp for untainting windows filenames? by ikegami (Patriarch) on Jan 09, 2009 at 05:14 UTC
I use untaint_path() to check several filenames not just $^X. To make them safe for what? Most most applications, `untaint_path` might remove the taint flag, but it doesn't make sure they're safe first. On that topic, I am using the value of $^X in a qx// call. On Linux at least, if I don't untaint it, I get a nastygram about "insecure dependency." Should perl be a little smarter here? In unix systems, it's possible to execute a binary at one path while making it think it's at a different path. `$ cat > a.c #include <stdio.h> int main(int argc, char** argv) { printf("%s\n", argv[0]); return 0; } $ gcc -o a a.c $ perl -e'exec { "a" } "evil"' evil` [download] Based on a comment in `$^X`, it looks like there's a way for processes to find out which binary is actually being executed on some systems, and Perl uses it. If the following doesn't print "`evil`" on your system, `$^X` can probably be trusted on your system. `$ perl -e'system { "perl" } "evil", "-le", "print \$^X"' /usr/bin/perl` [download]	[reply] [d/l] [select]
Re^4: One true regexp for untainting windows filenames? by jaldhar (Vicar) on Jan 09, 2009 at 19:42 UTC
To make them safe for what? Most most applications, untaint_path might remove the taint flag, but it doesn't make sure they're safe first. Safe to use in `qx//;` in taint mode Earlier, I set `$ENV{PATH}` to `q{}`. This means I need to use complete paths to every file or command I use and they need to be untainted to prevent the 'insecure dependency' error. I had forgotten about argv[0]. Now you have led me to realize that running under -T will not really buying me anything here without additional checking. Hopefully this conversation will remind others to not complacently assume untainted eq secure if nothing else. -- જલધર	[reply] [d/l] [select]
Re^5: One true regexp for untainting windows filenames? by ikegami (Patriarch) on Jan 09, 2009 at 19:59 UTC
Safe to use in qx//; in taint mode In such general terms, it's impossible. You can make it so `qx//` doesn't croak, but you can't make it safe. Need more info.	[reply] [d/l]


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