Comment 6 for bug 67141

I do set GREP_OPTIONS in my .bashrc, etc. Specifically, I use GREP_OPTIONS=--color=auto

It is a common command someone might set. Either one off (just to see color for some greps) or routinely (like I have in my bashrc).

It is a security issue because it open up holes, prevent actions from happening, etc. if a grep doesn't return what the user expects.

For example:
---------------------------
$ grep -E -q local /etc/hosts ; echo $?
0

$ env GREP_OPTIONS=-P grep -E -q local /etc/hosts ; echo $?
grep: conflicting matchers specified
2

$ env GREP_OPTIONS=-f/dev/zero grep -E -q local /etc/hosts ; echo $?
grep: memory exhausted
1
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Just for a few examples of how this can go wrong, maliciously or otherwise.

GREP_OPTIONS can be used to read in files (-f) or change the meaning of a grep (illegal options) or otherwise corrupt it's usage in a script.

The fact that a tool that is usually used without considering how it could fail is used everyplace is the problem. I suggest just add something to /lib/lsb/init-functions to unset GREP_OPTIONS.

I don't have a specific security hole in mind, but something like a firewall going down might try to turn off packet forwarding, but think it's already down and leave it up. Or something like that.

Ciao!