Re: Strange file -i

[Stephane Chazelas]

2015-03-05 15:20:44 -0500, Chet Ramey:
[...]
> For example, I never do this:
> 
> > $ perl -ne 'print if /foo/' *
> 
> I just use grep directly.

That was just a basic example.

What about:

sed 's/foo/bar/g' *

?

> Or this:
> 
> > rm -- *
[...]

Then, you're in for some bad surprise some day.

You should definitely do that in scripts that you share with
others at least. Not doing it is introducing a security
vulnerability.

sed 's/foo/bar/' *

is OK with non-GNU seds, but with GNU sed (that accepts options
after arguments), it's an arbitrary command execution
vulnerability.

For instance if there's a file called 
-e1s:.*:uname>\&2:e (left there by another cheeky user, some
malware, a dodgy tarball (like bash's that contain a -i file
:-b))

sed s/foo/bar/ *

runs uname for every non-empty file in the directory.

-- 
Stephane