Patch to harden config.guess [was Re: Security vulnerability in automake]

[Lawrence Teo]

Here's a patch that I wrote to address that security "hole" in config.guess. 
I sent it to address@hidden on June 4, 2002 but have not heard from 
them since. The patch works with GNU config.guess 2002-05-29, available at 
ftp://ftp.gnu.org/pub/gnu/config/config.guess

The patch tries to ensure that config.guess will only produce non-existent 
dummy filenames. It generates dummy filenames by checking the existence of 
dummy-$$-n and dummy-$$-n.{c,o,rel,s}, where n=1 and keeps incrementing, 
until no such files exist.

This doesn't necessarily prevent the symlink attack, but I believe it'll 
harden config.guess signficantly. Also, I used this method instead of 
generating a random hash value because I think we can't assume that 
config.guess will always run on hosts with md5sum or cksum available.

I'm not an expert at portable Bourne shell scripting, and there may be other 
issues with the patch, so if possible, please let me know what you think. 
Thank you.

Lawrence

--
Lawrence Teo
lcteo at uncc dot edu
http://www.coe.uncc.edu/~lcteo

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