-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I reported the vulnerability below to the Pine team on Oct 21, when 4.20 was current. 4.21 (which I just noticed on freshmeat) seems to fix the problem even though it's not mentioned in the release notes. Since it's not, I thought some disclosure was in order. I built 4.21 in the same way I built 4.20 (below). Best, Jim Hebert - ---------- Forwarded message ---------- Date: Thu, 21 Oct 1999 03:40:27 -0400 (EDT) From: Jim Hebert To: pine@cac.washington.edu Subject: Security: expanding env vars in URLs 1 line summary: environment vars are expanded in URLs I try to view Versions tested: 4.10 and 4.20. 4.10 from "Red Hat" rpm and 4.20 built from pristine sources to slx build target. Both seem equally affected. Discussion: A certain mailing I get occasionally recently had a url like http://something/some/cgi$12345 I noticed viewing the url didn't seem to work right, and finally figured out that the url must get near enough to a shell to allow environment variable expansion. A quick test for me was: echo 'setenv WWW www.securityfocus.com' >> .tcshrc source .tcshrc pine (view a link I mailed myself like: http://$WWW ) it works, I visit securityfocus Doesn't sound dangerous/exploitable yet, right? Well, imagine your shell is bash, someone sends you a html formatted mail, and the url is long: "Click here for cool stuff!" the url is very long, long enough that the dangerous part is elided when pine asks the user to confirm they want to visit that page the url ends with something like: ?trojan=$(shell command) The user says "yeah, sure, visit that page" since they don't see the dangerous part. At the least least, people put your environment variables into their webserver access logs. At most, people can get you to run shell commands (bad enough by itself) _and_ have the output of them sent to them if they wish. I searched the bugtraq archives and didn't see anything about this. Sorry if it's a known issue. Thanks, jim jhebert@jhebert.cx -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.0 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE4Mzj9B1oRfeAiKDARAs7ZAJ9WpvdZ8aVLAl1N89dXl1mun1jFLQCeP8lq 2F6L+3uiYG63eOpgVv0ME5I= =Zj4l -----END PGP SIGNATURE----- Reply-To: Pavel Kankovsky An attempt was made to fix the vulnerability. An unsuccessful one. The following line in pine/mailview.c controls whether the quoting is done or not: if(strpbrk(handle->h.url.path, "&*;<>?[|~$") != NULL){ /* specials? */ It is obvious something is wrong: they try to explicitly list all harmful characters and we all know this is the "disaster pattern". It is left as an exercise for the reader for find at least two characters not included in the list that have special meaning for the shell. Special bonus for finding a character that is not on the list and has the power to defeat the effect of quoting (and I am not speaking about bash 1.x \377 bug, btw. it chokes on ``echo "$(echo '1`2')"'' as well...another good reason to get rid of it). If you need a hint, search the same function for the following line: sstrcpy(&cmdp, handle->h.url.path); Yes, I know, providing patches or pointing out the mistakes clearly might be more efficient but I hope Pine developers will get sick of their own code having no choice but to analyze it and will rewrite it from the scratch...and cleanly (for instance, they should use a single (reasonably safe) substitution procedure for mailcap and urls). --Pavel Kankovsky aka Peak [ Boycott Microsoft--http://www.vcnet.com/bms ] "Resistance is futile. Open your source code and prepare for assimilation."