------------------------------------------------------------------------ ------- Title : Majordomo info leakage (all versions) Date : 03/02/2003 Article by : Marco van Berkum (m.v.berkum (at) obit (dot) nl [email concealed]) Bug finder : Jakub Klausa (jacke (at) bofh (dot) pl [email concealed]) Investigated by : Jakub Klausa and Marco van Berkum ------------------------------------------------------------------------ ------- Introduction: -------------- Some while ago Jakub Klausa mailed me about a problem regarding the Majordomo mailinglist program. At first we were not sure if it was a one time problem or a common issue, so we checked several other servers and installed Majordomo ourselves and found ALL Majordomo versions to be vulnerable, also the latest Majordomo 2 (alpha). The problem: --------------- All email addresses can be extracted from mailinglists for which 'which_access' is set to "open" in the configuration file, which_access is set to "open" by default !! Majordomo 1.94.5 documentation quote: "8. By default, anyone (even non-subscribers) can use the commands "who", "which", "index", and "get" on a list. If you create an empty file named "listname.private" in the $listdir directory, only members of the list can use those commands." Typical case of RTFDOC of course, but still, why isn't the private configuration file the default one (?!), now people actually have to read the documentation to protect their lists against evil spammers. We all know that admins do not always read the docs (uhuh). So this bug can be exploited without being subscribed to any mailinglist on that server when "which_access" is set to open. This bug can be exploited by sending: which @ or which . To the Majordomo daemon. Majordomo will then match "@" (or ".") on all the mailinglists that have 'which_access' set to "open". This then matches all email addresses that are subscribed to that list. There is a slight difference between the new Majordomo 2 (alpha) and the current Majordomo 1.94.x branch. Majordomo 1.94.x gives output such as this: >>>> which @ The string '@' appears in the following entries in lists served by majordomo (at) somedomain (dot) com [email concealed]: List Address ==== ======= test-list user (at) somedomain (dot) com [email concealed] test-list anotheruser (at) anotherdomain (dot) com [email concealed] another-list satan (at) evilmajordomodomain (dot) net [email concealed] another-list bush (at) sopranos (dot) org [email concealed] etc... Majordomo 2 also has the bug, not as much as the 1.94.x though: >>>> which @ The pattern "/\@/i" matched the following subscriptions. Matches for the devils mailing list: satan (at) majordomo (dot) org [email concealed] -- Match limit of 1 for devils exceeded. Matches for the britney mailing list: eminem (at) spears (dot) net [email concealed] -- Match limit of 1 for britney exceeded. Impact: ------- High. Not only privacy is the issue here, this bug could be used by evil spammers to fill their databases. And the users did much of their work for them already, as the victims are usually well targeted (subject-specific mailinglists come to mind). Solution: --------- general: Read the documentation regarding $listname.private and set all which_access to "closed", or update to Majordomo 2 alpha, which still requires the same attention. Majordomo 1.94.5 and earlier: As mentioned by the documentation that comes with Majordomo 1.94.5, create an empty file named "$listname.private" in the $listdir. It will only reduce the group of people being able to pick up all the addresses to the ones subscribed to the list. Check your current configurations for open which_access, close them. Majordomo 2: The authors responded quickly and changed default configuration settings to be "closed". Get the latest CVS version, and check your current configurations for open which_access, which_access should be closed at any time. Jakub made a patch for Majordomo 1.94.5. [Patch] This is a patch for Majordomo 1.94.5, which makes the Majordomo ignore the 'which' request if they don't contain e-mail address-like string as a parameter (roughly). --- majordomo.orig Mon Feb 3 13:23:45 2003 +++ majordomo Mon Feb 3 13:23:23 2003 @@ -624,6 +624,11 @@ sub do_which { local($subscriber) = join(" ", @_) || &valid_addr($reply_to); + if ($subscriber !~ /^[0-9a-zA-Z\.\-\_]+\@[0-9a-zA-Z\.\-]+\.[a-zA-Z]{2,3}$/) { + + &log("which abuse -> $subscriber passed as an argument."); + exit(0); + }; local($count, $per_list_hits) = 0; # Tell the requestor which lists they are on by reading through all # the lists, comparing their address to each address from each list Cheers Marco van Berkum / http://ws.obit.nl / m.v.berkum (at) obit (dot) nl [email concealed] Jakub Klausa / jacke (at) bofh (dot) pl [email concealed] -- find / -user your -name base -exec chown us:us {}\; ---------------------------------------- | Marco van Berkum / MB17300-RIPE | | m.v.berkum (at) obit (dot) nl [email concealed] / http://ws.obit.nl | ----------------------------------------