In article <20030729210308.15518.qmailat_private> on chiark.mail.bugtraq, Vade 79 wrote: [...] Thank you for reporting these vulnerabilities in man-db. However, I'm disappointed that you neither informed me a little beforehand so that I wasn't taken by surprise by your BugTraq post (preferable), nor sent a copy of your report to me as the maintainer of man-db (which I would regard as the minimum of common courtesy). Fortunately, a friend brought your post to my attention this morning so that I could begin preparing patches, a little later than I would otherwise have been able to do. Please inform the maintainer in future. The BugTraq guidelines suggest a one-week notice period, although in fact I'd personally have been happy with a few days. >[part 1: add_to_dirlist() buffer overflow] > >man-db contains a buffer overflow vulnerability do to the lack of bounds >checking in multiple sscanf() calls. which formats the user supplied file >~/.manpath. [...] >as you can see; MANDATORY_MANPATH, MANPATH_MAP, and MANDB_MAP do not >properly limit the value written to key[50], and/or cont[512]). however, >as far as exploitation by overflowing those buffers goes is limited. this >is do to the way the buffers are allocated in memory, so when >overwritten, will just overwrite into another character buffer. > >but, this is not all in vain. do to the size of buf[BUFSIZE], which is >8192 bytes(standard), and what key/cont overwrites into. you can pass >enormously long values(~8192) to other functions. as most checks are done >before-hand, and almost all buffers in the program are allocated to 4095 >bytes; you can make the overflow occur, in many locations, elsewhere in >the program. I've fixed the sscanf() invocations so that these arrays aren't overflowed. Other PATH_MAX-sized buffers will take a little more work, but I'll look at them. >[part 2: ult_src() buffer overflow] > >man-db contains a buffer overflow vulnerability do to the size of a buffer >being half the size it should be(doesn't follow the 4096 trend), for a >"path". Fixed by allocating this buffer dynamically instead. >[part 3: ".so" link buffer overflow] > >man-db contains a buffer overflow vulnerability do to the lack of bounds >checking for ".so" link/redirection manpages. this occurs when the >function attempts to change memory, without re-calculating the >size. Fixed in the process of fixing part 2 above, by causing the function in question to return a newly allocated string rather than doing that grotty hack of writing into a string allocated elsewhere without reallocation. >[part 4: PATH/MANPATH argument overflow] > >man-db contains a buffer overflow vulnerability do to the lack of bounds >checking for the amount PATH/MANPATH values given. the bug is found in >multiple routines. > >proof/to test for vulnerability existence: ># man -M `perl -e 'print"/tmp:"x260'` x >Segmentation fault On my machine it seems to require 432 elements or more, but anyway. I've applied a stopgap measure for now, namely to check whether the number of elements in MANPATH is going to overflow the list holding them. I'll add proper dynamically resized arrays later when I have a little more time. These fixes are in savannah.nongnu.org CVS for now; I'll prepare a release for Debian unstable tonight and if possible Debian stable as well. A full 2.4.2 release will have to wait a little longer, but should be within the week. Cheers, -- Colin Watson [cjwatsonat_private]
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