-----BEGIN PGP SIGNED MESSAGE----- MIT krb5 Security Advisory 2004-004 Original release: 2004-12-20 Topic: heap buffer overflow in libkadm5srv Severity: serious SUMMARY ======= The MIT Kerberos 5 administration library (libkadm5srv) contains a heap buffer overflow in password history handling code which could be exploited to execute arbitrary code on a Key Distribution Center (KDC) host. The overflow occurs during a password change of a principal with a certain password history state. An administrator must have performed a certain password policy change in order to create the vulnerable state. (See MITIGATING FACTORS below.) No exploits are known to exist at this time, though a public discussion of the bug took place during the first weeks of December 2004, containing sufficient detail that someone could infer how to perform an attack. Exploitation of this vulnerability is believed to be difficult, due to the limited extent of the overflow. IMPACT ====== An authenticated user, not necessarily one with administrative privileges, could execute arbitrary code on the KDC host, compromising an entire Kerberos realm. [CAN-2004-1189] MITIGATING FACTORS ================== * Typically, only a principal satisfying the following conditions can trigger the buffer overflow upon password change: + have changed its password fewer times than the history count in its password policy + had its password policy's history count subsequently reduced to equal the number of times it has changed its password * There are other means of producing the vulnerable state, though they are significantly more complex and much less likely. All of these other methods involve a reduction of the password history count in a password policy. * A workaround exists (see FIXES). AFFECTED SOFTWARE ================= * KDC software on all releases of MIT krb5, up to and including krb5-1.3.5. The vulnerable library is libkadm5srv. Programs which use the vulnerable functionality of the library include: + kadmind (administration daemon) + kadmin.local (KDC-local administration client) + kadmind4 (krb4 compatibility administration daemon) FIXES ===== * WORKAROUND: Until your KDC programs and libraries have been patched, do not decrease the password history count on any policy in your Kerberos realm. Also, if you have already decreased the password history count on a policy at some point in the past, you should raise it to the maximum value that it has had in the past. * The upcoming krb5-1.4 release (currently in beta test) will contain fixes for this problem. The krb5-1.4-beta3 release contains fixes for this problem. * The upcoming krb5-1.3.6 patch release contains fixes for this problem. * Apply the following patch to src/lib/kadm5/srv/svr_principal.c, and recompile the affected libraries and binaries. This patch was generated against krb5-1.3.5, and may apply, with some offset, to earlier releases. This patch may also be found at: http://web.mit.edu/kerberos/advisories/2004-004-patch_1.3.5.txt The associated detached PGP signature is at: http://web.mit.edu/kerberos/advisories/2004-004-patch_1.3.5.txt.asc Index: svr_principal.c =================================================================== RCS file: /cvs/krbdev/krb5/src/lib/kadm5/srv/svr_principal.c,v retrieving revision 1.26.2.1 diff -c -r1.26.2.1 svr_principal.c *** svr_principal.c 2 Sep 2003 18:58:56 -0000 1.26.2.1 - --- svr_principal.c 20 Dec 2004 19:47:29 -0000 *************** *** 1017,1022 **** - --- 1017,1025 ---- memset(&adb->old_keys[adb->old_key_len],0,sizeof(osa_pw_hist_ent)); adb->old_key_len++; + for (i = adb->old_key_len - 1; i > adb->old_key_next; i--) + adb->old_keys[i] = adb->old_keys[i - 1]; + memset(&adb->old_keys[adb->old_key_next],0,sizeof(osa_pw_hist_ent)); } else if (adb->old_key_len > pol->pw_history_num-1) { /* * The policy must have changed! Shrink the array. *************** *** 1039,1048 **** histp[i] = adb->old_keys[j]; } /* Now free the ones we don't keep (the oldest ones) */ ! for (i = 0; i < adb->old_key_len - (pol->pw_history_num - 1); i++) for (j = 0; j < adb->old_keys[KADM_MOD(i)].n_key_data; j++) krb5_free_key_data_contents(context, &adb->old_keys[KADM_MOD(i)].key_data[j]); free((void *)adb->old_keys); adb->old_keys = histp; adb->old_key_len = pol->pw_history_num - 1; - --- 1042,1053 ---- histp[i] = adb->old_keys[j]; } /* Now free the ones we don't keep (the oldest ones) */ ! for (i = 0; i < adb->old_key_len - (pol->pw_history_num-1); i++) { for (j = 0; j < adb->old_keys[KADM_MOD(i)].n_key_data; j++) krb5_free_key_data_contents(context, &adb->old_keys[KADM_MOD(i)].key_data[j]); + free(adb->old_keys[KADM_MOD(i)].key_data); + } free((void *)adb->old_keys); adb->old_keys = histp; adb->old_key_len = pol->pw_history_num - 1; *************** *** 1052,1061 **** - --- 1057,1070 ---- } } + if (adb->old_key_next + 1 > adb->old_key_len) + adb->old_key_next = 0; + /* free the old pw history entry if it contains data */ histp = &adb->old_keys[adb->old_key_next]; for (i = 0; i < histp->n_key_data; i++) krb5_free_key_data_contents(context, &histp->key_data[i]); + free(histp->key_data); /* store the new entry */ adb->old_keys[adb->old_key_next] = *pw; REFERENCES ========== This announcement and related security advisories may be found on the MIT Kerberos security advisory page at: http://web.mit.edu/kerberos/advisories/index.html The main MIT Kerberos web page is at: http://web.mit.edu/kerberos/index.html CERT VU#948033: http://www.kb.cert.org/vuls/id/948033 CVE CAN-2004-1189: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-1189 Administration library in MIT Kerberos 5 release krb5-1.3.5 and earlier has a heap buffer overflow in code which handles password history, possibly allowing authenticated attackers to execute arbitrary code on a KDC host. ACKNOWLEDGMENTS =============== Thanks to Michael Tautschnig for reporting this problem. Thanks to Chaskiel Grundman and Luke Howard for providing debugging help on the mailing list. DETAILS ======= The vulnerable function is add_to_history() in src/lib/kadm5/srv/svr_principal.c. The password history is stored as a ring buffer, represented as an array of osa_pw_ent_rec, which is adb->old_keys. The "next" pointer is an index into the array, adb->old_key_next, and the length of the array is stored in adb->old_key_len. The array is dynamically resized as needed, and there is no separate head pointer. The policy's history count is stored in pol->pw_hist_num, but the actual maximum number of keys stored in adb->old_keys is pol->pw_hist_num-1, since the "current" key data are also used for history comparisons when a password change occurs. The index value adb->old_key_next is permitted to index to a position one past the end of the array adb->old_keys if adb->old_key_next is less than pol->pw_hist_num-1. This out-of-bounds indexing is usually fixed up when add_to_history() enlarges the array on a subsequent call. If pol->pw_hist_num is reduced to adb->old_key_next after a password change that causes adb->old_key_next to index out of bounds, a subsequent password change will not run the resizing code, and add_to_history() will write a password history entry past the end of the array adb->old_keys. REVISION HISTORY ================ 2004-12-20 original release Copyright (C) 2004 Massachusetts Institute of Technology -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (SunOS) iQCVAwUBQcdAH6bDgE/zdoE9AQEWogQAy7vS1GLO5gG/uX9rm15NUQEO5K07NaMu MdwZhITIR0tg5aIR2eecon1ahgdDFrZELnZ3G/+ArhLqH+yvmskmOLZGmRHQ9Q0l mMf4DbOWMQZgGNmbvTTAzg0GAuVYdw2+5acP7maj61O0nV9mQIOdeM7Y0HFj46QL EVf4jR0OsJY= =ZAwT -----END PGP SIGNATURE-----
aliz, rphillips, please provide an updated ebuild with the patches
*** Bug 74449 has been marked as a duplicate of this bug. ***
rphillips/aliz: This is nasty, please patch it asap
mit-krb5 1.3.6 has been released. This security bug has been fixed. We should *really* upgrade. http://web.mit.edu/kerberos/www/krb5-1.3/
Version 1.3.6 has been commited. Arches need to test and unmask. -r
Thx Ryan. Arches please test and mark stable.
I get this on ppc64: --- SNIP --- checking for socket... yes checking if DNS Kerberos lookup support should be compiled in... yes checking for res_search... no checking for res_search in -lresolv... no configure: error: Cannot find resolver support routine res_search in -lresolv. !!! ERROR: app-crypt/mit-krb5-1.3.6 failed. !!! Function econf, Line 449, Exitcode 1 !!! econf failed --- SNIP --- Markus
Markus: can you try the previous stable one (1.3.4-r1) and see if it compiles right ? Just to be sure we're dealing with a regression here, not a missing dep that has always been missing.
1.3.4-r1 compiles and works for me.
sparc stable.
Markus: Can you try this: http://groups-beta.google.com/group/linux.debian.bugs.dist/browse_thread/thread/9539854ad48787eb/2bbdf3b27d08cc87?q=%22configure:+error:+Cannot+find+resolver+support+routine+res_search+in+-lresolv.%22&_done=%2Fgroups%3Fq%3D%22configure:+error:+Cannot+find+resolver+support+routine+res_search+in+-lresolv.%22%26hl%3Den%26lr%3D%26c2coff%3D1%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN%26tab%3Dwg%26&_doneTitle=Back+to+Search&&d#2bbdf3b27d08cc87
same result... :-(
Stable on mips.
Created attachment 47192 [details, diff] mit-krb5-1.3.6-ppc64.patch I'm sorry. I first regenerated the configure scripts and then applied the patch.. Of cause this has to be the other way around. Now it works. Here is the patch. This should be tested on other archs, too. If it works, I'll add it arch independend. otherwise I have to use "use ppc64 && patch ..."
Stable on alpha.
Markus: given that other arches tested without the patch and reported success maybe it's better not to force them to test a new version. I think the best way to handle this is to submit a 1.3.6-r1 as "~* ppc64" with the patch in "use ppc64 &&"-style and mark it stable on ppc64. Another way of doing it if you feel the patch is useful for everyone is to have it "-* ppc64" with the patch applied to all arches. They will test it in time and unmask -r1 for them if it works, but we can still issue the GLSA as unaffected: >=1.3.6
I've added 1.3.6-r1 and applied the ppc64 using "use ppc64 && .." Markus
amd64 also needs -r1, so i changed the name of the patch and changed use ppc64 && to 64-bit &&. it's stable now on amd64
Patch file for 64bit should be called: files/mit-krb5-1.3.6-64-bit.patch as stated in ebuild, but actually is files/mit-krb5-1.3.6-64bit.patch
arm/hppa/ia64/s390 stable also fixed 64 bit patch name
It compiles on ppc. But is it normal that ktelnet quits with a segmentation fault? So, it's not masked stable yet.
sorry for the delay.... x86 stable and happy new year..
stable on ppc
Thx everyone closing with GLSA 200501-05
