Starting with commit Linux-PAM-0-77-28-g0b3e583 that introduced hashed passwords support in pam_userdb, hashes are compared case-insensitively. This bug leads to accepting hashes for completely different passwords in addition to those that should be accepted. Additionally, commit Linux-PAM-1_1_6-13-ge2a8187 that added support for modern password hashes with different lengths and settings, did not update the hash comparison accordingly, which leads to accepting computed hashes longer than stored hashes when the latter is a prefix of the former. * modules/pam_userdb/pam_userdb.c (user_lookup): Reject the computed hash whose length differs from the stored hash length. Compare computed and stored hashes case-sensitively. Fixes CVE-2013-7041. Bug-Debian: http://bugs.debian.org/731368 --- I'm not an advocate for keeping pam_userdb in the tree, but while it's in the tree, these bugs have to be fixed. modules/pam_userdb/pam_userdb.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/modules/pam_userdb/pam_userdb.c b/modules/pam_userdb/pam_userdb.c index de8b5b1..ff040e6 100644 --- a/modules/pam_userdb/pam_userdb.c +++ b/modules/pam_userdb/pam_userdb.c @@ -222,12 +222,15 @@ user_lookup (pam_handle_t *pamh, const char *database, const char *cryptmode, } else { cryptpw = crypt (pass, data.dptr); - if (cryptpw) { - compare = strncasecmp (data.dptr, cryptpw, data.dsize); + if (cryptpw && strlen(cryptpw) == (size_t)data.dsize) { + compare = memcmp(data.dptr, cryptpw, data.dsize); } else { compare = -2; if (ctrl & PAM_DEBUG_ARG) { - pam_syslog(pamh, LOG_INFO, "crypt() returned NULL"); + if (cryptpw) + pam_syslog(pamh, LOG_INFO, "lengths of computed and stored hashes differ"); + else + pam_syslog(pamh, LOG_INFO, "crypt() returned NULL"); } }; -- ldv