Integer signedness error in the pamStrTok function in libpam/pammisc.c in Linux-PAM (aka pam) 1.0.3 and earlier, when a configuration file contains non-ASCII usernames, might allow remote attackers to cause a denial of service, and might allow remote authenticated users to obtain login access with a different user's non-ASCII username, via a login attempt.

An issue dealing with password changes, with respect to the MINDAYS field in /etc/shadow was reported on the Debian BTS (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514437) that affects all versions of PAM 1.x. Because of this, if an administrative user sets the password minimum days via chage or passwd, /etc/shadow is updated correctly, but PAM allows the user to change their password with no regard for the MINDAYS setting, effectively allowing them to re-use old passwords immediately and disregard any established password policies that should be enforced.

This is due to the fact that no minimum age password checks are done by PAM in 1.x; in the old versions it was done in unixverifyshadow() by checking the value of of spmin. In newer PAM this check is no longer there.

The pamsmclosesession function in pamxauth.c in the pamxauth module in Linux-PAM (aka pam) 1.1.2 and earlier does not properly handle a failure to determine a certain target uid, which might allow local users to delete unintended files by executing a program that relies on the pamxauth PAM check.

The checkacl function in pamxauth.c in the pamxauth module in Linux-PAM (aka pam) 1.1.2 and earlier does not verify that a certain ACL file is a regular file, which might allow local users to cause a denial of service (resource consumption) via a special file.

The pamenv module in Linux-PAM (aka pam) 1.1.2 and earlier reads the .pamenvironment file in a user's home directory, which might allow local users to run programs with an unintended environment by executing a program that relies on the pamenv PAM check.

It was reported that pamenv and pammail modules do not drop privileges before accessing users' files. This flaw can lead to information disclosure.

Issue was partially addressed in Linux-PAM 1.1.2: http://git.altlinux.org/people/ldv/packages/?p=pam.git;a=commitdiff;h=06f882f30092a39a1db867c9744b2ca8d60e4ad6

The fix in 1.1.2 has some problems though, it fails to switch fsgid/egid and groups (CVE-2010-3430) and does not check setfsuid() return value (CVE-2010-3431): http://thread.gmane.org/gmane.comp.security.oss.general/3311/focus=3551

Fix using newly-introduced pammodutildroppriv / pammodutilregainpriv was committed in upstream CVS and should be included in 1.1.3: http://git.altlinux.org/people/ldv/packages/?p=pam.git;a=commitdiff;h=843807a3a90f52e7538be756616510730a24739a

Acknowledgements:

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting this issue.