Review Request 111261: [KDE-Workspace]: Possible NULL ptr. deref. in KDM and KCheckPass

mancha mancha mancha1 at
Thu Jun 27 19:05:54 BST 2013

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(Updated June 27, 2013, 6:05 p.m.)

Review request for kde-workspace.


1) Addressed Oswald's observations.
2) Digital UNIX C2 security's dispcrypt() can return NULL so I added protection for osf1c2crypt() as suggested by Michael. 


Beginning with glibc 2.17 (eglibc 2.17), crypt() fails with EINVAL (w/ NULL return) if the salt violates specifications. Additionally, on FIPS-140 enabled Linux systems, DES or MD5 encrypted passwords passed to crypt() fail with EPERM (w/ NULL return).

If KDM uses raw crypt() authentication (or pw_encrypt() on a patched Shadow system; see: ), instead of higher-level authentication such as PAM, and that crypt() can return a NULL pointer (as glibc 2.17+ does when passed a DES/MD5 encrypted passwords on Linux systems in FIPS-140 mode), then attempting to login to such an account via KDM crashes the daemon.

kdm[1879]: segfault at 0 ip b74a1909 sp bfd209d4 error 4 in[b7421000+186000]
kdm[1841]: Unknown session exit code 0 (sig 11) from manager process

Likewise, KCheckPass, when called in a similar scenario as KDM above, or when attempting to pass invalid input to crypt()/pw_encrypt() such as a "locked" account that has a "!" prepended in the password field, will crash.

kcheckpass[1927]: segfault at 0 ip b762b910 sp bffb0494 error 4 in[b75ab000+186000]

Note: an earlier (and buggy) patch was emailed directly to ML (not via RR). Please disregard that submission entirely.

Diffs (updated)

  kcheckpass/checkpass_etcpasswd.c 1dbe06f 
  kcheckpass/checkpass_osfc2passwd.c 9a074f9 
  kcheckpass/checkpass_shadow.c ec3a4e0 
  kdm/backend/client.c bdff6da 



Tests conducted on KDE-Workspace 4.10.4 confirm attached patch corrects the issues described above. Before applying the patch, KDM and KCheckPass segfault as shown in log snippets above. After applying the patch, both properly handle NULL returns from crypt() and pw_encrypt().


mancha mancha

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