Bug 42103

Summary: root password is hashed with MD5
Product: UCS Reporter: Michael Grandjean <grandjean>
Component: PAMAssignee: Florian Best <best>
Status: CLOSED FIXED QA Contact: Stefan Gohmann <gohmann>
Severity: normal    
Priority: P5 CC: best, gohmann
Version: UCS 4.1   
Target Milestone: UCS 4.1-3-errata   
Hardware: Other   
OS: Linux   
What kind of report is it?: Security Issue What type of bug is this?: ---
Who will be affected by this bug?: --- How will those affected feel about the bug?: ---
User Pain: Enterprise Customer affected?: Yes
School Customer affected?: ISV affected?:
Waiting Support: Flags outvoted (downgraded) after PO Review:
Ticket number: Bug group (optional): API change, Security
Max CVSS v3 score:
Attachments: Replace md5 with sha512, remove nullok, min, max

Description Michael Grandjean univentionstaff 2016-08-23 22:59:38 CEST 
UCS 4.1-3 errata 237

Expected behaviour:
The UCRV "password/hashing/method" specifies "SHA-512" as default hashing method for all passwords.

Observed behaviour:
"password/hashing/method" is only valid for LDAP users. For local users (such as "root") we still use MD5 (or md5crypt iirc):

> root@ucs-2920:~# less /etc/shadow | grep root
> root:$1$F5qxj2Hh$kVYT3gvF2GFpC3CGAFAAQ/:17036:0:99999:7:::

"$1$" indicates MD5 / md5crypt as hashing method.

Possible solution:
AFAIK /etc/pam.d/common-password is responsible for this:
> password        [success=2 default=ignore]      pam_unix.so nullok obscure md5 min=4 max=32 try_first_pass use_authtok

We should replace 'md5' with 'sha512'.
I also think we should remove 'nullok', because empty root passwords don't seem acceptable to me. The 'min' and 'max' settings seem outdated as they have no effect: I can ignore the warnings and set a root password with only 1 character (or one with 35 characters) nevertheless.

The default Debian Wheezy config uses this:
> password        [success=2 default=ignore]      pam_unix.so obscure use_authtok try_first_pass sha512
Comment 1 Michael Grandjean univentionstaff 2016-08-23 23:02:14 CEST 
Created attachment 7919 [details]
Replace md5 with sha512, remove nullok, min, max
Comment 2 Florian Best univentionstaff 2016-08-24 11:57:30 CEST 
On my UCS 4.1 system my root password is not hashed with MD5 but with SHA-512. Which tool did you use to change the root password?
Comment 3 Florian Best univentionstaff 2016-08-24 12:01:50 CEST 
(In reply to Florian Best from comment #2)
> On my UCS 4.1 system my root password is not hashed with MD5 but with
> SHA-512. Which tool did you use to change the root password?
Ah okay, I could reproduce this with the following python script:

import PAM
auth = PAM.pam()
auth.start('univention-management-console')
auth.chauthtok()
Comment 4 Florian Best univentionstaff 2016-10-14 14:01:36 CEST 
All relevant pam configuration files:
grep -l pam_unix $(find $(find -name pam.d -type d) -type f)

* Removed min and max parameter as don't exists (/aren't documented). Default minlen is 6.
* Changed MD5 to SHA512
* Removed nullok

From pam_unix manpage:
nullok: The default action of this module is to not permit the user access to a service if their official password is blank. The nullok argument overrides this default and allows any user with a blank password to access the service.

So after this change it's not possible to change the password anymore if it is empty. I don't know which side effects this can have. We will see tomorrow if the jenkins tests fail if e.g. system-setup tries to use this when initially setting the password for root. Michael/The security auditors wants this change. It's also the debian default.

univention-ldap (12.1.6-40):
r73236 | Bug #42103: enhance pam_unix password change configuration
r73235 | Bug #42103: enhance pam_unix password change configuration

univention-ldap.yaml:
r73236 | Bug #42103: enhance pam_unix password change configuration

univention-pam (9.0.0-7):
r73236 | Bug #42103: enhance pam_unix password change configuration
r73235 | Bug #42103: enhance pam_unix password change configuration

univention-management-console (8.0.28-19):
r73236 | Bug #42103: enhance pam_unix password change configuration
r73235 | Bug #42103: enhance pam_unix password change configuration

univention-pam.yaml:
r73236 | Bug #42103: enhance pam_unix password change configuration

univention-management-console.yaml:
r73236 | Bug #42103: enhance pam_unix password change configuration

Merge to UCS 4.2:
univention-ldap (13.0.0-11):
r73238 | Bug #42103: enhance pam_unix password change configuration
r73237 | Bug #42103: enhance pam_unix password change configuration

univention-management-console (9.0.12-24):
r73238 | Bug #42103: enhance pam_unix password change configuration
r73237 | Bug #42103: enhance pam_unix password change configuration

univention-pam (10.0.0-2):
r73238 | Bug #42103: enhance pam_unix password change configuration
r73237 | Bug #42103: enhance pam_unix password change configuration
Comment 5 Florian Best univentionstaff 2016-10-14 14:09:02 CEST 
univention-pam (9.0.0-8):
r73239 | Bug #42103: adjust pseudo tests
Comment 6 Stefan Gohmann univentionstaff 2016-10-19 11:20:08 CEST 
Tests: OK, the new hashes are SHA 256

Code review: OK

Merge to 4.2: OK

YAML: OK