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Bug 1788196

Summary: sudo allows privilege escalation with expire password
Product: Red Hat Enterprise Linux 7 Reporter: Carl Thompson <fedora>
Component: sudoAssignee: Radovan Sroka <rsroka>
Status: CLOSED ERRATA QA Contact: Dalibor Pospíšil <dapospis>
Severity: high Docs Contact:
Priority: medium    
Version: 7.8CC: dapospis, huzaifas, tjaros
Target Milestone: rcKeywords: AutoVerified, Security
Target Release: ---   
Hardware: Unspecified   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: No Doc Update
Doc Text:
Story Points: ---
Clone Of:
: 1815164 (view as bug list) Environment:
Last Closed: 2020-09-29 19:56:45 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1815164    
Attachments:
Description Flags
proposed patch1
none
proposed patch2 none

Description Carl Thompson 2020-01-06 16:55:58 UTC 
Description of problem:
sudo allows privilege escalation with expired passwords

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Have a user configured for sudo privileges
2. Have user with expired (not locked) password
3. Sudo to elevate privileges.  It will prompt for password but you do not need to change.
4. sudo again and you will be cached and have sudo access without change password

Actual results:
Allows privilege escalation with expired password

Expected results:
Deny privilege escalation until password is changed

Additional info:
upstream fix is in place:  https://bugzilla.sudo.ws/show_bug.cgi?id=910
Comment 2 Huzaifa S. Sidhpurwala 2020-01-29 08:06:54 UTC 
Carl,

Are you able to reproduce this on rhel-8 or fedora. It seems like RHEL/Fedora has a PAM configuration which blocks users with expired passwords from logging, Can you pls confirm?
Comment 3 Carl Thompson 2020-01-30 16:34:58 UTC 
I have not tested this on a RHEL 8 system.  It does not affect RHEL 6 because of code changes between 6 and 7 in sudo.

We ran into this issue when utilizing LDAP.  Sudo privileges configured locally.  The sudo caches the expired password as valid and prompts for a password change.  However, if you cancel out of password change dialog and simply run sudo again the cached validation of the expired password is enough to allow escalation, not prompting for password change again.
Comment 6 Huzaifa S. Sidhpurwala 2020-02-05 05:29:00 UTC 
(In reply to Carl Thompson from comment #3)
> I have not tested this on a RHEL 8 system.  It does not affect RHEL 6
> because of code changes between 6 and 7 in sudo.
> 
> We ran into this issue when utilizing LDAP.  Sudo privileges configured
> locally.  The sudo caches the expired password as valid and prompts for a
> password change.  However, if you cancel out of password change dialog and
> simply run sudo again the cached validation of the expired password is
> enough to allow escalation, not prompting for password change again.

It seems like this issue was introduced via cab448ac8633 which was released via sudo-1.8.23, so rhel-7/8 may be affected. We are still trying to reproduce this issue here.
Comment 8 Huzaifa S. Sidhpurwala 2020-02-07 04:40:03 UTC 
(In reply to Carl Thompson from comment #3)
> I have not tested this on a RHEL 8 system.  It does not affect RHEL 6
> because of code changes between 6 and 7 in sudo.
> 
> We ran into this issue when utilizing LDAP.  Sudo privileges configured
> locally.  The sudo caches the expired password as valid and prompts for a
> password change.  However, if you cancel out of password change dialog and
> simply run sudo again the cached validation of the expired password is
> enough to allow escalation, not prompting for password change again.

Hi Carl,

We tested this on rhel-6/7/8 and we could not reproduce this on any of the platforms with standard PAM configuration shipped with stock RHEL. It seems that though the bug may exist in sudo, the PAM configurations shipped with RHEL stop the flaw from manifesting. Could you share your configurations you use (PAM etc) so that we can try to reproduce this at our end?

Thanks!
Comment 9 Carl Thompson 2020-02-17 15:20:56 UTC 
I know we have seen this in our systems here.  As soon as I get a chance I will setup a complete environment that is easy for you to duplicate with instructions on how I have it setup to attempt to duplicate this.

I will be utilizing FreeIPA for LDAP and test against RHEL 6/7/8
Comment 11 Radovan Sroka 2020-03-19 16:50:01 UTC 
Created attachment 1671514 [details]
proposed patch1
Comment 12 Radovan Sroka 2020-03-19 16:50:41 UTC 
Created attachment 1671515 [details]
proposed patch2
Comment 19 errata-xmlrpc 2020-09-29 19:56:45 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (sudo bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:3930