Bug 1357859 – guest_t can run sudo

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Bug 1357859 - guest_t can run sudo

Summary:	guest_t can run sudo

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	openssh (Show other bugs)
Sub Component:
Version:	7.3
Hardware:	All Linux

Priority	high Severity high
Target Milestone:	rc
Target Release:	---
Assigned To:	Jakub Jelen
QA Contact:	Stefan Kremen
Docs Contact:

URL:
Whiteboard:
Keywords:

Depends On:	1356245 1357857 1357860
Blocks:	1376826 1378463
	Show dependency tree / graph

Reported:	2016-07-19 08:21 EDT by Lukas Vrabec
Modified:	2016-11-03 16:20 EDT (History)
CC List:	15 users (show)

See Also:
Fixed In Version:	openssh-6.6.1p1-29.el7
Doc Type:	If docs needed, set a value
Doc Text:
Story Points:	---
Clone Of:	1357857
Clones:	1376826 (view as bug list)
Environment:
Last Closed:	2016-11-03 16:20:29 EDT
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
proposed patch for openssh (drop suid early, retain SYS_CHROOT, fallback to old behavior) (3.12 KB, patch) 2016-07-20 07:16 EDT, Jakub Jelen	no flags	Details \| Diff
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2016:2588	normal	SHIPPED_LIVE	Moderate: openssh security, bug fix, and enhancement update	2016-11-03 08:09:45 EDT

Groups: None (edit)

Comment 2 Jakub Jelen 2016-07-20 07:16 EDT

Created attachment 1182040 [details]
proposed patch for openssh (drop suid early, retain SYS_CHROOT, fallback to old behavior)

See the comment #7 in the bug #1356245 for the changes need to the policy.

Comment 7 Jakub Jelen 2016-08-02 02:05:48 EDT

It looks like Lukas didn't actually add the setcap rule, only the setpcap, as it looks from the linked diff. And to the SSH client policy?

> + # SSH client local policy
> ++allow ssh_t self:capability { setpcap setuid setgid dac_override dac_read_search };

Shouldn't it come to the  sshd_t  as explained in the above mentioned comment?

Comment 12 Jakub Jelen 2016-09-14 04:16:30 EDT

Stefan,
this is expected behavior. The issue was that the  guest_u  could run the sudo when the boolean  selinuxuser_use_ssh_chroot  was enabled. Reading the  /etc/shadow  is out of the scope of this bug. It was just an arbitrary operation requiring superuser privileges.

AFAIK, there was no real exploit (Simon, Lukas, correct me if I am wrong), because the context of  guest_u  didn't allow to progress much further from sudo, but mitigating even the ability to start sudo was the intention of this bug (removing setuid, setgid permissions from the confined users and handling the chroot in ssh using linux capabilities).

Comment 13 Stefan Kremen 2016-09-14 05:57:07 EDT

Thanks Jakub for explanation.

Comment 16 errata-xmlrpc 2016-11-03 16:20:29 EDT

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, 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://rhn.redhat.com/errata/RHSA-2016-2588.html

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