Bug 1602931 (CVE-2018-10903)

Summary:	CVE-2018-10903 python-cryptography: GCM tag forgery via truncated tag in finalize_with_tag API
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	apevec, bmcclain, cheimes, chrisw, dblechte, dfediuck, eedri, jjoyce, jschluet, kbasil, lhh, lpeer, markmc, mburns, mgoldboi, michal.skrivanek, npmccallum, rbryant, rhos-maint, sbonazzo, sclewis, sherold, slinaber, tdecacqu
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	python-cryptography 2.3	Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-06-10 10:33:26 UTC	Type:	---
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:	1602932, 1605040, 1605041, 1605042, 1607923
Bug Blocks:	1602933

Description Pedro Sampaio 2018-07-18 20:15:40 UTC

A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.

Upstream patch:

https://github.com/pyca/cryptography/pull/4342/commits/688e0f673bfbf43fa898994326c6877f00ab19ef

References:

https://bugzilla.redhat.com/show_bug.cgi?id=1602752

Comment 4 Joshua Padman 2018-07-20 04:07:29 UTC

The following OpenStack releases ship the vulnerable library. However, OpenStack does not appear to use the GCM mode.
Red Hat OpenStack 13
Red Hat OpenStack 14

Comment 5 Joshua Padman 2018-07-20 04:11:14 UTC

Created python-cryptography tracking bugs for this issue:

Affects: openstack-rdo [bug 1605041]

Comment 9 Alan Pevec 2018-07-25 14:41:55 UTC

(In reply to Pedro Yóssis Silva Barbosa from comment #8)
> RHEL7.5 ships version 1.7.2-2. Thus it is affected.

How come, description says >=1.9.0 and <2.3 ?

Comment 10 Pedro Yóssis Silva Barbosa 2018-07-28 18:37:27 UTC

Correction: RHEL7.5 ships version 1.7.2-2 and the finalize_with_tag method wasn't implemented in this version. Thus it is NOT affected. I am closing the rhel-7 tracker.

Comment 11 errata-xmlrpc 2018-11-13 22:13:18 UTC

This issue has been addressed in the following products:

  Red Hat OpenStack Platform 13.0 (Queens)

Via RHSA-2018:3600 https://access.redhat.com/errata/RHSA-2018:3600