Bug 1926227

Summary:	CVE-2020-36242 python-cryptography: certain sequences of update() calls when symmetrically encrypting very large payloads could result in an integer overflow and lead to buffer overflows [fedora-all]
Product:	[Fedora] Fedora	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	python-cryptography	Assignee:	Christian Heimes <cheimes>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	33	CC:	cheimes, itamar, jeremy, nick, npmccallum, terrycwk1994
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	python-cryptography-3.2.1-2.fc33	Doc Type:	No Doc Update
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-02-12 01:42:18 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:
Bug Blocks:	1926226

Description Guilherme de Almeida Suckevicz 2021-02-08 13:21:35 UTC

This is an automatically created tracking bug!  It was created to ensure
that one or more security vulnerabilities are fixed in affected versions
of fedora-all.

For comments that are specific to the vulnerability please use bugs filed
against the "Security Response" product referenced in the "Blocks" field.

For more information see:
http://fedoraproject.org/wiki/Security/TrackingBugs

When submitting as an update, use the fedpkg template provided in the next
comment(s).  This will include the bug IDs of this tracking bug as well as
the relevant top-level CVE bugs.

Please also mention the CVE IDs being fixed in the RPM changelog and the
fedpkg commit message.

NOTE: this issue affects multiple supported versions of Fedora. While only
one tracking bug has been filed, please correct all affected versions at
the same time.  If you need to fix the versions independent of each other,
you may clone this bug as appropriate.

Comment 1 Guilherme de Almeida Suckevicz 2021-02-08 13:21:37 UTC

Use the following template to for the 'fedpkg update' request to submit an
update for this issue as it contains the top-level parent bug(s) as well as
this tracking bug.  This will ensure that all associated bugs get updated
when new packages are pushed to stable.

=====

# bugfix, security, enhancement, newpackage (required)
type=security

# low, medium, high, urgent (required)
severity=medium

# testing, stable
request=testing

# Bug numbers: 1234,9876
bugs=1926226,1926227

# Description of your update
notes=Security fix for [PUT CVEs HERE]

# Enable request automation based on the stable/unstable karma thresholds
autokarma=True
stable_karma=3
unstable_karma=-3

# Automatically close bugs when this marked as stable
close_bugs=True

# Suggest that users restart after update
suggest_reboot=False

======

Additionally, you may opt to use the bodhi web interface to submit updates:

https://bodhi.fedoraproject.org/updates/new

Comment 2 Christian Heimes 2021-02-08 14:01:16 UTC

The fix is trivial: https://github.com/pyca/cryptography/pull/5748

diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
index 2b10681b31..0f96795fdc 100644
--- a/src/cryptography/hazmat/backends/openssl/ciphers.py
+++ b/src/cryptography/hazmat/backends/openssl/ciphers.py
@@ -16,7 +16,7 @@
 class _CipherContext(object):
     _ENCRYPT = 1
     _DECRYPT = 0
-    _MAX_CHUNK_SIZE = 2 ** 31 - 1
+    _MAX_CHUNK_SIZE = 2 ** 30 - 1
 
     def __init__(self, backend, cipher, mode, operation):
         self._backend = backend

Comment 3 Fedora Update System 2021-02-08 14:55:30 UTC

FEDORA-2021-8e36e7ed1a has been submitted as an update to Fedora 33. https://bodhi.fedoraproject.org/updates/FEDORA-2021-8e36e7ed1a

Comment 4 Fedora Update System 2021-02-09 01:26:38 UTC

FEDORA-2021-8e36e7ed1a has been pushed to the Fedora 33 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --advisory=FEDORA-2021-8e36e7ed1a`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2021-8e36e7ed1a

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 5 Fedora Update System 2021-02-12 01:42:18 UTC

FEDORA-2021-8e36e7ed1a has been pushed to the Fedora 33 stable repository.
If problem still persists, please make note of it in this bug report.