Bug 1725721

Summary:	SSLContext.post_handshake_auth implicitly enables cert validation
Product:	Red Hat Enterprise Linux 8	Reporter:	Christian Heimes <cheimes>
Component:	python3	Assignee:	Python Maintainers <python-maint>
Status:	CLOSED ERRATA	QA Contact:	Lukáš Zachar <lzachar>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	8.1	CC:	cstratak, jkejda, pviktori, torsava
Target Milestone:	rc
Target Release:	8.0
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	python3-3.6.8-13.el8	Doc Type:	Bug Fix
Doc Text:	Cause: Enabling TLS 1.3 post handshake authentication also enables cert chain validation implicitly on the client side, even though the SSL_VERIFY_POST_HANDSHAKE flag is supposed to be ignored by openssl on the client side. Consequence: SSL/TLS connections can fail with a cert validation error. Fix: SSLContext.post_handshake_auth = True no longer sets SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Result: SSL/TLS connections do not fail with a cert validation error when verify mode is set to CERT_NONE.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-11-05 22:03:44 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:	1726743

Description Christian Heimes 2019-07-01 10:18:21 UTC

Description of problem:
Enabling TLS 1.3 post handshake auth also enables cert chain validation. OpenSSL documents SSL_VERIFY_POST_HANDSHAKE as ignored for client side. However tls_process_server_certificate in the client state machine code does not ignore the flag and checks for a correct cert chain.

see https://github.com/openssl/openssl/issues/9259 and https://github.com/openssl/openssl/blob/743694a6c29e5a6387819523fad5e3b7e613f1ee/ssl/statem/statem_clnt.c#L1899-L1918

Version-Release number of selected component (if applicable):
python3-3.6.8-11.el8

How reproducible:
always

Steps to Reproduce:
See test case https://github.com/python/cpython/blob/fc1fbe6099e826e8304eadf781af7c10d739fc40/Lib/test/test_ssl.py#L4437-L4466

Actual results:
SSL/TLS connection fails with cert validation error

Expected results:
SSL/TLS connection should not fail with a cert validation error when verify mode is set to CERT_NONE

Additional info:

Comment 2 Tomas Orsava 2019-08-28 15:52:00 UTC

Hi Charris,
could you please add a doc type/text here?

Comment 6 errata-xmlrpc 2019-11-05 22:03:44 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, 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/RHSA-2019:3520