Bug 1216057 (CVE-2015-3420)

Summary:	CVE-2015-3420 dovecot: SSL/TLS handshake failures leading to a crash of the login process.
Product:	[Other] Security Response	Reporter:	Martin Prpič <mprpic>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	carnil, janfrode, mhlavink
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	dovecot 2.2.17	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-04-29 15:28:40 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:	1216059
Bug Blocks:	1216058

Description Martin Prpič 2015-04-28 12:26:24 UTC

A flaw was found in the way Dovecot handled SSL handshake failures. A remote attacker could use this flaw to crash the imap-login
and pop3-login processes.

Note that only Dovecot installations accepting SSL/TLS connections that have SSLv3 disabled are vulnerable.

Additional details:

http://dovecot.org/pipermail/dovecot/2015-April/100618.html
http://seclists.org/oss-sec/2015/q2/288

Upstream patch:

http://hg.dovecot.org/dovecot-2.2/rev/86f535375750

Comment 1 Martin Prpič 2015-04-28 12:28:41 UTC

Created dovecot tracking bugs for this issue:

Affects: fedora-all [bug 1216059]

Comment 2 Stefan Cornelius 2015-04-29 15:18:05 UTC

Steps to reproduce, taken from http://dovecot.org/pipermail/dovecot/2015-April/100618.html:

Add to config: ssl_protocols = !SSLv2 !SSLv3
Run: openssl s_client -ssl3 -connect localhost:995

It looks like the following commit introduced the described behaviour (not confirmed):
http://hg.dovecot.org/dovecot-2.2/diff/09d3c9c6f0ad/src/login-common/ssl-proxy-openssl.c

Our RHEL versions do not have this change. Fedora has this in the source, but I still was not able to trigger a crash. It's possible that our OpenSSL versions handle this situation more gracefully, but I didn't investigate that.

Comment 3 Stefan Cornelius 2015-04-29 15:28:40 UTC

Statement:

This issue did not affect the versions of dovecot as shipped with Red Hat Enterprise Linux 5, 6, and 7.