Bug 1290292 (CVE-2015-5296)

Summary: CVE-2015-5296 samba: client requesting encryption vulnerable to downgrade attack
Product: [Other] Security Response Reporter: Huzaifa S. Sidhpurwala <huzaifas>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: aavati, asn, gdeschner, jrivera, jrusnack, nlevinki, rfortier, sbose, security-response-team, sgirijan, sisharma, slong, smohan, ssaha, vbellur
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: samba 4.1.22, samba 4.2.7, samba 4.3.3 Doc Type: Bug Fix
Doc Text:
A man-in-the-middle vulnerability was found in the way "connection signing" was implemented by Samba. A remote attacker could use this flaw to downgrade an existing Samba client connection and force the use of plain text.
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-01-08 12:19:30 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: 1290706, 1290707, 1290708, 1290709, 1290710, 1290711, 1290727, 1292069    
Bug Blocks: 1281327    

Description Huzaifa S. Sidhpurwala 2015-12-10 05:29:52 UTC
As per upstream samba advisory:

Versions of Samba from 3.2.0 to 4.3.2 inclusive do not ensure that signing is negotiated when creating an encrypted client connection to
a server.

Without this a man-in-the-middle attack could downgrade the connection and connect using the supplied credentials as an unsigned, unencrypted
connection.

The following mitigation was suggested by upstream:


When using the smbclient command, always add the argument "--signing=required" when using the "-e" or "--encrypt" argument.

Alternatively, set the variable "client signing = mandatory" in the [global] section of the smb.conf file on any client using encrypted connections.

To protect a Samba server exporting encrypted shares against a downgrade attack set the variable "smb encrypt = mandatory" in the smb.conf definition of the encrypted shares.

Comment 1 Huzaifa S. Sidhpurwala 2015-12-10 06:34:11 UTC
Acknowledgements:

Red Hat would like to thank the Samba project for reporting this issue. Upstream acknowledges Stefan Metzmacher of the Samba Team and Sernet.de as the original reporters.

Comment 5 Siddharth Sharma 2015-12-16 12:09:14 UTC
Created samba tracking bugs for this issue:

Affects: fedora-all [bug 1292069]

Comment 6 Huzaifa S. Sidhpurwala 2015-12-17 04:12:27 UTC
External References:

https://www.samba.org/samba/security/CVE-2015-5296.html

Comment 8 errata-xmlrpc 2016-01-07 17:07:00 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2016:0010 https://rhn.redhat.com/errata/RHSA-2016-0010.html

Comment 9 errata-xmlrpc 2016-01-07 17:23:21 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2016:0011 https://rhn.redhat.com/errata/RHSA-2016-0011.html

Comment 10 errata-xmlrpc 2016-01-08 01:40:31 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2016:0006 https://rhn.redhat.com/errata/RHSA-2016-0006.html

Comment 11 errata-xmlrpc 2016-01-08 10:19:12 UTC
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.1 for RHEL 7

Via RHSA-2016:0016 https://rhn.redhat.com/errata/RHSA-2016-0016.html

Comment 12 errata-xmlrpc 2016-01-08 10:19:56 UTC
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.1 for RHEL 6

Via RHSA-2016:0015 https://rhn.redhat.com/errata/RHSA-2016-0015.html