Bug 799928

Summary:	[RFE] Hash the hostname/port information in the known_hosts file.
Product:	Red Hat Enterprise Linux 6	Reporter:	Stephen Gallagher <sgallagh>
Component:	sssd	Assignee:	Jakub Hrozek <jhrozek>
Status:	CLOSED ERRATA	QA Contact:	Kaushik Banerjee <kbanerje>
Severity:	unspecified	Docs Contact:
Priority:	high
Version:	6.3	CC:	grajaiya, jgalipea, prc, spoore
Target Milestone:	rc	Keywords:	FutureFeature
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	sssd-1.9.1-1.el6	Doc Type:	Enhancement
Doc Text:	Do not document	Story Points:	---
Clone Of:		Environment:
Last Closed:	2013-02-21 09:20:13 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:

Description Stephen Gallagher 2012-03-05 12:48:45 UTC

This bug is created as a clone of upstream ticket:
https://fedorahosted.org/sssd/ticket/1203

Last week I discussed the SSH known_hosts work with Honza. I thought about the stuff on the weekend. The plan is to have a global known_hosts file which gets written by sssd. This means that all users on this system have access which means reveal information to a lot of people who might not have this detailed information. So the hostnames should be stored hashed in the known_hosts file.

This way they do not reveal identifying information should the file's contents be disclosed. OpenSSH supports hashing since quite some time now.

Normally it looks like this:
{{{
|1|dTVaYG/giqH3nvoLfGECyOsiMDs=|RzAc9qu1lG+3ZtajFbaVuL02SZA= ssh-rsa ...
|1|base64(salt)|base64(hash)|
}}}
Here is some pseudo code for comparing it:

{{{
match_hashed_host(hostname, sourcehash) {

salt = base64_decode(sourcehash + 3)
hash = base64_decode(sourehash + strlen(salthash))

mac = sha1_hmac(hostname, salt)

if (mac == hash)
  woohoo
else
  cry
}
}}}

Comment 1 RHEL Program Management 2012-07-10 07:06:42 UTC

This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.

Comment 2 RHEL Program Management 2012-07-11 02:04:46 UTC

This request was erroneously removed from consideration in Red Hat Enterprise Linux 6.4, which is currently under development.  This request will be evaluated for inclusion in Red Hat Enterprise Linux 6.4.

Comment 5 Scott Poore 2012-11-28 16:12:56 UTC

Verified.

Version ::

sssd-1.9.2-21.el6.x86_64

Manual Test Results ::

[root@rhel6-1 log]# ssh rhel6-1.testrelm.com
root.com's password: 
Last login: Wed Nov 28 08:45:45 2012 from 192.168.122.1

[root@rhel6-1 ~]# exit
logout
Connection to rhel6-1.testrelm.com closed.

[root@rhel6-1 log]# ssh-keygen -H -F rhel6-1.testrelm.com -f /var/lib/sss/pubconf/known_hosts 
# Host rhel6-1.testrelm.com found: line 3 type RSA
|1|jzhcKuywO/syrzxU7BjbXAIa/kM=|RznFNMi4cWBK8/LXEdx2CqlCbSw= ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAxes4L818CAuJFLTL0MOwKaL6IbG92Mx3orn0ceOvz8OlWZ3VJADiBIXC9GdDTFEzJIqP5EW/WWb7hgbjBJ0h9zmD7onxgXZj+J9m28REl1ut03KldBYcBZPGyhYs+sKRCLSp1R5BT6laoq5rYxnQuDwCa8oljhnaCpBnWu9t7le3cfXmJfWfbnCFNB5FCPc/UDL/QwuLBiq0QNoRrjOgJqygtZ7EMP3csrYB/UxkNCvycGbZ6xg49HAcci064Ek6wz5GYD7/yFQB5bqvK1cAUkLjlL5m8Osw+McU+Z/aFz/5QfDHaEJ/krlCM8HPjEYv35CG0cYt1fHQKgYARxGMqw==
# Host rhel6-1.testrelm.com found: line 4 type DSA
|1|+/qqOvsp0eYFPHyUddi+YYn5XLs=|6nvBL7cSakbCOuXZXq5smAZ70qg= ssh-dss AAAAB3NzaC1kc3MAAACBAOVwCsdmy76rq7NeRhKWzvoMFhTu4jjaDcOUi1RIJujR0MbncFaZMK2oVR4hIu/Br19ZqSFz55DurlQRpxw0RLcv3AQS4OWXu5zgMvDHK/87f0J8PlatSzNOmLNrVJZAiYe8LdhuXfd5Cz2o+LjxQ/j0YnHyg9KjJ8hY3HOFqYGVAAAAFQCTDM0w6dGWA8SGtSxVIR/CYOFyawAAAIEA04PQf1JF1HkPkfr/xRsMWPBKZvIsX5tD54Y64Pakc/A4oTKxFjTlW/Z3i62Rwx4g7VCFsjbabXJ/CvLq+zZsuqJEU8kny6Sk0SQ+ky4rbPj0zatzM8uQKFpeuY+103fKp/pn5AUUTGgCK5nf5o4lwiR4enDVG3Tp7DjOWDNkfUwAAACACpDqLiyaC+dFIaBl5tAXbEf2PieEZ6Q7wEtCAQ2IsiRGFjsXzqZYo/qZk9gWkieClVofGlSdhbyZGbBFx9Q8t/yaNFbsqB09RCzgRxlQGqgltKMEtYok9IpzegcWgkPP0VT/KGcrvTfeccLOFyCucLMpYIHs2n9QvHUEgqz2CaQ=

[root@rhel6-1 log]# knownhost="$(ssh-keygen -H -F rhel6-1.testrelm.com -f /var/lib/sss/pubconf/known_hosts |grep ssh-rsa)"

[root@rhel6-1 log]# hostname=$(hostname)

[root@rhel6-1 log]# key=$(echo ${knownhost:3:28} | base64 -d | xxd -ps)

[root@rhel6-1 log]# mac1=$(echo ${knownhost:32:28} | base64 -d | xxd -ps)

[root@rhel6-1 log]# mac2=$(echo -n $hostname | openssl dgst -sha1 -mac HMAC -macopt hexkey:$key | awk '{ print $2 }')

[root@rhel6-1 log]# [ $mac1 = $mac2 ] && echo 'Keys match'
Keys match

Comment 6 errata-xmlrpc 2013-02-21 09:20:13 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.

http://rhn.redhat.com/errata/RHSA-2013-0508.html