Bug 1197072

Summary: ssh client using HostbasedAuthentication aborts in FIPS mode
Product: Red Hat Enterprise Linux 6 Reporter: Stanislav Zidek <szidek>
Component: opensshAssignee: Jakub Jelen <jjelen>
Status: CLOSED ERRATA QA Contact: Stanislav Zidek <szidek>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.6CC: jjelen, plautrba
Target Milestone: rcKeywords: Patch
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: openssh-5.3p1-106.el6 Doc Type: Bug Fix
Doc Text:
Cause: ssh client is loading RSA1 keys that are not allowed to use in FIPS mode, if they exists. Consequence: ssh client crashes when trying to use disallowed hash. Fix: Do not load RSA1 keys in FIPS mode. Result: RSA1 keys are ignored in FIPS mode.
 Story Points: ---
Clone Of:
: 1197666 (view as bug list) Environment:
Last Closed: 2015-07-22 06:47:10 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: 1197666    
Attachments:
Description Flags
Patch that fixes the problem
none
proposed patch none

Description Stanislav Zidek 2015-02-27 13:04:49 UTC 
Created attachment 996028 [details]
Patch that fixes the problem

Description of problem:
ssh client aborts with HostbasedAuthentication fails if there is /etc/ssh/ssh_host_key present. This is somehow similar to bz1009959.

Version-Release number of selected component (if applicable):
openssh-5.3p1-105.el6

How reproducible:
always

Steps to Reproduce:
1. setup hostbased authentication for server
2. ssh -p 6296 -o PubkeyAuthentication=no -o BatchMode=yes -o HostbasedAuthentication=yes -v <USER>@<SERVER>

Actual results:
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
FIPS mode initialized
debug1: Connecting to sheep-29.lab.eng.brq.redhat.com [10.34.88.29] port 6296.
debug1: Connection established.
md5_dgst.c(78): OpenSSL internal error, assertion failed: Digest MD5 forbidden in FIPS mode!
Aborted (core dumped)

Expected results:
no core dump, authentication success

Additional info:
If I just remove /etc/ssh/ssh_host_key, everything works fine.

Configuration:

I am using same machine for both server and client for simplicity.
* add these lines to default /etc/ssh/sshd_config
HostbasedAuthentication yes
HostbasedUsesNameFromPacketOnly yes
IgnoreRhosts no
* add machine to global known_hosts
ssh-keyscan <HOSTNAME> >/etc/ssh/ssh_known_hosts
* add root to user's ~/.shosts file
# su - <USER> -c -c 'echo "<HOSTNAME> root" >.shosts; chmod 600 .shosts'

Backtrace:
(gdb) bt
#0  0x00007fb4b613e625 in raise () from /lib64/libc.so.6
#1  0x00007fb4b613fe05 in abort () from /lib64/libc.so.6
#2  0x00007fb4b7c25fbf in OpenSSLDie () from /usr/lib64/libcrypto.so.10
#3  0x00007fb4b7c2c729 in MD5_Init () from /usr/lib64/libcrypto.so.10
#4  0x00007fb4b860f85c in cipher_set_key_string (cc=0x7fff7c31a4d0, cipher=0x7fb4b884f4e0, 
    passphrase=0x7fb4b8640602 "", do_encrypt=0) at cipher.c:314
#5  0x00007fb4b8603a47 in key_load_private_rsa1 (fd=4, filename=0x7fb4b8631e2d "/etc/ssh/ssh_host_key", 
    passphrase=0x7fb4b8640602 "", commentp=0x0) at authfile.c:430
#6  0x00007fb4b85ee36a in main (ac=<value optimized out>, av=<value optimized out>) at ssh.c:829

I am attaching patch that solves problem for me.
Comment 1 Jakub Jelen 2015-03-01 19:30:30 UTC 
Created attachment 996817 [details]
proposed patch

This makes sense to me. We can't load RSA1 key in FIPS mode. Also sounds reasonable for RHEL-6.7.
But there is that comment "closes fd" so we should close fd as well even if we are in fips mode (as it is solved in your referenced bugzilla). Also we need to return and not to let it fallback into key_load_private_pem and generate errors

Unfortunately, I don't have FIPS machine around. Stanislav, can you try it with this patch?
Comment 2 Jakub Jelen 2015-03-02 10:53:14 UTC 
OK. Tested with rhel6 and it solves this issue for me.

This issue applies also for rhel7 in this border condition so I'm cloning bug to rhel7.
Comment 3 Stanislav Zidek 2015-03-02 12:28:45 UTC 
(In reply to Jakub Jelen from comment #1)
> Created attachment 996817 [details]
> proposed patch
> 
> Unfortunately, I don't have FIPS machine around. Stanislav, can you try it
> with this patch?

Jakub, your patch works as expected, solves the problem for me. Thanks!
Comment 6 errata-xmlrpc 2015-07-22 06:47:10 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://rhn.redhat.com/errata/RHBA-2015-1335.html