Tuesday, October 23, 2012

HP/H3C and Huawei SNMP Weak Access to Critical Data

HP/H3C and Huawei SNMP Weak Access to Critical Data

Overview

HP/H3C and Huawei networking equipment suffers from a serious weakness in regards to their handling of Systems Network Management Protocol (SNMP) requests for protected h3c-user.mib and hh3c-user.mib objects.

Identifiers


Vendor releases


Researcher

 Kurt Grutzmacher
 grutz <at> jingojango dot net
 twitter: @grutz

Details

Huawei/H3C have two OIDs, 'old' and 'new':
  •   old: 1.3.6.1.4.1.2011.10
  •   new: 1.3.6.1.4.1.25506
Most devices support both formats.

The MIBs h3c-user.mib and hh3c-user.mib, for the purpose of this document, will be referred to as (h)h3c-user.mib. This MIB defines the internal table and objects to "Manage configuration and Monitor running state for userlog feature."

This means there are some cool objects with data in this MIB penetration testers or malicious actors would want to get their dirty little hands on. Most objects are only accessible with the read/write community string.

In the revision history of (h)h3c-user.mib, version 2.0 modified the MAX-ACCESS from read-only to read-create the following objects within the (h)h3cUserInfoEntry sequence:
  •   (h)h3cUserName
  •   (h)h3cUserPassword
  •   (h)h3cAuthMode
  •   (h)h3cUserLevel
The purpose of these objects are to provide the locally configured users to those with a valid SNMP community. After the change only those with the read-write community string should have access, however this was not the case and the code still retained the earlier access of read-only.

So if you have the SNMP public community string then you have the ability to view these entries.

Why this is impactful

The (h)h3cUserPassword is presented in one of three formats as defined in the (h)h3cAuthMode object and mirrors how passwords are stored in the device configuration:
  •   0 -- password simple, meaning cleartext
  •   7 -- password cipher, meaning ciphertext
  •   9 -- password sha-256, meaning one-way sha-256 hash
SHA-256 is a recent addition and is not supported on all devices yet.

On top of this the (h)h3cUserLevel can be 0 to 3 where 0 is limited access and 3 is full access.

Globbing some users

You must have an SNMP read-only or read-write string and access to the
SNMP port (udp/161) for this to work:
 $ snmpwalk –c public –v 1 $IP 1.3.6.1.4.1.2011.10.2.12.1.1.1
or
 $ snmpwalk –c public –v 1 $IP 1.3.6.1.4.1.25506.2.12.1.1.1

Weaponizing

Files relevant to this disclosure:
  •   hh3c-localuser-enum.rb - Metasploit auxiliary scanner module
  •   snmp-h3c-login.nse - Nmap Scripting Engine module
These will soon be posted to https://github.com/grutz/h3c-pt-tools and requested to be added to each tool.

Mitigation

By itself this is already bad but most users who do any of the following may already be protected:
  • Use complex SNMP community strings or disable SNMPv1
  • Have disabled the mib entries for (h)h3c-user
  • Block SNMP using access controls or firewalls
  • Do not define local users, use RADIUS or TACACS+
More specific routines can be found in the vendor's release.

Why this is a bigger problem

People make poor choices. They like to think their equipment won't rat them out so they use cleartext passwords on networking equipment.

The cipher is an interesting one because it's basically an unknown... What, you think the only thing I had to share at Toorcon was SNMP and some cleartext credentials?

Timeline

June-ish 2012: Research begins after seeing something cool on a penetration test

August 6, 2012: Contacted US-CERT to coordinate vendor disclosure, VU#225404

September 5, 2012: No response from H3C, contacted US-CERT again

September 6, 2012: H3C (through US-CERT) requests more time, I state intention to present findings at Toorcon (Oct 19/20, 2012) or disclose if talk not accepted.

September 18, 2012: Approved for Toorcon! Information goes up not long after on Toorcon website.

September 18-October 16, 2012: Build slides, work on tools, no contact with US-CERT or vendors.

October 16, 2012: HP contacts me directly asking that I not present  this information at Toorcon

October 18, 2012: Publicly state agreement to cancel the Toorcon talk

October 22, 2012: HP discloses! What what? Why bother putting any pressure not to give the talk if you're gonna give everything out 2 days later?

October 23, 2012: So I publish.

1 comment:

Damon Schuartz said...

This is a really helpful way of putting it all together and explaining it in detail. Surely, enterprise network management tools are very much helpful in a speedy production for companies.