Advisory ID:               SYSS-2022-005
Product:                   Store 'n' Go Secure Portable HDD
Manufacturer:              Verbatim
Affected Version(s):       GD25LK01-3637-C VER4.0
Tested Version(s):         GD25LK01-3637-C VER4.0
Vulnerability Type:        Use of a Cryptographic Primitive with a Risky
                            Implementation (CWE-1240)
Risk Level:                High
Solution Status:           Open
Manufacturer Notification: 2022-01-31
Solution Date:             -
Public Disclosure:         2022-06-08
CVE Reference:             CVE-2022-28384
Author of Advisory:        Matthias Deeg (SySS GmbH)

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Overview:

The Verbatim Store 'n' Go Secure Portable HDD is a portable USB drive
with AES 256-bit hardware encryption and a built-in keypad for passcode
entry.

The manufacturer describes the product as follows:

"The AES 256-bit Hardware Encryption seamlessly encrypts all data on the
drive in real-time with a built-in keypad for password input. The SSD
does not store passwords in the computer or system's volatile memory
making it far more secure than software encryption. Also, if it falls
into the wrong hands, the SSD will lock and require re-formatting after
20 failed password attempts." [1]

Due to an insecure design, the Verbatim Store 'n' Go Secure Portable HDD
is vulnerable to an offline brute-force attack for finding out the
correct passcode, and thus gaining unauthorized access to the stored
encrypted data.

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Vulnerability Details:

When analyzing the external SSD Verbatim Store 'n' Go Secure Portable
HDD, Matthias Deeg found out it uses an insecure design which allows for
offline brute-force attacks against the passcode.

The device consists of following four main parts:

1. a Toshiba SSD (MQ04ABF100)
2. an USB-to-SATA bridge controller (INIC-3637EN)
3. a SPI flash memory chip (XT25F01D) containing the firmware of the
    INIC-3637EN
4. a keypad controller (unknown chip, marked "SW611 2121")

For encrypting the data stored on the SSD, the hardware AES engine of
the INIC-3637EN is used. More specifically, AES-256 in ECB (Electronic
Codebook) mode is used for data encryption, which is also a security
issue by itself described in SySS security advisory SYSS-2022-002 [2].

The cryptographic key for the actual data encryption, the so-called data
encryption key (DEK) is stored in a special sector of the SSD which in
turn is encrypted using AES-256-ECB with a so-called key encryption key
(KEK).

This KEK is derived from the entered passcode which can be between five
and twelve digits long, and generated by the keypad controller.

When the unlock button is pressed on the Verbatim Store 'n' Go Secure
Portable HDD, this generated AES 256-bit key is transmitted via SPI
communication from the keypad controller to the USB-to-SATA bridge
controller INIC-3637EN for configuring the corresponding hardware AES
engine.

For verifying the entered passcode, the firmware of the INIC-3637EN
reads and decrypts the special sector on the SSD with the provided KEK,
and checks specific data offsets for the known byte pattern (signature)
"0x20 0x49 0x4E 0x49" which represents the string " INI".

If this byte pattern could successfully be found, the entered passcode
and its derived AES key is very likely correct, and enables the firmware
access to the decrypted DEK, which can then be used to decrypt the
actual SSD user data.

This described design of the Verbatim Store 'n' Go Secure Portable HDD
allows for offline brute-force attacks for finding the correct passcode.
Because an attacker can generate and observe the derived AES keys (KEK)
of the keypad for all possible passcodes, and then try to correctly
decrypt the data of specific SSD sector. If the magic byte pattern
" INI" can be found in the expected places of the resulting plaintext,
the correct passcode was found, which then allows for gaining
unauthorized access to the encrypted user data.

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Proof of Concept (PoC):

For demonstrating the offline brute-force attack, Matthias Deeg
developed a sample brute-forcing software tool which checks the complete
search space of all possible passcodes between 5 and 12 digits.

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Solution:

SySS GmbH is not aware of a solution for the described security issue.

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Disclosure Timeline:

2022-01-31: Vulnerability reported to manufacturer
2022-02-11: Vulnerability reported to manufacturer again
2022-03-07: Vulnerability reported to manufacturer again
2022-06-08: Public release of security advisory

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References:

[1] Product website for Verbatim Store 'n' Go Secure Portable HDD
 
https://www.verbatim-europe.co.uk/en/prod/store-n-go-portable-ssd-with-keypad-access-256gb-53402/
[2] SySS Security Advisory SYSS-2022-006
 
https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2022-006.txt
[3] SySS Security Advisory SYSS-2022-005
 
https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2022-005.txt
[4] SySS GmbH, SySS Responsible Disclosure Policy
     https://www.syss.de/en/responsible-disclosure-policy

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Credits:

This security vulnerability was found by Matthias Deeg of SySS GmbH.

E-Mail: matthias.deeg (at) syss.de
Public Key: 
https://www.syss.de/fileadmin/dokumente/Materialien/PGPKeys/Matthias_Deeg.asc
Key fingerprint = D1F0 A035 F06C E675 CDB9 0514 D9A4 BF6A 34AD 4DAB

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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.

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Copyright:

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