BSA-2017-445

Brocade Security Advisory ID

BSA-2017-445

Initial Publication Date

09/29/2017

Last Updated

10/27/2017

Revision

3.0: Final

Risk Impact

Medium

Workaround

N/A

Component

DENX Das U-Boot

Affected CVE

CVE-2017-3226

CVSS Score

5.8

Summary

Das U-Boot is a device bootloader that can read its configuration from an AES encrypted file. For devices utilizing this environment encryption mode, U-Boot's use of a zero initialization vector and improper handling of an error condition may allow attacks against the underlying cryptographic implementation and allow an attacker to decrypt the data.

Devices that make use of Das U-Boot's AES-CBC encryption feature using environment encryption (i.e., setting the configuration parameter) read environment variables from disk as the encrypted disk image is processed. An attacker with physical access to the device can manipulate the encrypted environment data to include a crafted two-byte sequence which triggers an error in environment variable parsing. This error condition is improperly handled by Das U-Boot, resulting in an immediate process termination with a debugging message.

The immediate failure can be used as an oracle for a Vaudenay-style timing attack on the cryptography, allowing a dedicated attacker to decrypt and potentially modify the contents of the device.

Affected Products

Brocade is investigating its product lines to determine which products may be affected by this vulnerability and the impact on each affected product.

Products Confirmed Not Vulnerable

Brocade Fabric OS, Brocade NetIron OS, Brocade Network Advisor, Brocade Network OS, Brocade ServerIronADX, Brocade SLX-OS, Brocade Virtual ADX, and Brocade Workflow Composer are confirmed not affected by this vulnerability.

Workaround

There are no workarounds that address this vulnerability.

Revision History

Version Change Date
1.0 Initial Publication September 29, 2017
2.0 Updated to address BNA, FOS, & WC October 13, 2017
3.0 Updated to address ADX & vADX October 27, 2017

Disclaimer

THIS DOCUMENT IS PROVIDED ON AN AS-IS BASIS SOLELY FOR INFORMATIONAL PURPOSES AND DOES NOT IMPLY ANY KIND OF GUARANTY OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. YOUR USE OF THE INFORMATION CONTAINED HEREIN IS AT YOUR OWN RISK. ALL INFORMATION PROVIDED HEREIN IS BASED ON BROCADE'S CURRENT KNOWLEDGE AND UNDERSTANDING OF THE VULNERABILITY AND IMPACT TO BROCADE HARDWARE AND SOFTWARE PRODUCTS. BROCADE RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.