Summary

Security Advisory ID : BSA-2017-445

Component : DENX Das U-Boot

Revision : 3.0: Final

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