CWE-1254 Incorrect Comparison Logic Granularity

The product's comparison logic is performed over a series of steps rather than across the entire string in one operation. If there is a comparison logic failure on one of these steps, the operation may be vulnerable to a timing attack that can result in the interception of the process for nefarious purposes.

Comparison logic is used to compare a variety of objects including passwords, Message Authentication Codes (MACs), and responses to verification challenges. When comparison logic is implemented at a finer granularity (e.g., byte-by-byte comparison) and breaks in the case of a comparison failure, an attacker can exploit this implementation to identify when exactly the failure occurred. With multiple attempts, the attacker may be able to guesses the correct password/response to challenge and elevate their privileges.

• Confidentiality, Authorization: Bypass Protection Mechanism

• [Implementation] The hardware designer should ensure that comparison logic is implemented so as to compare in one operation instead in smaller chunks.

• CVE-2019-10482: Smartphone OS uses comparison functions that are not in constant time, allowing side channels • CVE-2019-10071: Java-oriented framework compares HMAC signatures using String.equals() instead of a constant-time algorithm, causing timing discrepancies • CVE-2014-0984: Password-checking function in router terminates validation of a password entry when it encounters the first incorrect character, which allows remote attackers to obtain passwords via a brute-force attack that relies on timing differences in responses to incorrect password guesses, aka a timing side-channel attack.