Incorrect Comparison Logic Granularity

Opis

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.

Skutki

• Confidentiality, Authorization

  Bypass Protection Mechanism

Zapobieganie

• Implementation

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

Przykłady podatności

• 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.

Słabość nadrzędna

• CWE-208 Observable Timing Discrepancy
• CWE-697 Incorrect Comparison

Kiedy powstaje

• Architecture and Design
• Implementation

Dotyczy

Not Language-Specific, Not OS-Specific, Not Architecture-Specific, Not Technology-Specific

Uwagi

CWE 4.16 removed a demonstrative example for a hardware module because it was inaccurate and unable to be adapted. The CWE team is developing an alternative.

Źródła

1. SCA4n00bz - Timing-based Sidechannel Attacks for Hardware N00bz workshop — Joe Fitzpatrick