Control-flow timing leak in Kyber reference implementation when compiled with Clang 15-18 for -Os, -O1 and other options

Vulnerability Description

liboqs is a C-language cryptographic library that provides implementations of post-quantum cryptography algorithms. A control-flow timing lean has been identified in the reference implementation of the Kyber key encapsulation mechanism when it is compiled with Clang 15-18 for `-Os`, `-O1`, and other compilation options. A proof-of-concept local attack on the reference implementation leaks the entire ML-KEM 512 secret key in ~10 minutes using end-to-end decapsulation timing measurements. The issue has been fixed in version 0.10.1. As a possible workaround, some compiler options may produce vectorized code that does not leak secret information, however relying on these compiler options as a workaround may not be reliable.

References

• https://github.com/open-quantum-safe/liboqs/security/advisories/GHSA-f2v9-5498-2vpp
• https://github.com/open-quantum-safe/liboqs/commit/982c762c242ef549c914891b47bf6e0ed6321f91
• https://github.com/pq-crystals/kyber/commit/9b8d30698a3e7449aeb34e62339d4176f11e3c6c
• https://github.com/open-quantum-safe/liboqs/blob/7eecda6095c003ddded7175a1ffdf35a2ce63ed5/src/kem/kyber/pqcrystals-kyber_kyber512_ref/poly.c#L166