Improper random reading in CIRCL

Medium5.3CVE-2023-1732 · Published May 10, 2023

### Impact When sampling randomness for a shared secret, the implementation of Kyber and FrodoKEM, did not check whether `crypto/rand.Read()` returns an error. In rare deployment cases (error thrown by the `Read()` function), this could lead to a predictable shared secret. The tkn20 and blindrsa components did not check whether enough randomness was returned from the user provided randomness source. Typically the user provides `crypto/rand.Reader`, which in the vast majority of cases will always return the right number random bytes. In the cases where it does not, or the user provides a source that does not, the blinding for blindrsa is weak and integrity of the plaintext is not ensured in tkn20. ### Patches The fix was introduced in CIRCL v. 1.3.3