mbedtls/docs/3.0-migration-guide.d/require-matching-hashlen-rsa.md

RSA signature functions now require hashlen to match the expected value

This only affects users of the low-level RSA API; users of the high-level PK API or of the PSA Crypto API are not affected.

All the functions in the RSA module that accept a hashlen parameter used to ignore it unless the md_alg parameter was MBEDTLS_MD_NONE, indicating raw data was signed. They now require this parameter's value to be equal to the output size of the hash algorithm used when signing a hash. (The requirements when signing raw data are unchanged.)

The migration path is to pass the correct value to those functions.