tree e2acc6bec929890f1157ef89e3f501188f18af96
parent 8a3b2692bcc68ea4c68d2bdd00d5ec647e33b769
author David Benjamin <davidben@google.com> 1661545489 -0400
committer Adam Langley <agl@google.com> 1661805617 +0000

Add EVP_HPKE_KDF_hkdf_md.

Some HPKE consumers call into the KDF directly. We don't have an EVP_KDF
abstraction and it's not clear to me how settled "KDF" is as an
interface. (HPKE specifically assumes an extract/expand pair.)

For now, just add EVP_HPKE_KDF_hkdf_md which is defined to only work for
HKDF KDFs. As we don't implement ID -> KDF lookup ourselves and expect
callers to decide which algorithms they want to export, any future
non-HKDF-based KDF won't affect existing callers anyway. If that
happens, we can make this return an EVP_KDF or just add
EVP_HPKE_KDF_{extract,expand} depending on universal this turns out to
be.

Change-Id: I93b9c8a5340472974a6f1bfc45154371d8971600
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/54085
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>