Many consumers need SPKI support (X.509, TLS, QUIC, WebCrypto), each
with different ways to set signature parameters. SPKIs themselves can
get complex with id-RSASSA-PSS keys which come with various constraints
in the key parameters. This suggests we want a common in-library
representation of an SPKI.
This adds two new functions EVP_parse_public_key and
EVP_marshal_public_key which converts EVP_PKEY to and from SPKI and
implements X509_PUBKEY functions with them. EVP_PKEY seems to have been
intended to be able to express the supported SPKI types with
full-fidelity, so these APIs will continue this.
This means future support for id-RSASSA-PSS would *not* repurpose
EVP_PKEY_RSA. I'm worried about code assuming EVP_PKEY_RSA implies
acting on the RSA* is legal. Instead, it'd add an EVP_PKEY_RSA_PSS and
the data pointer would be some (exposed, so the caller may still check
key size, etc.) RSA_PSS_KEY struct. Internally, the EVP_PKEY_CTX
implementation would enforce the key constraints. If RSA_PSS_KEY would
later need its own API, that code would move there, but that seems
unlikely.
Ideally we'd have a 1:1 correspondence with key OID, although we may
have to fudge things if mistakes happen in standardization. (Whether or
not X.509 reuses id-ecPublicKey for Ed25519, we'll give it a separate
EVP_PKEY type.)
DSA parsing hooks are still implemented, missing parameters and all for
now. This isn't any worse than before.
Decoupling from the giant crypto/obj OID table will be a later task.
BUG=522228
Change-Id: I0e3964edf20cb795a18b0991d17e5ca8bce3e28c
Reviewed-on: https://boringssl-review.googlesource.com/6861
Reviewed-by: Adam Langley <agl@google.com>
68772b31b0