On 14/08/2019 08:59, Peter Eisentraut wrote:
I'm confused by how the code uses the term "verifier" in relation to SCRAM.
ISTM that the code uses the term as meaning whatever is or would be
stored in pg_auth.rolpassword.
I don't see this usage supported in the RFCs. In RFC 5802,
verifier = "v=" base64
;; base-64 encoded ServerSignature.
where
ServerSignature := HMAC(ServerKey, AuthMessage)
ServerKey := HMAC(SaltedPassword, "Server Key")
AuthMessage := client-first-message-bare + "," +
server-first-message + "," +
client-final-message-without-proof
whereas what is stored in rolpassword is
SCRAM-SHA-256$<iterations>:<salt>$<storedkey>:<serverkey>
where
StoredKey := H(ClientKey)
ClientKey := HMAC(SaltedPassword, "Client Key")
So while these are all related, I don't think it's accurate to call what
is in rolpassword a SCRAM "verifier".
Huh, you're right.
RFC 5803 is titled "Lightweight Directory Access Protocol (LDAP) Schema
for Storing Salted Challenge Response Authentication Mechanism (SCRAM)
Secrets". Following that, I think calling the contents of rolpassword a
"secret" or a "stored secret" would be better.
RFC 5802 uses the term "Authentication information". See section "2.1
Terminology":
o Authentication information: Information used to verify an identity
claimed by a SCRAM client. The authentication information for a
SCRAM identity consists of salt, iteration count, "StoredKey" and
"ServerKey" (as defined in the algorithm overview) for each
supported cryptographic hash function.
But I agree that "secret", as used in RFC5803 is better.
- Heikki
