all the following discussion is for HKDF in TLS1.3:
Regarding the 'salt' parameter in - HKDF-Extract(salt, IKM)
as written in RFC 5869:
HKDF without having to protect the secrecy of the salt. In a different application domain, a key agreement protocol deriving
cryptographic keys from a Diffie-Hellman exchange can derive a salt value from public nonces exchanged and authenticated between
communicating parties as part of the key agreement (this is the
approach taken in [IKEv2]).
From what it seems, the client's random nonce is used for the salt, but I cannot find any documentation about it in the TLS 1.3 RFC, am I correct?
And regarding the 'info' paramter in HKDF-Expand(PRK, info, L):
Is it identical to the 'label' which's used in TLS 1.2 for PRF? Or are there new values for TLS 1.3 when deriving keys?
I'm just really confused about which parameter should be passed in each stage.
For example, when deriving the master-secret with the relevant hash, shared-secret, which 'info' parameter should be passed?
Thanks in advance!