SigV4 authentication is surprisingly complicated

SigV4 looks simple: sign a request, check the signature. Then you implement canonicalization, clock skew, and a cache that isn't allowed to hold your key. Tigris is a drop-in replacement for AWS S3 (or GCS, anything S3API compatible). As such, we need to be fully compatible with both the mechanisms and semantics of S3 including the SigV4 authentication protocol. This is the lingua franca of authentication in the object storage landscape; even Google Cloud Storage has a way to enable SigV4 support so you can use existing applications against its object storage service. At first I thought that SigV4 was fairly simple. Clients sign requests, servers do the same work and make sure the result matches. The main sticking point is that the cryptography involved is symmetric cryptography, the kind where both parties need to have the same secrets. This makes some scaling issues weird, but we'll get into that in the future. NoteThis is only going to be talking about authentication (ensuring the…