CosmicClash/server/domain/join_auth.go

package domain

import (
	"fmt"
	"time"
)

// SignedJoinAuthorisation is the transport envelope. The signing primitive is
// supplied by the backend signer so this policy stays independent of key
// storage and cryptographic algorithm choice.
type SignedJoinAuthorisation struct {
	Authorisation JoinAuthorisation
	Signature     []byte
}

func JoinAuthorisationBytes(auth JoinAuthorisation) []byte {
	return []byte(fmt.Sprintf("%s\x00%s\x00%s\x00%s\x00%d\x00%d\x00%s\x00%d\x00%s",
		auth.MatchID, auth.ServerID, auth.PlayerID, auth.SteamID, auth.Slot, auth.Team, auth.Protocol, auth.Generation, auth.ExpiresAt.UTC().Format(time.RFC3339Nano)))
}

func SignJoinAuthorisation(auth JoinAuthorisation, sign func([]byte) ([]byte, error)) (SignedJoinAuthorisation, error) {
	if sign == nil {
		return SignedJoinAuthorisation{}, ErrJoinAuthorisation
	}
	signature, err := sign(JoinAuthorisationBytes(auth))
	if err != nil || len(signature) == 0 {
		return SignedJoinAuthorisation{}, ErrJoinAuthorisation
	}
	return SignedJoinAuthorisation{Authorisation: auth, Signature: append([]byte(nil), signature...)}, nil
}

func (r *RankedConnections) AdmitSigned(signed SignedJoinAuthorisation, verify func([]byte, []byte) bool, now time.Time) (uint64, error) {
	if len(signed.Signature) == 0 || verify == nil || !verify(JoinAuthorisationBytes(signed.Authorisation), signed.Signature) {
		return 0, ErrJoinAuthorisation
	}
	return r.Admit(signed.Authorisation, now)
}