Server: refactor token verification to use the full verify library

[muhlemmer]

authenticator/cmd/server/transaction.go

Lines 183 to 208 in 4ee6ce9

	func (rt *requestTx) checkJWT(token string, valid time.Time) (*jwt.Claims, error) {
	log := rt.log.WithField("token", token)
	if token == "" {
	log.WithError(errors.New(errMissingToken)).Warn("checkJWT")
	return nil, status.Error(codes.InvalidArgument, errMissingToken)
	}
	kid, err := verify.ParseJWTHeader(token)
	if err != nil {
	log.WithError(err).Warn("tokens.ParseJWTHeader()")
	return nil, status.Error(codes.Unauthenticated, "Invalid token header")
	}
	key, err := rt.findJWTKey(kid)
	if err != nil {
	return nil, err
	}
	claims, err := jwt.EdDSACheck([]byte(token), []byte(key))
	if err != nil {
	log.WithError(err).Warn("jwt.EdDSACheck()")
	return nil, status.Error(codes.Unauthenticated, "EdDSA verification failed")
	}
	if !claims.Valid(valid) {
	log.WithError(errors.New(errExpiredToken)).Warn("jwt.EdDSACheck()")
	return nil, status.Error(codes.Unauthenticated, errExpiredToken)
	}
	return claims, nil
	}