if !compareSignatureV2(gotSignature, expectedSignature) {
		return ErrSignatureDoesNotMatch
	}

	r.Form.Del(xhttp.Expires)

	return ErrNone
}

func getReqAccessKeyV2(r *http.Request) (auth.Credentials, bool, APIErrorCode) {
	if accessKey := r.Form.Get(xhttp.AmzAccessKeyID); accessKey != "" {
		return checkKeyValid(r, accessKey)
	}

		return ErrSignatureVersionNotSupported
	case authTypePresignedV2, authTypeSignedV2:
		if s3Err = isReqAuthenticatedV2(r); s3Err != ErrNone {
			return s3Err
		}
		cred, owner, s3Err = getReqAccessKeyV2(r)
	case authTypeSigned, authTypePresigned:
		region := globalSite.Region()
		switch action {
		case policy.GetBucketLocationAction, policy.ListAllMyBucketsAction:
			region = ""
		}

func getReqAccessCred(r *http.Request, region string) (cred auth.Credentials) {
	cred, _, _ = getReqAccessKeyV4(r, region, serviceS3)
	if cred.AccessKey == "" {
		cred, _, _ = getReqAccessKeyV2(r)
	}
	return cred
}

// Extract request params to be sent with event notification.
func extractReqParams(r *http.Request) map[string]string {
	if r == nil {
		return nil
	}