auth: send LSAT and L402 Authorization headers

Again, as with WWW-Authenticate header, existing aperture instances
expect LSAT, and the protocol defines it is L402, so send both, LSAT
first, to maintain backward compatibility.

The header "Authorization: LSAT..." can be removed in the future,
when all aperture instances are upgraded.

auth/authenticator_test.go

@@ -100,11 +100,33 @@ func TestL402Authenticator(t *testing.T) {
 				result: false,
 			},
 			{
-				id: "valid auth header",
+				id: "valid auth header (both LSAT and L402)",
 				header: &http.Header{
 					l402.HeaderAuthorization: []string{
 						"LSAT " + testMacBase64 + ":" +
 							testPreimage,
+						"L402 " + testMacBase64 + ":" +
+							testPreimage,
+					},
+				},
+				result: true,
+			},
+			{
+				id: "valid auth header (LSAT only)",
+				header: &http.Header{
+					l402.HeaderAuthorization: []string{
+						"LSAT " + testMacBase64 + ":" +
+							testPreimage,
+					},
+				},
+				result: true,
+			},
+			{
+				id: "valid auth header (L402 only)",
+				header: &http.Header{
+					l402.HeaderAuthorization: []string{
+						"L402 " + testMacBase64 + ":" +
+							testPreimage,
 					},
 				},
 				result: true,

l402/header.go

@@ -27,13 +27,15 @@ const (
 )
 
 var (
-	authRegex  = regexp.MustCompile("LSAT (.*?):([a-f0-9]{64})")
-	authFormat = "LSAT %s:%s"
+	authRegex        = regexp.MustCompile("(LSAT|L402) (.*?):([a-f0-9]{64})")
+	authFormatLegacy = "LSAT %s:%s"
+	authFormat       = "L402 %s:%s"
 )
 
 // FromHeader tries to extract authentication information from HTTP headers.
-// There are two supported formats that can be sent in three different header
+// There are two supported formats that can be sent in four different header
 // fields:
+//  0. Authorization: LSAT <macBase64>:<preimageHex>
 //  1. Authorization: L402 <macBase64>:<preimageHex>
 //  2. Grpc-Metadata-Macaroon: <macHex>
 //  3. Macaroon: <macHex>
@@ -49,21 +51,27 @@ func FromHeader(header *http.Header) (*macaroon.Macaroon, lntypes.Preimage, erro
 	case header.Get(HeaderAuthorization) != "":
 		// Parse the content of the header field and check that it is in
 		// the correct format.
-		authHeader = header.Get(HeaderAuthorization)
-		log.Debugf("Trying to authorize with header value [%s].",
-			authHeader)
-		if !authRegex.MatchString(authHeader) {
-			return nil, lntypes.Preimage{}, fmt.Errorf("invalid "+
-				"auth header format: %s", authHeader)
+		var matches []string
+		authHeaders := header.Values(HeaderAuthorization)
+		for _, authHeader := range authHeaders {
+			log.Debugf("Trying to authorize with header value "+
+				"[%s].", authHeader)
+			if !authRegex.MatchString(authHeader) {
+				continue
+			}
+			matches = authRegex.FindStringSubmatch(authHeader)
+			if len(matches) != 4 {
+				continue
+			}
 		}
-		matches := authRegex.FindStringSubmatch(authHeader)
-		if len(matches) != 3 {
+
+		if len(matches) != 4 {
 			return nil, lntypes.Preimage{}, fmt.Errorf("invalid "+
 				"auth header format: %s", authHeader)
 		}
 
 		// Decode the content of the two parts of the header value.
-		macBase64, preimageHex := matches[1], matches[2]
+		macBase64, preimageHex := matches[2], matches[3]
 		macBytes, err := base64.StdEncoding.DecodeString(macBase64)
 		if err != nil {
 			return nil, lntypes.Preimage{}, fmt.Errorf("base64 "+
@@ -134,10 +142,17 @@ func SetHeader(header *http.Header, mac *macaroon.Macaroon,
 	if err != nil {
 		return err
 	}
-	value := fmt.Sprintf(
-		authFormat, base64.StdEncoding.EncodeToString(macBytes),
-		preimage.String(),
-	)
-	header.Set(HeaderAuthorization, value)
+	macStr := base64.StdEncoding.EncodeToString(macBytes)
+	preimageStr := preimage.String()
+
+	// Send "Authorization: LSAT..." header before sending
+	// "Authorization: L402" header to be compatible with old aperture.
+	// TODO: remove this after aperture is upgraded everywhere.
+	legacyValue := fmt.Sprintf(authFormatLegacy, macStr, preimageStr)
+	header.Set(HeaderAuthorization, legacyValue)
+
+	value := fmt.Sprintf(authFormat, macStr, preimageStr)
+	header.Add(HeaderAuthorization, value)
+
 	return nil
 }