Add support for array of audiences

See https://github.com/dgrijalva/jwt-go/pull/308

internal/serv/internal/auth/jwt.go

@@ -3,6 +3,8 @@ package auth
 import (
 	"context"
 	"encoding/json"
+	"errors"
+	"fmt"
 	"io/ioutil"
 	"net/http"
 	"strconv"
@@ -28,6 +30,30 @@ type firebasePKCache struct {
 
 var firebasePublicKeys firebasePKCache
 
+type standardClaims struct {
+	jwt.StandardClaims
+	Audience []string `json:"aud,omitempty"`
+}
+
+func (c *standardClaims) MatchAudience(audience string) bool {
+	matchLegacy := c.StandardClaims.Audience == audience
+	if matchLegacy {
+		return true
+	}
+
+	if c.Audience == nil {
+		return false
+	}
+
+	for _, tokenAudience := range c.Audience {
+		if audience == tokenAudience {
+			return true
+		}
+	}
+
+	return false
+}
+
 func JwtHandler(ac *Auth, next http.Handler) (http.HandlerFunc, error) {
 	var key interface{}
 	var jwtProvider int
@@ -99,17 +125,16 @@ func JwtHandler(ac *Auth, next http.Handler) (http.HandlerFunc, error) {
 			}
 		}
 
-		token, err := jwt.ParseWithClaims(tok, &jwt.StandardClaims{}, keyFunc)
-
+		token, err := jwt.ParseWithClaims(tok, &standardClaims{}, keyFunc)
 		if err != nil {
 			next.ServeHTTP(w, r)
 			return
 		}
 
-		if claims, ok := token.Claims.(*jwt.StandardClaims); ok {
+		if claims, ok := token.Claims.(*standardClaims); ok {
 			ctx := r.Context()
 
-			if ac.JWT.Audience != "" && claims.Audience != ac.JWT.Audience {
+			if ac.JWT.Audience != "" && !claims.MatchAudience(ac.JWT.Audience) {
 				next.ServeHTTP(w, r)
 				return
 			}