Added private error handler middleware

jwt.go

@@ -69,18 +69,33 @@ func NewMiddleware(c *Config) (*JWTMiddleware, error) {
 	return m, nil
 }
 
+type jwtError struct {
+	status  int
+	err     error
+	message string
+}
+
+type errorHandler func(http.ResponseWriter, *http.Request) *jwtError
+
+func (e errorHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if err := e(w, r); err != nil {
+		if err.message != "" {
+			log.Printf("error (%v) while %s", err.err, err.message)
+		}
+		http.Error(w, err.err.Error(), err.status)
+	}
+}
+
 func (m *JWTMiddleware) Secure(h http.Handler, v VerifyClaimsFunc) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	secureHandler := func(w http.ResponseWriter, r *http.Request) *jwtError {
 		authHeader := r.Header.Get("Authorization")
 		if authHeader == "" {
-			http.Error(w, ErrMissingToken.Error(), http.StatusUnauthorized)
-			return
+			return &jwtError{status: http.StatusUnauthorized, err: ErrMissingToken}
 		}
 		token := strings.Split(authHeader, " ")[1]
 		tokenParts := strings.Split(token, ".")
 		if len(tokenParts) != 3 {
-			http.Error(w, ErrMalformedToken.Error(), http.StatusUnauthorized)
-			return
+			return &jwtError{status: http.StatusUnauthorized, err: ErrMalformedToken}
 		}
 
 		// First, verify JOSE header
@@ -90,15 +105,19 @@ func (m *JWTMiddleware) Secure(h http.Handler, v VerifyClaimsFunc) http.Handler
 		}
 		header, err := decode(tokenParts[0])
 		if err != nil {
-			log.Printf("error (%v) while decoding header (%v)", err, tokenParts[0])
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
+			return &jwtError{
+				status:  http.StatusInternalServerError,
+				err:     err,
+				message: fmt.Sprintf("decoding header (%v)", tokenParts[0]),
+			}
 		}
 		err = json.Unmarshal(header, &t)
 		if err != nil {
-			log.Printf("error (%v) while unmarshalling header (%s)", err, header)
-			http.Error(w, ErrMalformedToken.Error(), http.StatusInternalServerError)
-			return
+			return &jwtError{
+				status:  http.StatusInternalServerError,
+				err:     ErrMalformedToken,
+				message: fmt.Sprintf("unmarshalling header (%s)", header),
+			}
 		}
 
 		// Then, verify signature
@@ -107,32 +126,40 @@ func (m *JWTMiddleware) Secure(h http.Handler, v VerifyClaimsFunc) http.Handler
 		mac.Write(message)
 		expectedMac, err := encode(mac.Sum(nil))
 		if err != nil {
-			panic(err)
-			return
+			return &jwtError{status: http.StatusInternalServerError, err: err}
 		}
 		if !hmac.Equal([]byte(tokenParts[2]), []byte(expectedMac)) {
-			log.Printf("invalid signature: %v", tokenParts[2])
-			http.Error(w, ErrInvalidSignature.Error(), http.StatusUnauthorized)
-			return
+			return &jwtError{
+				status:  http.StatusUnauthorized,
+				err:     ErrInvalidSignature,
+				message: fmt.Sprintf("checking signature (%v)", tokenParts[2]),
+			}
 		}
 
 		// Finally, check claims
 		claimSet, err := decode(tokenParts[1])
 		if err != nil {
-			log.Printf("error (%v) while decoding claims", err)
-			http.Error(w, ErrDecoding.Error(), http.StatusInternalServerError)
-			return
+			return &jwtError{
+				status:  http.StatusInternalServerError,
+				err:     ErrDecoding,
+				message: "decoding claims",
+			}
 		}
 		err = v(claimSet)
 		if err != nil {
-			log.Printf("claims handler error: %v", err)
-			http.Error(w, err.Error(), http.StatusUnauthorized)
-			return
+			return &jwtError{
+				status:  http.StatusUnauthorized,
+				err:     err,
+				message: "handling claims callback",
+			}
 		}
 
 		// If we make it this far, process the downstream handler
 		h.ServeHTTP(w, r)
-	})
+		return nil
+	}
+
+	return errorHandler(secureHandler)
 }
 
 func (m *JWTMiddleware) GenerateToken(w http.ResponseWriter, r *http.Request) {