Add helper.IsContentType and use it everywhere

internal/api/api.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"mime"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -288,6 +287,5 @@ func bufferResponse(r io.Reader) (*bytes.Buffer, error) {
 }
 
 func validResponseContentType(resp *http.Response) bool {
-	parsed, _, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))
-	return err == nil && parsed == ResponseContentType
+	return helper.IsContentType(ResponseContentType, resp.Header.Get("Content-Type"))
 }

internal/api/block.go

@@ -44,7 +44,7 @@ func (b *blocker) WriteHeader(status int) {
 		return
 	}
 
-	if b.Header().Get("Content-Type") == ResponseContentType {
+	if helper.IsContentType(ResponseContentType, b.Header().Get("Content-Type")) {
 		b.status = 500
 		b.Header().Del("Content-Length")
 		b.hijacked = true

internal/helper/helpers.go

@@ -3,6 +3,7 @@ package helper
 import (
 	"errors"
 	"log"
+	"mime"
 	"net"
 	"net/http"
 	"net/url"
@@ -160,3 +161,8 @@ func SetForwardedFor(newHeaders *http.Header, originalRequest *http.Request) {
 		newHeaders.Set("X-Forwarded-For", header)
 	}
 }
+
+func IsContentType(expected, actual string) bool {
+	parsed, _, err := mime.ParseMediaType(actual)
+	return err == nil && parsed == expected
+}

internal/upstream/routes.go

 package upstream
 
 import (
-	"mime"
 	"net/http"
 	"path"
 	"regexp"
@@ -67,8 +66,7 @@ func wsRoute(regexpStr string, handler http.Handler, matchers ...matcherFunc) ro
 // Creates matcherFuncs for a particular content type.
 func isContentType(contentType string) func(*http.Request) bool {
 	return func(r *http.Request) bool {
-		parsed, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
-		return err == nil && contentType == parsed
+		return helper.IsContentType(contentType, r.Header.Get("Content-Type"))
 	}
 }