Only use Host header from reverse proxy (#32060)

X-Forwarded-Host has many problems: non-standard, not well-defined
(X-Forwarded-Port or not), conflicts with Host header, it already caused
problems like #31907. So do not use X-Forwarded-Host, just use Host
header directly.

Official document also only uses `Host` header and never mentioned
others.

.github/workflows/pull-db-tests.yml

@@ -201,7 +201,8 @@ jobs:
     runs-on: ubuntu-latest
     services:
       mssql:
-        image: mcr.microsoft.com/mssql/server:2017-latest
+        # some images before 2024-04 can't run on new kernels
+        image: mcr.microsoft.com/mssql/server:2019-latest
         env:
           ACCEPT_EULA: Y
           MSSQL_PID: Standard

modules/httplib/url.go

@@ -52,11 +52,6 @@ func getRequestScheme(req *http.Request) string {
 	return ""
 }
 
-func getForwardedHost(req *http.Request) string {
-	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Host
-	return req.Header.Get("X-Forwarded-Host")
-}
-
 // GuessCurrentAppURL tries to guess the current full app URL (with sub-path) by http headers. It always has a '/' suffix, exactly the same as setting.AppURL
 func GuessCurrentAppURL(ctx context.Context) string {
 	return GuessCurrentHostURL(ctx) + setting.AppSubURL + "/"
@@ -81,11 +76,9 @@ func GuessCurrentHostURL(ctx context.Context) string {
 	if reqScheme == "" {
 		return strings.TrimSuffix(setting.AppURL, setting.AppSubURL+"/")
 	}
-	reqHost := getForwardedHost(req)
-	if reqHost == "" {
-		reqHost = req.Host
-	}
-	return reqScheme + "://" + reqHost
+	// X-Forwarded-Host has many problems: non-standard, not well-defined (X-Forwarded-Port or not), conflicts with Host header.
+	// So do not use X-Forwarded-Host, just use Host header directly.
+	return reqScheme + "://" + req.Host
 }
 
 // MakeAbsoluteURL tries to make a link to an absolute URL:

modules/httplib/url_test.go

@@ -70,7 +70,7 @@ func TestMakeAbsoluteURL(t *testing.T) {
 			"X-Forwarded-Proto": {"https"},
 		},
 	})
-	assert.Equal(t, "https://forwarded-host/foo", MakeAbsoluteURL(ctx, "/foo"))
+	assert.Equal(t, "https://user-host/foo", MakeAbsoluteURL(ctx, "/foo"))
 }
 
 func TestIsCurrentGiteaSiteURL(t *testing.T) {
@@ -119,5 +119,6 @@ func TestIsCurrentGiteaSiteURL(t *testing.T) {
 		},
 	})
 	assert.True(t, IsCurrentGiteaSiteURL(ctx, "http://localhost:3000"))
-	assert.True(t, IsCurrentGiteaSiteURL(ctx, "https://forwarded-host"))
+	assert.True(t, IsCurrentGiteaSiteURL(ctx, "https://user-host"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "https://forwarded-host"))
 }