From 03e718023603cc06b75a08faa1b5988d50551caa Mon Sep 17 00:00:00 2001
From: nsfisis <nsfisis@gmail.com>
Date: Tue, 2 Apr 2024 01:12:12 +0900
Subject: modify location header the origin server responds

---
 server.go | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/server.go b/server.go
index 7c7c6a6..261b6bf 100644
--- a/server.go
+++ b/server.go
@@ -64,6 +64,33 @@ func newMultipleReverseProxyServer(ps []ProxyConfig) (*multipleReverseProxyServe
 				r.SetURL(targetUrl)
 				r.SetXForwarded()
 			},
+			ModifyResponse: func(r *http.Response) error {
+				if r.StatusCode < 300 || 400 <= r.StatusCode {
+					return nil
+				}
+
+				// If the response is redirect and has location header, rewrite it.
+				location := r.Header.Get("Location")
+				if location == "" {
+					return nil
+				}
+				locationUrl, err := url.Parse(location)
+				if err != nil {
+					return nil
+				}
+				if !locationUrl.IsAbs() {
+					return nil
+				}
+				if locationUrl.Hostname() != targetUrl.Hostname() {
+					return nil
+				}
+				locationUrl.Host = p.From.Host
+				if locationUrl.Scheme == "http" {
+					locationUrl.Scheme = "https"
+				}
+				r.Header.Set("Location", locationUrl.String())
+				return nil
+			},
 		}
 		if p.BasicAuth != nil {
 			credentialFileContent, err := os.ReadFile(p.BasicAuth.CredentialFile)
-- 
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