From 1c223d993157d86a3a4e41857910f75e264218b0 Mon Sep 17 00:00:00 2001
From: PJ Eby <pje@telecommunity.com>
Date: Tue, 28 Nov 2017 01:37:26 -0500
Subject: [PATCH] Allow setting upstream Host header

---
 forwarding.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/forwarding.go b/forwarding.go
index e7669fff..6851a10a 100644
--- a/forwarding.go
+++ b/forwarding.go
@@ -58,7 +58,12 @@ func (r *oauthProxy) proxyMiddleware(next http.Handler) http.Handler {
 		// and we must update the host headers
 		req.URL.Host = r.endpoint.Host
 		req.URL.Scheme = r.endpoint.Scheme
-		req.Host = r.endpoint.Host
+		if v := req.Header.Get("Host"); v != "" {
+			req.Host = v
+			req.Header.Del("Host")
+		} else {
+			req.Host = r.endpoint.Host
+		}
 
 		req.Header.Add("X-Forwarded-For", realIP(req))
 		req.Header.Set("X-Forwarded-Host", req.URL.Host)