From a584df6afa719cd9b9f0b70b9265cf65febfd8ec Mon Sep 17 00:00:00 2001
From: Adnan Maolood <me@adnano.co>
Date: Wed, 24 Feb 2021 18:22:01 -0500
Subject: [PATCH] Display an error on charsets other than UTF-8

This prevents the proxy from sending invalid UTF-8 to the client.
---
 main.go | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/main.go b/main.go
index bbfac30..f836415 100644
--- a/main.go
+++ b/main.go
@@ -453,8 +453,7 @@ func proxyGemini(req gemini.Request, external bool, root *url.URL,
 		return
 	}
 
-	// XXX: We could use the params I guess
-	m, _, err := mime.ParseMediaType(resp.Meta)
+	m, params, err := mime.ParseMediaType(resp.Meta)
 	if err != nil {
 		w.WriteHeader(http.StatusBadGateway)
 		w.Write([]byte(fmt.Sprintf("Gateway error: %d %s: %v",
@@ -468,6 +467,15 @@ func proxyGemini(req gemini.Request, external bool, root *url.URL,
 		return
 	}
 
+	if charset, ok := params["charset"]; ok {
+		charset = strings.ToLower(charset)
+		if charset != "utf-8" {
+			w.WriteHeader(http.StatusNotImplemented)
+			fmt.Fprintf(w, "Unsupported charset: %s", charset)
+			return
+		}
+	}
+
 	w.Header().Add("Content-Type", "text/html")
 	ctx := &GemtextContext{
 		CSS:      css,