fix(proxy_handler): Handle spaces in x-forwarded-for header (#327)

Having spaces or no spaces results in equivalent headers in RFC 7239:
   As an example, the header field

       Forwarded: for=192.0.2.43,for="[2001:db8:cafe::17]",for=unknown

   is equivalent to the header field

       Forwarded: for=192.0.2.43, for="[2001:db8:cafe::17]", for=unknown

This PR fixes #326 because we treated spaces as mandatory in the Forwarded Header.

Signed-off-by: Lennard Eijsackers <[email protected]>

Author: Blokje5

proxy_handler.go

@@ -74,7 +74,7 @@ func extractFirstMatchFromIPList(ipList string) string {
 	if ipList == "" {
 		return ""
 	}
-	s := strings.Index(ipList, ", ")
+	s := strings.Index(ipList, ",")
 	if s == -1 {
 		s = len(ipList)
 	}
@@ -91,7 +91,7 @@ func parseForwardedHeader(fwd string) string {
 	for _, split := range splits {
 		trimmed := strings.TrimSpace(split)
 		if strings.HasPrefix(strings.ToLower(trimmed), "for=") {
-			forSplits := strings.Split(trimmed, ", ")
+			forSplits := strings.Split(trimmed, ",")
 			if len(forSplits) == 0 {
 				return ""
 			}

proxy_handler_test.go

@@ -74,6 +74,19 @@ func TestProxyHandler(t *testing.T) {
 			},
 			expectedAddr: "10.0.0.1",
 		},
+		{
+			name: "proxy should forward proxy header Forwarded if set and treat a lack of spaces as an equivalent (issue #326).",
+			proxy: &config.Proxy{
+				Enable: true,
+			},
+			r: &http.Request{
+				RemoteAddr: "127.0.0.1:1234",
+				Header: http.Header{
+					"Forwarded": []string{"for=10.0.0.1,for=10.0.0.3"},
+				},
+			},
+			expectedAddr: "10.0.0.1",
+		},
 		{
 			name: "proxy should properly parse Forwarded header",
 			proxy: &config.Proxy{