From 22a86038929923429679b189b5fce160fd9ef2e9 Mon Sep 17 00:00:00 2001
From: Jens Langhammer <jens.langhammer@beryju.org>
Date: Wed, 22 Dec 2021 10:16:01 +0100
Subject: [PATCH] internal: add custom proxy certificates support to embedded
 outpost

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>
---
 internal/outpost/proxyv2/proxyv2.go | 20 ++++++++++++++------
 internal/web/{ssl.go => tls.go}     | 23 ++++++++++++++++++-----
 2 files changed, 32 insertions(+), 11 deletions(-)
 rename internal/web/{ssl.go => tls.go} (63%)

diff --git a/internal/outpost/proxyv2/proxyv2.go b/internal/outpost/proxyv2/proxyv2.go
index d6d44d530..afa5b8d7f 100644
--- a/internal/outpost/proxyv2/proxyv2.go
+++ b/internal/outpost/proxyv2/proxyv2.go
@@ -88,17 +88,25 @@ func (ps *ProxyServer) Type() string {
 
 func (ps *ProxyServer) TimerFlowCacheExpiry() {}
 
-func (ps *ProxyServer) getCertificates(info *tls.ClientHelloInfo) (*tls.Certificate, error) {
-	app, ok := ps.apps[info.ServerName]
+func (ps *ProxyServer) GetCertificate(serverName string) *tls.Certificate {
+	app, ok := ps.apps[serverName]
 	if !ok {
-		ps.log.WithField("server-name", info.ServerName).Debug("app does not exist")
-		return &ps.defaultCert, nil
+		ps.log.WithField("server-name", serverName).Debug("app does not exist")
+		return nil
 	}
 	if app.Cert == nil {
-		ps.log.WithField("server-name", info.ServerName).Debug("app does not have a certificate")
+		ps.log.WithField("server-name", serverName).Debug("app does not have a certificate")
+		return nil
+	}
+	return app.Cert
+}
+
+func (ps *ProxyServer) getCertificates(info *tls.ClientHelloInfo) (*tls.Certificate, error) {
+	appCert := ps.GetCertificate(info.ServerName)
+	if appCert == nil {
 		return &ps.defaultCert, nil
 	}
-	return app.Cert, nil
+	return appCert, nil
 }
 
 // ServeHTTP constructs a net.Listener and starts handling HTTP requests
diff --git a/internal/web/ssl.go b/internal/web/tls.go
similarity index 63%
rename from internal/web/ssl.go
rename to internal/web/tls.go
index bf6fc4bf4..da1c9d4a1 100644
--- a/internal/web/ssl.go
+++ b/internal/web/tls.go
@@ -9,16 +9,29 @@ import (
 	"goauthentik.io/internal/crypto"
 )
 
-// ServeHTTPS constructs a net.Listener and starts handling HTTPS requests
-func (ws *WebServer) listenTLS() {
+func (ws *WebServer) GetCertificate() func(ch *tls.ClientHelloInfo) (*tls.Certificate, error) {
 	cert, err := crypto.GenerateSelfSignedCert()
 	if err != nil {
 		ws.log.WithError(err).Error("failed to generate default cert")
 	}
+	return func(ch *tls.ClientHelloInfo) (*tls.Certificate, error) {
+		if ws.ProxyServer != nil {
+			appCert := ws.ProxyServer.GetCertificate(ch.ServerName)
+			if appCert != nil {
+				return appCert, nil
+			}
+		}
+		ws.log.Trace("using default, self-signed certificate")
+		return &cert, nil
+	}
+}
+
+// ServeHTTPS constructs a net.Listener and starts handling HTTPS requests
+func (ws *WebServer) listenTLS() {
 	tlsConfig := &tls.Config{
-		MinVersion:   tls.VersionTLS12,
-		MaxVersion:   tls.VersionTLS12,
-		Certificates: []tls.Certificate{cert},
+		MinVersion:     tls.VersionTLS12,
+		MaxVersion:     tls.VersionTLS12,
+		GetCertificate: ws.GetCertificate(),
 	}
 
 	ln, err := net.Listen("tcp", config.G.Web.ListenTLS)