From c8f3800f1cacb2a812fe467116c224b83709093b Mon Sep 17 00:00:00 2001
From: Simon Thulbourn <simon+github@thulbourn.com>
Date: Fri, 20 Mar 2015 15:19:07 +0000
Subject: [PATCH] Add client certificate CA option to authenticate with client
 certs

Add the ability to authenticate against multiple client CA certificates.

Signed-off-by: Simon Thulbourn <simon+github@thulbourn.com>
---
 cmd/registry/main.go                | 37 ++++++++++++++++++++++++++++-
 configuration/configuration.go      |  4 ++++
 configuration/configuration_test.go | 24 +++++++++++++++++++
 doc/configuration.md                |  7 ++++++
 4 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/cmd/registry/main.go b/cmd/registry/main.go
index 6c442895..ab14990b 100644
--- a/cmd/registry/main.go
+++ b/cmd/registry/main.go
@@ -1,9 +1,12 @@
 package main
 
 import (
+	"crypto/tls"
+	"crypto/x509"
 	_ "expvar"
 	"flag"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	_ "net/http/pprof"
 	"os"
@@ -67,8 +70,40 @@ func main() {
 			ctxu.GetLogger(app).Fatalln(err)
 		}
 	} else {
+		tlsConf := &tls.Config{
+			ClientAuth: tls.NoClientCert,
+		}
+
+		if len(config.HTTP.TLS.ClientCAs) != 0 {
+			pool := x509.NewCertPool()
+
+			for _, ca := range config.HTTP.TLS.ClientCAs {
+				caPem, err := ioutil.ReadFile(ca)
+				if err != nil {
+					ctxu.GetLogger(app).Fatalln(err)
+				}
+
+				if ok := pool.AppendCertsFromPEM(caPem); !ok {
+					ctxu.GetLogger(app).Fatalln(fmt.Errorf("Could not add CA to pool"))
+				}
+			}
+
+			for _, subj := range pool.Subjects() {
+				ctxu.GetLogger(app).Debugf("CA Subject: %s", string(subj))
+			}
+
+			tlsConf.ClientAuth = tls.RequireAndVerifyClientCert
+			tlsConf.ClientCAs = pool
+		}
+
 		ctxu.GetLogger(app).Infof("listening on %v, tls", config.HTTP.Addr)
-		if err := http.ListenAndServeTLS(config.HTTP.Addr, config.HTTP.TLS.Certificate, config.HTTP.TLS.Key, handler); err != nil {
+		server := &http.Server{
+			Addr:      config.HTTP.Addr,
+			Handler:   handler,
+			TLSConfig: tlsConf,
+		}
+
+		if err := server.ListenAndServeTLS(config.HTTP.TLS.Certificate, config.HTTP.TLS.Key); err != nil {
 			ctxu.GetLogger(app).Fatalln(err)
 		}
 	}
diff --git a/configuration/configuration.go b/configuration/configuration.go
index 6c03b27f..4bfbf9df 100644
--- a/configuration/configuration.go
+++ b/configuration/configuration.go
@@ -57,6 +57,10 @@ type Configuration struct {
 			// contain the private portion for the file specified in
 			// Certificate.
 			Key string `yaml:"key,omitempty"`
+
+			// Specifies the CA certs for client authentication
+			// A file may contain multiple CA certificates encoded as PEM
+			ClientCAs []string `yaml:"clientcas,omitempty"`
 		} `yaml:"tls,omitempty"`
 
 		// Debug configures the http debug interface, if specified. This can
diff --git a/configuration/configuration_test.go b/configuration/configuration_test.go
index 5a6abf90..c5041487 100644
--- a/configuration/configuration_test.go
+++ b/configuration/configuration_test.go
@@ -52,6 +52,27 @@ var configStruct = Configuration{
 			},
 		},
 	},
+	HTTP: struct {
+		Addr   string `yaml:"addr,omitempty"`
+		Prefix string `yaml:"prefix,omitempty"`
+		Secret string `yaml:"secret,omitempty"`
+		TLS    struct {
+			Certificate string   `yaml:"certificate,omitempty"`
+			Key         string   `yaml:"key,omitempty"`
+			ClientCAs   []string `yaml:"clientcas,omitempty"`
+		} `yaml:"tls,omitempty"`
+		Debug struct {
+			Addr string `yaml:"addr,omitempty"`
+		} `yaml:"debug,omitempty"`
+	}{
+		TLS: struct {
+			Certificate string   `yaml:"certificate,omitempty"`
+			Key         string   `yaml:"key,omitempty"`
+			ClientCAs   []string `yaml:"clientcas,omitempty"`
+		}{
+			ClientCAs: []string{"/path/to/ca.pem"},
+		},
+	},
 }
 
 // configYamlV0_1 is a Version 0.1 yaml document representing configStruct
@@ -82,6 +103,9 @@ notifications:
 reporting:
   bugsnag:
     apikey: BugsnagApiKey
+http:
+  clientcas:
+    - /path/to/ca.pem
 `
 
 // inmemoryConfigYamlV0_1 is a Version 0.1 yaml document specifying an inmemory
diff --git a/doc/configuration.md b/doc/configuration.md
index f9cbf197..b431869d 100644
--- a/doc/configuration.md
+++ b/doc/configuration.md
@@ -62,6 +62,9 @@ http:
 	tls:
 		certificate: /path/to/x509/public
 		key: /path/to/x509/private
+    clientcas:
+      - /path/to/ca.pem
+      - /path/to/another/ca.pem
 	debug:
 		addr: localhost:5001
 notifications:
@@ -260,6 +263,9 @@ http:
 	tls:
 		certificate: /path/to/x509/public
 		key: /path/to/x509/private
+    clientcas:
+      - /path/to/ca.pem
+      - /path/to/another/ca.pem
 	debug:
 		addr: localhost:5001
 ```
@@ -276,6 +282,7 @@ The tls option within http is **optional** and allows you to configure SSL for t
 
 - certificate: **Required** - Absolute path to x509 cert file
 - key: **Required** - Absolute path to x509 private key file
+- clientcas: **Optional** - An array of absolute paths to a x509 CA file
 
 ### debug