Support etcd TLS certficates (#6719)

This PR supports two models for etcd certs

- Client-to-server transport security with HTTPS
- Client-to-server authentication with HTTPS client certificates

cmd/common-main.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"crypto/tls"
 	"errors"
 	"net"
 	"os"
@@ -157,11 +158,27 @@ func handleCommonEnvVars() {
 	etcdEndpointsEnv, ok := os.LookupEnv("MINIO_ETCD_ENDPOINTS")
 	if ok {
 		etcdEndpoints := strings.Split(etcdEndpointsEnv, ",")
+
+		// This is only to support client side certificate authentication
+		// https://coreos.com/etcd/docs/latest/op-guide/security.html
+		etcdClientCertFile, ok1 := os.LookupEnv("MINIO_ETCD_CLIENT_CERT")
+		etcdClientCertKey, ok2 := os.LookupEnv("MINIO_ETCD_CLIENT_CERT_KEY")
+		var getClientCertificate func(*tls.CertificateRequestInfo) (*tls.Certificate, error)
+		if ok1 && ok2 {
+			getClientCertificate = func(unused *tls.CertificateRequestInfo) (*tls.Certificate, error) {
+				cert, err := tls.LoadX509KeyPair(etcdClientCertFile, etcdClientCertKey)
+				return &cert, err
+			}
+		}
 		var err error
 		globalEtcdClient, err = etcd.New(etcd.Config{
 			Endpoints:         etcdEndpoints,
 			DialTimeout:       defaultDialTimeout,
 			DialKeepAliveTime: defaultDialKeepAlive,
+			TLS: &tls.Config{
+				RootCAs:              globalRootCAs,
+				GetClientCertificate: getClientCertificate,
+			},
 		})
 		logger.FatalIf(err, "Unable to initialize etcd with %s", etcdEndpoints)
 	}

cmd/gateway-main.go

@@ -134,9 +134,6 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 	// Handle common command args.
 	handleCommonCmdArgs(ctx)
 
-	// Handle common env vars.
-	handleCommonEnvVars()
-
 	// Get port to listen on from gateway address
 	_, gatewayPort, pErr := net.SplitHostPort(gatewayAddr)
 	if pErr != nil {
@@ -149,11 +146,6 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 	// To avoid this error situation we check for port availability.
 	logger.FatalIf(checkPortAvailability(gatewayPort), "Unable to start the gateway")
 
-	// Validate if we have access, secret set through environment.
-	if !globalIsEnvCreds {
-		logger.Fatal(uiErrEnvCredentialsMissingGateway(nil), "Unable to start gateway")
-	}
-
 	// Create certs path.
 	logger.FatalIf(createConfigDir(), "Unable to create configuration directories")
 
@@ -166,6 +158,14 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 	globalRootCAs, err = getRootCAs(getCADir())
 	logger.FatalIf(err, "Failed to read root CAs (%v)", err)
 
+	// Handle common env vars.
+	handleCommonEnvVars()
+
+	// Validate if we have access, secret set through environment.
+	if !globalIsEnvCreds {
+		logger.Fatal(uiErrEnvCredentialsMissingGateway(nil), "Unable to start gateway")
+	}
+
 	// Set system resources to maximum.
 	logger.LogIf(context.Background(), setMaxResources())
 

cmd/gateway/s3/gateway-s3.go

@@ -203,6 +203,9 @@ func newS3(url string) (*miniogo.Core, error) {
 		return nil, err
 	}
 
+	// Set custom transport
+	clnt.SetCustomTransport(minio.NewCustomHTTPTransport())
+
 	probeBucketName := randString(60, rand.NewSource(time.Now().UnixNano()), "probe-bucket-sign-")
 	// Check if the provided keys are valid.
 	if _, err = clnt.BucketExists(probeBucketName); err != nil {

cmd/server-main.go

@@ -218,12 +218,6 @@ func serverMain(ctx *cli.Context) {
 		logger.EnableQuiet()
 	}
 
-	// Handle all server command args.
-	serverHandleCmdArgs(ctx)
-
-	// Handle all server environment vars.
-	serverHandleEnvVars()
-
 	// Create certs path.
 	logger.FatalIf(createConfigDir(), "Unable to initialize configuration files")
 
@@ -236,6 +230,12 @@ func serverMain(ctx *cli.Context) {
 	globalRootCAs, err = getRootCAs(getCADir())
 	logger.FatalIf(err, "Failed to read root CAs (%v)", err)
 
+	// Handle all server command args.
+	serverHandleCmdArgs(ctx)
+
+	// Handle all server environment vars.
+	serverHandleEnvVars()
+
 	// Is distributed setup, error out if no certificates are found for HTTPS endpoints.
 	if globalIsDistXL {
 		if globalEndpoints.IsHTTPS() && !globalIsSSL {