Improve SSL support

Related issue: https://github.com/github/gh-ost/issues/521

 - Add --ssl-cert and --ssl-key options to specify SSL public/private
   key files
 - Allow combining --ssl-allow-insecure with other --ssl* flags.
   `mysql.RegisterTLSConfig` allows combining the corresponding
   parameters in the `tls.Config` it receives, so gh-ost should
   allow this. I found being able to pass --ssl-allow-insecure along
   with --ssl-ca, --ssl-cert, and --ssl-key useful in testing.
 - Use the same TLS config everywhere. Since the CLI only supports
   a single set of --ssl* configuration parameters, this should be
   fine -- `mysql.RegisterTLSConfig` documentation indicates the
   TLS config given will not be modified, so it can safely be used
   in many goroutines provided we also do not modify it. The previous
   implementation did not work when the TLS config was duplicated,
   which happens when gh-ost walks up the replication chain trying
   to find the master. This is because, when the config is duplicated,
   we must call `RegisterTLSConfig` again with the new config. This
   config is exactly the same, so it's easiest to side-step the issue
   by registering the TLS config once and using it everywhere.

doc/command-line-flags.md

@@ -189,6 +189,14 @@ Allows `gh-ost` to connect to the MySQL servers using encrypted connections, but
 
 `--ssl-ca=/path/to/ca-cert.pem`: ca certificate file (in PEM format) to use for server certificate verification. If specified, the default system ca cert pool will not be used for verification, only the ca cert provided here. Requires `--ssl`.
 
+### ssl-cert
+
+`--ssl-cert=/path/to/ssl-cert.crt`: SSL public key certificate file (in PEM format).
+
+### ssl-key
+
+`--ssl-key=/path/to/ssl-key.key`: SSL private key file (in PEM format).
+
 ### test-on-replica
 
 Issue the migration on a replica; do not modify data on master. Useful for validating, testing and benchmarking. See [`testing-on-replica`](testing-on-replica.md)

go/base/context.go

@@ -102,6 +102,8 @@ type MigrationContext struct {
 	UseTLS            bool
 	TLSAllowInsecure  bool
 	TLSCACertificate  string
+	TLSCertificate    string
+	TLSKey            string
 	CliMasterUser     string
 	CliMasterPassword string
 
@@ -702,7 +704,7 @@ func (this *MigrationContext) ApplyCredentials() {
 
 func (this *MigrationContext) SetupTLS() error {
 	if this.UseTLS {
-		return this.InspectorConnectionConfig.UseTLS(this.TLSCACertificate, this.TLSAllowInsecure)
+		return this.InspectorConnectionConfig.UseTLS(this.TLSCACertificate, this.TLSCertificate, this.TLSKey, this.TLSAllowInsecure)
 	}
 	return nil
 }

go/cmd/gh-ost/main.go

@@ -57,6 +57,8 @@ func main() {
 
 	flag.BoolVar(&migrationContext.UseTLS, "ssl", false, "Enable SSL encrypted connections to MySQL hosts")
 	flag.StringVar(&migrationContext.TLSCACertificate, "ssl-ca", "", "CA certificate in PEM format for TLS connections to MySQL hosts. Requires --ssl")
+	flag.StringVar(&migrationContext.TLSCertificate, "ssl-cert", "", "Certificate in PEM format for TLS connections to MySQL hosts. Requires --ssl")
+	flag.StringVar(&migrationContext.TLSKey, "ssl-key", "", "Key in PEM format for TLS connections to MySQL hosts. Requires --ssl")
 	flag.BoolVar(&migrationContext.TLSAllowInsecure, "ssl-allow-insecure", false, "Skips verification of MySQL hosts' certificate chain and host name. Requires --ssl")
 
 	flag.StringVar(&migrationContext.DatabaseName, "database", "", "database name (mandatory)")
@@ -204,6 +206,12 @@ func main() {
 	if migrationContext.TLSCACertificate != "" && !migrationContext.UseTLS {
 		log.Fatalf("--ssl-ca requires --ssl")
 	}
+	if migrationContext.TLSCertificate != "" && !migrationContext.UseTLS {
+		log.Fatalf("--ssl-cert requires --ssl")
+	}
+	if migrationContext.TLSKey != "" && !migrationContext.UseTLS {
+		log.Fatalf("--ssl-key requires --ssl")
+	}
 	if migrationContext.TLSAllowInsecure && !migrationContext.UseTLS {
 		log.Fatalf("--ssl-allow-insecure requires --ssl")
 	}

go/mysql/connection.go

@@ -16,6 +16,10 @@ import (
 	"github.com/go-sql-driver/mysql"
 )
 
+const (
+	TLS_CONFIG_KEY = "ghost"
+)
+
 // ConnectionConfig is the minimal configuration required to connect to a MySQL server
 type ConnectionConfig struct {
 	Key        InstanceKey
@@ -57,11 +61,11 @@ func (this *ConnectionConfig) Equals(other *ConnectionConfig) bool {
 	return this.Key.Equals(&other.Key) || this.ImpliedKey.Equals(other.ImpliedKey)
 }
 
-func (this *ConnectionConfig) UseTLS(caCertificatePath string, allowInsecure bool) error {
+func (this *ConnectionConfig) UseTLS(caCertificatePath, clientCertificate, clientKey string, allowInsecure bool) error {
 	var rootCertPool *x509.CertPool
+	var certs []tls.Certificate
 	var err error
 
-	if !allowInsecure {
 	if caCertificatePath == "" {
 		rootCertPool, err = x509.SystemCertPool()
 		if err != nil {
@@ -77,14 +81,21 @@ func (this *ConnectionConfig) UseTLS(caCertificatePath string, allowInsecure boo
 			return errors.New("could not add ca certificate to cert pool")
 		}
 	}
+	if clientCertificate != "" || clientKey != "" {
+		cert, err := tls.LoadX509KeyPair(clientCertificate, clientKey)
+		if err != nil {
+			return err
+		}
+		certs = []tls.Certificate{cert}
 	}
 
 	this.tlsConfig = &tls.Config{
+		Certificates:       certs,
 		RootCAs:            rootCertPool,
 		InsecureSkipVerify: allowInsecure,
 	}
 
-	return mysql.RegisterTLSConfig(this.Key.StringCode(), this.tlsConfig)
+	return mysql.RegisterTLSConfig(TLS_CONFIG_KEY, this.tlsConfig)
 }
 
 func (this *ConnectionConfig) TLSConfig() *tls.Config {
@@ -103,7 +114,7 @@ func (this *ConnectionConfig) GetDBUri(databaseName string) string {
 	// simplify construction of the DSN below.
 	tlsOption := "false"
 	if this.tlsConfig != nil {
-		tlsOption = this.Key.StringCode()
+		tlsOption = TLS_CONFIG_KEY
 	}
 	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?interpolateParams=%t&autocommit=true&charset=utf8mb4,utf8,latin1&tls=%s", this.User, this.Password, hostname, this.Key.Port, databaseName, interpolateParams, tlsOption)
 }

go/mysql/connection_test.go

@@ -80,5 +80,5 @@ func TestGetDBUriWithTLSSetup(t *testing.T) {
 	c.tlsConfig = &tls.Config{}
 
 	uri := c.GetDBUri("test")
-	test.S(t).ExpectEquals(uri, "gromit:penguin@tcp(myhost:3306)/test?interpolateParams=true&autocommit=true&charset=utf8mb4,utf8,latin1&tls=myhost:3306")
+	test.S(t).ExpectEquals(uri, "gromit:penguin@tcp(myhost:3306)/test?interpolateParams=true&autocommit=true&charset=utf8mb4,utf8,latin1&tls=ghost")
 }