Add client certificate, require client certificate verification

arbnode/dataposter/data_poster.go

@@ -175,22 +175,32 @@ func NewDataPoster(ctx context.Context, opts *DataPosterOpts) (*DataPoster, erro
 }
 
 func rpcClient(ctx context.Context, opts *ExternalSignerCfg) (*rpc.Client, error) {
-	rootCrt, err := os.ReadFile(opts.RootCA)
+	clientCert, err := tls.LoadX509KeyPair(opts.ClientCert, opts.ClientPrivateKey)
 	if err != nil {
-		return nil, fmt.Errorf("error reading external signer root CA: %w", err)
+		return nil, fmt.Errorf("error loading client certificate and private key: %w", err)
 	}
-	pool := x509.NewCertPool()
-	pool.AppendCertsFromPEM(rootCrt)
+
+	tlsCfg := &tls.Config{
+		MinVersion:   tls.VersionTLS12,
+		Certificates: []tls.Certificate{clientCert},
+	}
+	if opts.RootCA != "" {
+		rootCrt, err := os.ReadFile(opts.RootCA)
+		if err != nil {
+			return nil, fmt.Errorf("error reading external signer root CA: %w", err)
+		}
+		rootCertPool := x509.NewCertPool()
+		rootCertPool.AppendCertsFromPEM(rootCrt)
+		tlsCfg.RootCAs = rootCertPool
+	}
+
 	return rpc.DialOptions(
 		ctx,
 		opts.URL,
 		rpc.WithHTTPClient(
 			&http.Client{
 				Transport: &http.Transport{
-					TLSClientConfig: &tls.Config{
-						MinVersion: tls.VersionTLS12,
-						RootCAs:    pool,
-					},
+					TLSClientConfig: tlsCfg,
 				},
 			},
 		),
@@ -743,9 +753,13 @@ type ExternalSignerCfg struct {
 	Address string `koanf:"address"`
 	// API method name (e.g. eth_signTransaction).
 	Method string `koanf:"method"`
-	// Path to the external signer root CA certificate.
+	// (Optional) Path to the external signer root CA certificate.
 	// This allows us to use self-signed certificats on the external signer.
 	RootCA string `koanf:"root-ca"`
+	// Client certificate for mtls.
+	ClientCert string `koanf:"client-cert"`
+	// Client certificate key for mtls.
+	ClientPrivateKey string `koanf:"client-private-key"`
 }
 
 type DangerousConfig struct {
@@ -788,6 +802,8 @@ func addExternalSignerOptions(prefix string, f *pflag.FlagSet) {
 	f.String(prefix+".address", DefaultDataPosterConfig.ExternalSigner.Address, "external signer address")
 	f.String(prefix+".method", DefaultDataPosterConfig.ExternalSigner.Method, "external signer method")
 	f.String(prefix+".root-ca", DefaultDataPosterConfig.ExternalSigner.RootCA, "external signer root CA")
+	f.String(prefix+".client-cert", DefaultDataPosterConfig.ExternalSigner.ClientCert, "rpc client cert")
+	f.String(prefix+".client-private-key", DefaultDataPosterConfig.ExternalSigner.ClientPrivateKey, "rpc client private key")
 }
 
 var DefaultDataPosterConfig = DataPosterConfig{

arbnode/dataposter/dataposter_test.go

@@ -2,6 +2,8 @@ package dataposter
 
 import (
 	"context"
+	"crypto/tls"
+	"crypto/x509"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -74,10 +76,12 @@ func TestExternalSigner(t *testing.T) {
 	}()
 	signer, addr, err := externalSigner(ctx,
 		&ExternalSignerCfg{
-			Address: srv.address.Hex(),
-			URL:     "https://localhost:1234",
-			Method:  "test_signTransaction",
-			RootCA:  cert,
+			Address:          srv.address.Hex(),
+			URL:              "https://localhost:1234",
+			Method:           "test_signTransaction",
+			RootCA:           cert,
+			ClientCert:       "./testdata/client.crt",
+			ClientPrivateKey: "./testdata/client.key",
 		})
 	if err != nil {
 		t.Fatalf("Error getting external signer: %v", err)
@@ -129,7 +133,24 @@ func newServer(ctx context.Context, t *testing.T) (*http.Server, *server) {
 		"test_signTransaction": s.signTransaction,
 	}
 	m := http.NewServeMux()
-	httpSrv := &http.Server{Addr: ":1234", Handler: m, ReadTimeout: 5 * time.Second}
+
+	clientCert, err := os.ReadFile("./testdata/client.crt")
+	if err != nil {
+		panic(err)
+	}
+	pool := x509.NewCertPool()
+	pool.AppendCertsFromPEM(clientCert)
+
+	httpSrv := &http.Server{
+		Addr:        ":1234",
+		Handler:     m,
+		ReadTimeout: 5 * time.Second,
+		TLSConfig: &tls.Config{
+			MinVersion: tls.VersionTLS12,
+			ClientAuth: tls.RequireAndVerifyClientCert,
+			ClientCAs:  pool,
+		},
+	}
 	m.HandleFunc("/", s.mux)
 	return httpSrv, s
 }

arbnode/dataposter/testdata/client.cnf

@@ -0,0 +1,52 @@
+[req]
+default_bits       = 2048
+default_keyfile    = server-key.pem
+distinguished_name = subject
+req_extensions     = req_ext
+x509_extensions    = x509_ext
+string_mask        = utf8only
+
+[subject]
+countryName                 = CH
+countryName_default         = CH
+
+stateOrProvinceName         = Zurich
+stateOrProvinceName_default = ZH
+
+localityName                = city
+localityName_default        = Zurich
+
+organizationName            = Offchain Labs
+organizationName_default    = Offchain Labs
+
+commonName                  = offchainlabs.ch
+commonName_default          = localhost
+
+emailAddress                = Email Address
+emailAddress_default        = [email protected]
+
+[x509_ext]
+subjectKeyIdentifier   = hash
+authorityKeyIdentifier = keyid,issuer
+
+basicConstraints       = CA:FALSE
+keyUsage               = digitalSignature, keyEncipherment
+subjectAltName         = @alternate_names
+nsComment              = "OpenSSL Generated Certificate"
+
+[req_ext]
+subjectKeyIdentifier = hash
+
+basicConstraints     = CA:FALSE
+keyUsage             = digitalSignature, keyEncipherment
+subjectAltName       = @alternate_names
+nsComment            = "OpenSSL Generated Certificate"
+
+[alternate_names]
+DNS.1 = localhost
+DNS.2 = 127.0.0.1
+
+[alternate_names]
+DNS.1 = localhost
+DNS.2 = 127.0.0.1
+

arbnode/dataposter/testdata/client.crt

@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
+MIIE0jCCA7qgAwIBAgIUPaBB3/hHMpZfGB3VOw1+mHG4LnUwDQYJKoZIhvcNAQEL
+BQAwgYMxCzAJBgNVBAYTAkNIMQswCQYDVQQIDAJaSDEPMA0GA1UEBwwGWnVyaWNo
+MRYwFAYDVQQKDA1PZmZjaGFpbiBMYWJzMRIwEAYDVQQDDAlsb2NhbGhvc3QxKjAo
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+CAwCWkgxDzANBgNVBAcMBlp1cmljaDEWMBQGA1UECgwNT2ZmY2hhaW4gTGFiczES
+MBAGA1UEAwwJbG9jYWxob3N0MSowKAYJKoZIhvcNAQkBFhtub3RhYmlnZGVhbEBv
+ZmZjaGFpbmxhYnMuY2gwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQC1
+1asfUzv07QTVwlM4o3g51ilIFEApPkpdQej/GIItLEVRQW+GI9jYuEM07wdwMhSH
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+Z2RlYWxAb2ZmY2hhaW5sYWJzLmNoghQ9oEHf+Ecyll8YHdU7DX6YcbgudTAJBgNV
+HRMEAjAAMAsGA1UdDwQEAwIFoDAfBgNVHREEGDAWgglsb2NhbGhvc3SCCTEyNy4w
+LjAuMTAsBglghkgBhvhCAQ0EHxYdT3BlblNTTCBHZW5lcmF0ZWQgQ2VydGlmaWNh
+dGUwDQYJKoZIhvcNAQELBQADggEBAF4EVkOZZeMIvv0JViP7NsmIl2ke/935x6Hd
+hQiLUw13XHYXzMa5/8Y5fnKjttBODpFoQlwjgI18vzuYzItYMBc2cabQJcpfG+Wq
+M3m/wl1TC2XOuHj1E4RA/nU3tslntahtXG+vkks9RN+f9irHUhDRR6AGSnSB2Gi/
+B2OGmXn7S4Qge8+fGHAjN+tlu+tOoEWP6R3if/a9UIe5EGM8QTe4zw6lr+iPrOhC
+M94pK5IEWn5IIGhr3zJIYkm/Dp+rFqhV1sqPOjjFLVCA7KJ3jVVVHlcm4Xa/+fyk
+CIm7/VAmnbeUNlMbkXNOfQMeku8Iwsu80pvf3kjhU/PgO/5oojk=
+-----END CERTIFICATE-----

arbnode/dataposter/testdata/client.key

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvwIBADANBgkqhkiG9w0BAQEFAASCBKkwggSlAgEAAoIBAQC11asfUzv07QTV
+wlM4o3g51ilIFEApPkpdQej/GIItLEVRQW+GI9jYuEM07wdwMhSHJPFNbZB3dmBu
+qDLx13hY03ufyeY+nab0/sO6x13kXChvIqgPRyJtkEAoYkMM3W0DS6HeL/6DFoTQ
+2xAlZb/7i/9deuUwDL3MNVSjPCm9PjFzSOFgAQQud2uUT7aENGuGWhw3oXz9gU/8
+gv3keLzcIa2PHyEW5M7jeGSYMjfW3wr0d+Z5mSNRc/U6kncKi06cQrMKrgFfF7a5
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++hmZj5IpgMJZLrgvWY4s+PGfgiRR/28QCBrVXkETiZ5zirQFN4tvLlKcSK4xZf29
+FBRUCiPxck36NhiqrBNOi1Mn8BKedl4cESkvSu1cvcmeOh100HPcHfLDVqHx3qsl
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+nFoSa/XNHaa8y7jmmlCnWJqs6DAAQQ3VW0tPX03GYL/NDcI+PwzYDHDkSB6Qa/o8
+VzVGK1/kr/+bveNvqmi0vNb54fMFLveGgsY4Cu1cffiw8m6nYJ/V4eCsHfpF1B5L
+5HDnt5rFKt1Mi9WsUSRtxipxBA==
+-----END PRIVATE KEY-----