Add TLS to the server side, expose optional root certificate path on client side

arbnode/dataposter/data_poster.go

@@ -6,9 +6,13 @@ package dataposter
 
 import (
 	"context"
+	"crypto/tls"
+	"crypto/x509"
 	"errors"
 	"fmt"
 	"math/big"
+	"net/http"
+	"os"
 	"strings"
 	"sync"
 	"time"
@@ -170,18 +174,42 @@ func NewDataPoster(ctx context.Context, opts *DataPosterOpts) (*DataPoster, erro
 	return dp, nil
 }
 
+func rpcClient(ctx context.Context, opts *ExternalSignerCfg) (*rpc.Client, error) {
+	rootCrt, err := os.ReadFile(opts.RootCA)
+	if err != nil {
+		return nil, fmt.Errorf("error reading external signer root CA: %w", err)
+	}
+	pool := x509.NewCertPool()
+	pool.AppendCertsFromPEM(rootCrt)
+	return rpc.DialOptions(
+		ctx,
+		opts.URL,
+		rpc.WithHTTPClient(
+			&http.Client{
+				Transport: &http.Transport{
+					TLSClientConfig: &tls.Config{
+						MinVersion: tls.VersionTLS12,
+						RootCAs:    pool,
+					},
+				},
+			},
+		),
+	)
+}
+
 // externalSigner returns signer function and ethereum address of the signer.
 // Returns an error if address isn't specified or if it can't connect to the
 // signer RPC server.
 func externalSigner(ctx context.Context, opts *ExternalSignerCfg) (signerFn, common.Address, error) {
 	if opts.Address == "" {
 		return nil, common.Address{}, errors.New("external signer (From) address specified")
 	}
-	sender := common.HexToAddress(opts.Address)
-	client, err := rpc.DialContext(ctx, opts.URL)
+
+	client, err := rpcClient(ctx, opts)
 	if err != nil {
 		return nil, common.Address{}, fmt.Errorf("error connecting external signer: %w", err)
 	}
+	sender := common.HexToAddress(opts.Address)
 
 	var hasher types.Signer
 	return func(ctx context.Context, addr common.Address, tx *types.Transaction) (*types.Transaction, error) {
@@ -715,6 +743,9 @@ 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.
+	// This allows us to use self-signed certificats on the external signer.
+	RootCA string `koanf:"root-ca"`
 }
 
 type DangerousConfig struct {
@@ -756,6 +787,7 @@ func addExternalSignerOptions(prefix string, f *pflag.FlagSet) {
 	f.String(prefix+".url", DefaultDataPosterConfig.ExternalSigner.URL, "external signer url")
 	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")
 }
 
 var DefaultDataPosterConfig = DataPosterConfig{

arbnode/dataposter/dataposter_test.go

@@ -64,18 +64,20 @@ func TestExternalSigner(t *testing.T) {
 			t.Fatalf("Error shutting down http server: %v", err)
 		}
 	})
+	cert, key := "./testdata/localhost.crt", "./testdata/localhost.key"
 	go func() {
 		fmt.Println("Server is listening on port 1234...")
-		if err := httpSrv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
-			t.Errorf("ListenAndServe() unexpected error:  %v", err)
+		if err := httpSrv.ListenAndServeTLS(cert, key); err != nil && err != http.ErrServerClosed {
+			t.Errorf("ListenAndServeTLS() unexpected error:  %v", err)
 			return
 		}
 	}()
 	signer, addr, err := externalSigner(ctx,
 		&ExternalSignerCfg{
 			Address: srv.address.Hex(),
-			URL:     "http://127.0.0.1:1234",
+			URL:     "https://localhost:1234",
 			Method:  "test_signTransaction",
+			RootCA:  cert,
 		})
 	if err != nil {
 		t.Fatalf("Error getting external signer: %v", err)

arbnode/dataposter/testdata/localhost.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/localhost.crt

@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
+MIIEwzCCA6ugAwIBAgIUHx3SdpCP5jXZE7USUqX5uRNFKPIwDQYJKoZIhvcNAQEL
+BQAwfzELMAkGA1UEBhMCQ0gxCzAJBgNVBAgMAlpIMQ8wDQYDVQQHDAZadXJpY2gx
+FjAUBgNVBAoMDU9mZmNoYWluIExhYnMxEjAQBgNVBAMMCWxvY2FsaG9zdDEmMCQG
+CSqGSIb3DQEJARYXYmlnZGVhbEBvZmZjaGFpbmxhYnMuY2gwHhcNMjMxMDE2MTQ0
+MDA1WhcNMjQxMDE1MTQ0MDA1WjB/MQswCQYDVQQGEwJDSDELMAkGA1UECAwCWkgx
+DzANBgNVBAcMBlp1cmljaDEWMBQGA1UECgwNT2ZmY2hhaW4gTGFiczESMBAGA1UE
+AwwJbG9jYWxob3N0MSYwJAYJKoZIhvcNAQkBFhdiaWdkZWFsQG9mZmNoYWlubGFi
+cy5jaDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBALg7XwaIh4l2Fp8a
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+YWJzLmNoghQfHdJ2kI/mNdkTtRJSpfm5E0Uo8jAJBgNVHRMEAjAAMAsGA1UdDwQE
+AwIFoDAfBgNVHREEGDAWgglsb2NhbGhvc3SCCTEyNy4wLjAuMTAsBglghkgBhvhC
+AQ0EHxYdT3BlblNTTCBHZW5lcmF0ZWQgQ2VydGlmaWNhdGUwDQYJKoZIhvcNAQEL
+BQADggEBAIkhBcnLeeNwUwb+sSG4Qm8JdeplHPMeViNfFIflUfIIYS00JA2q9w8W
++6Nh8s6Dn20lQETUnesYj97BdqzLjFuJYAlblhE+zP8g/3Mkpu+wZAGvQjUIRyGT
+C17BEtQQgAnv5pD22jr9hpLl2KowN6Oo1gzilCA+AtMkNZFIGDOxzuIv2u8rSD89
+R/V6UEDMCgusFJnZ/GzKkUNbsrAfNUezNUal+KzMhHGHBwg4jfCNhnAAB43eRtJA
+0pSRMMLcUEQnVotXDXYC3DhJmkYp1uXOH/tWs6z9xForOkWFxNMVj+zUWBi7n3Jw
+N2BXlb64D96uor13U0dmvQJ72ooJc+A=
+-----END CERTIFICATE-----

arbnode/dataposter/testdata/localhost.key

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQC4O18GiIeJdhaf
+GjHzTHU0EjDzEdM6Z4nFU5/3oqM1rKpQCmsZkDNz8SdKFVlt4ifPaeK7+ZvlIyug
+677FEDs5fIrIMhgkzJ5C7cRZcmpZQzUQ2sEXLkz7jSPTZHSZvmc+x6KC8xXgQ3kt
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+1e7NdNIKw3fP/J4UrHk7btAm65us8hSCeMGatEErAhNZT0gR4zhcksMCBPQLkVIT
++HINYjdOzAJqoEbRRUnaVT5VDQy8HmyLCtyqhoGR18XbjshNnhKLYKCJ2z0Lrvf2
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+KDmww0xr8dyMUYTP1vde7np2XKa/OX3iejDzbI3RcZN/DEV+dCBY8pqHHfaAaESu
+fwBWvfD8wtwCZzB3lOZEi80=
+-----END PRIVATE KEY-----