Support for per-vu TLS configuration (grpc.Client.connect only) (#3159)

You can also now use per-vu TLS configuration on `grpc.Client` `connect` params. Previously, `grpc.Client` `connect` made use of a shared (immutable) `tls.Config` cloned into every VU. Now, the `connect` `params` argument can contain a `tlsconfig` key that maps to the `TLSAuth` struct. This will create a per-vu TLS configuration for the `grpc.Client` allowing you to connect to multiple mTLS endpoints in a single VU. Note: the global tls.Config will remain unmodified.

```javascript
const params = {
    plaintext: false,
    tlsconfig: {
        cacerts: ["cacerts.pem"],
        cert: "cert.pem",
        key: "key.pem",
        password: "cert-passphrase",
        domains: ["grpcbin.test.notk6.io"], // Deprecated
    }
};
const hostPort = "grpcbin.test.notk6.io:9001";
const client = new grpc.Client();

client.connect(hostPort, params);
```


Co-authored-by: Mihail Stoykov <312246+mstoykov@users.noreply.github.com>
Co-authored-by: Oleg Bespalov <olegbespalov@gmail.com>

js/modules/k6/grpc/client.go

@@ -2,6 +2,9 @@ package grpc
 
 import (
 	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/pem"
 	"errors"
 	"fmt"
 	"io"
@@ -108,6 +111,101 @@ func (c *Client) LoadProtoset(protosetPath string) ([]MethodInfo, error) {
 	return c.convertToMethodInfo(fdset)
 }
 
+// Note: this function was lifted from `lib/options.go`
+func decryptPrivateKey(key, password []byte) ([]byte, error) {
+	block, _ := pem.Decode(key)
+	if block == nil {
+		return nil, errors.New("failed to decode PEM key")
+	}
+
+	blockType := block.Type
+	if blockType == "ENCRYPTED PRIVATE KEY" {
+		return nil, errors.New("encrypted pkcs8 formatted key is not supported")
+	}
+	/*
+	   Even though `DecryptPEMBlock` has been deprecated since 1.16.x it is still
+	   being used here because it is deprecated due to it not supporting *good* cryptography
+	   ultimately though we want to support something so we will be using it for now.
+	*/
+	decryptedKey, err := x509.DecryptPEMBlock(block, password) //nolint:staticcheck
+	if err != nil {
+		return nil, err
+	}
+	key = pem.EncodeToMemory(&pem.Block{
+		Type:  blockType,
+		Bytes: decryptedKey,
+	})
+	return key, nil
+}
+
+func buildTLSConfig(parentConfig *tls.Config, certificate, key []byte, caCertificates [][]byte) (*tls.Config, error) {
+	var cp *x509.CertPool
+	if len(caCertificates) > 0 {
+		cp, _ = x509.SystemCertPool()
+		for i, caCert := range caCertificates {
+			if ok := cp.AppendCertsFromPEM(caCert); !ok {
+				return nil, fmt.Errorf("failed to append ca certificate [%d] from PEM", i)
+			}
+		}
+	}
+
+	// Ignoring 'TLS MinVersion is too low' because this tls.Config will inherit MinValue and MaxValue
+	// from the vu state tls.Config
+
+	//nolint:golint,gosec
+	tlsCfg := &tls.Config{
+		CipherSuites:       parentConfig.CipherSuites,
+		InsecureSkipVerify: parentConfig.InsecureSkipVerify,
+		MinVersion:         parentConfig.MinVersion,
+		MaxVersion:         parentConfig.MaxVersion,
+		Renegotiation:      parentConfig.Renegotiation,
+		RootCAs:            cp,
+	}
+	if len(certificate) > 0 && len(key) > 0 {
+		cert, err := tls.X509KeyPair(certificate, key)
+		if err != nil {
+			return nil, fmt.Errorf("failed to append certificate from PEM: %w", err)
+		}
+		tlsCfg.Certificates = []tls.Certificate{cert}
+	}
+	return tlsCfg, nil
+}
+
+func buildTLSConfigFromMap(parentConfig *tls.Config, tlsConfigMap map[string]interface{}) (*tls.Config, error) {
+	var cert, key, pass []byte
+	var ca [][]byte
+	var err error
+	if certstr, ok := tlsConfigMap["cert"].(string); ok {
+		cert = []byte(certstr)
+	}
+	if keystr, ok := tlsConfigMap["key"].(string); ok {
+		key = []byte(keystr)
+	}
+	if passwordStr, ok := tlsConfigMap["password"].(string); ok {
+		pass = []byte(passwordStr)
+		if len(pass) > 0 {
+			if key, err = decryptPrivateKey(key, pass); err != nil {
+				return nil, err
+			}
+		}
+	}
+	if cas, ok := tlsConfigMap["cacerts"]; ok {
+		var caCertsArray []interface{}
+		if caCertsArray, ok = cas.([]interface{}); ok {
+			ca = make([][]byte, len(caCertsArray))
+			for i, entry := range caCertsArray {
+				var entryStr string
+				if entryStr, ok = entry.(string); ok {
+					ca[i] = []byte(entryStr)
+				}
+			}
+		} else if caCertStr, caCertStrOk := cas.(string); caCertStrOk {
+			ca = [][]byte{[]byte(caCertStr)}
+		}
+	}
+	return buildTLSConfig(parentConfig, cert, key, ca)
+}
+
 // Connect is a block dial to the gRPC server at the given address (host:port)
 func (c *Client) Connect(addr string, params map[string]interface{}) (bool, error) {
 	state := c.vu.State()
@@ -125,9 +223,13 @@ func (c *Client) Connect(addr string, params map[string]interface{}) (bool, erro
 	var tcred credentials.TransportCredentials
 	if !p.IsPlaintext {
 		tlsCfg := state.TLSConfig.Clone()
+		if len(p.TLS) > 0 {
+			if tlsCfg, err = buildTLSConfigFromMap(tlsCfg, p.TLS); err != nil {
+				return false, err
+			}
+		}
 		tlsCfg.NextProtos = []string{"h2"}
 
-		// TODO(rogchap): Would be good to add support for custom RootCAs (self signed)
 		tcred = credentials.NewTLS(tlsCfg)
 	} else {
 		tcred = insecure.NewCredentials()
@@ -387,6 +489,7 @@ type connectParams struct {
 	Timeout               time.Duration
 	MaxReceiveSize        int64
 	MaxSendSize           int64
+	TLS                   map[string]interface{}
 }
 
 func (c *Client) parseConnectParams(raw map[string]interface{}) (connectParams, error) {
@@ -435,7 +538,43 @@ func (c *Client) parseConnectParams(raw map[string]interface{}) (connectParams,
 			if params.MaxSendSize < 0 {
 				return params, fmt.Errorf("invalid maxSendSize value: '%#v, it needs to be a positive integer", v)
 			}
+		case "tls":
+			var ok bool
+			params.TLS, ok = v.(map[string]interface{})
 
+			if !ok {
+				return params, fmt.Errorf("invalid tls value: '%#v', expected (optional) keys: cert, key, password, and cacerts", v)
+			}
+			// optional map keys below
+			if cert, certok := params.TLS["cert"]; certok {
+				if _, ok = cert.(string); !ok {
+					return params, fmt.Errorf("invalid tls cert value: '%#v', it needs to be a PEM formatted string", v)
+				}
+			}
+			if key, keyok := params.TLS["key"]; keyok {
+				if _, ok = key.(string); !ok {
+					return params, fmt.Errorf("invalid tls key value: '%#v', it needs to be a PEM formatted string", v)
+				}
+			}
+			if pass, passok := params.TLS["password"]; passok {
+				if _, ok = pass.(string); !ok {
+					return params, fmt.Errorf("invalid tls password value: '%#v', it needs to be a string", v)
+				}
+			}
+			if cacerts, cacertsok := params.TLS["cacerts"]; cacertsok {
+				var cacertsArray []interface{}
+				if cacertsArray, ok = cacerts.([]interface{}); ok {
+					for _, cacertsArrayEntry := range cacertsArray {
+						if _, ok = cacertsArrayEntry.(string); !ok {
+							return params, fmt.Errorf("invalid tls cacerts value: '%#v',"+
+								" it needs to be a string or an array of PEM formatted strings", v)
+						}
+					}
+				} else if _, ok = cacerts.(string); !ok {
+					return params, fmt.Errorf("invalid tls cacerts value: '%#v',"+
+						" it needs to be a string or an array of PEM formatted strings", v)
+				}
+			}
 		default:
 			return params, fmt.Errorf("unknown connect param: %q", k)
 		}