[client] Add mTLS support for SSO login (#2188)

* Add mTLS support for SSO login
* Refactor variable to follow Go naming conventions

---------

Co-authored-by: bcmmbaga <bethuelmbaga12@gmail.com>

client/android/login.go

@@ -84,7 +84,7 @@ func (a *Auth) SaveConfigIfSSOSupported(listener SSOListener) {
 func (a *Auth) saveConfigIfSSOSupported() (bool, error) {
 	supportsSSO := true
 	err := a.withBackOff(a.ctx, func() (err error) {
-		_, err = internal.GetPKCEAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL)
+		_, err = internal.GetPKCEAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL, nil)
 		if s, ok := gstatus.FromError(err); ok && (s.Code() == codes.NotFound || s.Code() == codes.Unimplemented) {
 			_, err = internal.GetDeviceAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL)
 			s, ok := gstatus.FromError(err)

client/internal/auth/oauth.go

@@ -86,7 +86,7 @@ func NewOAuthFlow(ctx context.Context, config *internal.Config, isLinuxDesktopCl
 
 // authenticateWithPKCEFlow initializes the Proof Key for Code Exchange flow auth flow
 func authenticateWithPKCEFlow(ctx context.Context, config *internal.Config) (OAuthFlow, error) {
-	pkceFlowInfo, err := internal.GetPKCEAuthorizationFlowInfo(ctx, config.PrivateKey, config.ManagementURL)
+	pkceFlowInfo, err := internal.GetPKCEAuthorizationFlowInfo(ctx, config.PrivateKey, config.ManagementURL, config.ClientCertKeyPair)
 	if err != nil {
 		return nil, fmt.Errorf("getting pkce authorization flow info failed with error: %v", err)
 	}

client/internal/auth/pkce_flow.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/sha256"
 	"crypto/subtle"
+	"crypto/tls"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -143,6 +144,18 @@ func (p *PKCEAuthorizationFlow) WaitToken(ctx context.Context, _ AuthFlowInfo) (
 func (p *PKCEAuthorizationFlow) startServer(server *http.Server, tokenChan chan<- *oauth2.Token, errChan chan<- error) {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
+		cert := p.providerConfig.ClientCertPair
+		if cert != nil {
+			tr := &http.Transport{
+				TLSClientConfig: &tls.Config{
+					Certificates: []tls.Certificate{*cert},
+				},
+			}
+			sslClient := &http.Client{Transport: tr}
+			ctx := context.WithValue(req.Context(), oauth2.HTTPClient, sslClient)
+			req = req.WithContext(ctx)
+		}
+
 		token, err := p.handleRequest(req)
 		if err != nil {
 			renderPKCEFlowTmpl(w, err)

client/internal/config.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"net/url"
 	"os"
@@ -57,6 +58,8 @@ type ConfigInput struct {
 	DisableAutoConnect  *bool
 	ExtraIFaceBlackList []string
 	DNSRouteInterval    *time.Duration
+	ClientCertPath      string
+	ClientCertKeyPath   string
 }
 
 // Config Configuration type
@@ -102,6 +105,13 @@ type Config struct {
 
 	// DNSRouteInterval is the interval in which the DNS routes are updated
 	DNSRouteInterval time.Duration
+	//Path to a certificate used for mTLS authentication
+	ClientCertPath string
+
+	//Path to corresponding private key of ClientCertPath
+	ClientCertKeyPath string
+
+	ClientCertKeyPair *tls.Certificate `json:"-"`
 }
 
 // ReadConfig read config file and return with Config. If it is not exists create a new with default values
@@ -385,6 +395,26 @@ func (config *Config) apply(input ConfigInput) (updated bool, err error) {
 
 	}
 
+	if input.ClientCertKeyPath != "" {
+		config.ClientCertKeyPath = input.ClientCertKeyPath
+		updated = true
+	}
+
+	if input.ClientCertPath != "" {
+		config.ClientCertPath = input.ClientCertPath
+		updated = true
+	}
+
+	if config.ClientCertPath != "" && config.ClientCertKeyPath != "" {
+		cert, err := tls.LoadX509KeyPair(config.ClientCertPath, config.ClientCertKeyPath)
+		if err != nil {
+			log.Error("Failed to load mTLS cert/key pair: ", err)
+		} else {
+			config.ClientCertKeyPair = &cert
+			log.Info("Loaded client mTLS cert/key pair")
+		}
+	}
+
 	return updated, nil
 }
 

client/internal/pkce_auth.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"net/url"
 
@@ -36,10 +37,12 @@ type PKCEAuthProviderConfig struct {
 	RedirectURLs []string
 	// UseIDToken indicates if the id token should be used for authentication
 	UseIDToken bool
+	//ClientCertPair is used for mTLS authentication to the IDP
+	ClientCertPair *tls.Certificate
 }
 
 // GetPKCEAuthorizationFlowInfo initialize a PKCEAuthorizationFlow instance and return with it
-func GetPKCEAuthorizationFlowInfo(ctx context.Context, privateKey string, mgmURL *url.URL) (PKCEAuthorizationFlow, error) {
+func GetPKCEAuthorizationFlowInfo(ctx context.Context, privateKey string, mgmURL *url.URL, clientCert *tls.Certificate) (PKCEAuthorizationFlow, error) {
 	// validate our peer's Wireguard PRIVATE key
 	myPrivateKey, err := wgtypes.ParseKey(privateKey)
 	if err != nil {
@@ -93,6 +96,7 @@ func GetPKCEAuthorizationFlowInfo(ctx context.Context, privateKey string, mgmURL
 			Scope:                 protoPKCEAuthorizationFlow.GetProviderConfig().GetScope(),
 			RedirectURLs:          protoPKCEAuthorizationFlow.GetProviderConfig().GetRedirectURLs(),
 			UseIDToken:            protoPKCEAuthorizationFlow.GetProviderConfig().GetUseIDToken(),
+			ClientCertPair:        clientCert,
 		},
 	}
 

client/ios/NetBirdSDK/login.go

@@ -74,7 +74,7 @@ func (a *Auth) SaveConfigIfSSOSupported() (bool, error) {
 	err := a.withBackOff(a.ctx, func() (err error) {
 		_, err = internal.GetDeviceAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL)
 		if s, ok := gstatus.FromError(err); ok && (s.Code() == codes.NotFound || s.Code() == codes.Unimplemented) {
-			_, err = internal.GetPKCEAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL)
+			_, err = internal.GetPKCEAuthorizationFlowInfo(a.ctx, a.config.PrivateKey, a.config.ManagementURL, nil)
 			if s, ok := gstatus.FromError(err); ok && (s.Code() == codes.NotFound || s.Code() == codes.Unimplemented) {
 				supportsSSO = false
 				err = nil