support proxy db tunnel mfa access

integration/helpers/instance.go

@@ -28,6 +28,12 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gravitational/trace"
+	"github.com/jonboulle/clockwork"
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/crypto/ssh"
+
 	"github.com/gravitational/teleport/api/breaker"
 	"github.com/gravitational/teleport/api/client/proto"
 	"github.com/gravitational/teleport/api/types"
@@ -46,11 +52,6 @@ import (
 	"github.com/gravitational/teleport/lib/sshutils"
 	"github.com/gravitational/teleport/lib/tlsca"
 	"github.com/gravitational/teleport/lib/utils"
-	"github.com/gravitational/trace"
-	"github.com/jonboulle/clockwork"
-	log "github.com/sirupsen/logrus"
-	"github.com/stretchr/testify/require"
-	"golang.org/x/crypto/ssh"
 )
 
 const (
@@ -1214,8 +1215,7 @@ func (i *TeleInstance) NewClientWithCreds(cfg ClientConfig, creds UserCreds) (tc
 	return clt, nil
 }
 
-// NewUnauthenticatedClient returns a fully configured and pre-authenticated client
-// (pre-authenticated with server CAs and signed session key)
+// NewUnauthenticatedClient returns a fully configured and un-authenticated client
 func (i *TeleInstance) NewUnauthenticatedClient(cfg ClientConfig) (tc *client.TeleportClient, err error) {
 	keyDir, err := os.MkdirTemp(i.Config.DataDir, "tsh")
 	if err != nil {
@@ -1274,7 +1274,12 @@ func (i *TeleInstance) NewClient(cfg ClientConfig) (*client.TeleportClient, erro
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}
+	return i.AddClientCredentials(tc, cfg)
+}
 
+// AddClientCredentials adds authenticated credentials to a client.
+// (server CAs and signed session key).
+func (i *TeleInstance) AddClientCredentials(tc *client.TeleportClient, cfg ClientConfig) (*client.TeleportClient, error) {
 	// Generate certificates for the user simulating login.
 	creds, err := GenerateUserCreds(UserCredsRequest{
 		Process:  i.Process,

integration/proxy/proxy_test.go

@@ -29,6 +29,7 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/gravitational/trace"
+	"github.com/jonboulle/clockwork"
 	"github.com/stretchr/testify/require"
 	"go.mongodb.org/mongo-driver/bson"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -41,6 +42,7 @@ import (
 	"github.com/gravitational/teleport/integration/kube"
 	"github.com/gravitational/teleport/lib"
 	"github.com/gravitational/teleport/lib/auth/testauthority"
+	libclient "github.com/gravitational/teleport/lib/client"
 	"github.com/gravitational/teleport/lib/defaults"
 	"github.com/gravitational/teleport/lib/service"
 	"github.com/gravitational/teleport/lib/srv/alpnproxy"
@@ -754,6 +756,74 @@ func TestALPNSNIProxyDatabaseAccess(t *testing.T) {
 			require.NoError(t, client.Close())
 		})
 	})
+
+	t.Run("authenticated tunnel with cert renewal", func(t *testing.T) {
+		// get a teleport client
+		tc, err := pack.Root.Cluster.NewClient(helpers.ClientConfig{
+			Login:   pack.Root.User.GetName(),
+			Cluster: pack.Root.Cluster.Secrets.SiteName,
+		})
+		require.NoError(t, err)
+		routeToDatabase := tlsca.RouteToDatabase{
+			ServiceName: pack.Root.MysqlService.Name,
+			Protocol:    pack.Root.MysqlService.Protocol,
+			Username:    "root",
+		}
+		// inject a fake clock into the middleware so we can control when it thinks certs have expired
+		fakeClock := clockwork.NewFakeClockAt(time.Now())
+		m, err := libclient.NewDBCertChecker(tc, routeToDatabase, fakeClock)
+		require.NoError(t, err)
+
+		// configure local proxy without certs but with cert checking/reissuing middleware
+		// local proxy middleware should fetch a DB cert when the local proxy starts
+		lp := mustStartALPNLocalProxyWithConfig(t, alpnproxy.LocalProxyConfig{
+			RemoteProxyAddr:    pack.Root.Cluster.SSHProxy,
+			Protocols:          []alpncommon.Protocol{alpncommon.ProtocolMySQL},
+			InsecureSkipVerify: true,
+			Middleware:         m,
+		})
+
+		client, err := mysql.MakeTestClientWithoutTLS(lp.GetAddr(), routeToDatabase)
+		require.NoError(t, err)
+
+		// Execute a query.
+		result, err := client.Execute("select 1")
+		require.NoError(t, err)
+		require.Equal(t, mysql.TestQueryResponse, result)
+
+		// Disconnect.
+		require.NoError(t, client.Close())
+		certs := lp.GetCerts()
+		require.NotEmpty(t, certs)
+		cert1, err := utils.TLSCertToX509(certs[0])
+		require.NoError(t, err)
+		// sanity check that cert equality check works
+		require.Equal(t, cert1, cert1, "cert should be equal to itself")
+
+		// mock db cert expiration (as far as the middleware thinks anyway)
+		// Unfortunately, mocking cert expiration by advancing a fake clock
+		// does not cause an invalid certificate error even if no cert renewal is done by the middleware,
+		// because TLS handshakes are done with real system time.
+		require.Greater(t, cert1.NotAfter, fakeClock.Now())
+		fakeClock.Advance(cert1.NotAfter.Sub(fakeClock.Now()) + time.Second)
+
+		// Open a new connection
+		client, err = mysql.MakeTestClientWithoutTLS(lp.GetAddr(), routeToDatabase)
+		require.NoError(t, err)
+
+		// Execute a query.
+		result, err = client.Execute("select 1")
+		require.NoError(t, err)
+		require.Equal(t, mysql.TestQueryResponse, result)
+
+		// Disconnect.
+		require.NoError(t, client.Close())
+		certs = lp.GetCerts()
+		require.NotEmpty(t, certs)
+		cert2, err := utils.TLSCertToX509(certs[0])
+		require.NoError(t, err)
+		require.NotEqual(t, cert1, cert2, "cert should have been renewed by middleware")
+	})
 }
 
 // TestALPNSNIProxyAppAccess tests application access via ALPN SNI proxy service.

lib/client/api.go

@@ -1713,7 +1713,7 @@ func (tc *TeleportClient) ReissueUserCerts(ctx context.Context, cachePolicy Cert
 // (according to RBAC), IssueCertsWithMFA will:
 // - for SSH certs, return the existing Key from the keystore.
 // - for TLS certs, fall back to ReissueUserCerts.
-func (tc *TeleportClient) IssueUserCertsWithMFA(ctx context.Context, params ReissueParams) (*Key, error) {
+func (tc *TeleportClient) IssueUserCertsWithMFA(ctx context.Context, params ReissueParams, applyOpts func(opts *PromptMFAChallengeOpts)) (*Key, error) {
 	ctx, span := tc.Tracer.Start(
 		ctx,
 		"teleportClient/IssueUserCertsWithMFA",
@@ -1730,7 +1730,7 @@ func (tc *TeleportClient) IssueUserCertsWithMFA(ctx context.Context, params Reis
 	return proxyClient.IssueUserCertsWithMFA(
 		ctx, params,
 		func(ctx context.Context, proxyAddr string, c *proto.MFAAuthenticateChallenge) (*proto.MFAAuthenticateResponse, error) {
-			return tc.PromptMFAChallenge(ctx, proxyAddr, c, nil /* applyOpts */)
+			return tc.PromptMFAChallenge(ctx, proxyAddr, c, applyOpts)
 		})
 }
 

lib/client/api_login_test.go

@@ -264,6 +264,7 @@ func TestTeleportClient_PromptMFAChallenge(t *testing.T) {
 	challenge := &proto.MFAAuthenticateChallenge{}
 
 	customizedOpts := &client.PromptMFAChallengeOpts{
+		BeforePrompt:            "some explanation for the imminent prompt",
 		PromptDevicePrefix:      "llama",
 		Quiet:                   true,
 		AllowStdinHijack:        true,

lib/client/local_proxy_middleware.go

@@ -0,0 +1,164 @@
+/*
+Copyright 2022 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package client
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/gravitational/trace"
+	"github.com/jonboulle/clockwork"
+
+	"github.com/gravitational/teleport/api/client/proto"
+	"github.com/gravitational/teleport/api/utils/keys"
+	"github.com/gravitational/teleport/lib/srv/alpnproxy"
+	"github.com/gravitational/teleport/lib/tlsca"
+	"github.com/gravitational/teleport/lib/utils"
+)
+
+// DBCertChecker is a middleware that ensures that the local proxy has valid TLS database certs.
+type DBCertChecker struct {
+	// tc is a TeleportClient used to reissue certificates when necessary.
+	tc *TeleportClient
+	// dbRoute contains database routing information.
+	dbRoute tlsca.RouteToDatabase
+	// Clock specifies the time provider. Will be used to override the time anchor
+	// for TLS certificate verification.
+	// Defaults to real clock if unspecified
+	clock clockwork.Clock
+}
+
+func NewDBCertChecker(tc *TeleportClient, dbRoute tlsca.RouteToDatabase, clock clockwork.Clock) (alpnproxy.LocalProxyMiddleware, error) {
+	if err := dbRoute.CheckAndSetDefaults(); err != nil {
+		return nil, trace.Wrap(err)
+	}
+	if clock == nil {
+		clock = clockwork.NewRealClock()
+	}
+	return &DBCertChecker{
+		tc:      tc,
+		dbRoute: dbRoute,
+		clock:   clock,
+	}, nil
+}
+
+var _ alpnproxy.LocalProxyMiddleware = (*DBCertChecker)(nil)
+
+// OnNewConnection is a callback triggered when a new downstream connection is
+// accepted by the local proxy.
+func (c *DBCertChecker) OnNewConnection(ctx context.Context, lp *alpnproxy.LocalProxy, conn net.Conn) error {
+	return trace.Wrap(c.ensureValidCerts(ctx, lp))
+}
+
+// OnStart is a callback triggered when the local proxy starts.
+func (c *DBCertChecker) OnStart(ctx context.Context, lp *alpnproxy.LocalProxy) error {
+	return trace.Wrap(c.ensureValidCerts(ctx, lp))
+}
+
+// checkCerts checks if the local proxy TLS certs are configured, not expired, and match the db route.
+func (c *DBCertChecker) checkCerts(lp *alpnproxy.LocalProxy) error {
+	log.Debug("checking local proxy database certs")
+	certs := lp.GetCerts()
+	if len(certs) == 0 {
+		return trace.Wrap(trace.NotFound("local proxy has no TLS certificates configured"))
+	}
+	cert, err := utils.TLSCertToX509(certs[0])
+	if err != nil {
+		return trace.Wrap(err)
+	}
+	err = utils.VerifyCertificateExpiry(cert, c.clock)
+	if err != nil {
+		return trace.Wrap(err)
+	}
+	identity, err := tlsca.FromSubject(cert.Subject, cert.NotAfter)
+	if err != nil {
+		return trace.Wrap(err)
+	}
+	if c.dbRoute.Username != "" && c.dbRoute.Username != identity.RouteToDatabase.Username {
+		msg := fmt.Sprintf("certificate subject is for user %s, but need %s", identity.RouteToDatabase.Username, c.dbRoute.Username)
+		return trace.Wrap(errors.New(msg))
+	}
+	if c.dbRoute.Database != "" && c.dbRoute.Database != identity.RouteToDatabase.Database {
+		msg := fmt.Sprintf("certificate subject is for database name %s, but need %s", identity.RouteToDatabase.Database, c.dbRoute.Database)
+		return trace.Wrap(errors.New(msg))
+	}
+	return nil
+}
+
+// ensureValidCerts ensures that the local proxy is configured with valid certs.
+func (c *DBCertChecker) ensureValidCerts(ctx context.Context, lp *alpnproxy.LocalProxy) error {
+	if err := c.checkCerts(lp); err != nil {
+		log.WithError(err).Debug("need cert renewal")
+	} else {
+		return nil
+	}
+	return trace.Wrap(c.renewCerts(ctx, lp))
+}
+
+// renewCerts attempts to renew the database certs for the local proxy.
+func (c *DBCertChecker) renewCerts(ctx context.Context, lp *alpnproxy.LocalProxy) error {
+	var accessRequests []string
+	if profile, err := StatusCurrent(c.tc.HomePath, c.tc.WebProxyAddr, ""); err != nil {
+		log.WithError(err).Warn("unable to load profile, requesting database certs without access requests")
+	} else {
+		accessRequests = profile.ActiveRequests.AccessRequests
+	}
+
+	msg := fmt.Sprintf("Local proxy tunnel requires credentials to access database %q", c.dbRoute.ServiceName)
+	var key *Key
+	if err := RetryWithRelogin(ctx, c.tc, func() error {
+		newKey, err := c.tc.IssueUserCertsWithMFA(ctx, ReissueParams{
+			RouteToCluster: c.tc.SiteName,
+			RouteToDatabase: proto.RouteToDatabase{
+				ServiceName: c.dbRoute.ServiceName,
+				Protocol:    c.dbRoute.Protocol,
+				Username:    c.dbRoute.Username,
+				Database:    c.dbRoute.Database,
+			},
+			AccessRequests: accessRequests,
+		}, func(opts *PromptMFAChallengeOpts) {
+			opts.BeforePrompt = msg
+		})
+		key = newKey
+		return trace.Wrap(err)
+	}); err != nil {
+		return trace.Wrap(err)
+	}
+
+	dbCert, ok := key.DBTLSCerts[c.dbRoute.ServiceName]
+	if !ok {
+		return trace.NotFound("database '%v' TLS cert missing", c.dbRoute.ServiceName)
+	}
+	tlsCert, err := keys.X509KeyPair(dbCert, key.PrivateKeyPEM())
+	if err != nil {
+		return trace.Wrap(err)
+	}
+	x509cert, err := x509.ParseCertificate(tlsCert.Certificate[0])
+	if err != nil {
+		return trace.Wrap(err)
+	}
+	certTTL := x509cert.NotAfter.Sub(c.clock.Now()).Round(time.Minute)
+	fmt.Printf("Proxy credentials renewed. New cert valid until %s [valid for %v]\n",
+		x509cert.NotAfter.Format(time.RFC3339), certTTL)
+	lp.SetCerts([]tls.Certificate{tlsCert})
+	return nil
+}

lib/client/mfa.go

@@ -50,6 +50,10 @@ func (p *mfaPrompt) PromptPIN() (string, error) {
 
 // PromptMFAChallengeOpts groups optional settings for PromptMFAChallenge.
 type PromptMFAChallengeOpts struct {
+	// BeforePrompt is an optional method to print before the prompt.
+	// It is used to provide context about why the user is being prompted where it may
+	// not be obvious.
+	BeforePrompt string
 	// PromptDevicePrefix is an optional prefix printed before "security key" or
 	// "device". It is used to emphasize between different kinds of devices, like
 	// registered vs new.
@@ -105,6 +109,10 @@ func PromptMFAChallenge(ctx context.Context, c *proto.MFAAuthenticateChallenge,
 	if opts == nil {
 		opts = &PromptMFAChallengeOpts{}
 	}
+	if opts.BeforePrompt != "" {
+		// print a message before any prompt or error message to provide context
+		fmt.Println(opts.BeforePrompt)
+	}
 	promptDevicePrefix := opts.PromptDevicePrefix
 	quiet := opts.Quiet