[v17] Add SSO MFA prompt for WebUI MFA flows

lib/client/weblogin.go

@@ -113,6 +113,8 @@ type MFAChallengeResponse struct {
 	WebauthnResponse *wantypes.CredentialAssertionResponse `json:"webauthn_response,omitempty"`
 	// SSOResponse is a response from an SSO MFA flow.
 	SSOResponse *SSOResponse `json:"sso_response"`
+	// TODO(Joerger): DELETE IN v19.0.0, WebauthnResponse used instead.
+	WebauthnAssertionResponse *wantypes.CredentialAssertionResponse `json:"webauthnAssertionResponse"`
 }
 
 // SSOResponse is a json compatible [proto.SSOResponse].
@@ -124,25 +126,57 @@ type SSOResponse struct {
 // GetOptionalMFAResponseProtoReq converts response to a type proto.MFAAuthenticateResponse,
 // if there were any responses set. Otherwise returns nil.
 func (r *MFAChallengeResponse) GetOptionalMFAResponseProtoReq() (*proto.MFAAuthenticateResponse, error) {
-	if r.TOTPCode != "" && r.WebauthnResponse != nil {
+	var availableResponses int
+	if r.TOTPCode != "" {
+		availableResponses++
+	}
+	if r.WebauthnResponse != nil {
+		availableResponses++
+	}
+	if r.SSOResponse != nil {
+		availableResponses++
+	}
+
+	if availableResponses > 1 {
 		return nil, trace.BadParameter("only one MFA response field can be set")
 	}
 
-	if r.TOTPCode != "" {
+	switch {
+	case r.WebauthnResponse != nil:
+		return &proto.MFAAuthenticateResponse{Response: &proto.MFAAuthenticateResponse_Webauthn{
+			Webauthn: wantypes.CredentialAssertionResponseToProto(r.WebauthnResponse),
+		}}, nil
+	case r.SSOResponse != nil:
+		return &proto.MFAAuthenticateResponse{Response: &proto.MFAAuthenticateResponse_SSO{
+			SSO: &proto.SSOResponse{
+				RequestId: r.SSOResponse.RequestID,
+				Token:     r.SSOResponse.Token,
+			},
+		}}, nil
+	case r.TOTPCode != "":
 		return &proto.MFAAuthenticateResponse{Response: &proto.MFAAuthenticateResponse_TOTP{
 			TOTP: &proto.TOTPResponse{Code: r.TOTPCode},
 		}}, nil
-	}
-
-	if r.WebauthnResponse != nil {
+	case r.WebauthnAssertionResponse != nil:
 		return &proto.MFAAuthenticateResponse{Response: &proto.MFAAuthenticateResponse_Webauthn{
-			Webauthn: wantypes.CredentialAssertionResponseToProto(r.WebauthnResponse),
+			Webauthn: wantypes.CredentialAssertionResponseToProto(r.WebauthnAssertionResponse),
 		}}, nil
 	}
 
 	return nil, nil
 }
 
+// ParseMFAChallengeResponse parses [MFAChallengeResponse] from JSON and returns it as a [proto.MFAAuthenticateResponse].
+func ParseMFAChallengeResponse(mfaResponseJSON []byte) (*proto.MFAAuthenticateResponse, error) {
+	var resp MFAChallengeResponse
+	if err := json.Unmarshal(mfaResponseJSON, &resp); err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	protoResp, err := resp.GetOptionalMFAResponseProtoReq()
+	return protoResp, trace.Wrap(err)
+}
+
 // CreateSSHCertReq is passed by tsh to authenticate a local user without MFA
 // and receive short-lived certificates.
 type CreateSSHCertReq struct {

lib/web/apiserver.go

@@ -2778,7 +2778,7 @@ func (h *Handler) mfaLoginBegin(w http.ResponseWriter, r *http.Request, p httpro
 		return nil, trace.AccessDenied("invalid credentials")
 	}
 
-	return makeAuthenticateChallenge(mfaChallenge), nil
+	return makeAuthenticateChallenge(mfaChallenge, "" /*channelID*/), nil
 }
 
 // mfaLoginFinish completes the MFA login ceremony, returning a new SSH
@@ -4877,16 +4877,12 @@ func parseMFAResponseFromRequest(r *http.Request) error {
 // context and returned.
 func contextWithMFAResponseFromRequestHeader(ctx context.Context, requestHeader http.Header) (context.Context, error) {
 	if mfaResponseJSON := requestHeader.Get("Teleport-MFA-Response"); mfaResponseJSON != "" {
-		var resp mfaResponse
-		if err := json.Unmarshal([]byte(mfaResponseJSON), &resp); err != nil {
+		mfaResp, err := client.ParseMFAChallengeResponse([]byte(mfaResponseJSON))
+		if err != nil {
 			return nil, trace.Wrap(err)
 		}
 
-		return mfa.ContextWithMFAResponse(ctx, &proto.MFAAuthenticateResponse{
-			Response: &proto.MFAAuthenticateResponse_Webauthn{
-				Webauthn: wantypes.CredentialAssertionResponseToProto(resp.WebauthnAssertionResponse),
-			},
-		}), nil
+		return mfa.ContextWithMFAResponse(ctx, mfaResp), nil
 	}
 
 	return ctx, nil

lib/web/apiserver_test.go

@@ -5594,10 +5594,6 @@ func TestCreateAppSession_RequireSessionMFA(t *testing.T) {
 	require.NoError(t, err)
 	mfaResp, err := webauthnDev.SolveAuthn(chal)
 	require.NoError(t, err)
-	mfaRespJSON, err := json.Marshal(mfaResponse{
-		WebauthnAssertionResponse: wantypes.CredentialAssertionResponseFromProto(mfaResp.GetWebauthn()),
-	})
-	require.NoError(t, err)
 
 	// Extract the session ID and bearer token for the current session.
 	rawCookie := *pack.cookies[0]
@@ -5631,7 +5627,9 @@ func TestCreateAppSession_RequireSessionMFA(t *testing.T) {
 					PublicAddr:  "panel.example.com",
 					ClusterName: "localhost",
 				},
-				MFAResponse: string(mfaRespJSON),
+				MFAResponse: client.MFAChallengeResponse{
+					WebauthnAssertionResponse: wantypes.CredentialAssertionResponseFromProto(mfaResp.GetWebauthn()),
+				},
 			},
 			expectMFAVerified: true,
 		},

lib/web/apps.go

@@ -22,7 +22,6 @@ package web
 
 import (
 	"context"
-	"encoding/json"
 	"net/http"
 	"sort"
 
@@ -33,7 +32,7 @@ import (
 	"github.com/gravitational/teleport/api/client/proto"
 	apidefaults "github.com/gravitational/teleport/api/defaults"
 	"github.com/gravitational/teleport/api/types"
-	wantypes "github.com/gravitational/teleport/lib/auth/webauthntypes"
+	"github.com/gravitational/teleport/lib/client"
 	"github.com/gravitational/teleport/lib/httplib"
 	"github.com/gravitational/teleport/lib/reversetunnelclient"
 	"github.com/gravitational/teleport/lib/utils"
@@ -191,7 +190,10 @@ type CreateAppSessionRequest struct {
 	// AWSRole is the AWS role ARN when accessing AWS management console.
 	AWSRole string `json:"arn,omitempty"`
 	// MFAResponse is an optional MFA response used to create an MFA verified app session.
-	MFAResponse string `json:"mfa_response"`
+	MFAResponse client.MFAChallengeResponse `json:"mfaResponse"`
+	// TODO(Joerger): DELETE IN v19.0.0
+	// Backwards compatible version of MFAResponse
+	MFAResponseJSON string `json:"mfa_response"`
 }
 
 // CreateAppSessionResponse is a response to POST /v1/webapi/sessions/app
@@ -230,17 +232,16 @@ func (h *Handler) createAppSession(w http.ResponseWriter, r *http.Request, p htt
 		}
 	}
 
-	var mfaProtoResponse *proto.MFAAuthenticateResponse
-	if req.MFAResponse != "" {
-		var resp mfaResponse
-		if err := json.Unmarshal([]byte(req.MFAResponse), &resp); err != nil {
-			return nil, trace.Wrap(err)
-		}
+	mfaResponse, err := req.MFAResponse.GetOptionalMFAResponseProtoReq()
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
 
-		mfaProtoResponse = &proto.MFAAuthenticateResponse{
-			Response: &proto.MFAAuthenticateResponse_Webauthn{
-				Webauthn: wantypes.CredentialAssertionResponseToProto(resp.WebauthnAssertionResponse),
-			},
+	// Fallback to backwards compatible mfa response.
+	if mfaResponse == nil && req.MFAResponseJSON != "" {
+		mfaResponse, err = client.ParseMFAChallengeResponse([]byte(req.MFAResponseJSON))
+		if err != nil {
+			return nil, trace.Wrap(err)
 		}
 	}
 
@@ -263,7 +264,7 @@ func (h *Handler) createAppSession(w http.ResponseWriter, r *http.Request, p htt
 		PublicAddr:  result.App.GetPublicAddr(),
 		ClusterName: result.ClusterName,
 		AWSRoleARN:  req.AWSRole,
-		MFAResponse: mfaProtoResponse,
+		MFAResponse: mfaResponse,
 		AppName:     result.App.GetName(),
 		URI:         result.App.GetURI(),
 		ClientAddr:  r.RemoteAddr,

lib/web/files.go

@@ -20,7 +20,6 @@ package web
 
 import (
 	"context"
-	"encoding/json"
 	"errors"
 	"net/http"
 	"time"
@@ -35,7 +34,6 @@ import (
 	"github.com/gravitational/teleport/api/utils/keys"
 	"github.com/gravitational/teleport/api/utils/sshutils"
 	"github.com/gravitational/teleport/lib/auth/authclient"
-	wantypes "github.com/gravitational/teleport/lib/auth/webauthntypes"
 	"github.com/gravitational/teleport/lib/client"
 	"github.com/gravitational/teleport/lib/multiplexer"
 	"github.com/gravitational/teleport/lib/reversetunnelclient"
@@ -56,8 +54,8 @@ type fileTransferRequest struct {
 	remoteLocation string
 	// filename is a file name
 	filename string
-	// webauthn is an optional parameter that contains a webauthn response string used to issue single use certs
-	webauthn string
+	// mfaResponse is an optional parameter that contains an mfa response string used to issue single use certs
+	mfaResponse string
 	// fileTransferRequestID is used to find a FileTransferRequest on a session
 	fileTransferRequestID string
 	// moderatedSessonID is an ID of a moderated session that has completed a
@@ -74,11 +72,25 @@ func (h *Handler) transferFile(w http.ResponseWriter, r *http.Request, p httprou
 		remoteLocation:        query.Get("location"),
 		filename:              query.Get("filename"),
 		namespace:             defaults.Namespace,
-		webauthn:              query.Get("webauthn"),
+		mfaResponse:           query.Get("mfaResponse"),
 		fileTransferRequestID: query.Get("fileTransferRequestId"),
 		moderatedSessionID:    query.Get("moderatedSessionId"),
 	}
 
+	// Check for old query parameter, uses the same data structure.
+	// TODO(Joerger): DELETE IN v19.0.0
+	if req.mfaResponse == "" {
+		req.mfaResponse = query.Get("webauthn")
+	}
+
+	var mfaResponse *proto.MFAAuthenticateResponse
+	if req.mfaResponse != "" {
+		var err error
+		if mfaResponse, err = client.ParseMFAChallengeResponse([]byte(req.mfaResponse)); err != nil {
+			return nil, trace.Wrap(err)
+		}
+	}
+
 	// Send an error if only one of these params has been sent. Both should exist or not exist together
 	if (req.fileTransferRequestID != "") != (req.moderatedSessionID != "") {
 		return nil, trace.BadParameter("fileTransferRequestId and moderatedSessionId must both be included in the same request.")
@@ -107,7 +119,7 @@ func (h *Handler) transferFile(w http.ResponseWriter, r *http.Request, p httprou
 		return nil, trace.Wrap(err)
 	}
 
-	if mfaReq.Required && query.Get("webauthn") == "" {
+	if mfaReq.Required && mfaResponse == nil {
 		return nil, trace.AccessDenied("MFA required for file transfer")
 	}
 
@@ -135,8 +147,8 @@ func (h *Handler) transferFile(w http.ResponseWriter, r *http.Request, p httprou
 		return nil, trace.Wrap(err)
 	}
 
-	if req.webauthn != "" {
-		err = ft.issueSingleUseCert(req.webauthn, r, tc)
+	if req.mfaResponse != "" {
+		err = ft.issueSingleUseCert(mfaResponse, r, tc)
 		if err != nil {
 			return nil, trace.Wrap(err)
 		}
@@ -216,21 +228,10 @@ func (f *fileTransfer) createClient(req fileTransferRequest, httpReq *http.Reque
 	return tc, nil
 }
 
-type mfaResponse struct {
-	// WebauthnResponse is the response from authenticators.
-	WebauthnAssertionResponse *wantypes.CredentialAssertionResponse `json:"webauthnAssertionResponse"`
-}
-
 // issueSingleUseCert will take an assertion response sent from a solved challenge in the web UI
 // and use that to generate a cert. This cert is added to the Teleport Client as an authmethod that
 // can be used to connect to a node.
-func (f *fileTransfer) issueSingleUseCert(webauthn string, httpReq *http.Request, tc *client.TeleportClient) error {
-	var mfaResp mfaResponse
-	err := json.Unmarshal([]byte(webauthn), &mfaResp)
-	if err != nil {
-		return trace.Wrap(err)
-	}
-
+func (f *fileTransfer) issueSingleUseCert(mfaResponse *proto.MFAAuthenticateResponse, httpReq *http.Request, tc *client.TeleportClient) error {
 	pk, err := keys.ParsePrivateKey(f.sctx.cfg.Session.GetSSHPriv())
 	if err != nil {
 		return trace.Wrap(err)
@@ -241,11 +242,7 @@ func (f *fileTransfer) issueSingleUseCert(webauthn string, httpReq *http.Request
 		SSHPublicKey: pk.MarshalSSHPublicKey(),
 		Username:     f.sctx.GetUser(),
 		Expires:      time.Now().Add(time.Minute).UTC(),
-		MFAResponse: &proto.MFAAuthenticateResponse{
-			Response: &proto.MFAAuthenticateResponse_Webauthn{
-				Webauthn: wantypes.CredentialAssertionResponseToProto(mfaResp.WebauthnAssertionResponse),
-			},
-		},
+		MFAResponse:  mfaResponse,
 	})
 	if err != nil {
 		return trace.Wrap(err)

lib/web/mfa.go

@@ -21,8 +21,10 @@ package web
 import (
 	"context"
 	"net/http"
+	"net/url"
 	"strings"
 
+	"github.com/google/uuid"
 	"github.com/gravitational/trace"
 	"github.com/julienschmidt/httprouter"
 
@@ -201,6 +203,22 @@ func (h *Handler) createAuthenticateChallengeHandle(w http.ResponseWriter, r *ht
 		allowReuse = mfav1.ChallengeAllowReuse_CHALLENGE_ALLOW_REUSE_YES
 	}
 
+	// Prepare an sso client redirect URL in case the user has an SSO MFA device.
+	ssoClientRedirectURL, err := url.Parse(sso.WebMFARedirect)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	// id is used by the front end to differentiate between separate ongoing SSO challenges.
+	id, err := uuid.NewRandom()
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	channelID := id.String()
+	query := ssoClientRedirectURL.Query()
+	query.Set("channel_id", channelID)
+	ssoClientRedirectURL.RawQuery = query.Encode()
+
 	chal, err := clt.CreateAuthenticateChallenge(r.Context(), &proto.CreateAuthenticateChallengeRequest{
 		Request: &proto.CreateAuthenticateChallengeRequest_ContextUser{
 			ContextUser: &proto.ContextUser{},
@@ -211,13 +229,13 @@ func (h *Handler) createAuthenticateChallengeHandle(w http.ResponseWriter, r *ht
 			AllowReuse:                  allowReuse,
 			UserVerificationRequirement: req.UserVerificationRequirement,
 		},
-		SSOClientRedirectURL: sso.WebMFARedirect,
+		SSOClientRedirectURL: ssoClientRedirectURL.String(),
 	})
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}
 
-	return makeAuthenticateChallenge(chal), nil
+	return makeAuthenticateChallenge(chal, channelID), nil
 }
 
 // createAuthenticateChallengeWithTokenHandle creates and returns MFA authenticate challenges for the user defined in token.
@@ -235,7 +253,7 @@ func (h *Handler) createAuthenticateChallengeWithTokenHandle(w http.ResponseWrit
 		return nil, trace.Wrap(err)
 	}
 
-	return makeAuthenticateChallenge(chal), nil
+	return makeAuthenticateChallenge(chal, "" /*channelID*/), nil
 }
 
 type createRegisterChallengeWithTokenRequest struct {
@@ -581,7 +599,7 @@ func (h *Handler) checkMFARequired(ctx context.Context, req *isMFARequiredReques
 }
 
 // makeAuthenticateChallenge converts proto to JSON format.
-func makeAuthenticateChallenge(protoChal *proto.MFAAuthenticateChallenge) *client.MFAAuthenticateChallenge {
+func makeAuthenticateChallenge(protoChal *proto.MFAAuthenticateChallenge, ssoChannelID string) *client.MFAAuthenticateChallenge {
 	chal := &client.MFAAuthenticateChallenge{
 		TOTPChallenge: protoChal.GetTOTP() != nil,
 	}
@@ -590,6 +608,7 @@ func makeAuthenticateChallenge(protoChal *proto.MFAAuthenticateChallenge) *clien
 	}
 	if protoChal.GetSSOChallenge() != nil {
 		chal.SSOChallenge = client.SSOChallengeFromProto(protoChal.GetSSOChallenge())
+		chal.SSOChallenge.ChannelID = ssoChannelID
 	}
 	return chal
 }