AUTH-2055: Verifies token at edge on access login

carrier/carrier.go

@@ -114,7 +114,7 @@ func createWebsocketStream(options *StartOptions) (*cloudflaredWebsocket.Conn, e
 
 	wsConn, resp, err := cloudflaredWebsocket.ClientConnect(req, nil)
 	defer closeRespBody(resp)
-	if err != nil && isAccessResponse(resp) {
+	if err != nil && IsAccessResponse(resp) {
 		wsConn, err = createAccessAuthenticatedStream(options)
 		if err != nil {
 			return nil, err
@@ -126,10 +126,10 @@ func createWebsocketStream(options *StartOptions) (*cloudflaredWebsocket.Conn, e
 	return &cloudflaredWebsocket.Conn{Conn: wsConn}, nil
 }
 
-// isAccessResponse checks the http Response to see if the url location
+// IsAccessResponse checks the http Response to see if the url location
 // contains the Access structure.
-func isAccessResponse(resp *http.Response) bool {
-	if resp == nil || resp.StatusCode <= 300 {
+func IsAccessResponse(resp *http.Response) bool {
+	if resp == nil || resp.StatusCode != http.StatusFound {
 		return false
 	}
 
@@ -156,7 +156,7 @@ func createAccessAuthenticatedStream(options *StartOptions) (*websocket.Conn, er
 		return wsConn, nil
 	}
 
-	if !isAccessResponse(resp) {
+	if !IsAccessResponse(resp) {
 		return nil, err
 	}
 
@@ -179,7 +179,7 @@ func createAccessAuthenticatedStream(options *StartOptions) (*websocket.Conn, er
 
 // createAccessWebSocketStream builds an Access request and makes a connection
 func createAccessWebSocketStream(options *StartOptions) (*websocket.Conn, *http.Response, error) {
-	req, err := buildAccessRequest(options)
+	req, err := BuildAccessRequest(options)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -187,7 +187,7 @@ func createAccessWebSocketStream(options *StartOptions) (*websocket.Conn, *http.
 }
 
 // buildAccessRequest builds an HTTP request with the Access token set
-func buildAccessRequest(options *StartOptions) (*http.Request, error) {
+func BuildAccessRequest(options *StartOptions) (*http.Request, error) {
 	req, err := http.NewRequest(http.MethodGet, options.OriginURL, nil)
 	if err != nil {
 		return nil, err

carrier/carrier_test.go

@@ -102,14 +102,14 @@ func TestIsAccessResponse(t *testing.T) {
 		ExpectedOut bool
 	}{
 		{"nil response", nil, false},
-		{"redirect with no location", &http.Response{StatusCode: http.StatusPermanentRedirect}, false},
+		{"redirect with no location", &http.Response{StatusCode: http.StatusFound}, false},
 		{"200 ok", &http.Response{StatusCode: http.StatusOK}, false},
-		{"redirect with location", &http.Response{StatusCode: http.StatusPermanentRedirect, Header: validLocationHeader}, true},
-		{"redirect with invalid location", &http.Response{StatusCode: http.StatusPermanentRedirect, Header: invalidLocationHeader}, false},
+		{"redirect with location", &http.Response{StatusCode: http.StatusFound, Header: validLocationHeader}, true},
+		{"redirect with invalid location", &http.Response{StatusCode: http.StatusFound, Header: invalidLocationHeader}, false},
 	}
 
 	for i, tc := range testCases {
-		if isAccessResponse(tc.In) != tc.ExpectedOut {
+		if IsAccessResponse(tc.In) != tc.ExpectedOut {
 			t.Fatalf("Failed case %d -- %s", i, tc.Description)
 		}
 	}

cmd/cloudflared/access/cmd.go

@@ -1,17 +1,20 @@
 package access
 
 import (
-	"errors"
 	"fmt"
+	"net/http"
 	"net/url"
 	"os"
 	"strings"
 	"text/template"
+	"time"
 
+	"github.com/cloudflare/cloudflared/carrier"
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/shell"
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/token"
 	"github.com/cloudflare/cloudflared/sshgen"
 	"github.com/cloudflare/cloudflared/validation"
+	"github.com/pkg/errors"
 	"golang.org/x/net/idna"
 
 	"github.com/cloudflare/cloudflared/log"
@@ -188,9 +191,14 @@ func login(c *cli.Context) error {
 		logger.Errorf("Please provide the url of the Access application\n")
 		return err
 	}
-	token, err := token.FetchToken(appURL)
-	if err != nil {
-		logger.Errorf("Failed to fetch token: %s\n", err)
+	if err := verifyTokenAtEdge(appURL, c); err != nil {
+		logger.WithError(err).Error("Could not verify token")
+		return err
+	}
+
+	token, err := token.GetTokenIfExists(appURL)
+	if err != nil || token == "" {
+		fmt.Fprintln(os.Stderr, "Unable to find token for provided application.")
 		return err
 	}
 	fmt.Fprintf(os.Stdout, "Successfully fetched your token:\n\n%s\n\n", string(token))
@@ -372,3 +380,59 @@ func isFileThere(candidate string) bool {
 	}
 	return true
 }
+
+// verifyTokenAtEdge checks for a token on disk, or generates a new one.
+// Then makes a request to to the origin with the token to ensure it is valid.
+// Returns nil if token is valid.
+func verifyTokenAtEdge(appUrl *url.URL, c *cli.Context) error {
+	headers := buildRequestHeaders(c.StringSlice(sshHeaderFlag))
+	if c.IsSet(sshTokenIDFlag) {
+		headers.Add("CF-Access-Client-Id", c.String(sshTokenIDFlag))
+	}
+	if c.IsSet(sshTokenSecretFlag) {
+		headers.Add("CF-Access-Client-Secret", c.String(sshTokenSecretFlag))
+	}
+	options := &carrier.StartOptions{OriginURL: appUrl.String(), Headers: headers}
+
+	if valid, err := isTokenValid(options); err != nil {
+		return err
+	} else if valid {
+		return nil
+	}
+
+	if err := token.RemoveTokenIfExists(appUrl); err != nil {
+		return err
+	}
+
+	if valid, err := isTokenValid(options); err != nil {
+		return err
+	} else if !valid {
+		return errors.New("failed to verify token")
+	}
+
+	return nil
+}
+
+// isTokenValid makes a request to the origin and returns true if the response was not a 302.
+func isTokenValid(options *carrier.StartOptions) (bool, error) {
+	req, err := carrier.BuildAccessRequest(options)
+	if err != nil {
+		return false, errors.Wrap(err, "Could not create access request")
+	}
+
+	// Do not follow redirects
+	client := &http.Client{
+		CheckRedirect: func(req *http.Request, via []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
+		Timeout: time.Second * 5,
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	// A redirect to login means the token was invalid.
+	return !carrier.IsAccessResponse(resp), nil
+}