server, integration, cmd: Protect Admin API

Admin API now requires a 128 byte base64 encoded secret to be passed in
Authorization header, closing up a potential security hole for those
who expose this service.

cmd/dex-overlord/main.go

@@ -41,6 +41,9 @@ func main() {
 
 	adminListen := fs.String("admin-listen", "http://127.0.0.1:5557", "scheme, host and port for listening for administrative operation requests ")
 
+	adminAPISecret := pflag.NewBase64(server.AdminAPISecretLength)
+	fs.Var(adminAPISecret, "admin-api-secret", fmt.Sprintf("A base64-encoded %d byte string which is used to protect the Admin API.", server.AdminAPISecretLength))
+
 	localConnectorID := fs.String("local-connector", "local", "ID of the local connector")
 	logDebug := fs.Bool("log-debug", false, "log debug-level information")
 	logTimestamps := fs.Bool("log-timestamps", false, "prefix log lines with timestamps")
@@ -124,7 +127,7 @@ func main() {
 	}
 
 	krot := key.NewPrivateKeyRotator(kRepo, *keyPeriod)
-	s := server.NewAdminServer(adminAPI, krot)
+	s := server.NewAdminServer(adminAPI, krot, adminAPISecret.String())
 	h := s.HTTPHandler()
 	httpsrv := &http.Server{
 		Addr:    adminURL.Host,

integration/admin_api_test.go

@@ -14,6 +14,10 @@ import (
 	"github.com/coreos/dex/user"
 )
 
+const (
+	adminAPITestSecret = "admin_secret"
+)
+
 type adminAPITestFixtures struct {
 	ur       user.UserRepo
 	pwr      user.PasswordInfoRepo
@@ -58,6 +62,15 @@ var (
 	}
 )
 
+type adminAPITransport struct {
+	secret string
+}
+
+func (a *adminAPITransport) RoundTrip(r *http.Request) (*http.Response, error) {
+	r.Header.Set("Authorization", a.secret)
+	return http.DefaultTransport.RoundTrip(r)
+}
+
 func makeAdminAPITestFixtures() *adminAPITestFixtures {
 	f := &adminAPITestFixtures{}
 
@@ -65,9 +78,13 @@ func makeAdminAPITestFixtures() *adminAPITestFixtures {
 	f.ur = ur
 	f.pwr = pwr
 	f.adAPI = admin.NewAdminAPI(um, f.ur, f.pwr, "local")
-	f.adSrv = server.NewAdminServer(f.adAPI, nil)
+	f.adSrv = server.NewAdminServer(f.adAPI, nil, adminAPITestSecret)
 	f.hSrv = httptest.NewServer(f.adSrv.HTTPHandler())
-	f.hc = &http.Client{}
+	f.hc = &http.Client{
+		Transport: &adminAPITransport{
+			secret: adminAPITestSecret,
+		},
+	}
 	f.adClient, _ = adminschema.NewWithBasePath(f.hc, f.hSrv.URL)
 
 	return f
@@ -129,6 +146,7 @@ func TestCreateAdmin(t *testing.T) {
 	tests := []struct {
 		admn    *adminschema.Admin
 		errCode int
+		secret  string
 	}{
 		{
 			admn: &adminschema.Admin{
@@ -137,6 +155,14 @@ func TestCreateAdmin(t *testing.T) {
 			},
 			errCode: -1,
 		},
+		{
+			admn: &adminschema.Admin{
+				Email:    "foo@example.com",
+				Password: "foopass",
+			},
+			errCode: http.StatusUnauthorized,
+			secret:  "bad_secret",
+		},
 		{
 			// duplicate Email
 			admn: &adminschema.Admin{
@@ -156,6 +182,11 @@ func TestCreateAdmin(t *testing.T) {
 	for i, tt := range tests {
 		func() {
 			f := makeAdminAPITestFixtures()
+			if tt.secret != "" {
+				f.hc.Transport = &adminAPITransport{
+					secret: tt.secret,
+				}
+			}
 			defer f.close()
 
 			admn, err := f.adClient.Admin.Create(tt.admn).Do()

server/admin.go

@@ -16,6 +16,7 @@ import (
 
 const (
 	AdminAPIVersion      = "v1"
+	AdminAPISecretLength = 128
 )
 
 var (
@@ -28,9 +29,10 @@ var (
 type AdminServer struct {
 	adminAPI *admin.AdminAPI
 	checker  health.Checker
+	secret   string
 }
 
-func NewAdminServer(adminAPI *admin.AdminAPI, rotator *key.PrivateKeyRotator) *AdminServer {
+func NewAdminServer(adminAPI *admin.AdminAPI, rotator *key.PrivateKeyRotator, secret string) *AdminServer {
 	return &AdminServer{
 		adminAPI: adminAPI,
 		checker: health.Checker{
@@ -38,6 +40,7 @@ func NewAdminServer(adminAPI *admin.AdminAPI, rotator *key.PrivateKeyRotator) *A
 				rotator,
 			},
 		},
+		secret: secret,
 	}
 }
 
@@ -48,7 +51,25 @@ func (s *AdminServer) HTTPHandler() http.Handler {
 	r.GET(AdminGetStateEndpoint, s.getState)
 	r.Handler("GET", httpPathHealth, s.checker)
 	r.HandlerFunc("GET", httpPathDebugVars, health.ExpvarHandler)
-	return r
+
+	return authorizer(r, s.secret, httpPathHealth, httpPathDebugVars)
+}
+
+func authorizer(h http.Handler, secret string, public ...string) http.Handler {
+	publicSet := map[string]struct{}{}
+	for _, p := range public {
+		publicSet[p] = struct{}{}
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, isPublicPath := publicSet[r.URL.Path]
+
+		if !isPublicPath && r.Header.Get("Authorization") != secret {
+			writeAPIError(w, http.StatusUnauthorized, newAPIError(errorAccessDenied, ""))
+			return
+		}
+		h.ServeHTTP(w, r)
+	})
 }
 
 func (s *AdminServer) getAdmin(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {