Merge pull request #10937 from reasonerjt/csrf-2.0

Update CSRF mechanism
2024-12-22 08:38:03 +01:00 · 2020-03-09 12:31:08 +08:00 · 2020-03-09 12:31:08 +08:00 · 6d89553c4d
commit 6d89553c4d
parent 073d95b89f ae5ffce83a
34 changed files with 2568 additions and 36 deletions
--- a/make/photon/prepare/templates/core/app.conf.jinja
+++ b/make/photon/prepare/templates/core/app.conf.jinja
@ -4,6 +4,3 @@ enablegzip = true

 [dev]
 httpport = 8080
-EnableXSRF = true
-XSRFKey = {{xsrf_key}}
-XSRFExpire = 3600
--- a/make/photon/prepare/templates/core/env.jinja
+++ b/make/photon/prepare/templates/core/env.jinja
@ -47,6 +47,7 @@ REGISTRY_CONTROLLER_URL={{registry_controller_url}}
 WITH_CHARTMUSEUM={{with_chartmuseum}}
 REGISTRY_CREDENTIAL_USERNAME={{registry_username}}
 REGISTRY_CREDENTIAL_PASSWORD={{registry_password}}
+CSRF_KEY={{csrf_key}}

 HTTP_PROXY={{core_http_proxy}}
 HTTPS_PROXY={{core_https_proxy}}
--- a/make/photon/prepare/utils/core.py
+++ b/make/photon/prepare/utils/core.py
@ -32,14 +32,14 @@ def prepare_core(config_dict, with_notary, with_clair, with_trivy, with_chartmus
        with_clair=with_clair,
        with_trivy=with_trivy,
        with_chartmuseum=with_chartmuseum,
+        csrf_key=generate_random_string(32),
        **config_dict)

    render_jinja(
        core_conf_template_path,
        core_conf,
        uid=DEFAULT_UID,
-        gid=DEFAULT_GID,
-        xsrf_key=generate_random_string(40))
+        gid=DEFAULT_GID)


 def copy_core_config(core_templates_path, core_config_path):
--- a/src/core/api/base.go
+++ b/src/core/api/base.go
@ -83,10 +83,6 @@ func (b *BaseController) Prepare() {
 		return
 	}
 	b.ProjectMgr = pm
-
-	if !filter.ReqCarriesSession(b.Ctx.Request) {
-		b.EnableXSRF = false
-	}
 }

 // RequireAuthenticated returns true when the request is authenticated
@ -96,7 +92,6 @@ func (b *BaseController) RequireAuthenticated() bool {
 		b.SendError(internal_errors.UnauthorizedError(errors.New("Unauthorized")))
 		return false
 	}
-
 	return true
 }

--- a/src/core/controllers/controllers_test.go
+++ b/src/core/controllers/controllers_test.go
@ -16,6 +16,7 @@ package controllers
 import (
 	"context"
 	"fmt"
+	"github.com/goharbor/harbor/src/core/middlewares"
 	"net/http"
 	"net/http/httptest"
 	"os"
@ -38,7 +39,6 @@ func init() {
 	dir := filepath.Dir(file)
 	dir = filepath.Join(dir, "..")
 	apppath, _ := filepath.Abs(dir)
-	beego.BConfig.WebConfig.EnableXSRF = true
 	beego.BConfig.WebConfig.Session.SessionOn = true
 	beego.TestBeegoInit(apppath)
 	beego.AddTemplateExt("htm")
@ -100,30 +100,38 @@ func TestRedirectForOIDC(t *testing.T) {
 func TestAll(t *testing.T) {
 	config.InitWithSettings(utilstest.GetUnitTestConfig())
 	assert := assert.New(t)
+	handler := http.Handler(beego.BeeApp.Handlers)
+	mws := middlewares.MiddleWares()
+	for i := len(mws) - 1; i >= 0; i-- {
+		if mws[i] == nil {
+			continue
+		}
+		handler = mws[i](handler)
+	}

 	r, _ := http.NewRequest("POST", "/c/login", nil)
 	w := httptest.NewRecorder()
-	beego.BeeApp.Handlers.ServeHTTP(w, r)
-	assert.Equal(http.StatusUnprocessableEntity, w.Code, "'/c/login' httpStatusCode should be 422")
+	handler.ServeHTTP(w, r)
+	assert.Equal(http.StatusForbidden, w.Code, "'/c/login' httpStatusCode should be 403")

 	r, _ = http.NewRequest("GET", "/c/log_out", nil)
 	w = httptest.NewRecorder()
-	beego.BeeApp.Handlers.ServeHTTP(w, r)
+	handler.ServeHTTP(w, r)
 	assert.Equal(int(200), w.Code, "'/c/log_out' httpStatusCode should be 200")
 	assert.Equal(true, strings.Contains(fmt.Sprintf("%s", w.Body), ""), "http respond should be empty")

 	r, _ = http.NewRequest("POST", "/c/reset", nil)
 	w = httptest.NewRecorder()
-	beego.BeeApp.Handlers.ServeHTTP(w, r)
-	assert.Equal(http.StatusUnprocessableEntity, w.Code, "'/c/reset' httpStatusCode should be 422")
+	handler.ServeHTTP(w, r)
+	assert.Equal(http.StatusForbidden, w.Code, "'/c/reset' httpStatusCode should be 403")

 	r, _ = http.NewRequest("POST", "/c/userExists", nil)
 	w = httptest.NewRecorder()
-	beego.BeeApp.Handlers.ServeHTTP(w, r)
-	assert.Equal(http.StatusUnprocessableEntity, w.Code, "'/c/userExists' httpStatusCode should be 422")
+	handler.ServeHTTP(w, r)
+	assert.Equal(http.StatusForbidden, w.Code, "'/c/userExists' httpStatusCode should be 403")

 	r, _ = http.NewRequest("GET", "/c/sendEmail", nil)
 	w = httptest.NewRecorder()
-	beego.BeeApp.Handlers.ServeHTTP(w, r)
+	handler.ServeHTTP(w, r)
 	assert.Equal(int(400), w.Code, "'/c/sendEmail' httpStatusCode should be 400")
 }
--- a/src/core/filter/sessionchecker.go
+++ b/src/core/filter/sessionchecker.go
@ -18,11 +18,8 @@ func SessionCheck(ctx *beegoctx.Context) {
 	req := ctx.Request
 	_, err := req.Cookie(config.SessionCookieName)
 	if err == nil {
-		// This is a temp workaround for beego bug: https://github.com/goharbor/harbor/issues/10446
-		// After we upgrading beego to the latest version and moving the filter to middleware,
-		// this workaround can be removed
-		*(ctx.Request) = *(req.WithContext(context.WithValue(req.Context(), SessionReqKey, true)))
-		log.Debug("Mark the request as no-session")
+		ctx.Request = req.WithContext(context.WithValue(req.Context(), SessionReqKey, true))
+		log.Debugf("Mark the request as with-session: %s %s", req.Method, req.URL.RawPath)
 	}
 }

--- a/src/core/middlewares/middlewares.go
+++ b/src/core/middlewares/middlewares.go
@ -15,6 +15,7 @@
 package middlewares

 import (
+	"github.com/goharbor/harbor/src/server/middleware/csrf"
 	"github.com/goharbor/harbor/src/server/middleware/readonly"
 	"net/http"
 	"path"
@ -71,6 +72,7 @@ func legacyAPISkipper(r *http.Request) bool {
 // MiddleWares returns global middlewares
 func MiddleWares() []beego.MiddleWare {
 	return []beego.MiddleWare{
+		csrf.Middleware(),
 		requestid.Middleware(),
 		readonly.Middleware(readonlySkippers...),
 		orm.Middleware(legacyAPISkipper),
--- a/src/core/service/notifications/base.go
+++ b/src/core/service/notifications/base.go
@ -6,8 +6,3 @@ import "github.com/goharbor/harbor/src/core/api"
 type BaseHandler struct {
 	api.BaseController
 }
-
-// Prepare disable the xsrf as the request is from other components and do not require the xsrf token
-func (bh *BaseHandler) Prepare() {
-	bh.EnableXSRF = false
-}
--- a/src/core/service/token/token.go
+++ b/src/core/service/token/token.go
@ -27,13 +27,6 @@ type Handler struct {
 	beego.Controller
 }

-// Prepare disables xsrf for /service/token endpoint.
-// This is done on purpose b/c containerd will try to send POST and fallback to GET
-// more details see #10305
-func (h *Handler) Prepare() {
-	h.EnableXSRF = false
-}
-
 // Get handles GET request, it checks the http header for user credentials
 // and parse service and scope based on docker registry v2 standard,
 // checks the permission against local DB and generates jwt token.
--- a/src/go.mod
+++ b/src/go.mod
@ -44,6 +44,7 @@ require (
 	github.com/google/certificate-transparency-go v1.0.21 // indirect
 	github.com/google/go-querystring v0.0.0-20170111101155-53e6ce116135 // indirect
 	github.com/google/uuid v1.1.1
+	github.com/gorilla/csrf v1.6.2
 	github.com/gorilla/handlers v1.3.0
 	github.com/gorilla/mux v1.7.2
 	github.com/graph-gophers/dataloader v5.0.0+incompatible
--- a/src/go.sum
+++ b/src/go.sum
@ -342,6 +342,8 @@ github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1 h1:EGx4pi6eqNxGa
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
 github.com/gorilla/context v1.1.1 h1:AWwleXJkX/nhcU9bZSnZoi3h/qGYqQAGhq6zZe/aQW8=
 github.com/gorilla/context v1.1.1/go.mod h1:kBGZzfjB9CEq2AlWe17Uuf7NDRt0dE0s8S51q0aT7Yg=
+github.com/gorilla/csrf v1.6.2 h1:QqQ/OWwuFp4jMKgBFAzJVW3FMULdyUW7JoM4pEWuqKg=
+github.com/gorilla/csrf v1.6.2/go.mod h1:7tSf8kmjNYr7IWDCYhd3U8Ck34iQ/Yw5CJu7bAkHEGI=
 github.com/gorilla/handlers v0.0.0-20150720190736-60c7bfde3e33/go.mod h1:Qkdc/uu4tH4g6mTK6auzZ766c4CA0Ng8+o/OAirnOIQ=
 github.com/gorilla/handlers v1.3.0 h1:tsg9qP3mjt1h4Roxp+M1paRjrVBfPSOpBuVclh6YluI=
 github.com/gorilla/handlers v1.3.0/go.mod h1:Qkdc/uu4tH4g6mTK6auzZ766c4CA0Ng8+o/OAirnOIQ=
@ -349,6 +351,8 @@ github.com/gorilla/mux v1.6.2 h1:Pgr17XVTNXAk3q/r4CpKzC5xBM/qW1uVLV+IhRZpIIk=
 github.com/gorilla/mux v1.6.2/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
 github.com/gorilla/mux v1.7.2 h1:zoNxOV7WjqXptQOVngLmcSQgXmgk4NMz1HibBchjl/I=
 github.com/gorilla/mux v1.7.2/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
+github.com/gorilla/securecookie v1.1.1 h1:miw7JPhV+b/lAHSXz4qd/nN9jRiAFV5FwjeKyCS8BvQ=
+github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+HVt/4epWDjd4=
 github.com/gorilla/websocket v0.0.0-20170926233335-4201258b820c/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
 github.com/gosuri/uitable v0.0.4/go.mod h1:tKR86bXuXPZazfOTG1FIzvjIdXzd0mo4Vtn16vt0PJo=
--- a/src/server/middleware/csrf/csrf.go
+++ b/src/server/middleware/csrf/csrf.go
@ -0,0 +1,89 @@
+package csrf
+
+import (
+	"github.com/goharbor/harbor/src/common/utils"
+	"github.com/goharbor/harbor/src/common/utils/log"
+	"github.com/goharbor/harbor/src/core/config"
+	ierror "github.com/goharbor/harbor/src/internal/error"
+	serror "github.com/goharbor/harbor/src/server/error"
+	"github.com/goharbor/harbor/src/server/middleware"
+	"github.com/gorilla/csrf"
+	"net/http"
+	"os"
+	"strings"
+	"sync"
+)
+
+const (
+	csrfKeyEnv  = "CSRF_KEY"
+	tokenHeader = "X-Harbor-CSRF-Token"
+	tokenCookie = "__csrf"
+)
+
+var (
+	once    sync.Once
+	protect func(handler http.Handler) http.Handler
+)
+
+// attachToken makes sure if csrf generate a new token it will be included in the response header
+func attachToken(w http.ResponseWriter, r *http.Request) {
+	if t := csrf.Token(r); len(t) > 0 {
+		http.SetCookie(w, &http.Cookie{
+			Name:     tokenCookie,
+			Secure:   true,
+			Value:    t,
+			Path:     "/",
+			SameSite: http.SameSiteStrictMode,
+		})
+	} else {
+		log.Warningf("token not found in context, skip attaching")
+	}
+}
+
+func handleError(w http.ResponseWriter, r *http.Request) {
+	attachToken(w, r)
+	serror.SendError(w, ierror.New(csrf.FailureReason(r)).WithCode(ierror.ForbiddenCode))
+	return
+}
+
+func attach(handler http.Handler) http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		attachToken(rw, req)
+		handler.ServeHTTP(rw, req)
+	})
+}
+
+// Middleware initialize the middleware to apply csrf selectively
+func Middleware() func(handler http.Handler) http.Handler {
+	once.Do(func() {
+		key := os.Getenv(csrfKeyEnv)
+		if len(key) != 32 {
+			log.Warningf("Invalid CSRF key from environment: %s, generating random key...", key)
+			key = utils.GenerateRandomString()
+
+		}
+		protect = csrf.Protect([]byte(key), csrf.RequestHeader(tokenHeader),
+			csrf.ErrorHandler(http.HandlerFunc(handleError)),
+			csrf.SameSite(csrf.SameSiteStrictMode),
+			csrf.Path("/"))
+	})
+	return middleware.New(func(rw http.ResponseWriter, req *http.Request, next http.Handler) {
+		protect(attach(next)).ServeHTTP(rw, req)
+	}, csrfSkipper)
+}
+
+// csrfSkipper makes sure only some of the uris accessed by non-UI client can skip the csrf check
+func csrfSkipper(req *http.Request) bool {
+	path := req.URL.Path
+	// We can check the cookie directly b/c the filter and controllerRegistry is executed after middleware, so no session
+	// cookie is added by beego.
+	_, err := req.Cookie(config.SessionCookieName)
+	hasSession := err == nil
+	if (strings.HasPrefix(path, "/v2/") ||
+		strings.HasPrefix(path, "/api/") ||
+		strings.HasPrefix(path, "/chartrepo/") ||
+		strings.HasPrefix(path, "/service/")) && !hasSession {
+		return true
+	}
+	return false
+}
--- a/src/server/middleware/csrf/csrf_test.go
+++ b/src/server/middleware/csrf/csrf_test.go
@ -0,0 +1,60 @@
+package csrf
+
+import (
+	"github.com/stretchr/testify/assert"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+type handler struct {
+}
+
+func (h *handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	w.WriteHeader(http.StatusOK)
+}
+
+func TestMiddleware(t *testing.T) {
+	srv := Middleware()(&handler{})
+	cases := []struct {
+		req         *http.Request
+		statusCode  int
+		returnToken bool
+	}{
+		{
+			req:         httptest.NewRequest(http.MethodGet, "/", nil),
+			statusCode:  http.StatusOK,
+			returnToken: true,
+		},
+		{
+			req:         httptest.NewRequest(http.MethodDelete, "/", nil),
+			statusCode:  http.StatusForbidden,
+			returnToken: true,
+		},
+		{
+			req:         httptest.NewRequest(http.MethodGet, "/api/2.0/projects", nil), // should be skipped
+			statusCode:  http.StatusOK,
+			returnToken: false,
+		},
+		{
+			req:         httptest.NewRequest(http.MethodDelete, "/v2/library/hello-world/manifests/latest", nil), // should be skipped
+			statusCode:  http.StatusOK,
+			returnToken: false,
+		},
+	}
+	for _, c := range cases {
+		rec := httptest.NewRecorder()
+		srv.ServeHTTP(rec, c.req)
+		assert.Equal(t, c.statusCode, rec.Result().StatusCode)
+		assert.Equal(t, c.returnToken, hasCookie(rec.Result(), tokenCookie))
+	}
+}
+
+func hasCookie(resp *http.Response, name string) bool {
+	for _, c := range resp.Cookies() {
+		if c != nil && c.Name == name {
+			return true
+		}
+	}
+	return false
+}
--- a/src/vendor/github.com/gorilla/csrf/AUTHORS
+++ b/src/vendor/github.com/gorilla/csrf/AUTHORS
@ -0,0 +1,20 @@
+# This is the official list of gorilla/csrf authors for copyright purposes.
+# Please keep the list sorted.
+
+adiabatic <adiabatic@users.noreply.github.com>
+Google LLC (https://opensource.google.com)
+jamesgroat <james@groat.com>
+Joshua Carp <jm.carp@gmail.com>
+Kamil Kisiel <kamil@kamilkisiel.net>
+Kevin Burke <kev@inburke.com>
+Kévin Dunglas <dunglas@gmail.com>
+Kristoffer Berdal <web@flexd.net>
+Martin Angers <martin.n.angers@gmail.com>
+Matt Silverlock <matt@eatsleeprepeat.net>
+Philip I. Thomas <mail@philipithomas.com>
+Richard Musiol <mail@richard-musiol.de>
+Seth Hoenig <seth.a.hoenig@gmail.com>
+Stefano Vettorazzi <stefanovc@gmail.com>
+Wayne Ashley Berry <wayneashleyberry@gmail.com>
+田浩浩 <llitfkitfk@gmail.com>
+陈东海 <cdh_cjx@163.com>
--- a/src/vendor/github.com/gorilla/csrf/Gopkg.lock
+++ b/src/vendor/github.com/gorilla/csrf/Gopkg.lock
@ -0,0 +1,27 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/gorilla/context"
+  packages = ["."]
+  revision = "1ea25387ff6f684839d82767c1733ff4d4d15d0a"
+  version = "v1.1"
+
+[[projects]]
+  name = "github.com/gorilla/securecookie"
+  packages = ["."]
+  revision = "667fe4e3466a040b780561fe9b51a83a3753eefc"
+  version = "v1.1"
+
+[[projects]]
+  name = "github.com/pkg/errors"
+  packages = ["."]
+  revision = "645ef00459ed84a119197bfb8d8205042c6df63d"
+  version = "v0.8.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "1695686bc8fa0eb76df9fe8c5ca473686071ddcf795a0595a9465a03e8ac9bef"
+  solver-name = "gps-cdcl"
+  solver-version = 1
--- a/src/vendor/github.com/gorilla/csrf/Gopkg.toml
+++ b/src/vendor/github.com/gorilla/csrf/Gopkg.toml
@ -0,0 +1,34 @@
+
+# Gopkg.toml example
+#
+# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#  name = "github.com/x/y"
+#  version = "2.4.0"
+
+
+[[constraint]]
+  name = "github.com/gorilla/context"
+  version = "1.1.0"
+
+[[constraint]]
+  name = "github.com/gorilla/securecookie"
+  version = "1.1.0"
+
+[[constraint]]
+  name = "github.com/pkg/errors"
+  version = "0.8.0"
--- a/src/vendor/github.com/gorilla/csrf/LICENSE
+++ b/src/vendor/github.com/gorilla/csrf/LICENSE
@ -0,0 +1,26 @@
+Copyright (c) 2015-2018, The Gorilla Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation and/or
+other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors
+may be used to endorse or promote products derived from this software without
+specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--- a/src/vendor/github.com/gorilla/csrf/README.md
+++ b/src/vendor/github.com/gorilla/csrf/README.md
@ -0,0 +1,352 @@
+# gorilla/csrf
+
+[![GoDoc](https://godoc.org/github.com/gorilla/csrf?status.svg)](https://godoc.org/github.com/gorilla/csrf)
+[![Sourcegraph](https://sourcegraph.com/github.com/gorilla/csrf/-/badge.svg)](https://sourcegraph.com/github.com/gorilla/csrf?badge)
+[![Reviewed by Hound](https://img.shields.io/badge/Reviewed_by-Hound-8E64B0.svg)](https://houndci.com)
+[![CircleCI](https://circleci.com/gh/gorilla/csrf.svg?style=svg)](https://circleci.com/gh/gorilla/csrf)
+
+gorilla/csrf is a HTTP middleware library that provides [cross-site request
+forgery](http://blog.codinghorror.com/preventing-csrf-and-xsrf-attacks/) (CSRF)
+protection. It includes:
+
+- The `csrf.Protect` middleware/handler provides CSRF protection on routes
+  attached to a router or a sub-router.
+- A `csrf.Token` function that provides the token to pass into your response,
+  whether that be a HTML form or a JSON response body.
+- ... and a `csrf.TemplateField` helper that you can pass into your `html/template`
+  templates to replace a `{{ .csrfField }}` template tag with a hidden input
+  field.
+
+gorilla/csrf is designed to work with any Go web framework, including:
+
+- The [Gorilla](https://www.gorillatoolkit.org/) toolkit
+- Go's built-in [net/http](http://golang.org/pkg/net/http/) package
+- [Goji](https://goji.io) - see the [tailored fork](https://github.com/goji/csrf)
+- [Gin](https://github.com/gin-gonic/gin)
+- [Echo](https://github.com/labstack/echo)
+- ... and any other router/framework that rallies around Go's `http.Handler` interface.
+
+gorilla/csrf is also compatible with middleware 'helper' libraries like
+[Alice](https://github.com/justinas/alice) and [Negroni](https://github.com/codegangsta/negroni).
+
+## Install
+
+With a properly configured Go toolchain:
+
+```sh
+go get github.com/gorilla/csrf
+```
+
+## Examples
+
+- [HTML Forms](#html-forms)
+- [JavaScript Apps](#javascript-applications)
+- [Google App Engine](#google-app-engine)
+- [Setting SameSite](#setting-samesite)
+- [Setting Options](#setting-options)
+
+gorilla/csrf is easy to use: add the middleware to your router with
+the below:
+
+```go
+CSRF := csrf.Protect([]byte("32-byte-long-auth-key"))
+http.ListenAndServe(":8000", CSRF(r))
+```
+
+...and then collect the token with `csrf.Token(r)` in your handlers before
+passing it to the template, JSON body or HTTP header (see below).
+
+Note that the authentication key passed to `csrf.Protect([]byte(key))` should be
+32-bytes long and persist across application restarts. Generating a random key
+won't allow you to authenticate existing cookies and will break your CSRF
+validation.
+
+gorilla/csrf inspects the HTTP headers (first) and form body (second) on
+subsequent POST/PUT/PATCH/DELETE/etc. requests for the token.
+
+### HTML Forms
+
+Here's the common use-case: HTML forms you want to provide CSRF protection for,
+in order to protect malicious POST requests being made:
+
+```go
+package main
+
+import (
+    "net/http"
+
+    "github.com/gorilla/csrf"
+    "github.com/gorilla/mux"
+)
+
+func main() {
+    r := mux.NewRouter()
+    r.HandleFunc("/signup", ShowSignupForm)
+    // All POST requests without a valid token will return HTTP 403 Forbidden.
+    // We should also ensure that our mutating (non-idempotent) handler only
+    // matches on POST requests. We can check that here, at the router level, or
+    // within the handler itself via r.Method.
+    r.HandleFunc("/signup/post", SubmitSignupForm).Methods("POST")
+
+    // Add the middleware to your router by wrapping it.
+    http.ListenAndServe(":8000",
+        csrf.Protect([]byte("32-byte-long-auth-key"))(r))
+    // PS: Don't forget to pass csrf.Secure(false) if you're developing locally
+    // over plain HTTP (just don't leave it on in production).
+}
+
+func ShowSignupForm(w http.ResponseWriter, r *http.Request) {
+    // signup_form.tmpl just needs a {{ .csrfField }} template tag for
+    // csrf.TemplateField to inject the CSRF token into. Easy!
+    t.ExecuteTemplate(w, "signup_form.tmpl", map[string]interface{}{
+        csrf.TemplateTag: csrf.TemplateField(r),
+    })
+    // We could also retrieve the token directly from csrf.Token(r) and
+    // set it in the request header - w.Header.Set("X-CSRF-Token", token)
+    // This is useful if you're sending JSON to clients or a front-end JavaScript
+    // framework.
+}
+
+func SubmitSignupForm(w http.ResponseWriter, r *http.Request) {
+    // We can trust that requests making it this far have satisfied
+    // our CSRF protection requirements.
+}
+```
+
+Note that the CSRF middleware will (by necessity) consume the request body if the
+token is passed via POST form values. If you need to consume this in your
+handler, insert your own middleware earlier in the chain to capture the request
+body.
+
+### JavaScript Applications
+
+This approach is useful if you're using a front-end JavaScript framework like
+React, Ember or Angular, and are providing a JSON API. Specifically, we need
+to provide a way for our front-end fetch/AJAX calls to pass the token on each
+fetch (AJAX/XMLHttpRequest) request. We achieve this by:
+
+- Parsing the token from the `<input>` field generated by the
+  `csrf.TemplateField(r)` helper, or passing it back in a response header.
+- Sending this token back on every request
+- Ensuring our cookie is attached to the request so that the form/header
+  value can be compared to the cookie value.
+
+We'll also look at applying selective CSRF protection using
+[gorilla/mux's](https://www.gorillatoolkit.org/pkg/mux) sub-routers,
+as we don't handle any POST/PUT/DELETE requests with our top-level router.
+
+```go
+package main
+
+import (
+    "github.com/gorilla/csrf"
+    "github.com/gorilla/mux"
+)
+
+func main() {
+    r := mux.NewRouter()
+    csrfMiddleware := csrf.Protect([]byte("32-byte-long-auth-key"))
+
+    api := r.PathPrefix("/api").Subrouter()
+    api.Use(csrfMiddleware)
+    api.HandleFunc("/user/{id}", GetUser).Methods("GET")
+
+    http.ListenAndServe(":8000", r)
+}
+
+func GetUser(w http.ResponseWriter, r *http.Request) {
+    // Authenticate the request, get the id from the route params,
+    // and fetch the user from the DB, etc.
+
+    // Get the token and pass it in the CSRF header. Our JSON-speaking client
+    // or JavaScript framework can now read the header and return the token in
+    // in its own "X-CSRF-Token" request header on the subsequent POST.
+    w.Header().Set("X-CSRF-Token", csrf.Token(r))
+    b, err := json.Marshal(user)
+    if err != nil {
+        http.Error(w, err.Error(), 500)
+        return
+    }
+
+    w.Write(b)
+}
+```
+
+In our JavaScript application, we should read the token from the response
+headers and pass it in a request header for all requests. Here's what that
+looks like when using [Axios](https://github.com/axios/axios), a popular
+JavaScript HTTP client library:
+
+```js
+// You can alternatively parse the response header for the X-CSRF-Token, and
+// store that instead, if you followed the steps above to write the token to a
+// response header.
+let csrfToken = document.getElementsByName("gorilla.csrf.Token")[0].value
+
+// via https://github.com/axios/axios#creating-an-instance
+const instance = axios.create({
+  baseURL: "https://example.com/api/",
+  timeout: 1000,
+  headers: { "X-CSRF-Token": csrfToken }
+})
+
+// Now, any HTTP request you make will include the csrfToken from the page,
+// provided you update the csrfToken variable for each render.
+try {
+  let resp = await instance.post(endpoint, formData)
+  // Do something with resp
+} catch (err) {
+  // Handle the exception
+}
+```
+
+If you plan to host your JavaScript application on another domain, you can use the Trusted Origins
+feature to allow the host of your JavaScript application to make requests to your Go application. Observe the example below:
+
+
+```go
+package main
+
+import (
+    "github.com/gorilla/csrf"
+    "github.com/gorilla/mux"
+)
+
+func main() {
+    r := mux.NewRouter()
+    csrfMiddleware := csrf.Protect([]byte("32-byte-long-auth-key"), csrf.TrustedOrigin([]string{"ui.domain.com"}))
+
+    api := r.PathPrefix("/api").Subrouter()
+    api.Use(csrfMiddleware)
+    api.HandleFunc("/user/{id}", GetUser).Methods("GET")
+
+    http.ListenAndServe(":8000", r)
+}
+
+func GetUser(w http.ResponseWriter, r *http.Request) {
+    // Authenticate the request, get the id from the route params,
+    // and fetch the user from the DB, etc.
+
+    // Get the token and pass it in the CSRF header. Our JSON-speaking client
+    // or JavaScript framework can now read the header and return the token in
+    // in its own "X-CSRF-Token" request header on the subsequent POST.
+    w.Header().Set("X-CSRF-Token", csrf.Token(r))
+    b, err := json.Marshal(user)
+    if err != nil {
+        http.Error(w, err.Error(), 500)
+        return
+    }
+
+    w.Write(b)
+}
+```
+
+On the example above, you're authorizing requests from `ui.domain.com` to make valid CSRF requests to your application, so you can have your API server on another domain without problems.
+
+### Google App Engine
+
+If you're using [Google App
+Engine](https://cloud.google.com/appengine/docs/go/how-requests-are-handled#Go_Requests_and_HTTP),
+(first-generation) which doesn't allow you to hook into the default `http.ServeMux` directly,
+you can still use gorilla/csrf (and gorilla/mux):
+
+```go
+package app
+
+// Remember: appengine has its own package main
+func init() {
+    r := mux.NewRouter()
+    r.HandleFunc("/", IndexHandler)
+    // ...
+
+    // We pass our CSRF-protected router to the DefaultServeMux
+    http.Handle("/", csrf.Protect([]byte(your-key))(r))
+}
+```
+
+Note: You can ignore this if you're using the
+[second-generation](https://cloud.google.com/appengine/docs/go/) Go runtime
+on App Engine (Go 1.11 and above).
+
+### Setting SameSite
+
+Go 1.11 introduced the option to set the SameSite attribute in cookies. This is
+valuable if a developer wants to instruct a browser to not include cookies during
+a cross site request. SameSiteStrictMode prevents all cross site requests from including
+the cookie. SameSiteLaxMode prevents CSRF prone requests (POST) from including the cookie
+but allows the cookie to be included in GET requests to support external linking.
+
+```go
+func main() {
+    CSRF := csrf.Protect(
+      []byte("a-32-byte-long-key-goes-here"),
+      // instruct the browser to never send cookies during cross site requests
+      csrf.SameSite(csrf.SameSiteStrictMode),
+    )
+
+    r := mux.NewRouter()
+    r.HandleFunc("/signup", GetSignupForm)
+    r.HandleFunc("/signup/post", PostSignupForm)
+
+    http.ListenAndServe(":8000", CSRF(r))
+}
+```
+
+### Setting Options
+
+What about providing your own error handler and changing the HTTP header the
+package inspects on requests? (i.e. an existing API you're porting to Go). Well,
+gorilla/csrf provides options for changing these as you see fit:
+
+```go
+func main() {
+    CSRF := csrf.Protect(
+            []byte("a-32-byte-long-key-goes-here"),
+            csrf.RequestHeader("Authenticity-Token"),
+            csrf.FieldName("authenticity_token"),
+            csrf.ErrorHandler(http.HandlerFunc(serverError(403))),
+    )
+
+    r := mux.NewRouter()
+    r.HandleFunc("/signup", GetSignupForm)
+    r.HandleFunc("/signup/post", PostSignupForm)
+
+    http.ListenAndServe(":8000", CSRF(r))
+}
+```
+
+Not too bad, right?
+
+If there's something you're confused about or a feature you would like to see
+added, open an issue.
+
+## Design Notes
+
+Getting CSRF protection right is important, so here's some background:
+
+- This library generates unique-per-request (masked) tokens as a mitigation
+  against the [BREACH attack](http://breachattack.com/).
+- The 'base' (unmasked) token is stored in the session, which means that
+  multiple browser tabs won't cause a user problems as their per-request token
+  is compared with the base token.
+- Operates on a "whitelist only" approach where safe (non-mutating) HTTP methods
+  (GET, HEAD, OPTIONS, TRACE) are the _only_ methods where token validation is not
+  enforced.
+- The design is based on the battle-tested
+  [Django](https://docs.djangoproject.com/en/1.8/ref/csrf/) and [Ruby on
+  Rails](http://api.rubyonrails.org/classes/ActionController/RequestForgeryProtection.html)
+  approaches.
+- Cookies are authenticated and based on the [securecookie](https://github.com/gorilla/securecookie)
+  library. They're also Secure (issued over HTTPS only) and are HttpOnly
+  by default, because sane defaults are important.
+- Cookie SameSite attribute (prevents cookies from being sent by a browser
+  during cross site requests) are not set by default to maintain backwards compatibility
+  for legacy systems. The SameSite attribute can be set with the SameSite option.
+- Go's `crypto/rand` library is used to generate the 32 byte (256 bit) tokens
+  and the one-time-pad used for masking them.
+
+This library does not seek to be adventurous.
+
+## License
+
+BSD licensed. See the LICENSE file for details.
--- a/src/vendor/github.com/gorilla/csrf/context.go
+++ b/src/vendor/github.com/gorilla/csrf/context.go
@ -0,0 +1,29 @@
+// +build go1.7
+
+package csrf
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/pkg/errors"
+)
+
+func contextGet(r *http.Request, key string) (interface{}, error) {
+	val := r.Context().Value(key)
+	if val == nil {
+		return nil, errors.Errorf("no value exists in the context for key %q", key)
+	}
+
+	return val, nil
+}
+
+func contextSave(r *http.Request, key string, val interface{}) *http.Request {
+	ctx := r.Context()
+	ctx = context.WithValue(ctx, key, val)
+	return r.WithContext(ctx)
+}
+
+func contextClear(r *http.Request) {
+	// no-op for go1.7+
+}
--- a/src/vendor/github.com/gorilla/csrf/csrf.go
+++ b/src/vendor/github.com/gorilla/csrf/csrf.go
@ -0,0 +1,309 @@
+package csrf
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/pkg/errors"
+
+	"github.com/gorilla/securecookie"
+)
+
+// CSRF token length in bytes.
+const tokenLength = 32
+
+// Context/session keys & prefixes
+const (
+	tokenKey     string = "gorilla.csrf.Token"
+	formKey      string = "gorilla.csrf.Form"
+	errorKey     string = "gorilla.csrf.Error"
+	skipCheckKey string = "gorilla.csrf.Skip"
+	cookieName   string = "_gorilla_csrf"
+	errorPrefix  string = "gorilla/csrf: "
+)
+
+var (
+	// The name value used in form fields.
+	fieldName = tokenKey
+	// defaultAge sets the default MaxAge for cookies.
+	defaultAge = 3600 * 12
+	// The default HTTP request header to inspect
+	headerName = "X-CSRF-Token"
+	// Idempotent (safe) methods as defined by RFC7231 section 4.2.2.
+	safeMethods = []string{"GET", "HEAD", "OPTIONS", "TRACE"}
+)
+
+// TemplateTag provides a default template tag - e.g. {{ .csrfField }} - for use
+// with the TemplateField function.
+var TemplateTag = "csrfField"
+
+var (
+	// ErrNoReferer is returned when a HTTPS request provides an empty Referer
+	// header.
+	ErrNoReferer = errors.New("referer not supplied")
+	// ErrBadReferer is returned when the scheme & host in the URL do not match
+	// the supplied Referer header.
+	ErrBadReferer = errors.New("referer invalid")
+	// ErrNoToken is returned if no CSRF token is supplied in the request.
+	ErrNoToken = errors.New("CSRF token not found in request")
+	// ErrBadToken is returned if the CSRF token in the request does not match
+	// the token in the session, or is otherwise malformed.
+	ErrBadToken = errors.New("CSRF token invalid")
+)
+
+// SameSiteMode allows a server to define a cookie attribute making it impossible for
+// the browser to send this cookie along with cross-site requests. The main
+// goal is to mitigate the risk of cross-origin information leakage, and provide
+// some protection against cross-site request forgery attacks.
+//
+// See https://tools.ietf.org/html/draft-ietf-httpbis-cookie-same-site-00 for details.
+type SameSiteMode int
+
+// SameSite options
+const (
+	SameSiteDefaultMode SameSiteMode = iota + 1
+	SameSiteLaxMode
+	SameSiteStrictMode
+	SameSiteNoneMode
+)
+
+type csrf struct {
+	h    http.Handler
+	sc   *securecookie.SecureCookie
+	st   store
+	opts options
+}
+
+// options contains the optional settings for the CSRF middleware.
+type options struct {
+	MaxAge int
+	Domain string
+	Path   string
+	// Note that the function and field names match the case of the associated
+	// http.Cookie field instead of the "correct" HTTPOnly name that golint suggests.
+	HttpOnly       bool
+	Secure         bool
+	SameSite       SameSiteMode
+	RequestHeader  string
+	FieldName      string
+	ErrorHandler   http.Handler
+	CookieName     string
+	TrustedOrigins []string
+}
+
+// Protect is HTTP middleware that provides Cross-Site Request Forgery
+// protection.
+//
+// It securely generates a masked (unique-per-request) token that
+// can be embedded in the HTTP response (e.g. form field or HTTP header).
+// The original (unmasked) token is stored in the session, which is inaccessible
+// by an attacker (provided you are using HTTPS). Subsequent requests are
+// expected to include this token, which is compared against the session token.
+// Requests that do not provide a matching token are served with a HTTP 403
+// 'Forbidden' error response.
+//
+// Example:
+//	package main
+//
+//	import (
+//		"html/template"
+//
+//		"github.com/gorilla/csrf"
+//		"github.com/gorilla/mux"
+//	)
+//
+//	var t = template.Must(template.New("signup_form.tmpl").Parse(form))
+//
+//	func main() {
+//		r := mux.NewRouter()
+//
+//		r.HandleFunc("/signup", GetSignupForm)
+//		// POST requests without a valid token will return a HTTP 403 Forbidden.
+//		r.HandleFunc("/signup/post", PostSignupForm)
+//
+//		// Add the middleware to your router.
+//		http.ListenAndServe(":8000",
+//		// Note that the authentication key provided should be 32 bytes
+//		// long and persist across application restarts.
+//			  csrf.Protect([]byte("32-byte-long-auth-key"))(r))
+//	}
+//
+//	func GetSignupForm(w http.ResponseWriter, r *http.Request) {
+//		// signup_form.tmpl just needs a {{ .csrfField }} template tag for
+//		// csrf.TemplateField to inject the CSRF token into. Easy!
+//		t.ExecuteTemplate(w, "signup_form.tmpl", map[string]interface{}{
+//			csrf.TemplateTag: csrf.TemplateField(r),
+//		})
+//		// We could also retrieve the token directly from csrf.Token(r) and
+//		// set it in the request header - w.Header.Set("X-CSRF-Token", token)
+//		// This is useful if you're sending JSON to clients or a front-end JavaScript
+//		// framework.
+//	}
+//
+func Protect(authKey []byte, opts ...Option) func(http.Handler) http.Handler {
+	return func(h http.Handler) http.Handler {
+		cs := parseOptions(h, opts...)
+
+		// Set the defaults if no options have been specified
+		if cs.opts.ErrorHandler == nil {
+			cs.opts.ErrorHandler = http.HandlerFunc(unauthorizedHandler)
+		}
+
+		if cs.opts.MaxAge < 0 {
+			// Default of 12 hours
+			cs.opts.MaxAge = defaultAge
+		}
+
+		if cs.opts.FieldName == "" {
+			cs.opts.FieldName = fieldName
+		}
+
+		if cs.opts.CookieName == "" {
+			cs.opts.CookieName = cookieName
+		}
+
+		if cs.opts.RequestHeader == "" {
+			cs.opts.RequestHeader = headerName
+		}
+
+		// Create an authenticated securecookie instance.
+		if cs.sc == nil {
+			cs.sc = securecookie.New(authKey, nil)
+			// Use JSON serialization (faster than one-off gob encoding)
+			cs.sc.SetSerializer(securecookie.JSONEncoder{})
+			// Set the MaxAge of the underlying securecookie.
+			cs.sc.MaxAge(cs.opts.MaxAge)
+		}
+
+		if cs.st == nil {
+			// Default to the cookieStore
+			cs.st = &cookieStore{
+				name:     cs.opts.CookieName,
+				maxAge:   cs.opts.MaxAge,
+				secure:   cs.opts.Secure,
+				httpOnly: cs.opts.HttpOnly,
+				sameSite: cs.opts.SameSite,
+				path:     cs.opts.Path,
+				domain:   cs.opts.Domain,
+				sc:       cs.sc,
+			}
+		}
+
+		return cs
+	}
+}
+
+// Implements http.Handler for the csrf type.
+func (cs *csrf) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Skip the check if directed to. This should always be a bool.
+	if val, err := contextGet(r, skipCheckKey); err == nil {
+		if skip, ok := val.(bool); ok {
+			if skip {
+				cs.h.ServeHTTP(w, r)
+				return
+			}
+		}
+	}
+
+	// Retrieve the token from the session.
+	// An error represents either a cookie that failed HMAC validation
+	// or that doesn't exist.
+	realToken, err := cs.st.Get(r)
+	if err != nil || len(realToken) != tokenLength {
+		// If there was an error retrieving the token, the token doesn't exist
+		// yet, or it's the wrong length, generate a new token.
+		// Note that the new token will (correctly) fail validation downstream
+		// as it will no longer match the request token.
+		realToken, err = generateRandomBytes(tokenLength)
+		if err != nil {
+			r = envError(r, err)
+			cs.opts.ErrorHandler.ServeHTTP(w, r)
+			return
+		}
+
+		// Save the new (real) token in the session store.
+		err = cs.st.Save(realToken, w)
+		if err != nil {
+			r = envError(r, err)
+			cs.opts.ErrorHandler.ServeHTTP(w, r)
+			return
+		}
+	}
+
+	// Save the masked token to the request context
+	r = contextSave(r, tokenKey, mask(realToken, r))
+	// Save the field name to the request context
+	r = contextSave(r, formKey, cs.opts.FieldName)
+
+	// HTTP methods not defined as idempotent ("safe") under RFC7231 require
+	// inspection.
+	if !contains(safeMethods, r.Method) {
+		// Enforce an origin check for HTTPS connections. As per the Django CSRF
+		// implementation (https://goo.gl/vKA7GE) the Referer header is almost
+		// always present for same-domain HTTP requests.
+		if r.URL.Scheme == "https" {
+			// Fetch the Referer value. Call the error handler if it's empty or
+			// otherwise fails to parse.
+			referer, err := url.Parse(r.Referer())
+			if err != nil || referer.String() == "" {
+				r = envError(r, ErrNoReferer)
+				cs.opts.ErrorHandler.ServeHTTP(w, r)
+				return
+			}
+
+			valid := sameOrigin(r.URL, referer)
+
+			if !valid {
+				for _, trustedOrigin := range cs.opts.TrustedOrigins {
+					if referer.Host == trustedOrigin {
+						valid = true
+						break
+					}
+				}
+			}
+
+			if valid == false {
+				r = envError(r, ErrBadReferer)
+				cs.opts.ErrorHandler.ServeHTTP(w, r)
+				return
+			}
+		}
+
+		// If the token returned from the session store is nil for non-idempotent
+		// ("unsafe") methods, call the error handler.
+		if realToken == nil {
+			r = envError(r, ErrNoToken)
+			cs.opts.ErrorHandler.ServeHTTP(w, r)
+			return
+		}
+
+		// Retrieve the combined token (pad + masked) token and unmask it.
+		requestToken := unmask(cs.requestToken(r))
+
+		// Compare the request token against the real token
+		if !compareTokens(requestToken, realToken) {
+			r = envError(r, ErrBadToken)
+			cs.opts.ErrorHandler.ServeHTTP(w, r)
+			return
+		}
+
+	}
+
+	// Set the Vary: Cookie header to protect clients from caching the response.
+	w.Header().Add("Vary", "Cookie")
+
+	// Call the wrapped handler/router on success.
+	cs.h.ServeHTTP(w, r)
+	// Clear the request context after the handler has completed.
+	contextClear(r)
+}
+
+// unauthorizedhandler sets a HTTP 403 Forbidden status and writes the
+// CSRF failure reason to the response.
+func unauthorizedHandler(w http.ResponseWriter, r *http.Request) {
+	http.Error(w, fmt.Sprintf("%s - %s",
+		http.StatusText(http.StatusForbidden), FailureReason(r)),
+		http.StatusForbidden)
+	return
+}
--- a/src/vendor/github.com/gorilla/csrf/doc.go
+++ b/src/vendor/github.com/gorilla/csrf/doc.go
@ -0,0 +1,176 @@
+/*
+Package csrf (gorilla/csrf) provides Cross Site Request Forgery (CSRF)
+prevention middleware for Go web applications & services.
+
+It includes:
+
+* The `csrf.Protect` middleware/handler provides CSRF protection on routes
+attached to a router or a sub-router.
+
+* A `csrf.Token` function that provides the token to pass into your response,
+whether that be a HTML form or a JSON response body.
+
+* ... and a `csrf.TemplateField` helper that you can pass into your `html/template`
+templates to replace a `{{ .csrfField }}` template tag with a hidden input
+field.
+
+gorilla/csrf is easy to use: add the middleware to individual handlers with
+the below:
+
+    CSRF := csrf.Protect([]byte("32-byte-long-auth-key"))
+    http.HandlerFunc("/route", CSRF(YourHandler))
+
+... and then collect the token with `csrf.Token(r)` before passing it to the
+template, JSON body or HTTP header (you pick!). gorilla/csrf inspects the form body
+(first) and HTTP headers (second) on subsequent POST/PUT/PATCH/DELETE/etc. requests
+for the token.
+
+Note that the authentication key passed to `csrf.Protect([]byte(key))` should be
+32-bytes long and persist across application restarts. Generating a random key
+won't allow you to authenticate existing cookies and will break your CSRF
+validation.
+
+Here's the common use-case: HTML forms you want to provide CSRF protection for,
+in order to protect malicious POST requests being made:
+
+	package main
+
+	import (
+		"fmt"
+		"html/template"
+		"net/http"
+
+		"github.com/gorilla/csrf"
+		"github.com/gorilla/mux"
+	)
+
+	var form = `
+	<html>
+	<head>
+	<title>Sign Up!</title>
+	</head>
+	<body>
+	<form method="POST" action="/signup/post" accept-charset="UTF-8">
+	<input type="text" name="name">
+	<input type="text" name="email">
+	<!--
+	The default template tag used by the CSRF middleware .
+	This will be replaced with a hidden <input> field containing the
+	masked CSRF token.
+	-->
+	{{ .csrfField }}
+	<input type="submit" value="Sign up!">
+	</form>
+	</body>
+	</html>
+	`
+
+	var t = template.Must(template.New("signup_form.tmpl").Parse(form))
+
+	func main() {
+		r := mux.NewRouter()
+		r.HandleFunc("/signup", ShowSignupForm)
+		// All POST requests without a valid token will return HTTP 403 Forbidden.
+		// We should also ensure that our mutating (non-idempotent) handler only
+		// matches on POST requests. We can check that here, at the router level, or
+		// within the handler itself via r.Method.
+		r.HandleFunc("/signup/post", SubmitSignupForm).Methods("POST")
+
+		// Add the middleware to your router by wrapping it.
+		http.ListenAndServe(":8000",
+		csrf.Protect([]byte("32-byte-long-auth-key"))(r))
+		// PS: Don't forget to pass csrf.Secure(false) if you're developing locally
+		// over plain HTTP (just don't leave it on in production).
+	}
+
+	func ShowSignupForm(w http.ResponseWriter, r *http.Request) {
+		// signup_form.tmpl just needs a {{ .csrfField }} template tag for
+		// csrf.TemplateField to inject the CSRF token into. Easy!
+		t.ExecuteTemplate(w, "signup_form.tmpl", map[string]interface{}{
+			csrf.TemplateTag: csrf.TemplateField(r),
+		})
+	}
+
+	func SubmitSignupForm(w http.ResponseWriter, r *http.Request) {
+		// We can trust that requests making it this far have satisfied
+		// our CSRF protection requirements.
+		fmt.Fprintf(w, "%v\n", r.PostForm)
+	}
+
+Note that the CSRF middleware will (by necessity) consume the request body if the
+token is passed via POST form values. If you need to consume this in your
+handler, insert your own middleware earlier in the chain to capture the request
+body.
+
+You can also send the CSRF token in the response header. This approach is useful
+if you're using a front-end JavaScript framework like Ember or Angular, or are
+providing a JSON API:
+
+	package main
+
+	import (
+		"github.com/gorilla/csrf"
+		"github.com/gorilla/mux"
+	)
+
+	func main() {
+		r := mux.NewRouter()
+
+		api := r.PathPrefix("/api").Subrouter()
+		api.HandleFunc("/user/:id", GetUser).Methods("GET")
+
+		http.ListenAndServe(":8000",
+		csrf.Protect([]byte("32-byte-long-auth-key"))(r))
+	}
+
+	func GetUser(w http.ResponseWriter, r *http.Request) {
+		// Authenticate the request, get the id from the route params,
+		// and fetch the user from the DB, etc.
+
+		// Get the token and pass it in the CSRF header. Our JSON-speaking client
+		// or JavaScript framework can now read the header and return the token in
+		// in its own "X-CSRF-Token" request header on the subsequent POST.
+		w.Header().Set("X-CSRF-Token", csrf.Token(r))
+		b, err := json.Marshal(user)
+		if err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		w.Write(b)
+	}
+
+If you're writing a client that's supposed to mimic browser behavior, make sure to
+send back the CSRF cookie (the default name is _gorilla_csrf, but this can be changed
+with the CookieName Option) along with either the X-CSRF-Token header or the gorilla.csrf.Token form field.
+
+In addition: getting CSRF protection right is important, so here's some background:
+
+* This library generates unique-per-request (masked) tokens as a mitigation
+against the BREACH attack (http://breachattack.com/).
+
+* The 'base' (unmasked) token is stored in the session, which means that
+multiple browser tabs won't cause a user problems as their per-request token
+is compared with the base token.
+
+* Operates on a "whitelist only" approach where safe (non-mutating) HTTP methods
+(GET, HEAD, OPTIONS, TRACE) are the *only* methods where token validation is not
+enforced.
+
+* The design is based on the battle-tested Django
+(https://docs.djangoproject.com/en/1.8/ref/csrf/) and Ruby on Rails
+(http://api.rubyonrails.org/classes/ActionController/RequestForgeryProtection.html)
+approaches.
+
+* Cookies are authenticated and based on the securecookie
+(https://github.com/gorilla/securecookie) library. They're also Secure (issued
+over HTTPS only) and are HttpOnly by default, because sane defaults are
+important.
+
+* Go's `crypto/rand` library is used to generate the 32 byte (256 bit) tokens
+and the one-time-pad used for masking them.
+
+This library does not seek to be adventurous.
+
+*/
+package csrf
--- a/src/vendor/github.com/gorilla/csrf/go.mod
+++ b/src/vendor/github.com/gorilla/csrf/go.mod
@ -0,0 +1,6 @@
+module github.com/gorilla/csrf
+
+require (
+	github.com/gorilla/securecookie v1.1.1
+	github.com/pkg/errors v0.8.0
+)
--- a/src/vendor/github.com/gorilla/csrf/go.sum
+++ b/src/vendor/github.com/gorilla/csrf/go.sum
@ -0,0 +1,4 @@
+github.com/gorilla/securecookie v1.1.1 h1:miw7JPhV+b/lAHSXz4qd/nN9jRiAFV5FwjeKyCS8BvQ=
+github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+HVt/4epWDjd4=
+github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
+github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
--- a/src/vendor/github.com/gorilla/csrf/helpers.go
+++ b/src/vendor/github.com/gorilla/csrf/helpers.go
@ -0,0 +1,203 @@
+package csrf
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"fmt"
+	"html/template"
+	"net/http"
+	"net/url"
+)
+
+// Token returns a masked CSRF token ready for passing into HTML template or
+// a JSON response body. An empty token will be returned if the middleware
+// has not been applied (which will fail subsequent validation).
+func Token(r *http.Request) string {
+	if val, err := contextGet(r, tokenKey); err == nil {
+		if maskedToken, ok := val.(string); ok {
+			return maskedToken
+		}
+	}
+
+	return ""
+}
+
+// FailureReason makes CSRF validation errors available in the request context.
+// This is useful when you want to log the cause of the error or report it to
+// client.
+func FailureReason(r *http.Request) error {
+	if val, err := contextGet(r, errorKey); err == nil {
+		if err, ok := val.(error); ok {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// UnsafeSkipCheck will skip the CSRF check for any requests.  This must be
+// called before the CSRF middleware.
+//
+// Note: You should not set this without otherwise securing the request from
+// CSRF attacks. The primary use-case for this function is to turn off CSRF
+// checks for non-browser clients using authorization tokens against your API.
+func UnsafeSkipCheck(r *http.Request) *http.Request {
+	return contextSave(r, skipCheckKey, true)
+}
+
+// TemplateField is a template helper for html/template that provides an <input> field
+// populated with a CSRF token.
+//
+// Example:
+//
+//      // The following tag in our form.tmpl template:
+//      {{ .csrfField }}
+//
+//      // ... becomes:
+//      <input type="hidden" name="gorilla.csrf.Token" value="<token>">
+//
+func TemplateField(r *http.Request) template.HTML {
+	if name, err := contextGet(r, formKey); err == nil {
+		fragment := fmt.Sprintf(`<input type="hidden" name="%s" value="%s">`,
+			name, Token(r))
+
+		return template.HTML(fragment)
+	}
+
+	return template.HTML("")
+}
+
+// mask returns a unique-per-request token to mitigate the BREACH attack
+// as per http://breachattack.com/#mitigations
+//
+// The token is generated by XOR'ing a one-time-pad and the base (session) CSRF
+// token and returning them together as a 64-byte slice. This effectively
+// randomises the token on a per-request basis without breaking multiple browser
+// tabs/windows.
+func mask(realToken []byte, r *http.Request) string {
+	otp, err := generateRandomBytes(tokenLength)
+	if err != nil {
+		return ""
+	}
+
+	// XOR the OTP with the real token to generate a masked token. Append the
+	// OTP to the front of the masked token to allow unmasking in the subsequent
+	// request.
+	return base64.StdEncoding.EncodeToString(append(otp, xorToken(otp, realToken)...))
+}
+
+// unmask splits the issued token (one-time-pad + masked token) and returns the
+// unmasked request token for comparison.
+func unmask(issued []byte) []byte {
+	// Issued tokens are always masked and combined with the pad.
+	if len(issued) != tokenLength*2 {
+		return nil
+	}
+
+	// We now know the length of the byte slice.
+	otp := issued[tokenLength:]
+	masked := issued[:tokenLength]
+
+	// Unmask the token by XOR'ing it against the OTP used to mask it.
+	return xorToken(otp, masked)
+}
+
+// requestToken returns the issued token (pad + masked token) from the HTTP POST
+// body or HTTP header. It will return nil if the token fails to decode.
+func (cs *csrf) requestToken(r *http.Request) []byte {
+	// 1. Check the HTTP header first.
+	issued := r.Header.Get(cs.opts.RequestHeader)
+
+	// 2. Fall back to the POST (form) value.
+	if issued == "" {
+		issued = r.PostFormValue(cs.opts.FieldName)
+	}
+
+	// 3. Finally, fall back to the multipart form (if set).
+	if issued == "" && r.MultipartForm != nil {
+		vals := r.MultipartForm.Value[cs.opts.FieldName]
+
+		if len(vals) > 0 {
+			issued = vals[0]
+		}
+	}
+
+	// Decode the "issued" (pad + masked) token sent in the request. Return a
+	// nil byte slice on a decoding error (this will fail upstream).
+	decoded, err := base64.StdEncoding.DecodeString(issued)
+	if err != nil {
+		return nil
+	}
+
+	return decoded
+}
+
+// generateRandomBytes returns securely generated random bytes.
+// It will return an error if the system's secure random number generator
+// fails to function correctly.
+func generateRandomBytes(n int) ([]byte, error) {
+	b := make([]byte, n)
+	_, err := rand.Read(b)
+	// err == nil only if len(b) == n
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+
+}
+
+// sameOrigin returns true if URLs a and b share the same origin. The same
+// origin is defined as host (which includes the port) and scheme.
+func sameOrigin(a, b *url.URL) bool {
+	return (a.Scheme == b.Scheme && a.Host == b.Host)
+}
+
+// compare securely (constant-time) compares the unmasked token from the request
+// against the real token from the session.
+func compareTokens(a, b []byte) bool {
+	// This is required as subtle.ConstantTimeCompare does not check for equal
+	// lengths in Go versions prior to 1.3.
+	if len(a) != len(b) {
+		return false
+	}
+
+	return subtle.ConstantTimeCompare(a, b) == 1
+}
+
+// xorToken XORs tokens ([]byte) to provide unique-per-request CSRF tokens. It
+// will return a masked token if the base token is XOR'ed with a one-time-pad.
+// An unmasked token will be returned if a masked token is XOR'ed with the
+// one-time-pad used to mask it.
+func xorToken(a, b []byte) []byte {
+	n := len(a)
+	if len(b) < n {
+		n = len(b)
+	}
+
+	res := make([]byte, n)
+
+	for i := 0; i < n; i++ {
+		res[i] = a[i] ^ b[i]
+	}
+
+	return res
+}
+
+// contains is a helper function to check if a string exists in a slice - e.g.
+// whether a HTTP method exists in a list of safe methods.
+func contains(vals []string, s string) bool {
+	for _, v := range vals {
+		if v == s {
+			return true
+		}
+	}
+
+	return false
+}
+
+// envError stores a CSRF error in the request context.
+func envError(r *http.Request, err error) *http.Request {
+	return contextSave(r, errorKey, err)
+}
--- a/src/vendor/github.com/gorilla/csrf/options.go
+++ b/src/vendor/github.com/gorilla/csrf/options.go
@ -0,0 +1,170 @@
+package csrf
+
+import (
+	"net/http"
+)
+
+// Option describes a functional option for configuring the CSRF handler.
+type Option func(*csrf)
+
+// MaxAge sets the maximum age (in seconds) of a CSRF token's underlying cookie.
+// Defaults to 12 hours. Call csrf.MaxAge(0) to explicitly set session-only
+// cookies.
+func MaxAge(age int) Option {
+	return func(cs *csrf) {
+		cs.opts.MaxAge = age
+	}
+}
+
+// Domain sets the cookie domain. Defaults to the current domain of the request
+// only (recommended).
+//
+// This should be a hostname and not a URL. If set, the domain is treated as
+// being prefixed with a '.' - e.g. "example.com" becomes ".example.com" and
+// matches "www.example.com" and "secure.example.com".
+func Domain(domain string) Option {
+	return func(cs *csrf) {
+		cs.opts.Domain = domain
+	}
+}
+
+// Path sets the cookie path. Defaults to the path the cookie was issued from
+// (recommended).
+//
+// This instructs clients to only respond with cookie for that path and its
+// subpaths - i.e. a cookie issued from "/register" would be included in requests
+// to "/register/step2" and "/register/submit".
+func Path(p string) Option {
+	return func(cs *csrf) {
+		cs.opts.Path = p
+	}
+}
+
+// Secure sets the 'Secure' flag on the cookie. Defaults to true (recommended).
+// Set this to 'false' in your development environment otherwise the cookie won't
+// be sent over an insecure channel. Setting this via the presence of a 'DEV'
+// environmental variable is a good way of making sure this won't make it to a
+// production environment.
+func Secure(s bool) Option {
+	return func(cs *csrf) {
+		cs.opts.Secure = s
+	}
+}
+
+// HttpOnly sets the 'HttpOnly' flag on the cookie. Defaults to true (recommended).
+func HttpOnly(h bool) Option {
+	return func(cs *csrf) {
+		// Note that the function and field names match the case of the
+		// related http.Cookie field instead of the "correct" HTTPOnly name
+		// that golint suggests.
+		cs.opts.HttpOnly = h
+	}
+}
+
+// SameSite sets the cookie SameSite attribute. Defaults to blank to maintain
+// backwards compatibility, however, Strict is recommended.
+//
+// SameSite(SameSiteStrictMode) will prevent the cookie from being sent by the
+// browser to the target site in all cross-site browsing context, even when
+// following a regular link (GET request).
+//
+// SameSite(SameSiteLaxMode) provides a reasonable balance between security and
+// usability for websites that want to maintain user's logged-in session after
+// the user arrives from an external link. The session cookie would be allowed
+// when following a regular link from an external website while blocking it in
+// CSRF-prone request methods (e.g. POST).
+//
+// This option is only available for go 1.11+.
+func SameSite(s SameSiteMode) Option {
+	return func(cs *csrf) {
+		cs.opts.SameSite = s
+	}
+}
+
+// ErrorHandler allows you to change the handler called when CSRF request
+// processing encounters an invalid token or request. A typical use would be to
+// provide a handler that returns a static HTML file with a HTTP 403 status. By
+// default a HTTP 403 status and a plain text CSRF failure reason are served.
+//
+// Note that a custom error handler can also access the csrf.FailureReason(r)
+// function to retrieve the CSRF validation reason from the request context.
+func ErrorHandler(h http.Handler) Option {
+	return func(cs *csrf) {
+		cs.opts.ErrorHandler = h
+	}
+}
+
+// RequestHeader allows you to change the request header the CSRF middleware
+// inspects. The default is X-CSRF-Token.
+func RequestHeader(header string) Option {
+	return func(cs *csrf) {
+		cs.opts.RequestHeader = header
+	}
+}
+
+// FieldName allows you to change the name attribute of the hidden <input> field
+// inspected by this package. The default is 'gorilla.csrf.Token'.
+func FieldName(name string) Option {
+	return func(cs *csrf) {
+		cs.opts.FieldName = name
+	}
+}
+
+// CookieName changes the name of the CSRF cookie issued to clients.
+//
+// Note that cookie names should not contain whitespace, commas, semicolons,
+// backslashes or control characters as per RFC6265.
+func CookieName(name string) Option {
+	return func(cs *csrf) {
+		cs.opts.CookieName = name
+	}
+}
+
+// TrustedOrigins configures a set of origins (Referers) that are considered as trusted.
+// This will allow cross-domain CSRF use-cases - e.g. where the front-end is served
+// from a different domain than the API server - to correctly pass a CSRF check.
+//
+// You should only provide origins you own or have full control over.
+func TrustedOrigins(origins []string) Option {
+	return func(cs *csrf) {
+		cs.opts.TrustedOrigins = origins
+	}
+}
+
+// setStore sets the store used by the CSRF middleware.
+// Note: this is private (for now) to allow for internal API changes.
+func setStore(s store) Option {
+	return func(cs *csrf) {
+		cs.st = s
+	}
+}
+
+// parseOptions parses the supplied options functions and returns a configured
+// csrf handler.
+func parseOptions(h http.Handler, opts ...Option) *csrf {
+	// Set the handler to call after processing.
+	cs := &csrf{
+		h: h,
+	}
+
+	// Default to true. See Secure & HttpOnly function comments for rationale.
+	// Set here to allow package users to override the default.
+	cs.opts.Secure = true
+	cs.opts.HttpOnly = true
+
+	// Default to blank to maintain backwards compatibility
+	cs.opts.SameSite = SameSiteDefaultMode
+
+	// Default; only override this if the package user explicitly calls MaxAge(0)
+	cs.opts.MaxAge = defaultAge
+
+	// Range over each options function and apply it
+	// to our csrf type to configure it. Options functions are
+	// applied in order, with any conflicting options overriding
+	// earlier calls.
+	for _, option := range opts {
+		option(cs)
+	}
+
+	return cs
+}
--- a/src/vendor/github.com/gorilla/csrf/store.go
+++ b/src/vendor/github.com/gorilla/csrf/store.go
@ -0,0 +1,86 @@
+// +build go1.11
+
+package csrf
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gorilla/securecookie"
+)
+
+// store represents the session storage used for CSRF tokens.
+type store interface {
+	// Get returns the real CSRF token from the store.
+	Get(*http.Request) ([]byte, error)
+	// Save stores the real CSRF token in the store and writes a
+	// cookie to the http.ResponseWriter.
+	// For non-cookie stores, the cookie should contain a unique (256 bit) ID
+	// or key that references the token in the backend store.
+	// csrf.GenerateRandomBytes is a helper function for generating secure IDs.
+	Save(token []byte, w http.ResponseWriter) error
+}
+
+// cookieStore is a signed cookie session store for CSRF tokens.
+type cookieStore struct {
+	name     string
+	maxAge   int
+	secure   bool
+	httpOnly bool
+	path     string
+	domain   string
+	sc       *securecookie.SecureCookie
+	sameSite SameSiteMode
+}
+
+// Get retrieves a CSRF token from the session cookie. It returns an empty token
+// if decoding fails (e.g. HMAC validation fails or the named cookie doesn't exist).
+func (cs *cookieStore) Get(r *http.Request) ([]byte, error) {
+	// Retrieve the cookie from the request
+	cookie, err := r.Cookie(cs.name)
+	if err != nil {
+		return nil, err
+	}
+
+	token := make([]byte, tokenLength)
+	// Decode the HMAC authenticated cookie.
+	err = cs.sc.Decode(cs.name, cookie.Value, &token)
+	if err != nil {
+		return nil, err
+	}
+
+	return token, nil
+}
+
+// Save stores the CSRF token in the session cookie.
+func (cs *cookieStore) Save(token []byte, w http.ResponseWriter) error {
+	// Generate an encoded cookie value with the CSRF token.
+	encoded, err := cs.sc.Encode(cs.name, token)
+	if err != nil {
+		return err
+	}
+
+	cookie := &http.Cookie{
+		Name:     cs.name,
+		Value:    encoded,
+		MaxAge:   cs.maxAge,
+		HttpOnly: cs.httpOnly,
+		Secure:   cs.secure,
+		SameSite: http.SameSite(cs.sameSite),
+		Path:     cs.path,
+		Domain:   cs.domain,
+	}
+
+	// Set the Expires field on the cookie based on the MaxAge
+	// If MaxAge <= 0, we don't set the Expires attribute, making the cookie
+	// session-only.
+	if cs.maxAge > 0 {
+		cookie.Expires = time.Now().Add(
+			time.Duration(cs.maxAge) * time.Second)
+	}
+
+	// Write the authenticated cookie to the response.
+	http.SetCookie(w, cookie)
+
+	return nil
+}
--- a/src/vendor/github.com/gorilla/csrf/store_legacy.go
+++ b/src/vendor/github.com/gorilla/csrf/store_legacy.go
@ -0,0 +1,86 @@
+// +build !go1.11
+// file for compatibility with go versions prior to 1.11
+
+package csrf
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gorilla/securecookie"
+)
+
+// store represents the session storage used for CSRF tokens.
+type store interface {
+	// Get returns the real CSRF token from the store.
+	Get(*http.Request) ([]byte, error)
+	// Save stores the real CSRF token in the store and writes a
+	// cookie to the http.ResponseWriter.
+	// For non-cookie stores, the cookie should contain a unique (256 bit) ID
+	// or key that references the token in the backend store.
+	// csrf.GenerateRandomBytes is a helper function for generating secure IDs.
+	Save(token []byte, w http.ResponseWriter) error
+}
+
+// cookieStore is a signed cookie session store for CSRF tokens.
+type cookieStore struct {
+	name     string
+	maxAge   int
+	secure   bool
+	httpOnly bool
+	path     string
+	domain   string
+	sc       *securecookie.SecureCookie
+	sameSite SameSiteMode
+}
+
+// Get retrieves a CSRF token from the session cookie. It returns an empty token
+// if decoding fails (e.g. HMAC validation fails or the named cookie doesn't exist).
+func (cs *cookieStore) Get(r *http.Request) ([]byte, error) {
+	// Retrieve the cookie from the request
+	cookie, err := r.Cookie(cs.name)
+	if err != nil {
+		return nil, err
+	}
+
+	token := make([]byte, tokenLength)
+	// Decode the HMAC authenticated cookie.
+	err = cs.sc.Decode(cs.name, cookie.Value, &token)
+	if err != nil {
+		return nil, err
+	}
+
+	return token, nil
+}
+
+// Save stores the CSRF token in the session cookie.
+func (cs *cookieStore) Save(token []byte, w http.ResponseWriter) error {
+	// Generate an encoded cookie value with the CSRF token.
+	encoded, err := cs.sc.Encode(cs.name, token)
+	if err != nil {
+		return err
+	}
+
+	cookie := &http.Cookie{
+		Name:     cs.name,
+		Value:    encoded,
+		MaxAge:   cs.maxAge,
+		HttpOnly: cs.httpOnly,
+		Secure:   cs.secure,
+		Path:     cs.path,
+		Domain:   cs.domain,
+	}
+
+	// Set the Expires field on the cookie based on the MaxAge
+	// If MaxAge <= 0, we don't set the Expires attribute, making the cookie
+	// session-only.
+	if cs.maxAge > 0 {
+		cookie.Expires = time.Now().Add(
+			time.Duration(cs.maxAge) * time.Second)
+	}
+
+	// Write the authenticated cookie to the response.
+	http.SetCookie(w, cookie)
+
+	return nil
+}
--- a/src/vendor/github.com/gorilla/securecookie/.travis.yml
+++ b/src/vendor/github.com/gorilla/securecookie/.travis.yml
@ -0,0 +1,19 @@
+language: go
+sudo: false
+
+matrix:
+  include:
+    - go: 1.3
+    - go: 1.4
+    - go: 1.5
+    - go: 1.6
+    - go: 1.7
+    - go: tip
+  allow_failures:
+    - go: tip
+
+script:
+  - go get -t -v ./...
+  - diff -u <(echo -n) <(gofmt -d .)
+  - go vet $(go list ./... | grep -v /vendor/)
+  - go test -v -race ./...
--- a/src/vendor/github.com/gorilla/securecookie/LICENSE
+++ b/src/vendor/github.com/gorilla/securecookie/LICENSE
@ -0,0 +1,27 @@
+Copyright (c) 2012 Rodrigo Moraes. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+	 * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+	 * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+	 * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--- a/src/vendor/github.com/gorilla/securecookie/README.md
+++ b/src/vendor/github.com/gorilla/securecookie/README.md
@ -0,0 +1,80 @@
+securecookie
+============
+[![GoDoc](https://godoc.org/github.com/gorilla/securecookie?status.svg)](https://godoc.org/github.com/gorilla/securecookie) [![Build Status](https://travis-ci.org/gorilla/securecookie.png?branch=master)](https://travis-ci.org/gorilla/securecookie)
+[![Sourcegraph](https://sourcegraph.com/github.com/gorilla/securecookie/-/badge.svg)](https://sourcegraph.com/github.com/gorilla/securecookie?badge)
+
+
+securecookie encodes and decodes authenticated and optionally encrypted 
+cookie values.
+
+Secure cookies can't be forged, because their values are validated using HMAC.
+When encrypted, the content is also inaccessible to malicious eyes. It is still
+recommended that sensitive data not be stored in cookies, and that HTTPS be used
+to prevent cookie [replay attacks](https://en.wikipedia.org/wiki/Replay_attack).
+
+## Examples
+
+To use it, first create a new SecureCookie instance:
+
+```go
+// Hash keys should be at least 32 bytes long
+var hashKey = []byte("very-secret")
+// Block keys should be 16 bytes (AES-128) or 32 bytes (AES-256) long.
+// Shorter keys may weaken the encryption used.
+var blockKey = []byte("a-lot-secret")
+var s = securecookie.New(hashKey, blockKey)
+```
+
+The hashKey is required, used to authenticate the cookie value using HMAC.
+It is recommended to use a key with 32 or 64 bytes.
+
+The blockKey is optional, used to encrypt the cookie value -- set it to nil
+to not use encryption. If set, the length must correspond to the block size
+of the encryption algorithm. For AES, used by default, valid lengths are
+16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
+
+Strong keys can be created using the convenience function GenerateRandomKey().
+
+Once a SecureCookie instance is set, use it to encode a cookie value:
+
+```go
+func SetCookieHandler(w http.ResponseWriter, r *http.Request) {
+	value := map[string]string{
+		"foo": "bar",
+	}
+	if encoded, err := s.Encode("cookie-name", value); err == nil {
+		cookie := &http.Cookie{
+			Name:  "cookie-name",
+			Value: encoded,
+			Path:  "/",
+			Secure: true,
+			HttpOnly: true,
+		}
+		http.SetCookie(w, cookie)
+	}
+}
+```
+
+Later, use the same SecureCookie instance to decode and validate a cookie
+value:
+
+```go
+func ReadCookieHandler(w http.ResponseWriter, r *http.Request) {
+	if cookie, err := r.Cookie("cookie-name"); err == nil {
+		value := make(map[string]string)
+		if err = s2.Decode("cookie-name", cookie.Value, &value); err == nil {
+			fmt.Fprintf(w, "The value of foo is %q", value["foo"])
+		}
+	}
+}
+```
+
+We stored a map[string]string, but secure cookies can hold any value that
+can be encoded using `encoding/gob`. To store custom types, they must be
+registered first using gob.Register(). For basic types this is not needed;
+it works out of the box. An optional JSON encoder that uses `encoding/json` is
+available for types compatible with JSON.
+
+## License
+
+BSD licensed. See the LICENSE file for details.
--- a/src/vendor/github.com/gorilla/securecookie/doc.go
+++ b/src/vendor/github.com/gorilla/securecookie/doc.go
@ -0,0 +1,61 @@
+// Copyright 2012 The Gorilla Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package securecookie encodes and decodes authenticated and optionally
+encrypted cookie values.
+
+Secure cookies can't be forged, because their values are validated using HMAC.
+When encrypted, the content is also inaccessible to malicious eyes.
+
+To use it, first create a new SecureCookie instance:
+
+	var hashKey = []byte("very-secret")
+	var blockKey = []byte("a-lot-secret")
+	var s = securecookie.New(hashKey, blockKey)
+
+The hashKey is required, used to authenticate the cookie value using HMAC.
+It is recommended to use a key with 32 or 64 bytes.
+
+The blockKey is optional, used to encrypt the cookie value -- set it to nil
+to not use encryption. If set, the length must correspond to the block size
+of the encryption algorithm. For AES, used by default, valid lengths are
+16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
+
+Strong keys can be created using the convenience function GenerateRandomKey().
+
+Once a SecureCookie instance is set, use it to encode a cookie value:
+
+	func SetCookieHandler(w http.ResponseWriter, r *http.Request) {
+		value := map[string]string{
+			"foo": "bar",
+		}
+		if encoded, err := s.Encode("cookie-name", value); err == nil {
+			cookie := &http.Cookie{
+				Name:  "cookie-name",
+				Value: encoded,
+				Path:  "/",
+			}
+			http.SetCookie(w, cookie)
+		}
+	}
+
+Later, use the same SecureCookie instance to decode and validate a cookie
+value:
+
+	func ReadCookieHandler(w http.ResponseWriter, r *http.Request) {
+		if cookie, err := r.Cookie("cookie-name"); err == nil {
+			value := make(map[string]string)
+			if err = s2.Decode("cookie-name", cookie.Value, &value); err == nil {
+				fmt.Fprintf(w, "The value of foo is %q", value["foo"])
+			}
+		}
+	}
+
+We stored a map[string]string, but secure cookies can hold any value that
+can be encoded using encoding/gob. To store custom types, they must be
+registered first using gob.Register(). For basic types this is not needed;
+it works out of the box.
+*/
+package securecookie
--- a/src/vendor/github.com/gorilla/securecookie/fuzz.go
+++ b/src/vendor/github.com/gorilla/securecookie/fuzz.go
@ -0,0 +1,25 @@
+// +build gofuzz
+
+package securecookie
+
+var hashKey = []byte("very-secret12345")
+var blockKey = []byte("a-lot-secret1234")
+var s = New(hashKey, blockKey)
+
+type Cookie struct {
+	B bool
+	I int
+	S string
+}
+
+func Fuzz(data []byte) int {
+	datas := string(data)
+	var c Cookie
+	if err := s.Decode("fuzz", datas, &c); err != nil {
+		return 0
+	}
+	if _, err := s.Encode("fuzz", c); err != nil {
+		panic(err)
+	}
+	return 1
+}
--- a/src/vendor/github.com/gorilla/securecookie/securecookie.go
+++ b/src/vendor/github.com/gorilla/securecookie/securecookie.go
@ -0,0 +1,646 @@
+// Copyright 2012 The Gorilla Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securecookie
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/subtle"
+	"encoding/base64"
+	"encoding/gob"
+	"encoding/json"
+	"fmt"
+	"hash"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Error is the interface of all errors returned by functions in this library.
+type Error interface {
+	error
+
+	// IsUsage returns true for errors indicating the client code probably
+	// uses this library incorrectly.  For example, the client may have
+	// failed to provide a valid hash key, or may have failed to configure
+	// the Serializer adequately for encoding value.
+	IsUsage() bool
+
+	// IsDecode returns true for errors indicating that a cookie could not
+	// be decoded and validated.  Since cookies are usually untrusted
+	// user-provided input, errors of this type should be expected.
+	// Usually, the proper action is simply to reject the request.
+	IsDecode() bool
+
+	// IsInternal returns true for unexpected errors occurring in the
+	// securecookie implementation.
+	IsInternal() bool
+
+	// Cause, if it returns a non-nil value, indicates that this error was
+	// propagated from some underlying library.  If this method returns nil,
+	// this error was raised directly by this library.
+	//
+	// Cause is provided principally for debugging/logging purposes; it is
+	// rare that application logic should perform meaningfully different
+	// logic based on Cause.  See, for example, the caveats described on
+	// (MultiError).Cause().
+	Cause() error
+}
+
+// errorType is a bitmask giving the error type(s) of an cookieError value.
+type errorType int
+
+const (
+	usageError = errorType(1 << iota)
+	decodeError
+	internalError
+)
+
+type cookieError struct {
+	typ   errorType
+	msg   string
+	cause error
+}
+
+func (e cookieError) IsUsage() bool    { return (e.typ & usageError) != 0 }
+func (e cookieError) IsDecode() bool   { return (e.typ & decodeError) != 0 }
+func (e cookieError) IsInternal() bool { return (e.typ & internalError) != 0 }
+
+func (e cookieError) Cause() error { return e.cause }
+
+func (e cookieError) Error() string {
+	parts := []string{"securecookie: "}
+	if e.msg == "" {
+		parts = append(parts, "error")
+	} else {
+		parts = append(parts, e.msg)
+	}
+	if c := e.Cause(); c != nil {
+		parts = append(parts, " - caused by: ", c.Error())
+	}
+	return strings.Join(parts, "")
+}
+
+var (
+	errGeneratingIV = cookieError{typ: internalError, msg: "failed to generate random iv"}
+
+	errNoCodecs            = cookieError{typ: usageError, msg: "no codecs provided"}
+	errHashKeyNotSet       = cookieError{typ: usageError, msg: "hash key is not set"}
+	errBlockKeyNotSet      = cookieError{typ: usageError, msg: "block key is not set"}
+	errEncodedValueTooLong = cookieError{typ: usageError, msg: "the value is too long"}
+
+	errValueToDecodeTooLong = cookieError{typ: decodeError, msg: "the value is too long"}
+	errTimestampInvalid     = cookieError{typ: decodeError, msg: "invalid timestamp"}
+	errTimestampTooNew      = cookieError{typ: decodeError, msg: "timestamp is too new"}
+	errTimestampExpired     = cookieError{typ: decodeError, msg: "expired timestamp"}
+	errDecryptionFailed     = cookieError{typ: decodeError, msg: "the value could not be decrypted"}
+	errValueNotByte         = cookieError{typ: decodeError, msg: "value not a []byte."}
+	errValueNotBytePtr      = cookieError{typ: decodeError, msg: "value not a pointer to []byte."}
+
+	// ErrMacInvalid indicates that cookie decoding failed because the HMAC
+	// could not be extracted and verified.  Direct use of this error
+	// variable is deprecated; it is public only for legacy compatibility,
+	// and may be privatized in the future, as it is rarely useful to
+	// distinguish between this error and other Error implementations.
+	ErrMacInvalid = cookieError{typ: decodeError, msg: "the value is not valid"}
+)
+
+// Codec defines an interface to encode and decode cookie values.
+type Codec interface {
+	Encode(name string, value interface{}) (string, error)
+	Decode(name, value string, dst interface{}) error
+}
+
+// New returns a new SecureCookie.
+//
+// hashKey is required, used to authenticate values using HMAC. Create it using
+// GenerateRandomKey(). It is recommended to use a key with 32 or 64 bytes.
+//
+// blockKey is optional, used to encrypt values. Create it using
+// GenerateRandomKey(). The key length must correspond to the block size
+// of the encryption algorithm. For AES, used by default, valid lengths are
+// 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
+// The default encoder used for cookie serialization is encoding/gob.
+//
+// Note that keys created using GenerateRandomKey() are not automatically
+// persisted. New keys will be created when the application is restarted, and
+// previously issued cookies will not be able to be decoded.
+func New(hashKey, blockKey []byte) *SecureCookie {
+	s := &SecureCookie{
+		hashKey:   hashKey,
+		blockKey:  blockKey,
+		hashFunc:  sha256.New,
+		maxAge:    86400 * 30,
+		maxLength: 4096,
+		sz:        GobEncoder{},
+	}
+	if hashKey == nil {
+		s.err = errHashKeyNotSet
+	}
+	if blockKey != nil {
+		s.BlockFunc(aes.NewCipher)
+	}
+	return s
+}
+
+// SecureCookie encodes and decodes authenticated and optionally encrypted
+// cookie values.
+type SecureCookie struct {
+	hashKey   []byte
+	hashFunc  func() hash.Hash
+	blockKey  []byte
+	block     cipher.Block
+	maxLength int
+	maxAge    int64
+	minAge    int64
+	err       error
+	sz        Serializer
+	// For testing purposes, the function that returns the current timestamp.
+	// If not set, it will use time.Now().UTC().Unix().
+	timeFunc func() int64
+}
+
+// Serializer provides an interface for providing custom serializers for cookie
+// values.
+type Serializer interface {
+	Serialize(src interface{}) ([]byte, error)
+	Deserialize(src []byte, dst interface{}) error
+}
+
+// GobEncoder encodes cookie values using encoding/gob. This is the simplest
+// encoder and can handle complex types via gob.Register.
+type GobEncoder struct{}
+
+// JSONEncoder encodes cookie values using encoding/json. Users who wish to
+// encode complex types need to satisfy the json.Marshaller and
+// json.Unmarshaller interfaces.
+type JSONEncoder struct{}
+
+// NopEncoder does not encode cookie values, and instead simply accepts a []byte
+// (as an interface{}) and returns a []byte. This is particularly useful when
+// you encoding an object upstream and do not wish to re-encode it.
+type NopEncoder struct{}
+
+// MaxLength restricts the maximum length, in bytes, for the cookie value.
+//
+// Default is 4096, which is the maximum value accepted by Internet Explorer.
+func (s *SecureCookie) MaxLength(value int) *SecureCookie {
+	s.maxLength = value
+	return s
+}
+
+// MaxAge restricts the maximum age, in seconds, for the cookie value.
+//
+// Default is 86400 * 30. Set it to 0 for no restriction.
+func (s *SecureCookie) MaxAge(value int) *SecureCookie {
+	s.maxAge = int64(value)
+	return s
+}
+
+// MinAge restricts the minimum age, in seconds, for the cookie value.
+//
+// Default is 0 (no restriction).
+func (s *SecureCookie) MinAge(value int) *SecureCookie {
+	s.minAge = int64(value)
+	return s
+}
+
+// HashFunc sets the hash function used to create HMAC.
+//
+// Default is crypto/sha256.New.
+func (s *SecureCookie) HashFunc(f func() hash.Hash) *SecureCookie {
+	s.hashFunc = f
+	return s
+}
+
+// BlockFunc sets the encryption function used to create a cipher.Block.
+//
+// Default is crypto/aes.New.
+func (s *SecureCookie) BlockFunc(f func([]byte) (cipher.Block, error)) *SecureCookie {
+	if s.blockKey == nil {
+		s.err = errBlockKeyNotSet
+	} else if block, err := f(s.blockKey); err == nil {
+		s.block = block
+	} else {
+		s.err = cookieError{cause: err, typ: usageError}
+	}
+	return s
+}
+
+// Encoding sets the encoding/serialization method for cookies.
+//
+// Default is encoding/gob.  To encode special structures using encoding/gob,
+// they must be registered first using gob.Register().
+func (s *SecureCookie) SetSerializer(sz Serializer) *SecureCookie {
+	s.sz = sz
+
+	return s
+}
+
+// Encode encodes a cookie value.
+//
+// It serializes, optionally encrypts, signs with a message authentication code,
+// and finally encodes the value.
+//
+// The name argument is the cookie name. It is stored with the encoded value.
+// The value argument is the value to be encoded. It can be any value that can
+// be encoded using the currently selected serializer; see SetSerializer().
+//
+// It is the client's responsibility to ensure that value, when encoded using
+// the current serialization/encryption settings on s and then base64-encoded,
+// is shorter than the maximum permissible length.
+func (s *SecureCookie) Encode(name string, value interface{}) (string, error) {
+	if s.err != nil {
+		return "", s.err
+	}
+	if s.hashKey == nil {
+		s.err = errHashKeyNotSet
+		return "", s.err
+	}
+	var err error
+	var b []byte
+	// 1. Serialize.
+	if b, err = s.sz.Serialize(value); err != nil {
+		return "", cookieError{cause: err, typ: usageError}
+	}
+	// 2. Encrypt (optional).
+	if s.block != nil {
+		if b, err = encrypt(s.block, b); err != nil {
+			return "", cookieError{cause: err, typ: usageError}
+		}
+	}
+	b = encode(b)
+	// 3. Create MAC for "name|date|value". Extra pipe to be used later.
+	b = []byte(fmt.Sprintf("%s|%d|%s|", name, s.timestamp(), b))
+	mac := createMac(hmac.New(s.hashFunc, s.hashKey), b[:len(b)-1])
+	// Append mac, remove name.
+	b = append(b, mac...)[len(name)+1:]
+	// 4. Encode to base64.
+	b = encode(b)
+	// 5. Check length.
+	if s.maxLength != 0 && len(b) > s.maxLength {
+		return "", errEncodedValueTooLong
+	}
+	// Done.
+	return string(b), nil
+}
+
+// Decode decodes a cookie value.
+//
+// It decodes, verifies a message authentication code, optionally decrypts and
+// finally deserializes the value.
+//
+// The name argument is the cookie name. It must be the same name used when
+// it was stored. The value argument is the encoded cookie value. The dst
+// argument is where the cookie will be decoded. It must be a pointer.
+func (s *SecureCookie) Decode(name, value string, dst interface{}) error {
+	if s.err != nil {
+		return s.err
+	}
+	if s.hashKey == nil {
+		s.err = errHashKeyNotSet
+		return s.err
+	}
+	// 1. Check length.
+	if s.maxLength != 0 && len(value) > s.maxLength {
+		return errValueToDecodeTooLong
+	}
+	// 2. Decode from base64.
+	b, err := decode([]byte(value))
+	if err != nil {
+		return err
+	}
+	// 3. Verify MAC. Value is "date|value|mac".
+	parts := bytes.SplitN(b, []byte("|"), 3)
+	if len(parts) != 3 {
+		return ErrMacInvalid
+	}
+	h := hmac.New(s.hashFunc, s.hashKey)
+	b = append([]byte(name+"|"), b[:len(b)-len(parts[2])-1]...)
+	if err = verifyMac(h, b, parts[2]); err != nil {
+		return err
+	}
+	// 4. Verify date ranges.
+	var t1 int64
+	if t1, err = strconv.ParseInt(string(parts[0]), 10, 64); err != nil {
+		return errTimestampInvalid
+	}
+	t2 := s.timestamp()
+	if s.minAge != 0 && t1 > t2-s.minAge {
+		return errTimestampTooNew
+	}
+	if s.maxAge != 0 && t1 < t2-s.maxAge {
+		return errTimestampExpired
+	}
+	// 5. Decrypt (optional).
+	b, err = decode(parts[1])
+	if err != nil {
+		return err
+	}
+	if s.block != nil {
+		if b, err = decrypt(s.block, b); err != nil {
+			return err
+		}
+	}
+	// 6. Deserialize.
+	if err = s.sz.Deserialize(b, dst); err != nil {
+		return cookieError{cause: err, typ: decodeError}
+	}
+	// Done.
+	return nil
+}
+
+// timestamp returns the current timestamp, in seconds.
+//
+// For testing purposes, the function that generates the timestamp can be
+// overridden. If not set, it will return time.Now().UTC().Unix().
+func (s *SecureCookie) timestamp() int64 {
+	if s.timeFunc == nil {
+		return time.Now().UTC().Unix()
+	}
+	return s.timeFunc()
+}
+
+// Authentication -------------------------------------------------------------
+
+// createMac creates a message authentication code (MAC).
+func createMac(h hash.Hash, value []byte) []byte {
+	h.Write(value)
+	return h.Sum(nil)
+}
+
+// verifyMac verifies that a message authentication code (MAC) is valid.
+func verifyMac(h hash.Hash, value []byte, mac []byte) error {
+	mac2 := createMac(h, value)
+	// Check that both MACs are of equal length, as subtle.ConstantTimeCompare
+	// does not do this prior to Go 1.4.
+	if len(mac) == len(mac2) && subtle.ConstantTimeCompare(mac, mac2) == 1 {
+		return nil
+	}
+	return ErrMacInvalid
+}
+
+// Encryption -----------------------------------------------------------------
+
+// encrypt encrypts a value using the given block in counter mode.
+//
+// A random initialization vector (http://goo.gl/zF67k) with the length of the
+// block size is prepended to the resulting ciphertext.
+func encrypt(block cipher.Block, value []byte) ([]byte, error) {
+	iv := GenerateRandomKey(block.BlockSize())
+	if iv == nil {
+		return nil, errGeneratingIV
+	}
+	// Encrypt it.
+	stream := cipher.NewCTR(block, iv)
+	stream.XORKeyStream(value, value)
+	// Return iv + ciphertext.
+	return append(iv, value...), nil
+}
+
+// decrypt decrypts a value using the given block in counter mode.
+//
+// The value to be decrypted must be prepended by a initialization vector
+// (http://goo.gl/zF67k) with the length of the block size.
+func decrypt(block cipher.Block, value []byte) ([]byte, error) {
+	size := block.BlockSize()
+	if len(value) > size {
+		// Extract iv.
+		iv := value[:size]
+		// Extract ciphertext.
+		value = value[size:]
+		// Decrypt it.
+		stream := cipher.NewCTR(block, iv)
+		stream.XORKeyStream(value, value)
+		return value, nil
+	}
+	return nil, errDecryptionFailed
+}
+
+// Serialization --------------------------------------------------------------
+
+// Serialize encodes a value using gob.
+func (e GobEncoder) Serialize(src interface{}) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	enc := gob.NewEncoder(buf)
+	if err := enc.Encode(src); err != nil {
+		return nil, cookieError{cause: err, typ: usageError}
+	}
+	return buf.Bytes(), nil
+}
+
+// Deserialize decodes a value using gob.
+func (e GobEncoder) Deserialize(src []byte, dst interface{}) error {
+	dec := gob.NewDecoder(bytes.NewBuffer(src))
+	if err := dec.Decode(dst); err != nil {
+		return cookieError{cause: err, typ: decodeError}
+	}
+	return nil
+}
+
+// Serialize encodes a value using encoding/json.
+func (e JSONEncoder) Serialize(src interface{}) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	enc := json.NewEncoder(buf)
+	if err := enc.Encode(src); err != nil {
+		return nil, cookieError{cause: err, typ: usageError}
+	}
+	return buf.Bytes(), nil
+}
+
+// Deserialize decodes a value using encoding/json.
+func (e JSONEncoder) Deserialize(src []byte, dst interface{}) error {
+	dec := json.NewDecoder(bytes.NewReader(src))
+	if err := dec.Decode(dst); err != nil {
+		return cookieError{cause: err, typ: decodeError}
+	}
+	return nil
+}
+
+// Serialize passes a []byte through as-is.
+func (e NopEncoder) Serialize(src interface{}) ([]byte, error) {
+	if b, ok := src.([]byte); ok {
+		return b, nil
+	}
+
+	return nil, errValueNotByte
+}
+
+// Deserialize passes a []byte through as-is.
+func (e NopEncoder) Deserialize(src []byte, dst interface{}) error {
+	if dat, ok := dst.(*[]byte); ok {
+		*dat = src
+		return nil
+	}
+	return errValueNotBytePtr
+}
+
+// Encoding -------------------------------------------------------------------
+
+// encode encodes a value using base64.
+func encode(value []byte) []byte {
+	encoded := make([]byte, base64.URLEncoding.EncodedLen(len(value)))
+	base64.URLEncoding.Encode(encoded, value)
+	return encoded
+}
+
+// decode decodes a cookie using base64.
+func decode(value []byte) ([]byte, error) {
+	decoded := make([]byte, base64.URLEncoding.DecodedLen(len(value)))
+	b, err := base64.URLEncoding.Decode(decoded, value)
+	if err != nil {
+		return nil, cookieError{cause: err, typ: decodeError, msg: "base64 decode failed"}
+	}
+	return decoded[:b], nil
+}
+
+// Helpers --------------------------------------------------------------------
+
+// GenerateRandomKey creates a random key with the given length in bytes.
+// On failure, returns nil.
+//
+// Callers should explicitly check for the possibility of a nil return, treat
+// it as a failure of the system random number generator, and not continue.
+func GenerateRandomKey(length int) []byte {
+	k := make([]byte, length)
+	if _, err := io.ReadFull(rand.Reader, k); err != nil {
+		return nil
+	}
+	return k
+}
+
+// CodecsFromPairs returns a slice of SecureCookie instances.
+//
+// It is a convenience function to create a list of codecs for key rotation. Note
+// that the generated Codecs will have the default options applied: callers
+// should iterate over each Codec and type-assert the underlying *SecureCookie to
+// change these.
+//
+// Example:
+//
+//      codecs := securecookie.CodecsFromPairs(
+//           []byte("new-hash-key"),
+//           []byte("new-block-key"),
+//           []byte("old-hash-key"),
+//           []byte("old-block-key"),
+//       )
+//
+//      // Modify each instance.
+//      for _, s := range codecs {
+//             if cookie, ok := s.(*securecookie.SecureCookie); ok {
+//                 cookie.MaxAge(86400 * 7)
+//                 cookie.SetSerializer(securecookie.JSONEncoder{})
+//                 cookie.HashFunc(sha512.New512_256)
+//             }
+//         }
+//
+func CodecsFromPairs(keyPairs ...[]byte) []Codec {
+	codecs := make([]Codec, len(keyPairs)/2+len(keyPairs)%2)
+	for i := 0; i < len(keyPairs); i += 2 {
+		var blockKey []byte
+		if i+1 < len(keyPairs) {
+			blockKey = keyPairs[i+1]
+		}
+		codecs[i/2] = New(keyPairs[i], blockKey)
+	}
+	return codecs
+}
+
+// EncodeMulti encodes a cookie value using a group of codecs.
+//
+// The codecs are tried in order. Multiple codecs are accepted to allow
+// key rotation.
+//
+// On error, may return a MultiError.
+func EncodeMulti(name string, value interface{}, codecs ...Codec) (string, error) {
+	if len(codecs) == 0 {
+		return "", errNoCodecs
+	}
+
+	var errors MultiError
+	for _, codec := range codecs {
+		encoded, err := codec.Encode(name, value)
+		if err == nil {
+			return encoded, nil
+		}
+		errors = append(errors, err)
+	}
+	return "", errors
+}
+
+// DecodeMulti decodes a cookie value using a group of codecs.
+//
+// The codecs are tried in order. Multiple codecs are accepted to allow
+// key rotation.
+//
+// On error, may return a MultiError.
+func DecodeMulti(name string, value string, dst interface{}, codecs ...Codec) error {
+	if len(codecs) == 0 {
+		return errNoCodecs
+	}
+
+	var errors MultiError
+	for _, codec := range codecs {
+		err := codec.Decode(name, value, dst)
+		if err == nil {
+			return nil
+		}
+		errors = append(errors, err)
+	}
+	return errors
+}
+
+// MultiError groups multiple errors.
+type MultiError []error
+
+func (m MultiError) IsUsage() bool    { return m.any(func(e Error) bool { return e.IsUsage() }) }
+func (m MultiError) IsDecode() bool   { return m.any(func(e Error) bool { return e.IsDecode() }) }
+func (m MultiError) IsInternal() bool { return m.any(func(e Error) bool { return e.IsInternal() }) }
+
+// Cause returns nil for MultiError; there is no unique underlying cause in the
+// general case.
+//
+// Note: we could conceivably return a non-nil Cause only when there is exactly
+// one child error with a Cause.  However, it would be brittle for client code
+// to rely on the arity of causes inside a MultiError, so we have opted not to
+// provide this functionality.  Clients which really wish to access the Causes
+// of the underlying errors are free to iterate through the errors themselves.
+func (m MultiError) Cause() error { return nil }
+
+func (m MultiError) Error() string {
+	s, n := "", 0
+	for _, e := range m {
+		if e != nil {
+			if n == 0 {
+				s = e.Error()
+			}
+			n++
+		}
+	}
+	switch n {
+	case 0:
+		return "(0 errors)"
+	case 1:
+		return s
+	case 2:
+		return s + " (and 1 other error)"
+	}
+	return fmt.Sprintf("%s (and %d other errors)", s, n-1)
+}
+
+// any returns true if any element of m is an Error for which pred returns true.
+func (m MultiError) any(pred func(Error) bool) bool {
+	for _, e := range m {
+		if ourErr, ok := e.(Error); ok && pred(ourErr) {
+			return true
+		}
+	}
+	return false
+}
--- a/src/vendor/modules.txt
+++ b/src/vendor/modules.txt
@ -189,10 +189,14 @@ github.com/google/go-querystring/query
 github.com/google/gofuzz
 # github.com/google/uuid v1.1.1
 github.com/google/uuid
+# github.com/gorilla/csrf v1.6.2
+github.com/gorilla/csrf
 # github.com/gorilla/handlers v1.3.0
 github.com/gorilla/handlers
 # github.com/gorilla/mux v1.7.2
 github.com/gorilla/mux
+# github.com/gorilla/securecookie v1.1.1
+github.com/gorilla/securecookie
 # github.com/graph-gophers/dataloader v5.0.0+incompatible
 github.com/graph-gophers/dataloader
 # github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af