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csrf.go
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csrf.go
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// Package csrf generates and validates csrf tokens for martini.
// There are multiple methods of delivery including via a cookie or HTTP
// header.
// Validation occurs via a traditional hidden form key of "_csrf", or via
// a custom HTTP header "X-CSRFToken".
//
// package main
//
// import (
// "github.com/go-martini/martini"
// "github.com/martini-contib/csrf"
// "github.com/martini-contrib/render"
// "github.com/martini-contib/sessions"
// "net/http"
// )
//
// func main() {
// m := martini.Classic()
// store := sessions.NewCookieStore([]byte("secret123"))
// m.Use(sessions.Sessions("my_session", store))
// // Setup generation middleware.
// m.Use(csrf.Generate(&csrf.Options{
// Secret: "token123",
// SessionKey: "userID",
// }))
// m.Use(render.Renderer())
//
// // Simulate the authentication of a session. If userID exists redirect
// // to a form that requires csrf protection.
// m.Get("/", func(s sessions.Session, r render.Render) {
// if s.Get("userID") == nil {
// r.Redirect("/login", 302)
// return
// }
// r.Redirect("/protected", 302)
// })
//
// // Set userID for the session.
// m.Get("/login", func(s sessions.Session, r render.Render) {
// s.Set("userID", "123456")
// r.Redirect("/", 302)
// })
//
// // Render a protected form. Passing a csrf token by calling x.GetToken()
// m.Get("/protected", func(s sessions.Session, r render.Render, x csrf.CSRF) {
// if s.Get("userID") == nil {
// r.Redirect("/login", 401)
// return
// }
// r.HTML(200, "protected", x.GetToken())
// })
//
// // Apply csrf validation to route.
// m.Post("/protected", csrf.Validate, func(s sessions.Session, r render.Render) {
// if s.Get("userID") != nil {
// r.HTML(200, "result", "You submitted a valid token")
// return
// }
// r.Redirect("/login", 401)
// })
//
// m.Run()
// }
package csrf
import (
"fmt"
"net/http"
"net/url"
"regexp"
"strconv"
"strings"
"time"
"github.com/go-martini/martini"
"github.com/martini-contrib/sessions"
"github.com/tommyp1ckles/xsrftoken"
)
// CSRF is used to get the current token and validate a suspect token.
type CSRF interface {
// Return HTTP header to search for token.
GetHeaderName() string
// Return form value to search for token.
GetFormName() string
// Return cookie name to search for token.
GetCookieName() string
// Return the token.
GetToken() string
// Validate by token.
ValidToken(t string) bool
// Error replies to the request with a custom function when ValidToken fails.
Error(w http.ResponseWriter)
}
type csrf struct {
// Header name value for setting and getting csrf token.
Header string
// Form name value for setting and getting csrf token.
Form string
// Cookie name value for setting and getting csrf token.
Cookie string
// Token generated to pass via header, cookie, or hidden form value.
Token string
// This value must be unique per user.
ID string
// Secret used along with the unique id above to generate the Token.
Secret string
// ErrorFunc is the custom function that replies to the request when ValidToken fails.
ErrorFunc func(w http.ResponseWriter)
}
// Returns the name of the HTTP header for csrf token.
func (c *csrf) GetHeaderName() string {
return c.Header
}
// Returns the name of the form value for csrf token.
func (c *csrf) GetFormName() string {
return c.Form
}
// Returns the name of the cookie for csrf token.
func (c *csrf) GetCookieName() string {
return c.Cookie
}
// Returns the current token. This is typically used
// to populate a hidden form in an HTML template.
func (c *csrf) GetToken() string {
return c.Token
}
// Validates the passed token against the existing Secret and ID.
func (c *csrf) ValidToken(t string) bool {
return xsrftoken.Valid(t, c.Secret, c.ID, "POST")
}
// Error replies to the request when ValidToken fails.
func (c *csrf) Error(w http.ResponseWriter) {
c.ErrorFunc(w)
}
// Options maintains options to manage behavior of Generate.
type Options struct {
// The global secret value used to generate Tokens.
Secret string
// HTTP header used to set and get token.
Header string
// Form value used to set and get token.
Form string
// Cookie value used to set and get token.
Cookie string
// Key used for getting the unique ID per user.
SessionKey string
// If true, send token via X-CSRFToken header.
SetHeader bool
// If true, send token via _csrf cookie.
SetCookie bool
// Set the Secure flag to true on the cookie.
Secure bool
// The function called when Validate fails.
ErrorFunc func(w http.ResponseWriter)
// Array of allowed origins. Will be checked during generation from a cross site request.
// Must be the complete origin. Example: 'https://golang.org'. You will only need to set this
// if you are supporting CORS.
AllowedOrigins []string
}
const domainReg = `^\.?[a-z\d]+(?:(?:[a-z\d]*)|(?:[a-z\d\-]*[a-z\d]))(?:\.[a-z\d]+(?:(?:[a-z\d]*)|(?:[a-z\d\-]*[a-z\d])))*$`
// Generate maps CSRF to each request. If this request is a Get request, it will generate a new token.
// Additionally, depending on options set, generated tokens will be sent via Header and/or Cookie.
func Generate(opts *Options) martini.Handler {
return func(s sessions.Session, c martini.Context, r *http.Request, w http.ResponseWriter) {
if opts.Header == "" {
opts.Header = "X-CSRFToken"
}
if opts.Form == "" {
opts.Form = "_csrf"
}
if opts.Cookie == "" {
opts.Cookie = "_csrf"
}
if opts.ErrorFunc == nil {
opts.ErrorFunc = func(w http.ResponseWriter) {
http.Error(w, "Invalid csrf token.", http.StatusBadRequest)
}
}
x := &csrf{
Secret: opts.Secret,
Header: opts.Header,
Form: opts.Form,
Cookie: opts.Cookie,
ErrorFunc: opts.ErrorFunc,
}
c.MapTo(x, (*CSRF)(nil))
uid := s.Get(opts.SessionKey)
if uid == nil {
return
}
switch uid.(type) {
case string:
x.ID = uid.(string)
case int64:
x.ID = strconv.FormatInt(uid.(int64), 10)
default:
return
}
if r.Header.Get("Origin") != "" {
originUrl, err := url.Parse(r.Header.Get("Origin"))
if err != nil {
return
}
if originUrl.Host != r.Host {
isAllowed := false
for _, origin := range opts.AllowedOrigins {
if originUrl.String() == origin {
isAllowed = true
break
}
}
if !isAllowed {
return
}
}
}
// If cookie present, map existing token, else generate a new one.
if ex, err := r.Cookie(opts.Cookie); err == nil && ex.Value != "" {
x.Token = ex.Value
} else {
x.Token = xsrftoken.Generate(x.Secret, x.ID, "POST")
if opts.SetCookie {
expire := time.Now().AddDate(0, 0, 1)
// Verify the domain is valid. If it is not, set as empty.
domain := strings.Split(r.Host, ":")[0]
if ok, err := regexp.Match(domainReg, []byte(domain)); !ok || err != nil {
domain = ""
}
cookie := &http.Cookie{
Name: opts.Cookie,
Value: x.Token,
Path: "/",
Domain: domain,
Expires: expire,
RawExpires: expire.Format(time.UnixDate),
MaxAge: 0,
Secure: opts.Secure,
HttpOnly: false,
Raw: fmt.Sprintf("%s=%s", opts.Cookie, x.Token),
Unparsed: []string{fmt.Sprintf("token=%s", x.Token)},
}
http.SetCookie(w, cookie)
}
}
if opts.SetHeader {
w.Header().Add(opts.Header, x.Token)
}
}
}
// Validate should be used as a per route middleware. It attempts to get a token from a "X-CSRFToken"
// HTTP header and then a "_csrf" form value. If one of these is found, the token will be validated
// using ValidToken. If this validation fails, custom Error is sent in the reply.
// If neither a header or form value is found, http.StatusBadRequest is sent.
func Validate(r *http.Request, w http.ResponseWriter, x CSRF) {
if token := r.Header.Get(x.GetHeaderName()); token != "" {
if !x.ValidToken(token) {
x.Error(w)
}
return
}
if token := r.FormValue(x.GetFormName()); token != "" {
if !x.ValidToken(token) {
x.Error(w)
}
return
}
http.Error(w, "Bad Request", http.StatusBadRequest)
return
}