94 lines
3 KiB
Go
94 lines
3 KiB
Go
// Copyright 2012 The Go 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 xsrftoken provides methods for generating and validating secure XSRF tokens.
|
|
package xsrftoken // import "golang.org/x/net/xsrftoken"
|
|
|
|
import (
|
|
"crypto/hmac"
|
|
"crypto/sha1"
|
|
"crypto/subtle"
|
|
"encoding/base64"
|
|
"fmt"
|
|
"strconv"
|
|
"strings"
|
|
"time"
|
|
)
|
|
|
|
// Timeout is the duration for which XSRF tokens are valid.
|
|
// It is exported so clients may set cookie timeouts that match generated tokens.
|
|
const Timeout = 24 * time.Hour
|
|
|
|
// clean sanitizes a string for inclusion in a token by replacing all ":"s.
|
|
func clean(s string) string {
|
|
return strings.Replace(s, ":", "_", -1)
|
|
}
|
|
|
|
// Generate returns a URL-safe secure XSRF token that expires in 24 hours.
|
|
//
|
|
// key is a secret key for your application; it must be non-empty.
|
|
// userID is an optional unique identifier for the user.
|
|
// actionID is an optional action the user is taking (e.g. POSTing to a particular path).
|
|
func Generate(key, userID, actionID string) string {
|
|
return generateTokenAtTime(key, userID, actionID, time.Now())
|
|
}
|
|
|
|
// generateTokenAtTime is like Generate, but returns a token that expires 24 hours from now.
|
|
func generateTokenAtTime(key, userID, actionID string, now time.Time) string {
|
|
if len(key) == 0 {
|
|
panic("zero length xsrf secret key")
|
|
}
|
|
// Round time up and convert to milliseconds.
|
|
milliTime := (now.UnixNano() + 1e6 - 1) / 1e6
|
|
|
|
h := hmac.New(sha1.New, []byte(key))
|
|
fmt.Fprintf(h, "%s:%s:%d", clean(userID), clean(actionID), milliTime)
|
|
|
|
// Get the padded base64 string then removing the padding.
|
|
tok := string(h.Sum(nil))
|
|
tok = base64.URLEncoding.EncodeToString([]byte(tok))
|
|
tok = strings.TrimRight(tok, "=")
|
|
|
|
return fmt.Sprintf("%s:%d", tok, milliTime)
|
|
}
|
|
|
|
// Valid reports whether a token is a valid, unexpired token returned by Generate.
|
|
func Valid(token, key, userID, actionID string) bool {
|
|
return validTokenAtTime(token, key, userID, actionID, time.Now())
|
|
}
|
|
|
|
// validTokenAtTime reports whether a token is valid at the given time.
|
|
func validTokenAtTime(token, key, userID, actionID string, now time.Time) bool {
|
|
if len(key) == 0 {
|
|
panic("zero length xsrf secret key")
|
|
}
|
|
// Extract the issue time of the token.
|
|
sep := strings.LastIndex(token, ":")
|
|
if sep < 0 {
|
|
return false
|
|
}
|
|
millis, err := strconv.ParseInt(token[sep+1:], 10, 64)
|
|
if err != nil {
|
|
return false
|
|
}
|
|
issueTime := time.Unix(0, millis*1e6)
|
|
|
|
// Check that the token is not expired.
|
|
if now.Sub(issueTime) >= Timeout {
|
|
return false
|
|
}
|
|
|
|
// Check that the token is not from the future.
|
|
// Allow 1 minute grace period in case the token is being verified on a
|
|
// machine whose clock is behind the machine that issued the token.
|
|
if issueTime.After(now.Add(1 * time.Minute)) {
|
|
return false
|
|
}
|
|
|
|
expected := generateTokenAtTime(key, userID, actionID, issueTime)
|
|
|
|
// Check that the token matches the expected value.
|
|
// Use constant time comparison to avoid timing attacks.
|
|
return subtle.ConstantTimeCompare([]byte(token), []byte(expected)) == 1
|
|
}
|