98 lines
3.1 KiB
Go
98 lines
3.1 KiB
Go
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// Copyright 2012 Google Inc. All Rights Reserved.
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// Copyright 2014 The Macaron Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package csrf
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import (
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"bytes"
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"crypto/hmac"
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"crypto/sha1"
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"crypto/subtle"
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"encoding/base64"
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"fmt"
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"strconv"
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"strings"
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"time"
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)
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// The duration that XSRF tokens are valid.
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// It is exported so clients may set cookie timeouts that match generated tokens.
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const TIMEOUT = 24 * time.Hour
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// clean sanitizes a string for inclusion in a token by replacing all ":"s.
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func clean(s string) string {
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return strings.Replace(s, ":", "_", -1)
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}
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// GenerateToken returns a URL-safe secure XSRF token that expires in 24 hours.
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//
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// key is a secret key for your application.
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// userID is a unique identifier for the user.
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// actionID is the action the user is taking (e.g. POSTing to a particular path).
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func GenerateToken(key, userID, actionID string) string {
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return generateTokenAtTime(key, userID, actionID, time.Now())
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}
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// generateTokenAtTime is like Generate, but returns a token that expires 24 hours from now.
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func generateTokenAtTime(key, userID, actionID string, now time.Time) string {
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h := hmac.New(sha1.New, []byte(key))
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fmt.Fprintf(h, "%s:%s:%d", clean(userID), clean(actionID), now.UnixNano())
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tok := fmt.Sprintf("%s:%d", h.Sum(nil), now.UnixNano())
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return base64.URLEncoding.EncodeToString([]byte(tok))
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}
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// Valid returns true if token is a valid, unexpired token returned by Generate.
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func ValidToken(token, key, userID, actionID string) bool {
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return validTokenAtTime(token, key, userID, actionID, time.Now())
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}
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// validTokenAtTime is like Valid, but it uses now to check if the token is expired.
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func validTokenAtTime(token, key, userID, actionID string, now time.Time) bool {
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// Decode the token.
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data, err := base64.URLEncoding.DecodeString(token)
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if err != nil {
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return false
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}
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// Extract the issue time of the token.
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sep := bytes.LastIndex(data, []byte{':'})
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if sep < 0 {
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return false
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}
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nanos, err := strconv.ParseInt(string(data[sep+1:]), 10, 64)
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if err != nil {
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return false
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}
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issueTime := time.Unix(0, nanos)
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// Check that the token is not expired.
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if now.Sub(issueTime) >= TIMEOUT {
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return false
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}
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// Check that the token is not from the future.
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// Allow 1 minute grace period in case the token is being verified on a
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// machine whose clock is behind the machine that issued the token.
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if issueTime.After(now.Add(1 * time.Minute)) {
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return false
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}
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expected := generateTokenAtTime(key, userID, actionID, issueTime)
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// Check that the token matches the expected value.
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// Use constant time comparison to avoid timing attacks.
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return subtle.ConstantTimeCompare([]byte(token), []byte(expected)) == 1
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}
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