From 8f91c777559748fa6e857d9fc1f4ae079a532813 Mon Sep 17 00:00:00 2001
From: Christopher Speller <crspeller@gmail.com>
Date: Mon, 3 Oct 2016 16:03:15 -0400
Subject: Adding ability to serve TLS directly from Mattermost server (#4119)

---
 vendor/golang.org/x/net/xsrftoken/xsrf.go | 88 +++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 vendor/golang.org/x/net/xsrftoken/xsrf.go

(limited to 'vendor/golang.org/x/net/xsrftoken/xsrf.go')

diff --git a/vendor/golang.org/x/net/xsrftoken/xsrf.go b/vendor/golang.org/x/net/xsrftoken/xsrf.go
new file mode 100644
index 000000000..8d2187872
--- /dev/null
+++ b/vendor/golang.org/x/net/xsrftoken/xsrf.go
@@ -0,0 +1,88 @@
+// 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.
+// userID is a unique identifier for the user.
+// actionID is the 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 {
+	// 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 {
+	// 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
+}
-- 
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