95 lines
2.7 KiB
Go
95 lines
2.7 KiB
Go
// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
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// Use of this source code is governed by a MIT style
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// license that can be found in the LICENSE file.
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package gin
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import (
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"crypto/subtle"
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"encoding/base64"
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"errors"
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"sort"
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)
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const (
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AuthUserKey = "user"
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)
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type (
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Accounts map[string]string
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authPair struct {
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Value string
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User string
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}
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authPairs []authPair
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)
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func (a authPairs) Len() int { return len(a) }
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func (a authPairs) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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func (a authPairs) Less(i, j int) bool { return a[i].Value < a[j].Value }
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// Implements a basic Basic HTTP Authorization. It takes as argument a map[string]string where
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// the key is the user name and the value is the password.
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func BasicAuth(accounts Accounts) HandlerFunc {
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pairs, err := processAccounts(accounts)
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if err != nil {
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panic(err)
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}
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return func(c *Context) {
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// Search user in the slice of allowed credentials
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user, ok := searchCredential(pairs, c.Request.Header.Get("Authorization"))
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if !ok {
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// Credentials doesn't match, we return 401 Unauthorized and abort request.
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c.Writer.Header().Set("WWW-Authenticate", "Basic realm=\"Authorization Required\"")
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c.Fail(401, errors.New("Unauthorized"))
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} else {
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// user is allowed, set UserId to key "user" in this context, the userId can be read later using
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// c.Get(gin.AuthUserKey)
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c.Set(AuthUserKey, user)
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}
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}
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}
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func processAccounts(accounts Accounts) (authPairs, error) {
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if len(accounts) == 0 {
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return nil, errors.New("Empty list of authorized credentials")
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}
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pairs := make(authPairs, 0, len(accounts))
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for user, password := range accounts {
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if len(user) == 0 {
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return nil, errors.New("User can not be empty")
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}
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base := user + ":" + password
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value := "Basic " + base64.StdEncoding.EncodeToString([]byte(base))
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pairs = append(pairs, authPair{
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Value: value,
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User: user,
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})
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}
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// We have to sort the credentials in order to use bsearch later.
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sort.Sort(pairs)
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return pairs, nil
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}
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func searchCredential(pairs authPairs, auth string) (string, bool) {
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if len(auth) == 0 {
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return "", false
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}
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// Search user in the slice of allowed credentials
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r := sort.Search(len(pairs), func(i int) bool { return pairs[i].Value >= auth })
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if r < len(pairs) && secureCompare(pairs[r].Value, auth) {
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return pairs[r].User, true
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} else {
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return "", false
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}
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}
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func secureCompare(given, actual string) bool {
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if subtle.ConstantTimeEq(int32(len(given)), int32(len(actual))) == 1 {
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return subtle.ConstantTimeCompare([]byte(given), []byte(actual)) == 1
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} else {
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/* Securely compare actual to itself to keep constant time, but always return false */
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return subtle.ConstantTimeCompare([]byte(actual), []byte(actual)) == 1 && false
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}
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}
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