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Copy pathauth.go
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94 lines (85 loc) · 2.7 KB
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// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.
package gin
import (
"crypto/subtle"
"encoding/base64"
"errors"
"sort"
)
const (
AuthUserKey = "user"
)
type (
Accounts map[string]string
authPair struct {
Value string
User string
}
authPairs []authPair
)
func (a authPairs) Len() int { return len(a) }
func (a authPairs) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a authPairs) Less(i, j int) bool { return a[i].Value < a[j].Value }
// Implements a basic Basic HTTP Authorization. It takes as argument a map[string]string where
// the key is the user name and the value is the password.
func BasicAuth(accounts Accounts) HandlerFunc {
pairs, err := processAccounts(accounts)
if err != nil {
panic(err)
}
return func(c *Context) {
// Search user in the slice of allowed credentials
user, ok := searchCredential(pairs, c.Request.Header.Get("Authorization"))
if !ok {
// Credentials doesn't match, we return 401 Unauthorized and abort request.
c.Writer.Header().Set("WWW-Authenticate", "Basic realm=\"Authorization Required\"")
c.Fail(401, errors.New("Unauthorized"))
} else {
// user is allowed, set UserId to key "user" in this context, the userId can be read later using
// c.Get(gin.AuthUserKey)
c.Set(AuthUserKey, user)
}
}
}
func processAccounts(accounts Accounts) (authPairs, error) {
if len(accounts) == 0 {
return nil, errors.New("Empty list of authorized credentials")
}
pairs := make(authPairs, 0, len(accounts))
for user, password := range accounts {
if len(user) == 0 {
return nil, errors.New("User can not be empty")
}
base := user + ":" + password
value := "Basic " + base64.StdEncoding.EncodeToString([]byte(base))
pairs = append(pairs, authPair{
Value: value,
User: user,
})
}
// We have to sort the credentials in order to use bsearch later.
sort.Sort(pairs)
return pairs, nil
}
func searchCredential(pairs authPairs, auth string) (string, bool) {
if len(auth) == 0 {
return "", false
}
// Search user in the slice of allowed credentials
r := sort.Search(len(pairs), func(i int) bool { return pairs[i].Value >= auth })
if r < len(pairs) && secureCompare(pairs[r].Value, auth) {
return pairs[r].User, true
} else {
return "", false
}
}
func secureCompare(given, actual string) bool {
if subtle.ConstantTimeEq(int32(len(given)), int32(len(actual))) == 1 {
return subtle.ConstantTimeCompare([]byte(given), []byte(actual)) == 1
} else {
/* Securely compare actual to itself to keep constant time, but always return false */
return subtle.ConstantTimeCompare([]byte(actual), []byte(actual)) == 1 && false
}
}