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// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package auth
import (
"context"
"crypto/sha256"
"crypto/subtle"
"encoding/hex"
"errors"
"strings"
"time"
auth_model "code.gitea.io/gitea/models/auth"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/timeutil"
"code.gitea.io/gitea/modules/util"
)
// Based on https://paragonie.com/blog/2015/04/secure-authentication-php-with-long-term-persistence#secure-remember-me-cookies
// The auth token consists of two parts: ID and token hash
// Every device login creates a new auth token with an individual id and hash.
// If a device uses the token to login into the instance, a fresh token gets generated which has the same id but a new hash.
var (
ErrAuthTokenInvalidFormat = util.NewInvalidArgumentErrorf("auth token has an invalid format")
ErrAuthTokenExpired = util.NewInvalidArgumentErrorf("auth token has expired")
ErrAuthTokenInvalidHash = util.NewInvalidArgumentErrorf("auth token is invalid")
)
func CheckAuthToken(ctx context.Context, value string) (*auth_model.AuthToken, error) {
if len(value) == 0 {
return nil, nil
}
parts := strings.SplitN(value, ":", 2)
if len(parts) != 2 {
return nil, ErrAuthTokenInvalidFormat
}
t, err := auth_model.GetAuthTokenByID(ctx, parts[0])
if err != nil {
if errors.Is(err, util.ErrNotExist) {
return nil, ErrAuthTokenExpired
}
return nil, err
}
if t.ExpiresUnix < timeutil.TimeStampNow() {
return nil, ErrAuthTokenExpired
}
hashedToken := sha256.Sum256([]byte(parts[1]))
if subtle.ConstantTimeCompare([]byte(t.TokenHash), []byte(hex.EncodeToString(hashedToken[:]))) == 0 {
// If an attacker steals a token and uses the token to create a new session the hash gets updated.
// When the victim uses the old token the hashes don't match anymore and the victim should be notified about the compromised token.
return nil, ErrAuthTokenInvalidHash
}
return t, nil
}
func RegenerateAuthToken(ctx context.Context, t *auth_model.AuthToken) (*auth_model.AuthToken, string, error) {
token, hash, err := generateTokenAndHash()
if err != nil {
return nil, "", err
}
newToken := &auth_model.AuthToken{
ID: t.ID,
TokenHash: hash,
UserID: t.UserID,
ExpiresUnix: timeutil.TimeStampNow().AddDuration(time.Duration(setting.LogInRememberDays*24) * time.Hour),
}
if err := auth_model.UpdateAuthTokenByID(ctx, newToken); err != nil {
return nil, "", err
}
return newToken, token, nil
}
func CreateAuthTokenForUserID(ctx context.Context, userID int64) (*auth_model.AuthToken, string, error) {
t := &auth_model.AuthToken{
UserID: userID,
ExpiresUnix: timeutil.TimeStampNow().AddDuration(time.Duration(setting.LogInRememberDays*24) * time.Hour),
}
var err error
t.ID, err = util.CryptoRandomString(10)
if err != nil {
return nil, "", err
}
token, hash, err := generateTokenAndHash()
if err != nil {
return nil, "", err
}
t.TokenHash = hash
if err := auth_model.InsertAuthToken(ctx, t); err != nil {
return nil, "", err
}
return t, token, nil
}
func generateTokenAndHash() (string, string, error) {
buf, err := util.CryptoRandomBytes(32)
if err != nil {
return "", "", err
}
token := hex.EncodeToString(buf)
hashedToken := sha256.Sum256([]byte(token))
return token, hex.EncodeToString(hashedToken[:]), nil
}
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