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// Copyright 2015 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package server
import (
"context"
"errors"
"fmt"
"net/http"
"strings"
"golang.org/x/oauth2"
"go.chromium.org/luci/gae/service/info"
"go.chromium.org/luci/gae/service/user"
"go.chromium.org/luci/auth/identity"
"go.chromium.org/luci/common/logging"
"go.chromium.org/luci/common/retry/transient"
"go.chromium.org/luci/server/auth"
)
var errBadAuthHeader = errors.New("oauth: bad Authorization header")
// EmailScope is a scope used to identifies user's email. Present in most tokens
// by default. Can be used as a base scope for authentication.
const EmailScope = "https://www.googleapis.com/auth/userinfo.email"
// OAuth2Method implements auth.Method on top of GAE OAuth2 API. It doesn't
// implement auth.UsersAPI.
type OAuth2Method struct {
// Scopes is a list of OAuth scopes to check when authenticating the token.
Scopes []string
}
var _ auth.UserCredentialsGetter = (*OAuth2Method)(nil)
// Authenticate extracts peer's identity from the incoming request.
func (m *OAuth2Method) Authenticate(ctx context.Context, r *http.Request) (*auth.User, error) {
if info.IsDevAppServer(ctx) {
// On "dev_appserver", we verify OAuth2 tokens using Google's OAuth2
// verification endpoint.
//
// It is slow as hell on "dev_appserver", but good enough for local manual
// testing.
devMethod := auth.GoogleOAuth2Method{
Scopes: m.Scopes,
}
return devMethod.Authenticate(ctx, r)
}
header := r.Header.Get("Authorization")
if header == "" || len(m.Scopes) == 0 {
return nil, nil // this method is not applicable
}
// GetOAuthUser RPC is notoriously flaky. Do a bunch of retries on errors.
var err error
for attempt := 0; attempt < 4; attempt++ {
var u *user.User
u, err = user.CurrentOAuth(ctx, m.Scopes...)
if err != nil {
if isFatalOAuthErr(err) {
return nil, err
}
logging.Warningf(ctx, "oauth: failed to execute GetOAuthUser - %s", err)
continue
}
if u.ClientID == "" {
return nil, fmt.Errorf("oauth: ClientID is unexpectedly empty")
}
id, idErr := identity.MakeIdentity("user:" + u.Email)
if idErr != nil {
return nil, idErr
}
return &auth.User{
Identity: id,
Superuser: u.Admin,
Email: u.Email,
ClientID: u.ClientID,
}, nil
}
return nil, transient.Tag.Apply(err)
}
// isFatalOAuthErr examines the error message to figure out whether the error
// from the OAuth service is fatal.
func isFatalOAuthErr(err error) bool {
msg := err.Error()
return strings.Contains(msg, "OAUTH_INVALID_TOKEN") || strings.Contains(msg, "OAUTH_INVALID_REQUEST")
}
// GetUserCredentials implements auth.UserCredentialsGetter.
func (m *OAuth2Method) GetUserCredentials(ctx context.Context, r *http.Request) (*oauth2.Token, error) {
chunks := strings.SplitN(r.Header.Get("Authorization"), " ", 2)
if len(chunks) != 2 || (chunks[0] != "OAuth" && chunks[0] != "Bearer") {
return nil, errBadAuthHeader
}
return &oauth2.Token{
AccessToken: chunks[1],
TokenType: "Bearer",
}, nil
}