// Copyright 2014 The oauth2 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 google import ( "sort" "strings" "sync" "time" "golang.org/x/net/context" "golang.org/x/oauth2" ) // Set at init time by appenginevm_hook.go. If true, we are on App Engine Managed VMs. var appengineVM bool // Set at init time by appengine_hook.go. If nil, we're not on App Engine. var appengineTokenFunc func(c context.Context, scopes ...string) (token string, expiry time.Time, err error) // AppEngineTokenSource returns a token source that fetches tokens // issued to the current App Engine application's service account. // If you are implementing a 3-legged OAuth 2.0 flow on App Engine // that involves user accounts, see oauth2.Config instead. // // The provided context must have come from appengine.NewContext. func AppEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource { if appengineTokenFunc == nil { panic("google: AppEngineTokenSource can only be used on App Engine.") } scopes := append([]string{}, scope...) sort.Strings(scopes) return &appEngineTokenSource{ ctx: ctx, scopes: scopes, key: strings.Join(scopes, " "), } } // aeTokens helps the fetched tokens to be reused until their expiration. var ( aeTokensMu sync.Mutex aeTokens = make(map[string]*tokenLock) // key is space-separated scopes ) type tokenLock struct { mu sync.Mutex // guards t; held while fetching or updating t t *oauth2.Token } type appEngineTokenSource struct { ctx context.Context scopes []string key string // to aeTokens map; space-separated scopes } func (ts *appEngineTokenSource) Token() (*oauth2.Token, error) { if appengineTokenFunc == nil { panic("google: AppEngineTokenSource can only be used on App Engine.") } aeTokensMu.Lock() tok, ok := aeTokens[ts.key] if !ok { tok = &tokenLock{} aeTokens[ts.key] = tok } aeTokensMu.Unlock() tok.mu.Lock() defer tok.mu.Unlock() if tok.t.Valid() { return tok.t, nil } access, exp, err := appengineTokenFunc(ts.ctx, ts.scopes...) if err != nil { return nil, err } tok.t = &oauth2.Token{ AccessToken: access, Expiry: exp, } return tok.t, nil }