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