reload token file for InClusterConfig every 5 minutes

Kubernetes-commit: 287f6a564fb8c264f281056011f4a66f197b18f4

rest/token_source.go

@@ -0,0 +1,138 @@
+/*
+Copyright 2018 The Kubernetes 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 rest
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+	"golang.org/x/oauth2"
+)
+
+// TokenSourceWrapTransport returns a WrapTransport that injects bearer tokens
+// authentication from an oauth2.TokenSource.
+func TokenSourceWrapTransport(ts oauth2.TokenSource) func(http.RoundTripper) http.RoundTripper {
+	return func(rt http.RoundTripper) http.RoundTripper {
+		return &tokenSourceTransport{
+			base: rt,
+			ort: &oauth2.Transport{
+				Source: ts,
+				Base:   rt,
+			},
+		}
+	}
+}
+
+func newCachedPathTokenSource(path string) oauth2.TokenSource {
+	return &cachingTokenSource{
+		now:    time.Now,
+		leeway: 1 * time.Minute,
+		base: &fileTokenSource{
+			path: path,
+			// This period was picked because it is half of the minimum validity
+			// duration for a token provisioned by they TokenRequest API. This is
+			// unsophisticated and should induce rotation at a frequency that should
+			// work with the token volume source.
+			period: 5 * time.Minute,
+		},
+	}
+}
+
+type tokenSourceTransport struct {
+	base http.RoundTripper
+	ort  http.RoundTripper
+}
+
+func (tst *tokenSourceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	// This is to allow --token to override other bearer token providers.
+	if req.Header.Get("Authorization") != "" {
+		return tst.base.RoundTrip(req)
+	}
+	return tst.ort.RoundTrip(req)
+}
+
+type fileTokenSource struct {
+	path   string
+	period time.Duration
+}
+
+var _ = oauth2.TokenSource(&fileTokenSource{})
+
+func (ts *fileTokenSource) Token() (*oauth2.Token, error) {
+	tokb, err := ioutil.ReadFile(ts.path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read token file %q: %v", ts.path, err)
+	}
+	tok := strings.TrimSpace(string(tokb))
+	if len(tok) == 0 {
+		return nil, fmt.Errorf("read empty token from file %q", ts.path)
+	}
+
+	return &oauth2.Token{
+		AccessToken: tok,
+		Expiry:      time.Now().Add(ts.period),
+	}, nil
+}
+
+type cachingTokenSource struct {
+	base   oauth2.TokenSource
+	leeway time.Duration
+
+	sync.RWMutex
+	tok *oauth2.Token
+
+	// for testing
+	now func() time.Time
+}
+
+var _ = oauth2.TokenSource(&cachingTokenSource{})
+
+func (ts *cachingTokenSource) Token() (*oauth2.Token, error) {
+	now := ts.now()
+	// fast path
+	ts.RLock()
+	tok := ts.tok
+	ts.RUnlock()
+
+	if tok != nil && tok.Expiry.Add(-1*ts.leeway).After(now) {
+		return tok, nil
+	}
+
+	// slow path
+	ts.Lock()
+	defer ts.Unlock()
+	if tok := ts.tok; tok != nil && tok.Expiry.Add(-1*ts.leeway).After(now) {
+		return tok, nil
+	}
+
+	tok, err := ts.base.Token()
+	if err != nil {
+		if ts.tok == nil {
+			return nil, err
+		}
+		glog.Errorf("Unable to rotate token: %v", err)
+		return ts.tok, nil
+	}
+
+	ts.tok = tok
+	return tok, nil
+}