feat(auth): add idtoken package

auth/idtoken/cache.go

@@ -0,0 +1,133 @@
+// Copyright 2023 Google LLC
+//
+// 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 idtoken
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+type cachingClient struct {
+	client *http.Client
+
+	// clock optionally specifies a func to return the current time.
+	// If nil, time.Now is used.
+	clock func() time.Time
+
+	mu    sync.Mutex
+	certs map[string]*cachedResponse
+}
+
+func newCachingClient(client *http.Client) *cachingClient {
+	return &cachingClient{
+		client: client,
+		certs:  make(map[string]*cachedResponse, 2),
+	}
+}
+
+type cachedResponse struct {
+	resp *certResponse
+	exp  time.Time
+}
+
+func (c *cachingClient) getCert(ctx context.Context, url string) (*certResponse, error) {
+	if response, ok := c.get(url); ok {
+		return response, nil
+	}
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	req = req.WithContext(ctx)
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("idtoken: unable to retrieve cert, got status code %d", resp.StatusCode)
+	}
+
+	certResp := &certResponse{}
+	if err := json.NewDecoder(resp.Body).Decode(certResp); err != nil {
+		return nil, err
+
+	}
+	c.set(url, certResp, resp.Header)
+	return certResp, nil
+}
+
+func (c *cachingClient) now() time.Time {
+	if c.clock != nil {
+		return c.clock()
+	}
+	return time.Now()
+}
+
+func (c *cachingClient) get(url string) (*certResponse, bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	cachedResp, ok := c.certs[url]
+	if !ok {
+		return nil, false
+	}
+	if c.now().After(cachedResp.exp) {
+		return nil, false
+	}
+	return cachedResp.resp, true
+}
+
+func (c *cachingClient) set(url string, resp *certResponse, headers http.Header) {
+	exp := c.calculateExpireTime(headers)
+	c.mu.Lock()
+	c.certs[url] = &cachedResponse{resp: resp, exp: exp}
+	c.mu.Unlock()
+}
+
+// calculateExpireTime will determine the expire time for the cache based on
+// HTTP headers. If there is any difficulty reading the headers the fallback is
+// to set the cache to expire now.
+func (c *cachingClient) calculateExpireTime(headers http.Header) time.Time {
+	var maxAge int
+	cc := strings.Split(headers.Get("cache-control"), ",")
+	for _, v := range cc {
+		if strings.Contains(v, "max-age") {
+			ss := strings.Split(v, "=")
+			if len(ss) < 2 {
+				return c.now()
+			}
+			ma, err := strconv.Atoi(ss[1])
+			if err != nil {
+				return c.now()
+			}
+			maxAge = ma
+		}
+	}
+	a := headers.Get("age")
+	if a == "" {
+		return c.now().Add(time.Duration(maxAge) * time.Second)
+	}
+	age, err := strconv.Atoi(a)
+	if err != nil {
+		return c.now()
+	}
+	return c.now().Add(time.Duration(maxAge-age) * time.Second)
+}

auth/idtoken/cache_test.go

@@ -0,0 +1,82 @@
+// Copyright 2023 Google LLC
+//
+// 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 idtoken
+
+import (
+	"net/http"
+	"sync"
+	"testing"
+	"time"
+)
+
+type fakeClock struct {
+	mu sync.Mutex
+	t  time.Time
+}
+
+func (c *fakeClock) Now() time.Time {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.t
+}
+
+func (c *fakeClock) Sleep(d time.Duration) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.t = c.t.Add(d)
+}
+
+func TestCacheHit(t *testing.T) {
+	clock := &fakeClock{t: time.Now()}
+	fakeResp := &certResponse{
+		Keys: []jwk{
+			{
+				Kid: "123",
+			},
+		},
+	}
+	cache := newCachingClient(nil)
+	cache.clock = clock.Now
+
+	// Cache should be empty
+	cert, ok := cache.get(googleSACertsURL)
+	if ok || cert != nil {
+		t.Fatal("cache for SA certs should be empty")
+	}
+
+	// Add an item, but make it expire now
+	cache.set(googleSACertsURL, fakeResp, make(http.Header))
+	clock.Sleep(time.Nanosecond) // it expires when current time is > expiration, not >=
+	cert, ok = cache.get(googleSACertsURL)
+	if ok || cert != nil {
+		t.Fatal("cache for SA certs should be expired")
+	}
+
+	// Add an item that expires in 1 seconds
+	h := make(http.Header)
+	h.Set("age", "0")
+	h.Set("cache-control", "public, max-age=1, must-revalidate, no-transform")
+	cache.set(googleSACertsURL, fakeResp, h)
+	cert, ok = cache.get(googleSACertsURL)
+	if !ok || cert == nil || cert.Keys[0].Kid != "123" {
+		t.Fatal("cache for SA certs have a resp")
+	}
+	// Wait
+	clock.Sleep(2 * time.Second)
+	cert, ok = cache.get(googleSACertsURL)
+	if ok || cert != nil {
+		t.Fatal("cache for SA certs should be expired")
+	}
+}

auth/idtoken/compute.go

@@ -0,0 +1,77 @@
+// Copyright 2023 Google LLC
+//
+// 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 idtoken
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/compute/metadata"
+)
+
+const identitySuffix = "instance/service-accounts/default/identity"
+
+// computeTokenProvider checks if this code is being run on GCE. If it is, it
+// will use the metadata service to build a TokenProvider that fetches ID
+// tokens.
+func computeTokenProvider(opts *Options) (auth.TokenProvider, error) {
+	if opts.CustomClaims != nil {
+		return nil, fmt.Errorf("idtoken: Options.CustomClaims can't be used with the metadata service, please provide a service account if you would like to use this feature")
+	}
+	tp := computeIDTokenProvider{
+		audience: opts.Audience,
+		format:   opts.ComputeTokenFormat,
+		client:   *metadata.NewClient(opts.client()),
+	}
+	return auth.NewCachedTokenProvider(tp, &auth.CachedTokenProviderOptions{
+		ExpireEarly: 5 * time.Minute,
+	}), nil
+}
+
+type computeIDTokenProvider struct {
+	audience string
+	format   ComputeTokenFormat
+	client   metadata.Client
+}
+
+func (c computeIDTokenProvider) Token(ctx context.Context) (*auth.Token, error) {
+	v := url.Values{}
+	v.Set("audience", c.audience)
+	if c.format != ComputeTokenFormatStandard {
+		v.Set("format", "full")
+	}
+	if c.format == ComputeTokenFormatFullWithLicense {
+		v.Set("licenses", "TRUE")
+	}
+	urlSuffix := identitySuffix + "?" + v.Encode()
+	res, err := c.client.Get(urlSuffix)
+	if err != nil {
+		return nil, err
+	}
+	if res == "" {
+		return nil, fmt.Errorf("idtoken: invalid empty response from metadata service")
+	}
+	return &auth.Token{
+		Value: res,
+		Type:  internal.TokenTypeBearer,
+		// Compute tokens are valid for one hour:
+		// https://cloud.google.com/iam/docs/create-short-lived-credentials-direct#create-id
+		Expiry: time.Now().Add(1 * time.Hour),
+	}, nil
+}

auth/idtoken/compute_test.go

@@ -0,0 +1,102 @@
+// Copyright 2023 Google LLC
+//
+// 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 idtoken
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+const metadataHostEnv = "GCE_METADATA_HOST"
+
+func TestComputeTokenSource(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.Contains(r.URL.Path, identitySuffix) {
+			t.Errorf("got %q, want contains %q", r.URL.Path, identitySuffix)
+		}
+		if got, want := r.URL.Query().Get("audience"), "aud"; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		if got, want := r.URL.Query().Get("format"), "full"; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		if got, want := r.URL.Query().Get("licenses"), "TRUE"; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		w.Write([]byte(`fake_token`))
+	}))
+	defer ts.Close()
+	t.Setenv(metadataHostEnv, strings.TrimPrefix(ts.URL, "http://"))
+	tp, err := computeTokenProvider(&Options{
+		Audience:           "aud",
+		ComputeTokenFormat: ComputeTokenFormatFullWithLicense,
+	})
+	if err != nil {
+		t.Fatalf("computeTokenProvider() = %v", err)
+	}
+	tok, err := tp.Token(context.Background())
+	if err != nil {
+		t.Fatalf("tp.Token() = %v", err)
+	}
+	if want := "fake_token"; tok.Value != want {
+		t.Errorf("got %q, want %q", tok.Value, want)
+	}
+}
+
+func TestComputeTokenSource_Standard(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.Contains(r.URL.Path, identitySuffix) {
+			t.Errorf("got %q, want contains %q", r.URL.Path, identitySuffix)
+		}
+		if got, want := r.URL.Query().Get("audience"), "aud"; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		if got, want := r.URL.Query().Get("format"), ""; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		if got, want := r.URL.Query().Get("licenses"), ""; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		w.Write([]byte(`fake_token`))
+	}))
+	defer ts.Close()
+	t.Setenv(metadataHostEnv, strings.TrimPrefix(ts.URL, "http://"))
+	tp, err := computeTokenProvider(&Options{
+		Audience:           "aud",
+		ComputeTokenFormat: ComputeTokenFormatStandard,
+	})
+	if err != nil {
+		t.Fatalf("computeTokenProvider() = %v", err)
+	}
+	tok, err := tp.Token(context.Background())
+	if err != nil {
+		t.Fatalf("tp.Token() = %v", err)
+	}
+	if want := "fake_token"; tok.Value != want {
+		t.Errorf("got %q, want %q", tok.Value, want)
+	}
+}
+
+func TestComputeTokenSource_Invalid(t *testing.T) {
+	if _, err := computeTokenProvider(&Options{
+		Audience:     "aud",
+		CustomClaims: map[string]interface{}{"foo": "bar"},
+	}); err == nil {
+		t.Fatal("computeTokenProvider() = nil, expected non-nil error", err)
+	}
+}