Add expires_in and issued_at to the auth spec.

This extends the specification for the Bearer token response to include
information pertaining to when an issued Bearer token will expire.

This also allows the client to accept `access_token` as an alias for `token`.

Signed-off-by: Matt Moore <mattmoor@google.com>

docs/client/auth/session.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/Sirupsen/logrus"
 	"github.com/docker/distribution/registry/client"
 	"github.com/docker/distribution/registry/client/transport"
 )
@@ -85,11 +86,24 @@ func (ea *endpointAuthorizer) ModifyRequest(req *http.Request) error {
 	return nil
 }
 
+// This is the minimum duration a token can last (in seconds).
+// A token must not live less than 60 seconds because older versions
+// of the Docker client didn't read their expiration from the token
+// response and assumed 60 seconds.  So to remain compatible with
+// those implementations, a token must live at least this long.
+const minimumTokenLifetimeSeconds = 60
+
+// Private interface for time used by this package to enable tests to provide their own implementation.
+type clock interface {
+	Now() time.Time
+}
+
 type tokenHandler struct {
 	header    http.Header
 	creds     CredentialStore
 	scope     tokenScope
 	transport http.RoundTripper
+	clock     clock
 
 	tokenLock       sync.Mutex
 	tokenCache      string
@@ -108,12 +122,24 @@ func (ts tokenScope) String() string {
 	return fmt.Sprintf("%s:%s:%s", ts.Resource, ts.Scope, strings.Join(ts.Actions, ","))
 }
 
+// An implementation of clock for providing real time data.
+type realClock struct{}
+
+// Now implements clock
+func (realClock) Now() time.Time { return time.Now() }
+
 // NewTokenHandler creates a new AuthenicationHandler which supports
 // fetching tokens from a remote token server.
 func NewTokenHandler(transport http.RoundTripper, creds CredentialStore, scope string, actions ...string) AuthenticationHandler {
+	return newTokenHandler(transport, creds, realClock{}, scope, actions...)
+}
+
+// newTokenHandler exposes the option to provide a clock to manipulate time in unit testing.
+func newTokenHandler(transport http.RoundTripper, creds CredentialStore, c clock, scope string, actions ...string) AuthenticationHandler {
 	return &tokenHandler{
 		transport: transport,
 		creds:     creds,
+		clock:     c,
 		scope: tokenScope{
 			Resource: "repository",
 			Scope:    scope,
@@ -146,40 +172,43 @@ func (th *tokenHandler) AuthorizeRequest(req *http.Request, params map[string]st
 func (th *tokenHandler) refreshToken(params map[string]string) error {
 	th.tokenLock.Lock()
 	defer th.tokenLock.Unlock()
-	now := time.Now()
+	now := th.clock.Now()
 	if now.After(th.tokenExpiration) {
-		token, err := th.fetchToken(params)
+		tr, err := th.fetchToken(params)
 		if err != nil {
 			return err
 		}
-		th.tokenCache = token
-		th.tokenExpiration = now.Add(time.Minute)
+		th.tokenCache = tr.Token
+		th.tokenExpiration = tr.IssuedAt.Add(time.Duration(tr.ExpiresIn) * time.Second)
 	}
 
 	return nil
 }
 
 type tokenResponse struct {
-	Token string `json:"token"`
+	Token       string    `json:"token"`
+	AccessToken string    `json:"access_token"`
+	ExpiresIn   int       `json:"expires_in"`
+	IssuedAt    time.Time `json:"issued_at"`
 }
 
-func (th *tokenHandler) fetchToken(params map[string]string) (token string, err error) {
+func (th *tokenHandler) fetchToken(params map[string]string) (token *tokenResponse, err error) {
 	//log.Debugf("Getting bearer token with %s for %s", challenge.Parameters, ta.auth.Username)
 	realm, ok := params["realm"]
 	if !ok {
-		return "", errors.New("no realm specified for token auth challenge")
+		return nil, errors.New("no realm specified for token auth challenge")
 	}
 
 	// TODO(dmcgowan): Handle empty scheme
 
 	realmURL, err := url.Parse(realm)
 	if err != nil {
-		return "", fmt.Errorf("invalid token auth challenge realm: %s", err)
+		return nil, fmt.Errorf("invalid token auth challenge realm: %s", err)
 	}
 
 	req, err := http.NewRequest("GET", realmURL.String(), nil)
 	if err != nil {
-		return "", err
+		return nil, err
 	}
 
 	reqParams := req.URL.Query()
@@ -206,26 +235,44 @@ func (th *tokenHandler) fetchToken(params map[string]string) (token string, err
 
 	resp, err := th.client().Do(req)
 	if err != nil {
-		return "", err
+		return nil, err
 	}
 	defer resp.Body.Close()
 
 	if !client.SuccessStatus(resp.StatusCode) {
-		return "", fmt.Errorf("token auth attempt for registry: %s request failed with status: %d %s", req.URL, resp.StatusCode, http.StatusText(resp.StatusCode))
+		return nil, fmt.Errorf("token auth attempt for registry: %s request failed with status: %d %s", req.URL, resp.StatusCode, http.StatusText(resp.StatusCode))
 	}
 
 	decoder := json.NewDecoder(resp.Body)
 
 	tr := new(tokenResponse)
 	if err = decoder.Decode(tr); err != nil {
-		return "", fmt.Errorf("unable to decode token response: %s", err)
+		return nil, fmt.Errorf("unable to decode token response: %s", err)
+	}
+
+	// `access_token` is equivalent to `token` and if both are specified
+	// the choice is undefined.  Canonicalize `access_token` by sticking
+	// things in `token`.
+	if tr.AccessToken != "" {
+		tr.Token = tr.AccessToken
 	}
 
 	if tr.Token == "" {
-		return "", errors.New("authorization server did not include a token in the response")
+		return nil, errors.New("authorization server did not include a token in the response")
 	}
 
-	return tr.Token, nil
+	if tr.ExpiresIn < minimumTokenLifetimeSeconds {
+		logrus.Debugf("Increasing token expiration to: %d seconds", tr.ExpiresIn)
+		// The default/minimum lifetime.
+		tr.ExpiresIn = minimumTokenLifetimeSeconds
+	}
+
+	if tr.IssuedAt.IsZero() {
+		// issued_at is optional in the token response.
+		tr.IssuedAt = th.clock.Now()
+	}
+
+	return tr, nil
 }
 
 type basicHandler struct {