remote/transport: Make bearer transport go-routine-safe

pkg/v1/remote/transport/bearer.go

@@ -24,8 +24,10 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"sync"
 
 	authchallenge "github.com/docker/distribution/registry/client/auth/challenge"
+
 	"github.com/google/go-containerregistry/internal/redact"
 	"github.com/google/go-containerregistry/pkg/authn"
 	"github.com/google/go-containerregistry/pkg/logs"
@@ -98,6 +100,7 @@ func fromChallenge(reg name.Registry, auth authn.Authenticator, t http.RoundTrip
 }
 
 type bearerTransport struct {
+	mx sync.RWMutex
 	// Wrapped by bearerTransport.
 	inner http.RoundTripper
 	// Basic credentials that we exchange for bearer tokens.
@@ -139,7 +142,10 @@ func (bt *bearerTransport) RoundTrip(in *http.Request) (*http.Response, error) {
 		// the registry with which we are interacting.
 		// In case of redirect http.Client can use an empty Host, check URL too.
 		if matchesHost(bt.registry.RegistryStr(), in, bt.scheme) {
-			hdr := fmt.Sprintf("Bearer %s", bt.bearer.RegistryToken)
+			bt.mx.RLock()
+			localToken := bt.bearer.RegistryToken
+			bt.mx.RUnlock()
+			hdr := fmt.Sprintf("Bearer %s", localToken)
 			in.Header.Set("Authorization", hdr)
 		}
 		return bt.inner.RoundTrip(in)
@@ -156,11 +162,12 @@ func (bt *bearerTransport) RoundTrip(in *http.Request) (*http.Response, error) {
 		res.Body.Close()
 
 		newScopes := []string{}
+		bt.mx.Lock()
+		got := stringSet(bt.scopes)
 		for _, wac := range challenges {
 			// TODO(jonjohnsonjr): Should we also update "realm" or "service"?
 			if want, ok := wac.Parameters["scope"]; ok {
 				// Add any scopes that we don't already request.
-				got := stringSet(bt.scopes)
 				if _, ok := got[want]; !ok {
 					newScopes = append(newScopes, want)
 				}
@@ -172,6 +179,7 @@ func (bt *bearerTransport) RoundTrip(in *http.Request) (*http.Response, error) {
 		// otherwise the registry might just ignore it :/
 		newScopes = append(newScopes, bt.scopes...)
 		bt.scopes = newScopes
+		bt.mx.Unlock()
 
 		// TODO(jonjohnsonjr): Teach transport.Error about "error" and "error_description" from challenge.
 
@@ -196,7 +204,9 @@ func (bt *bearerTransport) refresh(ctx context.Context) error {
 	}
 
 	if auth.RegistryToken != "" {
+		bt.mx.Lock()
 		bt.bearer.RegistryToken = auth.RegistryToken
+		bt.mx.Unlock()
 		return nil
 	}
 
@@ -212,7 +222,9 @@ func (bt *bearerTransport) refresh(ctx context.Context) error {
 
 	// Find a token to turn into a Bearer authenticator
 	if response.Token != "" {
+		bt.mx.Lock()
 		bt.bearer.RegistryToken = response.Token
+		bt.mx.Unlock()
 	}
 
 	// If we obtained a refresh token from the oauth flow, use that for refresh() now.
@@ -306,7 +318,9 @@ func (bt *bearerTransport) refreshOauth(ctx context.Context) ([]byte, error) {
 	}
 
 	v := url.Values{}
+	bt.mx.RLock()
 	v.Set("scope", strings.Join(bt.scopes, " "))
+	bt.mx.RUnlock()
 	if bt.service != "" {
 		v.Set("service", bt.service)
 	}
@@ -362,7 +376,9 @@ func (bt *bearerTransport) refreshBasic(ctx context.Context) ([]byte, error) {
 	client := http.Client{Transport: b}
 
 	v := u.Query()
+	bt.mx.RLock()
 	v["scope"] = bt.scopes
+	bt.mx.RUnlock()
 	v.Set("service", bt.service)
 	u.RawQuery = v.Encode()