registry: treat basic-auth 401 as unauthorized

Client-side login (daemon down) was wrapping a 401 as a plain error, so
Auth() moved on to the next endpoint. That can print Login Succeeded if
the HTTP fallback happens to answer 200.

Fixes #7237

Signed-off-by: Dean Chen <862469039@qq.com>

internal/registry/auth.go

@@ -67,7 +67,11 @@ func loginV2(ctx context.Context, authConfig *registry.AuthConfig, endpoint APIE
 
 	if resp.StatusCode != http.StatusOK {
 		// TODO(dmcgowan): Attempt to further interpret result, status code and error code string
-		return "", fmt.Errorf("login attempt to %s failed with status: %d %s", endpointStr, resp.StatusCode, http.StatusText(resp.StatusCode))
+		err := fmt.Errorf("login attempt to %s failed with status: %d %s", endpointStr, resp.StatusCode, http.StatusText(resp.StatusCode))
+		if resp.StatusCode == http.StatusUnauthorized {
+			return "", unauthorizedErr{err}
+		}
+		return "", err
 	}
 
 	return credentialAuthConfig.IdentityToken, nil

internal/registry/auth_test.go

@@ -0,0 +1,40 @@
+package registry
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"github.com/containerd/errdefs"
+	"github.com/moby/moby/api/types/registry"
+	"gotest.tools/v3/assert"
+	is "gotest.tools/v3/assert/cmp"
+)
+
+func TestLoginV2BasicAuthUnauthorized(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		user, pass, ok := r.BasicAuth()
+		if !ok || user != "alice" || pass != "secret" {
+			w.Header().Set("WWW-Authenticate", `Basic realm="test"`)
+			http.Error(w, "401 Unauthorized", http.StatusUnauthorized)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	t.Cleanup(srv.Close)
+
+	u, err := url.Parse(srv.URL)
+	assert.NilError(t, err)
+	endpoint := APIEndpoint{URL: u}
+	ctx := context.Background()
+
+	_, err = loginV2(ctx, &registry.AuthConfig{Username: "alice", Password: "wrong"}, endpoint, "docker-test")
+	assert.ErrorContains(t, err, "401")
+	assert.Check(t, errdefs.IsUnauthorized(err))
+
+	token, err := loginV2(ctx, &registry.AuthConfig{Username: "alice", Password: "secret"}, endpoint, "docker-test")
+	assert.NilError(t, err)
+	assert.Check(t, is.Equal("", token))
+}