Recognize invalid error responses of registry.redhat.io

... when checking for missing images.

In particular, this is necessary for use-sigstore-attachments not to
cause failures when pulling from registry.redhat.io.

Red Hat internal reference: RITM1310318

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

docker/docker_client.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"encoding/json"
@@ -983,15 +984,25 @@ func (c *dockerClient) getOCIDescriptorContents(ctx context.Context, ref dockerR
 // isManifestUnknownError returns true iff err from fetchManifest is a “manifest unknown” error.
 func isManifestUnknownError(err error) bool {
 	var errs errcode.Errors
-	if !errors.As(err, &errs) || len(errs) == 0 {
-		return false
+	if errors.As(err, &errs) && len(errs) != 0 {
+		firstErr := errs[0]
+		// docker/distribution, and as defined in the spec
+		var ec errcode.ErrorCoder
+		if errors.As(firstErr, &ec) && ec.ErrorCode() == v2.ErrorCodeManifestUnknown {
+			return true
+		}
+		// registry.redhat.io as of October 2022
+		var e errcode.Error
+		if errors.As(firstErr, &e) && e.ErrorCode() == errcode.ErrorCodeUnknown && e.Message == "Not Found" {
+			return true
+		}
 	}
-	err = errs[0]
-	ec, ok := err.(errcode.ErrorCoder)
-	if !ok {
-		return false
+	// ALSO registry.redhat.io as of October 2022
+	var unexpected *unexpectedHTTPResponseError
+	if errors.As(err, &unexpected) && unexpected.StatusCode == http.StatusNotFound && bytes.Contains(unexpected.Response, []byte("Not found")) {
+		return true
 	}
-	return ec.ErrorCode() == v2.ErrorCodeManifestUnknown
+	return false
 }
 
 // getSigstoreAttachmentManifest loads and parses the manifest for sigstore attachments for

docker/docker_client_test.go

@@ -1,6 +1,8 @@
 package docker
 
 import (
+	"bufio"
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -328,3 +330,59 @@ func TestNeedsNoRetry(t *testing.T) {
 		t.Fatal("Got the need to retry, but none should be required")
 	}
 }
+
+func TestIsManifestUnknownError(t *testing.T) {
+	// Mostly a smoke test; we can add more registries here if they need special handling.
+
+	for _, c := range []struct{ name, response string }{
+		{
+			name: "docker.io when a tag in an _existing repo_ is not found",
+			response: "HTTP/1.1 404 Not Found\r\n" +
+				"Connection: close\r\n" +
+				"Content-Length: 109\r\n" +
+				"Content-Type: application/json\r\n" +
+				"Date: Thu, 12 Aug 2021 20:51:32 GMT\r\n" +
+				"Docker-Distribution-Api-Version: registry/2.0\r\n" +
+				"Ratelimit-Limit: 100;w=21600\r\n" +
+				"Ratelimit-Remaining: 100;w=21600\r\n" +
+				"Strict-Transport-Security: max-age=31536000\r\n" +
+				"\r\n" +
+				"{\"errors\":[{\"code\":\"MANIFEST_UNKNOWN\",\"message\":\"manifest unknown\",\"detail\":{\"Tag\":\"this-does-not-exist\"}}]}\n",
+		},
+		{
+			name: "registry.redhat.io/v2/this-does-not-exist/manifests/latest",
+			response: "HTTP/1.1 404 Not Found\r\n" +
+				"Connection: close\r\n" +
+				"Content-Length: 53\r\n" +
+				"Cache-Control: max-age=0, no-cache, no-store\r\n" +
+				"Content-Type: application/json\r\n" +
+				"Date: Thu, 13 Oct 2022 18:15:15 GMT\r\n" +
+				"Expires: Thu, 13 Oct 2022 18:15:15 GMT\r\n" +
+				"Pragma: no-cache\r\n" +
+				"Server: Apache\r\n" +
+				"Strict-Transport-Security: max-age=63072000; includeSubdomains; preload\r\n" +
+				"X-Hostname: crane-tbr06.cran-001.prod.iad2.dc.redhat.com\r\n" +
+				"\r\n" +
+				"{\"errors\": [{\"code\": \"404\", \"message\": \"Not Found\"}]}\r\n",
+		},
+		{
+			name: "registry.redhat.io/v2/rhosp15-rhel8/openstack-cron/manifests/sha256-8df5e60c42668706ac108b59c559b9187fa2de7e4e262e2967e3e9da35d5a8d7.sig",
+			response: "HTTP/1.1 404 Not Found\r\n" +
+				"Connection: close\r\n" +
+				"Content-Length: 10\r\n" +
+				"Accept-Ranges: bytes\r\n" +
+				"Date: Thu, 13 Oct 2022 18:13:53 GMT\r\n" +
+				"Server: AkamaiNetStorage\r\n" +
+				"X-Docker-Size: -1\r\n" +
+				"\r\n" +
+				"Not found\r\n",
+		},
+	} {
+		resp, err := http.ReadResponse(bufio.NewReader(bytes.NewReader([]byte(c.response))), nil)
+		require.NoError(t, err, c.name)
+		err = fmt.Errorf("wrapped: %w", registryHTTPResponseToError(resp))
+
+		res := isManifestUnknownError(err)
+		assert.True(t, res, "%#v", err, c.name)
+	}
+}

docker/errors.go

@@ -52,7 +52,8 @@ func registryHTTPResponseToError(res *http.Response) error {
 		if len(response) > 50 {
 			response = response[:50] + "..."
 		}
-		err = fmt.Errorf("StatusCode: %d, %s", e.StatusCode, response)
+		// %.0w makes e visible to error.Unwrap() without including any text
+		err = fmt.Errorf("StatusCode: %d, %s%.0w", e.StatusCode, response, e)
 	}
 	return err
 }