From f6a11223079e9b39c98af5183bd969b705c41ab7 Mon Sep 17 00:00:00 2001
From: Ramkumar Chinchani <rchincha@cisco.com>
Date: Wed, 4 Oct 2023 23:33:50 +0000
Subject: [PATCH] fix: handle ancient empty docker layers

Earlier versions of docker images had empty layers of 1024 zero-valued
octets.

https://github.com/moby/moby/issues/20917#issuecomment-191901912

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>
---
 pkg/log/log.go          |  4 ++++
 pkg/overlay/metadata.go | 11 ++++++++++-
 test/docker-base.bats   | 10 ++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/pkg/log/log.go b/pkg/log/log.go
index 553383f0..c8a8c280 100644
--- a/pkg/log/log.go
+++ b/pkg/log/log.go
@@ -46,6 +46,10 @@ func Infof(msg string, v ...interface{}) {
 	addStackerLogSentinel(log.NewEntry(log.Log.(*log.Logger))).Infof(msg, v...)
 }
 
+func Warnf(msg string, v ...interface{}) {
+	addStackerLogSentinel(log.NewEntry(log.Log.(*log.Logger))).Warnf(msg, v...)
+}
+
 func Errorf(msg string, v ...interface{}) {
 	addStackerLogSentinel(log.NewEntry(log.Log.(*log.Logger))).Errorf(msg, v...)
 }
diff --git a/pkg/overlay/metadata.go b/pkg/overlay/metadata.go
index 3114dcf3..43906a2a 100644
--- a/pkg/overlay/metadata.go
+++ b/pkg/overlay/metadata.go
@@ -3,6 +3,7 @@ package overlay
 import (
 	"bytes"
 	"encoding/json"
+	"io/fs"
 	"os"
 	"path"
 
@@ -117,7 +118,15 @@ func (ovl overlayMetadata) lxcRootfsString(config types.StackerConfig, tag strin
 	for _, layer := range manifest.Layers {
 		contents := overlayPath(config.RootFSDir, layer.Digest, "overlay")
 		if _, err := os.Stat(contents); err != nil {
-			return "", errors.Wrapf(err, "%s does not exist", contents)
+			if errors.Is(err, fs.ErrNotExist) {
+				// some docker layers may be empty tars, so ignore these
+				// https://github.com/moby/moby/issues/20917#issuecomment-191901912
+				log.Warnf("%s skipping empty tar layer", layer.Digest)
+
+				continue
+			}
+
+			return "", errors.Wrapf(err, "%s unable to stat", contents)
 		}
 		lowerdirs = append(lowerdirs, contents)
 	}
diff --git a/test/docker-base.bats b/test/docker-base.bats
index b21d1cdc..5df40d6b 100644
--- a/test/docker-base.bats
+++ b/test/docker-base.bats
@@ -31,3 +31,13 @@ EOF
     umoci unpack --image oci:layer1 dest
     [ ! -f dest/rootfs/favicon.ico ]
 }
+
+@test "image with empty layer" {
+    cat > stacker.yaml <<EOF
+image:
+    from:
+        type: docker
+        url: docker://ghcr.io/project-stacker/grafana-oss:10.1.2-ubuntu
+EOF
+    stacker build
+}