From 939ac84c97521899ca20dd712e8be9e1ebabbcd9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anders=20F=20Bj=C3=B6rklund?= <anders.f.bjorklund@gmail.com>
Date: Tue, 15 Nov 2022 18:51:37 +0100
Subject: [PATCH] Add manifest and config

For showing the raw manifest and the image config, both in json.
Add basic pretty-printing, for advanced topics one can use "jq".
---
 README.md   |  3 +++
 undocker.py | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/README.md b/README.md
index 0714eba..8b798aa 100644
--- a/README.md
+++ b/README.md
@@ -17,8 +17,11 @@ Unpacks a Docker image.
       --verbose, -v
       --debug, -d
       --list, --ls          List layers in an image
+      --manifest, -m        Dump manifest contained in archive
       --layer LAYER, -l LAYER
                             Extract only the specified layer
+      --config, -c          Dump config contained in archive
+      --pretty, -p          Pretty print the json dump output
 
 ## Examples
 
diff --git a/undocker.py b/undocker.py
index 4384372..b6f5e55 100644
--- a/undocker.py
+++ b/undocker.py
@@ -31,15 +31,24 @@ def parse_args():
     p.add_argument('--layers',
                    action='store_true',
                    help='List layers in an image')
+    p.add_argument('--config', '-c',
+                   action='store_true',
+                   help='Dump config contained in archive')
     p.add_argument('--list', '--ls',
                    action='store_true',
                    help='List images/tags contained in archive')
+    p.add_argument('--manifest', '-m',
+                   action='store_true',
+                   help='Dump manifest contained in archive')
     p.add_argument('--layer', '-l',
                    action='append',
                    help='Extract only the specified layer')
     p.add_argument('--no-whiteouts', '-W',
                    action='store_true',
                    help='Do not process whiteout (.wh.*) files')
+    p.add_argument('--pretty', '-p',
+                   action='store_true',
+                   help='Pretty print the json dump output')
 
     g = p.add_argument_group('Logging options')
     g.add_argument('--verbose', '-v',
@@ -95,6 +104,10 @@ def main():
     args = parse_args()
     logging.basicConfig(level=args.loglevel)
 
+    pretty = {}
+    if args.pretty:
+        pretty = {"indent": 4}
+
     with tempfile.NamedTemporaryFile() as fd, (
             open(args.image, 'rb') if args.image
             else io.open(sys.stdin.fileno(), 'rb')) as image:
@@ -124,6 +137,34 @@ def main():
                 LOG.error('No image name specified and multiple '
                           'images contained in archive')
                 sys.exit(1)
+            if args.manifest or args.config:
+                try:
+                    mj = img.extractfile('manifest.json')
+                    manifest = json.loads(mj.read().decode('utf-8'))
+                except KeyError:
+                    LOG.error('failed to find manifest.json')
+                    sys.exit(1)
+                if args.manifest:
+                    print(json.dumps(manifest, **pretty))
+                    sys.exit(0)
+                configs = []
+                repotag = None
+                if args.image:
+                    name, tag = parse_image_spec(args.image)
+                    repotag = "%s:%s" % (name, tag)
+                for image in manifest:
+                    if repotag and repotag not in image['RepoTags']:
+                        continue
+                    try:
+                        cj = img.extractfile(image['Config'])
+                        config = json.loads(cj.read().decode('utf-8'))
+                    except KeyError:
+                        LOG.error('failed to read config json')
+                        sys.exit(1)
+                    configs.append(config)
+                if args.config:
+                    print(json.dumps(configs, **pretty))
+                    sys.exit(0)
 
             try:
                 top = repos[name][tag]