"""Restore an exact, hash-bound Docker build context into a new directory.""" import argparse from contextlib import contextmanager import hashlib import json from pathlib import Path, PurePosixPath import shutil import tarfile import tempfile def digest(path): value = hashlib.sha256() with Path(path).open('rb') as stream: for block in iter(lambda: stream.read(1024 * 1024), b''): value.update(block) return value.hexdigest() def relative(name): path = PurePosixPath(name) if (not name or path.is_absolute() or '..' in path.parts or '.' in name.split('/') or '\\' in name or str(path) != name): raise ValueError('Unsafe context member: ' + name) return path def declared_container_links(manifest, entries, tar): """Allow only exact Git-bound links to a declared paired container checkout.""" absolute = {name: row for name, row in entries.items() if row.get('kind') == 'symlink' and PurePosixPath(row['target']).is_absolute()} if not absolute: return {} if manifest.get('schema_version', 1) < 3 or 'instance.json' not in entries: raise ValueError('Absolute source link requires a version 3 instance binding') member = tar.getmember('instance.json'); row = entries['instance.json'] if not member.isfile() or member.size != row['bytes'] or member.size > 2 * 1024 * 1024: raise ValueError('Invalid source link declaration') data = tar.extractfile(member).read() if hashlib.sha256(data).hexdigest() != row['sha256']: raise ValueError('Source link declaration hash mismatch') instance = json.loads(data) repositories = {r['key']: r for r in instance['repositories']} allowed = {} for repo in repositories.values(): path = PurePosixPath(repo['path']) if not path.is_absolute() or path.parts[:2] != ('/', 'testbed') or '..' in path.parts or '.git' in path.parts: raise ValueError('Invalid declared repository path') for link in repo.get('workspace_links', []): target = repositories[link['target_repository']]['path'] if target == repo['path'] or link['original_target'] != target: raise ValueError('Container link does not bind a distinct paired repository') blob = target.encode() oid = hashlib.sha1(b'blob ' + str(len(blob)).encode() + b'\0' + blob).hexdigest() if oid != link['expected_blob']: raise ValueError('Container link differs from its original Git blob') name = str(PurePosixPath(repo['path'].lstrip('/')) / relative(link['path'])) if name in allowed: raise ValueError('Duplicate container link declaration') allowed[name] = target if any(allowed.get(name) != row['target'] for name, row in absolute.items()): raise ValueError('Undeclared absolute context link') return {name: row['target'].lstrip('/') for name, row in absolute.items()} def check_virtual_links(entries, container_links): """Resolve link graphs without touching an absolute container path on the host.""" links = {name: row['target'] for name, row in entries.items() if row.get('kind') == 'symlink'} for name in links: pending = list(PurePosixPath(name).parts); stack = []; followed = 0 while pending: part = pending.pop(0) if part in ('', '.'): continue if part == '..': if not stack: raise ValueError('Context link escapes output') stack.pop(); continue stack.append(part); prefix = '/'.join(stack) if prefix in links: followed += 1 if followed > 40: raise ValueError('Cyclic or excessive context link graph') target = links[prefix] if PurePosixPath(target).is_absolute(): if prefix not in container_links: raise ValueError('Undeclared absolute context link') stack = []; target = container_links[prefix] else: stack.pop() pending = list(PurePosixPath(target).parts) + pending @contextmanager def archive_stream(root, reference): parts=reference.get('parts') if parts is not None: if not isinstance(parts,list) or not parts: raise ValueError('Archive parts must be nonempty') with tempfile.TemporaryFile() as output: total=0;whole=hashlib.sha256() for part in parts: source=root/relative(part['path']) if source.is_symlink() or part['offset']!=total or source.stat().st_size!=part['bytes']: raise ValueError('Archive part path/order/size mismatch') actual=hashlib.sha256() with source.open('rb') as stream: for block in iter(lambda:stream.read(1024*1024),b''): actual.update(block);whole.update(block);output.write(block);total+=len(block) if actual.hexdigest()!=part['sha256']: raise ValueError('Archive part hash mismatch') if total!=reference['bytes'] or whole.hexdigest()!=reference['sha256']: raise ValueError('Reconstructed archive hash/size mismatch') output.seek(0) yield output else: source=root/relative(reference['path']) if source.is_symlink() or source.stat().st_size!=reference['bytes'] or digest(source)!=reference['sha256']: raise ValueError('Context archive hash/size mismatch') with source.open('rb') as stream:yield stream def materialize(manifest_path, output, verify_only=False): manifest_path, output = Path(manifest_path), Path(output) if output is not None else None if output is not None and (output.exists() or output.is_symlink()): raise FileExistsError(output) manifest = json.loads(manifest_path.read_text()) reference = manifest['archive'] entries = {str(relative(row['path'])): row for row in manifest['files']} if len(entries) != len(manifest['files']): raise ValueError('Duplicate manifest members') for name in entries: if any(str(parent) in entries for parent in PurePosixPath(name).parents): raise ValueError('File/directory context collision') with archive_stream(manifest_path.parent,reference) as source, tarfile.open(fileobj=source,mode='r:gz') as tar: members = tar.getmembers() names = [str(relative(member.name)) for member in members] if len(names) != len(set(names)) or set(names) != set(entries): raise ValueError('Unlisted, missing or duplicate archive members') container_links = declared_container_links(manifest, entries, tar) for member in members: row = entries[member.name] if member.mode != row['mode'] or not 0 <= member.mode <= 0o777: raise ValueError('Context member type/size/mode mismatch') if row.get('kind','file')=='symlink': target=row['target'] if (not member.issym() or member.linkname!=target or not target or (PurePosixPath(target).is_absolute() and member.name not in container_links) or '\\' in target or '\x00' in target): raise ValueError('Unsafe or changed context link') data=target.encode() if len(data)!=row['bytes']: raise ValueError('Context link size mismatch') actual=hashlib.sha256(data).hexdigest() elif row.get('kind','file')=='file' and member.isfile() and member.size==row['bytes']: actual_hash=hashlib.sha256() with tar.extractfile(member) as stream: for block in iter(lambda:stream.read(1024*1024),b''):actual_hash.update(block) actual=actual_hash.hexdigest() else: raise ValueError('Unsupported or changed context member') if actual != row['sha256']: raise ValueError('Context member hash mismatch: ' + member.name) check_virtual_links(entries, container_links) if verify_only: return {'files':len(entries),'archive_sha256':reference['sha256'],'state':'ARCHIVE_VERIFIED'} output.mkdir(parents=True, exist_ok=False) try: for member in members:(output/member.name).parent.mkdir(parents=True,exist_ok=True) for member in members: if member.isfile(): target=output/member.name with tar.extractfile(member) as source,target.open('xb') as destination:shutil.copyfileobj(source,destination) target.chmod(member.mode) # No regular-file write occurs after creating any source link. for member in members: if member.issym():(output/member.name).symlink_to(member.linkname) except BaseException: shutil.rmtree(output) raise return {'files': len(entries), 'symlinks':sum(row.get('kind')=='symlink' for row in entries.values()), 'declared_container_symlinks': len(container_links), 'archive_sha256': reference['sha256'], 'output': str(output)} # crossswe repair publication context compatibility v1 def descriptor_ref(folder, reference): path = folder / relative(reference['path']) if any(p.is_symlink() for p in (path, *path.parents)) or not path.is_file(): raise ValueError('Unsafe descriptor reference') if path.stat().st_size != reference['bytes'] or digest(path) != reference['sha256']: raise ValueError('Descriptor reference hash/size mismatch') return path def current_context(root, instance_id): folder = root / 'environments' / relative(instance_id) image_path = folder / 'image.json' if any(p.is_symlink() for p in (image_path, *image_path.parents)): raise ValueError('Unsafe image descriptor path') image = json.loads(image_path.read_text()) if image['instance_id'] != instance_id: raise ValueError('Image descriptor instance differs') manifest = descriptor_ref(folder, image['context_manifest']) recipe = None if image.get('recipe'): recipe = json.loads(descriptor_ref(folder, image['recipe']).read_text()) import re if (recipe.get('kind') != 'immutable-parent-delta' or not re.fullmatch(r'[^@\s]+@sha256:[0-9a-f]{64}', recipe.get('parent_image_ref', '')) or recipe['actual_context'] != image['context_manifest'] or descriptor_ref(folder, recipe['actual_context']) != manifest): raise ValueError('Invalid immutable parent/delta recipe') parent = json.loads(descriptor_ref(folder, recipe['parent_image_descriptor']).read_text()) if parent.get('image_ref') != recipe['parent_image_ref']: raise ValueError('Recipe parent descriptor identity differs') descriptor_ref(folder, parent['context_manifest']) descriptor_ref(folder, recipe['source_authority']) descriptor_ref(folder, recipe['build_receipt']) # Every parent descriptor uses environment-root-relative refs, including an # exact historical descriptor stored below history/. Never rebase its refs # to the history directory. recipe_chain(folder, image) return manifest, recipe def recipe_chain(folder, image, seen=None): seen = set() if seen is None else seen identity = image['image_ref'] if identity in seen or len(seen) >= 40: raise ValueError('Cyclic or excessive recipe chain') seen.add(identity) if image.get('provenance_only'): if image.get('registry_digest') != 'sha256:e6c20a1727d4eb758737a9c2710a2e0a805bc534fc056929d7ddb2279b55437c' or identity != 'silinchen0617/crossrepo-bench@sha256:e6c20a1727d4eb758737a9c2710a2e0a805bc534fc056929d7ddb2279b55437c': raise ValueError('Unsupported provenance-only immutable parent') context = descriptor_ref(folder, image['context_manifest']) for reference in image['verified_provenance'].values(): descriptor_ref(folder, reference) original = json.loads(descriptor_ref(folder, image['original_descriptor']).read_text()) if original['registry_digest'] != 'sha256:dd0cf3223f7e9524c4c21aafce54a1b59a7e53288027a1332ddeb1577cad6dda': raise ValueError('Historical original parent differs') return [{'image_ref': identity, 'context_manifest': str(context), 'context_kind': 'verified-registry-parent-reference'}] + recipe_chain(folder, original, seen) context = descriptor_ref(folder, image['context_manifest']) result = [{'image_ref': identity, 'context_manifest': str(context), 'context_kind': 'delta' if image.get('recipe') else 'full'}] if image.get('recipe'): recipe = json.loads(descriptor_ref(folder, image['recipe']).read_text()) parent = json.loads(descriptor_ref(folder, recipe['parent_image_descriptor']).read_text()) if parent['image_ref'] != recipe['parent_image_ref'] or recipe['actual_context'] != image['context_manifest']: raise ValueError('Recipe chain identity differs') result.extend(recipe_chain(folder, parent, seen)) return result def verify_manifest(manifest_path): return materialize(manifest_path, None, verify_only=True) def materialize_image(root, instance_id, output): manifest, recipe = current_context(Path(root), instance_id) result = materialize(manifest, output) result['context_manifest'] = str(manifest) result['context_kind'] = 'delta' if recipe else 'full' if recipe: result['parent_image_ref'] = recipe['parent_image_ref'] result['source_authority_full_build_context'] = recipe['source_authority_full_build_context'] result['recipe_note'] = 'Build this actual delta with its pinned parent; historical full context remains preserved.' return result def main(): parser = argparse.ArgumentParser(description=__doc__) parser.add_argument('--instance-id', required=True) parser.add_argument('--output-dir', type=Path, required=True) args = parser.parse_args() if Path(args.instance_id).name != args.instance_id or args.instance_id in ('','.', '..'): parser.error('Use a canonical instance ID') root = Path(__file__).resolve().parents[1] print(json.dumps(materialize_image(root, args.instance_id, args.output_dir))) if __name__ == '__main__': main()