From 42c6fe0dfc465e8c64bc448e556da0a5a1ebd728 Mon Sep 17 00:00:00 2001
From: EHotwagner <ehotwagner@gmail.com>
Date: Tue, 20 Oct 2026 23:07:24 +0200
Subject: [PATCH 1/2] Retain bounded static ELF dependency correspondence for
 BAR image

---
 containers/barc-stock-headless/README.md      |  10 ++
 containers/barc-stock-headless/build-image.py | 150 ++++++++++++++++++
 containers/barc-stock-headless/test_source.py | 134 ++++++++++++++++
 3 files changed, 294 insertions(+)

diff --git a/containers/barc-stock-headless/README.md b/containers/barc-stock-headless/README.md
index 9034b0c..3c44b6f 100644
--- a/containers/barc-stock-headless/README.md
+++ b/containers/barc-stock-headless/README.md
@@ -31,6 +31,16 @@ The builder fetches the existing HighBar vcpkg baseline256acc640… and verifies
 
 The builder records `/opt/barc/toolchain/ubuntu-packages.txt`, `vcpkg-status.txt`, generated manifest, tool-byte SHA256SUMS and MANIFEST.SHA256. Subsequent stages verify those produced bytes. The maintained platform runner separately retains the actual resulting immutable image ID and logs. These records are qualification OUTPUTS; they neither require a previously qualified image nor establish a successful build in advance. Official parent metadata is verified, but raw layer/config verification and the full resulting toolchain/build/ELF closure remain first-build obligations.
 
+## Static ELF correspondence
+
+Before the integration stage launches the downloader, it writes `/opt/barc/STATIC-ELF.json` from the actual selected engine and produced plugin. Both root hashes must match the pinned engine digest and the existing plugin digest manifest. The collector reads ELF bytes directly; it never invokes a loader, `ldd`, the engine or the plugin. It follows `DT_NEEDED` and the selected x86-64 interpreter recursively, records file hashes, byte sizes, metadata, dependency edges and resolved aliases, then checks the complete inventory again. A previous output is never overwritten. A failed collection produces no success manifest.
+
+This is a deliberately limited image-local **candidate correspondence**, not the dynamic loader's search algorithm. Candidate directories are each object's directory, its explicit `$ORIGIN`-relative RPATH or RUNPATH, and the fixed image directories `/lib/x86_64-linux-gnu`, `/usr/lib/x86_64-linux-gnu`, `/lib64` and `/usr/lib64`. Aliases to the same canonical file deduplicate; distinct candidates refuse even when their bytes match. Missing dependencies, escaping or changing aliases, SONAME mismatches, malformed ELF, audit/filter dependencies, NODEFLIB, combined RPATH/RUNPATH and unsupported path expansions refuse. Only little-endian ELF64 x86-64 executables/shared objects and `/lib64/ld-linux-x86-64.so.2` are supported. A real build exposing another arrangement requires a reviewed source correction in the same Delivery.
+
+Bounds are256 files/512MiB aggregate,256MiB per file,256 program headers,4096 dynamic entries,1MiB string metadata,128 dependencies and16 search directories per object. The admitted outer image operation still owns the original deadline, process custody and resource ceiling. This source does not establish loader precedence, inherited RPATH, cache/hardware-capability selection, symbol/version compatibility, dynamic `dlopen` populations or loaded ABI. `loadedAbiAccepted` remains false. Actual image creation/export/load/readback, static correspondence against that image, scoped retirement and native gameplay keep their separate acceptance requirements and the existing old-writer/NVMe resource hold.
+
+`python3 containers/barc-stock-headless/test_source.py` exercises the production collector with authored ELF bytes, including recursive closure, digest drift, missing/ambiguous dependencies, confinement, cycles, alias changes and bounded populations. One bounded `readelf` invocation independently checks an authored fixture; no fixture is compiled or executed. These controls establish source behavior, not a qualified image.
+
 ## Build and runtime boundaries
 
 `python3 containers/barc-stock-headless/build-image.py --mode preflight` performs inert data-only pin/shape checks before any image pull. After existing machine admission, use the repository root as the container context and this Containerfile. No toolchain build arguments are needed. Its default final stage acquires the full selected engine/game/map runtime. `--target development` is available for source/plugin work. Image creation does not run spring-headless or invent a native acceptance attempt.
diff --git a/containers/barc-stock-headless/build-image.py b/containers/barc-stock-headless/build-image.py
index 5e05841..b49785e 100644
--- a/containers/barc-stock-headless/build-image.py
+++ b/containers/barc-stock-headless/build-image.py
@@ -47,6 +47,150 @@ def sha(path, maximum):
             result.update(block)
     return result.hexdigest()
 
+def elf_metadata(path):
+    """Read bounded ELF64 metadata as data; never invoke a loader or the file."""
+    require(path.is_file() and not path.is_symlink(), 'ELF input must be a regular unlinked file')
+    size = path.stat().st_size
+    require(64 <= size <= 256 * 1024 * 1024, 'ELF file byte budget exceeded')
+    with path.open('rb') as stream:
+        def read(offset, count):
+            require(0 <= offset <= size and 0 <= count <= 1024 * 1024 and offset + count <= size,
+                    'truncated or excessive ELF metadata')
+            stream.seek(offset); value = stream.read(count)
+            require(len(value) == count, 'ELF changed during metadata read')
+            return value
+        header = struct.unpack('<16sHHIQQQIHHHHHH', read(0, 64))
+        require(header[0][:7] == b'\x7fELF\x02\x01\x01' and header[0][7] in (0, 3) and header[1] in (2, 3)
+                and header[2:4] == (62, 1) and header[8] == 64,
+                'only executable/shared ELF64 little-endian x86-64 is supported')
+        require(header[5] >= 64 and header[9] == 56 and 0 < header[10] <= 256, 'unsupported ELF program-header population')
+        segments = [struct.unpack('<IIQQQQQQ', read(header[5] + index * 56, 56))
+                    for index in range(header[10])]
+        for segment in segments:
+            require(segment[2] + segment[5] <= size and segment[5] <= segment[6], 'invalid ELF segment bounds')
+        dynamic = [s for s in segments if s[0] == 2]
+        interpreters = [s for s in segments if s[0] == 3]
+        require(len(dynamic) == 1 and len(interpreters) <= 1, 'one dynamic segment and at most one interpreter required')
+        interpreter = None
+        if interpreters:
+            value = read(interpreters[0][2], interpreters[0][5])
+            require(value == b'/lib64/ld-linux-x86-64.so.2\0', 'unsupported ELF interpreter')
+            interpreter = value[:-1].decode('ascii')
+        segment = dynamic[0]
+        containing = [s for s in segments if s[0] == 1 and s[2] <= segment[2]
+                      and segment[2] + segment[5] <= s[2] + s[5]
+                      and segment[3] - s[3] == segment[2] - s[2]]
+        require(len(containing) == 1, 'dynamic metadata is not in one corresponding load segment')
+        require(0 < segment[5] <= 4096 * 16 and segment[5] % 16 == 0, 'invalid dynamic metadata population')
+        tags = {}; terminated = False
+        for offset in range(segment[2], segment[2] + segment[5], 16):
+            tag, value = struct.unpack('<qQ', read(offset, 16))
+            if tag == 0:
+                terminated = True; break
+            tags.setdefault(tag, []).append(value)
+        require(terminated, 'unterminated ELF dynamic table')
+        # Audit/filter objects introduce another dependency mechanism. NODEFLIB
+        # changes the selected default-directory contract and is not supported.
+        require(not any(tag in tags for tag in (0x7fffffff, 0x7ffffffd, 0x6ffffefb, 0x6ffffefc)),
+                'unsupported ELF audit/filter dependency')
+        require(not any(value & 0x800 for value in tags.get(0x6ffffffb, [])), 'ELF NODEFLIB is unsupported')
+        for tag in (5, 10, 14, 15, 29):
+            require(len(tags.get(tag, [])) <= 1, 'duplicate singleton ELF metadata')
+        require(5 in tags and 10 in tags and 0 < tags[10][0] <= 1024 * 1024, 'bounded ELF string table required')
+        address, count = tags[5][0], tags[10][0]
+        loads = [s for s in segments if s[0] == 1 and s[3] <= address and address + count <= s[3] + s[5]]
+        require(len(loads) == 1, 'ambiguous or unmapped ELF string table')
+        strings = read(loads[0][2] + address - loads[0][3], count)
+        def string(index):
+            require(index < len(strings), 'ELF string offset outside table')
+            end = strings.find(b'\0', index)
+            require(index < end <= index + 4096, 'unterminated or excessive ELF string')
+            return strings[index:end].decode('ascii')
+        needed = [string(index) for index in tags.get(1, [])]
+        require(len(needed) <= 128 and len(set(needed)) == len(needed), 'duplicate/excessive ELF dependencies')
+        soname = string(tags[14][0]) if 14 in tags else None
+        for name in needed + ([soname] if soname else []):
+            require(bool(re.fullmatch(r'[A-Za-z0-9_+.-]+', name)) and name not in ('.', '..'), 'unsupported ELF library name')
+        require(not (15 in tags and 29 in tags), 'combined RPATH/RUNPATH is ambiguous')
+        paths = [string(tags[tag][0]) for tag in (15, 29) if tag in tags]
+        return {'class': 'ELF64', 'machine': 'x86-64', 'type': header[1], 'needed': needed,
+                'soname': soname, 'interpreter': interpreter, 'searchPath': paths[0] if paths else None,
+                'searchPathKind': 'RPATH' if 15 in tags else ('RUNPATH' if 29 in tags else None)}
+
+def static_elf_correspondence(image_root, engine, plugin):
+    """Closed image-local candidate correspondence, not dynamic-loader resolution."""
+    image_root = image_root.resolve(strict=True)
+    aliases = {}
+    def confined(path):
+        resolved = path.resolve(strict=True)
+        require(resolved.is_relative_to(image_root) and resolved.is_file(), 'ELF candidate escapes image or is nonregular')
+        require(path.is_relative_to(image_root), 'ELF input path escapes image')
+        aliases['/' + path.relative_to(image_root).as_posix()] = '/' + resolved.relative_to(image_root).as_posix()
+        return resolved
+    roots = {'engine': confined(engine), 'plugin': confined(plugin)}
+    pending = list(roots.values()); records = {}; total = 0
+    defaults = [image_root / path for path in ('lib/x86_64-linux-gnu', 'usr/lib/x86_64-linux-gnu', 'lib64', 'usr/lib64')]
+    while pending:
+        path = pending.pop(0)
+        key = '/' + path.relative_to(image_root).as_posix()
+        if key in records: continue
+        require(len(records) < 256, 'ELF dependency closure population exceeded')
+        total += path.stat().st_size
+        require(total <= 512 * 1024 * 1024, 'ELF dependency closure byte budget exceeded')
+        before = sha(path, 256 * 1024 * 1024); metadata = elf_metadata(path)
+        directories = [path.parent, *defaults]
+        if metadata['searchPath'] is not None:
+            entries = metadata['searchPath'].split(':')
+            require(len(entries) <= 16, 'ELF search-path population exceeded')
+            for entry in entries:
+                require(entry and (entry == '$ORIGIN' or entry.startswith('$ORIGIN/')),
+                        'only explicit ORIGIN-relative ELF search paths supported')
+                suffix = entry[len('$ORIGIN'):].lstrip('/')
+                require('$' not in suffix and '..' not in pathlib.PurePosixPath(suffix).parts,
+                        'unsupported ELF search-path expansion')
+                directory = (path.parent / suffix).resolve(strict=True)
+                require(directory.is_relative_to(image_root) and directory.is_dir(), 'ELF search directory escapes image')
+                directories.append(directory)
+        edges = []
+        for needed in metadata['needed']:
+            candidates = {confined(directory / needed) for directory in directories
+                          if (directory / needed).exists() or (directory / needed).is_symlink()}
+            require(len(candidates) == 1, 'missing or ambiguous ELF dependency: ' + needed)
+            candidate = candidates.pop()
+            edges.append({'needed': needed, 'path': '/' + candidate.relative_to(image_root).as_posix()})
+            pending.append(candidate)
+        if metadata['interpreter']:
+            candidate = confined(image_root / metadata['interpreter'].lstrip('/'))
+            edges.append({'interpreter': metadata['interpreter'], 'path': '/' + candidate.relative_to(image_root).as_posix()})
+            pending.append(candidate)
+        require(sha(path, 256 * 1024 * 1024) == before, 'ELF changed during correspondence')
+        records[key] = {'sha256': before, 'bytes': path.stat().st_size, 'metadata': metadata, 'dependencies': edges}
+    # A final sweep binds dependencies and both roots to one unchanged inventory.
+    for key, record in records.items():
+        require(sha(image_root / key.lstrip('/'), 256 * 1024 * 1024) == record['sha256'], 'ELF closure changed during collection')
+        for edge in record['dependencies']:
+            soname = records[edge['path']]['metadata']['soname']
+            require('needed' not in edge or soname is None or soname == edge['needed'], 'ELF dependency SONAME differs')
+    for selected, resolved in aliases.items():
+        require((image_root / selected.lstrip('/')).resolve(strict=True) == image_root / resolved.lstrip('/'),
+                'ELF dependency alias changed during collection')
+    return {'schema': 'bar-static-elf-correspondence/1', 'roots': {role: '/' + path.relative_to(image_root).as_posix() for role, path in roots.items()},
+            'files': records, 'aliases': aliases, 'loadedAbiAccepted': False,
+            'scope': 'ELF64 x86-64 image-local DT_NEEDED/interpreter candidate correspondence; not loader order, symbols, versions, dlopen or loaded ABI proof'}
+
+def retain_static_elf(output, image_root=pathlib.Path('/'), expected=None):
+    require(isinstance(expected, dict) and set(expected) == {'engine', 'plugin'}
+            and all(isinstance(value, str) and SHA.fullmatch(value) for value in expected.values()),
+            'exact expected engine/plugin digests required')
+    correspondence = static_elf_correspondence(image_root, output / 'engine/spring-headless', output / 'plugin/libSkirmishAI.so')
+    for role, digest in expected.items():
+        require(correspondence['files'][correspondence['roots'][role]]['sha256'] == digest,
+                'ELF root differs from selected digest: ' + role)
+    correspondence['expectedRoots'] = expected
+    with (output / 'STATIC-ELF.json').open('x') as stream:
+        json.dump(correspondence, stream, sort_keys=True, indent=2)
+        stream.write('\n')
+
 def run(command, seconds, *, env=None, cwd=None):
     subprocess.run(['timeout', '--kill-after=5s', str(seconds) + 's', *command], env=env, cwd=cwd, check=True)
 
@@ -285,6 +429,12 @@ def integrate(pins):
     engine_listing(archive, pins); (output / 'engine').mkdir()
     run(['7z', 'x', '-y', '-o' + str(output / 'engine'), str(archive)], 300)
     require(sha(output / 'engine/spring-headless', budget['engineExpandedMaxBytes']) == pins['engine']['headlessSha256'], 'headless binary differs')
+    # Validate and retain the produced engine/plugin dependency inventory before
+    # launching the downloader. No inspected ELF is executed by this check.
+    plugin_manifest = (output / 'PLUGIN.SHA256').read_text()
+    require(bool(re.fullmatch(r'[0-9a-f]{64}  /opt/barc/plugin/libSkirmishAI\.so\n', plugin_manifest)),
+            'plugin digest manifest differs')
+    retain_static_elf(output, expected={'engine': pins['engine']['headlessSha256'], 'plugin': plugin_manifest[:64]})
     # Retain the complete official engine payload; runtime entry is headless only.
     data = output / 'data'; (data / 'maps').mkdir(parents=True)
     acquire_file(pins['map']['url'], pins['map']['sha256'], data / 'maps' / pins['map']['file'], 300, budget['assetDownloadMaxBytes'])
diff --git a/containers/barc-stock-headless/test_source.py b/containers/barc-stock-headless/test_source.py
index e480780..c880261 100644
--- a/containers/barc-stock-headless/test_source.py
+++ b/containers/barc-stock-headless/test_source.py
@@ -16,6 +16,140 @@
 module = importlib.util.module_from_spec(spec); spec.loader.exec_module(module)
 pins = json.loads((root / 'resources.json').read_text())
 
+def elf_fixture(path, *, needed=(), soname=None, search=None, interpreter=False, extra=()):
+    """Small ELF bytes, authored as data. No compilation or fixture execution."""
+    strings = bytearray(b'\0'); tags = []
+    for tag, values in ((1, needed), (14, [soname] if soname else []), (29, [search] if search is not None else [])):
+        for value in values:
+            tags.append((tag, len(strings))); strings.extend(value.encode('ascii') + b'\0')
+    tags = [(5, 0x400), (10, len(strings)), *tags, *extra, (0, 0)]
+    data = bytearray(4096)
+    data[:64] = struct.pack('<16sHHIQQQIHHHHHH', b'\x7fELF\x02\x01\x01' + bytes(9), 3, 62, 1, 0, 64, 0, 0, 64, 56, 3 if interpreter else 2, 0, 0, 0)
+    data[64:120] = struct.pack('<IIQQQQQQ', 1, 4, 0, 0, 0, len(data), len(data), 4096)
+    data[120:176] = struct.pack('<IIQQQQQQ', 2, 4, 0x100, 0x100, 0, len(tags)*16, len(tags)*16, 8)
+    if interpreter:
+        value = b'/lib64/ld-linux-x86-64.so.2\0'
+        data[176:232] = struct.pack('<IIQQQQQQ', 3, 4, 0x800, 0x800, 0, len(value), len(value), 1)
+        data[0x800:0x800+len(value)] = value
+    for index, pair in enumerate(tags): data[0x100+index*16:0x110+index*16] = struct.pack('<qQ', *pair)
+    data[0x400:0x400+len(strings)] = strings
+    path.parent.mkdir(parents=True, exist_ok=True); path.write_bytes(data)
+    return path
+
+class StaticElfTests(unittest.TestCase):
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory(); self.addCleanup(self.temp.cleanup)
+        self.image = pathlib.Path(self.temp.name)
+        self.output = self.image / 'opt/barc'
+        self.engine = elf_fixture(self.output/'engine/spring-headless', needed=['liba.so'], interpreter=True)
+        self.plugin = elf_fixture(self.output/'plugin/libSkirmishAI.so', needed=['liba.so'])
+        self.liba = elf_fixture(self.image/'usr/lib/x86_64-linux-gnu/liba.so', soname='liba.so', needed=['libb.so'])
+        self.libb = elf_fixture(self.image/'usr/lib/x86_64-linux-gnu/libb.so', soname='libb.so')
+        self.loader = elf_fixture(self.image/'lib64/ld-linux-x86-64.so.2')
+    def collect(self):
+        return module.static_elf_correspondence(self.image, self.engine, self.plugin)
+    def expected(self):
+        return {role: hashlib.sha256(path.read_bytes()).hexdigest() for role, path in [('engine', self.engine), ('plugin', self.plugin)]}
+    def test_production_retention_has_recursive_hashes_and_never_executes(self):
+        with mock.patch.object(module.subprocess, 'run', side_effect=AssertionError('execution forbidden')), mock.patch.object(module.subprocess, 'Popen', side_effect=AssertionError('execution forbidden')):
+            module.retain_static_elf(self.output, self.image, self.expected())
+        result = json.loads((self.output/'STATIC-ELF.json').read_text())
+        self.assertEqual(len(result['files']), 5)
+        self.assertFalse(result['loadedAbiAccepted'])
+        self.assertEqual(result['roots']['engine'], '/opt/barc/engine/spring-headless')
+        for name, record in result['files'].items():
+            self.assertEqual(record['sha256'], hashlib.sha256((self.image/name.lstrip('/')).read_bytes()).hexdigest())
+        original = (self.output/'STATIC-ELF.json').read_bytes()
+        with self.assertRaises(FileExistsError): module.retain_static_elf(self.output, self.image, self.expected())
+        self.assertEqual(original, (self.output/'STATIC-ELF.json').read_bytes())
+    def test_missing_transitive_dependency_never_retains_success(self):
+        self.libb.unlink()
+        with self.assertRaisesRegex(ValueError, 'missing or ambiguous'): module.retain_static_elf(self.output, self.image, self.expected())
+        self.assertFalse((self.output/'STATIC-ELF.json').exists())
+    def test_selected_root_digest_drift_refuses_retention(self):
+        expected = self.expected(); expected['engine'] = '0'*64
+        with self.assertRaisesRegex(ValueError, 'selected digest'): module.retain_static_elf(self.output, self.image, expected)
+        self.assertFalse((self.output/'STATIC-ELF.json').exists())
+    def test_real_readelf_agrees_on_authored_nonexecuted_fixture(self):
+        inspected = subprocess.run(['readelf', '--file-header', '--dynamic', '--wide', str(self.engine)],
+                                   stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=5,
+                                   env={'PATH': '/usr/bin:/bin', 'LC_ALL': 'C'})
+        self.assertEqual(inspected.returncode, 0, inspected.stderr)
+        self.assertLess(len(inspected.stdout) + len(inspected.stderr), 16384)
+        self.assertIn(b'ELF64', inspected.stdout)
+        self.assertIn(b'Advanced Micro Devices X86-64', inspected.stdout)
+        self.assertIn(b'Shared library: [liba.so]', inspected.stdout)
+        self.assertEqual(module.elf_metadata(self.engine)['needed'], ['liba.so'])
+    def test_distinct_duplicate_refused_even_with_identical_bytes(self):
+        duplicate = self.image/'lib64/libb.so'; duplicate.write_bytes(self.libb.read_bytes())
+        with self.assertRaisesRegex(ValueError, 'ambiguous'): self.collect()
+    def test_system_aliases_deduplicate_and_are_retained(self):
+        (self.image/'lib').symlink_to('usr/lib', target_is_directory=True)
+        result = self.collect()
+        self.assertEqual(len(result['files']), 5)
+        self.assertEqual(result['aliases']['/lib/x86_64-linux-gnu/liba.so'], '/usr/lib/x86_64-linux-gnu/liba.so')
+    def test_dependency_link_outside_image_refused(self):
+        self.libb.unlink(); self.libb.symlink_to('/etc/passwd')
+        with self.assertRaisesRegex(ValueError, 'escapes image'): self.collect()
+    def test_soname_mismatch_refused(self):
+        elf_fixture(self.libb, soname='libwrong.so')
+        with self.assertRaisesRegex(ValueError, 'SONAME differs'): self.collect()
+    def test_duplicate_and_path_needed_names_are_refused(self):
+        for needed in (['libb.so', 'libb.so'], ['../libb.so'], ['/lib/libb.so']):
+            with self.subTest(needed=needed):
+                elf_fixture(self.liba, needed=needed)
+                with self.assertRaises(ValueError): self.collect()
+    def test_closure_population_is_bounded(self):
+        for index in range(255):
+            elf_fixture(self.liba.parent/f'lib{index}.so', needed=[f'lib{index+1}.so'] if index < 254 else [])
+        elf_fixture(self.liba, soname='liba.so', needed=['lib0.so'])
+        with self.assertRaisesRegex(ValueError, 'closure population'): self.collect()
+    def test_alias_retarget_during_collection_refuses(self):
+        alias = self.image/'lib64/liba.so'; alias.symlink_to(self.liba)
+        replacement = elf_fixture(self.image/'spare/liba.so', soname='liba.so', needed=['libb.so'])
+        original = module.sha; calls = []
+        def change(path, maximum):
+            result = original(path, maximum); calls.append(path)
+            if path == self.libb and calls.count(path) == 2:
+                alias.unlink(); alias.symlink_to(replacement)
+            return result
+        with mock.patch.object(module, 'sha', side_effect=change), self.assertRaisesRegex(ValueError, 'alias changed'): self.collect()
+    def test_cycles_terminate_without_omitting_edges(self):
+        elf_fixture(self.libb, soname='libb.so', needed=['liba.so'])
+        result = self.collect()
+        self.assertEqual(len(result['files']), 5)
+        self.assertEqual(result['files']['/usr/lib/x86_64-linux-gnu/libb.so']['dependencies'][0]['needed'], 'liba.so')
+    def test_origin_directory_and_unsupported_search_semantics(self):
+        self.libb.unlink(); elf_fixture(self.liba.parent/'private/libb.so', soname='libb.so')
+        elf_fixture(self.liba, soname='liba.so', needed=['libb.so'], search='$ORIGIN/private')
+        self.assertEqual(len(self.collect()['files']), 5)
+        for value in ('', '/host/lib', '$ORIGIN/../escape', '$LIB', '$ORIGIN:'):
+            with self.subTest(value=value):
+                elf_fixture(self.liba, soname='liba.so', needed=['libb.so'], search=value)
+                with self.assertRaises(ValueError): self.collect()
+    def test_changed_closure_refuses_final_sweep(self):
+        original = module.sha; calls = []
+        def change(path, maximum):
+            result = original(path, maximum); calls.append(path)
+            if path == self.libb and calls.count(path) == 2:
+                data = bytearray(self.engine.read_bytes()); data[-1] ^= 1; self.engine.write_bytes(data)
+            return result
+        with mock.patch.object(module, 'sha', side_effect=change), self.assertRaisesRegex(ValueError, 'closure changed'): self.collect()
+    def test_malformed_metadata_and_unsupported_dynamic_features(self):
+        original = self.libb.read_bytes()
+        mutations = [(4, b'\x01'), (5, b'\x02'), (18, b'\xb7\x00'), (54, b'\x00\x00'),
+                     (56, b'\xff\xff'), (0x108, struct.pack('<Q', 0xffffffffffffffff))]
+        for offset, value in mutations:
+            with self.subTest(offset=offset):
+                data = bytearray(original); data[offset:offset+len(value)] = value; self.libb.write_bytes(data)
+                with self.assertRaises(ValueError): self.collect()
+        for tags in ([(5, 0x400)], [(0x7fffffff, 0)], [(0x6ffffffb, 0x800)]):
+            with self.subTest(tags=tags):
+                elf_fixture(self.libb, extra=tags)
+                with self.assertRaises(ValueError): self.collect()
+        self.libb.write_bytes(original[:200])
+        with self.assertRaises(ValueError): self.collect()
+
 class ImageSourceTests(unittest.TestCase):
     def test_missing_unwind_is_refused_before_source_acquisition(self):
         with mock.patch.object(module.shutil, 'which', return_value='/fixture/tool'), mock.patch.object(module, 'run', side_effect=subprocess.CalledProcessError(1, ['pkg-config'])), mock.patch.object(module, 'source') as acquire:

From 2b876935bb13ac24ba26facc94f8385a1d19a3e7 Mon Sep 17 00:00:00 2001
From: EHotwagner <ehotwagner@gmail.com>
Date: Tue, 20 Oct 2026 23:10:18 +0200
Subject: [PATCH 2/2] Bind bounded ELF reads and preserve repeated alias
 identities

---
 containers/barc-stock-headless/README.md      |  2 +-
 containers/barc-stock-headless/build-image.py | 60 ++++++++++++++-----
 containers/barc-stock-headless/test_source.py | 44 ++++++++++++--
 3 files changed, 86 insertions(+), 20 deletions(-)

diff --git a/containers/barc-stock-headless/README.md b/containers/barc-stock-headless/README.md
index 3c44b6f..d37fe08 100644
--- a/containers/barc-stock-headless/README.md
+++ b/containers/barc-stock-headless/README.md
@@ -37,7 +37,7 @@ Before the integration stage launches the downloader, it writes `/opt/barc/STATI
 
 This is a deliberately limited image-local **candidate correspondence**, not the dynamic loader's search algorithm. Candidate directories are each object's directory, its explicit `$ORIGIN`-relative RPATH or RUNPATH, and the fixed image directories `/lib/x86_64-linux-gnu`, `/usr/lib/x86_64-linux-gnu`, `/lib64` and `/usr/lib64`. Aliases to the same canonical file deduplicate; distinct candidates refuse even when their bytes match. Missing dependencies, escaping or changing aliases, SONAME mismatches, malformed ELF, audit/filter dependencies, NODEFLIB, combined RPATH/RUNPATH and unsupported path expansions refuse. Only little-endian ELF64 x86-64 executables/shared objects and `/lib64/ld-linux-x86-64.so.2` are supported. A real build exposing another arrangement requires a reviewed source correction in the same Delivery.
 
-Bounds are256 files/512MiB aggregate,256MiB per file,256 program headers,4096 dynamic entries,1MiB string metadata,128 dependencies and16 search directories per object. The admitted outer image operation still owns the original deadline, process custody and resource ceiling. This source does not establish loader precedence, inherited RPATH, cache/hardware-capability selection, symbol/version compatibility, dynamic `dlopen` populations or loaded ABI. `loadedAbiAccepted` remains false. Actual image creation/export/load/readback, static correspondence against that image, scoped retirement and native gameplay keep their separate acceptance requirements and the existing old-writer/NVMe resource hold.
+Bounds are256 files/512MiB aggregate,256MiB per file,256 program headers,4096 dynamic entries,1MiB string metadata/2MiB cumulative metadata reads,128 dependencies and16 search directories per object. Hashing charges actual accepted bytes and reads at most the initially admitted descriptor size. Nonblocking/no-follow opens, regular-file descriptor checks and before/after descriptor/path identity checks refuse growing, replaced or nonregular inputs. Repeated alias lookups must retain the original resolution. The admitted outer image operation still owns the original deadline, process custody and resource ceiling. This source does not establish loader precedence, inherited RPATH, cache/hardware-capability selection, symbol/version compatibility, dynamic `dlopen` populations or loaded ABI. `loadedAbiAccepted` remains false. Actual image creation/export/load/readback, static correspondence against that image, scoped retirement and native gameplay keep their separate acceptance requirements and the existing old-writer/NVMe resource hold.
 
 `python3 containers/barc-stock-headless/test_source.py` exercises the production collector with authored ELF bytes, including recursive closure, digest drift, missing/ambiguous dependencies, confinement, cycles, alias changes and bounded populations. One bounded `readelf` invocation independently checks an authored fixture; no fixture is compiled or executed. These controls establish source behavior, not a qualified image.
 
diff --git a/containers/barc-stock-headless/build-image.py b/containers/barc-stock-headless/build-image.py
index b49785e..dc66c58 100644
--- a/containers/barc-stock-headless/build-image.py
+++ b/containers/barc-stock-headless/build-image.py
@@ -10,6 +10,8 @@
 import re
 import shutil
 import subprocess
+import contextlib
+import stat
 
 ROOT = pathlib.Path(__file__).resolve().parent
 SHA = re.compile(r'[0-9a-f]{64}')
@@ -38,25 +40,49 @@ def check_inputs(pins):
     require(pins['game']['name'] == 'Beyond All Reason test-29926-0571aa8', 'moving/unselected game name refused')
     require(pins['game']['sdp'] == '7fd33d9ceb79c052065b8d3c2f6f2687.sdp', 'game package identity differs')
 
-def sha(path, maximum):
-    require(path.is_file() and not path.is_symlink(), 'missing/linked input: ' + str(path))
-    require(path.stat().st_size <= maximum, 'input exceeds byte budget: ' + str(path))
-    result = hashlib.sha256()
-    with path.open('rb') as stream:
-        while block := stream.read(1024 * 1024):
+def file_identity(info):
+    return (info.st_dev, info.st_ino, info.st_size, info.st_mtime_ns, info.st_ctime_ns)
+
+@contextlib.contextmanager
+def regular_input(path, maximum):
+    # NONBLOCK prevents a raced FIFO from blocking open before the fstat check.
+    require(not path.is_symlink(), 'linked input refused')
+    descriptor = os.open(path, os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK)
+    with os.fdopen(descriptor, 'rb') as stream:
+        before = os.fstat(stream.fileno())
+        require(stat.S_ISREG(before.st_mode) and before.st_size <= maximum, 'input is nonregular or exceeds byte budget')
+        require(file_identity(path.lstat()) == file_identity(before), 'input replaced before read')
+        yield stream, before.st_size
+        require(file_identity(os.fstat(stream.fileno())) == file_identity(before)
+                and file_identity(path.lstat()) == file_identity(before), 'input grew or was replaced during read')
+
+def file_digest(path, maximum):
+    result = hashlib.sha256(); count = 0
+    with regular_input(path, maximum) as (stream, size):
+        while count < size:
+            block = stream.read(min(1024 * 1024, size - count))
+            require(bool(block), 'input truncated during read')
+            count += len(block)
+            require(count <= maximum, 'input read exceeds byte budget')
             result.update(block)
-    return result.hexdigest()
+        require(count == size, 'input size changed during read')
+    return result.hexdigest(), count
+
+def sha(path, maximum):
+    return file_digest(path, maximum)[0]
 
 def elf_metadata(path):
     """Read bounded ELF64 metadata as data; never invoke a loader or the file."""
-    require(path.is_file() and not path.is_symlink(), 'ELF input must be a regular unlinked file')
-    size = path.stat().st_size
-    require(64 <= size <= 256 * 1024 * 1024, 'ELF file byte budget exceeded')
-    with path.open('rb') as stream:
+    with regular_input(path, 256 * 1024 * 1024) as (stream, size):
+        require(size >= 64, 'truncated ELF file')
+        metadata_bytes = 0
         def read(offset, count):
+            nonlocal metadata_bytes
             require(0 <= offset <= size and 0 <= count <= 1024 * 1024 and offset + count <= size,
                     'truncated or excessive ELF metadata')
+            require(metadata_bytes + count <= 2 * 1024 * 1024, 'ELF cumulative metadata read budget exceeded')
             stream.seek(offset); value = stream.read(count)
+            metadata_bytes += len(value)
             require(len(value) == count, 'ELF changed during metadata read')
             return value
         header = struct.unpack('<16sHHIQQQIHHHHHH', read(0, 64))
@@ -125,7 +151,10 @@ def confined(path):
         resolved = path.resolve(strict=True)
         require(resolved.is_relative_to(image_root) and resolved.is_file(), 'ELF candidate escapes image or is nonregular')
         require(path.is_relative_to(image_root), 'ELF input path escapes image')
-        aliases['/' + path.relative_to(image_root).as_posix()] = '/' + resolved.relative_to(image_root).as_posix()
+        selected = '/' + path.relative_to(image_root).as_posix()
+        destination = '/' + resolved.relative_to(image_root).as_posix()
+        require(selected not in aliases or aliases[selected] == destination, 'ELF dependency alias changed between lookups')
+        aliases[selected] = destination
         return resolved
     roots = {'engine': confined(engine), 'plugin': confined(plugin)}
     pending = list(roots.values()); records = {}; total = 0
@@ -135,9 +164,10 @@ def confined(path):
         key = '/' + path.relative_to(image_root).as_posix()
         if key in records: continue
         require(len(records) < 256, 'ELF dependency closure population exceeded')
-        total += path.stat().st_size
+        before, accepted_bytes = file_digest(path, min(256 * 1024 * 1024, 512 * 1024 * 1024 - total))
+        total += accepted_bytes
         require(total <= 512 * 1024 * 1024, 'ELF dependency closure byte budget exceeded')
-        before = sha(path, 256 * 1024 * 1024); metadata = elf_metadata(path)
+        metadata = elf_metadata(path)
         directories = [path.parent, *defaults]
         if metadata['searchPath'] is not None:
             entries = metadata['searchPath'].split(':')
@@ -164,7 +194,7 @@ def confined(path):
             edges.append({'interpreter': metadata['interpreter'], 'path': '/' + candidate.relative_to(image_root).as_posix()})
             pending.append(candidate)
         require(sha(path, 256 * 1024 * 1024) == before, 'ELF changed during correspondence')
-        records[key] = {'sha256': before, 'bytes': path.stat().st_size, 'metadata': metadata, 'dependencies': edges}
+        records[key] = {'sha256': before, 'bytes': accepted_bytes, 'metadata': metadata, 'dependencies': edges}
     # A final sweep binds dependencies and both roots to one unchanged inventory.
     for key, record in records.items():
         require(sha(image_root / key.lstrip('/'), 256 * 1024 * 1024) == record['sha256'], 'ELF closure changed during collection')
diff --git a/containers/barc-stock-headless/test_source.py b/containers/barc-stock-headless/test_source.py
index c880261..c635b52 100644
--- a/containers/barc-stock-headless/test_source.py
+++ b/containers/barc-stock-headless/test_source.py
@@ -5,6 +5,7 @@
 import importlib.util
 import json
 import pathlib
+import os
 import struct
 import subprocess
 import tempfile
@@ -107,13 +108,48 @@ def test_closure_population_is_bounded(self):
     def test_alias_retarget_during_collection_refuses(self):
         alias = self.image/'lib64/liba.so'; alias.symlink_to(self.liba)
         replacement = elf_fixture(self.image/'spare/liba.so', soname='liba.so', needed=['libb.so'])
-        original = module.sha; calls = []
+        original = module.file_digest; calls = []
         def change(path, maximum):
             result = original(path, maximum); calls.append(path)
             if path == self.libb and calls.count(path) == 2:
                 alias.unlink(); alias.symlink_to(replacement)
             return result
-        with mock.patch.object(module, 'sha', side_effect=change), self.assertRaisesRegex(ValueError, 'alias changed'): self.collect()
+        with mock.patch.object(module, 'file_digest', side_effect=change), self.assertRaisesRegex(ValueError, 'alias changed'): self.collect()
+    def test_alias_retarget_between_repeated_lookups_refuses(self):
+        target = self.image/'spare/liba.so'
+        target.parent.mkdir(); self.liba.rename(target); self.liba.symlink_to(target)
+        replacement = elf_fixture(self.image/'other/liba.so', soname='liba.so', needed=['libb.so'])
+        original = module.elf_metadata
+        def change(path):
+            if path == self.plugin:
+                self.liba.unlink(); self.liba.symlink_to(replacement)
+            return original(path)
+        with mock.patch.object(module, 'elf_metadata', side_effect=change), self.assertRaisesRegex(ValueError, 'between lookups'): self.collect()
+    def test_growing_hash_input_is_bounded_during_actual_read(self):
+        path = self.image/'growing'; path.write_bytes(b'abcd'); original = module.os.fdopen; requested = []
+        class Reader:
+            def __init__(self, stream): self.stream = stream
+            def __enter__(self): return self
+            def __exit__(self, *args): self.stream.close()
+            def fileno(self): return self.stream.fileno()
+            def read(self, count):
+                requested.append(count)
+                with path.open('ab') as writer: writer.write(b'x'*100)
+                return self.stream.read(count)
+        with mock.patch.object(module.os, 'fdopen', side_effect=lambda *args: Reader(original(*args))):
+            with self.assertRaisesRegex(ValueError, 'grew or was replaced'): module.file_digest(path, 8)
+        self.assertEqual(requested, [4])
+    def test_replaced_file_after_open_is_refused(self):
+        path = self.image/'replaced'; path.write_bytes(b'old'); original = module.os.fdopen
+        def replace(*args):
+            stream = original(*args); path.unlink(); path.write_bytes(b'new'); return stream
+        with mock.patch.object(module.os, 'fdopen', side_effect=replace), self.assertRaisesRegex(ValueError, 'replaced before read'):
+            module.file_digest(path, 8)
+    def test_nonregular_and_linked_hash_inputs_refuse_without_blocking(self):
+        path = self.image/'fifo'; os.mkfifo(path)
+        with self.assertRaisesRegex(ValueError, 'nonregular'): module.file_digest(path, 8)
+        path.unlink(); path.symlink_to(self.libb)
+        with self.assertRaises((ValueError, OSError)): module.file_digest(path, 8192)
     def test_cycles_terminate_without_omitting_edges(self):
         elf_fixture(self.libb, soname='libb.so', needed=['liba.so'])
         result = self.collect()
@@ -128,13 +164,13 @@ def test_origin_directory_and_unsupported_search_semantics(self):
                 elf_fixture(self.liba, soname='liba.so', needed=['libb.so'], search=value)
                 with self.assertRaises(ValueError): self.collect()
     def test_changed_closure_refuses_final_sweep(self):
-        original = module.sha; calls = []
+        original = module.file_digest; calls = []
         def change(path, maximum):
             result = original(path, maximum); calls.append(path)
             if path == self.libb and calls.count(path) == 2:
                 data = bytearray(self.engine.read_bytes()); data[-1] ^= 1; self.engine.write_bytes(data)
             return result
-        with mock.patch.object(module, 'sha', side_effect=change), self.assertRaisesRegex(ValueError, 'closure changed'): self.collect()
+        with mock.patch.object(module, 'file_digest', side_effect=change), self.assertRaisesRegex(ValueError, 'closure changed'): self.collect()
     def test_malformed_metadata_and_unsupported_dynamic_features(self):
         original = self.libb.read_bytes()
         mutations = [(4, b'\x01'), (5, b'\x02'), (18, b'\xb7\x00'), (54, b'\x00\x00'),