From fdcf1db29073f2a9d200b668903897437537744c Mon Sep 17 00:00:00 2001
From: Jeffrey Wong <guineapig9@gmail.com>
Date: Tue, 20 Oct 2026 17:00:04 -0500
Subject: [PATCH] Build: keep the hash-pinned model guard libraries instead of
 recompiling them

---
 .../models/runtime_bridge/SConscript          | 23 +++++-
 .../models/tests/test_runtime_bridge_build.py | 76 +++++++++++++++++++
 prebuilt.json                                 |  2 +-
 3 files changed, 98 insertions(+), 3 deletions(-)
 create mode 100644 openpilot/starpilot/models/tests/test_runtime_bridge_build.py

diff --git a/openpilot/starpilot/models/runtime_bridge/SConscript b/openpilot/starpilot/models/runtime_bridge/SConscript
index e92eda4c50..c71d1daad6 100644
--- a/openpilot/starpilot/models/runtime_bridge/SConscript
+++ b/openpilot/starpilot/models/runtime_bridge/SConscript
@@ -37,6 +37,25 @@ if arch == 'comma_arm64':
     SHCCFLAGS=['$CCFLAGS', '-fPIC'], SHCFLAGS=['$CFLAGS'],
     SHLINKFLAGS=['$LINKFLAGS', '-shared'],
   )
-  guard_env.SharedLibrary('bounded_wait', ['bounded_wait.c'])
-  guard_env.SharedLibrary('usb_guards', ['usb_guards.c'])
+  # guard-policy.json pins both libraries by SHA-256 and the tree ships them built. A device build that recompiles
+  # them writes different bytes over the tracked files, and the guard then stops modeld, dmonitoringmodeld and
+  # controlsd at import ("Model submission guard source/artifact changed"). Keep the shipped libraries while they
+  # match the policy; rebuild only when they do not, which the guard then refuses at runtime.
+  import hashlib
+  import json
+  import os
+  here = Dir('.').srcnode().abspath
+  with open(os.path.join(here, 'guard-policy.json'), 'rb') as policy_file:
+    pinned = json.load(policy_file)['files']
+
+  def shipped(name):
+    path = os.path.join(here, name)
+    if os.path.islink(path) or not os.path.isfile(path):
+      return False
+    with open(path, 'rb') as library:
+      return hashlib.sha256(library.read()).hexdigest() == pinned.get(name)
+
+  if not (shipped('libbounded_wait.so') and shipped('libusb_guards.so')):
+    guard_env.SharedLibrary('bounded_wait', ['bounded_wait.c'])
+    guard_env.SharedLibrary('usb_guards', ['usb_guards.c'])
   Return('guard_env')
diff --git a/openpilot/starpilot/models/tests/test_runtime_bridge_build.py b/openpilot/starpilot/models/tests/test_runtime_bridge_build.py
new file mode 100644
index 0000000000..fcdb421afc
--- /dev/null
+++ b/openpilot/starpilot/models/tests/test_runtime_bridge_build.py
@@ -0,0 +1,76 @@
+"""The guard libraries are pinned by hash; a device build must not overwrite them. Fake SCons nodes, no compilers."""
+
+import hashlib
+import json
+import shutil
+import sys
+from pathlib import Path
+from types import ModuleType, SimpleNamespace
+from unittest.mock import Mock
+
+import pytest
+
+BRIDGE = Path(__file__).resolve().parents[1] / "runtime_bridge"
+SOURCE = BRIDGE / "SConscript"
+LIBRARIES = ("libbounded_wait.so", "libusb_guards.so")
+
+
+class Returned(Exception):
+  pass
+
+
+def evaluate(directory, arch="comma_arm64"):
+  env = Mock()
+  env.subst_list.return_value = []
+  guard_env = env.Clone.return_value
+
+  def stop(*_):
+    raise Returned()
+
+  scope = {"env": env, "arch": arch, "Import": Mock(), "Return": stop,
+           "Dir": lambda _: SimpleNamespace(srcnode=lambda: SimpleNamespace(abspath=str(directory)))}
+  try:
+    exec(compile(SOURCE.read_text(), str(SOURCE), "exec"), scope)
+  except Returned:
+    pass
+  return guard_env
+
+
+@pytest.fixture(autouse=True)
+def fake_scons(monkeypatch):
+  errors = ModuleType("SCons.Errors")
+  errors.UserError = type("UserError", (Exception,), {})
+  monkeypatch.setitem(sys.modules, "SCons", ModuleType("SCons"))
+  monkeypatch.setitem(sys.modules, "SCons.Errors", errors)
+
+
+@pytest.fixture
+def bridge(tmp_path):
+  for name in ("guard-policy.json", "bounded_wait.c", "usb_guards.c", *LIBRARIES):
+    shutil.copy(BRIDGE / name, tmp_path / name)
+  return tmp_path
+
+
+def test_shipped_libraries_match_the_policy_that_pins_them():
+  pinned = json.loads((BRIDGE / "guard-policy.json").read_bytes())["files"]
+  for name in LIBRARIES:
+    assert hashlib.sha256((BRIDGE / name).read_bytes()).hexdigest() == pinned[name]
+
+
+def test_matching_shipped_libraries_are_kept_not_rebuilt(bridge):
+  assert not evaluate(bridge).SharedLibrary.called
+
+
+@pytest.mark.parametrize("damage", ("changed", "missing"))
+@pytest.mark.parametrize("name", LIBRARIES)
+def test_a_changed_or_missing_library_is_rebuilt_so_the_guard_can_refuse_it(bridge, name, damage):
+  if damage == "changed":
+    (bridge / name).write_bytes((bridge / name).read_bytes() + b"\0")
+  else:
+    (bridge / name).unlink()
+  built = [call.args[0] for call in evaluate(bridge).SharedLibrary.call_args_list]
+  assert built == ["bounded_wait", "usb_guards"]
+
+
+def test_other_architectures_build_nothing(bridge):
+  assert not evaluate(bridge, arch="x86_64").SharedLibrary.called
diff --git a/prebuilt.json b/prebuilt.json
index 03e08c28b9..c3179870c1 100644
--- a/prebuilt.json
+++ b/prebuilt.json
@@ -1 +1 @@
-{"protected_inventory_sha256": "71d6cd3d1f42bd080c70cfabdbe93c972864379046240463577c088502bb51fc", "schema_version": 1}
+{"protected_inventory_sha256": "6013e0dc92e1a20be5b399fbd91223b040722469e22c0bfb9d79dd65ea0956f0", "schema_version": 1}