fix: let pinned executables through validate_pr

An executable is refused unless an emulator profile pins its exact bytes by sha1 or sha256. PICO-8's pico8.exe and SDL2.dll, from the official 0.2.7 archive, are pinned by the lexaloffle profile; md5 and crc32 never vouch for code.

scripts/validate_pr.py

@@ -422,8 +422,7 @@ def validate_file(
     result.crc32 = hashes["crc32"]
 
     ext = os.path.splitext(filepath)[1].lower()
-    if ext in BLOCKED_EXTENSIONS:
-        result.add_check(False, f"Blocked file extension: {ext}")
+    blocked = ext in BLOCKED_EXTENSIONS
 
     too_large = result.size > MAX_FILE_SIZE
     if too_large:
@@ -495,6 +494,22 @@ def validate_file(
         or profile_hashes.get("crc32", {}).get((result.crc32, None))
     )
 
+    if blocked:
+        # An executable is refused unless an emulator profile pins its exact
+        # bytes: PICO-8's pico8.exe and SDL2.dll are declared by sha1 from the
+        # official archive. A weak hash (md5, crc32) never vouches for code.
+        pinned = (
+            profile_hashes.get("sha1", {}).get(result.sha1)
+            or profile_hashes.get("sha256", {}).get(hashes.get("sha256", ""))
+        )
+        if pinned:
+            result.add_check(
+                True,
+                f"Executable whose bytes an emulator profile pins by sha1: {', '.join(sorted(pinned))}",
+            )
+        else:
+            result.add_check(False, f"Blocked file extension: {ext}")
+
     # The files of a ZIP no list declares whole, when the upload is one.
     members: list[str] | None = None
     if sha1_known:

tests/test_validate_pr.py

@@ -79,6 +79,26 @@ class FileShapeChecks(_Fixture):
         self.assertFalse(result.passed)
         self.assertIn("Blocked file extension", result.to_markdown())
 
+    def test_an_executable_a_profile_pins_by_sha1_passes(self):
+        """PICO-8's pico8.exe and SDL2.dll come from the official archive and
+        the lexaloffle profile pins their sha1: known bytes, not a payload."""
+        import hashlib
+        data = b"MZ pinned"
+        rel = self._bios_file("bios/Lexaloffle/PICO-8/pico8.exe", data)
+        pins = {"sha1": {hashlib.sha1(data).hexdigest(): {"lexaloffle"}}}
+        result = validate_pr.validate_file(rel, None, EMPTY_HASHES, pins)
+        self.assertNotIn("Blocked file extension", result.to_markdown())
+        self.assertIn("pins by sha1: lexaloffle", result.to_markdown())
+
+    def test_an_executable_known_only_by_md5_stays_refused(self):
+        import hashlib
+        data = b"MZ weak"
+        rel = self._bios_file("bios/Sony/PS/tool.exe", data)
+        pins = {"md5": {hashlib.md5(data).hexdigest(): {"someemu"}}}
+        result = validate_pr.validate_file(rel, None, EMPTY_HASHES, pins)
+        self.assertFalse(result.passed)
+        self.assertIn("Blocked file extension", result.to_markdown())
+
     def test_oversized_file_is_refused(self):
         rel = self._bios_file("bios/Sony/PS/big.bin")
         original = validate_pr.MAX_FILE_SIZE