🐛 fix(core): reject invalid LSP framing

lsp-server/test/test_core_server.py

@@ -18,6 +18,15 @@ def raw_frame(body: bytes) -> bytes:
     return f"Content-Length: {len(body)}\r\n\r\n".encode("ascii") + body
 
 
+def content_type_frame(message: dict) -> bytes:
+    body = json.dumps(message, separators=(",", ":")).encode("utf-8")
+    header = (
+        f"Content-Length: {len(body)}\r\n"
+        "Content-Type: application/vscode-jsonrpc; charset=utf-8\r\n\r\n"
+    ).encode("ascii")
+    return header + body
+
+
 def read_messages(data: bytes) -> list[dict]:
     messages = []
     offset = 0
@@ -294,6 +303,43 @@ def assert_cancellation_and_failures(server: Path) -> None:
         client.kill()
 
 
+def assert_framing(server: Path) -> None:
+    invalid_payloads = [
+        b"Content-Length: 2junk\r\n\r\n{}",
+        b"Content-Length: 2\r\nContent-Length: 2\r\n\r\n{}",
+        b"Content-Length: 0\r\n\r\n",
+        b"Content-Length: 16777217\r\n\r\n",
+        b"Content-Length: 10\r\n\r\n{}",
+        b"Content-Length: 2\n\n{}",
+        b"X-Length: 2\r\n\r\n{}",
+        b"Content-Length: 2\r\nContent-Type: application/json\r\n\r\n{}",
+    ]
+    for index, payload in enumerate(invalid_payloads):
+        result = run_raw(server, payload)
+        if result.returncode != 1:
+            raise RuntimeError(f"invalid framing case {index} should return code 1")
+        if result.stdout:
+            raise RuntimeError(f"invalid framing case {index} should not process its body")
+
+    valid_payload = b"".join([
+        content_type_frame({
+            "jsonrpc": "2.0",
+            "id": 31,
+            "method": "initialize",
+            "params": {},
+        }),
+        frame({"jsonrpc": "2.0", "id": 32, "method": "shutdown"}),
+        frame({"jsonrpc": "2.0", "method": "exit"}),
+    ])
+    valid = run_raw(server, valid_payload)
+    if valid.returncode != 0:
+        raise RuntimeError("canonical Content-Type should be accepted")
+    if response_by_id(valid.stdout, 31).get("error"):
+        raise RuntimeError("initialize with canonical Content-Type should succeed")
+    if response_by_id(valid.stdout, 32).get("result", "missing") is not None:
+        raise RuntimeError("continuous framing should reach shutdown")
+
+
 def main() -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument("--server", type=Path, required=True)
@@ -302,6 +348,7 @@ def main() -> int:
     assert_lifecycle(args.server)
     assert_json_rpc_errors(args.server)
     assert_cancellation_and_failures(args.server)
+    assert_framing(args.server)
     return 0