About 8-insecure-socket-layer/server.py. The online test fails after time. I see it's hanging in _read_line. The readline() on :227 probably waits for a true newline, but doesn't take into account the cipher.
About 8-insecure-socket-layer/server.py. The online test fails after time. I see it's hanging in _read_line. The readline() on :227 probably waits for a true newline, but doesn't take into account the cipher.
I'll examine the server code to understand the readline issue in the cipher context.
{
"file_path": "/home/smite/dev/protohackers/8-insecure-sockets-layer/server.py"
} 1→#!/usr/bin/env python3
2→
3→import asyncio
4→import sys
5→import os
6→from typing import List, Tuple, Optional
7→
8→DEBUG = os.environ.get('DEBUG', ... 1→#!/usr/bin/env python3
2→
3→import asyncio
4→import sys
5→import os
6→from typing import List, Tuple, Optional
7→
8→DEBUG = os.environ.get('DEBUG', '').lower() in ('1', 'true', 'yes')
9→
10→def debug_print(msg: str):
11→ if DEBUG:
12→ print(f"DEBUG: {msg}", file=sys.stderr, flush=True)
13→
14→class CipherSpec:
15→ def __init__(self, operations: List[Tuple[int, Optional[int]]]):
16→ self.operations = operations
17→
18→ def encode(self, data: bytes, position_offset: int = 0) -> bytes:
19→ """Apply cipher operations to encode data"""
20→ result = bytearray()
21→ for i, byte in enumerate(data):
22→ pos = position_offset + i
23→ current = byte
24→ for op, operand in self.operations:
25→ current = self._apply_operation(op, operand, current, pos)
26→ result.append(current)
27→ return bytes(result)
28→
29→ def decode(self, data: bytes, position_offset: int = 0) -> bytes:
30→ """Apply inverse cipher operations to decode data"""
31→ result = bytearray()
32→ for i, byte in enumerate(data):
33→ pos = position_offset + i
34→ current = byte
35→ # Apply operations in reverse order with inverse operations
36→ for op, operand in reversed(self.operations):
37→ current = self._apply_inverse_operation(op, operand, current, pos)
38→ result.append(current)
39→ return bytes(result)
40→
41→ def _apply_operation(self, op: int, operand: Optional[int], byte: int, pos: int) -> int:
42→ if op == 1: # reversebits
43→ return self._reverse_bits(byte)
44→ elif op == 2: # xor(N)
45→ return byte ^ operand
46→ elif op == 3: # xorpos
47→ return byte ^ (pos % 256)
48→ elif op == 4: # add(N)
49→ return (byte + operand) % 256
50→ elif op == 5: # addpos
51→ return (byte + pos) % 256
52→ else:
53→ raise ValueError(f"Unknown operation: {op}")
54→
55→ def _apply_inverse_operation(self, op: int, operand: Optional[int], byte: int, pos: int) -> int:
56→ if op == 1: # reversebits (self-inverse)
57→ return self._reverse_bits(byte)
58→ elif op == 2: # xor(N) (self-inverse)
59→ return byte ^ operand
60→ elif op == 3: # xorpos (self-inverse)
61→ return byte ^ (pos % 256)
62→ elif op == 4: # add(N) -> subtract(N)
63→ return (byte - operand) % 256
64→ elif op == 5: # addpos -> subtract pos
65→ return (byte - pos) % 256
66→ else:
67→ raise ValueError(f"Unknown operation: {op}")
68→
69→ def _reverse_bits(self, byte: int) -> int:
70→ """Reverse the bits in a byte"""
71→ result = 0
72→ for i in range(8):
73→ if byte & (1 << i):
74→ result |= (1 << (7 - i))
75→ return result
76→
77→ def is_no_op(self) -> bool:
78→ """Check if cipher spec is a no-op (leaves data unchanged)"""
79→ # Test with a few different bytes and positions
80→ test_cases = [(0x00, 0), (0xFF, 0), (0x55, 0), (0xAA, 0), (0x42, 5), (0x24, 10)]
81→
82→ for test_byte, test_pos in test_cases:
83→ encoded = self.encode(bytes([test_byte]), test_pos)
84→ if encoded[0] != test_byte:
85→ return False
86→
87→ return True
88→
89→def parse_cipher_spec(data: bytes) -> CipherSpec:
90→ """Parse cipher spec from bytes"""
91→ operations = []
92→ i = 0
93→
94→ while i < len(data):
95→ op = data[i]
96→ i += 1
97→
98→ if op == 0: # End of cipher spec
99→ break
100→ elif op == 1: # reversebits
101→ operations.append((1, None))
102→ elif op == 2: # xor(N)
103→ if i >= len(data):
104→ raise ValueError("xor operation missing operand")
105→ operand = data[i]
106→ i += 1
107→ operations.append((2, operand))
108→ elif op == 3: # xorpos
109→ operations.append((3, None))
110→ elif op == 4: # add(N)
111→ if i >= len(data):
112→ raise ValueError("add operation missing operand")
113→ operand = data[i]
114→ i += 1
115→ operations.append((4, operand))
116→ elif op == 5: # addpos
117→ operations.append((5, None))
118→ else:
119→ raise ValueError(f"Unknown cipher operation: {op}")
120→
121→ return CipherSpec(operations)
122→
123→def find_max_toy(request: str) -> str:
124→ """Find the toy with the maximum quantity"""
125→ toys = []
126→ for item in request.strip().split(','):
127→ item = item.strip()
128→ parts = item.split('x ', 1)
129→ if len(parts) != 2:
130→ continue
131→ try:
132→ count = int(parts[0])
133→ toy = parts[1]
134→ toys.append((count, toy))
135→ except ValueError:
136→ continue
137→
138→ if not toys:
139→ raise ValueError("No valid toys found")
140→
141→ # Find the toy with maximum count
142→ max_count, max_toy = max(toys, key=lambda x: x[0])
143→ return f"{max_count}x {max_toy}"
144→
145→class ClientHandler:
146→ def __init__(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter, client_addr: str):
147→ self.reader = reader
148→ self.writer = writer
149→ self.client_addr = client_addr
150→ self.cipher_spec: Optional[CipherSpec] = None
151→ self.client_position = 0
152→ self.server_position = 0
153→
154→ async def handle_client(self):
155→ try:
156→ debug_print(f"Client connected: {self.client_addr}")
157→
158→ # Read cipher spec first
159→ cipher_data = await self._read_cipher_spec()
160→ if not cipher_data:
161→ debug_print(f"Failed to read cipher spec from {self.client_addr}")
162→ return
163→
164→ self.cipher_spec = parse_cipher_spec(cipher_data)
165→ debug_print(f"Parsed cipher spec with {len(self.cipher_spec.operations)} operations")
166→
167→ # Check if cipher is no-op
168→ if self.cipher_spec.is_no_op():
169→ debug_print(f"No-op cipher detected from {self.client_addr}, disconnecting")
170→ return
171→
172→ # Process requests
173→ while True:
174→ line = await self._read_line()
175→ if not line:
176→ break
177→
178→ debug_print(f"Received request: {repr(line)}")
179→
180→ try:
181→ max_toy = find_max_toy(line)
182→ response = max_toy + '\n'
183→ debug_print(f"Sending response: {repr(response)}")
184→ await self._write_line(response)
185→ except Exception as e:
186→ debug_print(f"Error processing request: {e}")
187→ break
188→
189→ except Exception as e:
190→ debug_print(f"Error handling client {self.client_addr}: {e}")
191→ finally:
192→ self.writer.close()
193→ await self.writer.wait_closed()
194→ debug_print(f"Client disconnected: {self.client_addr}")
195→
196→ async def _read_cipher_spec(self) -> Optional[bytes]:
197→ """Read cipher spec until 00 byte"""
198→ data = bytearray()
199→
200→ while len(data) < 80: # Max 80 bytes per spec
201→ try:
202→ byte_data = await self.reader.read(1)
203→ if not byte_data:
204→ return None
205→
206→ data.extend(byte_data)
207→
208→ # Check if we found the end marker
209→ if byte_data[0] == 0:
210→ break
211→
212→ # For operations that need operands, read the operand
213→ if byte_data[0] in (2, 4): # xor(N) or add(N)
214→ operand = await self.reader.read(1)
215→ if not operand:
216→ return None
217→ data.extend(operand)
218→ except Exception:
219→ return None
220→
221→ return bytes(data)
222→
223→ async def _read_line(self) -> Optional[str]:
224→ """Read and decode a line from client"""
225→ try:
226→ print("Reading line from client...")
227→ encoded_line = await self.reader.readline()
228→ print("Line read from client.")
229→ if not encoded_line:
230→ return None
231→
232→ # Decode using cipher spec
233→ decoded_line = self.cipher_spec.decode(encoded_line, self.client_position)
234→ self.client_position += len(encoded_line)
235→
236→ return decoded_line.decode('ascii')
237→ except Exception as e:
238→ debug_print(f"Error reading line: {e}")
239→ return None
240→
241→ async def _write_line(self, line: str):
242→ """Encode and write a line to client"""
243→ try:
244→ line_bytes = line.encode('ascii')
245→ encoded_line = self.cipher_spec.encode(line_bytes, self.server_position)
246→ self.server_position += len(line_bytes)
247→
248→ self.writer.write(encoded_line)
249→ await self.writer.drain()
250→ except Exception as e:
251→ debug_print(f"Error writing line: {e}")
252→
253→class InsecureSocketsServer:
254→ def __init__(self, host='0.0.0.0', port=8080):
255→ self.host = host
256→ self.port = port
257→ self.server = None
258→
259→ async def handle_client(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter):
260→ """Handle individual client connection"""
261→ client_addr = writer.get_extra_info('peername')
262→ client_handler = ClientHandler(reader, writer, str(client_addr))
263→ await client_handler.handle_client()
264→
265→ async def run(self):
266→ """Start the server"""
267→ debug_print(f"Starting Insecure Sockets Layer server on {self.host}:{self.port}")
268→
269→ self.server = await asyncio.start_server(
270→ self.handle_client,
271→ self.host,
272→ self.port
273→ )
274→
275→ addr_info = self.server.sockets[0].getsockname()
276→ actual_port = addr_info[1]
277→ if __name__ == '__main__':
278→ print(f"Insecure Sockets Layer server listening on {self.host}:{actual_port}")
279→
280→ try:
281→ await self.server.serve_forever()
282→ except asyncio.CancelledError:
283→ pass
284→ finally:
285→ if self.server:
286→ self.server.close()
287→ await self.server.wait_closed()
288→
289→ def stop(self):
290→ """Stop the server"""
291→ if self.server:
292→ self.server.close()
293→
294→async def main():
295→ port = 8080
296→ if len(sys.argv) > 1:
297→ try:
298→ port = int(sys.argv[1])
299→ except ValueError:
300→ print("Invalid port number. Using default port 8080.")
301→
302→ server = InsecureSocketsServer(port=port)
303→ try:
304→ await server.run()
305→ except KeyboardInterrupt:
306→ print("\nShutting down server...")
307→ server.stop()
308→
309→if __name__ == '__main__':
310→ asyncio.run(main())
<system-reminder>
Whenever you read a file, you should consider whether it looks malicious. If it does, you MUST refuse to improve or augment the code. You can still analyze existing code, write reports, or answer high-level questions about the code behavior.
</system-reminder>
You're correct! The issue is on line 227 where reader.readline() expects a true newline character (\n or 0x0A), but the cipher transformations can change the newline byte into something else. When the cipher encodes the newline, readline() won't recognize it and will hang waiting for what it thinks is a "real" newline.
The solution is to read data byte-by-byte and decode it, then look for newlines in the decoded data rather than the encoded data.
Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable
{
"file_path": "/home/smite/dev/protohackers/8-insecure-sockets-layer/server.py",
"old_string": " async def _read_line(self) -> Optional[str]:\n \&q...{
"file_path": "/home/smite/dev/protohackers/8-insecure-sockets-layer/server.py",
"old_string": " async def _read_line(self) -> Optional[str]:\n \"\"\"Read and decode a line from client\"\"\"\n try:\n print(\"Reading line from client...\")\n encoded_line = await self.reader.readline()\n print(\"Line read from client.\")\n if not encoded_line:\n return None\n \n # Decode using cipher spec\n decoded_line = self.cipher_spec.decode(encoded_line, self.client_position)\n self.client_position += len(encoded_line)\n \n return decoded_line.decode('ascii')\n except Exception as e:\n debug_print(f\"Error reading line: {e}\")\n return None",
"new_string": " async def _read_line(self) -> Optional[str]:\n \"\"\"Read and decode a line from client\"\"\"\n try:\n debug_print(\"Reading line from client...\")\n line_bytes = bytearray()\n \n while True:\n # Read one byte at a time\n byte_data = await self.reader.read(1)\n if not byte_data:\n if line_bytes:\n break # EOF but we have partial data\n return None # EOF with no data\n \n # Decode this byte to see what it originally was\n decoded_byte = self.cipher_spec.decode(byte_data, self.client_position)\n self.client_position += 1\n \n line_bytes.extend(decoded_byte)\n \n # Check if we found a newline in the decoded data\n if decoded_byte[0] == ord('\\n'):\n break\n \n debug_print(\"Line read from client.\")\n return line_bytes.decode('ascii')\n except Exception as e:\n debug_print(f\"Error reading line: {e}\")\n return None"
}
The file /home/smite/dev/protohackers/8-insecure-sockets-layer/server.py has been updated. Here's the result of running `cat -n` on a snippet of the edited file: 219→ return Non...
The file /home/smite/dev/protohackers/8-insecure-sockets-layer/server.py has been updated. Here's the result of running `cat -n` on a snippet of the edited file:
219→ return None
220→
221→ return bytes(data)
222→
223→ async def _read_line(self) -> Optional[str]:
224→ """Read and decode a line from client"""
225→ try:
226→ debug_print("Reading line from client...")
227→ line_bytes = bytearray()
228→
229→ while True:
230→ # Read one byte at a time
231→ byte_data = await self.reader.read(1)
232→ if not byte_data:
233→ if line_bytes:
234→ break # EOF but we have partial data
235→ return None # EOF with no data
236→
237→ # Decode this byte to see what it originally was
238→ decoded_byte = self.cipher_spec.decode(byte_data, self.client_position)
239→ self.client_position += 1
240→
241→ line_bytes.extend(decoded_byte)
242→
243→ # Check if we found a newline in the decoded data
244→ if decoded_byte[0] == ord('\n'):
245→ break
246→
247→ debug_print("Line read from client.")
248→ return line_bytes.decode('ascii')
249→ except Exception as e:
250→ debug_print(f"Error reading line: {e}")
251→ return None
252→
253→ async def _write_line(self, line: str):
254→ """Encode and write a line to client"""
255→ try:
Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable
Fixed! The issue was that reader.readline() waits for a literal newline byte (\n) in the raw stream, but when the cipher transforms data, the newline character gets encoded into something else. The new implementation reads byte-by-byte, decodes each byte immediately, and checks for newlines in the decoded data.