578239a496
Run every Gitea API and broker control exchange inside a killable helper process whose connect, send, and read share one absolute wall-clock deadline, and add a watchdog that force-closes streaming connections at expiry. Redirects are rejected before authentication headers can move. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
303 lines
10 KiB
Python
303 lines
10 KiB
Python
#!/usr/bin/env python3
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"""Absolute wall-clock deadlines for every outbound Hermes HTTP exchange.
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Small control exchanges run inside a killable helper process, so connect,
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send, read, and DNS all share one hard bound that no blocking socket state
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can outlive. Large streaming Git exchanges cannot cross a process boundary;
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they instead register their connection with a watchdog that force-closes the
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socket when the same kind of absolute deadline expires.
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"""
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from __future__ import annotations
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import base64
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import contextlib
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import email.message
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import http.client
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import io
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import json
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import os
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import signal
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import socket
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import subprocess
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import sys
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import threading
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import time
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import urllib.error
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import urllib.request
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from dataclasses import dataclass
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from gitea_api_policy import PolicyError
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MAX_CONTROL_BYTES = 128 * 1024
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MAX_PROTOCOL_BYTES = 4 * 1024 * 1024
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MAX_STREAM_SECONDS = 900.0
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READ_CHUNK = 64 * 1024
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class _RejectRedirect(urllib.request.HTTPRedirectHandler):
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def redirect_request(self, req, fp, code, msg, headers, newurl):
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raise urllib.error.URLError("redirect rejected")
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@dataclass(frozen=True)
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class Result:
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"""Minimal HTTP evidence returned across the process boundary."""
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status: int
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content_type: str
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body: bytes
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def _read_response(response, maximum: int, deadline: float) -> bytes:
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chunks: list[bytes] = []
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total = 0
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while True:
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remaining = deadline - time.monotonic()
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if remaining <= 0:
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raise TimeoutError
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raw = getattr(getattr(response, "fp", None), "raw", None)
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sock = getattr(raw, "_sock", raw)
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if hasattr(sock, "settimeout"):
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sock.settimeout(remaining)
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chunk = response.read(min(READ_CHUNK, maximum + 1 - total))
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if not chunk:
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break
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chunks.append(chunk)
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total += len(chunk)
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if total > maximum:
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raise ValueError("response too large")
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return b"".join(chunks)
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def _child_exchange(control: dict[str, object]) -> Result:
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url = control.get("url")
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method = control.get("method")
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headers = control.get("headers")
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encoded = control.get("body")
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maximum = control.get("maximum")
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timeout = control.get("timeout")
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if (
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not isinstance(url, str)
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or not isinstance(method, str)
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or not isinstance(headers, dict)
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or not all(isinstance(key, str) and isinstance(value, str) for key, value in headers.items())
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or not isinstance(encoded, str)
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or not isinstance(maximum, int)
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or not 0 <= maximum <= 2 * 1024 * 1024
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or not isinstance(timeout, (int, float))
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or not 0 < timeout <= 120
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):
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raise ValueError("invalid control")
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body = base64.b64decode(encoded, validate=True) if encoded else None
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if body is not None and len(body) > MAX_CONTROL_BYTES:
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raise ValueError("request too large")
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deadline = time.monotonic() + float(timeout)
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request = urllib.request.Request(
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url, data=body, method=method, headers=headers # type: ignore[arg-type]
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)
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opener = urllib.request.build_opener(_RejectRedirect())
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try:
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response = opener.open(request, timeout=max(deadline - time.monotonic(), 0.001))
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except urllib.error.HTTPError as error:
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response = error
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with response:
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status = getattr(response, "status", response.getcode())
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content_type = response.headers.get_content_type()
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value = _read_response(response, maximum, deadline)
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return Result(int(status), str(content_type), value)
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def _child_main() -> int:
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try:
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raw = sys.stdin.buffer.read(MAX_CONTROL_BYTES + 1)
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if len(raw) > MAX_CONTROL_BYTES:
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raise ValueError("control too large")
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control = json.loads(raw)
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if not isinstance(control, dict):
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raise ValueError("invalid control")
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result = _child_exchange(control)
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output = {
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"ok": True,
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"status": result.status,
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"content_type": result.content_type,
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"body": base64.b64encode(result.body).decode("ascii"),
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}
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except Exception:
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output = {"ok": False}
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sys.stdout.write(json.dumps(output, separators=(",", ":")))
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return 0 if output["ok"] else 1
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def _terminate(process: subprocess.Popen[bytes]) -> None:
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with contextlib.suppress(ProcessLookupError):
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os.killpg(process.pid, signal.SIGKILL)
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process.communicate()
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def exchange(
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request: urllib.request.Request,
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*,
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maximum: int,
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timeout: float,
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popen=subprocess.Popen,
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) -> Result:
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"""Execute a whole request under one monotonic deadline and size limit."""
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if not 0 < timeout <= 120 or not 0 <= maximum <= 2 * 1024 * 1024:
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raise PolicyError("HTTP control request bounds are invalid")
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body = request.data or b""
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if not isinstance(body, bytes) or len(body) > MAX_CONTROL_BYTES:
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raise PolicyError("HTTP control request exceeds the safe size limit")
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control = json.dumps(
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{
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"url": request.full_url,
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"method": request.get_method(),
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"headers": dict(request.header_items()),
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"body": base64.b64encode(body).decode("ascii"),
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"maximum": maximum,
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"timeout": timeout,
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},
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separators=(",", ":"),
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).encode()
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deadline = time.monotonic() + timeout
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process = popen(
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[sys.executable, os.path.realpath(__file__), "--child"],
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.DEVNULL,
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start_new_session=True,
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env={"LANG": "C.UTF-8", "PATH": "/usr/bin:/bin"},
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)
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try:
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remaining = deadline - time.monotonic()
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if remaining <= 0:
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raise subprocess.TimeoutExpired(process.args, timeout)
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output, _error = process.communicate(control, timeout=remaining)
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except subprocess.TimeoutExpired as exc:
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_terminate(process)
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raise PolicyError("HTTP control request deadline exceeded") from exc
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if process.returncode != 0 or len(output) > MAX_PROTOCOL_BYTES:
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raise PolicyError("HTTP control request failed")
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try:
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result = json.loads(output)
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if not isinstance(result, dict) or result.get("ok") is not True:
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raise ValueError
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status = result["status"]
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content_type = result["content_type"]
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encoded = result["body"]
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if not isinstance(status, int) or not isinstance(content_type, str) or not isinstance(encoded, str):
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raise ValueError
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value = base64.b64decode(encoded, validate=True)
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except (KeyError, ValueError, TypeError, json.JSONDecodeError) as exc:
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raise PolicyError("HTTP control helper returned invalid evidence") from exc
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if len(value) > maximum:
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raise PolicyError("HTTP control response exceeds the safe size limit")
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return Result(status, content_type, value)
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class _AdaptedResponse:
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"""Present one finished exchange through the urlopen reader interface."""
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def __init__(self, result: Result):
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self.status = result.status
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self.headers = email.message.Message()
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self.headers["Content-Type"] = result.content_type
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self._stream = io.BytesIO(result.body)
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def read(self, limit: int = -1) -> bytes:
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return self._stream.read(limit)
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def __enter__(self):
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return self
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def __exit__(self, *_excinfo: object) -> bool:
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return False
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def open_bounded(
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request: urllib.request.Request,
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*,
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maximum: int,
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timeout: float,
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popen=subprocess.Popen,
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) -> _AdaptedResponse:
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"""Open one control exchange whose whole lifetime shares one deadline."""
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return _AdaptedResponse(
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exchange(request, maximum=maximum, timeout=timeout, popen=popen)
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)
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class StreamDeadline:
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"""Force-close tracked connections once an absolute deadline passes."""
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def __init__(self, timeout: float, *, timer=threading.Timer):
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if not 0 < timeout <= MAX_STREAM_SECONDS:
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raise PolicyError("HTTP stream deadline bounds are invalid")
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self._deadline = time.monotonic() + timeout
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self._lock = threading.Lock()
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self._connections: list[http.client.HTTPConnection] = []
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self.expired = False
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self._timer = timer(timeout, self._expire)
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self._timer.daemon = True
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self._timer.start()
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def remaining(self) -> float:
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value = self._deadline - time.monotonic()
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if value <= 0 or self.expired:
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raise PolicyError("HTTP stream deadline exceeded")
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return value
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def _expire(self) -> None:
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with self._lock:
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self.expired = True
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connections = list(self._connections)
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for connection in connections:
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# Shut the raw socket down first so a blocked send or recv wakes
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# immediately; close alone leaves peers waiting on the old fd.
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sock = getattr(connection, "sock", None)
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if sock is not None:
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with contextlib.suppress(OSError):
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sock.shutdown(socket.SHUT_RDWR)
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connection.close()
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def _track(self, connection: http.client.HTTPConnection):
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with self._lock:
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expired = self.expired
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if not expired:
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self._connections.append(connection)
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if expired:
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connection.close()
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raise PolicyError("HTTP stream deadline exceeded")
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return connection
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def cancel(self) -> None:
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self._timer.cancel()
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def handlers(self) -> tuple[urllib.request.BaseHandler, ...]:
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"""Build urllib handlers whose connections obey this deadline."""
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deadline = self
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class GuardedHTTPHandler(urllib.request.HTTPHandler):
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def http_open(self, req):
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return self.do_open(
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lambda host, **kwargs: deadline._track(
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http.client.HTTPConnection(host, **kwargs)
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),
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req,
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)
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class GuardedHTTPSHandler(urllib.request.HTTPSHandler):
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def https_open(self, req):
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return self.do_open(
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lambda host, **kwargs: deadline._track(
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http.client.HTTPSConnection(host, **kwargs)
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),
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req,
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)
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return (GuardedHTTPHandler(), GuardedHTTPSHandler())
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if __name__ == "__main__":
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raise SystemExit(_child_main() if sys.argv[1:] == ["--child"] else 2)
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