[verified] Handle delivery acknowledgements and read-only recovery

2026-10-13 06:26:49 +00:00
parent 3759fcbde3
commit dbd381a41b
5 changed files with 439 additions and 0 deletions
@@ -0,0 +1,80 @@
+"""Fail-closed decoding for one Gitea API delivery attempt.
+
+Unexpected/malformed acknowledgements can follow a committed mutation: callers
+must not blindly retry. They may perform caller-initiated read-only reconciliation.
+"""
+import json
+import ssl
+from urllib.error import HTTPError, URLError
+
+MAX_RESPONSE_BYTES = 1024 * 1024
+
+
+class DeliveryResponseError(Exception):
+    """Sanitized response failure; message never includes server content."""
+
+
+class InvalidExpectationError(DeliveryResponseError, ValueError):
+    """The caller supplied an invalid endpoint-specific status expectation."""
+
+
+class RejectedResponseError(DeliveryResponseError):
+    """Known auth/redirect or other non-success rejection; do not retry blindly."""
+
+
+class AcknowledgementUncertainError(DeliveryResponseError):
+    """Mutation may have committed; do not retry; reconcile read-only if needed."""
+
+
+def _validate_expected_status(expected_status):
+    if (isinstance(expected_status, bool) or not isinstance(expected_status, int)
+            or expected_status < 200 or expected_status > 299):
+        raise InvalidExpectationError("expected_status must be an explicit success status integer")
+
+
+def _reject_constant(_value):
+    raise ValueError("non-standard JSON constant")
+
+
+def decode_response(status, body, *, expected_status):
+    """Require the exact expected status and a bounded JSON object body."""
+    _validate_expected_status(expected_status)
+    if isinstance(status, bool) or not isinstance(status, int):
+        raise AcknowledgementUncertainError("invalid response status; do not retry; reconcile read-only")
+    if 300 <= status <= 399 or status in (401, 403):
+        raise RejectedResponseError("request rejected or redirected; do not retry blindly")
+    if status != expected_status:
+        raise AcknowledgementUncertainError("unexpected response status; do not retry; reconcile read-only")
+    if not isinstance(body, (bytes, bytearray)) or len(body) > MAX_RESPONSE_BYTES:
+        raise AcknowledgementUncertainError("invalid or oversized response; do not retry; reconcile read-only")
+    try:
+        value = json.loads(bytes(body).decode("utf-8"), parse_constant=_reject_constant)
+    except (UnicodeError, ValueError, RecursionError):
+        raise AcknowledgementUncertainError("invalid JSON response; do not retry; reconcile read-only") from None
+    if not isinstance(value, dict):
+        raise AcknowledgementUncertainError("response JSON must be an object; do not retry; reconcile read-only")
+    return value
+
+
+def deliver_once(send, *, expected_status):
+    """Validate expectation, invoke injected sender exactly once, decode its (status, bytes)."""
+    _validate_expected_status(expected_status)
+    try:
+        result = send()
+    except (RejectedResponseError, ssl.SSLCertVerificationError):
+        raise RejectedResponseError("transport security rejected; do not retry blindly") from None
+    except HTTPError as error:
+        if 300 <= error.code <= 399 or error.code in (401, 403):
+            raise RejectedResponseError("request rejected or redirected; do not retry blindly") from None
+        raise AcknowledgementUncertainError("HTTP acknowledgement uncertain; do not retry; reconcile read-only") from None
+    except URLError as error:
+        if isinstance(error.reason, ssl.SSLCertVerificationError):
+            raise RejectedResponseError("TLS verification rejected; do not retry blindly") from None
+        raise AcknowledgementUncertainError("transport failure; do not retry; reconcile read-only") from None
+    except Exception:
+        raise AcknowledgementUncertainError("transport failure; do not retry; reconcile read-only") from None
+    try:
+        status, body = result
+    except Exception:
+        raise AcknowledgementUncertainError("invalid transport response; do not retry; reconcile read-only") from None
+    return decode_response(status, body, expected_status=expected_status)