decomposer: generate deliverable files for Define the service contract and project architecture for the FastAPI endpoint monitoring service.; Implement the typed monitor CRUD API and concurrency-safe in-memory state according to the service design.; Implement secure on-demand endpoint checks with status updates, latency measurement, robust error handling, and redacted structured logs.; Add operational API endpoints and environment-driven runtime configuration to the monitoring service.; Create automated tests for the monitoring service.; Package the service with Docker and developer documentation.; Validate the complete project.

app/security.py

@@ -2,53 +2,48 @@ import asyncio
 import ipaddress
 import socket
 from collections.abc import Awaitable, Callable
-from urllib.parse import SplitResult, urlsplit, urlunsplit
+from urllib.parse import urlsplit, urlunsplit
 
 Resolver = Callable[[str, int], Awaitable[list[str]]]
 
 
-class UnsafeTargetError(ValueError):
+class DestinationRejected(ValueError):
     pass
 
 
-async def resolve_addresses(host: str, port: int) -> list[str]:
+async def system_resolver(host: str, port: int) -> list[str]:
-    def lookup() -> list[str]:
+    loop = asyncio.get_running_loop()
-        records = socket.getaddrinfo(host, port, type=socket.SOCK_STREAM)
+    records = await loop.getaddrinfo(host, port, type=socket.SOCK_STREAM)
-        return list({record[4][0] for record in records})
+    return sorted({record[4][0] for record in records})
-
-    return await asyncio.to_thread(lookup)
 
 
 def redacted_url(url: str) -> str:
-    parsed = urlsplit(url)
+    parts = urlsplit(url)
-    host = parsed.hostname or "invalid-host"
+    host = parts.hostname or ""
-    if ":" in host:
+    authority = f"{host}:{parts.port}" if parts.port else host
-        host = f"[{host}]"
+    query = "<redacted>" if parts.query else ""
-    port = f":{parsed.port}" if parsed.port else ""
+    return urlunsplit((parts.scheme, authority, parts.path or "/", query, ""))
-    return urlunsplit((parsed.scheme, f"{host}{port}", parsed.path or "/", "", ""))
 
 
-async def validate_target(url: str, resolver: Resolver) -> SplitResult:
+async def require_public_destination(url: str, resolver: Resolver = system_resolver) -> None:
-    parsed = urlsplit(url)
+    parts = urlsplit(url)
-    if parsed.scheme not in {"http", "https"} or not parsed.hostname:
+    if parts.scheme not in {"http", "https"} or not parts.hostname:
-        raise UnsafeTargetError("only absolute HTTP(S) URLs are allowed")
+        raise DestinationRejected("only HTTP(S) destinations are allowed")
-    if parsed.username is not None or parsed.password is not None:
+    if parts.username is not None or parts.password is not None:
-        raise UnsafeTargetError("URL credentials are not allowed")
+        raise DestinationRejected("URL user information is not allowed")
     try:
-        port = parsed.port or (443 if parsed.scheme == "https" else 80)
+        port = parts.port or (443 if parts.scheme == "https" else 80)
     except ValueError as exc:
-        raise UnsafeTargetError("invalid port") from exc
+        raise DestinationRejected("invalid destination port") from exc
     try:
-        addresses = await resolver(parsed.hostname, port)
+        addresses = await resolver(parts.hostname, port)
-    except (OSError, socket.gaierror) as exc:
+    except (OSError, UnicodeError) as exc:
-        raise UnsafeTargetError("DNS resolution failed") from exc
+        raise DestinationRejected("destination DNS resolution failed") from exc
     if not addresses:
-        raise UnsafeTargetError("DNS resolution returned no addresses")
+        raise DestinationRejected("destination DNS resolution returned no addresses")
-    for address in addresses:
+    try:
-        try:
+        parsed = [ipaddress.ip_address(address) for address in addresses]
-            ip = ipaddress.ip_address(address)
+    except ValueError as exc:
-        except ValueError as exc:
+        raise DestinationRejected("destination DNS returned an invalid address") from exc
-            raise UnsafeTargetError("DNS returned an invalid address") from exc
+    if any(not address.is_global for address in parsed):
-        if not ip.is_global:
+        raise DestinationRejected("destination resolves to a non-public address")
-            raise UnsafeTargetError("target resolves to a non-public address")
-    return parsed