The previous validator did a preflight `socket.getaddrinfo` before each
httpx request. Two problems:
* DNS rebinding / TOCTOU: httpx re-resolves at connect time, so a
hostname can answer with a public IP for the validator and a
private IP for the real request. The preflight check did not
constrain the connection.
* Event-loop blocking: `socket.getaddrinfo` is synchronous, and the
media-download callers are async. Slow resolvers stalled
unrelated requests.
Replace it with two layers, both wired automatically onto every httpx
client built by `utils.context`:
1. A request event hook running `validate_url_for_http_request`
(syntactic checks only: scheme, reserved hostnames, literal IPs,
internal TLDs). No DNS, no call-site responsibility.
2. `SSRFProtectedAsyncBackend` / `SSRFProtectedSyncBackend`, custom
httpcore network backends that resolve the hostname inside
`connect_tcp`, reject any address in a forbidden range, then
connect to that *same* validated address. The async variant uses
`loop.getaddrinfo` so it doesn't block the loop. httpcore calls
`start_tls(server_hostname=<URL host>)` after `connect_tcp`, so
TLS SNI and cert verification still use the original hostname
even though the TCP layer connects by IP.
Drop the explicit `validate_url_for_http_request(...)` calls from
`resources_handler.py` — the event hook covers them. Consolidate the
URL validator and its tests under `utils/ssrf.py` /
`tests/utils/test_ssrf.py` so the SSRF surface lives in one module.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This change replaces the `httpx` client with `aiohttp` for the
RetroAchievements API service.
The main reason for this change is that `httpx` has an unavoidable log
line with `INFO` level, which includes the request full URL, containing
the user's API key.
`httpx` has had an
[open discussion](https://github.com/encode/httpx/discussions/2765)
regarding this security issue for almost two years.
The change to `aiohttp` is painless, and would allow us to migrate more
of the codebase to it in the future, to avoid leaking sensitive
information in logs.
