On 2 January 2022 03:47:11 GMT, Kirill Nesmeyanov <n...@xakep.ru> wrote:
>
>I just gave an example of what at the moment can cause an exception in any
>application that is based on the PSR. It is enough to send the header "0:
>Farewell to the server". In some cases (for example, as is the case with
>RoadRunner) - this can cause a physical stop and restart of the server.
Any library where a crafted HTTP request can cause a server shutdown has a bug
which needs addressing right now - possibly more than one, actually, as it
implies error handling is leaking across request boundaries. A change to the
language applied in the next major version would fix this some time around
2025, once people start adopting it. A workaround in the library itself can be
applied within weeks.
I already gave a simple solution that such libraries can apply right now, with
very little chance of negative impact: sanitise headers more aggressively than
the HTTP standard requires, as Apache httpd does, in this case discarding any
header containing only digits. This is likely to be about three lines of code
inside a loop preprocessing raw headers:
if ( ctype_digit($rawHeaderName) ) {
trigger_error("Numeric HTTP header '$rawHeaderName' has been discarded.",
E_USER_WARNING);
continue;
}
If I was the maintainer of such a library, I might consider even stricter
validation, considering what seems like an accidentally broad definition in the
HTTP spec, and the possibility of an application receiving even more exotic
characters if processing raw TCP traffic.
The idea of an array_keys variant or option that forces everything back to
string seems like it might be useful (and easy to polyfill for old versions).
Changing such a fundamental language behaviour in the hope that it will fix
more code than it breaks is just not worth it.
Regards,
--
Rowan Tommins
[IMSoP]
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