4/12/2022 2:07 PM, Mickaël Salaün пишет:
On 23/03/2022 09:41, Konstantin Meskhidze wrote:
3/22/2022 4:24 PM, Mickaël Salaün пишет:
[...]
The remaining question is: should we need to accept 0 as a valid TCP
port? Can it be used? How does the kernel handle it?
I agree that must be a check for port 0 in add_rule_net_service(),
cause unlike most port numbers, port 0 is a reserved port in TCP/IP
networking, meaning that it should not be used in TCP or UDP messages.
Also network traffic sent across the internet to hosts listening on
port 0 might be generated from network attackers or accidentally by
applications programmed incorrectly.
Source: https://www.lifewire.com/port-0-in-tcp-and-udp-818145
OK, so denying this port by default without a way to allow it should not
be an issue. I guess an -EINVAL error would make sense when trying to
allow this port. This should be documented in a comment (with a link to
the RFC/section) and a dedicated test should check that behavior.
What is the behavior of firewalls (e.g. Netfiler) when trying to filter
port 0?
To be honest I don't know. I'm trying to check it.
This doesn't seem to be settle though:
https://www.austingroupbugs.net/view.php?id=1068
Interesting article:
https://z3r0trust.medium.com/socket-programming-the-bizarre-tcp-ip-port-0-saga-fcfbc0e0a276
Thanks. I will check.
.
