netdev - Re: [RFC PATCH v4 03/15] landlock: landlock_find/insert

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Date:   Tue, 26 Apr 2022 12:15:36 +0300
From:   Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        <willemdebruijn.kernel@...il.com>
CC:     <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
        <netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
        <artem.kuzin@...wei.com>, <anton.sirazetdinov@...wei.com>
Subject: Re: [RFC PATCH v4 03/15] landlock: landlock_find/insert_rule
 refactoring (TCP port 0)



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.
> 
> .