netdev - Re: [PATCH net-next v2] net: Fail explicit bind to local reserved ports

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20191107.151225.1298112792540927971.davem@davemloft.net>
Date:   Thu, 07 Nov 2019 15:12:25 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     stranche@...eaurora.org
Cc:     netdev@...r.kernel.org, subashab@...eaurora.org
Subject: Re: [PATCH net-next v2] net: Fail explicit bind to local reserved
 ports

From: Sean Tranchetti <stranche@...eaurora.org>
Date: Mon,  4 Nov 2019 17:25:41 -0700

> Reserved ports may have some special use cases which are not suitable for
> use by general userspace applications. Currently, ports specified in
> ip_local_reserved_ports will not be returned only in case of automatic port
> assignment.
> 
> In some cases, it maybe required to prevent the host from assigning the
> ports even in case of explicit binds. Consider the case of a transparent
> proxy where packets are being redirected. In case a socket matches this
> connection, packets from this application would be incorrectly sent to one
> of the endpoints.
> 
> Add a boolean sysctl flag 'reserved_port_bind'. Default value is 1 which
> preserves the existing behavior. Setting the value to 0 will prevent
> userspace applications from binding to these ports even when they are
> explicitly requested.
> 
> Signed-off-by: Sean Tranchetti <stranche@...eaurora.org>
> Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>

I think that someone with CAP_NET_BIND_SERVICE should be able to
override this.

Really, this is just extending the usual 0-->PROT_SOCK restriction.

This whole area is a mess of knobs and conditions, so I'd rather see
this implemented with some consolidation rather than layering yet
another thing on top of what we already have.

Thanks.