netdev - Re: sunrpc port allocation and IANA reserved list

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

Date:	Tue, 10 Nov 2009 15:06:25 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>
CC:	Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: sunrpc port allocation and IANA reserved list

On 11/10/2009 02:26 PM, Trond Myklebust wrote:
> On Tue, 2009-11-10 at 12:37 -0600, Chris Friesen wrote:
>> On 11/10/2009 11:53 AM, Ben Hutchings wrote:
>>> On Tue, 2009-11-10 at 11:43 -0600, Chris Friesen wrote:
>>
>>>> Given that a userspace application can be stopped and restarted at any
>>>> time, and a sunrpc registration can happen at any time, what is the
>>>> expected mechanism to prevent the kernel from allocating a port for use
>>>> by sunrpc that reserved or well-known?
>>>>
>>>> Apparently Redhat and Debian have distro-specific ways of dealing with
>>>> this, but is there a standard solution?  Should there be?
>>>>
>>>> The current setup seems suboptimal.
>>>
>>> I believe both RH and Debian are using the same implementation:
>>> <http://cyberelk.net/tim/software/portreserve/>.
>>
>> That helps with the startup case, but still leaves a possible hole if an
>> app using a fixed port number is restarted at runtime.  During the
>> window where nobody is bound to the port, the kernel could randomly
>> assign it to someone else.
> 
> Just use /proc/sys/sunrpc/{max,min}_resvport interface to restrict the
> range used to a safer one. That's what it is for...

What constitutes a "safer range"?  IANA has ports assigned
intermittently all the way through the default RPC range.  The largest
unassigned range is 922-988 (since 921 is used by lwresd).  If someone
needs more than 66 ports, how are they supposed to handle it?

Chris
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html