Re: [PATCH] rpc.statd: Bind downcall socket to loopback address

[Steve Dickson <SteveD@redhat.com>]

On 08/03/2011 05:18 PM, Chuck Lever wrote:
> 
> On Aug 3, 2011, at 1:44 PM, Steve Dickson wrote:
> 
>>
>>
>> On 08/01/2011 04:13 PM, Chuck Lever wrote:
>>> In the past, rpc.statd posted SM_NOTIFY requests using the same socket
>>> it used for sending downcalls to the kernel.  To receive replies from
>>> remote hosts, the socket was bound to INADDR_ANY.
>>>
>>> With commit f113db52 "Remove notify functionality from statd in
>>> favour of sm-notify" (Mar 20, 2007), the downcall socket is no longer
>>> used for sending requests to remote hosts.  However, the downcall
>>> socket is still bound to INADDR_ANY.
>>>
>>> Thus a remote host can inject data on this socket since it is an
>>> unconnected UDP socket listening for RPC replies.  Thanks to f113db52,
>>> the port number of this socket is no longer controlled by a command
>>> line option, making it difficult to firewall.
>>>
>>> We have demonstrated that data injection on this socket can result in
>>> a DoS by causing rpc.statd to consume CPU and log bandwidth, but so
>>> far we have not found a breach.
>>>
>>> To prevent unwanted data injection, bind this socket to the loopback
>>> address.
>>>
>>> BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=177
>>>
>>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> Committed..
> 
> Do you want to close out bz 177, or shall I? 
> Or we can wait for the next nfs-utils release (1.2.5?) to mark it FIXED.
Go ahead and close it out... It was all your hard work that got it 
done! You might as well have the pleasure of closing it... ;-) 

steved.

> 
>> steved.
>>
>>> ---
>>>
>>> Confirmed that reboot recovery still works, and that data injection
>>> is no longer possible.  This is an updated and final version of this
>>> patch.
>>>
>>> utils/statd/rmtcall.c |    2 +-
>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/utils/statd/rmtcall.c b/utils/statd/rmtcall.c
>>> index 0e52fe2..4ecb03c 100644
>>> --- a/utils/statd/rmtcall.c
>>> +++ b/utils/statd/rmtcall.c
>>> @@ -85,7 +85,7 @@ statd_get_socket(void)
>>>
>>> 		memset(&sin, 0, sizeof(sin));
>>> 		sin.sin_family = AF_INET;
>>> -		sin.sin_addr.s_addr = INADDR_ANY;
>>> +		sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
>>>
>>> 		if (bindresvport(sockfd, &sin) < 0) {
>>> 			xlog(D_GENERAL, "%s: can't bind to reserved port",
>>>
>>> --
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> 
> --
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
> 
> 
>