linux-kernel - Re: [PATCH 4.13 28/43] SMB3: Validate negotiate request must always be signed

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Message-ID: <b20cbd94-ce9b-cb2c-dc95-a6821376823f@csail.mit.edu>
Date:   Tue, 27 Feb 2018 01:22:31 -0800
From:   "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Thomas Backlund <tmb@...eia.org>,
        Steve French <smfrench@...il.com>,
        Aurélien Aptel <aaptel@...e.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        lsahlber@...hat.com, pshilov@...rosoft.com,
        linux-cifs@...r.kernel.org
Subject: Re: [PATCH 4.13 28/43] SMB3: Validate negotiate request must always
 be signed

On 2/27/18 12:54 AM, Greg Kroah-Hartman wrote:
> On Mon, Feb 26, 2018 at 07:44:28PM -0800, Srivatsa S. Bhat wrote:
>> On 1/3/18 6:15 PM, Srivatsa S. Bhat wrote:
>>> On 11/1/17 8:18 AM, Greg Kroah-Hartman wrote:
>>>> On Tue, Oct 31, 2017 at 03:02:11PM +0200, Thomas Backlund wrote:
>>>>> Den 31.10.2017 kl. 11:55, skrev Greg Kroah-Hartman:
>>>>>> 4.13-stable review patch.  If anyone has any objections, please let me know.
>>>>>>
>>>>>> ------------------
>>>>>>
>>>>>> From: Steve French <smfrench@...il.com>
>>>>>>
>>>>>> commit 4587eee04e2ac7ac3ac9fa2bc164fb6e548f99cd upstream.
>>>>>>
>>>>>> According to MS-SMB2 3.2.55 validate_negotiate request must
>>>>>> always be signed. Some Windows can fail the request if you send it unsigned
>>>>>>
>>>>>> See kernel bugzilla bug 197311
>>>>>>
>>>>>> Acked-by: Ronnie Sahlberg <lsahlber.redhat.com>
>>>>>> Signed-off-by: Steve French <smfrench@...il.com>
>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>>>>>
>>>>>> ---
>>>>>>   fs/cifs/smb2pdu.c |    3 +++
>>>>>>   1 file changed, 3 insertions(+)
>>>>>>
>>>>>> --- a/fs/cifs/smb2pdu.c
>>>>>> +++ b/fs/cifs/smb2pdu.c
>>>>>> @@ -1963,6 +1963,9 @@ SMB2_ioctl(const unsigned int xid, struc
>>>>>>   	} else
>>>>>>   		iov[0].iov_len = get_rfc1002_length(req) + 4;
>>>>>> +	/* validate negotiate request must be signed - see MS-SMB2 3.2.5.5 */
>>>>>> +	if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO)
>>>>>> +		req->hdr.sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
>>>>>>   	rc = SendReceive2(xid, ses, iov, n_iov, &resp_buftype, flags, &rsp_iov);
>>>>>>   	cifs_small_buf_release(req);
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> This one needs to be backported to all stable kernels as the commit that
>>>>> introduced the regression:
>>>>> '
>>>>> 0603c96f3af50e2f9299fa410c224ab1d465e0f9
>>>>> SMB: Validate negotiate (to protect against downgrade) even if signing off
>>>>>
>>>>> is backported in stable trees as of: 4.9.53, 4.4.90, 3.18.73
>>>>
>>>> Oh wait, it breaks the builds on older kernels, that's why I didn't
>>>> apply it :)
>>>>
>>>> Can you provide me with a working backport?
>>>>
>>>
>>> Hi Steve,
>>>
>>> Is there a version of this fix available for stable kernels?
>>>
>>
>> Hi Greg,
>>
>> Mounting SMB3 shares continues to fail for me on 4.4.118 and 4.9.84
>> due to the issues that I have described in detail on this mail thread.
>>
>> Since there is no apparent fix for this bug on stable kernels, could
>> you please consider reverting the original commit that caused this
>> regression?
>>
>> That commit was intended to enhance security, which is probably why it
>> was backported to stable kernels in the first place; but instead it
>> ends up breaking basic functionality itself (mounting). So in the
>> absence of a proper fix, I don't see much of an option but to revert
>> that commit.
>>
>> So, please consider reverting the following:
>>
>> commit 02ef29f9cbb616bf419 "SMB: Validate negotiate (to protect
>> against downgrade) even if signing off" on 4.4.118
>>
>> commit 0e1b85a41a25ac888fb "SMB: Validate negotiate (to protect
>> against downgrade) even if signing off" on 4.9.84
>>
>> They correspond to commit 0603c96f3af50e2f9299fa410c224ab1d465e0f9
>> upstream. Both these patches should revert cleanly. 
> 
> Do you still have this same problem on 4.14 and 4.15?  If so, the issue
> needs to get fixed there, not papered-over by reverting these old
> changes, as you will hit the issue again in the future when you update
> to a newer kernel version.
> 

4.14 and 4.15 work great! (I had mentioned this is in my original bug
report but forgot to summarize it here, sorry).

Thank you!

Regards,
Srivatsa