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

From: "Srivatsa S. Bhat" <srivatsa@csail.mit.edu>
To: Steve French <smfrench@gmail.com>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Thomas Backlund" <tmb@mageia.org>,
	"Aurélien Aptel" <aaptel@suse.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Stable <stable@vger.kernel.org>,
	"Ronnie Sahlberg" <lsahlber@redhat.com>,
	"Pavel Shilovskiy" <pshilov@microsoft.com>,
	CIFS <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH 4.13 28/43] SMB3: Validate negotiate request must always be signed
Date: Thu, 1 Mar 2018 12:51:09 -0800	[thread overview]
Message-ID: <188c02d6-e27f-235c-a833-021f7304161b@csail.mit.edu> (raw)
In-Reply-To: <CAH2r5ms9mpdYOFYQo5gck9XAsTzZpHe75GHCgd_xCc25suSBHQ@mail.gmail.com>

On 3/1/18 12:12 PM, Steve French wrote:
> So far I haven't been able to reproduce this on the current 4.9 stable
> tree with vers=3.0 or with default (vers=1.0 for these older kernels).
> 

Maybe the problem also depends on the particular version of Windows
that hosts the SMB shares? I'm using Windows Server 2016 (Version
1607, OS Build 14393.693). With vers=3.0, the issue is reproducible
every time, but vers=1.0 works fine.

Regards,
Srivatsa

> On Tue, Feb 27, 2018 at 11:56 AM, Steve French <smfrench@gmail.com> wrote:
>> This shouldn't be too hard to figure out if willing to backport a
>> slightly larger set of fixes to the older stable, but I don't have a
>> system running 4.9 stable.
>>
>> Is this the correct stable tree branch?
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/log/?h=linux-4.9.y
>>
>> On Tue, Feb 27, 2018 at 11:45 AM, Srivatsa S. Bhat
>> <srivatsa@csail.mit.edu> wrote:
>>> On 2/27/18 4:40 AM, Greg Kroah-Hartman wrote:
>>>> On Tue, Feb 27, 2018 at 01:22:31AM -0800, Srivatsa S. Bhat wrote:
>>>>> 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@gmail.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@gmail.com>
>>>>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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).
>>>>
>>>>
>>>> Then what is the bugfix that should be applied here in order to keep
>>>> things working with these patches applied?
>>>>
>>>
>>> That would be the one mentioned in the subject line of this thread :)
>>> However, a working backport of that fix is not available for 4.4 and
>>> 4.9, hence the trouble.
>>>
>>> It looks like we are reconstructing elements of this email thread all
>>> over again, so let me quickly summarize the status so far:
>>>
>>> In 4.14/4.15/mainline,
>>> - commit 0603c96f3af50e2f9 (SMB: Validate negotiate (to protect against
>>>   downgrade) even if signing off) caused mount regression with SMB v3.
>>>
>>> - commit 4587eee04e2ac7ac3 (SMB3: Validate negotiate request must
>>>   always be signed) fixed the issue.
>>>
>>> - [ There was a lot of code churn in the CIFS/SMB codebase between
>>>     these two commits in mainline. ]
>>>
>>> In this email thread, you backported the fix to stable 4.13. Thomas
>>> noticed that the problematic commit had also made it to stable series
>>> such as 4.4 and 4.9, and requested a backport of the fix to those
>>> trees as well. However, a straight-forward backport of the fix to 4.4
>>> and 4.9 breaks the build, so no fix was available for those kernels.
>>>
>>> I investigated this and tried to produce a working backport of the fix
>>> to 4.4 and 4.9, but didn't succeed, despite trying several variations
>>> as well as suggestions from Aurelien [1][2]. So, given that there is
>>> still no known fix for the mount regression on 4.4 and 4.9 stable
>>> series at this point, I decided to request a revert of the problematic
>>> commit that caused the regression in those kernels.
>>>
>>> [1]. https://lkml.org/lkml/2018/1/3/892
>>> [2]. https://lkml.org/lkml/2018/1/29/1009
>>>
>>> Regards,
>>> Srivatsa
>>
>>
>>
>> --
>> Thanks,
>>
>> Steve
> 
> 
> 