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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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?

thanks,

greg k-h