[PATCH][SMB3] allow files to be created with backslash in file name

[Steve French]

On Sat, Jan 2, 2021 at 7:25 PM Jeremy Allison <jra at samba.org> wrote:
>
> On Sat, Jan 02, 2021 at 05:21:16PM -0800, Jeremy Allison via samba-technical wrote:
> >On Sat, Jan 02, 2021 at 06:19:39PM -0600, Steve French wrote:
> >>I agree with the idea of being safe (in the smbclient in this case),
> >>and not returning potentially dangerous file names (even if a very
> >>remote danger to the tool, smbclient in this case), but I am not
> >>convinced that the "user friendly" behavior is to reject the names
> >>with the rather confusing message - especially as it would mean that
> >>inserting a single file with an odd name into a server could make the
> >>whole share unusable for smbclient (e.g. in a backup scenario).  I
>
> FYI, as I pointed out this only happens if you *explicitly*
> set a server parameter that is only expected to be set on
> a share with "clean" (no non-Windows) names.
>
> So just creating a file containing : \ etc. doesn't do
> this - you have to misconfigure the server FIRST.

I agree that with Samba server this is less common (not sure how many
vendors set that smb.conf
parm) but note that "man smb.conf" does not warn that disabling name
mangling will break
smbclient (assuming that local files have been created on the server with one of
the various reserved characters, perhaps over NFS for example).  But
... there are many
other servers, and I wouldn't be surprised if other servers have
sometimes returned files
created by NFS or Ceph or some cluster fs that contain reserved
characters, even if
it is illegal.

> The SMBecho is due to the keepalive failing
We (SMB/CIFS developers) would know that, but I doubt that all users
would realize that
(for example) creating a file over NFS with a reserved character and
then reexporting the
file over SMB with Samba configured with managled names off, or with a
server that
is less strict than Samba.   Seems like it would be better to print a
warning like:
                    "exiting due to invalid character found in file name"
rather than killing the session and ending up with the (to most users)
unehelpful error message.
-- 
Thanks,

Steve