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

[Jeremy Allison]

On Fri, Jan 01, 2021 at 09:12:14AM -0600, Steve French wrote:
>On Fri, Jan 1, 2021 at 12:00 AM Jeremy Allison <jra at samba.org> wrote:
>>
>> On Thu, Dec 31, 2020 at 09:35:23PM -0600, Steve French via samba-technical wrote:
>> >
>> >This patch may be even more important to Samba, as alternative ways of
>> >storing these files can create more problems. Interestingly Samba
>> >server reports local files with backslashes in them over the wire
>> >without remapping, even though these are illegal in SMB3 which would
>> >cause confusion on the client(s).  Has anyone tried Windows mounting
>>
>> Samba should mangle names containing '\' to 8.3 names.
>
>You were right mangled names was enabled.  But that is also
>interesting - it does expose a bug in smbclient.
>
>When you connect smbclient - doing a ls of a subdirectory with
>reserved characters worked, but doing an ls of the parent (root
>directory of share) caused smbclient to disconnect.  See below
>
>smb: \> ls rsvd-chars
>  rsvd-chars                          D        0  Fri Jan  1 08:55:49 2021
>
>556368460 blocks of size 1024. 296010296 blocks available
>smb: \> ls
>  .                                   D        0  Fri Jan  1 08:54:28 2021
>  ..                                  D        0  Thu Dec 31 21:42:28 2020
>  topdir                              D        0  Mon Dec 14 16:01:25 2020
>  lock1.txt                           A      200  Fri Dec 18 12:28:18 2020
>  lock_rw_shared.dat                  A      200  Fri Dec 18 12:28:18 2020
>  lock_rw_exclusive.dat               A      200  Fri Dec 18 12:28:18 2020
>  autounlock.txt                      A      200  Fri Dec 18 12:28:18 2020
>is_bad_finfo_name: bad finfo->name
>NT_STATUS_INVALID_NETWORK_RESPONSE listing \*

This is coming from the following code which is designed to
protect the client from a malicious server returning a '\' or '/'
character in an filename component.

/****************************************************************************
  Check if a returned directory name is safe.
****************************************************************************/

static NTSTATUS is_bad_name(bool windows_names, const char *name)
{
         const char *bad_name_p = NULL;

         bad_name_p = strchr(name, '/');
         if (bad_name_p != NULL) {
                 /*
                  * Windows and POSIX names can't have '/'.
                  * Server is attacking us.
                  */
                 return NT_STATUS_INVALID_NETWORK_RESPONSE;
         }
         if (windows_names) {
                 bad_name_p = strchr(name, '\\');
                 if (bad_name_p != NULL) {
                         /*
                          * Windows names can't have '\\'.
                          * Server is attacking us.
                          */
                         return NT_STATUS_INVALID_NETWORK_RESPONSE;
                 }
         }
         return NT_STATUS_OK;
}