[debbugs-tracker] bug#29455: closed (backup-by-copying ACL Operation not permitted with Windows 7 and Samba)

[GNU bug Tracking System]

Your message dated Sun, 29 Sep 2019 02:11:45 +0200
with message-id <CADwFkmmj01ARRt+UKc4uWOBd78BeAPHFf82BWrPNJ4p=address@hidden>
and subject line Re: bug#29455: backup-by-copying ACL Operation not permitted 
with Windows 7 and Samba
has caused the debbugs.gnu.org bug report #29455,
regarding backup-by-copying ACL Operation not permitted with Windows 7 and Samba
to be marked as done.

(If you believe you have received this mail in error, please contact
address@hidden.)


-- 
29455: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=29455
GNU Bug Tracking System
Contact address@hidden with problems

--- Begin Message --- Subject: backup-by-copying ACL Operation not permitted with Windows 7 and Samba Date: Sun, 26 Nov 2017 22:59:33 +0800

Hi,

Local: Windows 7

GNU Emacs 27.0.50 (build 1, x86_64-w64-mingw32) of 2017-11-24

(backup-by-copying t)

File is on a server which is mapped as network driver in Windows 7. It seems a samba according to the SID below.

The SDDL from file-acl is

"O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)"

After I edited the file and write it, the backup meets error:

Debugger entered--Lisp error: (file-error "Setting ACL" "Operation not permitted" "c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~")
  set-file-acl("c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~" "O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)")
  set-file-extended-attributes("c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~" ((acl . "O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)") (selinux-context nil nil nil nil)))
  backup-buffer-copy("i:/power/permutation_test_fixed_IA_time.r" "c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~" 438 ((acl . "O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)") (selinux-context nil nil nil nil)))
  backup-buffer()
  basic-save-buffer-2()
  basic-save-buffer-1()
  basic-save-buffer(t)
  save-buffer(1)
  funcall-interactively(save-buffer 1)
  call-interactively(save-buffer nil nil)
  command-execute(save-buffer)

The ACL of a local file looks like:

"O:S-1-5-21-1213861250-xxx-207145G:DUD:AI(A;ID;FA;;;SY)(A;ID;FA;;;BA)(A;ID;FA;;;S-1-5-21-1213861250-xx-207145)(A;ID;FA;;;LA)"

I think it is a bug because:

1. I have the write access to the mapped network driver

2. If I copy a local file to the mapped network driver, the ACL would be set up well.

So I don't think there should be a write permission in this backup case.

Best Regards

Shuguang Sun

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#29455: backup-by-copying ACL Operation not permitted with Windows 7 and Samba
>
>
>
>
> Date: 
>
> Sun, 29 Sep 2019 02:11:45 +0200
>
>
>
>
> Eli Zaretskii <address@hidden> writes:
>
> >> From: Shuguang Sun <address@hidden>
> >> Date: Tue, 28 Nov 2017 18:43:53 +0800
> >> Cc: address@hidden
> >>
> >>  Thanks, but that's not what I asked.  I asked you to create a local
> >>  file (which I call "SOME-FILE" below, replace that with the actual
> >>  name of the file), and then type this inside Emacs:
> >>
> >>    M-: (set-file-acl "SOME-FILE" 
> >> "O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)
> >>  (A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)") RET
> >>
> >> It raises the same error message:
> >> (file-error "Setting ACL" "Operation not permitted" 
> >> "c:/Users/username/Documents/base/subtitle.txt")
> >>
> >> or
> >> eval: Setting ACL: Operation not permitted, 
> >> c:/Users/username/HOME/.emacs.d/autosave/.bashrc.~1~
> >
> > OK, I think I understand what causes this: the problem is with setting
> > the owner of the file to a user whose SID the local system doesn't
> > recognize, because it's not a local user.  If you omit the
> > O:S-1-22-1-79077G:S-1-22-2-108 part from the argument, the
> > set-file-acl call will most probably succeed.
> >
> > I think that Emacs works correctly in this case: it tries to preserve
> > the ACLs of the original file in the backup file, and when that fails,
> > falls back to preserving only the read-write mode bits.  Your original
> > problem was caused by debug-on-error being non-nil, which shouldn't be
> > done except when debugging something.
> >
> > I don't see how we could avoid showing the error message, because
> > Emacs cannot possibly know which user SID values are known to the
> > local system.  When you configure your backups of files from networked
> > drives to be stored on a local disk, you should realize that you run
> > the risk of having these problems with preserving extended
> > permissions.
> >
> > So I think we see Emacs working as designed, and this bug should be
> > closed.
>
> According to the above, this bug should be closed.  I'm doing so now.
>
> Best regards,
> Stefan Kangas
>
>
> --- End Message ---