Re: 22.1.50; insert-file-contents is slow under tramp

[Michael Albinus <michael.albinus@gmx.de>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> How can you do that?  Let's say I access a file of user BAR from user FOO,
> how would you go about doing it in such a way that user TOTO can never see
> the content of the file?  BAR can't use `chown' (unless it's root).

BAR must give away the ownership of the temporary file to FOO. See
this test (BAR is albinus, FOO is hostmann). Any TOTO cannot see the
contents of the file, despite she is root - in this case we can forget
security at all.

# whoami
albinus
# touch stefan
# chmod 0400 stefan
# ll stefan
-r--------   1 albinus  smc3            0 Aug 27 16:36 stefan
# chown hostmann stefan 
# ll stefan
-r--------   1 hostmann smc3            0 Aug 27 16:36 stefan
# cat stefan
cat: stefan: Permission denied

Note that we are speaking about temporary files. Either FOO or BAR is
always me (locally), for the other user I have a Tramp connection
capable to send UNIX commands. I can send commands under both user
permissions in the order I do need. It's a kind of puzzling who must
give ownership to whom (it depends on the copying direction), but it's
a finite number of cases only.

>         Stefan

Best regards, Michael.