Re: "Permission denied" from dired, but not from ido completion in tramp

[Michael Albinus]

Philipp Middendorf <pmidden@mailbox.org> writes:

> Hi Michael,

Hi Philipp,

> thanks for digging through that giant of a log file. It seems you
> conclude that tramp's behavior is fine as it is. But is it? I can
> clearly access the files and directories, manually via "ssh ...; cd
> ...;" and even through tramp, as demonstrated via ido. But then with
> dired, tramp can somehow not do it anymore? Is tramp doing an extra
> permissions check here that fails, or what's the deeper reason behind
> the error? In other words, what's different from the way tramp
> accesses files vs. tramp+ido or me ssh'ing into the machine?

The problem is the call of access-file, which checks, whether a file or
directory is accessible. Internally, it calls file-accessible-directory-p.

This has a simple implementation in Tramp:

--8<---------------cut here---------------start------------->8---
(defun tramp-handle-file-accessible-directory-p (filename)
  "Like `file-accessible-directory-p' for Tramp files."
  (and (file-directory-p filename)
       (file-readable-p filename)))
--8<---------------cut here---------------end--------------->8---

And this fails for the file-readable-p part.

I suspect, that ido doesn't call access-file for the directory. However
I'm curious to understand why ido can read files in that directory,
although it has permissions "dr-xr-x---", and you are neither the user
"fsdata" nor in the "fsdata" group. Is there a hidden setting on that
machine, that you can read the contents of the directory nevertheless?

> PS: I'm in the Hamburg branch of DESY, but we're in close relations
> with Zeuthen. Funny that you know of it. :)

Well, I'm living in the neighbor village of Zeuthen, in Wildau. And
decades ago, I've worked for a research institute in Berlin Adlershof,
which was a spin-off of the predecessor of desy Zeuthen
<https://en.wikipedia.org/wiki/DESY#Zeuthen>. Achhhh ...

> Cheers
> Philipp

Best regards, Michael.