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

[Philipp Middendorf]

Hi Michael,

I see, thanks for the explanations! It's indeed curious that the usual 
user/group mechanism isn't used here. I will ask the people at DESY what's 
going on here in detail, but I heard some time ago that ACLs are being used, 
which seem to work in parallel to the usual Linux rights. Maybe tramp doesn't 
support this?

Is there a way to tell tramp to simply omit these permission checks? Do you 
know which purpose the checks serve? I mean, couldn't tramp just try to open 
files and then fail if the OS gives an error?

Cheers
Philipp

> Michael Albinus <michael.albinus@gmx.de> hat am 15.06.2024 11:12 CEST 
> geschrieben:
> 
>  
> 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.