tramp (2.6.0.29.1) : incorrect parsing of group with "-" in name

[Gael Le Mignot]

Hello,

After upgrading from GNU Emacs 28.2 to GNU Emacs 29.1 (Debian packages) I
noticed a regression when I try to open a file on a remote host where my
user has write access through its group : it's opened in read-only mode.

The command I used :
emacs -nw -Q --eval "(setq tramp-verbose 7)" 
/ssh:dockdev.pilotsystems.net:/home/crfpa/foo.txt

The permission of the file :
-rw-rw-r-- 1 crfpa crfpa 19 Oct 27 10:47 /home/crfpa/foo.txt

The result of id for my user on the remote host :
uid=10002(kilobug) gid=10002(kilobug) 
groups=10002(kilobug),4(adm),33(www-data),998(docker),1000(crfpa),1002(wpk),1003(probarreau),1004(ae)

There is no SELinux or ACL or anything of that kind.

After looking at the *debug tramp/ssh dockdev.pilotsystems.net* buffer
that seems to be the issue :

10:28:20.336793 tramp-send-command (6) # /bin/id
10:28:20.342457 tramp-wait-for-regexp (6) # 
uid=10002(kilobug) gid=10002(kilobug) 
groups=10002(kilobug),4(adm),33(www-data),998(docker),1000(crfpa),1002(wpk),1003(probarreau),1004(ae)
///ac59c02ea7871e6263e190f14ec29c44#$
10:28:20.342588 tramp-get-connection-property (7) # process-buffer nil; cache 
used: t
10:28:20.342699 tramp-set-connection-property (7) # uid-integer 10002
10:28:20.342764 tramp-set-connection-property (7) # uid-string kilobug
10:28:20.342815 tramp-set-connection-property (7) # gid-integer 10002
10:28:20.342884 tramp-set-connection-property (7) # gid-string kilobug
10:28:20.342934 tramp-set-connection-property (7) # groups-integer (10002 4)
10:28:20.342991 tramp-set-connection-property (7) # groups-string (kilobug adm)

The parsing of the groups I belong to stops when it reaches "www-data"
which has "-" in its name. If I remove myself from the group, then it
works (file is properly opened in read-write mode). I got the issue
confirmed by another user of #emacs IRC channel.

Version information :

Emacs  : GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, 
cairo version 1.16.0)
 of 2023-08-30, modified by Debian
Package: tramp (2.6.0.29.1 nil/nil)

The full *debug tramp/ssh dockdev.pilotsystems.net* buffer is available
at https://kilobug.net/debug-29.1.txt

Regards,
-- 
Gaël Le Mignot - gael@pilotsystems.net
Pilot Systems - 82, rue de Pixérécourt - 75020 Paris
Tel : +33 1 44 53 05 55 - www.pilot-systems.net
Découvrez notre offre Cloud privé 100% infogéré - www.pilotsystems.net/cloud/