[TiLP-devel] [ tilp-Bugs-1731776 ] Bad permissions check on /dev/ttySx

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Bugs item #1731776, was opened at 2007-06-06 02:50
Message generated for change (Comment added) made by rossaxe
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Category: None
Group: None
Status: Open
Resolution: Accepted
Priority: 5
Private: No
Submitted By: Ross Kendall Axe (rossaxe)
Assigned to: Romain Liévin (roms)
Summary: Bad permissions check on /dev/ttySx

Initial Comment:
TiLP produces the following output in the terminal window when attempting to open a serial link:

ticables-INFO: Check for tty usability:
ticables-INFO:     node /dev/ttyS0: exists
ticables-INFO:     permissions/user/group: -rw-rw---- root users
ticables-INFO:     is user can r/w on device: no
ticables-INFO:     are others can r/w on device: no
ticables-INFO:     is the user 'ross' in the group 'users': no
ticables-INFO:     => you should add your username at the group 'users' in '/etc/group'
ticables-INFO:     => you will have to restart you session, too

However, 'id ross' clearly indicates that I'm in the users group, in case I didn't already know that ;-)

$ id ross
uid=1004(ross) gid=100(users) groups=100(users),11(floppy),17(audio),18(video),19(cdrom),93(scanner)

Any attempt to use the link therefore fails since it never got initialised.  As to why it failed to notice that I have access, well, I'm not sure.  It could be that it's because it's my primary group, or because my passwd entry is accessed via nss_ldap.  I imagine it would also fail if I was using ACLs.

It seems to be that TiLP ought to simply use open("/dev/ttySx", O_RDWR) to check access rather than trying to be too clever and attempting to second guess the kernel's access rules.

Meanwhile, 'chmod 0666 /dev/ttyS?' is a suitable workaround for this problem :-)

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>Comment By: Ross Kendall Axe (rossaxe)
Date: 2007-07-04 23:46

Message:
Logged In: YES 
user_id=1206088
Originator: YES

Yeah, putting my username into /etc/group does also work around the
problem.  My username wasn't in 'group' on the LDAP server either though,
only in 'passwd' (where my GID is set to the GID of the users group, of
course).

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Comment By: Romain Liévin (roms)
Date: 2007-07-04 13:58

Message:
Logged In: YES 
user_id=136160
Originator: NO

ticables2 library is parsing /etc/group for entries. Is your username in
the same line as the 'users' line in this file? nss_ldap access may explain
your problem...

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