On Friday 27 January 2012 20:07:45 Samuli Suominen wrote:
> On 01/28/2012 02:41 AM, Mike Frysinger wrote:
> > On Friday 27 January 2012 19:18:07 Samuli Suominen wrote:
> >> On 01/28/2012 02:14 AM, Mike Frysinger wrote:
> >>> along these lines, why is cdrtools set*id ?  if we have a "cdrom"
> >>> group, and we assign our cdroms/dvdroms to that group, then we already
> >>> have access control in place and can skip the set*id.
> >> 
> >> cdrtools can't probe the drives without the binary being setuid, or the
> >> user belonging to the 'disk' group (and even that is not enough in some
> >> cases if the permissions vary)
> > 
> > the drives are owned by the "cdrom" group and have group +rw.  so if the
> > user is in the "cdrom" group, why can't they probe the drives ?
> > 
> > "disk" owns the non-removable hard drives.
> > 
> > $ ls -l /dev/sr0 /dev/sg0 /dev/sg6
> > crw-rw---- 1 root disk  21, 0 Jan  6 23:07 /dev/sg0
> > crw-rw---- 1 root cdrom 21, 6 Jan  6 23:07 /dev/sg6
> > brw-rw---- 1 root cdrom 11, 0 Jan 17 22:28 /dev/sr0
> > -mike
> 
> i dont know why, but it does probe also non-removable disks... it probes
> per bus, iirc
> 
> you can try it easily yourself:

this is a failure in cdrecord (not that surprising).  it aborts after the first 
EACCES it gets on /dev/sg# instead of continuing on.  granting set*id to a 
binary because they can't be bothered to try the next device is dumb.

$ sudo mv /dev/sg[0-5] ~/
$ sudo chmod 755 /usr/bin/cdrecord
$ cdrecord -scanbus

Cdrecord-ProDVD-ProBD-Clone 3.01a06 (x86_64-unknown-linux-gnu) Copyright (C) 
1995-2011 Joerg Schilling
TOC Type: 1 = CD-ROM
Linux sg driver version: 3.5.34
Using libscg version 'schily-0.9'.
Using libscg transport code version 'schily-scsi-linux-sg.c-1.95'
Driveropts: 'burnfree'
SCSI buffer size: 32768
scsibus7:
        7,0,0   700) 'TSSTcorp' 'CDDVDW SH-S222L ' 'SB03' Removable CD-ROM
        7,1,0   701) *
        7,2,0   702) *
        7,3,0   703) *
        7,4,0   704) *
        7,5,0   705) *
        7,6,0   706) *
        7,7,0   707) *
-mike