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
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