[gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[KH]

>>>Warning: Open by 'devname' is unintentional and not supported.
>>>     

>>
>> If you like to get correct behavior, do not use unsupported dev= parameters.
>>   

>I will need to read the manual again for this  :-) 

I have been trying to get the correct behavior but I just cannot manage to do so.

as root:
#cdrecord --scanbus
the following two would be my dvd-burners. One is usb and one is ide.

scsibus5:
	5,0,0	500) 'LITE-ON ' 'DVDRW SOHW-1633S' 'BS0H' Removable CD-ROM
	5,1,0	501) *
	5,2,0	502) *
	5,3,0	503) *
	5,4,0	504) *
	5,5,0	505) *
	5,6,0	506) *
	5,7,0	507) *
scsibus1001:
	1001,0,0 100100) 'HL-DT-ST' 'DVDRRW GWA-4164B' '1.03' Removable CD-ROM
	1001,1,0 100101) *
	1001,2,0 100102) *
	1001,3,0 100103) *
	1001,4,0 100104) *
	1001,5,0 100105) *
	1001,6,0 100106) *
	1001,7,0 100107) *

man says: dev=scsibus,target,lun

#cdrecord -dao -v -gracetime=3 -dev=5,0,0 dvd.iso

so then I only can run this as root. On the other hand there is a Average write speed   7.3x.
Running as user with the old command I only had 2.?x.

Is this normal behavior?

kh

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Joerg Schilling]

KH <gentoo-user@konstantinhansen.de> wrote:

> man says: dev=scsibus,target,lun
>
> #cdrecord -dao -v -gracetime=3 -dev=5,0,0 dvd.iso
>
> so then I only can run this as root. On the other hand there is a Average write speed   7.3x.
> Running as user with the old command I only had 2.?x.

Sorry, but I don't understand your problem.

Please try to use a different wording

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[KH]

Joerg Schilling schrieb:
> KH <gentoo-user@konstantinhansen.de> wrote:
>
>   
>> man says: dev=scsibus,target,lun
>>
>> #cdrecord -dao -v -gracetime=3 -dev=5,0,0 dvd.iso
>>
>> so then I only can run this as root. On the other hand there is a Average write speed   7.3x.
>> Running as user with the old command I only had 2.?x.
>>     
>
> Sorry, but I don't understand your problem.
>
> Please try to use a different wording
>
> Jörg
>
>   
Hi,
I am sorry for my bad English.
I used to run all my cdrecord commands as user. I am unable to run the
command in the format using dev=scsibus,target,lun as user (I can do so
as root), but I am able to burn a cd as user when using dev=/dev/cdrom.
With the first method the average write speed seems to be much faster
than with the second one.
I just wander if this is normal behavior. I always followed
http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
"[snip]Replace /<device>/ with your dvd device (for example
/dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?

kh

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Dale]

KH wrote:
> Joerg Schilling schrieb:
>   
>> KH <gentoo-user@konstantinhansen.de> wrote:
>>
>>   
>>     
>>> man says: dev=scsibus,target,lun
>>>
>>> #cdrecord -dao -v -gracetime=3 -dev=5,0,0 dvd.iso
>>>
>>> so then I only can run this as root. On the other hand there is a Average write speed   7.3x.
>>> Running as user with the old command I only had 2.?x.
>>>     
>>>       
>> Sorry, but I don't understand your problem.
>>
>> Please try to use a different wording
>>
>> Jörg
>>
>>   
>>     
> Hi,
> I am sorry for my bad English.
> I used to run all my cdrecord commands as user. I am unable to run the
> command in the format using dev=scsibus,target,lun as user (I can do so
> as root), but I am able to burn a cd as user when using dev=/dev/cdrom.
> With the first method the average write speed seems to be much faster
> than with the second one.
> I just wander if this is normal behavior. I always followed
> http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
> "[snip]Replace /<device>/ with your dvd device (for example
> /dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?
>
> kh
>
>
>   

Is the user you are attempting to run these commands as a member of the
cd and cdrw groups?  Usually if a command works as root but not a user,
it is a permissions problem which is fixed by being in the correct
group.  I say usually.

Dale

:-)  :-) 

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Joerg Schilling]

Dale <rdalek1967@gmail.com> wrote:

> > I am sorry for my bad English.
> > I used to run all my cdrecord commands as user. I am unable to run the
> > command in the format using dev=scsibus,target,lun as user (I can do so
> > as root), but I am able to burn a cd as user when using dev=/dev/cdrom.
> > With the first method the average write speed seems to be much faster
> > than with the second one.
> > I just wander if this is normal behavior. I always followed
> > http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
> > "[snip]Replace /<device>/ with your dvd device (for example
> > /dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?
> >
>
> Is the user you are attempting to run these commands as a member of the
> cd and cdrw groups?  Usually if a command works as root but not a user,
> it is a permissions problem which is fixed by being in the correct
> group.  I say usually.

Not true in the case of cdrecord.

The Linux kernel always needed root privs to burn media before 2004.
In 2004 a security bug was introduced that allowed to send any SCSI 
command to any drive.

In Autumn 2004 this bug was not fixed but the SCSI Linux kernel interface
was changed in an incompatible way. Now _some_ SCSI commands work as non-root.

SCSI is a try and error protocol and cdrecord checks which commands are working.
If it is possible to burn with the limuted non-root command set, it _may_ work
but there is a high risk for buffer underruns. In this case cdrecord believes 
that you own a really dumb burner that does not support most of the nice 
features....

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Dale]

Joerg Schilling wrote:
> Dale <rdalek1967@gmail.com> wrote:
>
>   
>>> I am sorry for my bad English.
>>> I used to run all my cdrecord commands as user. I am unable to run the
>>> command in the format using dev=scsibus,target,lun as user (I can do so
>>> as root), but I am able to burn a cd as user when using dev=/dev/cdrom.
>>> With the first method the average write speed seems to be much faster
>>> than with the second one.
>>> I just wander if this is normal behavior. I always followed
>>> http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
>>> "[snip]Replace /<device>/ with your dvd device (for example
>>> /dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?
>>>
>>>       
>> Is the user you are attempting to run these commands as a member of the
>> cd and cdrw groups?  Usually if a command works as root but not a user,
>> it is a permissions problem which is fixed by being in the correct
>> group.  I say usually.
>>     
>
> Not true in the case of cdrecord.
>
> The Linux kernel always needed root privs to burn media before 2004.
> In 2004 a security bug was introduced that allowed to send any SCSI 
> command to any drive.
>
> In Autumn 2004 this bug was not fixed but the SCSI Linux kernel interface
> was changed in an incompatible way. Now _some_ SCSI commands work as non-root.
>
> SCSI is a try and error protocol and cdrecord checks which commands are working.
> If it is possible to burn with the limuted non-root command set, it _may_ work
> but there is a high risk for buffer underruns. In this case cdrecord believes 
> that you own a really dumb burner that does not support most of the nice 
> features....
>
> Jörg
>
>   

So that I have a better understanding of this, if he is not a member of
the cd/cdrw group then the command would still work as a user?

Dale

:-)  :-) 

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Joerg Schilling]

Dale <rdalek1967@gmail.com> wrote:

> > In Autumn 2004 this bug was not fixed but the SCSI Linux kernel interface
> > was changed in an incompatible way. Now _some_ SCSI commands work as non-root.
> >
> > SCSI is a try and error protocol and cdrecord checks which commands are working.
> > If it is possible to burn with the limuted non-root command set, it _may_ work
> > but there is a high risk for buffer underruns. In this case cdrecord believes 
> > that you own a really dumb burner that does not support most of the nice 
> > features....
> >
> > Jörg

> So that I have a better understanding of this, if he is not a member of
> the cd/cdrw group then the command would still work as a user?

Since the original security bug hass not been fxed, you are able so send
a limit set of SCSI commands if you are able to open the device read-only.
Libscg opens the devices read/write, so the only effect of such a grup 
membership is that cdrecord is able to open the device.

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Dale]

Joerg Schilling wrote:
> Dale <rdalek1967@gmail.com> wrote:
>
>   
>>> In Autumn 2004 this bug was not fixed but the SCSI Linux kernel interface
>>> was changed in an incompatible way. Now _some_ SCSI commands work as non-root.
>>>
>>> SCSI is a try and error protocol and cdrecord checks which commands are working.
>>> If it is possible to burn with the limuted non-root command set, it _may_ work
>>> but there is a high risk for buffer underruns. In this case cdrecord believes 
>>> that you own a really dumb burner that does not support most of the nice 
>>> features....
>>>
>>> Jörg
>>>       
>
>   
>> So that I have a better understanding of this, if he is not a member of
>> the cd/cdrw group then the command would still work as a user?
>>     
>
> Since the original security bug hass not been fxed, you are able so send
> a limit set of SCSI commands if you are able to open the device read-only.
> Libscg opens the devices read/write, so the only effect of such a grup 
> membership is that cdrecord is able to open the device.
>
> Jörg
>
>   

Then what is the point of having a cd/cdrw group?  It doesn't seem to
have "secured" much of anything by having it.

Dale aka confused.  It's ok.  It's normal for me.

:-)  :-) 

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Joerg Schilling]

Dale <rdalek1967@gmail.com> wrote:

>
> Then what is the point of having a cd/cdrw group?  It doesn't seem to
> have "secured" much of anything by having it.
>
> Dale aka confused.  It's ok.  It's normal for me.
>

Well, I did never propose to go this way. The group you are talkign about 
is an "invention" of some people who did not understand the background.
As a result, some of them even tried to modify the cdrecord source code 
and finally ended up with something that has more problems than the original 
software.

At cdrecord level, the effects are not as bad as they are at different places.
The security bug in Linux in 2004 was "used" by some GUIs and the result is that
the authors included direct SCSI code into the GUI code. This resultet in 
non-portable code because no other OS allows to send SCSI commands without 
special privileges.

Simple conclusion: just follow the documentation in the man pages ;-)
			Install cdrecord suid root on Linux.

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Volker Armin Hemmann]

On Dienstag 07 Oktober 2008, KH wrote:
> Joerg Schilling schrieb:
> > KH <gentoo-user@konstantinhansen.de> wrote:
> >> man says: dev=scsibus,target,lun
> >>
> >> #cdrecord -dao -v -gracetime=3 -dev=5,0,0 dvd.iso
> >>
> >> so then I only can run this as root. On the other hand there is a
> >> Average write speed   7.3x. Running as user with the old command I only
> >> had 2.?x.
> >
> > Sorry, but I don't understand your problem.
> >
> > Please try to use a different wording
> >
> > Jörg
>
> Hi,
> I am sorry for my bad English.
> I used to run all my cdrecord commands as user. I am unable to run the
> command in the format using dev=scsibus,target,lun as user (I can do so
> as root), but I am able to burn a cd as user when using dev=/dev/cdrom.
> With the first method the average write speed seems to be much faster
> than with the second one.
> I just wander if this is normal behavior. I always followed
> http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
> "[snip]Replace /<device>/ with your dvd device (for example
> /dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?
>
> kh

no

Re: [gentoo-user] cdrecord - devname - was burning a dvd+r dl...

[Joerg Schilling]

KH <gentoo-user@konstantinhansen.de> wrote:

> I am sorry for my bad English.
> I used to run all my cdrecord commands as user. I am unable to run the
> command in the format using dev=scsibus,target,lun as user (I can do so
> as root), but I am able to burn a cd as user when using dev=/dev/cdrom.

If the first method only works as root, you did not install cdrecord correctly.
You need to install it suid root. If you are able to burn using dev=/dev/cdrom,
there may be a security hole in your system. In any case, this way you cannot
send all needed SCSI command to your drive as without root permission, the 
Linux kernel silently filters away some of the SCSI commands needed by cdrecord.

> With the first method the average write speed seems to be much faster
> than with the second one.

The first method is the official one. There is absolutely no garantee that the 
second method works at all.

> I just wander if this is normal behavior. I always followed
> http://gentoo-wiki.com/HOWTO_Create_a_DVD:Burn where it says:
> "[snip]Replace /<device>/ with your dvd device (for example
> /dev/dvd)[snip]" So the wiki seems to be wrong, isn't it?

This is wrong. The official supported method is to use dev=b,t,l

Jörg

-- 
 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily