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<H1>Permissions of /dev/sg* and xsane, xscanimage (was Re: Report on , last CVS snapshot)</H1>
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<STRONG>From:</STRONG> Peter Hackenberg (<A HREF="mailto:phackenberg@aip.de?Subject=Re:%20Permissions%20of%20/dev/sg*%20and%20xsane,%20xscanimage%20(was%20Re:%20Report%20on%20,%20last%20CVS%20snapshot)&In-Reply-To=&lt;Pine.HPP.3.96.1000224084709.10986A-100000@osra2.aip.de&gt;"><EM>phackenberg@aip.de</EM></A>)<BR>
<STRONG>Date:</STRONG> Thu Feb 24 2000 - 01:25:29 PST
<P>
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On Wed, 23 Feb 2000, Oliver Rauch wrote:
<BR>
<P><EM>&gt; Peter Hackenberg wrote:
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; &gt; &gt;
</EM><BR>
<EM>&gt; &gt; &gt; &gt; BTW, as root I can't find the xsane binaries once built and installed...
</EM><BR>
<EM>&gt; &gt; &gt; &gt; I will learn how to modify the path. :-)
</EM><BR>
<EM>&gt; &gt; &gt;
</EM><BR>
<EM>&gt; &gt; &gt; Do not run xsane as root!
</EM><BR>
<EM>&gt; &gt; &gt;
</EM><BR>
<EM>&gt; &gt;
</EM><BR>
<EM>&gt; &gt; Be careful with this, because the SCSI devices are assigned to
</EM><BR>
<EM>&gt; &gt; /dev/sg* at boot time. If some of your SCSI devices are switched off
</EM><BR>
<EM>&gt; &gt; at boot time, your scanner device file (e.g. /dev/sg2) may then
</EM><BR>
<EM>&gt; &gt; be pointing to your hard disk.
</EM><BR>
<EM>&gt; &gt;
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; I think about adding a &quot;root&quot; test to xsane so that xsane exits when
</EM><BR>
<EM>&gt; started as root.
</EM><BR>
<P>That's too restrictive. Sometimes you just want to test as root
<BR>
whether something works or not. Print some (annoying) warning
<BR>
message instead.
<BR>
<P><P>Not running xsane with uid root will only avoid some security
<BR>
problems. But it cannot restrict xsane (or xscanimage or ...) from
<BR>
accidently accessing a sensitive device.
<BR>
<P>Given that under &quot;regular&quot; conditions, i.e. all scsi devices are switched
<BR>
on at boot time,
<BR>
<P>crw-rw---- root disk /dev/sg2 # scanner
<BR>
crw-rw---- root disk /dev/sg3 # some sensitive device
<BR>
<P>and you reboot with the scanner switched off, then /dev/sg2 points
<BR>
to the sensitive device. That is the reason why
<BR>
<P>crw-rw-rw- root disk /dev/sg2
<BR>
<P>should be avoided. But then xsane must be setgid disk
<BR>
<P>-rwxr-sr-x root disk xsane
<BR>
<P>if you don't want to run xsane as root (what you also should not do).
<BR>
<P>The &quot;obvious&quot; solution to give the &quot;sensitive device&quot; a lower scsi number
<BR>
than the scanner is not feasible if that device must have a higher
<BR>
priority. It also fails if you dynamically load/delete scsi devices.
<BR>
<P>I do suggest to eliminate the /dev/scanner symlink business totally,
<BR>
because it is not unlikely that it points to the wrong device.
<BR>
<P>Peter
<BR>
<P><P><PRE>
--
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0325.html">Joe Smith: "Re: Permissions of /dev/sg* and xsane, xscanimage (was Re: Report on , last CVS snapshot)"</A>
<LI><STRONG>Next in thread:</STRONG> <A HREF="0319.html">Petter Reinholdtsen: "Re: Report on last CVS snapshot"</A>
<LI><STRONG>Reply:</STRONG> <A HREF="0325.html">Joe Smith: "Re: Permissions of /dev/sg* and xsane, xscanimage (was Re: Report on , last CVS snapshot)"</A>
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