Forward: Bug#138975: hotplug: /tmp symlink vulnerability

Forward: Bug#138975: hotplug: /tmp symlink vulnerability

[Fumitoshi UKAI]

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Hi,

I received the following bug report.
It actually create any files on tye system by dangling symlinking
in /tmp/test.<number> (touch follows symlinks).

Anyway as report said, I think it's better to touch /tmp itself
instead of touch /tmp/test.$$ and remove it.  
If directory is writable, touch the directory will be success, otherwise
touch will be failed. 

How about this ?

Index: etc/hotplug/ieee1394.agent
===================================================================
RCS file: /cvsroot/linux-hotplug/admin/etc/hotplug/ieee1394.agent,v
retrieving revision 1.3
diff -u -u -r1.3 ieee1394.agent
--- etc/hotplug/ieee1394.agent	4 Jan 2002 18:39:49 -0000	1.3
+++ etc/hotplug/ieee1394.agent	19 Mar 2002 01:36:56 -0000
@@ -33,9 +33,9 @@
 
 # if called too early in booting, things break
 # (bash creates tempfiles)
-if touch /tmp/test.$$ >/dev/null 2>&1
+if touch /tmp >/dev/null 2>&1
 then
-	rm -f /tmp/test.$$
+	: ok
 else
 	mesg Need writable /tmp ...
 	exit 1

Regards,
Fumitoshi UKAI


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From: Zygo Blaxell <zblaxell@feedme.hungrycats.org>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Subject: Bug#138975: hotplug: /tmp symlink vulnerability
Date: Mon, 18 Mar 2002 18:02:38 -0500
Message-ID: <E16n69G-00034f-00@satsuki.furryterror.org>

Package: hotplug
Version: 0.0.20020114-5
Severity: normal
File: /etc/hotplug/ieee1394.agent
Tags: security

Seen in /etc/hotplug/ieee1394.agent:

	if touch /tmp/test.$$ >/dev/null 2>&1
	then
		rm -f /tmp/test.$$
	else
		mesg Need writable /tmp ...
		exit 1
	fi

Not only does this follow symlinks when it executes as root, thereby allowing someone
to create files all over the system, but it also removes innocent files created
under /tmp whose names happen to coincide with the PID of the agent...

A better approach would be to try to create a directory under /tmp.
That won't work if the /tmp disk is full, but on the other hand not much is
going to work in such a state anyway.

An even better approach would be to try to touch /tmp itself--if that
fails, you certainly won't be able to write files in subdirectories
of /tmp.

-- System Information
Debian Release: 3.0
Architecture: i386
Kernel: Linux satsuki 2.4.18-pre7aa2-zb-p3-laptop #1 Sat Feb 9 17:03:54 EST 2002 i686
Locale: LANG=C, LC_CTYPE=

Versions of packages hotplug depends on:
ii  debconf                       1.0.26     Debian configuration management sy
ii  modutils                      2.4.13-3   Linux module utilities.

Re: Forward: Bug#138975: hotplug: /tmp symlink vulnerability

[David Brownell]

Looks right to me, except that some other agent
scripts had the same general need for writable /tmp
so maybe a more generic fix, done once, would be]
a better way to go.

- Dave


----- Original Message ----- 
From: "Fumitoshi UKAI" <ukai@debian.or.jp>
To: <linux-hotplug-devel@lists.sourceforge.net>
Sent: Monday, March 18, 2002 5:39 PM
Subject: Forward: Bug#138975: hotplug: /tmp symlink vulnerability


> Hi,
> 
> I received the following bug report.
> It actually create any files on tye system by dangling symlinking
> in /tmp/test.<number> (touch follows symlinks).
> 
> Anyway as report said, I think it's better to touch /tmp itself
> instead of touch /tmp/test.$$ and remove it.  
> If directory is writable, touch the directory will be success, otherwise
> touch will be failed. 
> 
> How about this ?
> 
> Index: etc/hotplug/ieee1394.agent
> =================================> RCS file: /cvsroot/linux-hotplug/admin/etc/hotplug/ieee1394.agent,v
> retrieving revision 1.3
> diff -u -u -r1.3 ieee1394.agent
> --- etc/hotplug/ieee1394.agent 4 Jan 2002 18:39:49 -0000 1.3
> +++ etc/hotplug/ieee1394.agent 19 Mar 2002 01:36:56 -0000
> @@ -33,9 +33,9 @@
>  
>  # if called too early in booting, things break
>  # (bash creates tempfiles)
> -if touch /tmp/test.$$ >/dev/null 2>&1
> +if touch /tmp >/dev/null 2>&1
>  then
> - rm -f /tmp/test.$$
> + : ok
>  else
>   mesg Need writable /tmp ...
>   exit 1
> 
> Regards,
> Fumitoshi UKAI
> 
> 


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Re: Forward: Bug#138975: hotplug: /tmp symlink vulnerability

[Fumitoshi UKAI]

At Mon, 18 Mar 2002 17:51:17 -0800,
David Brownell wrote:
 
> Looks right to me, except that some other agent
> scripts had the same general need for writable /tmp
> so maybe a more generic fix, done once, would be]
> a better way to go.

I committed this patch.
But I can't find any reason why this check is in ieee1394.agent only.
Which part of ieee1394.agent requires /tmp is writable?
Doesn't other agent need to check as well?

Regards,
Fumitoshi UKAI
 
> ----- Original Message ----- 
> From: "Fumitoshi UKAI" <ukai@debian.or.jp>
> To: <linux-hotplug-devel@lists.sourceforge.net>
> Sent: Monday, March 18, 2002 5:39 PM
> Subject: Forward: Bug#138975: hotplug: /tmp symlink vulnerability
> 
> 
> > Hi,
> > 
> > I received the following bug report.
> > It actually create any files on tye system by dangling symlinking
> > in /tmp/test.<number> (touch follows symlinks).
> > 
> > Anyway as report said, I think it's better to touch /tmp itself
> > instead of touch /tmp/test.$$ and remove it.  
> > If directory is writable, touch the directory will be success, otherwise
> > touch will be failed. 
> > 
> > How about this ?
> > 
> > Index: etc/hotplug/ieee1394.agent
> > =================================> > RCS file: /cvsroot/linux-hotplug/admin/etc/hotplug/ieee1394.agent,v
> > retrieving revision 1.3
> > diff -u -u -r1.3 ieee1394.agent
> > --- etc/hotplug/ieee1394.agent 4 Jan 2002 18:39:49 -0000 1.3
> > +++ etc/hotplug/ieee1394.agent 19 Mar 2002 01:36:56 -0000
> > @@ -33,9 +33,9 @@
> >  
> >  # if called too early in booting, things break
> >  # (bash creates tempfiles)
> > -if touch /tmp/test.$$ >/dev/null 2>&1
> > +if touch /tmp >/dev/null 2>&1
> >  then
> > - rm -f /tmp/test.$$
> > + : ok
> >  else
> >   mesg Need writable /tmp ...
> >   exit 1
> > 
> > Regards,
> > Fumitoshi UKAI
> > 
> > 
> 
> 
> _______________________________________________
> Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
> Linux-hotplug-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel
> 
> 

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