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______________________________________________________________________________
SuSE Security Announcement
Package: screen
Announcement-ID: SuSE-SA:2001:030
Date: Wednesday, September 5 2001 18:00 MEST
Affected SuSE versions: (6.0, 6.1, 6.2) 6.3, 6.4, 7.0, 7.1, 7.2
Vulnerability Type: local root compromise
Severity (1-10): 5
SuSE default package: yes
Other affected systems: some systems with the screen program
installed setuid root
Content of this advisory:
1) security vulnerability resolved: screen
problem description, discussion, solution and upgrade information
2) pending vulnerabilities, solutions, workarounds
3) standard appendix (further information)
______________________________________________________________________________
1) problem description, brief discussion, solution, upgrade information
screen is a terminal multiplexer program that allows reattaching to
a detached session as well as multi-attached (shared) sessions.
The screen package allows a local attacker to obtain root privileges if
the /usr/bin/screen command is installed setuid root and if a directory
below /tmp/screens/ exists.
The screen program needs root permissions from the setuid-root bit for
two reasons: multi-attached sessions are only possible with root
privileges, and writing terminal allocation information to /var/run/utmp
(the who(1) and finger(1) commands). If the screen command is not running
with special privileges, all functionality except these two features will
continue to work, but the local root compromise will not be possible.
In order to provide the features mentioned, the screen package used to
be installed setuid-root in SuSE Linux distributions.
The update packages that we provide for the supported distributions 6.3,
6.4, 7.0, 7.1 and 7.2 eliminate the error in the source code. In addition
to that, the rpm package does not contain the setuid-bit on the screen
program any more. If there is any more security-related bug in the screen
package or libraries that it is linked against to be found in the future,
these errors will not open local security holes any more. Users of the
screen package who need the multi-attach feature must enable it again by
adding the setuid-bit to the /usr/bin/screen file.
Please note that you should reflect the changes to permissions in the
files /etc/permissions*. If unsure, use the setting "secure local" for
the variable PERMISSION_SECURITY in /etc/rc.config and execute "SuSEconfig"
as root. Alternatively, change the settings for the screen program in
/etc/permissions* and run "chkstat -set <file>" for each file that you
need. Use the command "rpm -qlv screen | grep /usr/bin" to find out which
files to add to the permissions file (/usr/bin/screen is a symlink).
The authors of screen have released the new version screen-3.9.10 that
fixes the multi-attach-error, and some other uncritical bug. Our update
packages contain the necessary patches applied to the version as shipped
with the original distribution.
We thank Christian Hürgemann for reporting this
error on Monday, 3 Sep 2001.
Please download the update package for your distribution and verify its
integrity by the methods listed in section 3) of this announcement.
Then, install the package using the command "rpm -Uhv file.rpm" to apply
the update.
i386 Intel Platform:
SuSE-7.2
ftp://ftp.suse.com/pub/suse/i386/update/7.2/ap1/screen-3.9.8-115.i386.rpm
e85453f50170ecdabe97dd2b33b51e4a
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/screen-3.9.8-115.src.rpm
74ac0119ec42f7c5ad4405a7f1c00f6a
SuSE-7.1
ftp://ftp.suse.com/pub/suse/i386/update/7.1/ap1/screen-3.9.8-115.i386.rpm
fb0a3ba99db246c1f08e3814557858ae
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/screen-3.9.8-115.src.rpm
5edb0caa388be9f1ddc2cd4d0a4f3a54
SuSE-7.0
ftp://ftp.suse.com/pub/suse/i386/update/7.0/ap1/screen-3.9.8-115.i386.rpm
b7bfa891b49db29093f6ab1830d84838
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.0/zq1/screen-3.9.8-115.src.rpm
fb1e3bf070adec10296a59f2d1231c8c
SuSE-6.4
ftp://ftp.suse.com/pub/suse/i386/update/6.4/ap1/screen-3.9.8-115.i386.rpm
a889c9090b0a64eb57a407ee00444491
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/6.4/zq1/screen-3.9.8-115.src.rpm
29b6e24378153a4f9d2445414253759c
SuSE-6.3
ftp://ftp.suse.com/pub/suse/i386/update/6.3/ap1/screen-3.9.8-115.i386.rpm
5a47bdc2407890d9a940c710d4806383
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/6.3/zq1/screen-3.9.8-115.src.rpm
f3bace3114cfcb9b1b6e798ea8b93b34
Sparc Platform:
SuSE-7.1
ftp://ftp.suse.com/pub/suse/sparc/update/7.1/ap1/screen-3.9.8-61.sparc.rpm
3bfe4ac28d54ff2cab6582b2d09f3b75
source rpm:
ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/screen-3.9.8-61.src.rpm
17da9f63ec2b0d48b3593dacfe341a7b
SuSE-7.0
ftp://ftp.suse.com/pub/suse/sparc/update/7.0/ap1/screen-3.9.8-62.sparc.rpm
13037ae193ebd81b92ce1d94d2409421
source rpm:
ftp://ftp.suse.com/pub/suse/sparc/update/7.0/zq1/screen-3.9.8-62.src.rpm
c542f1c51a701ad5dd06d9f9f3701cfb
AXP Alpha Platform:
SuSE-7.1
ftp://ftp.suse.com/pub/suse/axp/update/7.1/ap1/screen-3.9.8-71.alpha.rpm
c5239b5ca727a4f7d54589399b62a5c5
source rpm:
ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/screen-3.9.8-71.src.rpm
4c389bca8641e3c081e992e82bc5065d
SuSE-7.0
ftp://ftp.suse.com/pub/suse/axp/update/7.0/ap1/screen-3.9.8-71.alpha.rpm
9f84734233284fc9f7be494c37a4f857
source rpm:
ftp://ftp.suse.com/pub/suse/axp/update/7.0/zq1/screen-3.9.8-71.src.rpm
31920bb58b696739100e75ce363ade6d
SuSE-6.4
ftp://ftp.suse.com/pub/suse/axp/update/6.4/ap1/screen-3.9.8-71.alpha.rpm
a7f64468ecc5be193795ea3a530d3ead
source rpm:
ftp://ftp.suse.com/pub/suse/axp/update/6.4/zq1/screen-3.9.8-71.src.rpm
dae933854ae9a7efd3e80e09641b9963
SuSE-6.3
ftp://ftp.suse.com/pub/suse/axp/update/6.3/ap1/screen-3.9.8-71.alpha.rpm
f66d9c18a27cd7915d5134528b47c342
source rpm:
ftp://ftp.suse.com/pub/suse/axp/update/6.3/zq1/screen-3.9.8-71.src.rpm
13157d46457be72fd7684ca0cbe6c49b
PPC Power PC Platform:
SuSE-7.1
ftp://ftp.suse.com/pub/suse/ppc/update/7.1/ap1/screen-3.9.8-52.ppc.rpm
090e4781fb4949697fb08f755a0ae12d
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/screen-3.9.8-52.src.rpm
ce19f08412c6517798690fa7d99ed690
SuSE-7.0
ftp://ftp.suse.com/pub/suse/ppc/update/7.0/ap1/screen-3.9.8-52.ppc.rpm
e37b478c4ce85febc13785b4a48c68c0
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/7.0/zq1/screen-3.9.8-52.src.rpm
0594837833e05e430c52421745f1abfa
SuSE-6.4
ftp://ftp.suse.com/pub/suse/ppc/update/6.4/ap1/screen-3.9.8-52.ppc.rpm
53cb3d0fdf964a4013b6aed326d77c9e
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/6.4/zq1/screen-3.9.8-52.src.rpm
89300f304c709a10975f5906bedd1529
______________________________________________________________________________
2) Pending vulnerabilities in SuSE Distributions and Workarounds:
- sendmail
SuSE Security announcement SuSE-SA:2001:028 (sendmail) offers a sendmail
update package for the 7.0-i386 distribution that has a lower version
number than the package in the tree for ftp installation on ftp.suse.com.
If your update rpm command fails with a complaint that the version
installed is newer than the one you wish to be installed, then please
use the "--oldpackage" commandline option to rpm:
"rpm --oldpackage -Uhv sendmail-*.rpm".
We are correcting the problem as soon as possible. The new package
will be named sendmail-8.11.0-10.i386.rpm and should appear on the ftp
server within the next 11 hours. The *-10 package is technically identical
to the *-5 package that is currently available on our ftp server.
______________________________________________________________________________
3) standard appendix: authenticity verification, additional information
- Package authenticity verification:
SuSE update packages are available on many mirror ftp servers all over
the world. While this service is being considered valuable and important
to the free and open source software community, many users wish to be
sure about the origin of the package and its content before installing
the package. There are two verification methods that can be used
independently from each other to prove the authenticity of a downloaded
file or rpm package:
1) md5sums as provided in the (cryptographically signed) announcement.
2) using the internal gpg signatures of the rpm package.
1) execute the command
md5sum
after you downloaded the file from a SuSE ftp server or its mirrors.
Then, compare the resulting md5sum with the one that is listed in the
announcement. Since the announcement containing the checksums is
cryptographically signed (usually using the key security@suse.de),
the checksums show proof of the authenticity of the package.
We disrecommend to subscribe to security lists which cause the
email message containing the announcement to be modified so that
the signature does not match after transport through the mailing
list software.
Downsides: You must be able to verify the authenticity of the
announcement in the first place. If RPM packages are being rebuilt
and a new version of a package is published on the ftp server, all
md5 sums for the files are useless.
2) rpm package signatures provide an easy way to verify the authenticity
of an rpm package. Use the command
rpm -v --checksig
to verify the signature of the package, where is the
filename of the rpm package that you have downloaded. Of course,
package authenticity verification can only target an uninstalled rpm
package file.
Prerequisites:
a) gpg is installed
b) The package is signed using a certain key. The public part of this
key must be installed by the gpg program in the directory
~/.gnupg/ under the user's home directory who performs the
signature verification (usually root). You can import the key
that is used by SuSE in rpm packages for SuSE Linux by saving
this announcement to a file ("announcement.txt") and
running the command (do "su -" to be root):
gpg --batch; gpg < announcement.txt | gpg --import
SuSE Linux distributions version 7.1 and thereafter install the
key "build@suse.de" upon installation or upgrade, provided that
the package gpg is installed. The file containing the public key
is placed at the toplevel directory of the first CD (pubring.gpg)
and at ftp://ftp.suse.com/pub/suse/pubring.gpg-build.suse.de .
- SuSE runs two security mailing lists to which any interested party may
subscribe:
suse-security@suse.com
- general/linux/SuSE security discussion.
All SuSE security announcements are sent to this list.
To subscribe, send an email to
.
suse-security-announce@suse.com
- SuSE's announce-only mailing list.
Only SuSE's security annoucements are sent to this list.
To subscribe, send an email to
.
For general information or the frequently asked questions (faq)
send mail to:
or
respectively.
===================================================
SuSE's security contact is .
The public key is listed below.
===================================================
______________________________________________________________________________
The information in this advisory may be distributed or reproduced,
provided that the advisory is not modified in any way. In particular,
it is desired that the cleartext signature shows proof of the
authenticity of the text.
SuSE GmbH makes no warranties of any kind whatsoever with respect
to the information contained in this security advisory.
Type Bits/KeyID Date User ID
pub 2048R/3D25D3D9 1999-03-06 SuSE Security Team
pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key
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