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CONECTIVA LINUX SECURITY ANNOUNCEMENT
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PACKAGE : openssh
SUMMARY : Remote vulnerability in OpenSSH
DATE : 2002-06-25 17:12:00
ID : CLA-2002:500
RELEVANT
RELEASES : 6.0, 7.0, 8
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DESCRIPTION
OpenSSH[1] is a very popular and versatile tool that uses encrypted
connections between hosts and is commonly used for remote
administration.
The OpenSSH development teem announced[2] that there is a serious
remote vulnerability in this service and that there is no fix for
this problem at this time. No further details have been released
about the vulnerability.
OpenSSH 3.3, however, implements by default a new feature called
"PrivilegeSeparation" that, according to the authors, prevents this
and future vulnerabilities, or at least mitigates their impact
severely. The OpenSSH team is strongly recommending that, even though
this version does not fix the issue, all users upgrade as soon as
possible due to this new security feature.
The PrivilegeSeparation[6] feature creates a new "sshd" process that
handles the network traffic and interacts with the remote user. This
process is unprivileged, running under an "sshd" userid and chrooted
in an emtpy directory called /var/emtpy.
This is a new feature of OpenSSH and there are some pending issues
(specially regarding PAM) that are being addressed:
- authentication via KeyboardInteractive does not work with
PrivilegeSeparation yet. This affects, for example, Kerberos5 logins
with the SSH1 protocol;
- by default data compression ("UseCompression yes" in sshd_config)
cannot be used with PrivilegeSeparation in 2.2 kernels. The packages
provided with this update, though, have a patch done by Solar
Designer (developer from the Openwall[4] project) to address this and
allow compression and PrivilegeSeparation in 2.2 kernels. But this
issue is still being addressed by the OpenSSH developers.
- expired passwords do not work with PrivilegeSeparation yet.
Previously the user got the chance to change his/her expired password
after logging in. With PrivilegeSeparation, the user is instantly
denied access if his/her password has expired.
Again, it is important to note that the 3.3p1 version still has a
vulnerability, but that the use of PrivilegeSeparation greatly
mitigates its impact and is therefore a recommended upgrade.
The OpenSSH team is working hard to address these remaining issues
with PrivilegeSeparation on several platforms, including GNU/Linux,
and also in fixing the vulnerability. There will be other releases in
the following days. In the meantime, the use of PrivilegeSeparation
in this new OpenSSH release is strongly recommended.
SOLUTION
It is recommended that all OpenSSH users upgrade their packages. The
sshd service will be restarted automatically if it is already running
before the upgrade.
It has been verified, however, that the service restart command
issued during the upgrade keeps an open file descriptor if done
remotely, which will keep the terminal open even after logout (also
known as "hang on exit" problem). Therefore, we recommend that a
manual "/sbin/service sshd restart" command be issued if the upgrade
is being done remotely to prevent this behaviour. We are still
investigating the issue.
REFERENCES
1.http://www.openssh.com
2.http://marc.theaimsgroup.com/?l=openssh-unix-dev&m=102495293705094&w=2
3.http://lwn.net/Vulnerabilities/3290/
4.http://www.openwall.com/Owl/
5.http://distro.conectiva.com.br/pipermail/seguranca/2002-June/002864.html
6.http://www.citi.umich.edu/u/provos/ssh/privsep.html
DIRECT DOWNLOAD LINKS TO THE UPDATED PACKAGES
ftp://atualizacoes.conectiva.com.br/6.0/SRPMS/openssh-3.3p1-1U60_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/openssh-3.3p1-1U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/openssh-askpass-3.3p1-1U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/openssh-askpass-gnome-3.3p1-1U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/openssh-clients-3.3p1-1U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/openssh-server-3.3p1-1U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/SRPMS/openssh-3.3p1-1U70_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/openssh-3.3p1-1U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/openssh-askpass-3.3p1-1U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/openssh-askpass-gnome-3.3p1-1U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/openssh-clients-3.3p1-1U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/openssh-server-3.3p1-1U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/SRPMS/openssh-3.3p1-1U8_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/openssh-3.3p1-1U8_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/openssh-askpass-3.3p1-1U8_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/openssh-askpass-gnome-3.3p1-1U8_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/openssh-clients-3.3p1-1U8_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/openssh-server-3.3p1-1U8_1cl.i386.rpm
ADDITIONAL INSTRUCTIONS
Users of Conectiva Linux version 6.0 or higher may use apt to perform
upgrades of RPM packages:
- add the following line to /etc/apt/sources.list if it is not there yet
(you may also use linuxconf to do this):
rpm [cncbr] ftp://atualizacoes.conectiva.com.br 6.0/conectiva updates
(replace 6.0 with the correct version number if you are not running CL6.0)
- run: apt-get update
- after that, execute: apt-get upgrade
Detailed instructions reagarding the use of apt and upgrade examples
can be found at http://distro.conectiva.com.br/atualizacoes/#apt?idioma=en
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All packages are signed with Conectiva's GPG key. The key and instructions
on how to import it can be found at
http://distro.conectiva.com.br/seguranca/chave/?idioma=en
Instructions on how to check the signatures of the RPM packages can be
found at http://distro.conectiva.com.br/seguranca/politica/?idioma=en
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All our advisories and generic update instructions can be viewed at
http://distro.conectiva.com.br/atualizacoes/?idioma=en
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This archive was generated by hypermail 2b30 : Wed Jun 26 2002 - 18:15:16 PDT