Neue openssl Pakete beheben potentielle Sicherheitslücke

[armin]

Jeder der in den letzten 18 Monaten einen DSA -Schlüssel mit openssl aus Debian erzeugt hat sollte dringend dieses Announcement lesen und wenn nötig seine Schlüssel aktualisieren: http://lists.debian.org/debian-security ... 00152.html

[ruwen]

Leider ist die Hilfeseite noch offline. Ich hoffe die kommt bald, weil ich habe ehrlich gesagt keinen Plan wie ich meine Keys neu generiere.

[hermannstux]

Suchst du sowas? http://www.huschi.net/14_141_de.html

Weasel hat vorhin ne Mail geschickt, das man alle Debian-Entwickler Accounts gesperrt hat, damit die Keys neu generiert werden.

[ruwen]

Hm... dann habe ich das ganze wohl etwas falsch verstanden. Ich nutze für SSH Benutzername und Passwort. Mein VPN ist zur Zeit aus, da kann ich in Ruhe warten. Ansonsten sind also nur Sachen betroffen, wo man sich via Key anmeldet?

[armin]

Ssh-Host-Keys sind zum Beispiel auch betroffen.

[novalix]

Hi,
die ersten Links und Workarounds trudeln langsam ein.
Unter http://blog.zakame.net/news/openssl-remote-dsa-1571 gibt es schon mal ein Mini-Tut zu den Host-Keys und einen link zu nem checker.
Da kommt noch einiges an Arbeit auf uns zu (vor allen Dingen den windowsnutzenden Kunden erklären, warum sie jetzt ein neues Sicherheitszertifikat importieren müssen und wie das geht und dass das nicht ihren Computer und auch nicht das Internet kaputt macht und ...).

Groetjes, niels

[armin]

Ssh-Host-Keys sind zum Beispiel auch betroffen.

Apropos:

Code: Alles auswählen

$ ./dowkd.pl host debianforum.de
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9
debianforum.de: weak key
debianforum.de: weak key


[Donnie-Darko]

http://www.debian.org/security/key-roll ... ex.de.html

[feltel]

Ssh-Host-Keys sind zum Beispiel auch betroffen.

Apropos:

Code: Alles auswählen

$ ./dowkd.pl host debianforum.de
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9
debianforum.de: weak key
debianforum.de: weak key


Jetzt nicht mehr:

Code: Alles auswählen

leela:~# perl dowkd.pl host debianforum.de
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9
# debianforum.de SSH-2.0-OpenSSH_4.3p2 Debian-9


[Profbunny]

hat jemand den patch für dowkd.pl als file für mich, irgendwie hauts das alles durcheinander wenn ich den von der seite kopiere.

[catdog2]

Code: Alles auswählen

- ------------------------------------------------------------------------
Debian Security Advisory DSA-1576-1                  security@debian.org
http://www.debian.org/security/                           Florian Weimer
May 14, 2008                          http://www.debian.org/security/faq
- ------------------------------------------------------------------------

Package        : openssh
Vulnerability  : predictable random number generator
Problem type   : remote
Debian-specific: yes
CVE Id(s)      : CVE-2008-0166

The recently announced vulnerability in Debian's openssl package
(DSA-1571-1, CVE-2008-0166) indirectly affects OpenSSH.  As a result,
all user and host keys generated using broken versions of the openssl
package must be considered untrustworthy, even after the openssl update
has been applied.

1. Install the security updates

   This update contains a dependency on the openssl update and will
   automatically install a corrected version of the libss0.9.8 package,
   and a new package openssh-blacklist.

   Once the update is applied, weak user keys will be automatically
   rejected where possible (though they cannot be detected in all
   cases).  If you are using such keys for user authentication, they
   will immediately stop working and will need to be replaced (see
   step 3).

   OpenSSH host keys can be automatically regenerated when the OpenSSH
   security update is applied.  The update will prompt for confirmation
   before taking this step.

2. Update OpenSSH known_hosts files

   The regeneration of host keys will cause a warning to be displayed when
   connecting to the system using SSH until the host key is updated in the
   known_hosts file.  The warning will look like this:

   @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
   @    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
   @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
   IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
   Someone could be eavesdropping on you right now (man-in-the-middle attack)!
   It is also possible that the RSA host key has just been changed.

   In this case, the host key has simply been changed, and you should update
   the relevant known_hosts file as indicated in the error message.
   
   It is recommended that you use a trustworthy channel to exchange the
   server key.  It is found in the file /etc/ssh/ssh_host_rsa_key.pub on
   the server; it's fingerprint can be printed using the command:

      ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key.pub

   In addition to user-specific known_hosts files, there may be a
   system-wide known hosts file /etc/ssh/known_hosts.  This is file is
   used both by the ssh client and by sshd for the hosts.equiv
   functionality.  This file needs to be updated as well.

3. Check all OpenSSH user keys

   The safest course of action is to regenerate all OpenSSH user keys,
   except where it can be established to a high degree of certainty that the
   key was generated on an unaffected system.

   Check whether your key is affected by running the ssh-vulnkey tool, included
   in the security update.  By default, ssh-vulnkey will check the standard
   location for user keys (~/.ssh/id_rsa, ~/.ssh/id_dsa and ~/.ssh/identity),
   your authorized_keys file (~/.ssh/authorized_keys and
   ~/.ssh/authorized_keys2), and the system's host keys
   (/etc/ssh/ssh_host_dsa_key and /etc/ssh/ssh_host_rsa_key).

   To check all your own keys, assuming they are in the standard
   locations (~/.ssh/id_rsa, ~/.ssh/id_dsa, or ~/.ssh/identity):

     ssh-vulnkey

   To check all keys on your system:

     sudo ssh-vulnkey -a

   To check a key in a non-standard location:

     ssh-vulnkey /path/to/key

   If ssh-vulnkey says "Unknown (no blacklist information)", then it has no
   information about whether that key is affected.  In this case, you
   can examine the modification time (mtime) of the file using "ls -l".
   Keys generated before September 2006 are not affected.  Keep in mind
   that, although unlikely, backup procedures may have changed the file
   date back in time (or the system clock may have been incorrectly
   set).
   
   If in doubt, generate a new key and remove the old one from any
   servers.

4. Regenerate any affected user keys

   OpenSSH keys used for user authentication must be manually regenerated,
   including those which may have since been transferred to a different system
   after being generated.

   New keys can be generated using ssh-keygen, e.g.:

   $ ssh-keygen
   Generating public/private rsa key pair.
   Enter file in which to save the key (/home/user/.ssh/id_rsa):
   Enter passphrase (empty for no passphrase):
   Enter same passphrase again:
   Your identification has been saved in /home/user/.ssh/id_rsa.
   Your public key has been saved in /home/user/.ssh/id_rsa.pub.
   The key fingerprint is:
   00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 user@host

5. Update authorized_keys files (if necessary)

   Once the user keys have been regenerated, the relevant public keys
   must be propagated to any authorized_keys files (and authorized_keys2
   files, if applicable) on remote systems.  Be sure to delete the lines
   containing old keys from those files..


In addition to countermeasures to mitigate the randomness vulnerability,
this OpenSSH update fixes several other vulnerabilities:

CVE-2008-1483:
   Timo Juhani Lindfors discovered that, when using X11 forwarding, the
   SSH client selects an X11 forwarding port without ensuring that it
   can be bound on all address families. If the system is configured
   with IPv6 (even if it does not have working IPv6 connectivity), this
   could allow a local attacker on the remote server to hijack X11
   forwarding.

CVE-2007-4752:
   Jan Pechanec discovered that ssh fails back to creating a trusted X11
   cookie if creating an untrusted cookie fails, potentially exposing
   the local display to a malicious remote server when using X11
   forwarding.

For the stable distribution (etch), these problems have been fixed in
version 4.3p2-9etch1.  Currently, only a subset of all supported
architectures have been built; further updates will be provided when
they become available.

For the unstable distribution (sid) and the testing distribution
(lenny), these problems have been fixed in version 4.7p1-9.

We recommend that you upgrade your openssh packages and take the
measures indicated above.

[pluvo]

http://www.links.org/?p=327
http://www.links.org/?p=328

Beim zweiten Blog-Eintrag wird auch etwas der technische Hintergrund beleuchtet.

Ansonsten gibt hier auch noch brauchbare Informationen:
http://wiki.debian.org/SSLkeys

http://de.wikipedia.org/wiki/Valgrind

mfg pluvo

[C_A]

Um den ganzen etwas Nachdruck zu verleihen

the exploit is *trivial*
and if you have weak keys then it is only a matter of time before every
script kiddie on the planet can log into your system. It was imperative
that use of these keys be disabled as soon as possible. If that involves
a few people being inconvenienced, it's worth the trouble.

(Aus einer Antwort auf die Bemerkung/Frage wieso man ohne weiteres den Login ueber die kompromitierten Schluessel abdreht und so evt. den Admin raussperrt.)

Ich finde dieses Vorgehen durchaus gerechtfertigt und gut so.

[TRex2003]

So, neue Keys erstellt und aus allen Systemen, die meinen Key akzeptieren, den alten gelöscht (und durch den neuen ersetzt).

Eigentlich wäre bei dem Update im config-Text ne Meldung angebracht gewesen, dass nicht nur Dienst X und Y neu gestartet werden müssen...

[C_A]

Ja jetzt wird das Ganze langsam script kiddy faehig

http://metasploit.com/users/hdm/tools/debian-openssl/