![]() ![]() You can also test to see if keys are vulnerable using the utility as described below. ![]() Instructions for how to regenerate the keys for these applications are below. Then, regenerate and distribute any potentially vulnerable keys. If you choose not to use the above aptitude command, note that all of the following packages must be upgraded (they all come from the same source package): You probably want to also pick up the new openssh packages that include the blacklist of known weak keys, but you will need to aptitude dist-upgrade for that in order to install the new openssh-blacklist package. To fix this, first aptitude update & aptitude upgrade to install the new version of the openssl and libssl0.9.8 packages (the vulnerability is fixed in version 0.9.8c-4etch3 for etch and version 0.9.8g-9 for lenny/sid). telnetd-ssl SSL certificates for SSL-Telnet.apache2 (ssl certs, see "PEM keys" bellow).postfix, exim4, sendmail and other MTAs when using SSL/TLS.Many lists of 'weak' keys have been generated by the metasploit project: Īpplications/protocols known to use these keys: This page uses the data from openssl-blacklist. There is a web-based check available at which will identify a CSR with a weak key. This is due to an 'attack' on DSA that allows the secret key to be found if the nonce used in the signature is known or reused.īlacklists of vulnerable keys available in unstable: Simply using a 'strong' DSA key (i.e., generated with a 'good' OpenSSL) to make a connection from such a machine may have compromised it. In addition, any DSA key must be considered compromised if it has been used on a machine with a 'bad' OpenSSL. Generated using 'openssl', 'ssh-keygen', or 'openvpn -keygen' (GnuPG and GNUTLS are not affected).Generated with Etch, Lenny or Sid (Sarge is not vulnerable).The following cryptographic tools are unaffected:Ĭryptsetup (neither LUKS nor the regular dm-crypt use openssl, the openssl keyscript - which is not used in any default installations - does use openssl, but only to encrypt the key, not to actually generate the key that is used to encrypt the partition, the encryption of the key may therefore be less strong than expected but the key itself is not)Ĭharacteristics of potentially vulnerable keys: Note that this last point means that passwords transmitted over ssh to a server with a weak dsa server key could be compromised too see the Debian project's reaction to this. all key types that were generated using openssl (this includes RSA and DSA keys)Ĭompromise of other keys or passwords that were transmitted over an encrypted link that was set up using weak keys.weak keys for both clients and servers (see section "Identifying Weak Keys below").web server certificates) potentially vulnerable. In Debian Security Advisory 1571, also known as CVE-2008-0166 (New openssl packages fix predictable random number generator), the Debian Security Team disclosed a vulnerability in the openssl package that makes many cryptographic keys that are used for authentication (e.g. Please consider things such as the physical location of the machine, etc, before completely disabling sshd. It seems you've deviated from default and without more details it's hard to know exactly what's going on.ĭepending on the requirements, removing the package providing sshd ( openssh-server) would be a more fool-proof approach. $ sudo systemctl stop rvice sshd.socketĪs it has been mentioned, Ubuntu's openssh-server only installs ssh.service, and no socket. One is dependent on the other and will not be disabled unless done in the proper order. You need to stop and disable both of these using systemctl, likely the socket first, and then the service. You can see that with your systemctl command, you have rvice and sshd.socket. No new connections should be able to become established. If I'm not mistaken, any existing ssh connections will be maintained even after running systemctl stop sshd. You can use systemctl disable sshd so that sshd will not be started when you turn the system on in the future. You can stop a service with systemctl, but you need to also disable it and anything that would cause it to start up. ![]()
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