Ubuntu 6.06 LTS / 7.04 / 7.10 / 8.04 LTS : openssl-blacklist update (USN-612-9)
High Nessus Plugin ID 33198
SynopsisThe remote Ubuntu host is missing one or more security-related patches.
DescriptionUSN-612-3 addressed a weakness in OpenSSL certificate and key generation in OpenVPN by introducing openssl-blacklist to aid in detecting vulnerable private keys. This update enhances the openssl-vulnkey tool to check Certificate Signing Requests, accept input from STDIN, and check moduli without a certificate.
It was also discovered that additional moduli are vulnerable if generated with OpenSSL 0.9.8g or higher. While it is believed that there are few of these vulnerable moduli in use, this update includes updated RSA-1024 and RSA-2048 blacklists. RSA-512 blacklists are also included in the new openssl-blacklist-extra package.
You can check for weak SSL/TLS certificates by installing openssl-blacklist via your package manager, and using the openssl-vulnkey command.
$ openssl-vulnkey /path/to/certificate_or_key $ cat /path/to/certificate_or_key | openssl-vulnkey -
You can also check if a modulus is vulnerable by specifying the modulus and number of bits.
$ openssl-vulnkey -b bits -m modulus
These commands can be used on public certificates, requests, and private keys for any X.509 certificate, CSR, or RSA key, including ones for web servers, mail servers, OpenVPN, and others. If in doubt, destroy the certificate and key and generate new ones. Please consult the documentation for your software when recreating SSL/TLS certificates. Also, if certificates have been generated for use on other systems, they must be found and replaced as well.
A weakness has been discovered in the random number generator used by OpenSSL on Debian and Ubuntu systems. As a result of this weakness, certain encryption keys are much more common than they should be, such that an attacker could guess the key through a brute-force attack given minimal knowledge of the system. This particularly affects the use of encryption keys in OpenSSH, OpenVPN and SSL certificates.
Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
SolutionUpdate the affected openssl-blacklist and / or openssl-blacklist-extra packages.