USN-612-9: openssl-blacklist update
12 June 2008
openssl-blacklist update
Releases
Packages
Details
USN-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 blocklists. RSA-512
blocklists 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.
Original advisory details:
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.
Update instructions
The problem can be corrected by updating your system to the following package versions:
Ubuntu 8.04
Ubuntu 7.10
Ubuntu 7.04
Ubuntu 6.06
In general, a standard system upgrade is sufficient to effect the
necessary changes.