openstack-keystone: denial of service

A vulnerability in how Keystone handles extremely long passwords was discovered. When Keystone is validating a password, glibc allocated space on the stack for the entire password. If the password is long enough, stack space can be exhausted which will lead to a crash. A remote attacker could use this to cause a crash in Keystone by submitting a long password when attempting to log into an existing account; an attacker must know an existing account name to attempt the login with for this attack to be successful.