openssl: crash caused by a missing krb5_sname_to_principal() return value check

The ksslkeytabisavailable function in ssl/kssl.c in OpenSSL before 0.9.8n, when Kerberos is enabled but Kerberos configuration files cannot be opened, does not check a certain return value, which allows remote attackers to cause a denial of service NULL pointer dereference and daemon crash via SS...