strongswan - security update

Alexander E. Patrakov discovered an issue in strongSwan, an IKE/IPsec
suite used to establish IPsec protected links.

When an IKEv2 client authenticates the server with certificates and the
client authenticates itself to the server using pre-shared key or EAP,
the constraints on the server certificate are only enforced by the
client after all authentication steps are completed successfully. A
rogue server which can authenticate using a valid certificate issued by
any CA trusted by the client could trick the user into continuing the
authentication, revealing the username and password digest (for EAP) or
even the cleartext password (if EAP-GTC is accepted).

For the oldstable distribution (wheezy), this problem has been fixed
in version 4.5.2-1.5+deb7u7.

For the stable distribution (jessie), this problem has been fixed in
version 5.2.1-6+deb8u1.

For the testing distribution (stretch), this problem has been fixed
in version 5.3.1-1.

For the unstable distribution (sid), this problem has been fixed in
version 5.3.1-1.

We recommend that you upgrade your strongswan packages.