To prevent the creation of the CHILD_SA we set a condition on the
IKE_SA. We also schedule a delete job in case the client does not
terminate the IKE_SA (which is a SHOULD in RFC 5685).
Previously the constraints in the authentication configuration of an
initiator were enforced only after all authentication rounds were
complete. This posed a problem if an initiator used EAP or PSK
authentication while the responder was authenticated with a certificate
and if a rogue server was able to authenticate itself with a valid
certificate issued by any CA the initiator trusted.
Because any constraints for the responder's identity (rightid) or other
aspects of the authentication (e.g. rightca) the initiator had were not
enforced until the initiator itself finished its authentication such a rogue
responder was able to acquire usernames and password hashes from the client.
And if a client supported EAP-GTC it was even possible to trick it into
sending plaintext passwords.
This patch enforces the configured constraints right after the responder's
authentication successfully finished for each round and before the initiator
starts with its own authentication.
Fixes CVE-2015-4171.
According to RFC 5996, we MAY send an INFORMATIONAL message having an
AUTHENTICATION_FAILED. We don't do any retransmits, though, but just close
the IKE_SA after one message has been sent, avoiding the danger that an
unauthenticated IKE_SA stays alive.
If it is set on an auth config IDr will not be sent, and later the configured
identity will not only be checked against the returned IDr, but also
against other identities contained in the responder's certificate.
With uniqueids=no the daemon still deletes any existing IKE_SA with the
same peer if an INITIAL_CONTACT notify is received. With this new option
it also ignores these notifies.
Tobias Brunner