This fixes an interoperability issue with Windows Server 2012 R2 gateways.
They insist on using modp1024 for IKE, however, Microsoft's IKEv2
implementation seems only to consider the first 15 DH groups in the proposal.
Depending on the loaded plugins modp1024 is now at position 17 or even
later, causing the server to reject the proposal. By removing some of
the weaker and rarely used DH groups from the default proposal we make
sure modp1024 is among the first 15 DH groups. The removed groups may
still be used by configuring custom proposals.
The default ESP cipher suite is now
AES_CBC-128/HMAC_SHA2_256_128
and requires SHA-2 HMAC support in the Linux kernel (correctly implemented
since 2.6.33).
The default IKE cipher suite is now
AES_CBC-128/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_256
if the openssl plugin is loaded or
AES_CBC-128/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_3072
if ECC is not available.
The use of the SHA-1 hash algorithm and the MODP_2048 DH group has been
deprecated and ENCR_CHACHA20_POLY1305 has been added to the default
IKE AEAD algorithms.
According to RFC 5996 3.3 we should use a separate proposal for AEAD algorithms.
This was not clear in RFC 5282, hence we previously included both AEAD and
non-AEAD algorithms in a single proposal.
The DH transform is optional for ESP/AH proposals. The initiator can
include NONE (0) in its proposal to indicate that while it prefers to
do a DH exchange, the responder may still decide to not do so.
Fixes#532.
Beside that it makes the code actually simpler, it reduces the number of lists
stored by each IKE_SA and each CHILD_SA by 4, which can be up to 1KB per SA.
Tobias Brunner