This is based on a patch and report by Masashi Honma
<honma@ictec.co.jp>. The issue is more generic than just TNC, though,
since failure to initialize any phase 2 EAP method can result in NULL
dereference.
It is possible that the initialization of the Phase 2 EAP method fails and
if that happens, we need to stop EAP-TTLS server from trying to continue
using the uninitialized EAP method. Otherwise, the server could trigger
a segmentation fault when dereferencing a NULL pointer.
Move the basic processing of received frames into eap_tls_common.c and use
callback functions to handle EAP type specific processing of the version
field and payload.
Fragmentation is now done as a separate step to clean up the design and to
allow the same code to be used in both Phase 1 and Phase 2. This adds
support for fragmenting EAP-PEAP/TTLS/FAST Phase 2 (tunneled) data.
Even though we try to disable TLS compression, it is possible that this
cannot be done with all TLS libraries. For example, OpenSSL 0.9.8 does not
seem to have a configuration item for disabling all compression (0.9.9 has
such an option). If compression is used, Phase 2 decryption may end up
producing more data than the input buffer due to compressed data. This
shows up especially with EAP-TNC that uses very compressible data format.
As a workaround, increase the decryption buffer length to (orig_len+500)*3.
This is a hack, but at least it handles most cases. TLS compression should
really be disabled for EAP use of TLS, but since this can show up with
common setups, it is better to handle this case.
