Problem - Kevin Tafuro

extra
Additional application-specific information the client passed to the server. You
can use this for whatever purpose you want. For example, you could use this
field to encode the server name the client thinks it’s connecting to, in order to
implement virtual servers.
elen
Length of the application-specific data.
If the user does not exist, you must return 0 from this callback.
The other callback allows you to log errors when a key exchange fails. You do not
have to define this callback. If you do define it, the signature is the same as in the
previous callback, except that it takes an extra parameter of type size_t that encodes
the error, and it does not return anything. As of this writing, there are only two error
conditions that might get reported:
AX_SOCK_ERR
Indicates that a generic socket error occurred. You can use your platform’s standard
API to retrieve more specific information.
AX_CAUTH_ERR
Indicates that the server was unable to authenticate the client.
The first error can represent a large number of failures. In most cases, the connection
will close unexpectedly, which can indicate many things, including loss of connectivity
or even the client’s failing to authenticate the server.
To initialize a server, we use the following function:
AX_SRV *AX_srv_listen(char *if, unsigned short port, size_t protocol,
AX_get_creds_cb cf, AX_exchange_status_cb sf);
This function has the following arguments:
if
String indicating the interface on which to bind. If you want to bind on all interfaces
a machine has, use “0.0.0.0”.
port
Port on which to bind.
protocol
Indication of which protocol you’re using. As of this writing, the only valid values
are SAX_PROTOCOL_v1 and PAX_PROTOCOL_v1.
cf
callback for retrieving credentials discussed above.
sf
Callback for error reporting discussed above. Set this to NULL if you don’t need it.
Performing Password-Based Authentication and Key Exchange | 425
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