Problem - Kevin Tafuro

see the confirmation request and the unique identifier that it contains. Unfortunately,
this is a much more difficult problem to solve, and it is one that cannot be
easily solved in software, so we will not give it any further consideration.
To implement such a scheme, the mailing list software must maintain some state
information. In particular, upon receipt of a request for membership, the software
needs to generate the unique identifier to include in the confirmation requests, and it
must store that identifier along with the email address for which membership has
been requested. In addition, it is a good idea to maintain some kind of a timestamp
so that confirmation requests will eventually expire. Expiring confirmation requests
significantly reduces the likelihood that Alice can guess the unique identifier; more
importantly, it also helps to reduce the amount of information that must be remembered
to be able to confirm requests.
We define two functions in this recipe that provide the basic implementation for the
confirmation request scheme we have just described. The first, spc_confirmation_
create( ), creates a new confirmation request by generating a unique identifier and
storing it with the email address for which confirmation is to be requested. It stores
the confirmation request information in an in-memory list of pending confirmations,
implemented simply as a dynamically allocated array. For use in a production environment,
a hash table or binary tree might be a better solution for an in-memory
data structure. Alternatively, the information could be stored in a database.
The function spc_confirmation_create( ) (SpcConfirmationCreate() on Windows)
will return 0 if some kind of error occurs. Possible errors include memory allocation
failures and attempts to add an address to the list of pending confirmations that
already exists in the list. If the operation is successful, the return value will be 1. Two
arguments are required by spc_confirmation_create( ):
address
Email address that is to be confirmed.
id
Pointer to a buffer that will be allocated by spc_confirmation_create( ). If the
function returns successfully, the buffer will contain the unique identifier to send
as part of the confirmation request email. It is the responsibility of the caller to
free the buffer using free( ) on Unix or LocalFree( ) on Windows.
You may adjust the SPC_CONFIRMATION_EXPIRE macro from the default presented here.
It controls how long pending confirmation requests will be honored and is specified
in seconds.
Note that the code we are presenting here does not send or receive email at all. Programmatically
sending and receiving email is outside the scope of this book.
#include
#include
#include
Confirming Requests via Email | 449
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