sasl_handle_login(struct sasl_session *const restrict p, struct user *const u, struct myuser *mu)
{
	bool was_killed = false;

	// Find the account if necessary
	if (! mu)
	{
		if (! *p->pendingeid)
		{
			(void) slog(LG_INFO, "%s: session for '%s' without an pendingeid (BUG)",
			                     MOWGLI_FUNC_NAME, u->nick);
			(void) notice(saslsvs->nick, u->nick, LOGIN_CANCELLED_STR);
			return false;
		}

		if (! (mu = myuser_find_uid(p->pendingeid)))
		{
			if (*p->authzid)
				(void) notice(saslsvs->nick, u->nick, "Account %s dropped; login cancelled",
				                                      p->authzid);
			else
				(void) notice(saslsvs->nick, u->nick, "Account dropped; login cancelled");

			return false;
		}
	}

	// If the user is already logged in, and not to the same account, log them out first
	if (u->myuser && u->myuser != mu)
	{
		if (is_soper(u->myuser))
			(void) logcommand_user(saslsvs, u, CMDLOG_ADMIN, "DESOPER: \2%s\2 as \2%s\2",
			                                                 u->nick, entity(u->myuser)->name);

		(void) logcommand_user(saslsvs, u, CMDLOG_LOGIN, "LOGOUT");

		if (! (was_killed = ircd_on_logout(u, entity(u->myuser)->name)))
		{
			mowgli_node_t *n;

			MOWGLI_ITER_FOREACH(n, u->myuser->logins.head)
			{
				if (n->data == u)
				{
					(void) mowgli_node_delete(n, &u->myuser->logins);
					(void) mowgli_node_free(n);
					break;
				}
			}

			u->myuser = NULL;
		}
	}

	// If they were not killed above, log them in now
	if (! was_killed)
	{
		if (u->myuser != mu)
		{
			// If they're not logged in, or logging in to a different account, do a full login
			(void) myuser_login(saslsvs, u, mu, false);
			(void) logcommand_user(saslsvs, u, CMDLOG_LOGIN, "LOGIN (%s)", p->mechptr->name);
		}
		else
		{
			// Otherwise, just update login time ...
			mu->lastlogin = CURRTIME;
			(void) logcommand_user(saslsvs, u, CMDLOG_LOGIN, "REAUTHENTICATE (%s)", p->mechptr->name);
		}
	}

	return true;
}
When an actor claims to have a given identity, the software does not prove or insufficiently proves that the claim is correct.