/* authd/provider.c - authentication provider framework
 * Copyright (c) 2016 Elizabeth Myers <elizabeth@interlinked.me>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/* The basic design here is to have "authentication providers" that do things
 * like query ident and blacklists and even open proxies.
 *
 * Providers are registered in the auth_providers linked list. It is planned to
 * use a bitmap to store provider ID's later.
 *
 * Providers can either return failure immediately, immediate acceptance, or do
 * work in the background (calling set_provider to signal this).
 *
 * Provider-specific data for each client can be kept in an index of the data
 * struct member (using the provider's ID).
 *
 * All providers must implement at a minimum a perform_provider function. You
 * don't have to implement the others if you don't need them.
 *
 * Providers may kick clients off by rejecting them. Upon rejection, all
 * providers are cancelled. They can also unconditionally accept them.
 *
 * When a provider is done and is neutral on accepting/rejecting a client, it
 * should call provider_done. Do NOT call this if you have accepted or rejected
 * the client.
 *
 * Eventually, stuff like *:line handling will be moved here, but that means we
 * have to talk to bandb directly first.
 *
 * --Elizafox, 9 March 2016
 */

#include "rb_dictionary.h"
#include "authd.h"
#include "provider.h"

rb_dlink_list auth_providers;

/* Clients waiting */
rb_dictionary *auth_clients;

/* Load a provider */
void load_provider(struct auth_provider *provider)
{
	if(rb_dlink_list_length(&auth_providers) >= MAX_PROVIDERS)
	{
		warn_opers(L_CRIT, "Exceeded maximum level of authd providers (%d max)", MAX_PROVIDERS);
		return;
	}

	provider->init();
	rb_dlinkAdd(provider, &provider->node, &auth_providers);
}

void unload_provider(struct auth_provider *provider)
{
	provider->destroy();
	rb_dlinkDelete(&provider->node, &auth_providers);
}

/* Initalise all providers */
void init_providers(void)
{
	auth_clients = rb_dictionary_create("pending auth clients", rb_uint32cmp);
	load_provider(&rdns_provider);
	load_provider(&ident_provider);
}

/* Terminate all providers */
void destroy_providers(void)
{
	rb_dlink_node *ptr;
	rb_dictionary_iter iter;
	struct auth_client *auth;
	struct auth_provider *provider;

	/* Cancel outstanding connections */
	RB_DICTIONARY_FOREACH(auth, &iter, auth_clients)
	{
		/* TBD - is this the right thing? */
		reject_client(auth, 0, "Authentication system is down... try reconnecting in a few seconds");
	}

	RB_DLINK_FOREACH(ptr, auth_providers.head)
	{
		provider = ptr->data;

		if(provider->destroy)
			provider->destroy();
	}
}

/* Cancel outstanding providers for a client */
void cancel_providers(struct auth_client *auth)
{
	rb_dlink_node *ptr;
	struct auth_provider *provider;

	RB_DLINK_FOREACH(ptr, auth_providers.head)
	{
		provider = ptr->data;

		if(provider->cancel && is_provider_on(auth, provider->id))
			/* Cancel if required */
			provider->cancel(auth);
	}

	rb_dictionary_delete(auth_clients, RB_UINT_TO_POINTER(auth->cid));
	rb_free(auth);
}

/* Provider is done */
void provider_done(struct auth_client *auth, provider_t id)
{
	rb_dlink_node *ptr;
	struct auth_provider *provider;

	set_provider_off(auth, id);
	set_provider_done(auth, id);

	if(!auth->providers)
	{
		/* No more providers, done */
		accept_client(auth, 0);
		return;
	}

	RB_DLINK_FOREACH(ptr, auth_providers.head)
	{
		provider = ptr->data;

		if(provider->completed && is_provider_on(auth, provider->id))
			/* Notify pending clients who asked for it */
			provider->completed(auth, id);
	}
}

/* Reject a client */
void reject_client(struct auth_client *auth, provider_t id, const char *reason)
{
	char reject;

	switch(id)
	{
	case PROVIDER_RDNS:
		reject = 'D';
		break;
	case PROVIDER_IDENT:
		reject = 'I';
		break;
	case PROVIDER_BLACKLIST:
		reject = 'B';
		break;
	default:
		reject = 'N';
		break;
	}

	/* We send back username and hostname in case ircd wants to overrule our decision.
	 * In the future this may not be the case.
	 * --Elizafox
	 */
	rb_helper_write(authd_helper, "R %x %c %s %s :%s", auth->cid, reject, auth->username, auth->hostname, reason);

	set_provider_off(auth, id);
	cancel_providers(auth);
}

/* Accept a client, cancel outstanding providers if any */
void accept_client(struct auth_client *auth, provider_t id)
{
	uint32_t cid = auth->cid;

	rb_helper_write(authd_helper, "A %x %s %s", auth->cid, auth->username, auth->hostname);

	set_provider_off(auth, id);
	cancel_providers(auth);
}

/* Send a notice to a client */
void notice_client(struct auth_client *auth, const char *fmt, ...)
{
	char buf[BUFSIZE];
	va_list args;

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);

	rb_helper_write(authd_helper, "N %x :%s", auth->cid, buf);
}

/* Send a warning to the IRC daemon for logging, etc. */
void warn_opers(notice_level_t level, const char *fmt, ...)
{
	char buf[BUFSIZE];
	va_list args;

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);

	rb_helper_write(authd_helper, "W %c :%s", level, buf);
}

/* Begin authenticating user */
static void start_auth(const char *cid, const char *l_ip, const char *l_port, const char *c_ip, const char *c_port)
{
	struct auth_provider *provider;
	struct auth_client *auth = rb_malloc(sizeof(struct auth_client));
	long lcid = strtol(cid, NULL, 16);
	rb_dlink_node *ptr;

	if(lcid >= UINT32_MAX)
		return;

	auth->cid = (uint32_t)lcid;

	rb_strlcpy(auth->l_ip, l_ip, sizeof(auth->l_ip));
	auth->l_port = (uint16_t)atoi(l_port);	/* should be safe */
	(void) rb_inet_pton_sock(l_ip, (struct sockaddr *)&auth->l_addr);

	rb_strlcpy(auth->c_ip, c_ip, sizeof(auth->c_ip));
	auth->c_port = (uint16_t)atoi(c_port);
	(void) rb_inet_pton_sock(c_ip, (struct sockaddr *)&auth->c_addr);

#ifdef RB_IPV6
	if(GET_SS_FAMILY(&auth->l_addr) == AF_INET6)
		((struct sockaddr_in6 *)&auth->l_addr)->sin6_port = htons(auth->l_port);
	else
#endif
		((struct sockaddr_in *)&auth->l_addr)->sin_port = htons(auth->l_port);

#ifdef RB_IPV6
	if(GET_SS_FAMILY(&auth->c_addr) == AF_INET6)
		((struct sockaddr_in6 *)&auth->c_addr)->sin6_port = htons(auth->c_port);
	else
#endif
		((struct sockaddr_in *)&auth->c_addr)->sin_port = htons(auth->c_port);

	rb_dictionary_add(auth_clients, RB_UINT_TO_POINTER(auth->cid), auth);

	RB_DLINK_FOREACH(ptr, auth_providers.head)
	{
		provider = ptr->data;

		/* Execute providers */
		if(!provider->start(auth))
		{
			/* Rejected immediately */
			cancel_providers(auth);
			return;
		}
	}

	/* If no providers are running, accept the client */
	if(!auth->providers)
		accept_client(auth, 0);
}

/* Callback for the initiation */
void handle_new_connection(int parc, char *parv[])
{
	if(parc < 7)
	{
		warn_opers(L_CRIT, "BUG: received too few params for new connection (7 expected, got %d)", parc);
		return;
	}

	start_auth(parv[1], parv[2], parv[3], parv[4], parv[5]);
}