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Implement a new authentication method allowing aucat and midicat to
work over TCP, for instance, to expose the sound card of one machine
with other machines of the network.

The first client generates a 128-bit random number (aka the
session cookie), saves it in $HOME/.aucat_cookie and sends it to the
server. Successive clients load the cookie from $HOME/.aucat_cookie
and send it to the server but the server accepts only clients whose
cookie matches the session cookie. When all clients are gone, the
session is over, and another cookie could start a new session, and so
on.

TCP is enabled on the server with the new -L option, and on the client
side hostnames are specified with a new optional component in the
device name.

hints from damien, dlg and deraadt, tweaks from jmc

/*	$OpenBSD: listen.c,v 1.14 2011/04/28 06:19:57 ratchov Exp $	*/
/*
 * Copyright (c) 2008 Alexandre Ratchov <alex@caoua.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/signal.h>
#include <sys/stat.h>
#include <sys/un.h>

#include <netinet/in.h>
#include <netdb.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "conf.h"
#include "listen.h"
#include "sock.h"

struct fileops listen_ops = {
	"listen",
	sizeof(struct listen),
	listen_close,
	NULL, /* read */
	NULL, /* write */
	NULL, /* start */
	NULL, /* stop */
	listen_nfds,
	listen_pollfd,
	listen_revents
};

void
listen_new_un(char *path)
{
	int sock, oldumask;
	struct sockaddr_un sockname;
	struct listen *f;

	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock < 0) {
		perror("socket");
		exit(1);
	}
	if (unlink(path) < 0 && errno != ENOENT) {
		perror("unlink");
		goto bad_close;
	}
	sockname.sun_family = AF_UNIX;
	strlcpy(sockname.sun_path, path, sizeof(sockname.sun_path));
	oldumask = umask(0111);
	if (bind(sock, (struct sockaddr *)&sockname,
		sizeof(struct sockaddr_un)) < 0) {
		perror("bind");
		goto bad_close;
	}
	umask(oldumask);
	if (listen(sock, 1) < 0) {
		perror("listen");
		goto bad_close;
	}
	f = (struct listen *)file_new(&listen_ops, path, 1);
	if (f == NULL)
		goto bad_close;
	f->path = strdup(path);
	if (f->path == NULL) {
		perror("strdup");
		exit(1);
	}
	f->fd = sock;
	return;
 bad_close:
	close(sock);
	exit(1);	
}

void
listen_new_tcp(char *addr, unsigned port)
{
	char *host, serv[sizeof(unsigned) * 3 + 1];
	struct addrinfo *ailist, *ai, aihints;
	struct listen *f;
	int s, error, opt = 1, n = 0;
	
	/* 
	 * obtain a list of possible addresses for the host/port 
	 */
	memset(&aihints, 0, sizeof(struct addrinfo));
	snprintf(serv, sizeof(serv), "%u", port);
	host = strcmp(addr, "*") == 0 ? NULL : addr;
	aihints.ai_flags |= AI_PASSIVE;
	aihints.ai_socktype = SOCK_STREAM;
	aihints.ai_protocol = IPPROTO_TCP;
	error = getaddrinfo(host, serv, &aihints, &ailist);
	if (error) {
		fprintf(stderr, "%s: %s\n", addr, gai_strerror(error));
		exit(1);
	}

	/* 
	 * for each address, try create a listening socket bound on
	 * that address
	 */
	for (ai = ailist; ai != NULL; ai = ai->ai_next) {
		s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
		if (s < 0) {
			perror("socket");
			continue;
		}
		opt = 1;
		if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(int)) < 0) {
			perror("setsockopt");
			goto bad_close;
		}
		if (bind(s, ai->ai_addr, ai->ai_addrlen) < 0) {
			perror("bind");
			goto bad_close;
		}
		if (listen(s, 1) < 0) {
			perror("listen");
			goto bad_close;
		}
		f = (struct listen *)file_new(&listen_ops, addr, 1);
		if (f == NULL) {
		bad_close:
			close(s);
			continue;
		}
		f->path = NULL;
		f->fd = s;
		n++;
	}
	freeaddrinfo(ailist);
	if (n == 0)
		exit(1);
}

int
listen_nfds(struct file *f) {
	return 1;
}

int
listen_pollfd(struct file *file, struct pollfd *pfd, int events)
{
	struct listen *f = (struct listen *)file;

	pfd->fd = f->fd;
	pfd->events = POLLIN;
	return 1;
}

int
listen_revents(struct file *file, struct pollfd *pfd)
{
	struct listen *f = (struct listen *)file;
	struct sockaddr caddr;
	socklen_t caddrlen;
	int sock;

	if (pfd->revents & POLLIN) {
		caddrlen = sizeof(caddrlen);
		sock = accept(f->fd, &caddr, &caddrlen);
		if (sock < 0) {
			/* XXX: should we kill the socket here ? */
			perror("accept");
			return 0;
		}
		if (fcntl(sock, F_SETFL, O_NONBLOCK) < 0) {
			perror("fcntl(sock, O_NONBLOCK)");
			close(sock);
			return 0;
		}
		if (sock_new(&sock_ops, sock) == NULL) {
			close(sock);
			return 0;
		}
	}
	return 0;
}

void
listen_close(struct file *file)
{
	struct listen *f = (struct listen *)file;

	if (f->path != NULL) {
		unlink(f->path);
		free(f->path);
	}
	close(f->fd);
}

void
listen_closeall(void)
{
	struct file *f, *fnext;

	for (f = LIST_FIRST(&file_list); f != NULL; f = fnext) {
		fnext = LIST_NEXT(f, entry);
		if (f->ops == &listen_ops)
			file_close(f);
	}
}