--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pop3e.c	Thu Mar 27 09:53:52 2014 +0500
@@ -0,0 +1,255 @@
+/*
+ * Copyright (c) 2014 Sunil Nimmagadda <sunil@nimmagadda.net>
+ *
+ * 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/time.h>
+#include <sys/tree.h>
+
+#include <err.h>
+#include <errno.h>
+#include <event.h>
+#include <netdb.h>
+#include <pwd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "imsgev.h"
+#include "pop3d.h"
+#include "ssl.h"
+
+#define BACKLOG		5
+
+static void auth_response(struct session *, int);
+static void pop3_accept(int, short, void *);
+static void pop3_listen(const char *);
+static void pop3_pause(int, short, void *);
+static void pop3d_imsgev(struct imsgev *, int, struct imsg *);
+static void needfd(struct imsgev *);
+static void sig_handler(int, short, void *);
+
+struct imsgev		iev_pop3d;
+void			*ssl_ctx;
+
+pid_t
+pop3_main(int pair[2], struct passwd *pw)
+{
+	extern struct session_tree	sessions;
+	struct event			ev_sigint, ev_sigterm;
+	pid_t				pid;
+
+	pid = fork();
+	if (pid < 0)
+		fatal("pop3e: fork");
+
+	if (pid > 0)
+		return (pid);
+
+	close(pair[0]);
+	setproctitle("pop3 engine");
+	SPLAY_INIT(&sessions);
+	event_init();
+	signal_set(&ev_sigint, SIGINT, sig_handler, NULL);
+	signal_set(&ev_sigterm, SIGTERM, sig_handler, NULL);
+	signal_add(&ev_sigint, NULL);
+	signal_add(&ev_sigterm, NULL);
+	imsgev_init(&iev_pop3d, pair[1], NULL, pop3d_imsgev, needfd);
+	pop3_listen("pop3");
+
+	ssl_init();
+	if ((ssl_ctx = ssl_setup()) == NULL)
+		fatal("ssl_setup failed");
+	pop3_listen("pop3s");
+
+	if (chroot(pw->pw_dir) == -1 || chdir("/") == -1)
+		fatal("chroot");
+
+	if (setgroups(1, &pw->pw_gid) ||
+	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
+	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
+		fatal("cannot drop privileges");
+
+	if (event_dispatch() < 0)
+		fatal("event_dispatch");
+
+	logit(LOG_INFO, "pop3 engine exiting");
+	_exit(0);
+}
+
+static void
+pop3_listen(const char *port)
+{
+	struct listener	*l = NULL;
+	struct addrinfo	hints, *res, *res0;
+	int		error, opt, serrno, s;
+	const char	*cause = NULL;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = PF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_flags = AI_PASSIVE;
+	error = getaddrinfo(NULL, port, &hints, &res0);
+	if (error)
+		errx(1, "%s", gai_strerror(error));
+
+	for (res = res0; res != NULL; res = res->ai_next) {
+		s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+		if (s == -1) {
+			cause = "socket";
+			continue;
+		}
+
+		opt = 1;
+		if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
+		    &opt, sizeof(opt)) == -1)
+			fatal("listener setsockopt(SO_REUSEADDR)");
+
+		if (bind(s, res->ai_addr, res->ai_addrlen) == -1) {
+			serrno = errno;
+			cause = "bind";
+			close(s);
+			errno = serrno;
+			continue;
+		}
+
+		set_nonblocking(s);
+		if (listen(s, BACKLOG) == -1)
+			fatal("listen");
+
+		l = xcalloc(1, sizeof(*l), "pop3_listen");
+		l->sock = s;
+		if (strcmp(port, "pop3s") == 0)
+			l->flags |= POP3S;
+
+		event_set(&l->ev, s, EV_READ|EV_PERSIST, pop3_accept, l);
+		event_add(&l->ev, NULL);
+		evtimer_set(&l->pause, pop3_pause, l);
+	}
+
+	if (l == NULL)
+		errx(1, "%s", cause);
+
+	freeaddrinfo(res0);
+}
+
+static void
+pop3_accept(int fd, short events, void *arg)
+{
+	struct sockaddr_storage ss;
+	struct listener		*l = arg;
+	struct timeval		timeout = {1, 0};
+	socklen_t		len;
+	int			s;
+
+	len = sizeof(ss);
+	s = accept(fd, (struct sockaddr *)&ss, &len);
+	if (s == -1) {
+		switch (errno) {
+		case EINTR:
+		case EWOULDBLOCK:
+		case ECONNABORTED:
+			return;
+		case EMFILE:
+		case ENFILE:
+			event_del(&l->ev);
+			evtimer_add(&l->pause, &timeout);
+			return;
+		default:
+			fatalx("accept");
+		}
+	}
+
+	set_nonblocking(s);
+	l->ss = ss;
+	session_init(l, s);
+}
+
+static void
+pop3_pause(int fd, short events, void *arg)
+{
+	struct listener *l = arg;
+
+	event_add(&l->ev, NULL);
+}
+
+static void
+pop3d_imsgev(struct imsgev *iev, int code, struct imsg *imsg)
+{
+	extern struct session_tree	sessions;
+	struct session			key, *r;
+
+	switch (code) {
+	case IMSGEV_IMSG:
+		key.id = imsg->hdr.peerid;
+		r = SPLAY_FIND(session_tree, &sessions, &key);
+		if (r == NULL) {
+			logit(LOG_INFO, "%u: session not found", key.id);
+			fatalx("pop3e: session lost");
+		}
+		switch (imsg->hdr.type) {
+		case IMSG_AUTH:
+			auth_response(r, imsg->fd);
+			break;
+		default:
+			logit(LOG_DEBUG, "%s: unexpected imsg %d",
+			    __func__, imsg->hdr.type);
+			break;
+		}
+		break;
+	case IMSGEV_EREAD:
+	case IMSGEV_EWRITE:
+	case IMSGEV_EIMSG:
+		fatal("pop3e: imsgev read/write error");
+		break;
+	case IMSGEV_DONE:
+		event_loopexit(NULL);
+		break;
+	}
+}
+
+static void
+auth_response(struct session *s, int fd)
+{
+	if (fd == -1) {
+		session_reply(s, "%s", "-ERR auth failed");
+		io_set_write(&s->io);
+		session_close(s, 1);
+		return;
+	}
+
+	session_imsgev_init(s, fd);
+}
+
+static void
+needfd(struct imsgev *iev)
+{
+	/* XXX can anything be done to handle fd exhaustion? */
+	fatalx("pop3e needs an fd");
+}
+
+static void
+sig_handler(int sig, short event, void *arg)
+{
+	switch (sig) {
+	case SIGINT:
+	case SIGTERM:
+		event_loopexit(NULL);
+	}
+}
+