--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/maildrop.c	Thu Mar 27 09:53:52 2014 +0500
@@ -0,0 +1,412 @@
+/*
+ * 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/param.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+
+#include <event.h>
+#include <fcntl.h>
+#include <pwd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "imsgev.h"
+#include "pop3d.h"
+
+static void session_imsgev(struct imsgev *, int, struct imsg *);
+static void update(struct imsgev *, struct imsg *, struct m_backend *);
+static void retr(struct imsgev *, struct imsg *, struct m_backend *);
+static void dele(struct imsgev *, struct imsg *, struct m_backend *);
+static void rset(struct imsgev *, struct imsg *, struct m_backend *);
+static void list(struct imsgev *, struct imsg *, struct m_backend *);
+static void list_all(struct imsgev *, struct imsg *, struct m_backend *, int);
+static void do_list(unsigned int, size_t *, char *, size_t);
+static void *do_list_all(int, size_t *);
+static struct m_backend *m_backend_lookup(enum m_type);
+static void sig_handler(int, short, void *);
+static void needfd(struct imsgev *);
+static size_t expand(char *, const char *, size_t, struct passwd *);
+
+static struct mdrop m;
+
+void
+maildrop_init(uint32_t session_id, int pair[2], struct passwd *pw,
+    int type, const char *path)
+{
+	struct imsgev		iev_session;
+	struct event		ev_sigint, ev_sigterm;
+	struct stats		stats;
+	struct m_backend	*mb;
+	char			buf[MAXPATHLEN];
+	pid_t			pid;
+	mode_t			old_mask;
+	int			fd, flags, res = -1;
+
+	if (seteuid(pw->pw_uid) < 0)
+		fatal("cannot lower privileges");
+
+	pid = fork();
+	if (seteuid(0) < 0)
+		fatal("cannot restore privileges");
+
+	if (pid < 0)
+		fatal("maildrop: fork");
+
+	if (pid > 0)
+		return;
+
+	if (seteuid(pw->pw_uid) < 0)
+		fatal("cannot lower privileges");
+
+	close(pair[0]);
+	setproctitle("maildrop");
+	if ((mb = m_backend_lookup(type)) == NULL)
+		fatalx("maildrop: invalid backend");
+
+	if (expand(buf, path, sizeof(buf), pw) >= sizeof(buf))
+		fatalx("maildrop: path truncation");
+
+	flags = O_CREAT;
+	if (type == M_MBOX)
+		flags |= O_RDWR;
+	else
+		flags |= O_RDONLY;
+
+	old_mask = umask(S_IXUSR|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH);
+	if ((fd = open(buf, flags)) == -1)
+		logit(LOG_CRIT, "%zu: failed to open %s", session_id , buf);
+
+	if (fd != -1) {
+		m.fd = fd;
+		res = mb->init(&m, &stats.nmsgs, &stats.sz);
+	}
+
+	umask(old_mask);
+	if (seteuid(0) < 0)
+		fatal("cannot restore privileges");
+
+	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");
+
+	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_session, pair[1], mb, session_imsgev, needfd);
+
+	if (res == 0) {
+		imsgev_xcompose(&iev_session, IMSG_MAILDROP_INIT, session_id,
+		    0, -1, &stats, sizeof(struct stats), "maildrop_init");
+	} else {
+		logit(LOG_CRIT, "%zu: maildrop init failed %s",
+		    session_id, buf);
+		imsgev_xcompose(&iev_session, IMSG_MAILDROP_INIT, session_id,
+		    0, -1, NULL, 0, "maildrop_init");
+	}
+
+	if (event_dispatch() < 0)
+		fatal("event_dispatch");
+
+	logit(LOG_INFO, "maildrop process exiting");
+	_exit(0);
+}
+
+/*
+ * Build dst by substituting '~' with user's home dir and '%u' with user name
+ * in src. Return the length of string built. If return value >= dst_sz then
+ * dst is truncated. 
+ */
+static size_t
+expand(char *dst, const char *src, size_t dst_sz, struct passwd *pw)
+{
+	size_t	i = 0, r;
+	int	c;
+
+	while ((c = *src++)) {
+		if (i >= dst_sz)
+			break;
+
+		switch (c) {
+		case '~':
+			if ((r = strlcpy(&dst[i], pw->pw_dir,
+			    (dst_sz - i))) >= (dst_sz - i)) {
+				i += r;
+				goto end;
+			}
+			i += r;
+			break;
+		case '%':
+			if (*src == 'u') {
+				if ((r = strlcpy(&dst[i], pw->pw_name,
+				    (dst_sz - i))) >= (dst_sz - i)) {
+					i += r;
+					goto end;
+				}
+				i += r;
+				src++;
+			} else
+				dst[i++] = c;
+			break;
+		default:
+			dst[i++] = c;
+			break;
+		}
+	}
+
+end:
+	if (c)
+		while ((c = *src++))
+			i++;
+
+	dst[dst_sz - 1] = '\0';
+	return (i);
+}
+
+static void
+session_imsgev(struct imsgev *iev, int code, struct imsg *imsg)
+{
+	struct m_backend	*mb = iev->data;
+	int			uidl = 0;		
+
+	switch (code) {
+	case IMSGEV_IMSG:
+		switch (imsg->hdr.type) {
+		case IMSG_MAILDROP_UPDATE:
+			update(iev, imsg, mb);
+			break;
+		case IMSG_MAILDROP_RETR:
+			retr(iev, imsg, mb);
+			break;
+		case IMSG_MAILDROP_DELE:
+			dele(iev, imsg, mb);
+			break;
+		case IMSG_MAILDROP_RSET:
+			rset(iev, imsg, mb);
+			break;
+		case IMSG_MAILDROP_LIST:
+			list(iev, imsg, mb);
+			break;
+		case IMSG_MAILDROP_UIDLALL:
+			uidl = 1;
+			/* FALLTHROUGH */
+		case IMSG_MAILDROP_LISTALL:
+			list_all(iev, imsg, mb, uidl);
+			break;
+		default:
+			logit(LOG_DEBUG, "%s: unexpected imsg %u",
+			    __func__, imsg->hdr.type);
+			break;
+		}
+		break;
+	case IMSGEV_EREAD:
+	case IMSGEV_EWRITE:
+	case IMSGEV_EIMSG:
+		fatal("maildrop: imsgev read/write error");
+		break;
+	case IMSGEV_DONE:
+		event_loopexit(NULL);
+		break;
+	}
+}
+
+static void
+update(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)
+{
+	int		res;
+	uint32_t	session_id = imsg->hdr.peerid;
+
+	if ((res = mb->update(&m)) == 0)
+		logit(LOG_INFO, "%zu: maildrop updated", session_id);
+	else
+		logit(LOG_CRIT, "%zu: maildrop updated failed", session_id);
+
+	imsgev_xcompose(iev, IMSG_MAILDROP_UPDATE, session_id,  0,
+	    -1, &res, sizeof(res), "maildrop_update");
+}
+
+static void
+retr(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)
+{
+	struct retr_res	res;
+	struct retr_req	*req = imsg->data;
+	int		fd;
+
+	fd = mb->retr(&m, req->idx, &res.nlines, &res.offset);
+	/* pass on top arguments */
+	res.top = req->top;
+	res.ntop = req->ntop;
+	imsgev_xcompose(iev, IMSG_MAILDROP_RETR, imsg->hdr.peerid, 0,
+	    fd, &res, sizeof(res), "maildrop_retr");
+}
+
+static void
+dele(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)
+{
+	unsigned int	*idx = imsg->data;
+	int		res = 0;
+
+	if (m.msgs_index[*idx]->flags & F_DELE) {
+		res = -1;
+		goto end;
+	}
+
+	m.msgs_index[*idx]->flags |= F_DELE;
+end:
+	imsgev_xcompose(iev, IMSG_MAILDROP_DELE, imsg->hdr.peerid, 0,
+	    -1, &res, sizeof(res), "maildrop_dele");
+}
+
+static void
+rset(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)
+{
+	size_t	i;
+
+	for (i = 0; i < m.nmsgs; i++)
+		m.msgs_index[i]->flags = 0;
+
+	imsgev_xcompose(iev, IMSG_MAILDROP_RSET, imsg->hdr.peerid, 0,
+	    -1, NULL, 0, "maildrop_rset");
+}
+
+static void
+list(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)
+{
+	struct list_req	*req = imsg->data;
+	struct list_res	res;
+	char		hash[SHA1_DIGEST_STRING_LENGTH];
+	size_t		sz;
+
+	res.idx = req->idx;
+	do_list(req->idx, &sz, hash, sizeof(hash));
+	res.uidl = req->uidl;
+	if (res.uidl)
+		strlcpy(res.u.hash, hash, sizeof(res.u.hash));
+	else
+		res.u.sz = sz;
+
+	imsgev_xcompose(iev, IMSG_MAILDROP_LIST, imsg->hdr.peerid, 0,
+	    -1, &res, sizeof(res), "maildrop_list");
+
+}
+
+static void
+list_all(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb, int uidl)
+{
+	void	*res;
+	size_t	sz;
+
+	res = do_list_all(uidl, &sz);
+	/* XXX watchout for sz > MAX_IMSGSIZE */
+	imsgev_xcompose(iev,
+	    (uidl) ? IMSG_MAILDROP_UIDLALL : IMSG_MAILDROP_LISTALL,
+	    imsg->hdr.peerid, 0, -1, res, sz, "maildrop_list");
+}
+
+static void
+do_list(unsigned int idx, size_t *sz, char *hash, size_t hash_sz)
+{
+	if (m.msgs_index[idx]->flags & F_DELE) {
+		*sz = 0;
+		strlcpy(hash, "", hash_sz);
+		return;
+	}
+
+	*sz = m.msgs_index[idx]->sz;
+	strlcpy(hash, m.msgs_index[idx]->hash, hash_sz);
+}
+
+static void *
+do_list_all(int uidl, size_t *sz)
+{
+	size_t	i, j, *nsz = NULL;
+	char	*nhash = NULL;
+
+	if (uidl) {
+		nhash = xcalloc(m.nmsgs, SHA1_DIGEST_STRING_LENGTH, "list_all");
+	} else
+		nsz = xcalloc(m.nmsgs, sizeof(size_t), "list_all");
+
+	for (i = 0; i < m.nmsgs; i++) {
+			
+		if (uidl) {
+			j = i * SHA1_DIGEST_STRING_LENGTH;
+			if (m.msgs_index[i]->flags & F_DELE)
+				nhash[j] = '\0';
+			else
+				strlcpy(nhash + j, m.msgs_index[i]->hash,
+			    	    SHA1_DIGEST_STRING_LENGTH);
+		} else {
+			if (m.msgs_index[i]->flags & F_DELE)
+				nsz[i] = 0;
+			else
+				nsz[i] = m.msgs_index[i]->sz;
+		}
+	}
+
+	if (uidl) {
+		*sz = m.nmsgs * SHA1_DIGEST_STRING_LENGTH;
+		return (nhash);
+	} else {
+		*sz = m.nmsgs * sizeof(size_t);
+		return (nsz);
+	}
+}
+
+static void
+needfd(struct imsgev *iev)
+{
+	fatalx("maildrop should never need an fd");
+}
+
+static void
+sig_handler(int sig, short event, void *arg)
+{
+	switch (sig) {
+	case SIGINT:
+	case SIGTERM:
+		event_loopexit(NULL);
+	}
+}
+
+extern struct m_backend m_backend_mbox;
+extern struct m_backend m_backend_maildir;
+
+static struct m_backend *
+m_backend_lookup(enum m_type type)
+{
+	switch (type) {
+	case M_MBOX:
+		return &m_backend_mbox;
+		break;
+	case M_MAILDIR:
+		return &m_backend_maildir;
+		break;
+	default:
+		fatalx("m_backend_lookup: invalid m_type");
+	};
+
+	return (NULL);
+}
+