--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/session.c	Thu Mar 27 09:53:52 2014 +0500
@@ -0,0 +1,754 @@
+/*
+ * 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 <ctype.h>
+#include <err.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "imsgev.h"
+#include "pop3d.h"
+#include "ssl.h"
+
+#define MAXLINESIZE	2048
+#define TIMEOUT		600000
+
+enum pop_command {
+	CMD_STLS = 0,
+	CMD_CAPA,
+	CMD_USER,
+	CMD_PASS,
+	CMD_QUIT,
+	CMD_STAT,
+	CMD_RETR,
+	CMD_LIST,
+	CMD_DELE,
+	CMD_RSET,
+	CMD_TOP,
+	CMD_UIDL,
+	CMD_NOOP
+};
+
+enum arg_constraint {
+	OPTIONAL = 1,
+	PROHIBITED,
+	REQUIRED
+};
+
+static struct {int code; enum arg_constraint c; const char *cmd;} commands[] = {
+	{CMD_STLS, PROHIBITED, "STLS"},
+	{CMD_CAPA, PROHIBITED, "CAPA"},
+	{CMD_USER, REQUIRED, "USER"},
+	{CMD_PASS, REQUIRED, "PASS"},
+	{CMD_QUIT, PROHIBITED, "QUIT"},
+	{CMD_STAT, PROHIBITED, "STAT"},
+	{CMD_RETR, REQUIRED, "RETR"},
+	{CMD_LIST, OPTIONAL, "LIST"},
+	{CMD_DELE, REQUIRED, "DELE"},
+	{CMD_RSET, PROHIBITED, "RSET"},
+	{CMD_TOP,  REQUIRED, "TOP"},
+	{CMD_UIDL, OPTIONAL, "UIDL"},
+	{CMD_NOOP, PROHIBITED, "NOOP"},
+	{-1, OPTIONAL, NULL}
+};
+
+static void auth_request(struct session *);
+static void capa(struct session *);
+static void command(struct session *, int, char *);
+static void session_io(struct io *, int);
+static void parse(struct session *, char *);
+static void auth_command(struct session *, int, char *);
+static void trans_command(struct session *, int, char *);
+static void get_list_all(struct session *, int);
+static void get_list(struct session *, unsigned int, int);
+static void maildrop_imsgev(struct imsgev *, int, struct imsg *);
+static void handle_init(struct session *, struct imsg *);
+static void handle_retr(struct session *, struct imsg *);
+static void handle_dele(struct session *, struct imsg *);
+static void handle_list(struct session *, struct imsg *);
+static void handle_list_all(struct session *, struct imsg *, int);
+static void handle_update(struct session *, struct imsg *);
+static void needfd(struct imsgev *);
+static void pop3_debug(char *, ...);
+static void session_write(struct session *, const char *, size_t);
+static const char *strstate(enum state);
+
+struct session_tree	sessions;
+static int		_pop3_debug = 1;
+
+void
+session_init(struct listener *l, int fd)
+{
+	struct session	*s;
+	void		*ssl;
+	extern void	*ssl_ctx;
+
+	s = xcalloc(1, sizeof(*s), "session_init");
+	s->l = l;
+	if (iobuf_init(&s->iobuf, 0, 0) == -1)
+		fatal("iobuf_init");
+
+	io_init(&s->io, fd, s, session_io, &s->iobuf);
+	io_set_timeout(&s->io, TIMEOUT);
+	s->id = arc4random();
+	s->sock = fd;
+	s->state = AUTH;
+	if (s->l->flags & POP3S) {
+		s->flags |= POP3S;
+		ssl = pop3s_init(ssl_ctx, s->sock);
+		io_set_read(&s->io);
+		io_start_tls(&s->io, ssl);
+		return;
+	}
+
+	log_connect(s->id, &l->ss, l->ss.ss_len);
+	SPLAY_INSERT(session_tree, &sessions, s);
+	session_reply(s, "%s", "+OK pop3d ready");
+	io_set_write(&s->io);
+}
+
+void
+session_close(struct session *s, int flush)
+{
+	struct session *entry;
+
+	entry = SPLAY_REMOVE(session_tree, &sessions,  s);
+	if (entry == NULL) {
+		 /* STARTTLS session was in progress and got interrupted */
+		logit(LOG_DEBUG, "%u: not in tree", s->id);
+		entry = s;
+	}
+
+	if (flush) {
+		if (entry->flags & POP3S)
+			iobuf_flush_ssl(&entry->iobuf, entry->io.ssl);
+		else
+			iobuf_flush(&entry->iobuf, entry->io.sock);
+	}
+
+	iobuf_clear(&entry->iobuf);
+	io_clear(&entry->io);
+	imsgev_clear(&entry->iev_maildrop);
+	imsgev_close(&entry->iev_maildrop);
+	logit(LOG_INFO, "%u: session closed", entry->id);
+	free(entry);
+}
+
+static void
+session_io(struct io *io, int evt)
+{
+	struct session	*s = io->arg;
+	char		*line;
+	size_t		len;
+
+	pop3_debug("%u: %s", s->id, io_strevent(evt));
+	switch (evt) {
+	case IO_DATAIN:
+		line = iobuf_getline(&s->iobuf, &len);
+		if (line == NULL) {
+			iobuf_normalize(&s->iobuf);
+			break;
+		}
+		if (strncasecmp(line, "PASS", 4) == 0)
+			pop3_debug(">>> PASS");
+		else
+			pop3_debug(">>> %s", line);
+		parse(s, line);
+		break;
+	case IO_LOWAT:
+		if (iobuf_queued(&s->iobuf) == 0)
+			io_set_read(io);
+		break;
+	case IO_TLSREADY:
+		/* greet only for pop3s, STLS already greeted */
+		if (s->flags & POP3S) {
+			log_connect(s->id, &s->l->ss, s->l->ss.ss_len);
+			session_reply(s, "%s", "+OK pop3 ready");
+			io_set_write(&s->io);
+		}
+		SPLAY_INSERT(session_tree, &sessions, s);
+		/* mark STLS session as secure */
+		s->flags |= POP3S;
+		logit(LOG_INFO, "%u: TLS ready", s->id);
+		break;
+	case IO_DISCONNECTED:
+	case IO_TIMEOUT:
+	case IO_ERROR:
+		session_close(s, 0);
+		break;
+	default:
+		logit(LOG_DEBUG, "unknown event %s", io_strevent(evt));
+		break;
+	}
+}
+
+static void
+parse(struct session *s, char *line)
+{
+	enum arg_constraint	c = OPTIONAL;
+	int			i, cmd = -1;
+	char			*args;
+
+	/* trim newline */
+	line[strcspn(line, "\n")] = '\0';
+
+	args = strchr(line, ' ');
+	if (args) {
+		*args++ = '\0';
+		while (isspace((unsigned char)*args))
+			args++;
+	}
+
+	for (i = 0; commands[i].code != -1; i++) {
+		if (strcasecmp(line, commands[i].cmd) == 0) {
+			cmd = commands[i].code;
+			c = commands[i].c;
+			break;
+		}
+	}
+
+	if (cmd == -1) {
+		logit(LOG_INFO, "%u: invalid command %s", s->id, line);
+		session_reply(s, "%s", "-ERR invalid command");
+		io_set_write(&s->io);
+		return;
+	}
+
+	if (c == PROHIBITED && args) {
+		session_reply(s, "%s", "-ERR no arguments allowed");
+		io_set_write(&s->io);
+		return;
+	} else if ((c == REQUIRED) &&
+	    (args == NULL || strlen(args) >= ARGLEN)) {
+		session_reply(s, "%s", "-ERR args required or too long");
+		io_set_write(&s->io);
+		return;
+	}
+
+	command(s, cmd, args);
+}
+
+static void
+command(struct session *s, int cmd, char *args)
+{
+	switch (s->state) {
+	case AUTH:
+		auth_command(s, cmd, args);
+		break;
+	case TRANSACTION:
+		trans_command(s, cmd, args);
+		break;
+	case UPDATE:
+		session_reply(s, "%s", "-ERR commands not allowed");
+		io_set_write(&s->io);
+		break;
+	default:
+		fatalx("Invalid state");
+	}
+}
+
+static void
+auth_command(struct session *s, int cmd, char *args)
+{
+	extern void	*ssl_ctx;
+	void		*ssl;
+
+	switch (cmd) {
+	case CMD_STLS:
+		if (s->flags & POP3S) {
+			session_reply(s, "%s", "-ERR already secured");
+			break;
+		}
+		session_reply(s, "%s", "+OK");
+		io_set_write(&s->io);
+		iobuf_flush(&s->iobuf, s->io.sock);
+		/* add back when IO_TLSREADY. */
+		SPLAY_REMOVE(session_tree, &sessions, s);
+		ssl = pop3s_init(ssl_ctx, s->sock);
+		io_set_read(&s->io);
+		io_start_tls(&s->io, ssl);
+		return;
+	case CMD_CAPA:
+		capa(s);
+		break;
+	case CMD_USER:
+		strlcpy(s->user, args, sizeof(s->user));
+		session_reply(s, "%s", "+OK");
+		break;
+	case CMD_PASS:
+		if (s->user[0] == '\0') {
+			session_reply(s, "%s", "-ERR no USER specified");
+			break;
+		}
+		strlcpy(s->pass, args, sizeof(s->pass));
+		auth_request(s);
+		return;
+	case CMD_QUIT:
+		session_reply(s, "%s", "+OK");
+		io_set_write(&s->io);
+		session_close(s, 1);
+		return;
+	default:
+		session_reply(s, "%s", "-ERR invalid command");
+		break;
+	}
+
+	io_set_write(&s->io);
+}
+
+static void
+auth_request(struct session *s)
+{
+	extern struct imsgev	iev_pop3d;
+	struct auth_req		req;
+
+	memset(&req, 0, sizeof(req));
+	strlcpy(req.user, s->user, sizeof(req.user));
+	strlcpy(req.pass, s->pass, sizeof(req.pass));
+	imsgev_xcompose(&iev_pop3d, IMSG_AUTH, s->id, 0, -1,
+	    &req, sizeof(req), "auth_request");
+}
+
+static void
+capa(struct session *s)
+{
+	session_reply(s, "%s", "+OK");
+	session_reply(s, "%s", "STLS");
+	session_reply(s, "%s", "USER");
+	session_reply(s, "%s", "TOP");
+	session_reply(s, "%s", "UIDL");
+	session_reply(s, "%s", "IMPLEMENTATION pop3d");
+	session_reply(s, "%s", ".");
+}
+
+static void
+trans_command(struct session *s, int cmd, char *args)
+{
+	struct retr_req	retr_req;
+	unsigned int	idx, n;
+	char		*c;
+	const char	*errstr;
+	int		uidl = 0;
+
+	memset(&retr_req, 0, sizeof(retr_req));
+	switch (cmd) {
+	case CMD_CAPA:
+		capa(s);
+		break;
+	case CMD_STAT:
+		session_reply(s, "%s %zu %zu", "+OK", s->nmsgs, s->m_sz);
+		break;
+	case CMD_TOP:
+		if ((c = strchr(args, ' ')) == NULL) {
+			session_reply(s, "%s", "-ERR invalid arguments");
+			break;
+		}
+		*c++ = '\0';
+		n = strtonum(c, 0, UINT_MAX, &errstr);
+		if (errstr) {
+			session_reply(s, "%s", "-ERR invalid n");
+			break;
+		}
+		retr_req.top = 1;
+		retr_req.ntop = n;
+		/* FALLTRHROUGH */
+	case CMD_RETR:
+		if (!get_index(s, args, &retr_req.idx))
+			break;
+		imsgev_xcompose(&s->iev_maildrop, IMSG_MAILDROP_RETR,
+		    s->id, 0, -1, &retr_req, sizeof(retr_req), "trans_command");
+		return;
+	case CMD_NOOP:
+		session_reply(s, "%s", "+OK");
+		break;
+	case CMD_DELE:
+		if (!get_index(s, args, &idx))
+			break;
+		imsgev_xcompose(&s->iev_maildrop, IMSG_MAILDROP_DELE,
+		    s->id, 0, -1, &idx, sizeof(idx), "trans_command");
+		return;
+	case CMD_RSET:
+		imsgev_xcompose(&s->iev_maildrop, IMSG_MAILDROP_RSET,
+		    s->id, 0, -1, NULL, 0, "trans_command");
+		return;
+	case CMD_UIDL:
+		uidl = 1;
+		/* FALLTHROUGH */
+	case CMD_LIST:
+		if (args) {
+			if (!get_index(s, args, &idx))
+				break;
+			get_list(s, idx, uidl);
+		} else
+			get_list_all(s, uidl);
+		return;
+	case CMD_QUIT:
+		imsgev_xcompose(&s->iev_maildrop, IMSG_MAILDROP_UPDATE,
+		    s->id, 0, -1, NULL, 0, "trans_command");
+		session_set_state(s, UPDATE);
+		return;
+	default:
+		session_reply(s, "%s", "-ERR invalid command");
+		break;
+	}
+
+	io_set_write(&s->io);
+}
+
+static void
+get_list_all(struct session *s, int uidl)
+{
+	imsgev_xcompose(&s->iev_maildrop,
+	    (uidl) ? IMSG_MAILDROP_UIDLALL : IMSG_MAILDROP_LISTALL,
+	    s->id, 0, -1, NULL, 0, "list_all");
+}
+
+static void
+get_list(struct session *s, unsigned int i, int uidl)
+{
+	struct list_req	req;
+
+	req.idx = i;
+	req.uidl = uidl;
+	imsgev_xcompose(&s->iev_maildrop, IMSG_MAILDROP_LIST,
+	    s->id, 0, -1, &req, sizeof(req), "list");
+}
+
+void
+session_imsgev_init(struct session *s, int fd)
+{
+	imsgev_init(&s->iev_maildrop, fd, s, maildrop_imsgev, needfd);
+}
+
+static void
+maildrop_imsgev(struct imsgev *iev, int code, struct imsg *imsg)
+{
+	struct session	key, *r;
+	int		uidl = 0;
+
+	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("session: session lost");
+		}
+		switch (imsg->hdr.type) {
+		case IMSG_MAILDROP_INIT:
+			handle_init(r, imsg);
+			break;
+		case IMSG_MAILDROP_RETR:
+			handle_retr(r, imsg);
+			break;
+		case IMSG_MAILDROP_DELE:
+			handle_dele(r, imsg);
+			break;
+		case IMSG_MAILDROP_RSET:
+			session_reply(r, "%s", "+OK reset");
+			io_set_write(&r->io);
+			break;
+		case IMSG_MAILDROP_LIST:
+			handle_list(r, imsg);
+			break;
+		case IMSG_MAILDROP_UIDLALL:
+			uidl = 1;
+			/* FALLTHROUGH */
+		case IMSG_MAILDROP_LISTALL:
+			handle_list_all(r, imsg, uidl);
+			break;
+		case IMSG_MAILDROP_UPDATE:
+			handle_update(r, imsg);
+			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("session: imsgev read/write error");
+		break;
+	}
+}
+
+static void
+handle_init(struct session *s, struct imsg *imsg)
+{
+	size_t		datalen;
+	struct stats	*stats;
+
+	datalen = imsg->hdr.len - sizeof(imsg->hdr);
+	if (datalen) {
+		stats = imsg->data;
+		s->m_sz = stats->sz;
+		s->nmsgs = stats->nmsgs;
+		session_reply(s, "%s", "+OK maildrop ready");
+		io_set_write(&s->io);
+		session_set_state(s, TRANSACTION);
+	} else {
+		session_reply(s, "%s", "-ERR maildrop init failed");
+		io_set_write(&s->io);
+		session_close(s, 1);
+	}
+}
+
+static void
+handle_retr(struct session *s, struct imsg *imsg)
+{
+	struct retr_res	*r = imsg->data;
+	FILE		*fp;
+	char		*line;
+	size_t		len;
+
+	if (imsg->fd == -1) {
+		session_reply(s, "%s", "-ERR marked for delete");
+		io_set_write(&s->io);
+		return;
+	}
+
+	if ((fp = fdopen(imsg->fd, "r")) == NULL) {
+		logit(LOG_INFO, "%zu: retr failed", s->id);
+		session_reply(s, "%s", "-ERR RETR failed");
+		io_set_write(&s->io);
+		session_close(s, 1);
+		return;
+	}
+
+	if (fseek(fp, r->offset, SEEK_SET) == -1)
+		fatal("fseek");
+
+	session_reply(s, "%s", "+OK");
+	/* Ignore "From " line when type is mbox; maildir doesn't have it */
+	if ((line = fgetln(fp, &len)) && strncmp(line, "From ", 5))
+		session_write(s, line, len);
+
+	if (r->top) {
+		/* print headers regardless of ntop */
+		while ((line = fgetln(fp, &len))) {
+			session_write(s, line, len);
+			r->nlines -= 1;
+			if (strncmp(line , "\n", 1) == 0)
+				break;
+		}
+
+		/* print ntop lines of body */
+		while ((r->ntop-- > 0) && r->nlines-- &&
+		    (line = fgetln(fp, &len)))
+			session_write(s, line, len);
+	} else
+		while (r->nlines-- && (line = fgetln(fp, &len)))
+			session_write(s, line, len);
+
+	session_reply(s, "%s", ".");
+	io_set_write(&s->io);
+	fclose(fp);
+	close(imsg->fd);
+}
+
+static void
+handle_dele(struct session *s, struct imsg *imsg)
+{
+	int	*res = imsg->data;
+
+	if (*res == 0)
+		session_reply(s, "%s", "+OK marked for delete");
+	else
+		session_reply(s, "%s", "+ERR msg already marked delete");
+
+	io_set_write(&s->io);
+}
+
+/* DELEted msg's hash and sz will be zero, ignore them */
+static void
+handle_list(struct session *s, struct imsg *imsg)
+{
+	struct list_res	*res = imsg->data;
+
+	res->idx += 1;	/* POP3 index is 1 based */
+	if (res->uidl) {
+		if (strlen(res->u.hash))
+			session_reply(s, "+OK %zu %s", res->idx, res->u.hash);
+		else
+			session_reply(s, "-ERR marked for delete");
+	} else {
+		if (res->u.sz)
+			session_reply(s, "+OK %zu %zu", res->idx, res->u.sz);
+		else
+			session_reply(s, "-ERR marked for delete");
+	}
+
+	io_set_write(&s->io);
+}
+
+/* DELEted msg's hash and sz will be zero, ignore them */
+static void
+handle_list_all(struct session *s, struct imsg *imsg, int uidl)
+{
+	char 	*nhash = NULL;
+	size_t	datalen, i, item_sz, j, nitems, *nsz = NULL;
+
+	datalen = imsg->hdr.len - sizeof(imsg->hdr);
+	item_sz = (uidl) ? SHA1_DIGEST_STRING_LENGTH : sizeof(size_t);
+	nitems = datalen / item_sz;
+	if (uidl)
+		nhash = imsg->data;
+	else
+		nsz = imsg->data;
+
+	session_reply(s, "+OK");
+	for (i = 0; i < nitems; i++) {
+		if (uidl) {
+			j = i * SHA1_DIGEST_STRING_LENGTH;
+			if (nhash[j])
+				session_reply(s, "%zu %s", i + 1, nhash + j);
+		} else {
+			if (nsz[i])
+				session_reply(s, "%zu %zu", i + 1, nsz[i]);
+		}
+	}
+
+	session_reply(s, ".");
+	io_set_write(&s->io);
+
+}
+
+static void
+handle_update(struct session *s, struct imsg *imsg)
+{
+	int	*res = imsg->data;
+
+	if (*res == 0)
+		session_reply(s, "%s", "+OK maildrop updated");
+	else
+		session_reply(s, "%s", "-ERR maildrop update failed");
+
+	io_set_write(&s->io);
+	session_close(s, 1);
+}
+
+static void
+needfd(struct imsgev *iev)
+{
+	/* XXX */
+	fatalx("session needs an fd");
+}
+
+int
+session_cmp(struct session *a, struct session *b)
+{
+	if (a->id < b->id)
+		return (-1);
+
+	if (a->id > b->id)
+		return (1);
+
+	return (0);
+}
+
+void
+session_set_state(struct session *s, enum state newstate)
+{
+	pop3_debug("%u: %s -> %s", s->id, strstate(s->state),
+	    strstate(newstate));
+	s->state = newstate;
+}
+
+#define CASE(x) case x : return #x
+static const char *
+strstate(enum state state)
+{
+	static char buf[32];
+
+	switch (state) {
+	CASE(AUTH);
+	CASE(TRANSACTION);
+	CASE(UPDATE);
+	default:
+		snprintf(buf, sizeof(buf), "%d ???", state);
+		return (buf);
+	}
+}
+
+void
+session_reply(struct session *s, char *fmt, ...)
+{
+	va_list	ap;
+	int	n;
+	char	buf[MAXLINESIZE];
+
+	va_start(ap, fmt);
+	n = vsnprintf(buf, sizeof(buf), fmt, ap);
+	va_end(ap);
+	if (n == -1 || n > MAXLINESIZE)
+		fatalx("session_reply: response too long");
+
+	if (buf[0] == '+')
+		pop3_debug("<<< +OK");
+	else if (buf[0] == '-')
+		pop3_debug("<<< -ERR");
+
+	iobuf_xfqueue(&s->iobuf, "session_reply", "%s\r\n", buf);
+}
+
+static void
+session_write(struct session *s, const char *data, size_t len)
+{
+	/* remove terminating \n or \r\n if any */
+	if (data[len - 1] == '\n')
+		len -= 1;
+
+	if (data[len - 1] == '\r')
+		len -= 1;
+
+	/* byte stuff "." if at beginning of line */
+	if (data[0] == '.')
+		iobuf_xfqueue(&s->iobuf, "session_write", ".");
+
+	iobuf_xqueue(&s->iobuf, "session_write", data, len);
+	/* explicitly terminate with CRLF */
+	iobuf_xfqueue(&s->iobuf, "session_write", "\r\n");
+}
+
+static void
+pop3_debug(char *fmt, ...)
+{
+	va_list		ap;
+	char		buf[MAXLINESIZE];
+	int		n;
+
+	if (!_pop3_debug)
+		return;
+
+	va_start(ap, fmt);
+	n = vsnprintf(buf, sizeof(buf), fmt, ap);
+	va_end(ap);
+	if (n == -1 || n > MAXLINESIZE)
+		fatalx("pop3_debug: response too long");
+
+	logit(LOG_DEBUG, "%s", buf);
+}
+
+SPLAY_GENERATE(session_tree, session, entry, session_cmp);
+