Return to evbuffer_tls.c CVS log

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Call tls_close() in libevent TLS wrapper of syslogd when the other
side terminates the TLS connection.  It results in a proper shutdown
and the TLS peer has a chance to detect errors.  This is expecially
important for the client side.  Due to the reduced TLS 1.3 handshake,
errors might be undetected and log messages dropped silently.  By
doing a matching TLS shutdown on his side, the client can receive
the error.
Instead of checking socket writability and calling tls_close()
repeatedly, syslogd calls it only once.  As the other side has
closed the connection anyway it is our turn to write the shutdown
message.  Do not care about errors here and avoid complexity.
OK tb@

/*	$OpenBSD: evbuffer_tls.c,v 1.13 2022/03/22 22:58:00 bluhm Exp $ */

/*
 * Copyright (c) 2002-2004 Niels Provos <provos@citi.umich.edu>
 * Copyright (c) 2014-2015 Alexander Bluhm <bluhm@openbsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * 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.
 */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>

#include <errno.h>
#include <event.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tls.h>

#include "evbuffer_tls.h"

/* prototypes */

void bufferevent_read_pressure_cb(struct evbuffer *, size_t, size_t, void *);
static void buffertls_readcb(int, short, void *);
static void buffertls_writecb(int, short, void *);
static void buffertls_handshakecb(int, short, void *);
int evtls_read(struct evbuffer *, int, int, struct tls *);
int evtls_write(struct evbuffer *, int, struct tls *);

static int
bufferevent_add(struct event *ev, int timeout)
{
	struct timeval tv, *ptv = NULL;

	if (timeout) {
		timerclear(&tv);
		tv.tv_sec = timeout;
		ptv = &tv;
	}

	return (event_add(ev, ptv));
}

static void
buffertls_readcb(int fd, short event, void *arg)
{
	struct buffertls *buftls = arg;
	struct bufferevent *bufev = buftls->bt_bufev;
	struct tls *ctx = buftls->bt_ctx;
	int res = 0;
	short what = EVBUFFER_READ;
	size_t len;
	int howmuch = -1;

	if (event == EV_TIMEOUT) {
		what |= EVBUFFER_TIMEOUT;
		goto error;
	}

	/*
	 * If we have a high watermark configured then we don't want to
	 * read more data than would make us reach the watermark.
	 */
	if (bufev->wm_read.high != 0) {
		howmuch = bufev->wm_read.high - EVBUFFER_LENGTH(bufev->input);
		/* we might have lowered the watermark, stop reading */
		if (howmuch <= 0) {
			struct evbuffer *buf = bufev->input;
			event_del(&bufev->ev_read);
			evbuffer_setcb(buf,
			    bufferevent_read_pressure_cb, bufev);
			return;
		}
	}

	res = evtls_read(bufev->input, fd, howmuch, ctx);
	switch (res) {
	case TLS_WANT_POLLIN:
		bufferevent_add(&bufev->ev_read, bufev->timeout_read);
		return;
	case TLS_WANT_POLLOUT:
		event_del(&bufev->ev_write);
		event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_readcb,
		    buftls);
		bufferevent_add(&bufev->ev_write, bufev->timeout_write);
		return;
	case -1:
		what |= EVBUFFER_ERROR;
		break;
	case 0:
		tls_close(ctx);
		what |= EVBUFFER_EOF;
		break;
	}
	if (res <= 0)
		goto error;

	event_del(&bufev->ev_write);
	event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_writecb, buftls);
	if (bufev->enabled & EV_READ)
		bufferevent_add(&bufev->ev_read, bufev->timeout_read);
	if (EVBUFFER_LENGTH(bufev->output) != 0 && bufev->enabled & EV_WRITE)
		bufferevent_add(&bufev->ev_write, bufev->timeout_write);

	/* See if this callbacks meets the water marks */
	len = EVBUFFER_LENGTH(bufev->input);
	if (bufev->wm_read.low != 0 && len < bufev->wm_read.low)
		return;
	if (bufev->wm_read.high != 0 && len >= bufev->wm_read.high) {
		struct evbuffer *buf = bufev->input;
		event_del(&bufev->ev_read);

		/* Now schedule a callback for us when the buffer changes */
		evbuffer_setcb(buf, bufferevent_read_pressure_cb, bufev);
	}

	/* Invoke the user callback - must always be called last */
	if (bufev->readcb != NULL)
		(*bufev->readcb)(bufev, bufev->cbarg);
	return;

 error:
	(*bufev->errorcb)(bufev, what, bufev->cbarg);
}

static void
buffertls_writecb(int fd, short event, void *arg)
{
	struct buffertls *buftls = arg;
	struct bufferevent *bufev = buftls->bt_bufev;
	struct tls *ctx = buftls->bt_ctx;
	int res = 0;
	short what = EVBUFFER_WRITE;

	if (event == EV_TIMEOUT) {
		what |= EVBUFFER_TIMEOUT;
		goto error;
	}

	if (EVBUFFER_LENGTH(bufev->output) != 0) {
		res = evtls_write(bufev->output, fd, ctx);
		switch (res) {
		case TLS_WANT_POLLIN:
			event_del(&bufev->ev_read);
			event_set(&bufev->ev_read, fd, EV_READ,
			    buffertls_writecb, buftls);
			bufferevent_add(&bufev->ev_read, bufev->timeout_read);
			return;
		case TLS_WANT_POLLOUT:
			bufferevent_add(&bufev->ev_write, bufev->timeout_write);
			return;
		case -1:
			what |= EVBUFFER_ERROR;
			break;
		case 0:
			what |= EVBUFFER_EOF;
			break;
		}
		if (res <= 0)
			goto error;
	}

	event_del(&bufev->ev_read);
	event_set(&bufev->ev_read, fd, EV_READ, buffertls_readcb, buftls);
	if (bufev->enabled & EV_READ)
		bufferevent_add(&bufev->ev_read, bufev->timeout_read);
	if (EVBUFFER_LENGTH(bufev->output) != 0 && bufev->enabled & EV_WRITE)
		bufferevent_add(&bufev->ev_write, bufev->timeout_write);

	/*
	 * Invoke the user callback if our buffer is drained or below the
	 * low watermark.
	 */
	if (bufev->writecb != NULL &&
	    EVBUFFER_LENGTH(bufev->output) <= bufev->wm_write.low)
		(*bufev->writecb)(bufev, bufev->cbarg);

	return;

 error:
	(*bufev->errorcb)(bufev, what, bufev->cbarg);
}

static void
buffertls_handshakecb(int fd, short event, void *arg)
{
	struct buffertls *buftls = arg;
	struct bufferevent *bufev = buftls->bt_bufev;
	struct tls *ctx = buftls->bt_ctx;
	int res = 0;
	short what = EVBUFFER_HANDSHAKE;

	if (event == EV_TIMEOUT) {
		what |= EVBUFFER_TIMEOUT;
		goto error;
	}

	res = tls_handshake(ctx);
	switch (res) {
	case TLS_WANT_POLLIN:
		bufferevent_add(&bufev->ev_read, bufev->timeout_read);
		return;
	case TLS_WANT_POLLOUT:
		bufferevent_add(&bufev->ev_write, bufev->timeout_write);
		return;
	case -1:
		what |= EVBUFFER_ERROR;
		break;
	}
	if (res == -1)
		goto error;

	/* Handshake was successful, change to read and write callback. */
	event_del(&bufev->ev_read);
	event_del(&bufev->ev_write);
	event_set(&bufev->ev_read, fd, EV_READ, buffertls_readcb, buftls);
	event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_writecb, buftls);
	if (bufev->enabled & EV_READ)
		bufferevent_add(&bufev->ev_read, bufev->timeout_read);
	if (EVBUFFER_LENGTH(bufev->output) != 0 && bufev->enabled & EV_WRITE)
		bufferevent_add(&bufev->ev_write, bufev->timeout_write);

	return;

 error:
	(*bufev->errorcb)(bufev, what, bufev->cbarg);
}

void
buffertls_set(struct buffertls *buftls, struct bufferevent *bufev,
    struct tls *ctx, int fd)
{
	bufferevent_setfd(bufev, fd);
	event_set(&bufev->ev_read, fd, EV_READ, buffertls_readcb, buftls);
	event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_writecb, buftls);
	buftls->bt_bufev = bufev;
	buftls->bt_ctx = ctx;
}

void
buffertls_accept(struct buffertls *buftls, int fd)
{
	struct bufferevent *bufev = buftls->bt_bufev;

	event_del(&bufev->ev_read);
	event_del(&bufev->ev_write);
	event_set(&bufev->ev_read, fd, EV_READ, buffertls_handshakecb, buftls);
	event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_handshakecb,
	    buftls);
	bufferevent_add(&bufev->ev_read, bufev->timeout_read);
}

void
buffertls_connect(struct buffertls *buftls, int fd)
{
	struct bufferevent *bufev = buftls->bt_bufev;

	event_del(&bufev->ev_read);
	event_del(&bufev->ev_write);
	event_set(&bufev->ev_read, fd, EV_READ, buffertls_handshakecb, buftls);
	event_set(&bufev->ev_write, fd, EV_WRITE, buffertls_handshakecb,
	    buftls);
	bufferevent_add(&bufev->ev_write, bufev->timeout_write);
}

/*
 * Reads data from a file descriptor into a buffer.
 */

#define EVBUFFER_MAX_READ	16384

int
evtls_read(struct evbuffer *buf, int fd, int howmuch, struct tls *ctx)
{
	u_char *p;
	size_t oldoff = buf->off;
	int n = EVBUFFER_MAX_READ;

	if (howmuch < 0 || howmuch > n)
		howmuch = n;

	/* If we don't have FIONREAD, we might waste some space here */
	if (evbuffer_expand(buf, howmuch) == -1)
		return (-1);

	/* We can append new data at this point */
	p = buf->buffer + buf->off;

	n = tls_read(ctx, p, howmuch);
	if (n <= 0)
		return (n);

	buf->off += n;

	/* Tell someone about changes in this buffer */
	if (buf->off != oldoff && buf->cb != NULL)
		(*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

	return (n);
}

int
evtls_write(struct evbuffer *buffer, int fd, struct tls *ctx)
{
	int n;

	n = tls_write(ctx, buffer->buffer, buffer->off);
	if (n <= 0)
		return (n);
	evbuffer_drain(buffer, n);

	return (n);
}