1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2018-2024 Netflix
5 * Author: Maksim Yevmenkin <maksim.yevmenkin@gmail.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30#define ACCEPT_FILTER_MOD
31
32#include <sys/param.h>
33#include <sys/kernel.h>
34#include <sys/mbuf.h>
35#include <sys/module.h>
36#include <sys/signalvar.h>
37#include <sys/sysctl.h>
38#include <sys/socketvar.h>
39
40static int sbfull(struct sockbuf *sb);
41static uint8_t sbmget8(struct mbuf *m, int offset);
42static int so_hastls(struct socket *so, void *arg, int waitflag);
43
44ACCEPT_FILTER_DEFINE(accf_tls, "tlsready", so_hastls, NULL, NULL, 1);
45
46static int
47sbfull(struct sockbuf *sb)
48{
49
50	return (sbused(sb) >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax);
51}
52
53static uint8_t
54sbmget8(struct mbuf *m, int offset)
55{
56	struct mbuf *n = m->m_nextpkt;
57
58	while (m != NULL && offset >= m->m_len) {
59		offset -= m->m_len;
60		m = m->m_next;
61		if (m == NULL) {
62			m = n;
63			n = m->m_nextpkt;
64		}
65	}
66
67	return *(mtod(m, uint8_t *) + offset);
68}
69
70static int
71so_hastls(struct socket *so, void *arg, int waitflag)
72{
73	struct sockbuf	*sb = &so->so_rcv;
74	int		avail;
75	uint16_t	reclen;
76
77	if ((sb->sb_state & SBS_CANTRCVMORE) || sbfull(sb))
78		return (SU_ISCONNECTED); /* can't wait any longer */
79
80	/*
81	 * struct {
82	 * 	ContentType type;		- 1 byte, 0x16 handshake
83	 * 	ProtocolVersion version;	- 2 bytes (major, minor)
84	 * 	uint16 length;			- 2 bytes, NBO, 2^14 max
85	 * 	opaque fragment[TLSPlaintext.length];
86	 * } TLSPlaintext;
87	 */
88
89	/* Did we get at least 5 bytes */
90	avail = sbavail(sb);
91	if (avail < 5)
92		return (SU_OK); /* nope */
93
94	/* Does this look like TLS handshake? */
95	if (sbmget8(sb->sb_mb, 0) != 0x16)
96		return (SU_ISCONNECTED); /* nope */
97
98	/* Did we get a complete TLS record? */
99	reclen  = (uint16_t) sbmget8(sb->sb_mb, 3) << 8;
100	reclen |= (uint16_t) sbmget8(sb->sb_mb, 4);
101
102	if (reclen <= 16384 && avail < (int) 5 + reclen)
103		return (SU_OK); /* nope */
104
105	return (SU_ISCONNECTED);
106}
107