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 #define ACCEPT_FILTER_MOD
30
31 #include <sys/param.h>
32 #include <sys/kernel.h>
33 #include <sys/mbuf.h>
34 #include <sys/module.h>
35 #include <sys/signalvar.h>
36 #include <sys/sysctl.h>
37 #include <sys/socketvar.h>
38
39 static int sbfull(struct sockbuf *sb);
40 static uint8_t sbmget8(struct mbuf *m, int offset);
41 static int so_hastls(struct socket *so, void *arg, int waitflag);
42
43 ACCEPT_FILTER_DEFINE(accf_tls, "tlsready", so_hastls, NULL, NULL, 1);
44
45 static int
sbfull(struct sockbuf * sb)46 sbfull(struct sockbuf *sb)
47 {
48
49 return (sbused(sb) >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax);
50 }
51
52 static uint8_t
sbmget8(struct mbuf * m,int offset)53 sbmget8(struct mbuf *m, int offset)
54 {
55 struct mbuf *n = m->m_nextpkt;
56
57 while (m != NULL && offset >= m->m_len) {
58 offset -= m->m_len;
59 m = m->m_next;
60 if (m == NULL) {
61 m = n;
62 n = m->m_nextpkt;
63 }
64 }
65
66 return *(mtod(m, uint8_t *) + offset);
67 }
68
69 static int
so_hastls(struct socket * so,void * arg,int waitflag)70 so_hastls(struct socket *so, void *arg, int waitflag)
71 {
72 struct sockbuf *sb = &so->so_rcv;
73 int avail;
74 uint16_t reclen;
75
76 if ((sb->sb_state & SBS_CANTRCVMORE) || sbfull(sb))
77 return (SU_ISCONNECTED); /* can't wait any longer */
78
79 /*
80 * struct {
81 * ContentType type; - 1 byte, 0x16 handshake
82 * ProtocolVersion version; - 2 bytes (major, minor)
83 * uint16 length; - 2 bytes, NBO, 2^14 max
84 * opaque fragment[TLSPlaintext.length];
85 * } TLSPlaintext;
86 */
87
88 /* Did we get at least 5 bytes */
89 avail = sbavail(sb);
90 if (avail < 5)
91 return (SU_OK); /* nope */
92
93 /* Does this look like TLS handshake? */
94 if (sbmget8(sb->sb_mb, 0) != 0x16)
95 return (SU_ISCONNECTED); /* nope */
96
97 /* Did we get a complete TLS record? */
98 reclen = (uint16_t) sbmget8(sb->sb_mb, 3) << 8;
99 reclen |= (uint16_t) sbmget8(sb->sb_mb, 4);
100
101 if (reclen <= 16384 && avail < (int) 5 + reclen)
102 return (SU_OK); /* nope */
103
104 return (SU_ISCONNECTED);
105 }
106