/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2003 Bruce M. Simpson <bms@spc.org>
* Copyright (c) 2016 Andrey V. Elsukov <ae@FreeBSD.org>
*
* 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.
*/
/* TCP MD5 Signature Option (RFC2385) */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/lock.h>
#include <sys/md5.h>
#include <sys/rmlock.h>
#include <sys/socket.h>
#include <sys/sockopt.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/protosw.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_var.h>
#include <net/vnet.h>
#include <netipsec/ipsec.h>
#include <netipsec/ipsec_support.h>
#include <netipsec/xform.h>
#ifdef INET6
#include <netinet/ip6.h>
#include <netipsec/ipsec6.h>
#endif
#include <netipsec/key.h>
#include <netipsec/key_debug.h>
#define TCP_SIGLEN 16 /* length of computed digest in bytes */
#define TCP_KEYLEN_MIN 1 /* minimum length of TCP-MD5 key */
#define TCP_KEYLEN_MAX 80 /* maximum length of TCP-MD5 key */
static int
tcp_ipsec_pcbctl(struct inpcb *inp, struct sockopt *sopt)
{
struct tcpcb *tp;
int error, optval;
if (sopt->sopt_name != TCP_MD5SIG) {
return (ENOPROTOOPT);
}
if (sopt->sopt_dir == SOPT_GET) {
INP_RLOCK(inp);
if (inp->inp_flags & INP_DROPPED) {
INP_RUNLOCK(inp);
return (ECONNRESET);
}
tp = intotcpcb(inp);
optval = (tp->t_flags & TF_SIGNATURE) ? 1 : 0;
INP_RUNLOCK(inp);
/* On success return with released INP_WLOCK */
return (sooptcopyout(sopt, &optval, sizeof(optval)));
}
error = sooptcopyin(sopt, &optval, sizeof(optval), sizeof(optval));
if (error != 0)
return (error);
/* INP_WLOCK_RECHECK */
INP_WLOCK(inp);
if (inp->inp_flags & INP_DROPPED) {
INP_WUNLOCK(inp);
return (ECONNRESET);
}
tp = intotcpcb(inp);
if (optval > 0)
tp->t_flags |= TF_SIGNATURE;
else
tp->t_flags &= ~TF_SIGNATURE;
INP_WUNLOCK(inp);
return (error);
}
/*
* Callback function invoked by m_apply() to digest TCP segment data
* contained within an mbuf chain.
*/
static int
tcp_signature_apply(void *fstate, void *data, u_int len)
{
MD5Update(fstate, (u_char *)data, len);
return (0);
}
#ifdef INET
static int
ip_pseudo_compute(struct mbuf *m, MD5_CTX *ctx)
{
struct ippseudo ipp;
struct ip *ip;
ip = mtod(m, struct ip *);
ipp.ippseudo_src.s_addr = ip->ip_src.s_addr;
ipp.ippseudo_dst.s_addr = ip->ip_dst.s_addr;
ipp.ippseudo_p = IPPROTO_TCP;
ipp.ippseudo_pad = 0;
ipp.ippseudo_len = htons(m->m_pkthdr.len - (ip->ip_hl << 2));
MD5Update(ctx, (char *)&ipp, sizeof(ipp));
return (ip->ip_hl << 2);
}
#endif
#ifdef INET6
static int
ip6_pseudo_compute(struct mbuf *m, MD5_CTX *ctx)
{
struct ip6_pseudo {
struct in6_addr src, dst;
uint32_t len;
uint32_t nxt;
} ip6p __aligned(4);
struct ip6_hdr *ip6;
ip6 = mtod(m, struct ip6_hdr *);
ip6p.src = ip6->ip6_src;
ip6p.dst = ip6->ip6_dst;
ip6p.len = htonl(m->m_pkthdr.len - sizeof(*ip6)); /* XXX: ext headers */
ip6p.nxt = htonl(IPPROTO_TCP);
MD5Update(ctx, (char *)&ip6p, sizeof(ip6p));
return (sizeof(*ip6));
}
#endif
static int
tcp_signature_compute(struct mbuf *m, struct tcphdr *th,
struct secasvar *sav, u_char *buf)
{
MD5_CTX ctx;
int len;
u_short csum;
MD5Init(&ctx);
/* Step 1: Update MD5 hash with IP(v6) pseudo-header. */
switch (sav->sah->saidx.dst.sa.sa_family) {
#ifdef INET
case AF_INET:
len = ip_pseudo_compute(m, &ctx);
break;
#endif
#ifdef INET6
case AF_INET6:
len = ip6_pseudo_compute(m, &ctx);
break;
#endif
default:
return (EAFNOSUPPORT);
}
/*
* Step 2: Update MD5 hash with TCP header, excluding options.
* The TCP checksum must be set to zero.
*/
csum = th->th_sum;
th->th_sum = 0;
MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
th->th_sum = csum;
/*
* Step 3: Update MD5 hash with TCP segment data.
* Use m_apply() to avoid an early m_pullup().
*/
len += (th->th_off << 2);
if (m->m_pkthdr.len - len > 0)
m_apply(m, len, m->m_pkthdr.len - len,
tcp_signature_apply, &ctx);
/*
* Step 4: Update MD5 hash with shared secret.
*/
MD5Update(&ctx, sav->key_auth->key_data, _KEYLEN(sav->key_auth));
MD5Final(buf, &ctx);
key_sa_recordxfer(sav, m);
return (0);
}
static void
setsockaddrs(const struct mbuf *m, union sockaddr_union *src,
union sockaddr_union *dst)
{
struct ip *ip;
IPSEC_ASSERT(m->m_len >= sizeof(*ip), ("unexpected mbuf len"));
ip = mtod(m, struct ip *);
switch (ip->ip_v) {
#ifdef INET
case IPVERSION:
ipsec4_setsockaddrs(m, src, dst);
break;
#endif
#ifdef INET6
case (IPV6_VERSION >> 4):
ipsec6_setsockaddrs(m, src, dst);
break;
#endif
default:
bzero(src, sizeof(*src));
bzero(dst, sizeof(*dst));
}
}
/*
* Compute TCP-MD5 hash of an *INBOUND* TCP segment.
* Parameters:
* m pointer to head of mbuf chain
* th pointer to TCP header
* buf pointer to storage for computed MD5 digest
*
* Return 0 if successful, otherwise return error code.
*/
static int
tcp_ipsec_input(struct mbuf *m, struct tcphdr *th, u_char *buf)
{
char tmpdigest[TCP_SIGLEN];
struct secasindex saidx;
struct secasvar *sav;
setsockaddrs(m, &saidx.src, &saidx.dst);
saidx.proto = IPPROTO_TCP;
saidx.mode = IPSEC_MODE_TCPMD5;
saidx.reqid = 0;
sav = key_allocsa_tcpmd5(&saidx);
if (sav == NULL) {
KMOD_TCPSTAT_INC(tcps_sig_err_buildsig);
return (ENOENT);
}
if (buf == NULL) {
key_freesav(&sav);
KMOD_TCPSTAT_INC(tcps_sig_err_nosigopt);
return (EACCES);
}
/*
* tcp_input() operates with TCP header fields in host
* byte order. We expect them in network byte order.
*/
tcp_fields_to_net(th);
tcp_signature_compute(m, th, sav, tmpdigest);
tcp_fields_to_host(th);
key_freesav(&sav);
if (bcmp(buf, tmpdigest, TCP_SIGLEN) != 0) {
KMOD_TCPSTAT_INC(tcps_sig_rcvbadsig);
return (EACCES);
}
KMOD_TCPSTAT_INC(tcps_sig_rcvgoodsig);
return (0);
}
/*
* Compute TCP-MD5 hash of an *OUTBOUND* TCP segment.
* Parameters:
* m pointer to head of mbuf chain
* th pointer to TCP header
* buf pointer to storage for computed MD5 digest
*
* Return 0 if successful, otherwise return error code.
*/
static int
tcp_ipsec_output(struct mbuf *m, struct tcphdr *th, u_char *buf)
{
struct secasindex saidx;
struct secasvar *sav;
setsockaddrs(m, &saidx.src, &saidx.dst);
saidx.proto = IPPROTO_TCP;
saidx.mode = IPSEC_MODE_TCPMD5;
saidx.reqid = 0;
sav = key_allocsa_tcpmd5(&saidx);
if (sav == NULL) {
KMOD_TCPSTAT_INC(tcps_sig_err_buildsig);
return (ENOENT);
}
tcp_signature_compute(m, th, sav, buf);
key_freesav(&sav);
return (0);
}
/*
* Initialize a TCP-MD5 SA. Called when the SA is being set up.
*
* We don't need to set up the tdb prefixed fields, as we don't use the
* opencrypto code; we just perform a key length check.
*
* XXX: Currently we have used single 'magic' SPI and need to still
* support this.
*
* This allows per-host granularity without affecting the userland
* interface, which is a simple socket option toggle switch,
* TCP_SIGNATURE_ENABLE.
*
* To allow per-service granularity requires that we have a means
* of mapping port to SPI. The mandated way of doing this is to
* use SPD entries to specify packet flows which get the TCP-MD5
* treatment, however the code to do this is currently unstable
* and unsuitable for production use.
*
* Therefore we use this compromise in the meantime.
*/
static int
tcpsignature_init(struct secasvar *sav, struct xformsw *xsp)
{
int keylen;
if (sav->alg_auth != SADB_X_AALG_TCP_MD5) {
DPRINTF(("%s: unsupported authentication algorithm %u\n",
__func__, sav->alg_auth));
return (EINVAL);
}
if (sav->key_auth == NULL) {
DPRINTF(("%s: no authentication key present\n", __func__));
return (EINVAL);
}
keylen = _KEYLEN(sav->key_auth);
if ((keylen < TCP_KEYLEN_MIN) || (keylen > TCP_KEYLEN_MAX)) {
DPRINTF(("%s: invalid key length %u\n", __func__, keylen));
return (EINVAL);
}
sav->tdb_xform = xsp;
return (0);
}
/*
* Called when the SA is deleted.
*/
static void
tcpsignature_cleanup(struct secasvar *sav)
{
}
static struct xformsw tcpsignature_xformsw = {
.xf_type = XF_TCPSIGNATURE,
.xf_name = "TCP-MD5",
.xf_init = tcpsignature_init,
.xf_cleanup = tcpsignature_cleanup,
};
static const struct tcpmd5_methods tcpmd5_methods = {
.input = tcp_ipsec_input,
.output = tcp_ipsec_output,
.pcbctl = tcp_ipsec_pcbctl,
};
#ifndef KLD_MODULE
/* TCP-MD5 support is build in the kernel */
static const struct tcpmd5_support tcpmd5_ipsec = {
.enabled = IPSEC_MODULE_ENABLED,
.methods = &tcpmd5_methods
};
const struct tcpmd5_support * const tcp_ipsec_support = &tcpmd5_ipsec;
#endif /* !KLD_MODULE */
static int
tcpmd5_modevent(module_t mod, int type, void *data)
{
switch (type) {
case MOD_LOAD:
xform_attach(&tcpsignature_xformsw);
#ifdef KLD_MODULE
tcpmd5_support_enable(&tcpmd5_methods);
#endif
break;
case MOD_UNLOAD:
#ifdef KLD_MODULE
tcpmd5_support_disable();
#endif
xform_detach(&tcpsignature_xformsw);
break;
default:
return (EOPNOTSUPP);
}
return (0);
}
static moduledata_t tcpmd5_mod = {
"tcpmd5",
tcpmd5_modevent,
0
};
DECLARE_MODULE(tcpmd5, tcpmd5_mod, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY);
MODULE_VERSION(tcpmd5, 1);
#ifdef KLD_MODULE
MODULE_DEPEND(tcpmd5, ipsec_support, 1, 1, 1);
#endif
