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/*
* OpenVPN -- An application to securely tunnel IP networks
* over a single TCP/UDP port, with support for SSL/TLS-based
* session authentication and key exchange,
* packet encryption, packet authentication, and
* packet compression.
*
* Copyright (C) 2002-2021 OpenVPN Inc <sales@openvpn.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif
#include "syshead.h"
#include "proto.h"
#include "error.h"
#include "memdbg.h"
/*
* If raw tunnel packet is IPv<X>, return true and increment
* buffer offset to start of IP header.
*/
static bool
is_ipv_X(int tunnel_type, struct buffer *buf, int ip_ver)
{
int offset;
uint16_t proto;
const struct openvpn_iphdr *ih;
verify_align_4(buf);
if (tunnel_type == DEV_TYPE_TUN)
{
if (BLEN(buf) < sizeof(struct openvpn_iphdr))
{
return false;
}
offset = 0;
}
else if (tunnel_type == DEV_TYPE_TAP)
{
const struct openvpn_ethhdr *eh;
if (BLEN(buf) < (sizeof(struct openvpn_ethhdr)
+ sizeof(struct openvpn_iphdr)))
{
return false;
}
eh = (const struct openvpn_ethhdr *)BPTR(buf);
/* start by assuming this is a standard Eth fram */
proto = eh->proto;
offset = sizeof(struct openvpn_ethhdr);
/* if this is a 802.1q frame, parse the header using the according
* format
*/
if (proto == htons(OPENVPN_ETH_P_8021Q))
{
const struct openvpn_8021qhdr *evh;
if (BLEN(buf) < (sizeof(struct openvpn_ethhdr)
+ sizeof(struct openvpn_iphdr)))
{
return false;
}
evh = (const struct openvpn_8021qhdr *)BPTR(buf);
proto = evh->proto;
offset = sizeof(struct openvpn_8021qhdr);
}
if (ntohs(proto) != (ip_ver == 6 ? OPENVPN_ETH_P_IPV6 : OPENVPN_ETH_P_IPV4))
{
return false;
}
}
else
{
return false;
}
ih = (const struct openvpn_iphdr *)(BPTR(buf) + offset);
/* IP version is stored in the same bits for IPv4 or IPv6 header */
if (OPENVPN_IPH_GET_VER(ih->version_len) == ip_ver)
{
return buf_advance(buf, offset);
}
else
{
return false;
}
}
bool
is_ipv4(int tunnel_type, struct buffer *buf)
{
return is_ipv_X( tunnel_type, buf, 4 );
}
bool
is_ipv6(int tunnel_type, struct buffer *buf)
{
return is_ipv_X( tunnel_type, buf, 6 );
}
uint16_t
ip_checksum(const sa_family_t af, const uint8_t *payload, const int len_payload,
const uint8_t *src_addr, const uint8_t *dest_addr, const int proto)
{
uint32_t sum = 0;
int addr_len = (af == AF_INET) ? 4 : 16;
/*
* make 16 bit words out of every two adjacent 8 bit words and */
/* calculate the sum of all 16 bit words
*/
for (int i = 0; i < len_payload; i += 2)
{
sum += (uint16_t)(((payload[i] << 8) & 0xFF00)
+((i + 1 < len_payload) ? (payload[i + 1] & 0xFF) : 0));
}
/*
* add the pseudo header which contains the IP source and destination
* addresses
*/
for (int i = 0; i < addr_len; i += 2)
{
sum += (uint16_t)((src_addr[i] << 8) & 0xFF00) + (src_addr[i + 1] & 0xFF);
}
for (int i = 0; i < addr_len; i += 2)
{
sum += (uint16_t)((dest_addr[i] << 8) & 0xFF00) + (dest_addr[i + 1] & 0xFF);
}
/* the length of the payload */
sum += (uint16_t)len_payload;
/* The next header or proto field*/
sum += (uint16_t)proto;
/*
* keep only the last 16 bits of the 32 bit calculated sum and add
* the carries
*/
while (sum >> 16)
{
sum = (sum & 0xFFFF) + (sum >> 16);
}
/* Take the one's complement of sum */
return ((uint16_t) ~sum);
}
#ifdef PACKET_TRUNCATION_CHECK
void
ipv4_packet_size_verify(const uint8_t *data,
const int size,
const int tunnel_type,
const char *prefix,
counter_type *errors)
{
if (size > 0)
{
struct buffer buf;
buf_set_read(&buf, data, size);
if (is_ipv4(tunnel_type, &buf))
{
const struct openvpn_iphdr *pip;
int hlen;
int totlen;
const char *msgstr = "PACKET SIZE INFO";
unsigned int msglevel = D_PACKET_TRUNC_DEBUG;
if (BLEN(&buf) < (int) sizeof(struct openvpn_iphdr))
{
return;
}
verify_align_4(&buf);
pip = (struct openvpn_iphdr *) BPTR(&buf);
hlen = OPENVPN_IPH_GET_LEN(pip->version_len);
totlen = ntohs(pip->tot_len);
if (BLEN(&buf) != totlen)
{
msgstr = "PACKET TRUNCATION ERROR";
msglevel = D_PACKET_TRUNC_ERR;
if (errors)
{
++(*errors);
}
}
msg(msglevel, "%s %s: size=%d totlen=%d hlen=%d errcount=" counter_format,
msgstr,
prefix,
BLEN(&buf),
totlen,
hlen,
errors ? *errors : (counter_type)0);
}
}
}
#endif /* ifdef PACKET_TRUNCATION_CHECK */
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