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esp.c
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esp.c
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/*
* OpenConnect (SSL + DTLS) VPN client
*
* Copyright © 2008-2015 Intel Corporation.
*
* Author: David Woodhouse <[email protected]>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2.1, 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
* Lesser General Public License for more details.
*/
#include <config.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#ifdef __FreeBSD__
#include <sys/types.h>
#include <netinet/in.h>
#endif
#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#include "win32-ipicmp.h"
#else
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#endif
#include "openconnect-internal.h"
#include "lzo.h"
int print_esp_keys(struct openconnect_info *vpninfo, const char *name, struct esp *esp)
{
int i;
const char *enctype, *mactype;
char enckey[256], mackey[256];
switch(vpninfo->esp_enc) {
case 0x02:
enctype = "AES-128-CBC (RFC3602)";
break;
case 0x05:
enctype = "AES-256-CBC (RFC3602)";
break;
default:
return -EINVAL;
}
switch(vpninfo->esp_hmac) {
case 0x01:
mactype = "HMAC-MD5-96 (RFC2403)";
break;
case 0x02:
mactype = "HMAC-SHA-1-96 (RFC2404)";
break;
default:
return -EINVAL;
}
for (i = 0; i < vpninfo->enc_key_len; i++)
sprintf(enckey + (2 * i), "%02x", esp->enc_key[i]);
for (i = 0; i < vpninfo->hmac_key_len; i++)
sprintf(mackey + (2 * i), "%02x", esp->hmac_key[i]);
vpn_progress(vpninfo, PRG_TRACE,
_("Parameters for %s ESP: SPI 0x%08x\n"),
name, (unsigned)ntohl(esp->spi));
vpn_progress(vpninfo, PRG_TRACE,
_("ESP encryption type %s key 0x%s\n"),
enctype, enckey);
vpn_progress(vpninfo, PRG_TRACE,
_("ESP authentication type %s key 0x%s\n"),
mactype, mackey);
return 0;
}
int esp_send_probes(struct openconnect_info *vpninfo)
{
struct pkt *pkt;
int pktlen;
if (vpninfo->dtls_fd == -1) {
int fd = udp_connect(vpninfo);
if (fd < 0)
return fd;
/* We are not connected until we get an ESP packet back */
vpninfo->dtls_state = DTLS_SLEEPING;
vpninfo->dtls_fd = fd;
monitor_fd_new(vpninfo, dtls);
monitor_read_fd(vpninfo, dtls);
monitor_except_fd(vpninfo, dtls);
}
pkt = malloc(sizeof(*pkt) + 1 + vpninfo->pkt_trailer);
if (!pkt)
return -ENOMEM;
pkt->len = 1;
pkt->data[0] = 0;
pktlen = encrypt_esp_packet(vpninfo, pkt);
if (pktlen >= 0)
send(vpninfo->dtls_fd, (void *)&pkt->esp, pktlen, 0);
pkt->len = 1;
pkt->data[0] = 0;
pktlen = encrypt_esp_packet(vpninfo, pkt);
if (pktlen >= 0)
send(vpninfo->dtls_fd, (void *)&pkt->esp, pktlen, 0);
free(pkt);
vpninfo->dtls_times.last_tx = time(&vpninfo->new_dtls_started);
return 0;
};
static uint16_t csum(uint16_t *buf, int nwords)
{
uint32_t sum = 0;
for(sum=0; nwords>0; nwords--)
sum += ntohs(*buf++);
sum = (sum >> 16) + (sum &0xffff);
sum += (sum >> 16);
return htons((uint16_t)(~sum));
}
int esp_send_probes_gp(struct openconnect_info *vpninfo)
{
/* The GlobalProtect VPN initiates and maintains the ESP connection
* using specially-crafted ICMP ("ping") packets.
*
* 1) These ping packets have a special magic payload. It must
* include at least the 16 bytes below. The Windows client actually
* sends this 56-byte version, but the remaining bytes don't
* seem to matter:
*
* "monitor\x00\x00pan ha 0123456789:;<=>? !\"#$%&\'()*+,-./\x10\x11\x12\x13\x14\x15\x16\x18";
*
* 2) The ping packets are addressed to the IP supplied in the
* config XML as as <gw-address>. In most cases, this is the
* same as the *external* IP address of the VPN gateway
* (vpninfo->ip_info.gateway_addr), but in some cases it is a
* separate address.
*
* Don't blame me. I didn't design this.
*/
static char magic[16] = "monitor\x00\x00pan ha ";
int pktlen, seq;
struct pkt *pkt = malloc(sizeof(*pkt) + sizeof(struct ip) + ICMP_MINLEN + sizeof(magic) + vpninfo->pkt_trailer);
struct ip *iph = (void *)pkt->data;
struct icmp *icmph = (void *)(pkt->data + sizeof(*iph));
char *pmagic = (void *)(pkt->data + sizeof(*iph) + ICMP_MINLEN);
if (!pkt)
return -ENOMEM;
if (vpninfo->dtls_fd == -1) {
int fd = udp_connect(vpninfo);
if (fd < 0)
return fd;
/* We are not connected until we get an ESP packet back */
vpninfo->dtls_state = DTLS_SLEEPING;
vpninfo->dtls_fd = fd;
monitor_fd_new(vpninfo, dtls);
monitor_read_fd(vpninfo, dtls);
monitor_except_fd(vpninfo, dtls);
}
for (seq=1; seq <= (vpninfo->dtls_state==DTLS_CONNECTED ? 1 : 3); seq++) {
memset(pkt, 0, sizeof(*pkt) + sizeof(*iph) + ICMP_MINLEN + sizeof(magic));
pkt->len = sizeof(struct ip) + ICMP_MINLEN + sizeof(magic);
/* IP Header */
iph->ip_hl = 5;
iph->ip_v = 4;
iph->ip_len = htons(sizeof(*iph) + ICMP_MINLEN + sizeof(magic));
iph->ip_id = htons(0x4747); /* what the Windows client uses */
iph->ip_off = htons(IP_DF); /* don't fragment, frag offset = 0 */
iph->ip_ttl = 64; /* hops */
iph->ip_p = 1; /* ICMP */
iph->ip_src.s_addr = inet_addr(vpninfo->ip_info.addr);
iph->ip_dst.s_addr = vpninfo->esp_magic;
iph->ip_sum = csum((uint16_t *)iph, sizeof(*iph)/2);
/* ICMP echo request */
icmph->icmp_type = ICMP_ECHO;
icmph->icmp_hun.ih_idseq.icd_id = htons(0x4747);
icmph->icmp_hun.ih_idseq.icd_seq = htons(seq);
memcpy(pmagic, magic, sizeof(magic)); /* required to get gateway to respond */
icmph->icmp_cksum = csum((uint16_t *)icmph, (ICMP_MINLEN+sizeof(magic))/2);
pktlen = encrypt_esp_packet(vpninfo, pkt);
if (pktlen >= 0)
send(vpninfo->dtls_fd, (void *)&pkt->esp, pktlen, 0);
}
free(pkt);
vpninfo->dtls_times.last_tx = time(&vpninfo->new_dtls_started);
return 0;
}
int esp_catch_probe(struct openconnect_info *vpninfo, struct pkt *pkt)
{
return (pkt->len == 1 && pkt->data[0] == 0);
}
int esp_catch_probe_gp(struct openconnect_info *vpninfo, struct pkt *pkt)
{
struct ip *iph = (void *)(pkt->data);
return ( pkt->len >= 21
&& iph->ip_p==1 /* IPv4 protocol field == ICMP */
&& iph->ip_src.s_addr == vpninfo->esp_magic /* source == magic address */
&& pkt->len >= (iph->ip_hl<<2)+1 /* No short-packet segfaults */
&& pkt->data[iph->ip_hl<<2]==0 /* ICMP reply */ );
}
int esp_setup(struct openconnect_info *vpninfo, int dtls_attempt_period)
{
if (vpninfo->dtls_state == DTLS_DISABLED ||
vpninfo->dtls_state == DTLS_NOSECRET)
return -EINVAL;
if (vpninfo->esp_ssl_fallback)
vpninfo->dtls_times.dpd = vpninfo->esp_ssl_fallback;
else
vpninfo->dtls_times.dpd = dtls_attempt_period;
vpninfo->dtls_attempt_period = dtls_attempt_period;
print_esp_keys(vpninfo, _("incoming"), &vpninfo->esp_in[vpninfo->current_esp_in]);
print_esp_keys(vpninfo, _("outgoing"), &vpninfo->esp_out);
vpn_progress(vpninfo, PRG_DEBUG, _("Send ESP probes\n"));
if (vpninfo->proto->udp_send_probes)
vpninfo->proto->udp_send_probes(vpninfo);
return 0;
}
int esp_mainloop(struct openconnect_info *vpninfo, int *timeout)
{
struct esp *esp = &vpninfo->esp_in[vpninfo->current_esp_in];
struct esp *old_esp = &vpninfo->esp_in[vpninfo->current_esp_in ^ 1];
struct pkt *this;
int work_done = 0;
int ret;
if (vpninfo->dtls_state == DTLS_SLEEPING) {
if (ka_check_deadline(timeout, time(NULL), vpninfo->new_dtls_started + vpninfo->dtls_attempt_period)
|| vpninfo->dtls_need_reconnect) {
vpn_progress(vpninfo, PRG_DEBUG, _("Send ESP probes\n"));
if (vpninfo->proto->udp_send_probes)
vpninfo->proto->udp_send_probes(vpninfo);
}
}
if (vpninfo->dtls_fd == -1)
return 0;
while (1) {
int len = vpninfo->ip_info.mtu + vpninfo->pkt_trailer;
int i;
struct pkt *pkt;
if (!vpninfo->dtls_pkt) {
vpninfo->dtls_pkt = malloc(sizeof(struct pkt) + len);
if (!vpninfo->dtls_pkt) {
vpn_progress(vpninfo, PRG_ERR, _("Allocation failed\n"));
break;
}
}
pkt = vpninfo->dtls_pkt;
len = recv(vpninfo->dtls_fd, (void *)&pkt->esp, len + sizeof(pkt->esp), 0);
if (len <= 0)
break;
vpn_progress(vpninfo, PRG_TRACE, _("Received ESP packet of %d bytes\n"),
len);
work_done = 1;
if (len <= sizeof(pkt->esp) + 12)
continue;
len -= sizeof(pkt->esp) + 12;
pkt->len = len;
if (pkt->esp.spi == esp->spi) {
if (decrypt_esp_packet(vpninfo, esp, pkt))
continue;
} else if (pkt->esp.spi == old_esp->spi &&
ntohl(pkt->esp.seq) + esp->seq < vpninfo->old_esp_maxseq) {
vpn_progress(vpninfo, PRG_TRACE,
_("Received ESP packet from old SPI 0x%x, seq %u\n"),
(unsigned)ntohl(old_esp->spi), (unsigned)ntohl(pkt->esp.seq));
if (decrypt_esp_packet(vpninfo, old_esp, pkt))
continue;
} else {
vpn_progress(vpninfo, PRG_DEBUG,
_("Received ESP packet with invalid SPI 0x%08x\n"),
(unsigned)ntohl(pkt->esp.spi));
continue;
}
if (pkt->data[len - 1] != 0x04 && pkt->data[len - 1] != 0x29 &&
pkt->data[len - 1] != 0x05) {
vpn_progress(vpninfo, PRG_ERR,
_("Received ESP packet with unrecognised payload type %02x\n"),
pkt->data[len-1]);
continue;
}
if (len <= 2 + pkt->data[len - 2]) {
vpn_progress(vpninfo, PRG_ERR,
_("Invalid padding length %02x in ESP\n"),
pkt->data[len - 2]);
continue;
}
pkt->len = len - 2 - pkt->data[len - 2];
for (i = 0 ; i < pkt->data[len - 2]; i++) {
if (pkt->data[pkt->len + i] != i + 1)
break; /* We can't just 'continue' here because it
* would only break out of this 'for' loop */
}
if (i != pkt->data[len - 2]) {
vpn_progress(vpninfo, PRG_ERR,
_("Invalid padding bytes in ESP\n"));
continue; /* We can here, though */
}
vpninfo->dtls_times.last_rx = time(NULL);
if (vpninfo->proto->udp_catch_probe) {
if (vpninfo->proto->udp_catch_probe(vpninfo, pkt)) {
if (vpninfo->dtls_state == DTLS_SLEEPING) {
vpn_progress(vpninfo, PRG_INFO,
_("ESP session established with server\n"));
queue_esp_control(vpninfo, 1);
vpninfo->dtls_state = DTLS_CONNECTING;
}
continue;
}
}
if (pkt->data[len - 1] == 0x05) {
struct pkt *newpkt = malloc(sizeof(*pkt) + vpninfo->ip_info.mtu + vpninfo->pkt_trailer);
int newlen = vpninfo->ip_info.mtu;
if (!newpkt) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to allocate memory to decrypt ESP packet\n"));
continue;
}
if (av_lzo1x_decode(newpkt->data, &newlen,
pkt->data, &pkt->len) || pkt->len) {
vpn_progress(vpninfo, PRG_ERR,
_("LZO decompression of ESP packet failed\n"));
free(newpkt);
continue;
}
newpkt->len = vpninfo->ip_info.mtu - newlen;
vpn_progress(vpninfo, PRG_TRACE,
_("LZO decompressed %d bytes into %d\n"),
len - 2 - pkt->data[len-2], newpkt->len);
queue_packet(&vpninfo->incoming_queue, newpkt);
} else {
queue_packet(&vpninfo->incoming_queue, pkt);
vpninfo->dtls_pkt = NULL;
}
}
if (vpninfo->dtls_state != DTLS_CONNECTED)
return 0;
switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
case KA_REKEY:
vpn_progress(vpninfo, PRG_ERR, _("Rekey not implemented for ESP\n"));
break;
case KA_DPD_DEAD:
vpn_progress(vpninfo, PRG_ERR, _("ESP detected dead peer\n"));
queue_esp_control(vpninfo, 0);
esp_close(vpninfo);
if (vpninfo->proto->udp_send_probes)
vpninfo->proto->udp_send_probes(vpninfo);
return 1;
case KA_DPD:
vpn_progress(vpninfo, PRG_DEBUG, _("Send ESP probes for DPD\n"));
if (vpninfo->proto->udp_send_probes)
vpninfo->proto->udp_send_probes(vpninfo);
work_done = 1;
break;
case KA_KEEPALIVE:
vpn_progress(vpninfo, PRG_ERR, _("Keepalive not implemented for ESP\n"));
break;
case KA_NONE:
break;
}
unmonitor_write_fd(vpninfo, dtls);
while ((this = dequeue_packet(&vpninfo->outgoing_queue))) {
int len;
len = encrypt_esp_packet(vpninfo, this);
if (len > 0) {
ret = send(vpninfo->dtls_fd, (void *)&this->esp, len, 0);
if (ret < 0) {
/* Not that this is likely to happen with UDP, but... */
if (errno == ENOBUFS || errno == EAGAIN || errno == EWOULDBLOCK) {
monitor_write_fd(vpninfo, dtls);
/* XXX: Keep the packet somewhere? */
free(this);
return work_done;
} else {
/* A real error in sending. Fall back to TCP? */
vpn_progress(vpninfo, PRG_ERR,
_("Failed to send ESP packet: %s\n"),
strerror(errno));
}
} else {
vpninfo->dtls_times.last_tx = time(NULL);
vpn_progress(vpninfo, PRG_TRACE, _("Sent ESP packet of %d bytes\n"),
len);
}
} else {
/* XXX: Fall back to TCP transport? */
}
free(this);
work_done = 1;
}
return work_done;
}
void esp_close(struct openconnect_info *vpninfo)
{
/* We close and reopen the socket in case we roamed and our
local IP address has changed. */
if (vpninfo->dtls_fd != -1) {
closesocket(vpninfo->dtls_fd);
unmonitor_read_fd(vpninfo, dtls);
unmonitor_write_fd(vpninfo, dtls);
unmonitor_except_fd(vpninfo, dtls);
vpninfo->dtls_fd = -1;
}
if (vpninfo->dtls_state > DTLS_DISABLED)
vpninfo->dtls_state = DTLS_SLEEPING;
}
void esp_close_secret(struct openconnect_info *vpninfo)
{
esp_close(vpninfo);
if (vpninfo->dtls_state > DTLS_DISABLED)
vpninfo->dtls_state = DTLS_NOSECRET;
}
void esp_shutdown(struct openconnect_info *vpninfo)
{
destroy_esp_ciphers(&vpninfo->esp_in[0]);
destroy_esp_ciphers(&vpninfo->esp_in[1]);
destroy_esp_ciphers(&vpninfo->esp_out);
esp_close(vpninfo);
}