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/*
* OpenConnect (SSL + DTLS) VPN client
*
* Copyright © 2008-2015 Intel Corporation.
*
* Author: David Woodhouse <dwmw2@infradead.org>
*
* 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 <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#include "openconnect-internal.h"
void destroy_esp_ciphers(struct esp *esp)
{
if (esp->cipher) {
gnutls_cipher_deinit(esp->cipher);
esp->cipher = NULL;
}
if (esp->hmac) {
gnutls_hmac_deinit(esp->hmac, NULL);
esp->hmac = NULL;
}
}
static int init_esp_cipher(struct openconnect_info *vpninfo, struct esp *esp,
gnutls_mac_algorithm_t macalg, gnutls_cipher_algorithm_t encalg)
{
gnutls_datum_t enc_key;
int err;
destroy_esp_ciphers(esp);
enc_key.size = gnutls_cipher_get_key_size(encalg);
enc_key.data = esp->enc_key;
err = gnutls_cipher_init(&esp->cipher, encalg, &enc_key, NULL);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to initialise ESP cipher: %s\n"),
gnutls_strerror(err));
return -EIO;
}
err = gnutls_hmac_init(&esp->hmac, macalg,
esp->hmac_key,
gnutls_hmac_get_len(macalg));
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to initialize ESP HMAC: %s\n"),
gnutls_strerror(err));
destroy_esp_ciphers(esp);
}
return 0;
}
int init_esp_ciphers(struct openconnect_info *vpninfo, struct esp *esp_out, struct esp *esp_in)
{
gnutls_mac_algorithm_t macalg;
gnutls_cipher_algorithm_t encalg;
int ret;
switch (vpninfo->esp_enc) {
case ENC_AES_128_CBC:
encalg = GNUTLS_CIPHER_AES_128_CBC;
break;
case ENC_AES_256_CBC:
encalg = GNUTLS_CIPHER_AES_256_CBC;
break;
default:
return -EINVAL;
}
switch (vpninfo->esp_hmac) {
case HMAC_MD5:
macalg = GNUTLS_MAC_MD5;
break;
case HMAC_SHA1:
macalg = GNUTLS_MAC_SHA1;
break;
case HMAC_SHA256:
macalg = GNUTLS_MAC_SHA256;
break;
default:
return -EINVAL;
}
ret = init_esp_cipher(vpninfo, esp_out, macalg, encalg);
if (ret)
return ret;
gnutls_cipher_set_iv(esp_out->cipher, esp_out->iv, sizeof(esp_out->iv));
ret = init_esp_cipher(vpninfo, esp_in, macalg, encalg);
if (ret) {
destroy_esp_ciphers(esp_out);
return ret;
}
return 0;
}
/* pkt->len shall be the *payload* length. Omitting the header and the 12-byte HMAC */
int decrypt_esp_packet(struct openconnect_info *vpninfo, struct esp *esp, struct pkt *pkt)
{
unsigned char hmac_buf[MAX_HMAC_SIZE];
int err;
err = gnutls_hmac(esp->hmac, &pkt->esp, sizeof(pkt->esp) + pkt->len);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to calculate HMAC for ESP packet: %s\n"),
gnutls_strerror(err));
return -EIO;
}
gnutls_hmac_output(esp->hmac, hmac_buf);
if (memcmp(hmac_buf, pkt->data + pkt->len, vpninfo->hmac_out_len)) {
vpn_progress(vpninfo, PRG_DEBUG,
_("Received ESP packet with invalid HMAC\n"));
return -EINVAL;
}
if (verify_packet_seqno(vpninfo, esp, ntohl(pkt->esp.seq)))
return -EINVAL;
gnutls_cipher_set_iv(esp->cipher, pkt->esp.iv, sizeof(pkt->esp.iv));
err = gnutls_cipher_decrypt(esp->cipher, pkt->data, pkt->len);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Decrypting ESP packet failed: %s\n"),
gnutls_strerror(err));
return -EINVAL;
}
return 0;
}
int encrypt_esp_packet(struct openconnect_info *vpninfo, struct pkt *pkt, int crypt_len)
{
const int blksize = 16;
int err;
err = gnutls_cipher_encrypt(vpninfo->esp_out.cipher, pkt->data, crypt_len);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to encrypt ESP packet: %s\n"),
gnutls_strerror(err));
return -EIO;
}
err = gnutls_hmac(vpninfo->esp_out.hmac, &pkt->esp, sizeof(pkt->esp) + crypt_len);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to calculate HMAC for ESP packet: %s\n"),
gnutls_strerror(err));
return -EIO;
}
gnutls_hmac_output(vpninfo->esp_out.hmac, pkt->data + crypt_len);
memcpy(vpninfo->esp_out.iv, pkt->data + crypt_len, blksize);
gnutls_cipher_encrypt(vpninfo->esp_out.cipher, vpninfo->esp_out.iv, blksize);
return 0;
}
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