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openssl-esp.c
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openssl-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 "openconnect-internal.h"
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#if OPENSSL_VERSION_NUMBER < 0x10100000L
#define EVP_CIPHER_CTX_free(c) do { \
EVP_CIPHER_CTX_cleanup(c); \
free(c); } while (0)
#define HMAC_CTX_free(c) do { \
HMAC_CTX_cleanup(c); \
free(c); } while (0)
static inline HMAC_CTX *HMAC_CTX_new(void)
{
HMAC_CTX *ret = malloc(sizeof(*ret));
if (ret)
HMAC_CTX_init(ret);
return ret;
}
#endif
void destroy_esp_ciphers(struct esp *esp)
{
if (esp->cipher) {
EVP_CIPHER_CTX_free(esp->cipher);
esp->cipher = NULL;
}
if (esp->hmac) {
HMAC_CTX_free(esp->hmac);
esp->hmac = NULL;
}
}
static int init_esp_cipher(struct openconnect_info *vpninfo, struct esp *esp,
const EVP_MD *macalg, const EVP_CIPHER *encalg, int decrypt)
{
int ret;
destroy_esp_ciphers(esp);
#if OPENSSL_VERSION_NUMBER < 0x10100000L
esp->cipher = malloc(sizeof(*esp->cipher));
if (!esp->cipher)
return -ENOMEM;
EVP_CIPHER_CTX_init(esp->cipher);
#else
esp->cipher = EVP_CIPHER_CTX_new();
if (!esp->cipher)
return -ENOMEM;
#endif
if (decrypt)
ret = EVP_DecryptInit_ex(esp->cipher, encalg, NULL, esp->enc_key, NULL);
else {
ret = EVP_EncryptInit_ex(esp->cipher, encalg, NULL, esp->enc_key, esp->iv);
}
if (!ret) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to initialise ESP cipher:\n"));
openconnect_report_ssl_errors(vpninfo);
return -EIO;
}
EVP_CIPHER_CTX_set_padding(esp->cipher, 0);
esp->hmac = HMAC_CTX_new();
if (!esp->hmac) {
destroy_esp_ciphers(esp);
return -ENOMEM;
}
if (!HMAC_Init_ex(esp->hmac, esp->hmac_key,
EVP_MD_size(macalg), macalg, NULL)) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to initialize ESP HMAC\n"));
openconnect_report_ssl_errors(vpninfo);
destroy_esp_ciphers(esp);
}
return 0;
}
int init_esp_ciphers(struct openconnect_info *vpninfo, struct esp *esp_out, struct esp *esp_in)
{
const EVP_CIPHER *encalg;
const EVP_MD *macalg;
int ret;
switch (vpninfo->esp_enc) {
case ENC_AES_128_CBC:
encalg = EVP_aes_128_cbc();
break;
case ENC_AES_256_CBC:
encalg = EVP_aes_256_cbc();
break;
default:
return -EINVAL;
}
switch (vpninfo->esp_hmac) {
case HMAC_MD5:
macalg = EVP_md5();
break;
case HMAC_SHA1:
macalg = EVP_sha1();
break;
case HMAC_SHA256:
macalg = EVP_sha256();
break;
default:
return -EINVAL;
}
ret = init_esp_cipher(vpninfo, &vpninfo->esp_out, macalg, encalg, 0);
if (ret)
return ret;
ret = init_esp_cipher(vpninfo, esp_in, macalg, encalg, 1);
if (ret) {
destroy_esp_ciphers(&vpninfo->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];
unsigned int hmac_len = sizeof(hmac_buf);
int crypt_len = pkt->len;
HMAC_Init_ex(esp->hmac, NULL, 0, NULL, NULL);
HMAC_Update(esp->hmac, (void *)&pkt->esp, sizeof(pkt->esp) + pkt->len);
HMAC_Final(esp->hmac, hmac_buf, &hmac_len);
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;
if (!EVP_DecryptInit_ex(esp->cipher, NULL, NULL, NULL,
pkt->esp.iv)) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set up decryption context for ESP packet:\n"));
openconnect_report_ssl_errors(vpninfo);
return -EINVAL;
}
if (!EVP_DecryptUpdate(esp->cipher, pkt->data, &crypt_len,
pkt->data, pkt->len)) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to decrypt ESP packet:\n"));
openconnect_report_ssl_errors(vpninfo);
return -EINVAL;
}
return 0;
}
int encrypt_esp_packet(struct openconnect_info *vpninfo, struct pkt *pkt, int crypt_len)
{
int blksize = 16;
unsigned int hmac_len = vpninfo->hmac_out_len;
if (!EVP_EncryptUpdate(vpninfo->esp_out.cipher, pkt->data, &crypt_len,
pkt->data, crypt_len)) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to encrypt ESP packet:\n"));
openconnect_report_ssl_errors(vpninfo);
return -EINVAL;
}
HMAC_Init_ex(vpninfo->esp_out.hmac, NULL, 0, NULL, NULL);
HMAC_Update(vpninfo->esp_out.hmac, (void *)&pkt->esp, sizeof(pkt->esp) + crypt_len);
HMAC_Final(vpninfo->esp_out.hmac, pkt->data + crypt_len, &hmac_len);
EVP_EncryptUpdate(vpninfo->esp_out.cipher, vpninfo->esp_out.iv, &blksize,
pkt->data + crypt_len + hmac_len - blksize, blksize);
return 0;
}