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/**
* @file
* SNMPv3 crypto/auth functions implemented for ARM mbedtls.
*/
/*
* Copyright (c) 2016 Elias Oenal and Dirk Ziegelmeier.
* All rights reserved.
*
* 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.
*
* Author: Elias Oenal <lwip@eliasoenal.com>
* Dirk Ziegelmeier <dirk@ziegelmeier.net>
*/
#include "lwip/apps/snmpv3.h"
#include "snmpv3_priv.h"
#include "lwip/arch.h"
#include "snmp_msg.h"
#include "lwip/sys.h"
#include <string.h>
#if LWIP_SNMP && LWIP_SNMP_V3 && LWIP_SNMP_V3_MBEDTLS
#include "mbedtls/md.h"
#include "mbedtls/cipher.h"
#include "mbedtls/md5.h"
#include "mbedtls/sha1.h"
err_t
snmpv3_auth(struct snmp_pbuf_stream *stream, u16_t length,
const u8_t *key, snmpv3_auth_algo_t algo, u8_t *hmac_out)
{
u32_t i;
u8_t key_len;
const mbedtls_md_info_t *md_info;
mbedtls_md_context_t ctx;
struct snmp_pbuf_stream read_stream;
snmp_pbuf_stream_init(&read_stream, stream->pbuf, stream->offset, stream->length);
if (algo == SNMP_V3_AUTH_ALGO_MD5) {
md_info = mbedtls_md_info_from_type(MBEDTLS_MD_MD5);
key_len = SNMP_V3_MD5_LEN;
} else if (algo == SNMP_V3_AUTH_ALGO_SHA) {
md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA1);
key_len = SNMP_V3_SHA_LEN;
} else {
return ERR_ARG;
}
mbedtls_md_init(&ctx);
if (mbedtls_md_setup(&ctx, md_info, 1) != 0) {
return ERR_ARG;
}
if (mbedtls_md_hmac_starts(&ctx, key, key_len) != 0) {
goto free_md;
}
for (i = 0; i < length; i++) {
u8_t byte;
if (snmp_pbuf_stream_read(&read_stream, &byte)) {
goto free_md;
}
if (mbedtls_md_hmac_update(&ctx, &byte, 1) != 0) {
goto free_md;
}
}
if (mbedtls_md_hmac_finish(&ctx, hmac_out) != 0) {
goto free_md;
}
mbedtls_md_free(&ctx);
return ERR_OK;
free_md:
mbedtls_md_free(&ctx);
return ERR_ARG;
}
#if LWIP_SNMP_V3_CRYPTO
err_t
snmpv3_crypt(struct snmp_pbuf_stream *stream, u16_t length,
const u8_t *key, const u8_t *priv_param, const u32_t engine_boots,
const u32_t engine_time, snmpv3_priv_algo_t algo, snmpv3_priv_mode_t mode)
{
size_t i;
mbedtls_cipher_context_t ctx;
const mbedtls_cipher_info_t *cipher_info;
struct snmp_pbuf_stream read_stream;
struct snmp_pbuf_stream write_stream;
snmp_pbuf_stream_init(&read_stream, stream->pbuf, stream->offset, stream->length);
snmp_pbuf_stream_init(&write_stream, stream->pbuf, stream->offset, stream->length);
mbedtls_cipher_init(&ctx);
if (algo == SNMP_V3_PRIV_ALGO_DES) {
u8_t iv_local[8];
u8_t out_bytes[8];
size_t out_len;
/* RFC 3414 mandates padding for DES */
if ((length & 0x07) != 0) {
return ERR_ARG;
}
cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_DES_CBC);
if (mbedtls_cipher_setup(&ctx, cipher_info) != 0) {
return ERR_ARG;
}
if (mbedtls_cipher_set_padding_mode(&ctx, MBEDTLS_PADDING_NONE) != 0) {
return ERR_ARG;
}
if (mbedtls_cipher_setkey(&ctx, key, 8 * 8, (mode == SNMP_V3_PRIV_MODE_ENCRYPT) ? MBEDTLS_ENCRYPT : MBEDTLS_DECRYPT) != 0) {
goto error;
}
/* Prepare IV */
for (i = 0; i < LWIP_ARRAYSIZE(iv_local); i++) {
iv_local[i] = priv_param[i] ^ key[i + 8];
}
if (mbedtls_cipher_set_iv(&ctx, iv_local, LWIP_ARRAYSIZE(iv_local)) != 0) {
goto error;
}
for (i = 0; i < length; i += 8) {
size_t j;
u8_t in_bytes[8];
out_len = LWIP_ARRAYSIZE(out_bytes) ;
for (j = 0; j < LWIP_ARRAYSIZE(in_bytes); j++) {
if (snmp_pbuf_stream_read(&read_stream, &in_bytes[j]) != ERR_OK) {
goto error;
}
}
if (mbedtls_cipher_update(&ctx, in_bytes, LWIP_ARRAYSIZE(in_bytes), out_bytes, &out_len) != 0) {
goto error;
}
if (snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len) != ERR_OK) {
goto error;
}
}
out_len = LWIP_ARRAYSIZE(out_bytes);
if (mbedtls_cipher_finish(&ctx, out_bytes, &out_len) != 0) {
goto error;
}
if (snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len) != ERR_OK) {
goto error;
}
} else if (algo == SNMP_V3_PRIV_ALGO_AES) {
u8_t iv_local[16];
cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_128_CFB128);
if (mbedtls_cipher_setup(&ctx, cipher_info) != 0) {
return ERR_ARG;
}
if (mbedtls_cipher_setkey(&ctx, key, 16 * 8, (mode == SNMP_V3_PRIV_MODE_ENCRYPT) ? MBEDTLS_ENCRYPT : MBEDTLS_DECRYPT) != 0) {
goto error;
}
/*
* IV is the big endian concatenation of boots,
* uptime and priv param - see RFC3826.
*/
iv_local[0 + 0] = (engine_boots >> 24) & 0xFF;
iv_local[0 + 1] = (engine_boots >> 16) & 0xFF;
iv_local[0 + 2] = (engine_boots >> 8) & 0xFF;
iv_local[0 + 3] = (engine_boots >> 0) & 0xFF;
iv_local[4 + 0] = (engine_time >> 24) & 0xFF;
iv_local[4 + 1] = (engine_time >> 16) & 0xFF;
iv_local[4 + 2] = (engine_time >> 8) & 0xFF;
iv_local[4 + 3] = (engine_time >> 0) & 0xFF;
SMEMCPY(iv_local + 8, priv_param, 8);
if (mbedtls_cipher_set_iv(&ctx, iv_local, LWIP_ARRAYSIZE(iv_local)) != 0) {
goto error;
}
for (i = 0; i < length; i++) {
u8_t in_byte;
u8_t out_byte;
size_t out_len = sizeof(out_byte);
if (snmp_pbuf_stream_read(&read_stream, &in_byte) != ERR_OK) {
goto error;
}
if (mbedtls_cipher_update(&ctx, &in_byte, sizeof(in_byte), &out_byte, &out_len) != 0) {
goto error;
}
if (snmp_pbuf_stream_write(&write_stream, out_byte) != ERR_OK) {
goto error;
}
}
} else {
return ERR_ARG;
}
mbedtls_cipher_free(&ctx);
return ERR_OK;
error:
mbedtls_cipher_free(&ctx);
return ERR_OK;
}
#endif /* LWIP_SNMP_V3_CRYPTO */
/* A.2.1. Password to Key Sample Code for MD5 */
void
snmpv3_password_to_key_md5(
const u8_t *password, /* IN */
size_t passwordlen, /* IN */
const u8_t *engineID, /* IN - pointer to snmpEngineID */
u8_t engineLength,/* IN - length of snmpEngineID */
u8_t *key) /* OUT - pointer to caller 16-octet buffer */
{
mbedtls_md5_context MD;
u8_t *cp, password_buf[64];
u32_t password_index = 0;
u8_t i;
u32_t count = 0;
mbedtls_md5_init(&MD); /* initialize MD5 */
mbedtls_md5_starts(&MD);
/**********************************************/
/* Use while loop until we've done 1 Megabyte */
/**********************************************/
while (count < 1048576) {
cp = password_buf;
for (i = 0; i < 64; i++) {
/*************************************************/
/* Take the next octet of the password, wrapping */
/* to the beginning of the password as necessary.*/
/*************************************************/
*cp++ = password[password_index++ % passwordlen];
}
mbedtls_md5_update(&MD, password_buf, 64);
count += 64;
}
mbedtls_md5_finish(&MD, key); /* tell MD5 we're done */
/*****************************************************/
/* Now localize the key with the engineID and pass */
/* through MD5 to produce final key */
/* May want to ensure that engineLength <= 32, */
/* otherwise need to use a buffer larger than 64 */
/*****************************************************/
SMEMCPY(password_buf, key, 16);
MEMCPY(password_buf + 16, engineID, engineLength);
SMEMCPY(password_buf + 16 + engineLength, key, 16);
mbedtls_md5_starts(&MD);
mbedtls_md5_update(&MD, password_buf, 32 + engineLength);
mbedtls_md5_finish(&MD, key);
mbedtls_md5_free(&MD);
return;
}
/* A.2.2. Password to Key Sample Code for SHA */
void
snmpv3_password_to_key_sha(
const u8_t *password, /* IN */
size_t passwordlen, /* IN */
const u8_t *engineID, /* IN - pointer to snmpEngineID */
u8_t engineLength,/* IN - length of snmpEngineID */
u8_t *key) /* OUT - pointer to caller 20-octet buffer */
{
mbedtls_sha1_context SH;
u8_t *cp, password_buf[72];
u32_t password_index = 0;
u8_t i;
u32_t count = 0;
mbedtls_sha1_init(&SH); /* initialize SHA */
mbedtls_sha1_starts(&SH);
/**********************************************/
/* Use while loop until we've done 1 Megabyte */
/**********************************************/
while (count < 1048576) {
cp = password_buf;
for (i = 0; i < 64; i++) {
/*************************************************/
/* Take the next octet of the password, wrapping */
/* to the beginning of the password as necessary.*/
/*************************************************/
*cp++ = password[password_index++ % passwordlen];
}
mbedtls_sha1_update(&SH, password_buf, 64);
count += 64;
}
mbedtls_sha1_finish(&SH, key); /* tell SHA we're done */
/*****************************************************/
/* Now localize the key with the engineID and pass */
/* through SHA to produce final key */
/* May want to ensure that engineLength <= 32, */
/* otherwise need to use a buffer larger than 72 */
/*****************************************************/
SMEMCPY(password_buf, key, 20);
MEMCPY(password_buf + 20, engineID, engineLength);
SMEMCPY(password_buf + 20 + engineLength, key, 20);
mbedtls_sha1_starts(&SH);
mbedtls_sha1_update(&SH, password_buf, 40 + engineLength);
mbedtls_sha1_finish(&SH, key);
mbedtls_sha1_free(&SH);
return;
}
#endif /* LWIP_SNMP && LWIP_SNMP_V3 && LWIP_SNMP_V3_MBEDTLS */