/*
* aes_icm_mbedtls.c
*
* AES Integer Counter Mode
*
* YongCheng Yang
*/
/*
*
* Copyright (c) 2013-2017, Cisco Systems, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the Cisco Systems, Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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
* COPYRIGHT HOLDERS OR CONTRIBUTORS 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.
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <mbedtls/aes.h>
#include "aes_icm_ext.h"
#include "crypto_types.h"
#include "err.h" /* for srtp_debug */
#include "alloc.h"
#include "cipher_types.h"
#include "cipher_test_cases.h"
srtp_debug_module_t srtp_mod_aes_icm = {
0, /* debugging is off by default */
"aes icm mbedtls" /* printable module name */
};
/*
* integer counter mode works as follows:
*
* https://tools.ietf.org/html/rfc3711#section-4.1.1
*
* E(k, IV) || E(k, IV + 1 mod 2^128) || E(k, IV + 2 mod 2^128) ...
* IV = (k_s * 2^16) XOR (SSRC * 2^64) XOR (i * 2^16)
*
* IV SHALL be defined by the SSRC, the SRTP packet index i,
* and the SRTP session salting key k_s.
*
* SSRC: 32bits.
* Sequence number: 16bits.
* nonce is 64bits. .
* packet index = ROC || SEQ. (ROC: Rollover counter)
*
* 16 bits
* <----->
* +------+------+------+------+------+------+------+------+
* | nonce | packet index | ctr |---+
* +------+------+------+------+------+------+------+------+ |
* |
* +------+------+------+------+------+------+------+------+ v
* | salt |000000|->(+)
* +------+------+------+------+------+------+------+------+ |
* |
* +---------+
* | encrypt |
* +---------+
* |
* +------+------+------+------+------+------+------+------+ |
* | keystream block |<--+
* +------+------+------+------+------+------+------+------+
*
* All fields are big-endian
*
* ctr is the block counter, which increments from zero for
* each packet (16 bits wide)
*
* packet index is distinct for each packet (48 bits wide)
*
* nonce can be distinct across many uses of the same key, or
* can be a fixed value per key, or can be per-packet randomness
* (64 bits)
*
*/
/*
* This function allocates a new instance of this crypto engine.
* The key_len parameter should be one of 30, 38, or 46 for
* AES-128, AES-192, and AES-256 respectively. Note, this key_len
* value is inflated, as it also accounts for the 112 bit salt
* value. The tlen argument is for the AEAD tag length, which
* isn't used in counter mode.
*/
static srtp_err_status_t srtp_aes_icm_mbedtls_alloc(srtp_cipher_t **c,
int key_len,
int tlen)
{
srtp_aes_icm_ctx_t *icm;
(void)tlen;
debug_print(srtp_mod_aes_icm, "allocating cipher with key length %d",
key_len);
/*
* Verify the key_len is valid for one of: AES-128/192/256
*/
if (key_len != SRTP_AES_ICM_128_KEY_LEN_WSALT &&
key_len != SRTP_AES_ICM_192_KEY_LEN_WSALT &&
key_len != SRTP_AES_ICM_256_KEY_LEN_WSALT) {
return srtp_err_status_bad_param;
}
/* allocate memory a cipher of type aes_icm */
*c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t));
if (*c == NULL) {
return srtp_err_status_alloc_fail;
}
icm = (srtp_aes_icm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_icm_ctx_t));
if (icm == NULL) {
srtp_crypto_free(*c);
*c = NULL;
return srtp_err_status_alloc_fail;
}
icm->ctx =
(mbedtls_aes_context *)srtp_crypto_alloc(sizeof(mbedtls_aes_context));
if (icm->ctx == NULL) {
srtp_crypto_free(icm);
srtp_crypto_free(*c);
*c = NULL;
return srtp_err_status_alloc_fail;
}
mbedtls_aes_init(icm->ctx);
/* set pointers */
(*c)->state = icm;
/* setup cipher parameters */
switch (key_len) {
case SRTP_AES_ICM_128_KEY_LEN_WSALT:
(*c)->algorithm = SRTP_AES_ICM_128;
(*c)->type = &srtp_aes_icm_128;
icm->key_size = SRTP_AES_128_KEY_LEN;
break;
case SRTP_AES_ICM_192_KEY_LEN_WSALT:
(*c)->algorithm = SRTP_AES_ICM_192;
(*c)->type = &srtp_aes_icm_192;
icm->key_size = SRTP_AES_192_KEY_LEN;
break;
case SRTP_AES_ICM_256_KEY_LEN_WSALT:
(*c)->algorithm = SRTP_AES_ICM_256;
(*c)->type = &srtp_aes_icm_256;
icm->key_size = SRTP_AES_256_KEY_LEN;
break;
}
/* set key size */
(*c)->key_len = key_len;
return srtp_err_status_ok;
}
/*
* This function deallocates an instance of this engine
*/
static srtp_err_status_t srtp_aes_icm_mbedtls_dealloc(srtp_cipher_t *c)
{
srtp_aes_icm_ctx_t *ctx;
if (c == NULL) {
return srtp_err_status_bad_param;
}
/*
* Free the aes context
*/
ctx = (srtp_aes_icm_ctx_t *)c->state;
if (ctx != NULL) {
mbedtls_aes_free(ctx->ctx);
srtp_crypto_free(ctx->ctx);
/* zeroize the key material */
octet_string_set_to_zero(ctx, sizeof(srtp_aes_icm_ctx_t));
srtp_crypto_free(ctx);
}
/* free memory */
srtp_crypto_free(c);
return srtp_err_status_ok;
}
static srtp_err_status_t srtp_aes_icm_mbedtls_context_init(void *cv,
const uint8_t *key)
{
srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
uint32_t key_size_in_bits = (c->key_size << 3);
int errcode = 0;
/*
* set counter and initial values to 'offset' value, being careful not to
* go past the end of the key buffer
*/
v128_set_to_zero(&c->counter);
v128_set_to_zero(&c->offset);
memcpy(&c->counter, key + c->key_size, SRTP_SALT_LEN);
memcpy(&c->offset, key + c->key_size, SRTP_SALT_LEN);
/* force last two octets of the offset to zero (for srtp compatibility) */
c->offset.v8[SRTP_SALT_LEN] = c->offset.v8[SRTP_SALT_LEN + 1] = 0;
c->counter.v8[SRTP_SALT_LEN] = c->counter.v8[SRTP_SALT_LEN + 1] = 0;
debug_print(srtp_mod_aes_icm, "key: %s",
srtp_octet_string_hex_string(key, c->key_size));
debug_print(srtp_mod_aes_icm, "offset: %s", v128_hex_string(&c->offset));
switch (c->key_size) {
case SRTP_AES_256_KEY_LEN:
case SRTP_AES_192_KEY_LEN:
case SRTP_AES_128_KEY_LEN:
break;
default:
return srtp_err_status_bad_param;
break;
}
errcode = mbedtls_aes_setkey_enc(c->ctx, key, key_size_in_bits);
if (errcode != 0) {
debug_print(srtp_mod_aes_icm, "errCode: %d", errcode);
}
return srtp_err_status_ok;
}
/*
* aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with
* the offset
*/
static srtp_err_status_t srtp_aes_icm_mbedtls_set_iv(
void *cv,
uint8_t *iv,
srtp_cipher_direction_t dir)
{
srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
v128_t nonce;
(void)dir;
c->nc_off = 0;
/* set nonce (for alignment) */
v128_copy_octet_string(&nonce, iv);
debug_print(srtp_mod_aes_icm, "setting iv: %s", v128_hex_string(&nonce));
v128_xor(&c->counter, &c->offset, &nonce);
debug_print(srtp_mod_aes_icm, "set_counter: %s",
v128_hex_string(&c->counter));
return srtp_err_status_ok;
}
/*
* This function encrypts a buffer using AES CTR mode
*
* Parameters:
* c Crypto context
* buf data to encrypt
* enc_len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_icm_mbedtls_encrypt(void *cv,
unsigned char *buf,
unsigned int *enc_len)
{
srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
int errCode = 0;
debug_print(srtp_mod_aes_icm, "rs0: %s", v128_hex_string(&c->counter));
errCode =
mbedtls_aes_crypt_ctr(c->ctx, *enc_len, &(c->nc_off), c->counter.v8,
c->stream_block.v8, buf, buf);
if (errCode != 0) {
debug_print(srtp_mod_aes_icm, "encrypt error: %d", errCode);
return srtp_err_status_cipher_fail;
}
return srtp_err_status_ok;
}
/*
* Name of this crypto engine
*/
static const char srtp_aes_icm_128_mbedtls_description[] =
"AES-128 counter mode using mbedtls";
static const char srtp_aes_icm_192_mbedtls_description[] =
"AES-192 counter mode using mbedtls";
static const char srtp_aes_icm_256_mbedtls_description[] =
"AES-256 counter mode using mbedtls";
/*
* This is the function table for this crypto engine.
* note: the encrypt function is identical to the decrypt function
*/
const srtp_cipher_type_t srtp_aes_icm_128 = {
srtp_aes_icm_mbedtls_alloc, /* */
srtp_aes_icm_mbedtls_dealloc, /* */
srtp_aes_icm_mbedtls_context_init, /* */
0, /* set_aad */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_set_iv, /* */
0, /* get_tag */
srtp_aes_icm_128_mbedtls_description, /* */
&srtp_aes_icm_128_test_case_0, /* */
SRTP_AES_ICM_128 /* */
};
/*
* This is the function table for this crypto engine.
* note: the encrypt function is identical to the decrypt function
*/
const srtp_cipher_type_t srtp_aes_icm_192 = {
srtp_aes_icm_mbedtls_alloc, /* */
srtp_aes_icm_mbedtls_dealloc, /* */
srtp_aes_icm_mbedtls_context_init, /* */
0, /* set_aad */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_set_iv, /* */
0, /* get_tag */
srtp_aes_icm_192_mbedtls_description, /* */
&srtp_aes_icm_192_test_case_0, /* */
SRTP_AES_ICM_192 /* */
};
/*
* This is the function table for this crypto engine.
* note: the encrypt function is identical to the decrypt function
*/
const srtp_cipher_type_t srtp_aes_icm_256 = {
srtp_aes_icm_mbedtls_alloc, /* */
srtp_aes_icm_mbedtls_dealloc, /* */
srtp_aes_icm_mbedtls_context_init, /* */
0, /* set_aad */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_encrypt, /* */
srtp_aes_icm_mbedtls_set_iv, /* */
0, /* get_tag */
srtp_aes_icm_256_mbedtls_description, /* */
&srtp_aes_icm_256_test_case_0, /* */
SRTP_AES_ICM_256 /* */
};