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