/*
* aes_gcm_mbedtls.c
*
* AES Galois 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/gcm.h>
#include "aes_gcm.h"
#include "alloc.h"
#include "err.h" /* for srtp_debug */
#include "crypto_types.h"
#include "cipher_types.h"
#include "cipher_test_cases.h"
srtp_debug_module_t srtp_mod_aes_gcm = {
0, /* debugging is off by default */
"aes gcm mbedtls" /* printable module name */
};
/**
* SRTP IV Formation for AES-GCM
* https://tools.ietf.org/html/rfc7714#section-8.1
* 0 0 0 0 0 0 0 0 0 0 1 1
* 0 1 2 3 4 5 6 7 8 9 0 1
* +--+--+--+--+--+--+--+--+--+--+--+--+
* |00|00| SSRC | ROC | SEQ |---+
* +--+--+--+--+--+--+--+--+--+--+--+--+ |
* |
* +--+--+--+--+--+--+--+--+--+--+--+--+ |
* | Encryption Salt |->(+)
* +--+--+--+--+--+--+--+--+--+--+--+--+ |
* |
* +--+--+--+--+--+--+--+--+--+--+--+--+ |
* | Initialization Vector |<--+
* +--+--+--+--+--+--+--+--+--+--+--+--+
*
* SRTCP IV Formation for AES-GCM
* https://tools.ietf.org/html/rfc7714#section-9.1
*
*/
/*
* For now we only support 8 and 16 octet tags. The spec allows for
* optional 12 byte tag, which may be supported in the future.
*/
#define GCM_IV_LEN 12
#define GCM_AUTH_TAG_LEN 16
#define GCM_AUTH_TAG_LEN_8 8
#define FUNC_ENTRY() debug_print(srtp_mod_aes_gcm, "%s entry", __func__);
/*
* This function allocates a new instance of this crypto engine.
* The key_len parameter should be one of 28 or 44 for
* AES-128-GCM or AES-256-GCM respectively. Note that the
* key length includes the 14 byte salt value that is used when
* initializing the KDF.
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_alloc(srtp_cipher_t **c,
int key_len,
int tlen)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *gcm;
debug_print(srtp_mod_aes_gcm, "allocating cipher with key length %d",
key_len);
debug_print(srtp_mod_aes_gcm, "allocating cipher with tag length %d", tlen);
/*
* Verify the key_len is valid for one of: AES-128/256
*/
if (key_len != SRTP_AES_GCM_128_KEY_LEN_WSALT &&
key_len != SRTP_AES_GCM_256_KEY_LEN_WSALT) {
return (srtp_err_status_bad_param);
}
if (tlen != GCM_AUTH_TAG_LEN && tlen != GCM_AUTH_TAG_LEN_8) {
return (srtp_err_status_bad_param);
}
/* allocate memory a cipher of type aes_gcm */
*c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t));
if (*c == NULL) {
return (srtp_err_status_alloc_fail);
}
gcm = (srtp_aes_gcm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_gcm_ctx_t));
if (gcm == NULL) {
srtp_crypto_free(*c);
*c = NULL;
return (srtp_err_status_alloc_fail);
}
gcm->ctx =
(mbedtls_gcm_context *)srtp_crypto_alloc(sizeof(mbedtls_gcm_context));
if (gcm->ctx == NULL) {
srtp_crypto_free(gcm);
srtp_crypto_free(*c);
*c = NULL;
return srtp_err_status_alloc_fail;
}
mbedtls_gcm_init(gcm->ctx);
/* set pointers */
(*c)->state = gcm;
/* setup cipher attributes */
switch (key_len) {
case SRTP_AES_GCM_128_KEY_LEN_WSALT:
(*c)->type = &srtp_aes_gcm_128;
(*c)->algorithm = SRTP_AES_GCM_128;
gcm->key_size = SRTP_AES_128_KEY_LEN;
gcm->tag_len = tlen;
break;
case SRTP_AES_GCM_256_KEY_LEN_WSALT:
(*c)->type = &srtp_aes_gcm_256;
(*c)->algorithm = SRTP_AES_GCM_256;
gcm->key_size = SRTP_AES_256_KEY_LEN;
gcm->tag_len = tlen;
break;
}
/* set key size */
(*c)->key_len = key_len;
return (srtp_err_status_ok);
}
/*
* This function deallocates a GCM session
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_dealloc(srtp_cipher_t *c)
{
srtp_aes_gcm_ctx_t *ctx;
FUNC_ENTRY();
ctx = (srtp_aes_gcm_ctx_t *)c->state;
if (ctx) {
mbedtls_gcm_free(ctx->ctx);
srtp_crypto_free(ctx->ctx);
/* zeroize the key material */
octet_string_set_to_zero(ctx, sizeof(srtp_aes_gcm_ctx_t));
srtp_crypto_free(ctx);
}
/* free memory */
srtp_crypto_free(c);
return (srtp_err_status_ok);
}
static srtp_err_status_t srtp_aes_gcm_mbedtls_context_init(void *cv,
const uint8_t *key)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
uint32_t key_len_in_bits;
int errCode = 0;
c->dir = srtp_direction_any;
c->aad_size = 0;
debug_print(srtp_mod_aes_gcm, "key: %s",
srtp_octet_string_hex_string(key, c->key_size));
key_len_in_bits = (c->key_size << 3);
switch (c->key_size) {
case SRTP_AES_256_KEY_LEN:
case SRTP_AES_128_KEY_LEN:
break;
default:
return (srtp_err_status_bad_param);
break;
}
errCode = mbedtls_gcm_setkey(c->ctx, MBEDTLS_CIPHER_ID_AES,
(const unsigned char *)key, key_len_in_bits);
if (errCode != 0) {
debug_print(srtp_mod_aes_gcm, "mbedtls error code: %d", errCode);
return srtp_err_status_init_fail;
}
return (srtp_err_status_ok);
}
static srtp_err_status_t srtp_aes_gcm_mbedtls_set_iv(
void *cv,
uint8_t *iv,
srtp_cipher_direction_t direction)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
if (direction != srtp_direction_encrypt &&
direction != srtp_direction_decrypt) {
return (srtp_err_status_bad_param);
}
c->dir = direction;
debug_print(srtp_mod_aes_gcm, "setting iv: %s",
srtp_octet_string_hex_string(iv, GCM_IV_LEN));
c->iv_len = GCM_IV_LEN;
memcpy(c->iv, iv, c->iv_len);
return (srtp_err_status_ok);
}
/*
* This function processes the AAD
*
* Parameters:
* c Crypto context
* aad Additional data to process for AEAD cipher suites
* aad_len length of aad buffer
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_set_aad(void *cv,
const uint8_t *aad,
uint32_t aad_len)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
debug_print(srtp_mod_aes_gcm, "setting AAD: %s",
srtp_octet_string_hex_string(aad, aad_len));
if (aad_len + c->aad_size > MAX_AD_SIZE) {
return srtp_err_status_bad_param;
}
memcpy(c->aad + c->aad_size, aad, aad_len);
c->aad_size += aad_len;
return (srtp_err_status_ok);
}
/*
* This function encrypts a buffer using AES GCM mode
*
* Parameters:
* c Crypto context
* buf data to encrypt
* enc_len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_encrypt(void *cv,
unsigned char *buf,
unsigned int *enc_len)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
int errCode = 0;
if (c->dir != srtp_direction_encrypt && c->dir != srtp_direction_decrypt) {
return (srtp_err_status_bad_param);
}
errCode = mbedtls_gcm_crypt_and_tag(c->ctx, MBEDTLS_GCM_ENCRYPT, *enc_len,
c->iv, c->iv_len, c->aad, c->aad_size,
buf, buf, c->tag_len, c->tag);
c->aad_size = 0;
if (errCode != 0) {
debug_print(srtp_mod_aes_gcm, "mbedtls error code: %d", errCode);
return srtp_err_status_bad_param;
}
return (srtp_err_status_ok);
}
/*
* This function calculates and returns the GCM tag for a given context.
* This should be called after encrypting the data. The *len value
* is increased by the tag size. The caller must ensure that *buf has
* enough room to accept the appended tag.
*
* Parameters:
* c Crypto context
* buf data to encrypt
* len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_get_tag(void *cv,
uint8_t *buf,
uint32_t *len)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
debug_print(srtp_mod_aes_gcm, "appended tag size: %d", c->tag_len);
*len = c->tag_len;
memcpy(buf, c->tag, c->tag_len);
return (srtp_err_status_ok);
}
/*
* This function decrypts a buffer using AES GCM mode
*
* Parameters:
* c Crypto context
* buf data to encrypt
* enc_len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_mbedtls_decrypt(void *cv,
unsigned char *buf,
unsigned int *enc_len)
{
FUNC_ENTRY();
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
int errCode = 0;
if (c->dir != srtp_direction_encrypt && c->dir != srtp_direction_decrypt) {
return (srtp_err_status_bad_param);
}
debug_print(srtp_mod_aes_gcm, "AAD: %s",
srtp_octet_string_hex_string(c->aad, c->aad_size));
errCode = mbedtls_gcm_auth_decrypt(
c->ctx, (*enc_len - c->tag_len), c->iv, c->iv_len, c->aad, c->aad_size,
buf + (*enc_len - c->tag_len), c->tag_len, buf, buf);
c->aad_size = 0;
if (errCode != 0) {
return (srtp_err_status_auth_fail);
}
/*
* Reduce the buffer size by the tag length since the tag
* is not part of the original payload
*/
*enc_len -= c->tag_len;
return (srtp_err_status_ok);
}
/*
* Name of this crypto engine
*/
static const char srtp_aes_gcm_128_mbedtls_description[] =
"AES-128 GCM using mbedtls";
static const char srtp_aes_gcm_256_mbedtls_description[] =
"AES-256 GCM using mbedtls";
/*
* This is the vector function table for this crypto engine.
*/
const srtp_cipher_type_t srtp_aes_gcm_128 = {
srtp_aes_gcm_mbedtls_alloc,
srtp_aes_gcm_mbedtls_dealloc,
srtp_aes_gcm_mbedtls_context_init,
srtp_aes_gcm_mbedtls_set_aad,
srtp_aes_gcm_mbedtls_encrypt,
srtp_aes_gcm_mbedtls_decrypt,
srtp_aes_gcm_mbedtls_set_iv,
srtp_aes_gcm_mbedtls_get_tag,
srtp_aes_gcm_128_mbedtls_description,
&srtp_aes_gcm_128_test_case_0,
SRTP_AES_GCM_128
};
/*
* This is the vector function table for this crypto engine.
*/
const srtp_cipher_type_t srtp_aes_gcm_256 = {
srtp_aes_gcm_mbedtls_alloc,
srtp_aes_gcm_mbedtls_dealloc,
srtp_aes_gcm_mbedtls_context_init,
srtp_aes_gcm_mbedtls_set_aad,
srtp_aes_gcm_mbedtls_encrypt,
srtp_aes_gcm_mbedtls_decrypt,
srtp_aes_gcm_mbedtls_set_iv,
srtp_aes_gcm_mbedtls_get_tag,
srtp_aes_gcm_256_mbedtls_description,
&srtp_aes_gcm_256_test_case_0,
SRTP_AES_GCM_256
};