411 lines
12 KiB
C
411 lines
12 KiB
C
/*
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* aes_gcm_mbedtls.c
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*
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* AES Galois 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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*
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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/gcm.h>
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#include "aes_gcm.h"
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#include "alloc.h"
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#include "err.h" /* for srtp_debug */
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#include "crypto_types.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_gcm = {
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0, /* debugging is off by default */
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"aes gcm mbedtls" /* printable module name */
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};
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/**
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* SRTP IV Formation for AES-GCM
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* https://tools.ietf.org/html/rfc7714#section-8.1
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* 0 0 0 0 0 0 0 0 0 0 1 1
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* 0 1 2 3 4 5 6 7 8 9 0 1
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* +--+--+--+--+--+--+--+--+--+--+--+--+
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* |00|00| SSRC | ROC | SEQ |---+
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* +--+--+--+--+--+--+--+--+--+--+--+--+ |
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* |
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* +--+--+--+--+--+--+--+--+--+--+--+--+ |
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* | Encryption Salt |->(+)
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* +--+--+--+--+--+--+--+--+--+--+--+--+ |
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* |
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* +--+--+--+--+--+--+--+--+--+--+--+--+ |
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* | Initialization Vector |<--+
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* +--+--+--+--+--+--+--+--+--+--+--+--+
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*
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* SRTCP IV Formation for AES-GCM
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* https://tools.ietf.org/html/rfc7714#section-9.1
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*
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*/
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/*
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* For now we only support 8 and 16 octet tags. The spec allows for
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* optional 12 byte tag, which may be supported in the future.
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*/
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#define GCM_IV_LEN 12
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#define GCM_AUTH_TAG_LEN 16
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#define GCM_AUTH_TAG_LEN_8 8
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#define FUNC_ENTRY() debug_print(srtp_mod_aes_gcm, "%s entry", __func__);
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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 28 or 44 for
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* AES-128-GCM or AES-256-GCM respectively. Note that the
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* key length includes the 14 byte salt value that is used when
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* initializing the KDF.
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*/
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static srtp_err_status_t srtp_aes_gcm_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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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *gcm;
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debug_print(srtp_mod_aes_gcm, "allocating cipher with key length %d",
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key_len);
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debug_print(srtp_mod_aes_gcm, "allocating cipher with tag length %d", tlen);
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/*
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* Verify the key_len is valid for one of: AES-128/256
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*/
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if (key_len != SRTP_AES_GCM_128_KEY_LEN_WSALT &&
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key_len != SRTP_AES_GCM_256_KEY_LEN_WSALT) {
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return (srtp_err_status_bad_param);
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}
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if (tlen != GCM_AUTH_TAG_LEN && tlen != GCM_AUTH_TAG_LEN_8) {
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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_gcm */
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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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gcm = (srtp_aes_gcm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_gcm_ctx_t));
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if (gcm == 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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gcm->ctx =
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(mbedtls_gcm_context *)srtp_crypto_alloc(sizeof(mbedtls_gcm_context));
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if (gcm->ctx == NULL) {
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srtp_crypto_free(gcm);
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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_gcm_init(gcm->ctx);
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/* set pointers */
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(*c)->state = gcm;
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/* setup cipher attributes */
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switch (key_len) {
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case SRTP_AES_GCM_128_KEY_LEN_WSALT:
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(*c)->type = &srtp_aes_gcm_128;
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(*c)->algorithm = SRTP_AES_GCM_128;
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gcm->key_size = SRTP_AES_128_KEY_LEN;
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gcm->tag_len = tlen;
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break;
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case SRTP_AES_GCM_256_KEY_LEN_WSALT:
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(*c)->type = &srtp_aes_gcm_256;
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(*c)->algorithm = SRTP_AES_GCM_256;
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gcm->key_size = SRTP_AES_256_KEY_LEN;
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gcm->tag_len = tlen;
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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 a GCM session
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*/
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static srtp_err_status_t srtp_aes_gcm_mbedtls_dealloc(srtp_cipher_t *c)
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{
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srtp_aes_gcm_ctx_t *ctx;
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FUNC_ENTRY();
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ctx = (srtp_aes_gcm_ctx_t *)c->state;
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if (ctx) {
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mbedtls_gcm_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_gcm_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_gcm_mbedtls_context_init(void *cv,
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const uint8_t *key)
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{
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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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uint32_t key_len_in_bits;
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int errCode = 0;
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c->dir = srtp_direction_any;
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c->aad_size = 0;
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debug_print(srtp_mod_aes_gcm, "key: %s",
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srtp_octet_string_hex_string(key, c->key_size));
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key_len_in_bits = (c->key_size << 3);
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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_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_gcm_setkey(c->ctx, MBEDTLS_CIPHER_ID_AES,
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(const unsigned char *)key, key_len_in_bits);
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if (errCode != 0) {
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debug_print(srtp_mod_aes_gcm, "mbedtls error code: %d", errCode);
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return srtp_err_status_init_fail;
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}
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return (srtp_err_status_ok);
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}
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static srtp_err_status_t srtp_aes_gcm_mbedtls_set_iv(
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void *cv,
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uint8_t *iv,
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srtp_cipher_direction_t direction)
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{
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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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if (direction != srtp_direction_encrypt &&
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direction != srtp_direction_decrypt) {
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return (srtp_err_status_bad_param);
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}
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c->dir = direction;
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debug_print(srtp_mod_aes_gcm, "setting iv: %s",
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srtp_octet_string_hex_string(iv, GCM_IV_LEN));
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c->iv_len = GCM_IV_LEN;
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memcpy(c->iv, iv, c->iv_len);
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return (srtp_err_status_ok);
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}
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/*
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* This function processes the AAD
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*
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* Parameters:
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* c Crypto context
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* aad Additional data to process for AEAD cipher suites
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* aad_len length of aad buffer
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*/
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static srtp_err_status_t srtp_aes_gcm_mbedtls_set_aad(void *cv,
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const uint8_t *aad,
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uint32_t aad_len)
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{
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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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debug_print(srtp_mod_aes_gcm, "setting AAD: %s",
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srtp_octet_string_hex_string(aad, aad_len));
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if (aad_len + c->aad_size > MAX_AD_SIZE) {
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return srtp_err_status_bad_param;
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}
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memcpy(c->aad + c->aad_size, aad, aad_len);
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c->aad_size += aad_len;
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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 GCM 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_gcm_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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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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int errCode = 0;
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if (c->dir != srtp_direction_encrypt && c->dir != srtp_direction_decrypt) {
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return (srtp_err_status_bad_param);
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}
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errCode = mbedtls_gcm_crypt_and_tag(c->ctx, MBEDTLS_GCM_ENCRYPT, *enc_len,
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c->iv, c->iv_len, c->aad, c->aad_size,
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buf, buf, c->tag_len, c->tag);
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c->aad_size = 0;
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if (errCode != 0) {
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debug_print(srtp_mod_aes_gcm, "mbedtls error code: %d", errCode);
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return srtp_err_status_bad_param;
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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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* This function calculates and returns the GCM tag for a given context.
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* This should be called after encrypting the data. The *len value
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* is increased by the tag size. The caller must ensure that *buf has
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* enough room to accept the appended tag.
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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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* len length of encrypt buffer
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*/
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static srtp_err_status_t srtp_aes_gcm_mbedtls_get_tag(void *cv,
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uint8_t *buf,
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uint32_t *len)
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{
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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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debug_print(srtp_mod_aes_gcm, "appended tag size: %d", c->tag_len);
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*len = c->tag_len;
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memcpy(buf, c->tag, c->tag_len);
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return (srtp_err_status_ok);
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}
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/*
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* This function decrypts a buffer using AES GCM 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_gcm_mbedtls_decrypt(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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FUNC_ENTRY();
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srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
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int errCode = 0;
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if (c->dir != srtp_direction_encrypt && c->dir != srtp_direction_decrypt) {
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return (srtp_err_status_bad_param);
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}
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debug_print(srtp_mod_aes_gcm, "AAD: %s",
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srtp_octet_string_hex_string(c->aad, c->aad_size));
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errCode = mbedtls_gcm_auth_decrypt(
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c->ctx, (*enc_len - c->tag_len), c->iv, c->iv_len, c->aad, c->aad_size,
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buf + (*enc_len - c->tag_len), c->tag_len, buf, buf);
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c->aad_size = 0;
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if (errCode != 0) {
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return (srtp_err_status_auth_fail);
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}
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/*
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* Reduce the buffer size by the tag length since the tag
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* is not part of the original payload
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*/
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*enc_len -= c->tag_len;
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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_gcm_128_mbedtls_description[] =
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"AES-128 GCM using mbedtls";
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static const char srtp_aes_gcm_256_mbedtls_description[] =
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"AES-256 GCM using mbedtls";
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/*
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* This is the vector function table for this crypto engine.
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*/
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const srtp_cipher_type_t srtp_aes_gcm_128 = {
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srtp_aes_gcm_mbedtls_alloc,
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srtp_aes_gcm_mbedtls_dealloc,
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srtp_aes_gcm_mbedtls_context_init,
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srtp_aes_gcm_mbedtls_set_aad,
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srtp_aes_gcm_mbedtls_encrypt,
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srtp_aes_gcm_mbedtls_decrypt,
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srtp_aes_gcm_mbedtls_set_iv,
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srtp_aes_gcm_mbedtls_get_tag,
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srtp_aes_gcm_128_mbedtls_description,
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&srtp_aes_gcm_128_test_case_0,
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SRTP_AES_GCM_128
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};
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/*
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* This is the vector function table for this crypto engine.
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*/
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const srtp_cipher_type_t srtp_aes_gcm_256 = {
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srtp_aes_gcm_mbedtls_alloc,
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srtp_aes_gcm_mbedtls_dealloc,
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srtp_aes_gcm_mbedtls_context_init,
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srtp_aes_gcm_mbedtls_set_aad,
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srtp_aes_gcm_mbedtls_encrypt,
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srtp_aes_gcm_mbedtls_decrypt,
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srtp_aes_gcm_mbedtls_set_iv,
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srtp_aes_gcm_mbedtls_get_tag,
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srtp_aes_gcm_256_mbedtls_description,
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&srtp_aes_gcm_256_test_case_0,
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SRTP_AES_GCM_256
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};
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