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/*
* ctr_prng.c
*
* counter mode based pseudorandom source
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright(c) 2001-2006 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.
*
*/
#include "prng.h"
/* single, global prng structure */
ctr_prng_t ctr_prng;
err_status_t
ctr_prng_init(rand_source_func_t random_source) {
uint8_t tmp_key[32];
err_status_t status;
/* initialize output count to zero */
ctr_prng.octet_count = 0;
/* set random source */
ctr_prng.rand = random_source;
/* initialize secret key from random source */
status = random_source(tmp_key, 32);
if (status)
return status;
/* initialize aes ctr context with random key */
status = aes_icm_context_init(&ctr_prng.state, tmp_key, 30);
if (status)
return status;
return err_status_ok;
}
err_status_t
ctr_prng_get_octet_string(void *dest, uint32_t len) {
err_status_t status;
/*
* if we need to re-initialize the prng, do so now
*
* avoid 32-bit overflows by subtracting instead of adding
*/
if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
status = ctr_prng_init(ctr_prng.rand);
if (status)
return status;
}
ctr_prng.octet_count += len;
/*
* write prng output
*/
status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len);
if (status)
return status;
return err_status_ok;
}
err_status_t
ctr_prng_deinit(void) {
/* nothing */
return err_status_ok;
}
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