michael@0: /*
michael@0:  * ctr_prng.c 
michael@0:  *
michael@0:  * counter mode based pseudorandom source
michael@0:  *
michael@0:  * David A. McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: /*
michael@0:  *	
michael@0:  * Copyright(c) 2001-2006 Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: 
michael@0: #include "prng.h"
michael@0: 
michael@0: /* single, global prng structure */
michael@0: 
michael@0: ctr_prng_t ctr_prng;
michael@0: 
michael@0: err_status_t
michael@0: ctr_prng_init(rand_source_func_t random_source) {
michael@0:   uint8_t tmp_key[32];
michael@0:   err_status_t status;
michael@0: 
michael@0:   /* initialize output count to zero */
michael@0:   ctr_prng.octet_count = 0;
michael@0: 
michael@0:   /* set random source */
michael@0:   ctr_prng.rand = random_source;
michael@0:   
michael@0:   /* initialize secret key from random source */
michael@0:   status = random_source(tmp_key, 32);
michael@0:   if (status) 
michael@0:     return status;
michael@0: 
michael@0:   /* initialize aes ctr context with random key */
michael@0:   status = aes_icm_context_init(&ctr_prng.state, tmp_key, 30);
michael@0:   if (status) 
michael@0:     return status;
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: ctr_prng_get_octet_string(void *dest, uint32_t len) {
michael@0:   err_status_t status;
michael@0: 
michael@0:   /* 
michael@0:    * if we need to re-initialize the prng, do so now 
michael@0:    *
michael@0:    * avoid 32-bit overflows by subtracting instead of adding
michael@0:    */
michael@0:   if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
michael@0:     status = ctr_prng_init(ctr_prng.rand);    
michael@0:     if (status)
michael@0:       return status;
michael@0:   }
michael@0:   ctr_prng.octet_count += len;
michael@0: 
michael@0:   /*
michael@0:    * write prng output 
michael@0:    */
michael@0:   status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len);
michael@0:   if (status)
michael@0:     return status;
michael@0:   
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: ctr_prng_deinit(void) {
michael@0: 
michael@0:   /* nothing */
michael@0:   
michael@0:   return err_status_ok;  
michael@0: }