| Benny Prijono | 8a0ab28 | 2008-01-23 20:17:42 +0000 | [diff] [blame] | 1 | /* |
| 2 | * ctr_prng.c |
| 3 | * |
| 4 | * counter mode based pseudorandom source |
| 5 | * |
| 6 | * David A. McGrew |
| 7 | * Cisco Systems, Inc. |
| 8 | */ |
| 9 | /* |
| 10 | * |
| 11 | * Copyright(c) 2001-2006 Cisco Systems, Inc. |
| 12 | * All rights reserved. |
| 13 | * |
| 14 | * Redistribution and use in source and binary forms, with or without |
| 15 | * modification, are permitted provided that the following conditions |
| 16 | * are met: |
| 17 | * |
| 18 | * Redistributions of source code must retain the above copyright |
| 19 | * notice, this list of conditions and the following disclaimer. |
| 20 | * |
| 21 | * Redistributions in binary form must reproduce the above |
| 22 | * copyright notice, this list of conditions and the following |
| 23 | * disclaimer in the documentation and/or other materials provided |
| 24 | * with the distribution. |
| 25 | * |
| 26 | * Neither the name of the Cisco Systems, Inc. nor the names of its |
| 27 | * contributors may be used to endorse or promote products derived |
| 28 | * from this software without specific prior written permission. |
| 29 | * |
| 30 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 31 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 32 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| 33 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| 34 | * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| 35 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| 36 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| 37 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| 39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 40 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
| 41 | * OF THE POSSIBILITY OF SUCH DAMAGE. |
| 42 | * |
| 43 | */ |
| 44 | |
| 45 | |
| 46 | #include "prng.h" |
| 47 | |
| 48 | /* single, global prng structure */ |
| 49 | |
| 50 | ctr_prng_t ctr_prng; |
| 51 | |
| 52 | err_status_t |
| 53 | ctr_prng_init(rand_source_func_t random_source) { |
| 54 | uint8_t tmp_key[32]; |
| 55 | err_status_t status; |
| 56 | |
| 57 | /* initialize output count to zero */ |
| 58 | ctr_prng.octet_count = 0; |
| 59 | |
| 60 | /* set random source */ |
| 61 | ctr_prng.rand = random_source; |
| 62 | |
| 63 | /* initialize secret key from random source */ |
| 64 | status = random_source(tmp_key, 32); |
| 65 | if (status) |
| 66 | return status; |
| 67 | |
| 68 | /* initialize aes ctr context with random key */ |
| 69 | status = aes_icm_context_init(&ctr_prng.state, tmp_key); |
| 70 | if (status) |
| 71 | return status; |
| 72 | |
| 73 | return err_status_ok; |
| 74 | } |
| 75 | |
| 76 | err_status_t |
| 77 | ctr_prng_get_octet_string(void *dest, uint32_t len) { |
| 78 | err_status_t status; |
| 79 | |
| 80 | /* |
| 81 | * if we need to re-initialize the prng, do so now |
| 82 | * |
| 83 | * avoid 32-bit overflows by subtracting instead of adding |
| 84 | */ |
| 85 | if (ctr_prng.octet_count > MAX_PRNG_OUT_LEN - len) { |
| 86 | status = ctr_prng_init(ctr_prng.rand); |
| 87 | if (status) |
| 88 | return status; |
| 89 | } |
| 90 | ctr_prng.octet_count += len; |
| 91 | |
| 92 | /* |
| 93 | * write prng output |
| 94 | */ |
| 95 | status = aes_icm_output(&ctr_prng.state, (uint8_t*)dest, len); |
| 96 | if (status) |
| 97 | return status; |
| 98 | |
| 99 | return err_status_ok; |
| 100 | } |
| 101 | |
| 102 | err_status_t |
| 103 | ctr_prng_deinit(void) { |
| 104 | |
| 105 | /* nothing */ |
| 106 | |
| 107 | return err_status_ok; |
| 108 | } |