Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 1 | /* |
| 2 | * prng.c |
| 3 | * |
| 4 | * 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 | x917_prng_t x917_prng; |
| 51 | |
| 52 | err_status_t |
| 53 | x917_prng_init(rand_source_func_t random_source) { |
| 54 | v128_t tmp_key; |
| 55 | err_status_t status; |
| 56 | |
| 57 | /* initialize output count to zero */ |
| 58 | x917_prng.octet_count = 0; |
| 59 | |
| 60 | /* set random source */ |
| 61 | x917_prng.rand = random_source; |
| 62 | |
| 63 | /* initialize secret key from random source */ |
| 64 | status = random_source((uint8_t *)&tmp_key, 16); |
| 65 | if (status) |
| 66 | return status; |
| 67 | |
| 68 | /* expand aes key */ |
| 69 | aes_expand_encryption_key(&tmp_key, x917_prng.key); |
| 70 | |
| 71 | /* initialize prng state from random source */ |
| 72 | status = x917_prng.rand((uint8_t *)&x917_prng.state, 16); |
| 73 | if (status) |
| 74 | return status; |
| 75 | |
| 76 | return err_status_ok; |
| 77 | } |
| 78 | |
| 79 | err_status_t |
| 80 | x917_prng_get_octet_string(uint8_t *dest, uint32_t len) { |
| 81 | uint32_t t; |
| 82 | v128_t buffer; |
| 83 | uint32_t i, tail_len; |
| 84 | err_status_t status; |
| 85 | |
| 86 | /* |
| 87 | * if we need to re-initialize the prng, do so now |
| 88 | * |
| 89 | * avoid overflows by subtracting instead of adding |
| 90 | */ |
| 91 | if (x917_prng.octet_count > MAX_PRNG_OUT_LEN - len) { |
| 92 | status = x917_prng_init(x917_prng.rand); |
| 93 | if (status) |
| 94 | return status; |
| 95 | } |
| 96 | x917_prng.octet_count += len; |
| 97 | |
| 98 | /* find out the time */ |
| 99 | t = (uint32_t)time(NULL); |
| 100 | |
| 101 | /* loop until we have output enough data */ |
| 102 | for (i=0; i < len/16; i++) { |
| 103 | |
| 104 | /* exor time into state */ |
| 105 | x917_prng.state.v32[0] ^= t; |
| 106 | |
| 107 | /* copy state into buffer */ |
| 108 | v128_copy(&buffer, &x917_prng.state); |
| 109 | |
| 110 | /* apply aes to buffer */ |
| 111 | aes_encrypt(&buffer, x917_prng.key); |
| 112 | |
| 113 | /* write data to output */ |
| 114 | *dest++ = buffer.v8[0]; |
| 115 | *dest++ = buffer.v8[1]; |
| 116 | *dest++ = buffer.v8[2]; |
| 117 | *dest++ = buffer.v8[3]; |
| 118 | *dest++ = buffer.v8[4]; |
| 119 | *dest++ = buffer.v8[5]; |
| 120 | *dest++ = buffer.v8[6]; |
| 121 | *dest++ = buffer.v8[7]; |
| 122 | *dest++ = buffer.v8[8]; |
| 123 | *dest++ = buffer.v8[9]; |
| 124 | *dest++ = buffer.v8[10]; |
| 125 | *dest++ = buffer.v8[11]; |
| 126 | *dest++ = buffer.v8[12]; |
| 127 | *dest++ = buffer.v8[13]; |
| 128 | *dest++ = buffer.v8[14]; |
| 129 | *dest++ = buffer.v8[15]; |
| 130 | |
| 131 | /* exor time into buffer */ |
| 132 | buffer.v32[0] ^= t; |
| 133 | |
| 134 | /* encrypt buffer */ |
| 135 | aes_encrypt(&buffer, x917_prng.key); |
| 136 | |
| 137 | /* copy buffer into state */ |
| 138 | v128_copy(&x917_prng.state, &buffer); |
| 139 | |
| 140 | } |
| 141 | |
| 142 | /* if we need to output any more octets, we'll do so now */ |
| 143 | tail_len = len % 16; |
| 144 | if (tail_len) { |
| 145 | |
| 146 | /* exor time into state */ |
| 147 | x917_prng.state.v32[0] ^= t; |
| 148 | |
| 149 | /* copy value into buffer */ |
| 150 | v128_copy(&buffer, &x917_prng.state); |
| 151 | |
| 152 | /* apply aes to buffer */ |
| 153 | aes_encrypt(&buffer, x917_prng.key); |
| 154 | |
| 155 | /* write data to output */ |
| 156 | for (i=0; i < tail_len; i++) { |
| 157 | *dest++ = buffer.v8[i]; |
| 158 | } |
| 159 | |
| 160 | /* now update the state one more time */ |
| 161 | |
| 162 | /* exor time into buffer */ |
| 163 | buffer.v32[0] ^= t; |
| 164 | |
| 165 | /* encrypt buffer */ |
| 166 | aes_encrypt(&buffer, x917_prng.key); |
| 167 | |
| 168 | /* copy buffer into state */ |
| 169 | v128_copy(&x917_prng.state, &buffer); |
| 170 | |
| 171 | } |
| 172 | |
| 173 | return err_status_ok; |
| 174 | } |
| 175 | |
| 176 | err_status_t |
| 177 | x917_prng_deinit(void) { |
| 178 | |
| 179 | return err_status_ok; |
| 180 | } |