1 /** 2 * \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion 3 * 4 * Copyright The Mbed TLS Contributors 5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 6 * 7 * This file is provided under the Apache License 2.0, or the 8 * GNU General Public License v2.0 or later. 9 * 10 * ********** 11 * Apache License 2.0: 12 * 13 * Licensed under the Apache License, Version 2.0 (the "License"); you may 14 * not use this file except in compliance with the License. 15 * You may obtain a copy of the License at 16 * 17 * http://www.apache.org/licenses/LICENSE-2.0 18 * 19 * Unless required by applicable law or agreed to in writing, software 20 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 21 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 22 * See the License for the specific language governing permissions and 23 * limitations under the License. 24 * 25 * ********** 26 * 27 * ********** 28 * GNU General Public License v2.0 or later: 29 * 30 * This program is free software; you can redistribute it and/or modify 31 * it under the terms of the GNU General Public License as published by 32 * the Free Software Foundation; either version 2 of the License, or 33 * (at your option) any later version. 34 * 35 * This program is distributed in the hope that it will be useful, 36 * but WITHOUT ANY WARRANTY; without even the implied warranty of 37 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 38 * GNU General Public License for more details. 39 * 40 * You should have received a copy of the GNU General Public License along 41 * with this program; if not, write to the Free Software Foundation, Inc., 42 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 43 * 44 * ********** 45 */ 46 /* 47 * The HAVEGE RNG was designed by Andre Seznec in 2002. 48 * 49 * http://www.irisa.fr/caps/projects/hipsor/publi.php 50 * 51 * Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr 52 */ 53 54 #if !defined(MBEDTLS_CONFIG_FILE) 55 #include "mbedtls/config.h" 56 #else 57 #include MBEDTLS_CONFIG_FILE 58 #endif 59 60 #if defined(MBEDTLS_HAVEGE_C) 61 62 #include "mbedtls/havege.h" 63 #include "mbedtls/timing.h" 64 65 #include <limits.h> 66 #include <string.h> 67 68 /* If int isn't capable of storing 2^32 distinct values, the code of this 69 * module may cause a processor trap or a miscalculation. If int is more 70 * than 32 bits, the code may not calculate the intended values. */ 71 #if INT_MIN + 1 != -0x7fffffff 72 #error "The HAVEGE module requires int to be exactly 32 bits, with INT_MIN = -2^31." 73 #endif 74 #if UINT_MAX != 0xffffffff 75 #error "The HAVEGE module requires unsigned to be exactly 32 bits." 76 #endif 77 78 /* Implementation that should never be optimized out by the compiler */ 79 static void mbedtls_zeroize( void *v, size_t n ) { 80 volatile unsigned char *p = v; while( n-- ) *p++ = 0; 81 } 82 83 /* ------------------------------------------------------------------------ 84 * On average, one iteration accesses two 8-word blocks in the havege WALK 85 * table, and generates 16 words in the RES array. 86 * 87 * The data read in the WALK table is updated and permuted after each use. 88 * The result of the hardware clock counter read is used for this update. 89 * 90 * 25 conditional tests are present. The conditional tests are grouped in 91 * two nested groups of 12 conditional tests and 1 test that controls the 92 * permutation; on average, there should be 6 tests executed and 3 of them 93 * should be mispredicted. 94 * ------------------------------------------------------------------------ 95 */ 96 97 #define SWAP(X,Y) { unsigned *T = (X); (X) = (Y); (Y) = T; } 98 99 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1; 100 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1; 101 102 #define TST1_LEAVE U1++; } 103 #define TST2_LEAVE U2++; } 104 105 #define ONE_ITERATION \ 106 \ 107 PTEST = PT1 >> 20; \ 108 \ 109 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \ 110 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \ 111 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \ 112 \ 113 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \ 114 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \ 115 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \ 116 \ 117 PTX = (PT1 >> 18) & 7; \ 118 PT1 &= 0x1FFF; \ 119 PT2 &= 0x1FFF; \ 120 CLK = (unsigned) mbedtls_timing_hardclock(); \ 121 \ 122 i = 0; \ 123 A = &WALK[PT1 ]; RES[i++] ^= *A; \ 124 B = &WALK[PT2 ]; RES[i++] ^= *B; \ 125 C = &WALK[PT1 ^ 1]; RES[i++] ^= *C; \ 126 D = &WALK[PT2 ^ 4]; RES[i++] ^= *D; \ 127 \ 128 IN = (*A >> (1)) ^ (*A << (31)) ^ CLK; \ 129 *A = (*B >> (2)) ^ (*B << (30)) ^ CLK; \ 130 *B = IN ^ U1; \ 131 *C = (*C >> (3)) ^ (*C << (29)) ^ CLK; \ 132 *D = (*D >> (4)) ^ (*D << (28)) ^ CLK; \ 133 \ 134 A = &WALK[PT1 ^ 2]; RES[i++] ^= *A; \ 135 B = &WALK[PT2 ^ 2]; RES[i++] ^= *B; \ 136 C = &WALK[PT1 ^ 3]; RES[i++] ^= *C; \ 137 D = &WALK[PT2 ^ 6]; RES[i++] ^= *D; \ 138 \ 139 if( PTEST & 1 ) SWAP( A, C ); \ 140 \ 141 IN = (*A >> (5)) ^ (*A << (27)) ^ CLK; \ 142 *A = (*B >> (6)) ^ (*B << (26)) ^ CLK; \ 143 *B = IN; CLK = (unsigned) mbedtls_timing_hardclock(); \ 144 *C = (*C >> (7)) ^ (*C << (25)) ^ CLK; \ 145 *D = (*D >> (8)) ^ (*D << (24)) ^ CLK; \ 146 \ 147 A = &WALK[PT1 ^ 4]; \ 148 B = &WALK[PT2 ^ 1]; \ 149 \ 150 PTEST = PT2 >> 1; \ 151 \ 152 PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]); \ 153 PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8); \ 154 PTY = (PT2 >> 10) & 7; \ 155 \ 156 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \ 157 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \ 158 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \ 159 \ 160 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \ 161 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \ 162 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \ 163 \ 164 C = &WALK[PT1 ^ 5]; \ 165 D = &WALK[PT2 ^ 5]; \ 166 \ 167 RES[i++] ^= *A; \ 168 RES[i++] ^= *B; \ 169 RES[i++] ^= *C; \ 170 RES[i++] ^= *D; \ 171 \ 172 IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK; \ 173 *A = (*B >> (10)) ^ (*B << (22)) ^ CLK; \ 174 *B = IN ^ U2; \ 175 *C = (*C >> (11)) ^ (*C << (21)) ^ CLK; \ 176 *D = (*D >> (12)) ^ (*D << (20)) ^ CLK; \ 177 \ 178 A = &WALK[PT1 ^ 6]; RES[i++] ^= *A; \ 179 B = &WALK[PT2 ^ 3]; RES[i++] ^= *B; \ 180 C = &WALK[PT1 ^ 7]; RES[i++] ^= *C; \ 181 D = &WALK[PT2 ^ 7]; RES[i++] ^= *D; \ 182 \ 183 IN = (*A >> (13)) ^ (*A << (19)) ^ CLK; \ 184 *A = (*B >> (14)) ^ (*B << (18)) ^ CLK; \ 185 *B = IN; \ 186 *C = (*C >> (15)) ^ (*C << (17)) ^ CLK; \ 187 *D = (*D >> (16)) ^ (*D << (16)) ^ CLK; \ 188 \ 189 PT1 = ( RES[( i - 8 ) ^ PTX] ^ \ 190 WALK[PT1 ^ PTX ^ 7] ) & (~1); \ 191 PT1 ^= (PT2 ^ 0x10) & 0x10; \ 192 \ 193 for( n++, i = 0; i < 16; i++ ) \ 194 POOL[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i]; 195 196 /* 197 * Entropy gathering function 198 */ 199 static void havege_fill( mbedtls_havege_state *hs ) 200 { 201 unsigned i, n = 0; 202 unsigned U1, U2, *A, *B, *C, *D; 203 unsigned PT1, PT2, *WALK, *POOL, RES[16]; 204 unsigned PTX, PTY, CLK, PTEST, IN; 205 206 WALK = (unsigned *) hs->WALK; 207 POOL = (unsigned *) hs->pool; 208 PT1 = hs->PT1; 209 PT2 = hs->PT2; 210 211 PTX = U1 = 0; 212 PTY = U2 = 0; 213 214 (void)PTX; 215 216 memset( RES, 0, sizeof( RES ) ); 217 218 while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 ) 219 { 220 ONE_ITERATION 221 ONE_ITERATION 222 ONE_ITERATION 223 ONE_ITERATION 224 } 225 226 hs->PT1 = PT1; 227 hs->PT2 = PT2; 228 229 hs->offset[0] = 0; 230 hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2; 231 } 232 233 /* 234 * HAVEGE initialization 235 */ 236 void mbedtls_havege_init( mbedtls_havege_state *hs ) 237 { 238 memset( hs, 0, sizeof( mbedtls_havege_state ) ); 239 240 havege_fill( hs ); 241 } 242 243 void mbedtls_havege_free( mbedtls_havege_state *hs ) 244 { 245 if( hs == NULL ) 246 return; 247 248 mbedtls_zeroize( hs, sizeof( mbedtls_havege_state ) ); 249 } 250 251 /* 252 * HAVEGE rand function 253 */ 254 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len ) 255 { 256 int val; 257 size_t use_len; 258 mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng; 259 unsigned char *p = buf; 260 261 while( len > 0 ) 262 { 263 use_len = len; 264 if( use_len > sizeof(int) ) 265 use_len = sizeof(int); 266 267 if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE ) 268 havege_fill( hs ); 269 270 val = hs->pool[hs->offset[0]++]; 271 val ^= hs->pool[hs->offset[1]++]; 272 273 memcpy( p, &val, use_len ); 274 275 len -= use_len; 276 p += use_len; 277 } 278 279 return( 0 ); 280 } 281 282 #endif /* MBEDTLS_HAVEGE_C */ 283