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 #include "mbedtls/platform_util.h"
65
66 #include <limits.h>
67 #include <string.h>
68
69 /* If int isn't capable of storing 2^32 distinct values, the code of this
70 * module may cause a processor trap or a miscalculation. If int is more
71 * than 32 bits, the code may not calculate the intended values. */
72 #if INT_MIN + 1 != -0x7fffffff
73 #error "The HAVEGE module requires int to be exactly 32 bits, with INT_MIN = -2^31."
74 #endif
75 #if UINT_MAX != 0xffffffff
76 #error "The HAVEGE module requires unsigned to be exactly 32 bits."
77 #endif
78
79 /* ------------------------------------------------------------------------
80 * On average, one iteration accesses two 8-word blocks in the havege WALK
81 * table, and generates 16 words in the RES array.
82 *
83 * The data read in the WALK table is updated and permuted after each use.
84 * The result of the hardware clock counter read is used for this update.
85 *
86 * 25 conditional tests are present. The conditional tests are grouped in
87 * two nested groups of 12 conditional tests and 1 test that controls the
88 * permutation; on average, there should be 6 tests executed and 3 of them
89 * should be mispredicted.
90 * ------------------------------------------------------------------------
91 */
92
93 #define SWAP(X,Y) { unsigned *T = (X); (X) = (Y); (Y) = T; }
94
95 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
96 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
97
98 #define TST1_LEAVE U1++; }
99 #define TST2_LEAVE U2++; }
100
101 #define ONE_ITERATION \
102 \
103 PTEST = PT1 >> 20; \
104 \
105 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
106 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
107 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
108 \
109 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
110 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
111 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
112 \
113 PTX = (PT1 >> 18) & 7; \
114 PT1 &= 0x1FFF; \
115 PT2 &= 0x1FFF; \
116 CLK = (unsigned) mbedtls_timing_hardclock(); \
117 \
118 i = 0; \
119 A = &WALK[PT1 ]; RES[i++] ^= *A; \
120 B = &WALK[PT2 ]; RES[i++] ^= *B; \
121 C = &WALK[PT1 ^ 1]; RES[i++] ^= *C; \
122 D = &WALK[PT2 ^ 4]; RES[i++] ^= *D; \
123 \
124 IN = (*A >> (1)) ^ (*A << (31)) ^ CLK; \
125 *A = (*B >> (2)) ^ (*B << (30)) ^ CLK; \
126 *B = IN ^ U1; \
127 *C = (*C >> (3)) ^ (*C << (29)) ^ CLK; \
128 *D = (*D >> (4)) ^ (*D << (28)) ^ CLK; \
129 \
130 A = &WALK[PT1 ^ 2]; RES[i++] ^= *A; \
131 B = &WALK[PT2 ^ 2]; RES[i++] ^= *B; \
132 C = &WALK[PT1 ^ 3]; RES[i++] ^= *C; \
133 D = &WALK[PT2 ^ 6]; RES[i++] ^= *D; \
134 \
135 if( PTEST & 1 ) SWAP( A, C ); \
136 \
137 IN = (*A >> (5)) ^ (*A << (27)) ^ CLK; \
138 *A = (*B >> (6)) ^ (*B << (26)) ^ CLK; \
139 *B = IN; CLK = (unsigned) mbedtls_timing_hardclock(); \
140 *C = (*C >> (7)) ^ (*C << (25)) ^ CLK; \
141 *D = (*D >> (8)) ^ (*D << (24)) ^ CLK; \
142 \
143 A = &WALK[PT1 ^ 4]; \
144 B = &WALK[PT2 ^ 1]; \
145 \
146 PTEST = PT2 >> 1; \
147 \
148 PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]); \
149 PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8); \
150 PTY = (PT2 >> 10) & 7; \
151 \
152 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
153 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
154 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
155 \
156 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
157 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
158 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
159 \
160 C = &WALK[PT1 ^ 5]; \
161 D = &WALK[PT2 ^ 5]; \
162 \
163 RES[i++] ^= *A; \
164 RES[i++] ^= *B; \
165 RES[i++] ^= *C; \
166 RES[i++] ^= *D; \
167 \
168 IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK; \
169 *A = (*B >> (10)) ^ (*B << (22)) ^ CLK; \
170 *B = IN ^ U2; \
171 *C = (*C >> (11)) ^ (*C << (21)) ^ CLK; \
172 *D = (*D >> (12)) ^ (*D << (20)) ^ CLK; \
173 \
174 A = &WALK[PT1 ^ 6]; RES[i++] ^= *A; \
175 B = &WALK[PT2 ^ 3]; RES[i++] ^= *B; \
176 C = &WALK[PT1 ^ 7]; RES[i++] ^= *C; \
177 D = &WALK[PT2 ^ 7]; RES[i++] ^= *D; \
178 \
179 IN = (*A >> (13)) ^ (*A << (19)) ^ CLK; \
180 *A = (*B >> (14)) ^ (*B << (18)) ^ CLK; \
181 *B = IN; \
182 *C = (*C >> (15)) ^ (*C << (17)) ^ CLK; \
183 *D = (*D >> (16)) ^ (*D << (16)) ^ CLK; \
184 \
185 PT1 = ( RES[( i - 8 ) ^ PTX] ^ \
186 WALK[PT1 ^ PTX ^ 7] ) & (~1); \
187 PT1 ^= (PT2 ^ 0x10) & 0x10; \
188 \
189 for( n++, i = 0; i < 16; i++ ) \
190 POOL[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
191
192 /*
193 * Entropy gathering function
194 */
havege_fill(mbedtls_havege_state * hs)195 static void havege_fill( mbedtls_havege_state *hs )
196 {
197 unsigned i, n = 0;
198 unsigned U1, U2, *A, *B, *C, *D;
199 unsigned PT1, PT2, *WALK, *POOL, RES[16];
200 unsigned PTX, PTY, CLK, PTEST, IN;
201
202 WALK = (unsigned *) hs->WALK;
203 POOL = (unsigned *) hs->pool;
204 PT1 = hs->PT1;
205 PT2 = hs->PT2;
206
207 PTX = U1 = 0;
208 PTY = U2 = 0;
209
210 (void)PTX;
211
212 memset( RES, 0, sizeof( RES ) );
213
214 while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
215 {
216 ONE_ITERATION
217 ONE_ITERATION
218 ONE_ITERATION
219 ONE_ITERATION
220 }
221
222 hs->PT1 = PT1;
223 hs->PT2 = PT2;
224
225 hs->offset[0] = 0;
226 hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
227 }
228
229 /*
230 * HAVEGE initialization
231 */
mbedtls_havege_init(mbedtls_havege_state * hs)232 void mbedtls_havege_init( mbedtls_havege_state *hs )
233 {
234 memset( hs, 0, sizeof( mbedtls_havege_state ) );
235
236 havege_fill( hs );
237 }
238
mbedtls_havege_free(mbedtls_havege_state * hs)239 void mbedtls_havege_free( mbedtls_havege_state *hs )
240 {
241 if( hs == NULL )
242 return;
243
244 mbedtls_platform_zeroize( hs, sizeof( mbedtls_havege_state ) );
245 }
246
247 /*
248 * HAVEGE rand function
249 */
mbedtls_havege_random(void * p_rng,unsigned char * buf,size_t len)250 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
251 {
252 int val;
253 size_t use_len;
254 mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
255 unsigned char *p = buf;
256
257 while( len > 0 )
258 {
259 use_len = len;
260 if( use_len > sizeof(int) )
261 use_len = sizeof(int);
262
263 if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
264 havege_fill( hs );
265
266 val = hs->pool[hs->offset[0]++];
267 val ^= hs->pool[hs->offset[1]++];
268
269 memcpy( p, &val, use_len );
270
271 len -= use_len;
272 p += use_len;
273 }
274
275 return( 0 );
276 }
277
278 #endif /* MBEDTLS_HAVEGE_C */
279