1 /**
2 * \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21 /*
22 * The HAVEGE RNG was designed by Andre Seznec in 2002.
23 *
24 * http://www.irisa.fr/caps/projects/hipsor/publi.php
25 *
26 * Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
27 */
28
29 #if !defined(MBEDTLS_CONFIG_FILE)
30 #include "mbedtls/config.h"
31 #else
32 #include MBEDTLS_CONFIG_FILE
33 #endif
34
35 #if defined(MBEDTLS_HAVEGE_C)
36
37 #include "mbedtls/havege.h"
38 #include "mbedtls/timing.h"
39
40 #include <string.h>
41
42 /* Implementation that should never be optimized out by the compiler */
mbedtls_zeroize(void * v,size_t n)43 static void mbedtls_zeroize( void *v, size_t n ) {
44 volatile unsigned char *p = v; while( n-- ) *p++ = 0;
45 }
46
47 /* ------------------------------------------------------------------------
48 * On average, one iteration accesses two 8-word blocks in the havege WALK
49 * table, and generates 16 words in the RES array.
50 *
51 * The data read in the WALK table is updated and permuted after each use.
52 * The result of the hardware clock counter read is used for this update.
53 *
54 * 25 conditional tests are present. The conditional tests are grouped in
55 * two nested groups of 12 conditional tests and 1 test that controls the
56 * permutation; on average, there should be 6 tests executed and 3 of them
57 * should be mispredicted.
58 * ------------------------------------------------------------------------
59 */
60
61 #define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
62
63 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
64 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
65
66 #define TST1_LEAVE U1++; }
67 #define TST2_LEAVE U2++; }
68
69 #define ONE_ITERATION \
70 \
71 PTEST = PT1 >> 20; \
72 \
73 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
74 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
75 TST1_ENTER TST1_ENTER TST1_ENTER TST1_ENTER \
76 \
77 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
78 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
79 TST1_LEAVE TST1_LEAVE TST1_LEAVE TST1_LEAVE \
80 \
81 PTX = (PT1 >> 18) & 7; \
82 PT1 &= 0x1FFF; \
83 PT2 &= 0x1FFF; \
84 CLK = (int) mbedtls_timing_hardclock(); \
85 \
86 i = 0; \
87 A = &WALK[PT1 ]; RES[i++] ^= *A; \
88 B = &WALK[PT2 ]; RES[i++] ^= *B; \
89 C = &WALK[PT1 ^ 1]; RES[i++] ^= *C; \
90 D = &WALK[PT2 ^ 4]; RES[i++] ^= *D; \
91 \
92 IN = (*A >> (1)) ^ (*A << (31)) ^ CLK; \
93 *A = (*B >> (2)) ^ (*B << (30)) ^ CLK; \
94 *B = IN ^ U1; \
95 *C = (*C >> (3)) ^ (*C << (29)) ^ CLK; \
96 *D = (*D >> (4)) ^ (*D << (28)) ^ CLK; \
97 \
98 A = &WALK[PT1 ^ 2]; RES[i++] ^= *A; \
99 B = &WALK[PT2 ^ 2]; RES[i++] ^= *B; \
100 C = &WALK[PT1 ^ 3]; RES[i++] ^= *C; \
101 D = &WALK[PT2 ^ 6]; RES[i++] ^= *D; \
102 \
103 if( PTEST & 1 ) SWAP( A, C ); \
104 \
105 IN = (*A >> (5)) ^ (*A << (27)) ^ CLK; \
106 *A = (*B >> (6)) ^ (*B << (26)) ^ CLK; \
107 *B = IN; CLK = (int) mbedtls_timing_hardclock(); \
108 *C = (*C >> (7)) ^ (*C << (25)) ^ CLK; \
109 *D = (*D >> (8)) ^ (*D << (24)) ^ CLK; \
110 \
111 A = &WALK[PT1 ^ 4]; \
112 B = &WALK[PT2 ^ 1]; \
113 \
114 PTEST = PT2 >> 1; \
115 \
116 PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]); \
117 PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8); \
118 PTY = (PT2 >> 10) & 7; \
119 \
120 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
121 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
122 TST2_ENTER TST2_ENTER TST2_ENTER TST2_ENTER \
123 \
124 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
125 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
126 TST2_LEAVE TST2_LEAVE TST2_LEAVE TST2_LEAVE \
127 \
128 C = &WALK[PT1 ^ 5]; \
129 D = &WALK[PT2 ^ 5]; \
130 \
131 RES[i++] ^= *A; \
132 RES[i++] ^= *B; \
133 RES[i++] ^= *C; \
134 RES[i++] ^= *D; \
135 \
136 IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK; \
137 *A = (*B >> (10)) ^ (*B << (22)) ^ CLK; \
138 *B = IN ^ U2; \
139 *C = (*C >> (11)) ^ (*C << (21)) ^ CLK; \
140 *D = (*D >> (12)) ^ (*D << (20)) ^ CLK; \
141 \
142 A = &WALK[PT1 ^ 6]; RES[i++] ^= *A; \
143 B = &WALK[PT2 ^ 3]; RES[i++] ^= *B; \
144 C = &WALK[PT1 ^ 7]; RES[i++] ^= *C; \
145 D = &WALK[PT2 ^ 7]; RES[i++] ^= *D; \
146 \
147 IN = (*A >> (13)) ^ (*A << (19)) ^ CLK; \
148 *A = (*B >> (14)) ^ (*B << (18)) ^ CLK; \
149 *B = IN; \
150 *C = (*C >> (15)) ^ (*C << (17)) ^ CLK; \
151 *D = (*D >> (16)) ^ (*D << (16)) ^ CLK; \
152 \
153 PT1 = ( RES[( i - 8 ) ^ PTX] ^ \
154 WALK[PT1 ^ PTX ^ 7] ) & (~1); \
155 PT1 ^= (PT2 ^ 0x10) & 0x10; \
156 \
157 for( n++, i = 0; i < 16; i++ ) \
158 hs->pool[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
159
160 /*
161 * Entropy gathering function
162 */
havege_fill(mbedtls_havege_state * hs)163 static void havege_fill( mbedtls_havege_state *hs )
164 {
165 int i, n = 0;
166 int U1, U2, *A, *B, *C, *D;
167 int PT1, PT2, *WALK, RES[16];
168 int PTX, PTY, CLK, PTEST, IN;
169
170 WALK = hs->WALK;
171 PT1 = hs->PT1;
172 PT2 = hs->PT2;
173
174 PTX = U1 = 0;
175 PTY = U2 = 0;
176
177 (void)PTX;
178
179 memset( RES, 0, sizeof( RES ) );
180
181 while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
182 {
183 ONE_ITERATION
184 ONE_ITERATION
185 ONE_ITERATION
186 ONE_ITERATION
187 }
188
189 hs->PT1 = PT1;
190 hs->PT2 = PT2;
191
192 hs->offset[0] = 0;
193 hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
194 }
195
196 /*
197 * HAVEGE initialization
198 */
mbedtls_havege_init(mbedtls_havege_state * hs)199 void mbedtls_havege_init( mbedtls_havege_state *hs )
200 {
201 memset( hs, 0, sizeof( mbedtls_havege_state ) );
202
203 havege_fill( hs );
204 }
205
mbedtls_havege_free(mbedtls_havege_state * hs)206 void mbedtls_havege_free( mbedtls_havege_state *hs )
207 {
208 if( hs == NULL )
209 return;
210
211 mbedtls_zeroize( hs, sizeof( mbedtls_havege_state ) );
212 }
213
214 /*
215 * HAVEGE rand function
216 */
mbedtls_havege_random(void * p_rng,unsigned char * buf,size_t len)217 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
218 {
219 int val;
220 size_t use_len;
221 mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
222 unsigned char *p = buf;
223
224 while( len > 0 )
225 {
226 use_len = len;
227 if( use_len > sizeof(int) )
228 use_len = sizeof(int);
229
230 if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
231 havege_fill( hs );
232
233 val = hs->pool[hs->offset[0]++];
234 val ^= hs->pool[hs->offset[1]++];
235
236 memcpy( p, &val, use_len );
237
238 len -= use_len;
239 p += use_len;
240 }
241
242 return( 0 );
243 }
244
245 #endif /* MBEDTLS_HAVEGE_C */
246
