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 #include "mbedtls/platform_util.h"
40 
41 #include <string.h>
42 
43 /* ------------------------------------------------------------------------
44  * On average, one iteration accesses two 8-word blocks in the havege WALK
45  * table, and generates 16 words in the RES array.
46  *
47  * The data read in the WALK table is updated and permuted after each use.
48  * The result of the hardware clock counter read is used  for this update.
49  *
50  * 25 conditional tests are present.  The conditional tests are grouped in
51  * two nested  groups of 12 conditional tests and 1 test that controls the
52  * permutation; on average, there should be 6 tests executed and 3 of them
53  * should be mispredicted.
54  * ------------------------------------------------------------------------
55  */
56 
57 #define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
58 
59 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
60 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
61 
62 #define TST1_LEAVE U1++; }
63 #define TST2_LEAVE U2++; }
64 
65 #define ONE_ITERATION                                   \
66                                                         \
67     PTEST = PT1 >> 20;                                  \
68                                                         \
69     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
70     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
71     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
72                                                         \
73     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
74     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
75     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
76                                                         \
77     PTX = (PT1 >> 18) & 7;                              \
78     PT1 &= 0x1FFF;                                      \
79     PT2 &= 0x1FFF;                                      \
80     CLK = (int) mbedtls_timing_hardclock();                            \
81                                                         \
82     i = 0;                                              \
83     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
84     B = &WALK[PT2    ]; RES[i++] ^= *B;                 \
85     C = &WALK[PT1 ^ 1]; RES[i++] ^= *C;                 \
86     D = &WALK[PT2 ^ 4]; RES[i++] ^= *D;                 \
87                                                         \
88     IN = (*A >> (1)) ^ (*A << (31)) ^ CLK;              \
89     *A = (*B >> (2)) ^ (*B << (30)) ^ CLK;              \
90     *B = IN ^ U1;                                       \
91     *C = (*C >> (3)) ^ (*C << (29)) ^ CLK;              \
92     *D = (*D >> (4)) ^ (*D << (28)) ^ CLK;              \
93                                                         \
94     A = &WALK[PT1 ^ 2]; RES[i++] ^= *A;                 \
95     B = &WALK[PT2 ^ 2]; RES[i++] ^= *B;                 \
96     C = &WALK[PT1 ^ 3]; RES[i++] ^= *C;                 \
97     D = &WALK[PT2 ^ 6]; RES[i++] ^= *D;                 \
98                                                         \
99     if( PTEST & 1 ) SWAP( A, C );                       \
100                                                         \
101     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
102     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
103     *B = IN; CLK = (int) mbedtls_timing_hardclock();                   \
104     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
105     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
106                                                         \
107     A = &WALK[PT1 ^ 4];                                 \
108     B = &WALK[PT2 ^ 1];                                 \
109                                                         \
110     PTEST = PT2 >> 1;                                   \
111                                                         \
112     PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]);   \
113     PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8);  \
114     PTY = (PT2 >> 10) & 7;                              \
115                                                         \
116     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
117     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
118     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
119                                                         \
120     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
121     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
122     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
123                                                         \
124     C = &WALK[PT1 ^ 5];                                 \
125     D = &WALK[PT2 ^ 5];                                 \
126                                                         \
127     RES[i++] ^= *A;                                     \
128     RES[i++] ^= *B;                                     \
129     RES[i++] ^= *C;                                     \
130     RES[i++] ^= *D;                                     \
131                                                         \
132     IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK;             \
133     *A = (*B >> (10)) ^ (*B << (22)) ^ CLK;             \
134     *B = IN ^ U2;                                       \
135     *C = (*C >> (11)) ^ (*C << (21)) ^ CLK;             \
136     *D = (*D >> (12)) ^ (*D << (20)) ^ CLK;             \
137                                                         \
138     A = &WALK[PT1 ^ 6]; RES[i++] ^= *A;                 \
139     B = &WALK[PT2 ^ 3]; RES[i++] ^= *B;                 \
140     C = &WALK[PT1 ^ 7]; RES[i++] ^= *C;                 \
141     D = &WALK[PT2 ^ 7]; RES[i++] ^= *D;                 \
142                                                         \
143     IN = (*A >> (13)) ^ (*A << (19)) ^ CLK;             \
144     *A = (*B >> (14)) ^ (*B << (18)) ^ CLK;             \
145     *B = IN;                                            \
146     *C = (*C >> (15)) ^ (*C << (17)) ^ CLK;             \
147     *D = (*D >> (16)) ^ (*D << (16)) ^ CLK;             \
148                                                         \
149     PT1 = ( RES[( i - 8 ) ^ PTX] ^                      \
150             WALK[PT1 ^ PTX ^ 7] ) & (~1);               \
151     PT1 ^= (PT2 ^ 0x10) & 0x10;                         \
152                                                         \
153     for( n++, i = 0; i < 16; i++ )                      \
154         hs->pool[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
155 
156 /*
157  * Entropy gathering function
158  */
havege_fill(mbedtls_havege_state * hs)159 static void havege_fill( mbedtls_havege_state *hs )
160 {
161     int i, n = 0;
162     int  U1,  U2, *A, *B, *C, *D;
163     int PT1, PT2, *WALK, RES[16];
164     int PTX, PTY, CLK, PTEST, IN;
165 
166     WALK = hs->WALK;
167     PT1  = hs->PT1;
168     PT2  = hs->PT2;
169 
170     PTX  = U1 = 0;
171     PTY  = U2 = 0;
172 
173     (void)PTX;
174 
175     memset( RES, 0, sizeof( RES ) );
176 
177     while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
178     {
179         ONE_ITERATION
180         ONE_ITERATION
181         ONE_ITERATION
182         ONE_ITERATION
183     }
184 
185     hs->PT1 = PT1;
186     hs->PT2 = PT2;
187 
188     hs->offset[0] = 0;
189     hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
190 }
191 
192 /*
193  * HAVEGE initialization
194  */
mbedtls_havege_init(mbedtls_havege_state * hs)195 void mbedtls_havege_init( mbedtls_havege_state *hs )
196 {
197     memset( hs, 0, sizeof( mbedtls_havege_state ) );
198 
199     havege_fill( hs );
200 }
201 
mbedtls_havege_free(mbedtls_havege_state * hs)202 void mbedtls_havege_free( mbedtls_havege_state *hs )
203 {
204     if( hs == NULL )
205         return;
206 
207     mbedtls_platform_zeroize( hs, sizeof( mbedtls_havege_state ) );
208 }
209 
210 /*
211  * HAVEGE rand function
212  */
mbedtls_havege_random(void * p_rng,unsigned char * buf,size_t len)213 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
214 {
215     int val;
216     size_t use_len;
217     mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
218     unsigned char *p = buf;
219 
220     while( len > 0 )
221     {
222         use_len = len;
223         if( use_len > sizeof(int) )
224             use_len = sizeof(int);
225 
226         if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
227             havege_fill( hs );
228 
229         val  = hs->pool[hs->offset[0]++];
230         val ^= hs->pool[hs->offset[1]++];
231 
232         memcpy( p, &val, use_len );
233 
234         len -= use_len;
235         p += use_len;
236     }
237 
238     return( 0 );
239 }
240 
241 #endif /* MBEDTLS_HAVEGE_C */
242