havege.c

00001 /**
00002  *  \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
00003  *
00004  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  *
00019  *  This file is part of mbed TLS (https://tls.mbed.org)
00020  */
00021 /*
00022  *  The HAVEGE RNG was designed by Andre Seznec in 2002.
00023  *
00024  *  http://www.irisa.fr/caps/projects/hipsor/publi.php
00025  *
00026  *  Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
00027  */
00028 
00029 #if !defined(MBEDTLS_CONFIG_FILE)
00030 #include "mbedtls/config.h"
00031 #else
00032 #include MBEDTLS_CONFIG_FILE
00033 #endif
00034 
00035 #if defined(MBEDTLS_HAVEGE_C)
00036 
00037 #include "mbedtls/havege.h"
00038 #include "mbedtls/timing.h"
00039 #include "mbedtls/platform_util.h"
00040 
00041 #include <string.h>
00042 
00043 /* ------------------------------------------------------------------------
00044  * On average, one iteration accesses two 8-word blocks in the havege WALK
00045  * table, and generates 16 words in the RES array.
00046  *
00047  * The data read in the WALK table is updated and permuted after each use.
00048  * The result of the hardware clock counter read is used  for this update.
00049  *
00050  * 25 conditional tests are present.  The conditional tests are grouped in
00051  * two nested  groups of 12 conditional tests and 1 test that controls the
00052  * permutation; on average, there should be 6 tests executed and 3 of them
00053  * should be mispredicted.
00054  * ------------------------------------------------------------------------
00055  */
00056 
00057 #define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
00058 
00059 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00060 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00061 
00062 #define TST1_LEAVE U1++; }
00063 #define TST2_LEAVE U2++; }
00064 
00065 #define ONE_ITERATION                                   \
00066                                                         \
00067     PTEST = PT1 >> 20;                                  \
00068                                                         \
00069     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00070     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00071     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00072                                                         \
00073     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00074     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00075     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00076                                                         \
00077     PTX = (PT1 >> 18) & 7;                              \
00078     PT1 &= 0x1FFF;                                      \
00079     PT2 &= 0x1FFF;                                      \
00080     CLK = (int) mbedtls_timing_hardclock();                            \
00081                                                         \
00082     i = 0;                                              \
00083     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
00084     B = &WALK[PT2    ]; RES[i++] ^= *B;                 \
00085     C = &WALK[PT1 ^ 1]; RES[i++] ^= *C;                 \
00086     D = &WALK[PT2 ^ 4]; RES[i++] ^= *D;                 \
00087                                                         \
00088     IN = (*A >> (1)) ^ (*A << (31)) ^ CLK;              \
00089     *A = (*B >> (2)) ^ (*B << (30)) ^ CLK;              \
00090     *B = IN ^ U1;                                       \
00091     *C = (*C >> (3)) ^ (*C << (29)) ^ CLK;              \
00092     *D = (*D >> (4)) ^ (*D << (28)) ^ CLK;              \
00093                                                         \
00094     A = &WALK[PT1 ^ 2]; RES[i++] ^= *A;                 \
00095     B = &WALK[PT2 ^ 2]; RES[i++] ^= *B;                 \
00096     C = &WALK[PT1 ^ 3]; RES[i++] ^= *C;                 \
00097     D = &WALK[PT2 ^ 6]; RES[i++] ^= *D;                 \
00098                                                         \
00099     if( PTEST & 1 ) SWAP( A, C );                       \
00100                                                         \
00101     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
00102     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
00103     *B = IN; CLK = (int) mbedtls_timing_hardclock();                   \
00104     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
00105     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
00106                                                         \
00107     A = &WALK[PT1 ^ 4];                                 \
00108     B = &WALK[PT2 ^ 1];                                 \
00109                                                         \
00110     PTEST = PT2 >> 1;                                   \
00111                                                         \
00112     PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]);   \
00113     PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8);  \
00114     PTY = (PT2 >> 10) & 7;                              \
00115                                                         \
00116     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00117     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00118     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00119                                                         \
00120     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00121     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00122     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00123                                                         \
00124     C = &WALK[PT1 ^ 5];                                 \
00125     D = &WALK[PT2 ^ 5];                                 \
00126                                                         \
00127     RES[i++] ^= *A;                                     \
00128     RES[i++] ^= *B;                                     \
00129     RES[i++] ^= *C;                                     \
00130     RES[i++] ^= *D;                                     \
00131                                                         \
00132     IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK;             \
00133     *A = (*B >> (10)) ^ (*B << (22)) ^ CLK;             \
00134     *B = IN ^ U2;                                       \
00135     *C = (*C >> (11)) ^ (*C << (21)) ^ CLK;             \
00136     *D = (*D >> (12)) ^ (*D << (20)) ^ CLK;             \
00137                                                         \
00138     A = &WALK[PT1 ^ 6]; RES[i++] ^= *A;                 \
00139     B = &WALK[PT2 ^ 3]; RES[i++] ^= *B;                 \
00140     C = &WALK[PT1 ^ 7]; RES[i++] ^= *C;                 \
00141     D = &WALK[PT2 ^ 7]; RES[i++] ^= *D;                 \
00142                                                         \
00143     IN = (*A >> (13)) ^ (*A << (19)) ^ CLK;             \
00144     *A = (*B >> (14)) ^ (*B << (18)) ^ CLK;             \
00145     *B = IN;                                            \
00146     *C = (*C >> (15)) ^ (*C << (17)) ^ CLK;             \
00147     *D = (*D >> (16)) ^ (*D << (16)) ^ CLK;             \
00148                                                         \
00149     PT1 = ( RES[( i - 8 ) ^ PTX] ^                      \
00150             WALK[PT1 ^ PTX ^ 7] ) & (~1);               \
00151     PT1 ^= (PT2 ^ 0x10) & 0x10;                         \
00152                                                         \
00153     for( n++, i = 0; i < 16; i++ )                      \
00154         hs->pool[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
00155 
00156 /*
00157  * Entropy gathering function
00158  */
00159 static void havege_fill( mbedtls_havege_state *hs )
00160 {
00161     int i, n = 0;
00162     int  U1,  U2, *A, *B, *C, *D;
00163     int PT1, PT2, *WALK, RES[16];
00164     int PTX, PTY, CLK, PTEST, IN;
00165 
00166     WALK = hs->WALK;
00167     PT1  = hs->PT1;
00168     PT2  = hs->PT2;
00169 
00170     PTX  = U1 = 0;
00171     PTY  = U2 = 0;
00172 
00173     (void)PTX;
00174 
00175     memset( RES, 0, sizeof( RES ) );
00176 
00177     while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
00178     {
00179         ONE_ITERATION
00180         ONE_ITERATION
00181         ONE_ITERATION
00182         ONE_ITERATION
00183     }
00184 
00185     hs->PT1 = PT1;
00186     hs->PT2 = PT2;
00187 
00188     hs->offset[0] = 0;
00189     hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
00190 }
00191 
00192 /*
00193  * HAVEGE initialization
00194  */
00195 void mbedtls_havege_init( mbedtls_havege_state *hs )
00196 {
00197     memset( hs, 0, sizeof( mbedtls_havege_state ) );
00198 
00199     havege_fill( hs );
00200 }
00201 
00202 void mbedtls_havege_free( mbedtls_havege_state *hs )
00203 {
00204     if( hs == NULL )
00205         return;
00206 
00207     mbedtls_platform_zeroize( hs, sizeof( mbedtls_havege_state ) );
00208 }
00209 
00210 /*
00211  * HAVEGE rand function
00212  */
00213 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
00214 {
00215     int val;
00216     size_t use_len;
00217     mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
00218     unsigned char *p = buf;
00219 
00220     while( len > 0 )
00221     {
00222         use_len = len;
00223         if( use_len > sizeof(int) )
00224             use_len = sizeof(int);
00225 
00226         if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
00227             havege_fill( hs );
00228 
00229         val  = hs->pool[hs->offset[0]++];
00230         val ^= hs->pool[hs->offset[1]++];
00231 
00232         memcpy( p, &val, use_len );
00233 
00234         len -= use_len;
00235         p += use_len;
00236     }
00237 
00238     return( 0 );
00239 }
00240 
00241 #endif /* MBEDTLS_HAVEGE_C */