havege.c

00001 /**
00002  *  \brief HAVEGE: HArdware Volatile Entropy Gathering and Expansion
00003  *
00004  *  Copyright (C) 2006-2014, ARM Limited, All Rights Reserved
00005  *
00006  *  This file is part of mbed TLS (https://tls.mbed.org)
00007  *
00008  *  This program is free software; you can redistribute it and/or modify
00009  *  it under the terms of the GNU General Public License as published by
00010  *  the Free Software Foundation; either version 2 of the License, or
00011  *  (at your option) any later version.
00012  *
00013  *  This program is distributed in the hope that it will be useful,
00014  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00016  *  GNU General Public License for more details.
00017  *
00018  *  You should have received a copy of the GNU General Public License along
00019  *  with this program; if not, write to the Free Software Foundation, Inc.,
00020  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
00021  */
00022 /*
00023  *  The HAVEGE RNG was designed by Andre Seznec in 2002.
00024  *
00025  *  http://www.irisa.fr/caps/projects/hipsor/publi.php
00026  *
00027  *  Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
00028  */
00029 
00030 #if !defined(POLARSSL_CONFIG_FILE)
00031 #include "polarssl/config.h"
00032 #else
00033 #include POLARSSL_CONFIG_FILE
00034 #endif
00035 
00036 #if defined(POLARSSL_HAVEGE_C)
00037 
00038 #include "polarssl/havege.h"
00039 #include "polarssl/timing.h"
00040 
00041 #include <string.h>
00042 
00043 /* Implementation that should never be optimized out by the compiler */
00044 static void polarssl_zeroize( void *v, size_t n ) {
00045     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
00046 }
00047 
00048 /* ------------------------------------------------------------------------
00049  * On average, one iteration accesses two 8-word blocks in the havege WALK
00050  * table, and generates 16 words in the RES array.
00051  *
00052  * The data read in the WALK table is updated and permuted after each use.
00053  * The result of the hardware clock counter read is used  for this update.
00054  *
00055  * 25 conditional tests are present.  The conditional tests are grouped in
00056  * two nested  groups of 12 conditional tests and 1 test that controls the
00057  * permutation; on average, there should be 6 tests executed and 3 of them
00058  * should be mispredicted.
00059  * ------------------------------------------------------------------------
00060  */
00061 
00062 #define SWAP(X,Y) { int *T = X; X = Y; Y = T; }
00063 
00064 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00065 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
00066 
00067 #define TST1_LEAVE U1++; }
00068 #define TST2_LEAVE U2++; }
00069 
00070 #define ONE_ITERATION                                   \
00071                                                         \
00072     PTEST = PT1 >> 20;                                  \
00073                                                         \
00074     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00075     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00076     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
00077                                                         \
00078     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00079     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00080     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
00081                                                         \
00082     PTX = (PT1 >> 18) & 7;                              \
00083     PT1 &= 0x1FFF;                                      \
00084     PT2 &= 0x1FFF;                                      \
00085     CLK = (int) hardclock();                            \
00086                                                         \
00087     i = 0;                                              \
00088     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
00089     B = &WALK[PT2    ]; RES[i++] ^= *B;                 \
00090     C = &WALK[PT1 ^ 1]; RES[i++] ^= *C;                 \
00091     D = &WALK[PT2 ^ 4]; RES[i++] ^= *D;                 \
00092                                                         \
00093     IN = (*A >> (1)) ^ (*A << (31)) ^ CLK;              \
00094     *A = (*B >> (2)) ^ (*B << (30)) ^ CLK;              \
00095     *B = IN ^ U1;                                       \
00096     *C = (*C >> (3)) ^ (*C << (29)) ^ CLK;              \
00097     *D = (*D >> (4)) ^ (*D << (28)) ^ CLK;              \
00098                                                         \
00099     A = &WALK[PT1 ^ 2]; RES[i++] ^= *A;                 \
00100     B = &WALK[PT2 ^ 2]; RES[i++] ^= *B;                 \
00101     C = &WALK[PT1 ^ 3]; RES[i++] ^= *C;                 \
00102     D = &WALK[PT2 ^ 6]; RES[i++] ^= *D;                 \
00103                                                         \
00104     if( PTEST & 1 ) SWAP( A, C );                       \
00105                                                         \
00106     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
00107     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
00108     *B = IN; CLK = (int) hardclock();                   \
00109     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
00110     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
00111                                                         \
00112     A = &WALK[PT1 ^ 4];                                 \
00113     B = &WALK[PT2 ^ 1];                                 \
00114                                                         \
00115     PTEST = PT2 >> 1;                                   \
00116                                                         \
00117     PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]);   \
00118     PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8);  \
00119     PTY = (PT2 >> 10) & 7;                              \
00120                                                         \
00121     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00122     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00123     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
00124                                                         \
00125     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00126     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00127     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
00128                                                         \
00129     C = &WALK[PT1 ^ 5];                                 \
00130     D = &WALK[PT2 ^ 5];                                 \
00131                                                         \
00132     RES[i++] ^= *A;                                     \
00133     RES[i++] ^= *B;                                     \
00134     RES[i++] ^= *C;                                     \
00135     RES[i++] ^= *D;                                     \
00136                                                         \
00137     IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK;             \
00138     *A = (*B >> (10)) ^ (*B << (22)) ^ CLK;             \
00139     *B = IN ^ U2;                                       \
00140     *C = (*C >> (11)) ^ (*C << (21)) ^ CLK;             \
00141     *D = (*D >> (12)) ^ (*D << (20)) ^ CLK;             \
00142                                                         \
00143     A = &WALK[PT1 ^ 6]; RES[i++] ^= *A;                 \
00144     B = &WALK[PT2 ^ 3]; RES[i++] ^= *B;                 \
00145     C = &WALK[PT1 ^ 7]; RES[i++] ^= *C;                 \
00146     D = &WALK[PT2 ^ 7]; RES[i++] ^= *D;                 \
00147                                                         \
00148     IN = (*A >> (13)) ^ (*A << (19)) ^ CLK;             \
00149     *A = (*B >> (14)) ^ (*B << (18)) ^ CLK;             \
00150     *B = IN;                                            \
00151     *C = (*C >> (15)) ^ (*C << (17)) ^ CLK;             \
00152     *D = (*D >> (16)) ^ (*D << (16)) ^ CLK;             \
00153                                                         \
00154     PT1 = ( RES[( i - 8 ) ^ PTX] ^                      \
00155             WALK[PT1 ^ PTX ^ 7] ) & (~1);               \
00156     PT1 ^= (PT2 ^ 0x10) & 0x10;                         \
00157                                                         \
00158     for( n++, i = 0; i < 16; i++ )                      \
00159         hs->pool[n % COLLECT_SIZE] ^= RES[i];
00160 
00161 /*
00162  * Entropy gathering function
00163  */
00164 static void havege_fill( havege_state *hs )
00165 {
00166     int i, n = 0;
00167     int  U1,  U2, *A, *B, *C, *D;
00168     int PT1, PT2, *WALK, RES[16];
00169     int PTX, PTY, CLK, PTEST, IN;
00170 
00171     WALK = hs->WALK;
00172     PT1  = hs->PT1;
00173     PT2  = hs->PT2;
00174 
00175     PTX  = U1 = 0;
00176     PTY  = U2 = 0;
00177 
00178     memset( RES, 0, sizeof( RES ) );
00179 
00180     while( n < COLLECT_SIZE * 4 )
00181     {
00182         ONE_ITERATION
00183         ONE_ITERATION
00184         ONE_ITERATION
00185         ONE_ITERATION
00186     }
00187 
00188     hs->PT1 = PT1;
00189     hs->PT2 = PT2;
00190 
00191     hs->offset[0] = 0;
00192     hs->offset[1] = COLLECT_SIZE / 2;
00193 }
00194 
00195 /*
00196  * HAVEGE initialization
00197  */
00198 void havege_init( havege_state *hs )
00199 {
00200     memset( hs, 0, sizeof( havege_state ) );
00201 
00202     havege_fill( hs );
00203 }
00204 
00205 void havege_free( havege_state *hs )
00206 {
00207     if( hs == NULL )
00208         return;
00209 
00210     polarssl_zeroize( hs, sizeof( havege_state ) );
00211 }
00212 
00213 /*
00214  * HAVEGE rand function
00215  */
00216 int havege_random( void *p_rng, unsigned char *buf, size_t len )
00217 {
00218     int val;
00219     size_t use_len;
00220     havege_state *hs = (havege_state *) p_rng;
00221     unsigned char *p = buf;
00222 
00223     while( len > 0 )
00224     {
00225         use_len = len;
00226         if( use_len > sizeof(int) )
00227             use_len = sizeof(int);
00228 
00229         if( hs->offset[1] >= COLLECT_SIZE )
00230             havege_fill( hs );
00231 
00232         val  = hs->pool[hs->offset[0]++];
00233         val ^= hs->pool[hs->offset[1]++];
00234 
00235         memcpy( p, &val, use_len );
00236 
00237         len -= use_len;
00238         p += use_len;
00239     }
00240 
00241     return( 0 );
00242 }
00243 
00244 #endif /* POLARSSL_HAVEGE_C */
00245