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  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: GPL-2.0
  6.  *
  7.  *  This program is free software; you can redistribute it and/or modify
  8.  *  it under the terms of the GNU General Public License as published by
  9.  *  the Free Software Foundation; either version 2 of the License, or
  10.  *  (at your option) any later version.
  11.  *
  12.  *  This program is distributed in the hope that it will be useful,
  13.  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15.  *  GNU General Public License for more details.
  16.  *
  17.  *  You should have received a copy of the GNU General Public License along
  18.  *  with this program; if not, write to the Free Software Foundation, Inc.,
  19.  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20.  *
  21.  *  This file is part of mbed TLS (https://tls.mbed.org)
  22.  */
  23. /*
  24.  *  The HAVEGE RNG was designed by Andre Seznec in 2002.
  25.  *
  26.  *  http://www.irisa.fr/caps/projects/hipsor/publi.php
  27.  *
  28.  *  Contact: seznec(at)irisa_dot_fr - orocheco(at)irisa_dot_fr
  29.  */
  30.  
  31. #if !defined(MBEDTLS_CONFIG_FILE)
  32. #include "mbedtls/config.h"
  33. #else
  34. #include MBEDTLS_CONFIG_FILE
  35. #endif
  36.  
  37. #if defined(MBEDTLS_HAVEGE_C)
  38.  
  39. #include "mbedtls/havege.h"
  40. #include "mbedtls/timing.h"
  41. #include "mbedtls/platform_util.h"
  42.  
  43. #include <limits.h>
  44. #include <string.h>
  45.  
  46. /* If int isn't capable of storing 2^32 distinct values, the code of this
  47.  * module may cause a processor trap or a miscalculation. If int is more
  48.  * than 32 bits, the code may not calculate the intended values. */
  49. #if INT_MIN + 1 != -0x7fffffff
  50. #error "The HAVEGE module requires int to be exactly 32 bits, with INT_MIN = -2^31."
  51. #endif
  52. #if UINT_MAX != 0xffffffff
  53. #error "The HAVEGE module requires unsigned to be exactly 32 bits."
  54. #endif
  55.  
  56. /* ------------------------------------------------------------------------
  57.  * On average, one iteration accesses two 8-word blocks in the havege WALK
  58.  * table, and generates 16 words in the RES array.
  59.  *
  60.  * The data read in the WALK table is updated and permuted after each use.
  61.  * The result of the hardware clock counter read is used  for this update.
  62.  *
  63.  * 25 conditional tests are present.  The conditional tests are grouped in
  64.  * two nested  groups of 12 conditional tests and 1 test that controls the
  65.  * permutation; on average, there should be 6 tests executed and 3 of them
  66.  * should be mispredicted.
  67.  * ------------------------------------------------------------------------
  68.  */
  69.  
  70. #define SWAP(X,Y) { unsigned *T = (X); (X) = (Y); (Y) = T; }
  71.  
  72. #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
  73. #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
  74.  
  75. #define TST1_LEAVE U1++; }
  76. #define TST2_LEAVE U2++; }
  77.  
  78. #define ONE_ITERATION                                   \
  79.                                                         \
  80.     PTEST = PT1 >> 20;                                  \
  81.                                                         \
  82.     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
  83.     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
  84.     TST1_ENTER  TST1_ENTER  TST1_ENTER  TST1_ENTER      \
  85.                                                         \
  86.     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
  87.     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
  88.     TST1_LEAVE  TST1_LEAVE  TST1_LEAVE  TST1_LEAVE      \
  89.                                                         \
  90.     PTX = (PT1 >> 18) & 7;                              \
  91.     PT1 &= 0x1FFF;                                      \
  92.     PT2 &= 0x1FFF;                                      \
  93.     CLK = (unsigned) mbedtls_timing_hardclock();        \
  94.                                                         \
  95.     i = 0;                                              \
  96.     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
  97.     B = &WALK[PT2    ]; RES[i++] ^= *B;                 \
  98.     C = &WALK[PT1 ^ 1]; RES[i++] ^= *C;                 \
  99.     D = &WALK[PT2 ^ 4]; RES[i++] ^= *D;                 \
  100.                                                         \
  101.     IN = (*A >> (1)) ^ (*A << (31)) ^ CLK;              \
  102.     *A = (*B >> (2)) ^ (*B << (30)) ^ CLK;              \
  103.     *B = IN ^ U1;                                       \
  104.     *C = (*C >> (3)) ^ (*C << (29)) ^ CLK;              \
  105.     *D = (*D >> (4)) ^ (*D << (28)) ^ CLK;              \
  106.                                                         \
  107.     A = &WALK[PT1 ^ 2]; RES[i++] ^= *A;                 \
  108.     B = &WALK[PT2 ^ 2]; RES[i++] ^= *B;                 \
  109.     C = &WALK[PT1 ^ 3]; RES[i++] ^= *C;                 \
  110.     D = &WALK[PT2 ^ 6]; RES[i++] ^= *D;                 \
  111.                                                         \
  112.     if( PTEST & 1 ) SWAP( A, C );                       \
  113.                                                         \
  114.     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
  115.     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
  116.     *B = IN; CLK = (unsigned) mbedtls_timing_hardclock(); \
  117.     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
  118.     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
  119.                                                         \
  120.     A = &WALK[PT1 ^ 4];                                 \
  121.     B = &WALK[PT2 ^ 1];                                 \
  122.                                                         \
  123.     PTEST = PT2 >> 1;                                   \
  124.                                                         \
  125.     PT2 = (RES[(i - 8) ^ PTY] ^ WALK[PT2 ^ PTY ^ 7]);   \
  126.     PT2 = ((PT2 & 0x1FFF) & (~8)) ^ ((PT1 ^ 8) & 0x8);  \
  127.     PTY = (PT2 >> 10) & 7;                              \
  128.                                                         \
  129.     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
  130.     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
  131.     TST2_ENTER  TST2_ENTER  TST2_ENTER  TST2_ENTER      \
  132.                                                         \
  133.     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
  134.     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
  135.     TST2_LEAVE  TST2_LEAVE  TST2_LEAVE  TST2_LEAVE      \
  136.                                                         \
  137.     C = &WALK[PT1 ^ 5];                                 \
  138.     D = &WALK[PT2 ^ 5];                                 \
  139.                                                         \
  140.     RES[i++] ^= *A;                                     \
  141.     RES[i++] ^= *B;                                     \
  142.     RES[i++] ^= *C;                                     \
  143.     RES[i++] ^= *D;                                     \
  144.                                                         \
  145.     IN = (*A >> ( 9)) ^ (*A << (23)) ^ CLK;             \
  146.     *A = (*B >> (10)) ^ (*B << (22)) ^ CLK;             \
  147.     *B = IN ^ U2;                                       \
  148.     *C = (*C >> (11)) ^ (*C << (21)) ^ CLK;             \
  149.     *D = (*D >> (12)) ^ (*D << (20)) ^ CLK;             \
  150.                                                         \
  151.     A = &WALK[PT1 ^ 6]; RES[i++] ^= *A;                 \
  152.     B = &WALK[PT2 ^ 3]; RES[i++] ^= *B;                 \
  153.     C = &WALK[PT1 ^ 7]; RES[i++] ^= *C;                 \
  154.     D = &WALK[PT2 ^ 7]; RES[i++] ^= *D;                 \
  155.                                                         \
  156.     IN = (*A >> (13)) ^ (*A << (19)) ^ CLK;             \
  157.     *A = (*B >> (14)) ^ (*B << (18)) ^ CLK;             \
  158.     *B = IN;                                            \
  159.     *C = (*C >> (15)) ^ (*C << (17)) ^ CLK;             \
  160.     *D = (*D >> (16)) ^ (*D << (16)) ^ CLK;             \
  161.                                                         \
  162.     PT1 = ( RES[( i - 8 ) ^ PTX] ^                      \
  163.             WALK[PT1 ^ PTX ^ 7] ) & (~1);               \
  164.     PT1 ^= (PT2 ^ 0x10) & 0x10;                         \
  165.                                                         \
  166.     for( n++, i = 0; i < 16; i++ )                      \
  167.         POOL[n % MBEDTLS_HAVEGE_COLLECT_SIZE] ^= RES[i];
  168.  
  169. /*
  170.  * Entropy gathering function
  171.  */
  172. static void havege_fill( mbedtls_havege_state *hs )
  173. {
  174.     unsigned i, n = 0;
  175.     unsigned  U1,  U2, *A, *B, *C, *D;
  176.     unsigned PT1, PT2, *WALK, *POOL, RES[16];
  177.     unsigned PTX, PTY, CLK, PTEST, IN;
  178.  
  179.     WALK = (unsigned *) hs->WALK;
  180.     POOL = (unsigned *) hs->pool;
  181.     PT1  = hs->PT1;
  182.     PT2  = hs->PT2;
  183.  
  184.     PTX  = U1 = 0;
  185.     PTY  = U2 = 0;
  186.  
  187.     (void)PTX;
  188.  
  189.     memset( RES, 0, sizeof( RES ) );
  190.  
  191.     while( n < MBEDTLS_HAVEGE_COLLECT_SIZE * 4 )
  192.     {
  193.         ONE_ITERATION
  194.         ONE_ITERATION
  195.         ONE_ITERATION
  196.         ONE_ITERATION
  197.     }
  198.  
  199.     hs->PT1 = PT1;
  200.     hs->PT2 = PT2;
  201.  
  202.     hs->offset[0] = 0;
  203.     hs->offset[1] = MBEDTLS_HAVEGE_COLLECT_SIZE / 2;
  204. }
  205.  
  206. /*
  207.  * HAVEGE initialization
  208.  */
  209. void mbedtls_havege_init( mbedtls_havege_state *hs )
  210. {
  211.     memset( hs, 0, sizeof( mbedtls_havege_state ) );
  212.  
  213.     havege_fill( hs );
  214. }
  215.  
  216. void mbedtls_havege_free( mbedtls_havege_state *hs )
  217. {
  218.     if( hs == NULL )
  219.         return;
  220.  
  221.     mbedtls_platform_zeroize( hs, sizeof( mbedtls_havege_state ) );
  222. }
  223.  
  224. /*
  225.  * HAVEGE rand function
  226.  */
  227. int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
  228. {
  229.     int val;
  230.     size_t use_len;
  231.     mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
  232.     unsigned char *p = buf;
  233.  
  234.     while( len > 0 )
  235.     {
  236.         use_len = len;
  237.         if( use_len > sizeof(int) )
  238.             use_len = sizeof(int);
  239.  
  240.         if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
  241.             havege_fill( hs );
  242.  
  243.         val  = hs->pool[hs->offset[0]++];
  244.         val ^= hs->pool[hs->offset[1]++];
  245.  
  246.         memcpy( p, &val, use_len );
  247.  
  248.         len -= use_len;
  249.         p += use_len;
  250.     }
  251.  
  252.     return( 0 );
  253. }
  254.  
  255. #endif /* MBEDTLS_HAVEGE_C */
  256.