1/* rndhw.c  - Access to the external random daemon
2 * Copyright (C) 2007  Free Software Foundation, Inc.
3 *
4 * This file is part of Libgcrypt.
5 *
6 * Libgcrypt is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU Lesser General Public License as
8 * published by the Free Software Foundation; either version 2.1 of
9 * the License, or (at your option) any later version.
10 *
11 * Libgcrypt is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
18 */
19
20#include <config.h>
21#include <stdio.h>
22#include <stdlib.h>
23
24#include "types.h"
25#include "g10lib.h"
26#include "rand-internal.h"
27
28#undef USE_PADLOCK
29#ifdef ENABLE_PADLOCK_SUPPORT
30# if defined (__i386__) && SIZEOF_UNSIGNED_LONG == 4 && defined (__GNUC__)
31# define USE_PADLOCK
32# endif
33#endif /*ENABLE_PADLOCK_SUPPORT*/
34
35/* Keep track on whether the RNG has problems.  */
36static volatile int rng_failed;
37
38
39#ifdef USE_PADLOCK
40static size_t
41poll_padlock (void (*add)(const void*, size_t, enum random_origins),
42              enum random_origins origin, int fast)
43{
44  volatile char buffer[64+8] __attribute__ ((aligned (8)));
45  volatile char *p;
46  unsigned int nbytes, status;
47
48  /* Peter Gutmann's cryptlib tests again whether the RNG is enabled
49     but we don't do so.  We would have to do this also for our AES
50     implementaion and that is definitely too time consuming.  There
51     would be a race condition anyway.  Thus we assume that the OS
52     does not change the Padlock initialization while a user process
53     is running.  */
54  p = buffer;
55  nbytes = 0;
56  while (nbytes < 64)
57    {
58      asm volatile
59        ("movl %1, %%edi\n\t"         /* Set buffer.  */
60         "xorl %%edx, %%edx\n\t"      /* Request up to 8 bytes.  */
61         ".byte 0x0f, 0xa7, 0xc0\n\t" /* XSTORE RNG. */
62         : "=a" (status)
63         : "g" (p)
64         : "%edx", "%edi", "cc"
65         );
66      if ((status & (1<<6))         /* RNG still enabled.  */
67          && !(status & (1<<13))    /* von Neumann corrector is enabled.  */
68          && !(status & (1<<14))    /* String filter is disabled.  */
69          && !(status & 0x1c00)     /* BIAS voltage at default.  */
70          && (!(status & 0x1f) || (status & 0x1f) == 8) /* Sanity check.  */
71          )
72        {
73          nbytes += (status & 0x1f);
74          if (fast)
75            break; /* Don't get into the loop with the fast flag set.  */
76          p += (status & 0x1f);
77        }
78      else
79        {
80          /* If there was an error we need to break the loop and
81             record that there is something wrong with the padlock
82             RNG.  */
83          rng_failed = 1;
84          break;
85        }
86    }
87
88  if (nbytes)
89    {
90      (*add) ((void*)buffer, nbytes, origin);
91      wipememory (buffer, nbytes);
92    }
93  return nbytes;
94}
95#endif /*USE_PADLOCK*/
96
97
98int
99_gcry_rndhw_failed_p (void)
100{
101  return rng_failed;
102}
103
104
105/* Try to read random from a hardware RNG if a fast one is
106   available.  */
107void
108_gcry_rndhw_poll_fast (void (*add)(const void*, size_t, enum random_origins),
109                       enum random_origins origin)
110{
111  (void)add;
112  (void)origin;
113
114#ifdef USE_PADLOCK
115  if ((_gcry_get_hw_features () & HWF_PADLOCK_RNG))
116    poll_padlock (add, origin, 1);
117#endif
118}
119
120
121/* Read 64 bytes from a hardware RNG and return the number of bytes
122   actually read.  */
123size_t
124_gcry_rndhw_poll_slow (void (*add)(const void*, size_t, enum random_origins),
125                       enum random_origins origin)
126{
127  size_t nbytes = 0;
128
129  (void)add;
130  (void)origin;
131
132#ifdef USE_PADLOCK
133  if ((_gcry_get_hw_features () & HWF_PADLOCK_RNG))
134    nbytes += poll_padlock (add, origin, 0);
135#endif
136
137  return nbytes;
138}
139