1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
/*
* Copyright (C) 2001, 2002 by the Massachusetts Institute of Technology.
* All rights reserved.
*
*
* Export of this software from the United States of America may require
* a specific license from the United States Government. It is the
* responsibility of any person or organization contemplating export to
* obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#include "k5-int.h"
#include "enc_provider.h"
#include <assert.h>
#include "yarrow.h"
static Yarrow_CTX y_ctx;
static int inited=0;
/* Helper function to estimate entropy based on sample length
* and where it comes from.
*/
static size_t
entropy_estimate (unsigned int randsource, size_t length)
{
switch (randsource) {
case KRB5_C_RANDSOURCE_OLDAPI:
return (4*length);
case KRB5_C_RANDSOURCE_OSRAND:
return (8*length);
case KRB5_C_RANDSOURCE_TRUSTEDPARTY:
return (4*length);
case KRB5_C_RANDSOURCE_TIMING:return (2);
case KRB5_C_RANDSOURCE_EXTERNAL_PROTOCOL:
return (0);
default:
abort();
}
return (0);
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_add_entropy (krb5_context context, unsigned int randsource,
const krb5_data *data)
{
int yerr;
if (inited == 0) {
unsigned i;
yerr = krb5int_yarrow_init (&y_ctx, NULL);
if ((yerr != YARROW_OK) && (yerr != YARROW_NOT_SEEDED))
return (KRB5_CRYPTO_INTERNAL);
for (i=0; i < KRB5_C_RANDSOURCE_MAX; i++ ) {
unsigned source_id;
if (krb5int_yarrow_new_source (&y_ctx, &source_id) != YARROW_OK )
return KRB5_CRYPTO_INTERNAL;
assert (source_id == i);
}
inited=1;
}
yerr = krb5int_yarrow_input (&y_ctx, randsource,
data->data, data->length,
entropy_estimate (randsource, data->length));
if (yerr != YARROW_OK)
return (KRB5_CRYPTO_INTERNAL);
return (0);
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_seed
(krb5_context context, krb5_data *data)
{
return (krb5_c_random_add_entropy (context, KRB5_C_RANDSOURCE_OLDAPI, data));
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_make_octets(krb5_context context, krb5_data *data)
{
int yerr;
assert (inited);
yerr = krb5int_yarrow_output (&y_ctx, data->data, data->length);
if (yerr == YARROW_NOT_SEEDED) {
yerr = krb5int_yarrow_reseed (&y_ctx, YARROW_SLOW_POOL);
if (yerr == YARROW_OK)
yerr = krb5int_yarrow_output (&y_ctx, data->data, data->length);
}
if ( yerr != YARROW_OK)
return (KRB5_CRYPTO_INTERNAL);
return(0);
}
void prng_cleanup (void)
{
if (inited) krb5int_yarrow_final (&y_ctx);
inited = 0;
}
/*
* Routines to get entropy from the OS. For UNIX we try /dev/urandom
* and /dev/random. Currently we don't do anything for Windows.
*/
#if defined(_WIN32)
krb5_error_code KRB5_CALLCONV
krb5_c_random_os_entropy (
krb5_context context, int strong, int *success)
{
if (success)
*success = 0;
return 0;
}
#else /*Windows*/
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
/*
* Helper function to read entropy from a random device. Takes the
* name of a device, opens it, makes sure it is a device and if so,
* reads entropy. Returns a boolean indicating whether entropy was
* read.
*/
static int
read_entropy_from_device (krb5_context context, const char *device)
{
krb5_data data;
struct stat sb;
int fd;
unsigned char buf[YARROW_SLOW_THRESH/8];
int left;
fd = open (device, O_RDONLY);
if (fd == -1)
return 0;
if (fstat (fd, &sb) == -1)
return 0;
if (S_ISREG(sb.st_mode)) {
close(fd);
return 0;
}
for (left = sizeof (buf); left > 0;) {
size_t count;
count = read (fd, &buf, (unsigned) left);
if (count <= 0) {
close(fd);
return 0;
}
left -= count;
}
close (fd);
data.length = sizeof (buf);
data.data = ( char * ) buf;
if ( krb5_c_random_add_entropy (context, KRB5_C_RANDSOURCE_OSRAND,
&data) != 0) {
return 0;
}
return 1;
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_os_entropy (krb5_context context,
int strong, int *success)
{
int unused;
int *oursuccess = success?success:&unused;
*oursuccess = 0;
/* If we are getting strong data then try that first. We aare
guaranteed to cause a reseed of some kind if strong is true and
we have both /dev/random and /dev/urandom. We want the strong
data included in the reseed so we get it first.*/
if (strong) {
if (read_entropy_from_device (context, "/dev/random"))
*oursuccess = 1;
}
if (read_entropy_from_device (context, "/dev/urandom"))
*oursuccess = 1;
return 0;
}
#endif /*Windows or pre-OSX Mac*/
|
