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
|
/*-------------------------------------------------------------------------
*
* pg_strong_random.c
* generate a cryptographically secure random number
*
* Our definition of "strong" is that it's suitable for generating random
* salts and query cancellation keys, during authentication.
*
* Note: this code is run quite early in postmaster and backend startup;
* therefore, even when built for backend, it cannot rely on backend
* infrastructure such as elog() or palloc().
*
* Copyright (c) 1996-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/port/pg_strong_random.c
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>
/*
* pg_strong_random & pg_strong_random_init
*
* Generate requested number of random bytes. The returned bytes are
* cryptographically secure, suitable for use e.g. in authentication.
*
* Before pg_strong_random is called in any process, the generator must first
* be initialized by calling pg_strong_random_init().
*
* We rely on system facilities for actually generating the numbers.
* We support a number of sources:
*
* 1. OpenSSL's RAND_bytes()
* 2. Windows' CryptGenRandom() function
* 3. /dev/urandom
*
* Returns true on success, and false if none of the sources
* were available. NB: It is important to check the return value!
* Proceeding with key generation when no random data was available
* would lead to predictable keys and security issues.
*/
#ifdef USE_OPENSSL
#include <openssl/rand.h>
void
pg_strong_random_init(void)
{
/*
* Make sure processes do not share OpenSSL randomness state. This is no
* longer required in OpenSSL 1.1.1 and later versions, but until we drop
* support for version < 1.1.1 we need to do this.
*/
RAND_poll();
}
bool
pg_strong_random(void *buf, size_t len)
{
int i;
/*
* Check that OpenSSL's CSPRNG has been sufficiently seeded, and if not
* add more seed data using RAND_poll(). With some older versions of
* OpenSSL, it may be necessary to call RAND_poll() a number of times. If
* RAND_poll() fails to generate seed data within the given amount of
* retries, subsequent RAND_bytes() calls will fail, but we allow that to
* happen to let pg_strong_random() callers handle that with appropriate
* error handling.
*/
#define NUM_RAND_POLL_RETRIES 8
for (i = 0; i < NUM_RAND_POLL_RETRIES; i++)
{
if (RAND_status() == 1)
{
/* The CSPRNG is sufficiently seeded */
break;
}
RAND_poll();
}
if (RAND_bytes(buf, len) == 1)
return true;
return false;
}
#elif WIN32
#include <wincrypt.h>
/*
* Cache a global crypto provider that only gets freed when the process
* exits, in case we need random numbers more than once.
*/
static HCRYPTPROV hProvider = 0;
void
pg_strong_random_init(void)
{
/* No initialization needed on WIN32 */
}
bool
pg_strong_random(void *buf, size_t len)
{
if (hProvider == 0)
{
if (!CryptAcquireContext(&hProvider,
NULL,
MS_DEF_PROV,
PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
{
/*
* On failure, set back to 0 in case the value was for some reason
* modified.
*/
hProvider = 0;
}
}
/* Re-check in case we just retrieved the provider */
if (hProvider != 0)
{
if (CryptGenRandom(hProvider, len, buf))
return true;
}
return false;
}
#else /* not USE_OPENSSL or WIN32 */
/*
* Without OpenSSL or Win32 support, just read /dev/urandom ourselves.
*/
void
pg_strong_random_init(void)
{
/* No initialization needed */
}
bool
pg_strong_random(void *buf, size_t len)
{
int f;
char *p = buf;
ssize_t res;
f = open("/dev/urandom", O_RDONLY, 0);
if (f == -1)
return false;
while (len)
{
res = read(f, p, len);
if (res <= 0)
{
if (errno == EINTR)
continue; /* interrupted by signal, just retry */
close(f);
return false;
}
p += res;
len -= res;
}
close(f);
return true;
}
#endif
|
