Make Rules.mk more compatible with merges and local diffs.
[BearSSL] / src / rand / sysrng.c
1 /*
2 * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #define BR_ENABLE_INTRINSICS 1
26 #include "inner.h"
27
28 #if BR_USE_URANDOM
29 #include <sys/types.h>
30 #include <unistd.h>
31 #include <fcntl.h>
32 #include <errno.h>
33 #endif
34
35 #if BR_USE_WIN32_RAND
36 #include <windows.h>
37 #include <wincrypt.h>
38 #pragma comment(lib, "advapi32")
39 #endif
40
41 #if BR_RDRAND
42 BR_TARGETS_X86_UP
43 BR_TARGET("rdrnd")
44 static int
45 seeder_rdrand(const br_prng_class **ctx)
46 {
47 unsigned char tmp[32];
48 size_t u;
49
50 for (u = 0; u < sizeof tmp; u += sizeof(uint32_t)) {
51 int j;
52 uint32_t x;
53
54 /*
55 * We use the 32-bit intrinsic so that code is compatible
56 * with both 32-bit and 64-bit architectures.
57 *
58 * Intel recommends trying at least 10 times in case of
59 * failure.
60 */
61 for (j = 0; j < 10; j ++) {
62 if (_rdrand32_step(&x)) {
63 goto next_word;
64 }
65 }
66 return 0;
67 next_word:
68 br_enc32le(tmp + u, x);
69 }
70 (*ctx)->update(ctx, tmp, sizeof tmp);
71 return 1;
72 }
73 BR_TARGETS_X86_DOWN
74
75 static int
76 rdrand_supported(void)
77 {
78 /*
79 * The RDRND support is bit 30 of ECX, as returned by CPUID.
80 */
81 return br_cpuid(0, 0, 0x40000000, 0);
82 }
83
84 #endif
85
86 #if BR_USE_URANDOM
87 static int
88 seeder_urandom(const br_prng_class **ctx)
89 {
90 int f;
91
92 f = open("/dev/urandom", O_RDONLY);
93 if (f >= 0) {
94 unsigned char tmp[32];
95 size_t u;
96
97 for (u = 0; u < sizeof tmp;) {
98 ssize_t len;
99
100 len = read(f, tmp + u, (sizeof tmp) - u);
101 if (len < 0) {
102 if (errno == EINTR) {
103 continue;
104 }
105 break;
106 }
107 u += (size_t)len;
108 }
109 close(f);
110 if (u == sizeof tmp) {
111 (*ctx)->update(ctx, tmp, sizeof tmp);
112 return 1;
113 }
114 }
115 return 0;
116 }
117 #endif
118
119 #if BR_USE_WIN32_RAND
120 static int
121 seeder_win32(const br_prng_class **ctx)
122 {
123 HCRYPTPROV hp;
124
125 if (CryptAcquireContext(&hp, 0, 0, PROV_RSA_FULL,
126 CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
127 {
128 BYTE buf[32];
129 BOOL r;
130
131 r = CryptGenRandom(hp, sizeof buf, buf);
132 CryptReleaseContext(hp, 0);
133 if (r) {
134 (*ctx)->update(ctx, buf, sizeof buf);
135 return 1;
136 }
137 }
138 return 0;
139 }
140 #endif
141
142 /* see bearssl_rand.h.h */
143 br_prng_seeder
144 br_prng_seeder_system(const char **name)
145 {
146 #if BR_RDRAND
147 if (rdrand_supported()) {
148 if (name != NULL) {
149 *name = "rdrand";
150 }
151 return &seeder_rdrand;
152 }
153 #endif
154 #if BR_USE_URANDOM
155 if (name != NULL) {
156 *name = "urandom";
157 }
158 return &seeder_urandom;
159 #elif BR_USE_WIN32_RAND
160 if (name != NULL) {
161 *name = "win32";
162 }
163 return &seeder_win32;
164 #endif
165 if (name != NULL) {
166 *name = "none";
167 }
168 return 0;
169 }