1 /* Copyright (c) 2014, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include <openssl/rand.h>
16
17 #include <assert.h>
18 #include <limits.h>
19 #include <string.h>
20
21 #include <openssl/chacha.h>
22 #include <openssl/cpu.h>
23 #include <openssl/mem.h>
24
25 #include "internal.h"
26 #include "../internal.h"
27
28
29 /* It's assumed that the operating system always has an unfailing source of
30 * entropy which is accessed via |CRYPTO_sysrand|. (If the operating system
31 * entropy source fails, it's up to |CRYPTO_sysrand| to abort the process—we
32 * don't try to handle it.)
33 *
34 * In addition, the hardware may provide a low-latency RNG. Intel's rdrand
35 * instruction is the canonical example of this. When a hardware RNG is
36 * available we don't need to worry about an RNG failure arising from fork()ing
37 * the process or moving a VM, so we can keep thread-local RNG state and XOR
38 * the hardware entropy in.
39 *
40 * (We assume that the OS entropy is safe from fork()ing and VM duplication.
41 * This might be a bit of a leap of faith, esp on Windows, but there's nothing
42 * that we can do about it.) */
43
44 /* rand_thread_state contains the per-thread state for the RNG. This is only
45 * used if the system has support for a hardware RNG. */
46 struct rand_thread_state {
47 uint8_t key[32];
48 uint64_t calls_used;
49 size_t bytes_used;
50 uint8_t partial_block[64];
51 unsigned partial_block_used;
52 };
53
54 /* kMaxCallsPerRefresh is the maximum number of |RAND_bytes| calls that we'll
55 * serve before reading a new key from the operating system. This only applies
56 * if we have a hardware RNG. */
57 static const unsigned kMaxCallsPerRefresh = 1024;
58
59 /* kMaxBytesPerRefresh is the maximum number of bytes that we'll return from
60 * |RAND_bytes| before reading a new key from the operating system. This only
61 * applies if we have a hardware RNG. */
62 static const uint64_t kMaxBytesPerRefresh = 1024 * 1024;
63
64 /* rand_thread_state_free frees a |rand_thread_state|. This is called when a
65 * thread exits. */
rand_thread_state_free(void * state)66 static void rand_thread_state_free(void *state) {
67 if (state == NULL) {
68 return;
69 }
70
71 OPENSSL_cleanse(state, sizeof(struct rand_thread_state));
72 OPENSSL_free(state);
73 }
74
75 #if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM)
76
77 /* These functions are defined in asm/rdrand-x86_64.pl */
78 extern int CRYPTO_rdrand(uint8_t out[8]);
79 extern int CRYPTO_rdrand_multiple8_buf(uint8_t *buf, size_t len);
80
have_rdrand(void)81 static int have_rdrand(void) {
82 return (OPENSSL_ia32cap_P[1] & (1u << 30)) != 0;
83 }
84
hwrand(uint8_t * buf,size_t len)85 static int hwrand(uint8_t *buf, size_t len) {
86 if (!have_rdrand()) {
87 return 0;
88 }
89
90 const size_t len_multiple8 = len & ~7;
91 if (!CRYPTO_rdrand_multiple8_buf(buf, len_multiple8)) {
92 return 0;
93 }
94 len -= len_multiple8;
95
96 if (len != 0) {
97 assert(len < 8);
98
99 uint8_t rand_buf[8];
100 if (!CRYPTO_rdrand(rand_buf)) {
101 return 0;
102 }
103 memcpy(buf + len_multiple8, rand_buf, len);
104 }
105
106 return 1;
107 }
108
109 #else
110
hwrand(uint8_t * buf,size_t len)111 static int hwrand(uint8_t *buf, size_t len) {
112 return 0;
113 }
114
115 #endif
116
RAND_bytes(uint8_t * buf,size_t len)117 int RAND_bytes(uint8_t *buf, size_t len) {
118 if (len == 0) {
119 return 1;
120 }
121
122 if (!hwrand(buf, len)) {
123 /* Without a hardware RNG to save us from address-space duplication, the OS
124 * entropy is used directly. */
125 CRYPTO_sysrand(buf, len);
126 return 1;
127 }
128
129 struct rand_thread_state *state =
130 CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_RAND);
131 if (state == NULL) {
132 state = OPENSSL_malloc(sizeof(struct rand_thread_state));
133 if (state == NULL ||
134 !CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_RAND, state,
135 rand_thread_state_free)) {
136 CRYPTO_sysrand(buf, len);
137 return 1;
138 }
139
140 memset(state->partial_block, 0, sizeof(state->partial_block));
141 state->calls_used = kMaxCallsPerRefresh;
142 }
143
144 if (state->calls_used >= kMaxCallsPerRefresh ||
145 state->bytes_used >= kMaxBytesPerRefresh) {
146 CRYPTO_sysrand(state->key, sizeof(state->key));
147 state->calls_used = 0;
148 state->bytes_used = 0;
149 state->partial_block_used = sizeof(state->partial_block);
150 }
151
152 if (len >= sizeof(state->partial_block)) {
153 size_t remaining = len;
154 while (remaining > 0) {
155 /* kMaxBytesPerCall is only 2GB, while ChaCha can handle 256GB. But this
156 * is sufficient and easier on 32-bit. */
157 static const size_t kMaxBytesPerCall = 0x80000000;
158 size_t todo = remaining;
159 if (todo > kMaxBytesPerCall) {
160 todo = kMaxBytesPerCall;
161 }
162 uint8_t nonce[12];
163 memset(nonce, 0, 4);
164 memcpy(nonce + 4, &state->calls_used, sizeof(state->calls_used));
165 CRYPTO_chacha_20(buf, buf, todo, state->key, nonce, 0);
166 buf += todo;
167 remaining -= todo;
168 state->calls_used++;
169 }
170 } else {
171 if (sizeof(state->partial_block) - state->partial_block_used < len) {
172 uint8_t nonce[12];
173 memset(nonce, 0, 4);
174 memcpy(nonce + 4, &state->calls_used, sizeof(state->calls_used));
175 CRYPTO_chacha_20(state->partial_block, state->partial_block,
176 sizeof(state->partial_block), state->key, nonce, 0);
177 state->partial_block_used = 0;
178 }
179
180 unsigned i;
181 for (i = 0; i < len; i++) {
182 buf[i] ^= state->partial_block[state->partial_block_used++];
183 }
184 state->calls_used++;
185 }
186 state->bytes_used += len;
187
188 return 1;
189 }
190
RAND_pseudo_bytes(uint8_t * buf,size_t len)191 int RAND_pseudo_bytes(uint8_t *buf, size_t len) {
192 return RAND_bytes(buf, len);
193 }
194
RAND_seed(const void * buf,int num)195 void RAND_seed(const void *buf, int num) {
196 /* OpenSSH calls |RAND_seed| before jailing on the assumption that any needed
197 * file descriptors etc will be opened. */
198 uint8_t unused;
199 RAND_bytes(&unused, sizeof(unused));
200 }
201
RAND_load_file(const char * path,long num)202 int RAND_load_file(const char *path, long num) {
203 if (num < 0) { /* read the "whole file" */
204 return 1;
205 } else if (num <= INT_MAX) {
206 return (int) num;
207 } else {
208 return INT_MAX;
209 }
210 }
211
RAND_add(const void * buf,int num,double entropy)212 void RAND_add(const void *buf, int num, double entropy) {}
213
RAND_egd(const char * path)214 int RAND_egd(const char *path) {
215 return 255;
216 }
217
RAND_poll(void)218 int RAND_poll(void) {
219 return 1;
220 }
221
RAND_status(void)222 int RAND_status(void) {
223 return 1;
224 }
225
226 static const struct rand_meth_st kSSLeayMethod = {
227 RAND_seed,
228 RAND_bytes,
229 RAND_cleanup,
230 RAND_add,
231 RAND_pseudo_bytes,
232 RAND_status,
233 };
234
RAND_SSLeay(void)235 RAND_METHOD *RAND_SSLeay(void) {
236 return (RAND_METHOD*) &kSSLeayMethod;
237 }
238
RAND_set_rand_method(const RAND_METHOD * method)239 void RAND_set_rand_method(const RAND_METHOD *method) {}
240