1 /*
2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 #include "internal/cryptlib.h"
11 #include <openssl/opensslconf.h>
12 #include "crypto/rand_pool.h"
13 #include "prov/seeding.h"
14
15 #ifdef OPENSSL_RAND_SEED_RDCPU
16 #if defined(OPENSSL_SYS_TANDEM) && defined(_TNS_X_TARGET)
17 #include <builtin.h> /* _rdrand64 */
18 #include <string.h> /* memcpy */
19 #else
20 size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
21 size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
22 #endif
23
24 static size_t get_hardware_random_value(unsigned char *buf, size_t len);
25
26 /*
27 * Acquire entropy using Intel-specific cpu instructions
28 *
29 * Uses the RDSEED instruction if available, otherwise uses
30 * RDRAND if available.
31 *
32 * For the differences between RDSEED and RDRAND, and why RDSEED
33 * is the preferred choice, see https://goo.gl/oK3KcN
34 *
35 * Returns the total entropy count, if it exceeds the requested
36 * entropy count. Otherwise, returns an entropy count of 0.
37 */
ossl_prov_acquire_entropy_from_cpu(RAND_POOL * pool)38 size_t ossl_prov_acquire_entropy_from_cpu(RAND_POOL *pool)
39 {
40 size_t bytes_needed;
41 unsigned char *buffer;
42
43 bytes_needed = ossl_rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
44 if (bytes_needed > 0) {
45 buffer = ossl_rand_pool_add_begin(pool, bytes_needed);
46
47 if (buffer != NULL) {
48 if (get_hardware_random_value(buffer, bytes_needed) == bytes_needed) {
49 ossl_rand_pool_add_end(pool, bytes_needed, 8 * bytes_needed);
50 } else {
51 ossl_rand_pool_add_end(pool, 0, 0);
52 }
53 }
54 }
55
56 return ossl_rand_pool_entropy_available(pool);
57 }
58
59 #if defined(OPENSSL_SYS_TANDEM) && defined(_TNS_X_TARGET)
60 /* Obtain random bytes from the x86 hardware random function in 64 bit chunks */
get_hardware_random_value(unsigned char * buf,size_t len)61 static size_t get_hardware_random_value(unsigned char *buf, size_t len)
62 {
63 size_t bytes_remaining = len;
64
65 while (bytes_remaining > 0) {
66 /* Always use 64 bit fetch, then use the lower bytes as needed. */
67 /* The platform is big-endian. */
68 uint64_t random_value = 0;
69
70 if (_rdrand64(&random_value) != 0) {
71 unsigned char *random_buffer = (unsigned char *)&random_value;
72
73 if (bytes_remaining >= sizeof(random_value)) {
74 memcpy(buf, random_buffer, sizeof(random_value));
75 bytes_remaining -= sizeof(random_value);
76 buf += sizeof(random_value);
77 } else {
78 memcpy(buf,
79 random_buffer + (sizeof(random_value) - bytes_remaining),
80 bytes_remaining);
81 bytes_remaining = 0; /* This will terminate the loop */
82 }
83 } else
84 break;
85 }
86 if (bytes_remaining == 0)
87 return len;
88 return 0;
89 }
90 #else
get_hardware_random_value(unsigned char * buf,size_t len)91 static size_t get_hardware_random_value(unsigned char *buf, size_t len)
92 {
93 /* Whichever comes first, use RDSEED, RDRAND or nothing */
94 if ((OPENSSL_ia32cap_P[2] & (1 << 18)) != 0) {
95 if (OPENSSL_ia32_rdseed_bytes(buf, len) != len)
96 return 0;
97 } else if ((OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) != 0) {
98 if (OPENSSL_ia32_rdrand_bytes(buf, len) != len)
99 return 0;
100 } else
101 return 0;
102 return len;
103 }
104 #endif
105
106 #else
107 NON_EMPTY_TRANSLATION_UNIT
108 #endif
109