1 /*
2 * QEMU Crypto random number provider
3 *
4 * Copyright (c) 2015-2016 Red Hat, Inc.
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 *
19 */
20
21 #include "qemu/osdep.h"
22
23 #include "crypto/random.h"
24 #include "qapi/error.h"
25
26 #ifdef _WIN32
27 #include <wincrypt.h>
28 static HCRYPTPROV hCryptProv;
29 #else
30 # ifdef CONFIG_GETRANDOM
31 # include <sys/random.h>
32 # endif
33 /* This is -1 for getrandom(), or a file handle for /dev/{u,}random. */
34 static int fd;
35 #endif
36
qcrypto_random_init(Error ** errp)37 int qcrypto_random_init(Error **errp)
38 {
39 #ifdef _WIN32
40 if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
41 CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
42 error_setg_win32(errp, GetLastError(),
43 "Unable to create cryptographic provider");
44 return -1;
45 }
46 #else
47 # ifdef CONFIG_GETRANDOM
48 if (getrandom(NULL, 0, 0) == 0) {
49 /* Use getrandom() */
50 fd = -1;
51 return 0;
52 }
53 /* Fall through to /dev/urandom case. */
54 # endif
55 fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
56 if (fd == -1 && errno == ENOENT) {
57 fd = open("/dev/random", O_RDONLY | O_CLOEXEC);
58 }
59 if (fd < 0) {
60 error_setg_errno(errp, errno, "No /dev/urandom or /dev/random");
61 return -1;
62 }
63 #endif
64 return 0;
65 }
66
qcrypto_random_bytes(void * buf,size_t buflen,Error ** errp)67 int qcrypto_random_bytes(void *buf,
68 size_t buflen,
69 Error **errp)
70 {
71 #ifdef _WIN32
72 if (!CryptGenRandom(hCryptProv, buflen, buf)) {
73 error_setg_win32(errp, GetLastError(),
74 "Unable to read random bytes");
75 return -1;
76 }
77 #else
78 # ifdef CONFIG_GETRANDOM
79 if (likely(fd < 0)) {
80 while (1) {
81 ssize_t got = getrandom(buf, buflen, 0);
82 if (likely(got == buflen)) {
83 return 0;
84 }
85 if (got >= 0) {
86 buflen -= got;
87 buf += got;
88 } else if (errno != EINTR) {
89 error_setg_errno(errp, errno, "getrandom");
90 return -1;
91 }
92 }
93 }
94 /* Fall through to /dev/urandom case. */
95 # endif
96 while (1) {
97 ssize_t got = read(fd, buf, buflen);
98 if (likely(got == buflen)) {
99 return 0;
100 }
101 if (got > 0) {
102 buflen -= got;
103 buf += got;
104 } else if (got == 0) {
105 error_setg(errp, "Unexpected EOF reading random bytes");
106 return -1;
107 } else if (errno != EINTR) {
108 error_setg_errno(errp, errno, "Unable to read random bytes");
109 return -1;
110 }
111 }
112 #endif
113 return 0;
114 }
115