1 /* 2 * Platform-specific and custom entropy polling functions 3 * 4 * Copyright The Mbed TLS Contributors 5 * SPDX-License-Identifier: Apache-2.0 6 * 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may 8 * not use this file except in compliance with the License. 9 * You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 20 #if defined(__linux__) && !defined(_GNU_SOURCE) 21 /* Ensure that syscall() is available even when compiling with -std=c99 */ 22 #define _GNU_SOURCE 23 #endif 24 25 #include "common.h" 26 27 #include <string.h> 28 29 #if defined(MBEDTLS_ENTROPY_C) 30 31 #include "mbedtls/entropy.h" 32 #include "entropy_poll.h" 33 #include "mbedtls/error.h" 34 35 #if defined(MBEDTLS_TIMING_C) 36 #include "mbedtls/timing.h" 37 #endif 38 #include "mbedtls/platform.h" 39 40 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY) 41 42 #if !defined(unix) && !defined(__unix__) && !defined(__unix) && \ 43 !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \ 44 !defined(__HAIKU__) && !defined(__midipix__) 45 #error \ 46 "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in mbedtls_config.h" 47 #endif 48 49 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) 50 51 #if !defined(_WIN32_WINNT) 52 #define _WIN32_WINNT 0x0400 53 #endif 54 #include <windows.h> 55 #include <wincrypt.h> 56 57 int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len, 58 size_t *olen) 59 { 60 HCRYPTPROV provider; 61 ((void) data); 62 *olen = 0; 63 64 if (CryptAcquireContext(&provider, NULL, NULL, 65 PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) == FALSE) { 66 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 67 } 68 69 if (CryptGenRandom(provider, (DWORD) len, output) == FALSE) { 70 CryptReleaseContext(provider, 0); 71 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 72 } 73 74 CryptReleaseContext(provider, 0); 75 *olen = len; 76 77 return 0; 78 } 79 #else /* _WIN32 && !EFIX64 && !EFI32 */ 80 81 /* 82 * Test for Linux getrandom() support. 83 * Since there is no wrapper in the libc yet, use the generic syscall wrapper 84 * available in GNU libc and compatible libc's (eg uClibc). 85 */ 86 #if ((defined(__linux__) && defined(__GLIBC__)) || defined(__midipix__)) 87 #include <unistd.h> 88 #include <sys/syscall.h> 89 #if defined(SYS_getrandom) 90 #define HAVE_GETRANDOM 91 #include <errno.h> 92 93 static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags) 94 { 95 /* MemSan cannot understand that the syscall writes to the buffer */ 96 #if defined(__has_feature) 97 #if __has_feature(memory_sanitizer) 98 memset(buf, 0, buflen); 99 #endif 100 #endif 101 return syscall(SYS_getrandom, buf, buflen, flags); 102 } 103 #endif /* SYS_getrandom */ 104 #endif /* __linux__ || __midipix__ */ 105 106 #if defined(__FreeBSD__) || defined(__DragonFly__) 107 #include <sys/param.h> 108 #if (defined(__FreeBSD__) && __FreeBSD_version >= 1200000) || \ 109 (defined(__DragonFly__) && __DragonFly_version >= 500700) 110 #include <errno.h> 111 #include <sys/random.h> 112 #define HAVE_GETRANDOM 113 static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags) 114 { 115 return getrandom(buf, buflen, flags); 116 } 117 #endif /* (__FreeBSD__ && __FreeBSD_version >= 1200000) || 118 (__DragonFly__ && __DragonFly_version >= 500700) */ 119 #endif /* __FreeBSD__ || __DragonFly__ */ 120 121 /* 122 * Some BSD systems provide KERN_ARND. 123 * This is equivalent to reading from /dev/urandom, only it doesn't require an 124 * open file descriptor, and provides up to 256 bytes per call (basically the 125 * same as getentropy(), but with a longer history). 126 * 127 * Documentation: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7 128 */ 129 #if (defined(__FreeBSD__) || defined(__NetBSD__)) && !defined(HAVE_GETRANDOM) 130 #include <sys/param.h> 131 #include <sys/sysctl.h> 132 #if defined(KERN_ARND) 133 #define HAVE_SYSCTL_ARND 134 135 static int sysctl_arnd_wrapper(unsigned char *buf, size_t buflen) 136 { 137 int name[2]; 138 size_t len; 139 140 name[0] = CTL_KERN; 141 name[1] = KERN_ARND; 142 143 while (buflen > 0) { 144 len = buflen > 256 ? 256 : buflen; 145 if (sysctl(name, 2, buf, &len, NULL, 0) == -1) { 146 return -1; 147 } 148 buflen -= len; 149 buf += len; 150 } 151 return 0; 152 } 153 #endif /* KERN_ARND */ 154 #endif /* __FreeBSD__ || __NetBSD__ */ 155 156 #include <stdio.h> 157 158 int mbedtls_platform_entropy_poll(void *data, 159 unsigned char *output, size_t len, size_t *olen) 160 { 161 FILE *file; 162 size_t read_len; 163 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 164 ((void) data); 165 166 #if defined(HAVE_GETRANDOM) 167 ret = getrandom_wrapper(output, len, 0); 168 if (ret >= 0) { 169 *olen = ret; 170 return 0; 171 } else if (errno != ENOSYS) { 172 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 173 } 174 /* Fall through if the system call isn't known. */ 175 #else 176 ((void) ret); 177 #endif /* HAVE_GETRANDOM */ 178 179 #if defined(HAVE_SYSCTL_ARND) 180 ((void) file); 181 ((void) read_len); 182 if (sysctl_arnd_wrapper(output, len) == -1) { 183 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 184 } 185 *olen = len; 186 return 0; 187 #else 188 189 *olen = 0; 190 191 file = fopen("/dev/urandom", "rb"); 192 if (file == NULL) { 193 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 194 } 195 196 /* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */ 197 mbedtls_setbuf(file, NULL); 198 199 read_len = fread(output, 1, len, file); 200 if (read_len != len) { 201 fclose(file); 202 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 203 } 204 205 fclose(file); 206 *olen = len; 207 208 return 0; 209 #endif /* HAVE_SYSCTL_ARND */ 210 } 211 #endif /* _WIN32 && !EFIX64 && !EFI32 */ 212 #endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */ 213 214 #if defined(MBEDTLS_ENTROPY_NV_SEED) 215 int mbedtls_nv_seed_poll(void *data, 216 unsigned char *output, size_t len, size_t *olen) 217 { 218 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE]; 219 size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE; 220 ((void) data); 221 222 memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE); 223 224 if (mbedtls_nv_seed_read(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) { 225 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 226 } 227 228 if (len < use_len) { 229 use_len = len; 230 } 231 232 memcpy(output, buf, use_len); 233 *olen = use_len; 234 235 return 0; 236 } 237 #endif /* MBEDTLS_ENTROPY_NV_SEED */ 238 239 #endif /* MBEDTLS_ENTROPY_C */ 240