1 /* 2 * Platform-specific and custom entropy polling functions 3 * 4 * Copyright The Mbed TLS Contributors 5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 6 */ 7 8 #if defined(__linux__) || defined(__midipix__) 9 /* Ensure that syscall() is available even when compiling with -std=c99 */ 10 #if !defined(_GNU_SOURCE) 11 #define _GNU_SOURCE 12 #endif 13 #endif 14 15 #include "common.h" 16 17 #include <string.h> 18 19 #if defined(MBEDTLS_ENTROPY_C) 20 21 #include "mbedtls/entropy.h" 22 #include "entropy_poll.h" 23 #include "mbedtls/error.h" 24 25 #if defined(MBEDTLS_TIMING_C) 26 #include "mbedtls/timing.h" 27 #endif 28 #include "mbedtls/platform.h" 29 30 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY) 31 32 #if !defined(unix) && !defined(__unix__) && !defined(__unix) && \ 33 !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \ 34 !defined(__HAIKU__) && !defined(__midipix__) && !defined(__MVS__) 35 #error \ 36 "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in mbedtls_config.h" 37 #endif 38 39 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) 40 41 #include <windows.h> 42 #include <bcrypt.h> 43 #include <intsafe.h> 44 45 int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len, 46 size_t *olen) 47 { 48 ((void) data); 49 *olen = 0; 50 51 /* 52 * BCryptGenRandom takes ULONG for size, which is smaller than size_t on 53 * 64-bit Windows platforms. Extract entropy in chunks of len (dependent 54 * on ULONG_MAX) size. 55 */ 56 while (len != 0) { 57 unsigned long ulong_bytes = 58 (len > ULONG_MAX) ? ULONG_MAX : (unsigned long) len; 59 60 if (!BCRYPT_SUCCESS(BCryptGenRandom(NULL, output, ulong_bytes, 61 BCRYPT_USE_SYSTEM_PREFERRED_RNG))) { 62 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 63 } 64 65 *olen += ulong_bytes; 66 len -= ulong_bytes; 67 } 68 69 return 0; 70 } 71 #else /* _WIN32 && !EFIX64 && !EFI32 */ 72 73 /* 74 * Test for Linux getrandom() support. 75 * Since there is no wrapper in the libc yet, use the generic syscall wrapper 76 * available in GNU libc and compatible libc's (eg uClibc). 77 */ 78 #if ((defined(__linux__) && defined(__GLIBC__)) || defined(__midipix__)) 79 #include <unistd.h> 80 #include <sys/syscall.h> 81 #if defined(SYS_getrandom) 82 #define HAVE_GETRANDOM 83 #include <errno.h> 84 85 static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags) 86 { 87 /* MemSan cannot understand that the syscall writes to the buffer */ 88 #if defined(__has_feature) 89 #if __has_feature(memory_sanitizer) 90 memset(buf, 0, buflen); 91 #endif 92 #endif 93 return (int) syscall(SYS_getrandom, buf, buflen, flags); 94 } 95 #endif /* SYS_getrandom */ 96 #endif /* __linux__ || __midipix__ */ 97 98 #if defined(__FreeBSD__) || defined(__DragonFly__) 99 #include <sys/param.h> 100 #if (defined(__FreeBSD__) && __FreeBSD_version >= 1200000) || \ 101 (defined(__DragonFly__) && __DragonFly_version >= 500700) 102 #include <errno.h> 103 #include <sys/random.h> 104 #define HAVE_GETRANDOM 105 static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags) 106 { 107 return (int) getrandom(buf, buflen, flags); 108 } 109 #endif /* (__FreeBSD__ && __FreeBSD_version >= 1200000) || 110 (__DragonFly__ && __DragonFly_version >= 500700) */ 111 #endif /* __FreeBSD__ || __DragonFly__ */ 112 113 /* 114 * Some BSD systems provide KERN_ARND. 115 * This is equivalent to reading from /dev/urandom, only it doesn't require an 116 * open file descriptor, and provides up to 256 bytes per call (basically the 117 * same as getentropy(), but with a longer history). 118 * 119 * Documentation: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7 120 */ 121 #if (defined(__FreeBSD__) || defined(__NetBSD__)) && !defined(HAVE_GETRANDOM) 122 #include <sys/param.h> 123 #include <sys/sysctl.h> 124 #if defined(KERN_ARND) 125 #define HAVE_SYSCTL_ARND 126 127 static int sysctl_arnd_wrapper(unsigned char *buf, size_t buflen) 128 { 129 int name[2]; 130 size_t len; 131 132 name[0] = CTL_KERN; 133 name[1] = KERN_ARND; 134 135 while (buflen > 0) { 136 len = buflen > 256 ? 256 : buflen; 137 if (sysctl(name, 2, buf, &len, NULL, 0) == -1) { 138 return -1; 139 } 140 buflen -= len; 141 buf += len; 142 } 143 return 0; 144 } 145 #endif /* KERN_ARND */ 146 #endif /* __FreeBSD__ || __NetBSD__ */ 147 148 #include <stdio.h> 149 150 int mbedtls_platform_entropy_poll(void *data, 151 unsigned char *output, size_t len, size_t *olen) 152 { 153 FILE *file; 154 size_t read_len; 155 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 156 ((void) data); 157 158 #if defined(HAVE_GETRANDOM) 159 ret = getrandom_wrapper(output, len, 0); 160 if (ret >= 0) { 161 *olen = (size_t) ret; 162 return 0; 163 } else if (errno != ENOSYS) { 164 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 165 } 166 /* Fall through if the system call isn't known. */ 167 #else 168 ((void) ret); 169 #endif /* HAVE_GETRANDOM */ 170 171 #if defined(HAVE_SYSCTL_ARND) 172 ((void) file); 173 ((void) read_len); 174 if (sysctl_arnd_wrapper(output, len) == -1) { 175 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 176 } 177 *olen = len; 178 return 0; 179 #else 180 181 *olen = 0; 182 183 file = fopen("/dev/urandom", "rb"); 184 if (file == NULL) { 185 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 186 } 187 188 /* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */ 189 mbedtls_setbuf(file, NULL); 190 191 read_len = fread(output, 1, len, file); 192 if (read_len != len) { 193 fclose(file); 194 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 195 } 196 197 fclose(file); 198 *olen = len; 199 200 return 0; 201 #endif /* HAVE_SYSCTL_ARND */ 202 } 203 #endif /* _WIN32 && !EFIX64 && !EFI32 */ 204 #endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */ 205 206 #if defined(MBEDTLS_ENTROPY_NV_SEED) 207 int mbedtls_nv_seed_poll(void *data, 208 unsigned char *output, size_t len, size_t *olen) 209 { 210 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE]; 211 size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE; 212 ((void) data); 213 214 memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE); 215 216 if (mbedtls_nv_seed_read(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) { 217 return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED; 218 } 219 220 if (len < use_len) { 221 use_len = len; 222 } 223 224 memcpy(output, buf, use_len); 225 *olen = use_len; 226 227 return 0; 228 } 229 #endif /* MBEDTLS_ENTROPY_NV_SEED */ 230 231 #endif /* MBEDTLS_ENTROPY_C */ 232