244 lines
6.7 KiB
C
244 lines
6.7 KiB
C
/*
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* Platform-specific and custom entropy polling functions
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#if defined(__linux__) && !defined(_GNU_SOURCE)
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/* Ensure that syscall() is available even when compiling with -std=c99 */
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#define _GNU_SOURCE
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#endif
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#include "common.h"
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#include <string.h>
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#if defined(MBEDTLS_ENTROPY_C)
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#include "mbedtls/entropy.h"
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#include "entropy_poll.h"
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#include "mbedtls/error.h"
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#if defined(MBEDTLS_TIMING_C)
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#include "mbedtls/timing.h"
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#endif
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#include "mbedtls/platform.h"
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#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
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#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
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!defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
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!defined(__HAIKU__) && !defined(__midipix__)
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#error \
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"Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in mbedtls_config.h"
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#endif
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#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
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#include <windows.h>
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#if _WIN32_WINNT >= 0x0501 /* _WIN32_WINNT_WINXP */
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#include <bcrypt.h>
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#include <intsafe.h>
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int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len,
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size_t *olen)
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{
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ULONG len_as_ulong = 0;
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((void) data);
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*olen = 0;
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/*
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* BCryptGenRandom takes ULONG for size, which is smaller than size_t on
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* 64-bit Windows platforms. Ensure len's value can be safely converted into
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* a ULONG.
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*/
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if (FAILED(SizeTToULong(len, &len_as_ulong))) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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if (!BCRYPT_SUCCESS(BCryptGenRandom(NULL, output, len_as_ulong,
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BCRYPT_USE_SYSTEM_PREFERRED_RNG))) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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*olen = len;
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return 0;
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}
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#else /* !_WIN32_WINNT_WINXP */
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#error "Entropy not available before Windows XP, use MBEDTLS_NO_PLATFORM_ENTROPY"
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#endif /* !_WIN32_WINNT_WINXP */
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#else /* _WIN32 && !EFIX64 && !EFI32 */
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/*
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* Test for Linux getrandom() support.
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* Since there is no wrapper in the libc yet, use the generic syscall wrapper
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* available in GNU libc and compatible libc's (eg uClibc).
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*/
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#if ((defined(__linux__) && defined(__GLIBC__)) || defined(__midipix__))
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#include <unistd.h>
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#include <sys/syscall.h>
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#if defined(SYS_getrandom)
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#define HAVE_GETRANDOM
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#include <errno.h>
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static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags)
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{
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/* MemSan cannot understand that the syscall writes to the buffer */
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#if defined(__has_feature)
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#if __has_feature(memory_sanitizer)
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memset(buf, 0, buflen);
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#endif
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#endif
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return syscall(SYS_getrandom, buf, buflen, flags);
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}
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#endif /* SYS_getrandom */
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#endif /* __linux__ || __midipix__ */
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#if defined(__FreeBSD__) || defined(__DragonFly__)
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#include <sys/param.h>
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#if (defined(__FreeBSD__) && __FreeBSD_version >= 1200000) || \
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(defined(__DragonFly__) && __DragonFly_version >= 500700)
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#include <errno.h>
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#include <sys/random.h>
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#define HAVE_GETRANDOM
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static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags)
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{
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return getrandom(buf, buflen, flags);
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}
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#endif /* (__FreeBSD__ && __FreeBSD_version >= 1200000) ||
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(__DragonFly__ && __DragonFly_version >= 500700) */
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#endif /* __FreeBSD__ || __DragonFly__ */
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/*
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* Some BSD systems provide KERN_ARND.
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* This is equivalent to reading from /dev/urandom, only it doesn't require an
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* open file descriptor, and provides up to 256 bytes per call (basically the
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* same as getentropy(), but with a longer history).
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*
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* Documentation: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7
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*/
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#if (defined(__FreeBSD__) || defined(__NetBSD__)) && !defined(HAVE_GETRANDOM)
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#include <sys/param.h>
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#include <sys/sysctl.h>
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#if defined(KERN_ARND)
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#define HAVE_SYSCTL_ARND
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static int sysctl_arnd_wrapper(unsigned char *buf, size_t buflen)
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{
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int name[2];
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size_t len;
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name[0] = CTL_KERN;
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name[1] = KERN_ARND;
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while (buflen > 0) {
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len = buflen > 256 ? 256 : buflen;
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if (sysctl(name, 2, buf, &len, NULL, 0) == -1) {
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return -1;
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}
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buflen -= len;
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buf += len;
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}
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return 0;
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}
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#endif /* KERN_ARND */
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#endif /* __FreeBSD__ || __NetBSD__ */
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#include <stdio.h>
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int mbedtls_platform_entropy_poll(void *data,
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unsigned char *output, size_t len, size_t *olen)
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{
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FILE *file;
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size_t read_len;
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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((void) data);
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#if defined(HAVE_GETRANDOM)
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ret = getrandom_wrapper(output, len, 0);
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if (ret >= 0) {
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*olen = ret;
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return 0;
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} else if (errno != ENOSYS) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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/* Fall through if the system call isn't known. */
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#else
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((void) ret);
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#endif /* HAVE_GETRANDOM */
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#if defined(HAVE_SYSCTL_ARND)
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((void) file);
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((void) read_len);
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if (sysctl_arnd_wrapper(output, len) == -1) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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*olen = len;
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return 0;
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#else
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*olen = 0;
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file = fopen("/dev/urandom", "rb");
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if (file == NULL) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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/* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */
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mbedtls_setbuf(file, NULL);
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read_len = fread(output, 1, len, file);
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if (read_len != len) {
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fclose(file);
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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fclose(file);
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*olen = len;
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return 0;
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#endif /* HAVE_SYSCTL_ARND */
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}
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#endif /* _WIN32 && !EFIX64 && !EFI32 */
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#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
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#if defined(MBEDTLS_ENTROPY_NV_SEED)
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int mbedtls_nv_seed_poll(void *data,
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unsigned char *output, size_t len, size_t *olen)
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{
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unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
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size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
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((void) data);
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memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
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if (mbedtls_nv_seed_read(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) {
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return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
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}
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if (len < use_len) {
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use_len = len;
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}
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memcpy(output, buf, use_len);
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*olen = use_len;
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return 0;
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}
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#endif /* MBEDTLS_ENTROPY_NV_SEED */
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#endif /* MBEDTLS_ENTROPY_C */
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