proxmark3/common/mbedtls/entropy_poll.c

/*
 *  Platform-specific and custom entropy polling functions
 *
 *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: GPL-2.0
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */

#if defined(__linux__)
/* Ensure that syscall() is available even when compiling with -std=c99 */
#define _GNU_SOURCE
#endif

#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#include <string.h>

#if defined(MBEDTLS_ENTROPY_C)

#include "mbedtls/entropy.h"
#include "mbedtls/entropy_poll.h"

#if defined(MBEDTLS_TIMING_C)
#include "mbedtls/timing.h"
#endif
#if defined(MBEDTLS_HAVEGE_C)
#include "mbedtls/havege.h"
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
#include "mbedtls/platform.h"
#endif

#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)

#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
    !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
    !defined(__HAIKU__)
#error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
#endif

#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)

#if !defined(_WIN32_WINNT)
#define _WIN32_WINNT 0x0400
#endif
#include <windows.h>
#include <wincrypt.h>

int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len,
                                  size_t *olen) {
    HCRYPTPROV provider;
    ((void) data);
    *olen = 0;

    if (CryptAcquireContext(&provider, NULL, NULL,
                            PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) == FALSE) {
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    if (CryptGenRandom(provider, (DWORD) len, output) == FALSE) {
        CryptReleaseContext(provider, 0);
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    CryptReleaseContext(provider, 0);
    *olen = len;

    return (0);
}
#else /* _WIN32 && !EFIX64 && !EFI32 */

/*
 * Test for Linux getrandom() support.
 * Since there is no wrapper in the libc yet, use the generic syscall wrapper
 * available in GNU libc and compatible libc's (eg uClibc).
 */
#if defined(__linux__) && defined(__GLIBC__)
#include <unistd.h>
#include <sys/syscall.h>
#if defined(SYS_getrandom)
#define HAVE_GETRANDOM

static int getrandom_wrapper(void *buf, size_t buflen, unsigned int flags) {
    /* MemSan cannot understand that the syscall writes to the buffer */
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
    memset(buf, 0, buflen);
#endif
#endif

    return (syscall(SYS_getrandom, buf, buflen, flags));
}

#include <sys/utsname.h>
/* Check if version is at least 3.17.0 */
static int check_version_3_17_plus(void) {
    int minor;
    struct utsname un;
    const char *ver;

    /* Get version information */
    uname(&un);
    ver = un.release;

    /* Check major version; assume a single digit */
    if (ver[0] < '3' || ver[0] > '9' || ver [1] != '.')
        return (-1);

    if (ver[0] - '0' > 3)
        return (0);

    /* Ok, so now we know major == 3, check minor.
     * Assume 1 or 2 digits. */
    if (ver[2] < '0' || ver[2] > '9')
        return (-1);

    minor = ver[2] - '0';

    if (ver[3] >= '0' && ver[3] <= '9')
        minor = 10 * minor + ver[3] - '0';
    else if (ver [3] != '.')
        return (-1);

    if (minor < 17)
        return (-1);

    return (0);
}
static int has_getrandom = -1;
#endif /* SYS_getrandom */
#endif /* __linux__ */

#include <stdio.h>

int mbedtls_platform_entropy_poll(void *data,
                                  unsigned char *output, size_t len, size_t *olen) {
    FILE *file;
    size_t read_len;
    ((void) data);

#if defined(HAVE_GETRANDOM)
    if (has_getrandom == -1)
        has_getrandom = (check_version_3_17_plus() == 0);

    if (has_getrandom) {
        int ret;

        if ((ret = getrandom_wrapper(output, len, 0)) < 0)
            return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);

        *olen = ret;
        return (0);
    }
#endif /* HAVE_GETRANDOM */

    *olen = 0;

    file = fopen("/dev/urandom", "rb");
    if (file == NULL)
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);

    read_len = fread(output, 1, len, file);
    if (read_len != len) {
        fclose(file);
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    fclose(file);
    *olen = len;

    return (0);
}
#endif /* _WIN32 && !EFIX64 && !EFI32 */
#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */

#if defined(MBEDTLS_TEST_NULL_ENTROPY)
int mbedtls_null_entropy_poll(void *data,
                              unsigned char *output, size_t len, size_t *olen) {
    ((void) data);
    ((void) output);
    *olen = 0;

    if (len < sizeof(unsigned char))
        return (0);

    *olen = sizeof(unsigned char);

    return (0);
}
#endif

#if defined(MBEDTLS_TIMING_C)
int mbedtls_hardclock_poll(void *data,
                           unsigned char *output, size_t len, size_t *olen) {
    unsigned long timer = mbedtls_timing_hardclock();
    ((void) data);
    *olen = 0;

    if (len < sizeof(unsigned long))
        return (0);

    memcpy(output, &timer, sizeof(unsigned long));
    *olen = sizeof(unsigned long);

    return (0);
}
#endif /* MBEDTLS_TIMING_C */

#if defined(MBEDTLS_HAVEGE_C)
int mbedtls_havege_poll(void *data,
                        unsigned char *output, size_t len, size_t *olen) {
    mbedtls_havege_state *hs = (mbedtls_havege_state *) data;
    *olen = 0;

    if (mbedtls_havege_random(hs, output, len) != 0)
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);

    *olen = len;

    return (0);
}
#endif /* MBEDTLS_HAVEGE_C */

#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_nv_seed_poll(void *data,
                         unsigned char *output, size_t len, size_t *olen) {
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
    size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
    ((void) data);

    memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

    if (mbedtls_nv_seed_read(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0)
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);

    if (len < use_len)
        use_len = len;

    memcpy(output, buf, use_len);
    *olen = use_len;

    return (0);
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */

#endif /* MBEDTLS_ENTROPY_C */