ring 0.7.4

/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

/* Copyright 2016 Brian Smith.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#if defined(__linux__)
#define _GNU_SOURCE
#endif

#include <openssl/base.h>

#include <assert.h>
#include <stddef.h>

/* GFp_sysrand_chunk fills |len| bytes at |buf| with entropy from the
 * operating system. |len| must be no more than |GFp_sysrand_chunk_max_len|.
 * It returns one on success, -1 if it failed because the operating system
 * doesn't offer such an API, or zero otherwise. */
long GFp_sysrand_chunk(void *buf, size_t len);

#if defined(OPENSSL_WINDOWS)

#include <limits.h>

#if defined(_MSC_VER)
#pragma warning(push, 3)
#endif

#include <windows.h>

/* #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036.  See the
 * "Community Additions" comment on MSDN here:
 * http://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx */
#define SystemFunction036 NTAPI SystemFunction036
#include <ntsecapi.h>
#undef SystemFunction036

#if defined(_MSC_VER)
#pragma warning(pop)
#endif

long GFp_sysrand_chunk(void *out, size_t requested) {
  if (requested > ULONG_MAX) {
    requested = ULONG_MAX;
  }
  if (requested > (size_t)LONG_MAX) {
    requested = (size_t)LONG_MAX;
  }

  return RtlGenRandom(out, (ULONG)requested) ? (long)requested : 0;
}

#elif defined(__linux__)

#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>

/* The getrandom syscall was added in Linux 3.17. For some important platforms,
 * we also support building against older kernels' headers. For other
 * platforms, the newer kernel's headers are required. */
#if !defined(SYS_getrandom)
#if defined(OPENSSL_AARCH64)
#define SYS_getrandom 278
#elif defined(OPENSSL_ARM)
#define SYS_getrandom 384
#elif defined(OPENSSL_X86)
#define SYS_getrandom 355
#elif defined(OPENSSL_X86_64)
#define SYS_getrandom 318
#else
#error "Error: Kernel headers are too old; SYS_getrandom not defined."
#endif
#endif

long GFp_sysrand_chunk(void *out, size_t requested) {
  long r = syscall(SYS_getrandom, out, requested, 0u);
  if (r < 0) {
    // EINTR is normal, and we can try again. Other error codes are fatal.
    if (errno == EINTR) {
      return 0;
    }
    return -1;
  }
  return r;
}

#endif