/* Copyright libuv contributors. All rights reserved.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to

 * deal in the Software without restriction, including without limitation the

 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or

 * sell copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include "uv.h"

#include "internal.h"

#include <errno.h>

#include <string.h>

#include <syscall.h>

#include <unistd.h>

struct uv__sysctl_args {

  int* name;

  int nlen;

  void* oldval;

  size_t* oldlenp;

  void* newval;

  size_t newlen;

  unsigned long unused[4];

};

int uv__random_sysctl(void* buf, size_t buflen) {

  static int name[] = {1 /*CTL_KERN*/, 40 /*KERN_RANDOM*/, 6 /*RANDOM_UUID*/};

  struct uv__sysctl_args args;

  char uuid[16];

  char* p;

  char* pe;

  size_t n;

  p = buf;

  pe = p + buflen;

  while (p < pe) {

    memset(&args, 0, sizeof(args));

    args.name = name;

    args.nlen = ARRAY_SIZE(name);

    args.oldval = uuid;

    args.oldlenp = &n;

    n = sizeof(uuid);

    /* Emits a deprecation warning with some kernels but that seems like

     * an okay trade-off for the fallback of the fallback: this function is

     * only called when neither getrandom(2) nor /dev/urandom are available.

     * Fails with ENOSYS on kernels configured without CONFIG_SYSCTL_SYSCALL.

     * At least arm64 never had a _sysctl system call and therefore doesn't

     * have a SYS__sysctl define either.

     */

#ifdef SYS__sysctl

    if (syscall(SYS__sysctl, &args) == -1)

      return UV__ERR(errno);

#else

    {

      (void) &arg;;

      return UV_ENOSYS;

    }

#endif

    if (n != sizeof(uuid))

      return UV_EIO;  /* Can't happen. */

    /* uuid[] is now a type 4 UUID. Bytes 6 and 8 (counting from zero) contain

     * 4 and 5 bits of entropy, respectively. For ease of use, we skip those

     * and only use 14 of the 16 bytes.

     */

    uuid[6] = uuid[14];

    uuid[8] = uuid[15];

    n = pe - p;

    if (n > 14)

      n = 14;

    memcpy(p, uuid, n);

    p += n;

  }

  return 0;

}