zircon/kernel/dev/hw_rng/debug.cc

// Copyright 2016 The Fuchsia Authors
// Copyright (c) 2016, Google, Inc. All rights reserved
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <debug.h>
#include <lib/console.h>
#include <stdlib.h>
#include <zircon/errors.h>

#include <dev/hw_rng.h>
#include <fbl/algorithm.h>
#include <ktl/algorithm.h>
#include <pretty/hexdump.h>

static int cmd_rng32(int argc, const cmd_args* argv, uint32_t flags) {
  uint32_t val;
  __UNUSED size_t fetched;

  fetched = hw_rng_get_entropy(&val, sizeof(val));

  if (fetched == 0) {
    printf("hw rng failed. Support may not exist on this platform\n");
    return ZX_ERR_NOT_SUPPORTED;
  }

  DEBUG_ASSERT(fetched == sizeof(val));

  printf("Random val = %u (0x%08x)\n", val, val);

  return ZX_OK;
}

static int cmd_rng(int argc, const cmd_args* argv, uint32_t flags) {
  if ((argc < 2) || (argc > 3)) {
    printf(
        "Invalid argument count\n\n"
        "Usage : %s <N>\n"
        "N     : Number of bytes to generate.\n",
        argv[0].str);
    return ZX_ERR_INVALID_ARGS;
  }

  printf("Generating %lu random bytes\n", argv[1].u);

  size_t offset = 0;
  while (offset < argv[1].u) {
    uint8_t bytes[16];
    size_t todo, done;

    todo = ktl::min(sizeof(bytes), argv[1].u - offset);
    done = hw_rng_get_entropy(bytes, todo);
    DEBUG_ASSERT(done <= todo);

    hexdump8_ex(bytes, done, offset);
    offset += done;

    if (done < todo) {
      printf("Entropy exhausted after %zu byte%s\n", offset, offset == 1 ? "" : "s");
      break;
    }
  }

  return ZX_OK;
}

STATIC_COMMAND_START
STATIC_COMMAND("rng32", "Generate and print a random 32 bit unsigned integer using the HW RNG",
               &cmd_rng32)
STATIC_COMMAND("rng", "Generate and print N random bytes using the HW RNG", &cmd_rng)
STATIC_COMMAND_END(hw_rng)