util.c

/*
 * Copyright 2017 Google Inc.
 * SPDX-License-Identifier: Apache-2.0
 *
 * An earlier version of this file was originally released into the public
 * domain by its authors. It has been modified to make the code compile and
 * link as part of the Google Authenticator project. These changes are
 * copyrighted by Google Inc. and released under the Apache License,
 * Version 2.0.
 *
 * The previous authors' terms are included below:
 */

/*****************************************************************************
 *
 * File:    util.c
 *
 * Purpose: Collection of cross file utility functions.
 *
 * This code is in the public domain
 *
 *****************************************************************************
 */

#include "config.h"

#include "util.h"

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#ifndef HAVE_EXPLICIT_BZERO
#define HAVE_EXPLICIT_BZERO 0
#endif

#ifndef FORCE_EXPLICIT_BZERO_FALLBACK
#define FORCE_EXPLICIT_BZERO_FALLBACK 0
#endif

#if !HAVE_EXPLICIT_BZERO || FORCE_EXPLICIT_BZERO_FALLBACK
// Prefer libc explicit_bzero() when it exists. Otherwise, route memset()
// through a volatile function pointer so the wipe remains an observable call
// without relying on compiler-specific inline assembly.
static void *(*const volatile memset_impl)(void *, int, size_t) = memset;

void explicit_bzero(void *s, size_t len) { memset_impl(s, 0, len); }
#endif

int ClampInt(int value, int min_value, int max_value) {
  assert(min_value <= max_value);
  if (value < min_value) {
    return min_value;
  }
  if (value > max_value) {
    return max_value;
  }
  return value;
}

double ClampDouble(double value, double min_value, double max_value) {
  assert(min_value <= max_value);
  if (value < min_value) {
    return min_value;
  }
  if (value > max_value) {
    return max_value;
  }
  return value;
}

void ClearFreeString(char **p) {
  if (p == NULL || *p == NULL) {
    return;
  }

  explicit_bzero(*p, strlen(*p));
  free(*p);
  *p = NULL;
}

void ClearFreeBuffer(char **p, size_t len) {
  if (p == NULL || *p == NULL) {
    return;
  }

  explicit_bzero(*p, len);
  free(*p);
  *p = NULL;
}