safe_bcmp.c

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/*
  +----------------------------------------------------------------------+
  | Copyright (c) The PHP Group                                          |
  +----------------------------------------------------------------------+
  | This source file is subject to version 3.01 of the PHP license,      |
  | that is bundled with this package in the file LICENSE, and is        |
  | available through the world-wide-web at the following url:           |
  | https://www.php.net/license/3_01.txt                                 |
  | If you did not receive a copy of the PHP license and are unable to   |
  | obtain it through the world-wide-web, please send a note to          |
  | license@php.net so we can mail you a copy immediately.               |
  +----------------------------------------------------------------------+
  | Author: David Carlier <devnexen@gmail.com>                           |
  +----------------------------------------------------------------------+
*/
 
#include "php.h"
 
#include <string.h>
 
/*
 * Returns 0 if both inputs match, non-zero if they don't.
 * Returns -1 early if inputs do not have the same lengths.
 *
 */
PHPAPI int php_safe_bcmp(const zend_string *a, const zend_string *b)
{
    const volatile unsigned char *ua = (const volatile unsigned char *)ZSTR_VAL(a);
    const volatile unsigned char *ub = (const volatile unsigned char *)ZSTR_VAL(b);
    size_t i = 0;
    int r = 0;
 
    if (ZSTR_LEN(a) != ZSTR_LEN(b)) {
        return -1;
    }
 
    /* This is security sensitive code. Do not optimize this for speed. */
    while (i < ZSTR_LEN(a)) {
        r |= ua[i] ^ ub[i];
        ++i;
    }
 
    return r;
}