/*
* Copyright (c) 2002-2024 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
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*/
/*-
* Copyright (c) 2008 Michael J. Silbersack.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/kernel.h>
#include <netinet/ip_var.h>
#include <sys/random.h>
#include <dev/random/randomdev.h>
uint16_t
ip_randomid(uint64_t salt)
{
uint16_t new_id;
/*
* Mostly the salt value is heap or stack pointer value.
* To avoid any chance of leaking address apply macro that
* adds per-boot random number to it.
*/
uint64_t salt_tmp = VM_KERNEL_ADDRPERM(salt);
/*
* When the passed salt values are addresses, it is possible some bits
* to not change at all, for example some higher order bits may not change
* and some lower order bits may be all 0s given particular alignment and object
* sizes.
* Therefore we compute a XOR'd 16bit value by considering all the bits
* of the salt to increase the likelihood of it being different.
*/
uint16_t new_id_salt = (uint16_t)(((salt_tmp >> 48) ^ (salt_tmp >> 32) ^
(salt_tmp >> 16) ^ salt_tmp) & 0xFF);
/* Avoid returning IP ID value of 0 */
do {
read_random(&new_id, sizeof(new_id));
} while (new_id == new_id_salt);
return new_id ^ new_id_salt;
}