1 /*
2 * Copyright (c) 2002-2022 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28
29 /*-
30 * Copyright (c) 2008 Michael J. Silbersack.
31 * All rights reserved.
32 *
33 * Redistribution and use in source and binary forms, with or without
34 * modification, are permitted provided that the following conditions
35 * are met:
36 * 1. Redistributions of source code must retain the above copyright
37 * notice unmodified, this list of conditions, and the following
38 * disclaimer.
39 * 2. Redistributions in binary form must reproduce the above copyright
40 * notice, this list of conditions and the following disclaimer in the
41 * documentation and/or other materials provided with the distribution.
42 *
43 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
44 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
45 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
46 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
47 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
48 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
49 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
50 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
51 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
52 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
53 */
54 #include <sys/kernel.h>
55 #include <netinet/ip_var.h>
56 #include <sys/random.h>
57 #include <dev/random/randomdev.h>
58
59 uint16_t
ip_randomid(uint64_t salt)60 ip_randomid(uint64_t salt)
61 {
62 uint16_t new_id;
63 /*
64 * Mostly the salt value is heap or stack pointer value.
65 * To avoid any chance of leaking address apply macro that
66 * adds per-boot random number to it.
67 */
68 uint64_t salt_tmp = VM_KERNEL_ADDRPERM(salt);
69
70 /*
71 * When the passed salt values are addresses, it is possible some bits
72 * to not change at all, for example some higher order bits may not change
73 * and some lower order bits may be all 0s given particular alignment and object
74 * sizes.
75 * Therefore we compute a XOR'd 16bit value by considering all the bits
76 * of the salt to increase the likelihood of it being different.
77 */
78 uint16_t new_id_salt = (uint16_t)(((salt_tmp >> 48) ^ (salt_tmp >> 32) ^
79 (salt_tmp >> 16) ^ salt_tmp) & 0xFF);
80
81 /* Avoid returning IP ID value of 0 */
82 do {
83 read_random(&new_id, sizeof(new_id));
84 } while (new_id == new_id_salt);
85
86 return new_id ^ new_id_salt;
87 }
88