tjh.dev
Linux kernel mirror (for testing)
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linux
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright 2018 Google LLC
4 */
5
6/*
7 * Implementation of the NH almost-universal hash function, specifically the
8 * variant of NH used in Adiantum. This is *not* a cryptographic hash function.
9 *
10 * Reference: section 6.3 of "Adiantum: length-preserving encryption for
11 * entry-level processors" (https://eprint.iacr.org/2018/720.pdf).
12 */
13
14#include <crypto/nh.h>
15#include <linux/export.h>
16#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/unaligned.h>
19
20#ifdef CONFIG_CRYPTO_LIB_NH_ARCH
21#include "nh.h" /* $(SRCARCH)/nh.h */
22#else
23static bool nh_arch(const u32 *key, const u8 *message, size_t message_len,
24 __le64 hash[NH_NUM_PASSES])
25{
26 return false;
27}
28#endif
29
30void nh(const u32 *key, const u8 *message, size_t message_len,
31 __le64 hash[NH_NUM_PASSES])
32{
33 u64 sums[4] = { 0, 0, 0, 0 };
34
35 if (nh_arch(key, message, message_len, hash))
36 return;
37
38 static_assert(NH_PAIR_STRIDE == 2);
39 static_assert(NH_NUM_PASSES == 4);
40
41 while (message_len) {
42 u32 m0 = get_unaligned_le32(message + 0);
43 u32 m1 = get_unaligned_le32(message + 4);
44 u32 m2 = get_unaligned_le32(message + 8);
45 u32 m3 = get_unaligned_le32(message + 12);
46
47 sums[0] += (u64)(u32)(m0 + key[0]) * (u32)(m2 + key[2]);
48 sums[1] += (u64)(u32)(m0 + key[4]) * (u32)(m2 + key[6]);
49 sums[2] += (u64)(u32)(m0 + key[8]) * (u32)(m2 + key[10]);
50 sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
51 sums[0] += (u64)(u32)(m1 + key[1]) * (u32)(m3 + key[3]);
52 sums[1] += (u64)(u32)(m1 + key[5]) * (u32)(m3 + key[7]);
53 sums[2] += (u64)(u32)(m1 + key[9]) * (u32)(m3 + key[11]);
54 sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
55 key += NH_MESSAGE_UNIT / sizeof(key[0]);
56 message += NH_MESSAGE_UNIT;
57 message_len -= NH_MESSAGE_UNIT;
58 }
59
60 hash[0] = cpu_to_le64(sums[0]);
61 hash[1] = cpu_to_le64(sums[1]);
62 hash[2] = cpu_to_le64(sums[2]);
63 hash[3] = cpu_to_le64(sums[3]);
64}
65EXPORT_SYMBOL_GPL(nh);
66
67#ifdef nh_mod_init_arch
68static int __init nh_mod_init(void)
69{
70 nh_mod_init_arch();
71 return 0;
72}
73subsys_initcall(nh_mod_init);
74
75static void __exit nh_mod_exit(void)
76{
77}
78module_exit(nh_mod_exit);
79#endif
80
81MODULE_DESCRIPTION("NH almost-universal hash function");
82MODULE_LICENSE("GPL");