1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * The "hash function" used as the core of the ChaCha stream cipher (RFC7539) |
4 | * |
5 | * Copyright (C) 2015 Martin Willi |
6 | */ |
7 | |
8 | #include <linux/bug.h> |
9 | #include <linux/kernel.h> |
10 | #include <linux/export.h> |
11 | #include <linux/bitops.h> |
12 | #include <linux/string.h> |
13 | #include <asm/unaligned.h> |
14 | #include <crypto/chacha.h> |
15 | |
16 | static void chacha_permute(u32 *x, int nrounds) |
17 | { |
18 | int i; |
19 | |
20 | /* whitelist the allowed round counts */ |
21 | WARN_ON_ONCE(nrounds != 20 && nrounds != 12); |
22 | |
23 | for (i = 0; i < nrounds; i += 2) { |
24 | x[0] += x[4]; x[12] = rol32(word: x[12] ^ x[0], shift: 16); |
25 | x[1] += x[5]; x[13] = rol32(word: x[13] ^ x[1], shift: 16); |
26 | x[2] += x[6]; x[14] = rol32(word: x[14] ^ x[2], shift: 16); |
27 | x[3] += x[7]; x[15] = rol32(word: x[15] ^ x[3], shift: 16); |
28 | |
29 | x[8] += x[12]; x[4] = rol32(word: x[4] ^ x[8], shift: 12); |
30 | x[9] += x[13]; x[5] = rol32(word: x[5] ^ x[9], shift: 12); |
31 | x[10] += x[14]; x[6] = rol32(word: x[6] ^ x[10], shift: 12); |
32 | x[11] += x[15]; x[7] = rol32(word: x[7] ^ x[11], shift: 12); |
33 | |
34 | x[0] += x[4]; x[12] = rol32(word: x[12] ^ x[0], shift: 8); |
35 | x[1] += x[5]; x[13] = rol32(word: x[13] ^ x[1], shift: 8); |
36 | x[2] += x[6]; x[14] = rol32(word: x[14] ^ x[2], shift: 8); |
37 | x[3] += x[7]; x[15] = rol32(word: x[15] ^ x[3], shift: 8); |
38 | |
39 | x[8] += x[12]; x[4] = rol32(word: x[4] ^ x[8], shift: 7); |
40 | x[9] += x[13]; x[5] = rol32(word: x[5] ^ x[9], shift: 7); |
41 | x[10] += x[14]; x[6] = rol32(word: x[6] ^ x[10], shift: 7); |
42 | x[11] += x[15]; x[7] = rol32(word: x[7] ^ x[11], shift: 7); |
43 | |
44 | x[0] += x[5]; x[15] = rol32(word: x[15] ^ x[0], shift: 16); |
45 | x[1] += x[6]; x[12] = rol32(word: x[12] ^ x[1], shift: 16); |
46 | x[2] += x[7]; x[13] = rol32(word: x[13] ^ x[2], shift: 16); |
47 | x[3] += x[4]; x[14] = rol32(word: x[14] ^ x[3], shift: 16); |
48 | |
49 | x[10] += x[15]; x[5] = rol32(word: x[5] ^ x[10], shift: 12); |
50 | x[11] += x[12]; x[6] = rol32(word: x[6] ^ x[11], shift: 12); |
51 | x[8] += x[13]; x[7] = rol32(word: x[7] ^ x[8], shift: 12); |
52 | x[9] += x[14]; x[4] = rol32(word: x[4] ^ x[9], shift: 12); |
53 | |
54 | x[0] += x[5]; x[15] = rol32(word: x[15] ^ x[0], shift: 8); |
55 | x[1] += x[6]; x[12] = rol32(word: x[12] ^ x[1], shift: 8); |
56 | x[2] += x[7]; x[13] = rol32(word: x[13] ^ x[2], shift: 8); |
57 | x[3] += x[4]; x[14] = rol32(word: x[14] ^ x[3], shift: 8); |
58 | |
59 | x[10] += x[15]; x[5] = rol32(word: x[5] ^ x[10], shift: 7); |
60 | x[11] += x[12]; x[6] = rol32(word: x[6] ^ x[11], shift: 7); |
61 | x[8] += x[13]; x[7] = rol32(word: x[7] ^ x[8], shift: 7); |
62 | x[9] += x[14]; x[4] = rol32(word: x[4] ^ x[9], shift: 7); |
63 | } |
64 | } |
65 | |
66 | /** |
67 | * chacha_block_generic - generate one keystream block and increment block counter |
68 | * @state: input state matrix (16 32-bit words) |
69 | * @stream: output keystream block (64 bytes) |
70 | * @nrounds: number of rounds (20 or 12; 20 is recommended) |
71 | * |
72 | * This is the ChaCha core, a function from 64-byte strings to 64-byte strings. |
73 | * The caller has already converted the endianness of the input. This function |
74 | * also handles incrementing the block counter in the input matrix. |
75 | */ |
76 | void chacha_block_generic(u32 *state, u8 *stream, int nrounds) |
77 | { |
78 | u32 x[16]; |
79 | int i; |
80 | |
81 | memcpy(x, state, 64); |
82 | |
83 | chacha_permute(x, nrounds); |
84 | |
85 | for (i = 0; i < ARRAY_SIZE(x); i++) |
86 | put_unaligned_le32(val: x[i] + state[i], p: &stream[i * sizeof(u32)]); |
87 | |
88 | state[12]++; |
89 | } |
90 | EXPORT_SYMBOL(chacha_block_generic); |
91 | |
92 | /** |
93 | * hchacha_block_generic - abbreviated ChaCha core, for XChaCha |
94 | * @state: input state matrix (16 32-bit words) |
95 | * @stream: output (8 32-bit words) |
96 | * @nrounds: number of rounds (20 or 12; 20 is recommended) |
97 | * |
98 | * HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step |
99 | * towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha |
100 | * skips the final addition of the initial state, and outputs only certain words |
101 | * of the state. It should not be used for streaming directly. |
102 | */ |
103 | void hchacha_block_generic(const u32 *state, u32 *stream, int nrounds) |
104 | { |
105 | u32 x[16]; |
106 | |
107 | memcpy(x, state, 64); |
108 | |
109 | chacha_permute(x, nrounds); |
110 | |
111 | memcpy(&stream[0], &x[0], 16); |
112 | memcpy(&stream[4], &x[12], 16); |
113 | } |
114 | EXPORT_SYMBOL(hchacha_block_generic); |
115 | |