blob: a46d2832dbabd094091a2432a08f69a491f20ade
1 | /* |
2 | * The "hash function" used as the core of the ChaCha stream cipher (RFC7539) |
3 | * |
4 | * Copyright (C) 2015 Martin Willi |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify |
7 | * it under the terms of the GNU General Public License as published by |
8 | * the Free Software Foundation; either version 2 of the License, or |
9 | * (at your option) any later version. |
10 | */ |
11 | |
12 | #include <linux/kernel.h> |
13 | #include <linux/export.h> |
14 | #include <linux/bitops.h> |
15 | #include <linux/cryptohash.h> |
16 | #include <asm/unaligned.h> |
17 | #include <crypto/chacha.h> |
18 | |
19 | static void chacha_permute(u32 *x, int nrounds) |
20 | { |
21 | int i; |
22 | |
23 | /* whitelist the allowed round counts */ |
24 | WARN_ON_ONCE(nrounds != 20 && nrounds != 12); |
25 | |
26 | for (i = 0; i < nrounds; i += 2) { |
27 | x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16); |
28 | x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16); |
29 | x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16); |
30 | x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16); |
31 | |
32 | x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12); |
33 | x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12); |
34 | x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12); |
35 | x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12); |
36 | |
37 | x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8); |
38 | x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8); |
39 | x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8); |
40 | x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8); |
41 | |
42 | x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7); |
43 | x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7); |
44 | x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7); |
45 | x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7); |
46 | |
47 | x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16); |
48 | x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16); |
49 | x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16); |
50 | x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16); |
51 | |
52 | x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12); |
53 | x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12); |
54 | x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12); |
55 | x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12); |
56 | |
57 | x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8); |
58 | x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8); |
59 | x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8); |
60 | x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8); |
61 | |
62 | x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7); |
63 | x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7); |
64 | x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7); |
65 | x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7); |
66 | } |
67 | } |
68 | |
69 | /** |
70 | * chacha_block - generate one keystream block and increment block counter |
71 | * @state: input state matrix (16 32-bit words) |
72 | * @stream: output keystream block (64 bytes) |
73 | * @nrounds: number of rounds (20 or 12; 20 is recommended) |
74 | * |
75 | * This is the ChaCha core, a function from 64-byte strings to 64-byte strings. |
76 | * The caller has already converted the endianness of the input. This function |
77 | * also handles incrementing the block counter in the input matrix. |
78 | */ |
79 | void chacha_block(u32 *state, u8 *stream, int nrounds) |
80 | { |
81 | u32 x[16]; |
82 | int i; |
83 | |
84 | memcpy(x, state, 64); |
85 | |
86 | chacha_permute(x, nrounds); |
87 | |
88 | for (i = 0; i < ARRAY_SIZE(x); i++) |
89 | put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]); |
90 | |
91 | state[12]++; |
92 | } |
93 | EXPORT_SYMBOL(chacha_block); |
94 | |
95 | /** |
96 | * hchacha_block - abbreviated ChaCha core, for XChaCha |
97 | * @in: input state matrix (16 32-bit words) |
98 | * @out: output (8 32-bit words) |
99 | * @nrounds: number of rounds (20 or 12; 20 is recommended) |
100 | * |
101 | * HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step |
102 | * towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha |
103 | * skips the final addition of the initial state, and outputs only certain words |
104 | * of the state. It should not be used for streaming directly. |
105 | */ |
106 | void hchacha_block(const u32 *in, u32 *out, int nrounds) |
107 | { |
108 | u32 x[16]; |
109 | |
110 | memcpy(x, in, 64); |
111 | |
112 | chacha_permute(x, nrounds); |
113 | |
114 | memcpy(&out[0], &x[0], 16); |
115 | memcpy(&out[4], &x[12], 16); |
116 | } |
117 | EXPORT_SYMBOL(hchacha_block); |
118 |