Line data Source code
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 :
16 200 : static void chacha_permute(u32 *x, int nrounds)
17 : {
18 : int i;
19 :
20 : /* whitelist the allowed round counts */
21 200 : WARN_ON_ONCE(nrounds != 20 && nrounds != 12);
22 :
23 2000 : for (i = 0; i < nrounds; i += 2) {
24 4000 : x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
25 4000 : x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
26 4000 : x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16);
27 4000 : x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
28 :
29 4000 : x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
30 4000 : x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
31 4000 : x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
32 4000 : x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
33 :
34 4000 : x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
35 4000 : x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
36 4000 : x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
37 4000 : x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
38 :
39 4000 : x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
40 4000 : x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
41 4000 : x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
42 4000 : x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
43 :
44 4000 : x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
45 4000 : x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
46 4000 : x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
47 4000 : x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
48 :
49 4000 : x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
50 4000 : x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
51 4000 : x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
52 4000 : x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
53 :
54 4000 : x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
55 4000 : x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
56 4000 : x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
57 4000 : x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
58 :
59 4000 : x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
60 4000 : x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
61 4000 : x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
62 4000 : x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
63 : }
64 200 : }
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 : */
76 200 : void chacha_block_generic(u32 *state, u8 *stream, int nrounds)
77 : {
78 : u32 x[16];
79 : int i;
80 :
81 400 : memcpy(x, state, 64);
82 :
83 200 : chacha_permute(x, nrounds);
84 :
85 3400 : for (i = 0; i < ARRAY_SIZE(x); i++)
86 6400 : put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
87 :
88 200 : state[12]++;
89 200 : }
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 0 : void hchacha_block_generic(const u32 *state, u32 *stream, int nrounds)
104 : {
105 : u32 x[16];
106 :
107 0 : memcpy(x, state, 64);
108 :
109 0 : chacha_permute(x, nrounds);
110 :
111 0 : memcpy(&stream[0], &x[0], 16);
112 0 : memcpy(&stream[4], &x[12], 16);
113 0 : }
114 : EXPORT_SYMBOL(hchacha_block_generic);
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