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