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(x[12] ^ x[0], 16); 25 x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16); 26 x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16); 27 x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16); 28 29 x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12); 30 x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12); 31 x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12); 32 x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12); 33 34 x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8); 35 x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8); 36 x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8); 37 x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8); 38 39 x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7); 40 x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7); 41 x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7); 42 x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7); 43 44 x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16); 45 x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16); 46 x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16); 47 x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16); 48 49 x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12); 50 x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12); 51 x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12); 52 x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12); 53 54 x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8); 55 x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8); 56 x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8); 57 x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8); 58 59 x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7); 60 x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7); 61 x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7); 62 x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 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(x[i] + state[i], &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