1 /* 2 * Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 /* Adapted from the public domain code by D. Bernstein from SUPERCOP. */ 11 12 #include <string.h> 13 14 #include "internal/endian.h" 15 #include "crypto/chacha.h" 16 #include "crypto/ctype.h" 17 18 typedef unsigned int u32; 19 typedef unsigned char u8; 20 typedef union { 21 u32 u[16]; 22 u8 c[64]; 23 } chacha_buf; 24 25 # define ROTATE(v, n) (((v) << (n)) | ((v) >> (32 - (n)))) 26 27 # define U32TO8_LITTLE(p, v) do { \ 28 (p)[0] = (u8)(v >> 0); \ 29 (p)[1] = (u8)(v >> 8); \ 30 (p)[2] = (u8)(v >> 16); \ 31 (p)[3] = (u8)(v >> 24); \ 32 } while(0) 33 34 /* QUARTERROUND updates a, b, c, d with a ChaCha "quarter" round. */ 35 # define QUARTERROUND(a,b,c,d) ( \ 36 x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]),16), \ 37 x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]),12), \ 38 x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]), 8), \ 39 x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]), 7) ) 40 41 /* chacha_core performs 20 rounds of ChaCha on the input words in 42 * |input| and writes the 64 output bytes to |output|. */ 43 static void chacha20_core(chacha_buf *output, const u32 input[16]) 44 { 45 u32 x[16]; 46 int i; 47 DECLARE_IS_ENDIAN; 48 49 memcpy(x, input, sizeof(x)); 50 51 for (i = 20; i > 0; i -= 2) { 52 QUARTERROUND(0, 4, 8, 12); 53 QUARTERROUND(1, 5, 9, 13); 54 QUARTERROUND(2, 6, 10, 14); 55 QUARTERROUND(3, 7, 11, 15); 56 QUARTERROUND(0, 5, 10, 15); 57 QUARTERROUND(1, 6, 11, 12); 58 QUARTERROUND(2, 7, 8, 13); 59 QUARTERROUND(3, 4, 9, 14); 60 } 61 62 if (IS_LITTLE_ENDIAN) { 63 for (i = 0; i < 16; ++i) 64 output->u[i] = x[i] + input[i]; 65 } else { 66 for (i = 0; i < 16; ++i) 67 U32TO8_LITTLE(output->c + 4 * i, (x[i] + input[i])); 68 } 69 } 70 71 void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp, 72 size_t len, const unsigned int key[8], 73 const unsigned int counter[4]) 74 { 75 u32 input[16]; 76 chacha_buf buf; 77 size_t todo, i; 78 79 /* sigma constant "expand 32-byte k" in little-endian encoding */ 80 input[0] = ((u32)ossl_toascii('e')) | ((u32)ossl_toascii('x') << 8) 81 | ((u32)ossl_toascii('p') << 16) 82 | ((u32)ossl_toascii('a') << 24); 83 input[1] = ((u32)ossl_toascii('n')) | ((u32)ossl_toascii('d') << 8) 84 | ((u32)ossl_toascii(' ') << 16) 85 | ((u32)ossl_toascii('3') << 24); 86 input[2] = ((u32)ossl_toascii('2')) | ((u32)ossl_toascii('-') << 8) 87 | ((u32)ossl_toascii('b') << 16) 88 | ((u32)ossl_toascii('y') << 24); 89 input[3] = ((u32)ossl_toascii('t')) | ((u32)ossl_toascii('e') << 8) 90 | ((u32)ossl_toascii(' ') << 16) 91 | ((u32)ossl_toascii('k') << 24); 92 93 input[4] = key[0]; 94 input[5] = key[1]; 95 input[6] = key[2]; 96 input[7] = key[3]; 97 input[8] = key[4]; 98 input[9] = key[5]; 99 input[10] = key[6]; 100 input[11] = key[7]; 101 102 input[12] = counter[0]; 103 input[13] = counter[1]; 104 input[14] = counter[2]; 105 input[15] = counter[3]; 106 107 while (len > 0) { 108 todo = sizeof(buf); 109 if (len < todo) 110 todo = len; 111 112 chacha20_core(&buf, input); 113 114 for (i = 0; i < todo; i++) 115 out[i] = inp[i] ^ buf.c[i]; 116 out += todo; 117 inp += todo; 118 len -= todo; 119 120 /* 121 * Advance 32-bit counter. Note that as subroutine is so to 122 * say nonce-agnostic, this limited counter width doesn't 123 * prevent caller from implementing wider counter. It would 124 * simply take two calls split on counter overflow... 125 */ 126 input[12]++; 127 } 128 } 129