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121 lines
3.6 KiB
C
121 lines
3.6 KiB
C
/*
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* Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/* Adapted from the public domain code by D. Bernstein from SUPERCOP. */
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#include <string.h>
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#include "internal/chacha.h"
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typedef unsigned int u32;
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typedef unsigned char u8;
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typedef union {
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u32 u[16];
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u8 c[64];
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} chacha_buf;
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# define ROTATE(v, n) (((v) << (n)) | ((v) >> (32 - (n))))
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# define U32TO8_LITTLE(p, v) do { \
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(p)[0] = (u8)(v >> 0); \
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(p)[1] = (u8)(v >> 8); \
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(p)[2] = (u8)(v >> 16); \
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(p)[3] = (u8)(v >> 24); \
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} while(0)
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/* QUARTERROUND updates a, b, c, d with a ChaCha "quarter" round. */
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# define QUARTERROUND(a,b,c,d) ( \
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x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]),16), \
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x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]),12), \
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x[a] += x[b], x[d] = ROTATE((x[d] ^ x[a]), 8), \
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x[c] += x[d], x[b] = ROTATE((x[b] ^ x[c]), 7) )
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/* chacha_core performs 20 rounds of ChaCha on the input words in
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* |input| and writes the 64 output bytes to |output|. */
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static void chacha20_core(chacha_buf *output, const u32 input[16])
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{
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u32 x[16];
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int i;
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const union {
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long one;
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char little;
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} is_endian = { 1 };
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memcpy(x, input, sizeof(x));
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for (i = 20; i > 0; i -= 2) {
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QUARTERROUND(0, 4, 8, 12);
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QUARTERROUND(1, 5, 9, 13);
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QUARTERROUND(2, 6, 10, 14);
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QUARTERROUND(3, 7, 11, 15);
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QUARTERROUND(0, 5, 10, 15);
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QUARTERROUND(1, 6, 11, 12);
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QUARTERROUND(2, 7, 8, 13);
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QUARTERROUND(3, 4, 9, 14);
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}
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if (is_endian.little) {
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for (i = 0; i < 16; ++i)
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output->u[i] = x[i] + input[i];
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} else {
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for (i = 0; i < 16; ++i)
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U32TO8_LITTLE(output->c + 4 * i, (x[i] + input[i]));
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}
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}
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void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
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size_t len, const unsigned int key[8],
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const unsigned int counter[4])
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{
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u32 input[16];
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chacha_buf buf;
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size_t todo, i;
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/* sigma constant "expand 32-byte k" in little-endian encoding */
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input[0] = ((u32)'e') | ((u32)'x'<<8) | ((u32)'p'<<16) | ((u32)'a'<<24);
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input[1] = ((u32)'n') | ((u32)'d'<<8) | ((u32)' '<<16) | ((u32)'3'<<24);
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input[2] = ((u32)'2') | ((u32)'-'<<8) | ((u32)'b'<<16) | ((u32)'y'<<24);
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input[3] = ((u32)'t') | ((u32)'e'<<8) | ((u32)' '<<16) | ((u32)'k'<<24);
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input[4] = key[0];
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input[5] = key[1];
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input[6] = key[2];
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input[7] = key[3];
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input[8] = key[4];
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input[9] = key[5];
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input[10] = key[6];
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input[11] = key[7];
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input[12] = counter[0];
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input[13] = counter[1];
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input[14] = counter[2];
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input[15] = counter[3];
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while (len > 0) {
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todo = sizeof(buf);
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if (len < todo)
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todo = len;
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chacha20_core(&buf, input);
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for (i = 0; i < todo; i++)
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out[i] = inp[i] ^ buf.c[i];
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out += todo;
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inp += todo;
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len -= todo;
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/*
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* Advance 32-bit counter. Note that as subroutine is so to
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* say nonce-agnostic, this limited counter width doesn't
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* prevent caller from implementing wider counter. It would
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* simply take two calls split on counter overflow...
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*/
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input[12]++;
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}
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}
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