/* =================================================================== * * Copyright (c) 2014, Legrandin * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * =================================================================== */ #include "pycrypto_common.h" FAKE_INIT(chacha20) #define KEY_SIZE 32 #define NONCE_SIZE 8 typedef struct { /** Initial state for the next iteration **/ uint32_t h[16]; /** How many bytes at the beginning of the key stream * have already been used. */ uint8_t usedKeyStream; uint8_t keyStream[sizeof(uint32_t)*16]; } stream_state; static int littleEndian(void) { int test = 1; return *((uint8_t*)&test) == 1; } static void byteSwap(uint32_t *v) { union { uint32_t w; uint8_t b[4]; } x, y; x.w = *v; y.b[0] = x.b[3]; y.b[1] = x.b[2]; y.b[2] = x.b[1]; y.b[3] = x.b[0]; *v = y.w; } /** Convert status word from little endian to native and vice versa **/ static void fix_endianess(uint32_t h[16], unsigned start, unsigned end) { unsigned i; if (littleEndian()) return; for (i=start; i> (32 - (n)))) #define QR(a, b, c, d) {\ a+=b; d^=a; d=ROTL(d,16); \ c+=d; b^=c; b=ROTL(b,12); \ a+=b; d^=a; d=ROTL(d,8); \ c+=d; b^=c; b=ROTL(b,7); \ } EXPORT_SYM int chacha20_init(stream_state **pState, const uint8_t *key, size_t keySize, const uint8_t *nonce, size_t nonceSize) { stream_state *hs; if (NULL == pState || NULL == nonce) return ERR_NULL; if (NULL == key || keySize != KEY_SIZE) return ERR_KEY_SIZE; if (NULL == nonce || nonceSize != NONCE_SIZE) return ERR_NONCE_SIZE; *pState = hs = (stream_state*) calloc(1, sizeof(stream_state)); if (NULL == hs) return ERR_MEMORY; hs->h[0] = 0x61707865; hs->h[1] = 0x3320646e; hs->h[2] = 0x79622d32; hs->h[3] = 0x6b206574; memcpy(&hs->h[4], key, KEY_SIZE); fix_endianess(hs->h, 4, 12); memcpy(&hs->h[14], nonce, NONCE_SIZE); fix_endianess(hs->h, 14, 16); hs->usedKeyStream = sizeof hs->keyStream; return 0; } EXPORT_SYM int chacha20_destroy(stream_state *state) { if (NULL == state) return ERR_NULL; free(state); return 0; } static int chacha20_core(stream_state *state) { unsigned i; uint32_t h[16]; memcpy(h, state->h, sizeof h); for (i=0; i<10; i++) { /** Column round **/ QR(h[0], h[4], h[ 8], h[12]); QR(h[1], h[5], h[ 9], h[13]); QR(h[2], h[6], h[10], h[14]); QR(h[3], h[7], h[11], h[15]); /** Diagonal round **/ QR(h[0], h[5], h[10], h[15]); QR(h[1], h[6], h[11], h[12]); QR(h[2], h[7], h[ 8], h[13]); QR(h[3], h[4], h[ 9], h[14]); } for (i=0; i<16; i++) h[i] += state->h[i]; fix_endianess(h, 0, 16); memcpy(state->keyStream, h, sizeof h); state->usedKeyStream = 0; if (++state->h[12] == 0) { if (++state->h[13] == 0) { return ERR_MAX_DATA; } } return 0; } EXPORT_SYM int chacha20_encrypt(stream_state *state, const uint8_t in[], uint8_t out[], size_t len) { if (NULL == state || NULL == in || NULL == out) return ERR_NULL; while (len>0) { unsigned keyStreamToUse; unsigned i; if (state->usedKeyStream == sizeof state->keyStream) { int result; result = chacha20_core(state); if (result) return result; } keyStreamToUse = minAB(len, sizeof state->keyStream - state->usedKeyStream); for (i=0; ikeyStream[i + state->usedKeyStream]; len -= keyStreamToUse; state->usedKeyStream += keyStreamToUse; } return 0; } EXPORT_SYM int chacha20_seek(stream_state *state, unsigned long block_high, unsigned long block_low, unsigned offset) { int result; if (NULL == state) return ERR_NULL; if (offset >= sizeof state->keyStream) return ERR_MAX_OFFSET; state->h[12] = block_low; state->h[13] = block_high; result = chacha20_core(state); if (result) return result; state->usedKeyStream = offset; return 0; }