/* * Simple implementation of chacha20 used as a CSPRNG. * * Copyright (c) 2016 NORDUnet A/S * 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. * 3. Neither the name of the NORDUnet nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * 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 "cc20_prng.h" /* "expand 32-byte k" */ #define CHACHA20_CONSTANT0 0x61707865 #define CHACHA20_CONSTANT1 0x3320646e #define CHACHA20_CONSTANT2 0x79622d32 #define CHACHA20_CONSTANT3 0x6b206574 #ifdef CHACHA20_PRNG_DEBUG void _dump(struct cc20_state *cc, char *str); #endif inline uint32_t rotl32 (uint32_t x, uint32_t n) { return (x << n) | (x >> (32 - n)); } inline void _qr(struct cc20_state *cc, uint32_t a, uint32_t b, uint32_t c, uint32_t d) { cc->i[a] += cc->i[b]; cc->i[d] ^= cc->i[a]; cc->i[d] = rotl32(cc->i[d], 16); cc->i[c] += cc->i[d]; cc->i[b] ^= cc->i[c]; cc->i[b] = rotl32(cc->i[b], 12); cc->i[a] += cc->i[b]; cc->i[d] ^= cc->i[a]; cc->i[d] = rotl32(cc->i[d], 8); cc->i[c] += cc->i[d]; cc->i[b] ^= cc->i[c]; cc->i[b] = rotl32(cc->i[b], 7); } void chacha20_prng_reseed(struct cc20_state *cc, uint32_t *entropy) { uint32_t i = 256 / 8 / 4; while (i--) { cc->i[i] = entropy[i]; } } void chacha20_prng_block(struct cc20_state *cc, uint32_t block_counter, struct cc20_state *out) { uint32_t i; out->i[0] = CHACHA20_CONSTANT0; out->i[1] = CHACHA20_CONSTANT1; out->i[2] = CHACHA20_CONSTANT2; out->i[3] = CHACHA20_CONSTANT3; cc->i[12] = block_counter; for (i = 4; i < CHACHA20_NUM_WORDS; i++) { out->i[i] = cc->i[i]; } for (i = 10; i; i--) { _qr(out, 0, 4, 8,12); _qr(out, 1, 5, 9,13); _qr(out, 2, 6,10,14); _qr(out, 3, 7,11,15); _qr(out, 0, 5,10,15); _qr(out, 1, 6,11,12); _qr(out, 2, 7, 8,13); _qr(out, 3, 4, 9,14); } for (i = 0; i < CHACHA20_NUM_WORDS; i++) { out->i[i] += cc->i[i]; } } int chacha20_prng_self_test1() { /* Test vector from RFC7539, section 2.3.2. * https://tools.ietf.org/html/rfc7539#section-2.3.2 */ struct cc20_state test = { {0x61707865, 0x3320646e, 0x79622d32, 0x6b206574, 0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c, 0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c, 0x00000001, 0x09000000, 0x4a000000, 0x00000000, }}; struct cc20_state expected = { {0xe4e7f110, 0x15593bd1, 0x1fdd0f50, 0xc47120a3, 0xc7f4d1c7, 0x0368c033, 0x9aaa2204, 0x4e6cd4c3, 0x466482d2, 0x09aa9f07, 0x05d7c214, 0xa2028bd9, 0xd19c12b5, 0xb94e16de, 0xe883d0cb, 0x4e3c50a2, }}; uint32_t i; struct cc20_state out; #ifdef CHACHA20_PRNG_DEBUG _dump(&test, "Test vector from RFC7539, section 2.3.2. Input:"); #endif chacha20_prng_block(&test, 1, &out); #ifdef CHACHA20_PRNG_DEBUG _dump(&out, "Test vector from RFC7539, section 2.3.2. Output:"); #endif for (i = 0; i < CHACHA20_NUM_WORDS; i++) { if (out.i[i] != expected.i[i]) return 0; } return 1; } int chacha20_prng_self_test2() { /* Two-block test vector from RFC7539, section 2.4.2. * https://tools.ietf.org/html/rfc7539#section-2.4.2 */ struct cc20_state test = { {0x61707865, 0x3320646e, 0x79622d32, 0x6b206574, 0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c, 0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c, 0x00000001, 0x00000000, 0x4a000000, 0x00000000, }}; struct cc20_state expected1 = { {0xf3514f22, 0xe1d91b40, 0x6f27de2f, 0xed1d63b8, 0x821f138c, 0xe2062c3d, 0xecca4f7e, 0x78cff39e, 0xa30a3b8a, 0x920a6072, 0xcd7479b5, 0x34932bed, 0x40ba4c79, 0xcd343ec6, 0x4c2c21ea, 0xb7417df0, }}; struct cc20_state expected2 = { {0x9f74a669, 0x410f633f, 0x28feca22, 0x7ec44dec, 0x6d34d426, 0x738cb970, 0x3ac5e9f3, 0x45590cc4, 0xda6e8b39, 0x892c831a, 0xcdea67c1, 0x2b7e1d90, 0x037463f3, 0xa11a2073, 0xe8bcfb88, 0xedc49139, }}; struct cc20_state out; uint32_t i; #ifdef CHACHA20_PRNG_DEBUG _dump(&test, "Test vector from RFC7539, section 2.4.2. Input:"); #endif chacha20_prng_block(&test, 1, &out); #ifdef CHACHA20_PRNG_DEBUG _dump(&out, "First block"); #endif for (i = 0; i < CHACHA20_NUM_WORDS; i++) { if (out.i[i] != expected1.i[i]) return 0; } chacha20_prng_block(&test, 2, &out); #ifdef CHACHA20_PRNG_DEBUG _dump(&out, "Second block"); #endif for (i = 0; i < CHACHA20_NUM_WORDS; i++) { if (out.i[i] != expected2.i[i]) return 0; } return 1; } #ifdef CHACHA20_PRNG_DEBUG #include void _dump(struct cc20_state *cc, char *str) { uint32_t i; printf("%s\n", str); for (i = 0; i < 4; i++) { printf("%02i %08x %08x %08x %08x\n", i * 4, cc->i[i * 4 + 0], cc->i[i * 4 + 1], cc->i[i * 4 + 2], cc->i[i * 4 + 3]); } printf("\n"); } #endif /* Test vector from RFC, used as simple power-on self-test of ability to compute * a block correctly. */ int chacha20_prng_self_test() { return \ chacha20_prng_self_test1() && \ chacha20_prng_self_test2(); }