/* $OpenBSD: arc4random.c,v 1.54 2015/09/13 08:31:47 guenther Exp $ */ /* * Copyright (c) 1996, David Mazieres * Copyright (c) 2008, Damien Miller * Copyright (c) 2013, Markus Friedl * Copyright (c) 2014, Theo de Raadt * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* * ChaCha based random number generator for OpenBSD. */ /* * Adapted for VeraCrypt */ #include "chachaRng.h" #include "cpu.h" #include "misc.h" #include static VC_INLINE void ChaCha20RngReKey (ChaCha20RngCtx* pCtx, int useCallBack) { /* fill rs_buf with the keystream */ if (pCtx->m_rs_have) memset(pCtx->m_rs_buf + sizeof(pCtx->m_rs_buf) - pCtx->m_rs_have, 0, pCtx->m_rs_have); ChaCha256Encrypt(&pCtx->m_chachaCtx, pCtx->m_rs_buf, sizeof (pCtx->m_rs_buf), pCtx->m_rs_buf); /* mix in optional user provided data */ if (pCtx->m_getRandSeedCallback && useCallBack) { unsigned char dat[CHACHA20RNG_KEYSZ + CHACHA20RNG_IVSZ]; size_t i; pCtx->m_getRandSeedCallback (dat, sizeof (dat)); for (i = 0; i < (CHACHA20RNG_KEYSZ + CHACHA20RNG_IVSZ); i++) pCtx->m_rs_buf[i] ^= dat[i]; burn (dat, sizeof(dat)); } /* immediately reinit for backtracking resistance */ ChaCha256Init (&pCtx->m_chachaCtx, pCtx->m_rs_buf, pCtx->m_rs_buf + CHACHA20RNG_KEYSZ, 20); memset(pCtx->m_rs_buf, 0, CHACHA20RNG_KEYSZ + CHACHA20RNG_IVSZ); pCtx->m_rs_have = sizeof (pCtx->m_rs_buf) - CHACHA20RNG_KEYSZ - CHACHA20RNG_IVSZ; } static VC_INLINE void ChaCha20RngStir(ChaCha20RngCtx* pCtx) { ChaCha20RngReKey (pCtx, 1); /* invalidate rs_buf */ pCtx->m_rs_have = 0; memset(pCtx->m_rs_buf, 0, CHACHA20RNG_RSBUFSZ); pCtx->m_rs_count = 1600000; } static VC_INLINE void ChaCha20RngStirIfNeeded(ChaCha20RngCtx* pCtx, size_t len) { if (pCtx->m_rs_count <= len) { ChaCha20RngStir(pCtx); } else pCtx->m_rs_count -= len; } void ChaCha20RngInit (ChaCha20RngCtx* pCtx, const unsigned char* key, GetRandSeedFn rngSeedCallback, size_t InitialBytesToSkip) { ChaCha256Init (&pCtx->m_chachaCtx, key, key + 32, 20); pCtx->m_getRandSeedCallback = rngSeedCallback; /* fill rs_buf with the keystream */ pCtx->m_rs_have = 0; memset (pCtx->m_rs_buf, 0, sizeof (pCtx->m_rs_buf)); pCtx->m_rs_count = 1600000; ChaCha20RngReKey(pCtx, 0); if (InitialBytesToSkip) ChaCha20RngGetBytes (pCtx, NULL, InitialBytesToSkip); } void ChaCha20RngGetBytes (ChaCha20RngCtx* pCtx, unsigned char* buffer, size_t bufferLen) { unsigned char *buf = (unsigned char*) buffer; unsigned char* keystream; size_t m; ChaCha20RngStirIfNeeded(pCtx, bufferLen); while (bufferLen > 0) { if (pCtx->m_rs_have > 0) { m = VC_MIN(bufferLen, pCtx->m_rs_have); keystream = pCtx->m_rs_buf + sizeof(pCtx->m_rs_buf) - pCtx->m_rs_have; if (buf) { memcpy(buf, keystream, m); buf += m; } memset(keystream, 0, m); bufferLen -= m; pCtx->m_rs_have -= m; } if (pCtx->m_rs_have == 0) ChaCha20RngReKey (pCtx, 0); } } 'n4' href='#n4'>4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

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