VeraCrypt
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authorMounir IDRASSI <mounir.idrassi@idrix.fr>2019-02-08 01:48:12 +0100
committerMounir IDRASSI <mounir.idrassi@idrix.fr>2019-02-08 01:50:12 +0100
commitba5da0946c3abaa93d1161ca512c3c326cda3736 (patch)
tree128c238dea40ac0de0c7de8e0b02810eabc8e564 /src/Crypto/chachaRng.c
parente5b9cee8681dc45340321f759079b344a3b2676c (diff)
downloadVeraCrypt-ba5da0946c3abaa93d1161ca512c3c326cda3736.tar.gz
VeraCrypt-ba5da0946c3abaa93d1161ca512c3c326cda3736.zip
Windows: Add implementation of ChaCha20 based random generator. Use it for driver need of random bytes (currently only wipe bytes but more to come later).
Diffstat (limited to 'src/Crypto/chachaRng.c')
-rw-r--r--src/Crypto/chachaRng.c120
1 files changed, 120 insertions, 0 deletions
diff --git a/src/Crypto/chachaRng.c b/src/Crypto/chachaRng.c
new file mode 100644
index 00000000..b3d92039
--- /dev/null
+++ b/src/Crypto/chachaRng.c
@@ -0,0 +1,120 @@
+/* $OpenBSD: arc4random.c,v 1.54 2015/09/13 08:31:47 guenther Exp $ */
+
+/*
+ * Copyright (c) 1996, David Mazieres <dm@uun.org>
+ * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
+ * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
+ * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
+ *
+ * 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 <string.h>
+
+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);
+ }
+}