xof: Added ChaCha20 stream as XOF

2016-08-06 12:09:05 +02:00
parent 8993cb556e
commit 1fddb0b92e
9 changed files with 311 additions and 3 deletions
@@ -0,0 +1,166 @@
+/*
+ * Copyright (C) 2016 Andreas Steffen
+ * HSR Hochschule fuer Technik Rapperswil
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include "chapoly_xof.h"
+#include "chapoly_drv.h"
+
+typedef struct private_chapoly_xof_t private_chapoly_xof_t;
+
+/**
+ * Private data of an chapoly_xof_t object.
+ */
+struct private_chapoly_xof_t {
+
+	/**
+	 * Public chapoly_xof_t interface.
+	 */
+	chapoly_xof_t public;
+
+	/**
+	 * Latest block of the ChaCha20 stream.
+	 */
+	uint8_t stream[CHACHA_BLOCK_SIZE];
+
+	/**
+	 * Index pointing to the current position in the stream
+	 */
+	u_int stream_index;
+
+	/**
+	 * Driver backend
+	 */
+	chapoly_drv_t *drv;
+};
+
+METHOD(xof_t, get_bytes, bool,
+	private_chapoly_xof_t *this, size_t out_len, uint8_t *buffer)
+{
+	size_t index = 0, len, blocks;
+
+	/* empty the stream buffer first */
+	len = min(out_len, CHACHA_BLOCK_SIZE - this->stream_index);
+	if (len)
+	{
+		memcpy(buffer + index, this->stream + this->stream_index, len);
+		index += len;
+		this->stream_index += len;
+	}
+
+	/* copy whole stream blocks directly to output buffer */
+	blocks = (out_len - index) / CHACHA_BLOCK_SIZE;	
+	while (blocks--)
+	{
+		if (!this->drv->chacha(this->drv, buffer + index))
+		{
+			return FALSE;
+		}
+		index += CHACHA_BLOCK_SIZE;
+	}	
+	
+	/* refill the stream buffer if some more output bytes are needed */
+	len = out_len - index;
+	if (len)
+	{
+		if (!this->drv->chacha(this->drv, this->stream))
+		{
+			return FALSE;
+		}
+		memcpy(buffer + index, this->stream, len);
+		this->stream_index = len;
+	}		
+	
+	return TRUE;
+}
+
+METHOD(xof_t, allocate_bytes, bool,
+	private_chapoly_xof_t *this, size_t out_len, chunk_t *chunk)
+{
+	*chunk = chunk_alloc(out_len);
+
+	if (!get_bytes(this, out_len, chunk->ptr))
+	{
+		chunk_free(chunk);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+METHOD(xof_t, get_block_size, size_t,
+	private_chapoly_xof_t *this)
+{
+	return CHACHA_BLOCK_SIZE;
+}
+
+METHOD(xof_t, get_seed_size, size_t,
+	private_chapoly_xof_t *this)
+{
+	return CHACHA_KEY_SIZE + CHACHA_SALT_SIZE + CHACHA_IV_SIZE;
+}
+
+METHOD(xof_t, set_seed, bool,
+	private_chapoly_xof_t *this, chunk_t seed)
+{
+	this->stream_index = CHACHA_BLOCK_SIZE;
+
+	return  seed.len == get_seed_size(this) &&
+			this->drv->set_key(this->drv, "expand 32-byte k",
+							seed.ptr, seed.ptr + CHACHA_KEY_SIZE) &&
+			this->drv->init(this->drv,
+						 	seed.ptr + CHACHA_KEY_SIZE + CHACHA_SALT_SIZE);
+}
+
+METHOD(xof_t, destroy, void,
+	private_chapoly_xof_t *this)
+{
+	this->drv->destroy(this->drv);
+	free(this);
+}
+
+/**
+ * See header
+ */
+chapoly_xof_t *chapoly_xof_create(ext_out_function_t algorithm)
+{
+	private_chapoly_xof_t *this;
+	chapoly_drv_t *drv;
+
+	if (algorithm != XOF_CHACHA20)
+	{
+		return NULL;
+	}
+
+	drv = chapoly_drv_probe();
+	if (!drv)
+	{
+		return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.xof_interface = {
+				.get_bytes = _get_bytes,
+				.allocate_bytes = _allocate_bytes,
+				.get_block_size = _get_block_size,
+				.get_seed_size = _get_seed_size,
+				.set_seed = _set_seed,
+				.destroy = _destroy,
+			},
+		},
+		.drv = drv,
+	);
+
+	return &this->public;
+}