--- /dev/null
+/*
+ ---------------------------------------------------------------------------
+ Copyright (c) 2002, Dr Brian Gladman < >, Worcester, UK.
+ All rights reserved.
+
+ LICENSE TERMS
+
+ The free distribution and use of this software in both source and binary
+ form is allowed (with or without changes) provided that:
+
+ 1. distributions of this source code include the above copyright
+ notice, this list of conditions and the following disclaimer;
+
+ 2. distributions in binary form include the above copyright
+ notice, this list of conditions and the following disclaimer
+ in the documentation and/or other associated materials;
+
+ 3. the copyright holder's name is not used to endorse products
+ built using this software without specific written permission.
+
+ ALTERNATIVELY, provided that this notice is retained in full, this product
+ may be distributed under the terms of the GNU General Public License (GPL),
+ in which case the provisions of the GPL apply INSTEAD OF those given above.
+
+ DISCLAIMER
+
+ This software is provided 'as is' with no explicit or implied warranties
+ in respect of its properties, including, but not limited to, correctness
+ and/or fitness for purpose.
+ ---------------------------------------------------------------------------
+ Issue Date: 24/01/2003
+
+ This file implements a random data pool based on the use of an external
+ entropy function. It is based on the ideas advocated by Peter Gutmann in
+ his work on pseudo random sequence generators. It is not a 'paranoid'
+ random sequence generator and no attempt is made to protect the pool
+ from prying eyes either by memory locking or by techniques to obscure
+ its location in memory.
+*/
+
+#include <string.h>
+#include "prng.h"
+
+#if defined(__cplusplus)
+extern "C"
+{
+#endif
+
+/* mix a random data pool using the SHA1 compression function (as */
+/* suggested by Peter Gutmann in his paper on random pools) */
+
+static void prng_mix(unsigned char buf[])
+{ unsigned int i, len;
+ sha1_ctx ctx[1];
+
+ /*lint -e{663} unusual array to pointer conversion */
+ for(i = 0; i < PRNG_POOL_SIZE; i += SHA1_DIGEST_SIZE)
+ {
+ /* copy digest size pool block into SHA1 hash block */
+ memcpy(ctx->hash, buf + (i ? i : PRNG_POOL_SIZE)
+ - SHA1_DIGEST_SIZE, SHA1_DIGEST_SIZE);
+
+ /* copy data from pool into the SHA1 data buffer */
+ len = PRNG_POOL_SIZE - i;
+ memcpy(ctx->wbuf, buf + i, (len > SHA1_BLOCK_SIZE ? SHA1_BLOCK_SIZE : len));
+
+ if(len < SHA1_BLOCK_SIZE)
+ memcpy(((char*)ctx->wbuf) + len, buf, SHA1_BLOCK_SIZE - len);
+
+ /* compress using the SHA1 compression function */
+ sha1_compile(ctx);
+
+ /* put digest size block back into the random pool */
+ memcpy(buf + i, ctx->hash, SHA1_DIGEST_SIZE);
+ }
+}
+
+/* refresh the output buffer and update the random pool by adding */
+/* entropy and remixing */
+
+static void update_pool(prng_ctx ctx[1])
+{ unsigned int i = 0;
+
+ /* transfer random pool data to the output buffer */
+ memcpy(ctx->obuf, ctx->rbuf, PRNG_POOL_SIZE);
+
+ /* enter entropy data into the pool */
+ while(i < PRNG_POOL_SIZE)
+ i += ctx->entropy(ctx->rbuf + i, PRNG_POOL_SIZE - i);
+
+ /* invert and xor the original pool data into the pool */
+ for(i = 0; i < PRNG_POOL_SIZE; ++i)
+ ctx->rbuf[i] ^= ~ctx->obuf[i];
+
+ /* mix the pool and the output buffer */
+ prng_mix(ctx->rbuf);
+ prng_mix(ctx->obuf);
+}
+
+void prng_init(prng_entropy_fn fun, prng_ctx ctx[1])
+{ int i;
+
+ /* clear the buffers and the counter in the context */
+ memset(ctx, 0, sizeof(prng_ctx));
+
+ /* set the pointer to the entropy collection function */
+ ctx->entropy = fun;
+
+ /* initialise the random data pool */
+ update_pool(ctx);
+
+ /* mix the pool a minimum number of times */
+ for(i = 0; i < PRNG_MIN_MIX; ++i)
+ prng_mix(ctx->rbuf);
+
+ /* update the pool to prime the pool output buffer */
+ update_pool(ctx);
+}
+
+/* provide random bytes from the random data pool */
+
+void prng_rand(unsigned char data[], unsigned int data_len, prng_ctx ctx[1])
+{ unsigned char *rp = data;
+ unsigned int len, pos = ctx->pos;
+
+ while(data_len)
+ {
+ /* transfer 'data_len' bytes (or the number of bytes remaining */
+ /* the pool output buffer if less) into the output */
+ len = (data_len < PRNG_POOL_SIZE - pos ? data_len : PRNG_POOL_SIZE - pos);
+ memcpy(rp, ctx->obuf + pos, len);
+ rp += len; /* update ouput buffer position pointer */
+ pos += len; /* update pool output buffer pointer */
+ data_len -= len; /* update the remaining data count */
+
+ /* refresh the random pool if necessary */
+ if(pos == PRNG_POOL_SIZE)
+ {
+ update_pool(ctx); pos = 0;
+ }
+ }
+
+ ctx->pos = pos;
+}
+
+void prng_end(prng_ctx ctx[1])
+{
+ /* ensure the data in the context is destroyed */
+ memset(ctx, 0, sizeof(prng_ctx));
+}
+
+#if defined(__cplusplus)
+}
+#endif
+
fnp / wl-app.git / blobdiff