SEC: add generic interface for entropy pools.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4335 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/sec/entropy.h b/bertos/sec/entropy.h
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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2010 Develer S.r.l. (http://www.develer.com/)
+ *
+ * -->
+ *
+ * \brief Entropy pool generic interface
+ * \author Giovanni Bajo <rasky@develer.com>
+ * 
+ */
+
+#ifndef SEC_ENTROPY_H
+#define SEC_ENTROPY_H
+
+#include <cfg/compiler.h>
+#include <cfg/debug.h>
+
+/**
+ * Maximum number of different sources of entropy available in BeRTOS.
+ *
+ * Increasing this value will likely make entropy pools use more RAM for their operations,
+ * so it should be kept to the minimum necessary for a given project.
+ */
+#define CONFIG_ENTROPY_NUM_SOURCES   8
+
+typedef struct EntropyPool_Context
+{
+    void (*add_entropy)(struct EntropyPool_Context *ctx, int source_idx,
+                        const uint8_t *data, size_t len,
+                        int entropy);
+    bool (*seeding_ready)(struct EntropyPool_Context *ctx);
+    void (*make_seed)(struct EntropyPool_Context *ctx, uint8_t *out, size_t len);
+
+} EntropyPool_Context;
+
+
+/**
+ * Add some data samples containing entropy into the pool.
+ * the samples are in the buffer pointed by \a data for a total of \a len
+ * bytes. \a entropy is the number of bits of estimated entropy in the
+ * samples. \a source_idx is the index of the entropy source.
+ */
+INLINE void entropy_add(EntropyPool_Context *e, int source_idx, 
+                 const uint8_t *data, size_t len,
+                 int entropy)
+{
+    ASSERT(e->add_entropy);
+    e->add_entropy(e, source_idx, data, len, entropy); 
+}
+
+/**
+ * Check if the generator is ready to produce a new seed.
+ */
+INLINE bool entropy_seeding_ready(EntropyPool_Context *ctx)
+{
+    ASSERT(ctx->seeding_ready);
+    return ctx->seeding_ready(ctx);    
+}
+
+/**
+ * Generate a new seed of the specified length.
+ * 
+ * \note This should not be abused to generate a very long seed, since the pool
+ * cannot hold lots of entropy.
+ */
+INLINE void entropy_make_seed(EntropyPool_Context *ctx, uint8_t *out, size_t len)
+{
+    ASSERT(ctx->make_seed);
+    ctx->make_seed(ctx, out, len);     
+}
+
+#endif /* SEC_ENTROPY_H */