SEC: add generic interface for PRNGs.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4332 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/sec/prng.h b/bertos/sec/prng.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 Generic interface for cryptographically-secure pseudo-RNG
+ * \author Giovanni Bajo <rasky@develer.com>
+ * 
+ */
+
+#ifndef SEC_PRNG_H
+#define SEC_PRNG_H
+
+#include <cfg/compiler.h>
+#include <cfg/debug.h>
+
+typedef struct PRNG
+{   
+    void (*reseed)(struct PRNG *ctx, const uint8_t *seed);
+    void (*generate)(struct PRNG *ctx, uint8_t *data, size_t len);
+    size_t seed_len;   
+} PRNG;
+
+/**
+ * Feed a new seed into the PRNG.
+ * 
+ * \note: Being a cryptographically-secure PRNG, the seed will be
+ * mixed to the current state of the generator, so it is NOT possible
+ * to generate the same sequence simply by using the same seed. If you
+ * need such a property, use a normale PRGN like \a rand().
+ */
+INLINE void prng_reseed(PRNG *ctx, const uint8_t *seed)
+{
+    ASSERT(ctx->reseed);
+    ctx->reseed(ctx, seed);
+}
+
+/**
+ * Get the length of the seed in bytes required by this generator.
+ */
+INLINE size_t prng_seed_len(PRNG *ctx)
+{
+    return ctx->seed_len;
+}
+
+/**
+ * Generate some cryptographically-secure random bytes into the specified
+ * buffer.
+ */
+INLINE void prng_generate(PRNG *ctx, uint8_t *data, size_t len)
+{
+    ASSERT(ctx->generate);
+    ctx->generate(ctx, data, len);
+}
+
+
+#endif /* SEC_PRNG_H */