- Added a generic entropy accumulator that provides support for adding custom entropy sources and added some generic and platform dependent entropy sources

library/entropy.c

@@ -0,0 +1,173 @@
+/*
+ *  Entropy accumulator implementation
+ *
+ *  Copyright (C) 2006-2011, Brainspark B.V.
+ *
+ *  This file is part of PolarSSL (http://www.polarssl.org)
+ *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ *  All rights reserved.
+ *
+ *  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.
+ *
+ *  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 Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "polarssl/config.h"
+
+#if defined(POLARSSL_ENTROPY_C)
+
+#include "polarssl/entropy.h"
+#include "polarssl/entropy_poll.h"
+
+#define ENTROPY_MAX_LOOP    256     /**< Maximum amount to loop before error */
+
+void entropy_init( entropy_context *ctx )
+{
+    memset( ctx, 0, sizeof(entropy_context) );
+
+    sha4_starts( &ctx->accumulator, 0 );
+
+#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
+    entropy_add_source( ctx, platform_entropy_poll, NULL );
+#endif
+#if defined(POLARSSL_TIMING_C)
+    entropy_add_source( ctx, hardclock_poll, NULL );
+#endif
+}
+
+int entropy_add_source( entropy_context *ctx,
+                        f_source_ptr f_source, void *p_source )
+{
+    if( ctx->source_count >= ENTROPY_MAX_SOURCES )
+        return( POLARSSL_ERR_ENTROPY_MAX_SOURCES );
+
+    ctx->f_source[ctx->source_count] = f_source;
+    ctx->p_source[ctx->source_count] = p_source;
+
+    ctx->source_count++;
+
+    return( 0 );
+}
+
+/*
+ * Entropy accumulator update
+ */
+int entropy_update( entropy_context *ctx, unsigned char source_id,
+                    const unsigned char *data, size_t len )
+{
+    unsigned char header[2];
+    unsigned char tmp[ENTROPY_BLOCK_SIZE];
+    size_t use_len = len;
+    const unsigned char *p = data;
+   
+    if( use_len > ENTROPY_BLOCK_SIZE )
+    {
+        sha4( data, len, tmp, 0 );
+
+        p = tmp;
+        use_len = ENTROPY_BLOCK_SIZE;
+    }
+
+    header[0] = source_id;
+    header[1] = use_len & 0xFF;
+
+    sha4_update( &ctx->accumulator, header, 2 );
+    sha4_update( &ctx->accumulator, p, use_len );
+    
+    ctx->size += use_len;
+
+    return( 0 );
+}
+
+int entropy_update_manual( entropy_context *ctx,
+                           const unsigned char *data, size_t len )
+{
+    return entropy_update( ctx, ENTROPY_SOURCE_MANUAL, data, len );
+}
+
+/*
+ * Run through the different sources to add entropy to our accumulator
+ */
+int entropy_gather( entropy_context *ctx )
+{
+    int ret, i;
+    unsigned char buf[ENTROPY_MAX_GATHER];
+    size_t olen;
+    
+    /*
+     * Run through our entropy sources
+     */
+    for( i = 0; i < ctx->source_count; i++ )
+    {
+        olen = 0;
+        if ( ( ret = ctx->f_source[i]( ctx->p_source[i],
+                        buf, ENTROPY_MAX_GATHER, &olen ) ) != 0 )
+        {
+            return( ret );
+        }
+
+        /*
+         * Add if we actually gathered something
+         */
+        if( olen > 0 )
+            entropy_update( ctx, (unsigned char) i, buf, olen );
+    }
+
+    return( 0 );
+}
+
+int entropy_func( void *data, unsigned char *output, size_t len )
+{
+    int ret, count = 0;
+    entropy_context *ctx = (entropy_context *) data;
+    unsigned char buf[ENTROPY_BLOCK_SIZE];
+
+    if( len > ENTROPY_BLOCK_SIZE )
+        return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
+
+    /*
+     * Always gather extra entropy before a call
+     */
+    do
+    {
+        if( count++ > ENTROPY_MAX_LOOP )
+            return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
+
+        if( ( ret = entropy_gather( ctx ) ) != 0 )
+            return( ret );
+    }
+    while( ctx->size < ENTROPY_MIN_POOL );
+
+    memset( buf, 0, ENTROPY_BLOCK_SIZE );
+
+    sha4_finish( &ctx->accumulator, buf );
+                
+    /*
+     * Perform second SHA-512 on entropy
+     */
+    sha4( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
+
+    /*
+     * Reset accumulator
+     */
+    memset( &ctx->accumulator, 0, sizeof( sha4_context ) );
+    sha4_starts( &ctx->accumulator, 0 );
+    ctx->size = 0;
+
+    memcpy( output, buf, len );
+
+    return( 0 );
+}
+
+#endif