Diff: polarssl/entropy.c

Revision:

0:137634ff4186

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/polarssl/entropy.c	Thu Jun 11 03:27:03 2015 +0000
@@ -0,0 +1,478 @@
+/*
+ *  Entropy accumulator implementation
+ *
+ *  Copyright (C) 2006-2014, ARM Limited, All Rights Reserved
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ *
+ *  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.
+ */
+
+#if !defined(POLARSSL_CONFIG_FILE)
+#include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
+
+#if defined(POLARSSL_ENTROPY_C)
+
+#include "polarssl/entropy.h"
+#include "polarssl/entropy_poll.h"
+
+#include <string.h>
+
+#if defined(POLARSSL_FS_IO)
+#include <stdio.h>
+#endif
+
+#if defined(POLARSSL_SELF_TEST)
+#if defined(POLARSSL_PLATFORM_C)
+#include "polarssl/platform.h"
+#else
+#include <stdio.h>
+#define polarssl_printf     printf
+#endif /* POLARSSL_PLATFORM_C */
+#endif /* POLARSSL_SELF_TEST */
+
+#if defined(POLARSSL_HAVEGE_C)
+#include "polarssl/havege.h"
+#endif
+
+/* Implementation that should never be optimized out by the compiler */
+static void polarssl_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+#define ENTROPY_MAX_LOOP    256     /**< Maximum amount to loop before error */
+
+void entropy_init( entropy_context *ctx )
+{
+    memset( ctx, 0, sizeof(entropy_context) );
+
+#if defined(POLARSSL_THREADING_C)
+    polarssl_mutex_init( &ctx->mutex );
+#endif
+
+#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
+    sha512_starts( &ctx->accumulator, 0 );
+#else
+    sha256_starts( &ctx->accumulator, 0 );
+#endif
+#if defined(POLARSSL_HAVEGE_C)
+    havege_init( &ctx->havege_data );
+#endif
+
+#if !defined(POLARSSL_NO_DEFAULT_ENTROPY_SOURCES)
+#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
+    entropy_add_source( ctx, platform_entropy_poll, NULL,
+                        ENTROPY_MIN_PLATFORM );
+#endif
+#if defined(POLARSSL_TIMING_C)
+    entropy_add_source( ctx, hardclock_poll, NULL, ENTROPY_MIN_HARDCLOCK );
+#endif
+#if defined(POLARSSL_HAVEGE_C)
+    entropy_add_source( ctx, havege_poll, &ctx->havege_data,
+                        ENTROPY_MIN_HAVEGE );
+#endif
+#endif /* POLARSSL_NO_DEFAULT_ENTROPY_SOURCES */
+}
+
+void entropy_free( entropy_context *ctx )
+{
+#if defined(POLARSSL_HAVEGE_C)
+    havege_free( &ctx->havege_data );
+#endif
+#if defined(POLARSSL_THREADING_C)
+    polarssl_mutex_free( &ctx->mutex );
+#endif
+    polarssl_zeroize( ctx, sizeof( entropy_context ) );
+}
+
+int entropy_add_source( entropy_context *ctx,
+                        f_source_ptr f_source, void *p_source,
+                        size_t threshold )
+{
+    int index, ret = 0;
+
+#if defined(POLARSSL_THREADING_C)
+    if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    index = ctx->source_count;
+    if( index >= ENTROPY_MAX_SOURCES )
+    {
+        ret = POLARSSL_ERR_ENTROPY_MAX_SOURCES;
+        goto exit;
+    }
+
+    ctx->source[index].f_source = f_source;
+    ctx->source[index].p_source = p_source;
+    ctx->source[index].threshold = threshold;
+
+    ctx->source_count++;
+
+exit:
+#if defined(POLARSSL_THREADING_C)
+    if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
+        return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Entropy accumulator update
+ */
+static 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 )
+    {
+#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
+        sha512( data, len, tmp, 0 );
+#else
+        sha256( data, len, tmp, 0 );
+#endif
+        p = tmp;
+        use_len = ENTROPY_BLOCK_SIZE;
+    }
+
+    header[0] = source_id;
+    header[1] = use_len & 0xFF;
+
+#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
+    sha512_update( &ctx->accumulator, header, 2 );
+    sha512_update( &ctx->accumulator, p, use_len );
+#else
+    sha256_update( &ctx->accumulator, header, 2 );
+    sha256_update( &ctx->accumulator, p, use_len );
+#endif
+
+    return( 0 );
+}
+
+int entropy_update_manual( entropy_context *ctx,
+                           const unsigned char *data, size_t len )
+{
+    int ret;
+
+#if defined(POLARSSL_THREADING_C)
+    if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    ret = entropy_update( ctx, ENTROPY_SOURCE_MANUAL, data, len );
+
+#if defined(POLARSSL_THREADING_C)
+    if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
+        return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Run through the different sources to add entropy to our accumulator
+ */
+static int entropy_gather_internal( entropy_context *ctx )
+{
+    int ret, i;
+    unsigned char buf[ENTROPY_MAX_GATHER];
+    size_t olen;
+
+    if( ctx->source_count == 0 )
+        return( POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED );
+
+    /*
+     * Run through our entropy sources
+     */
+    for( i = 0; i < ctx->source_count; i++ )
+    {
+        olen = 0;
+        if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
+                        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 );
+            ctx->source[i].size += olen;
+        }
+    }
+
+    return( 0 );
+}
+
+/*
+ * Thread-safe wrapper for entropy_gather_internal()
+ */
+int entropy_gather( entropy_context *ctx )
+{
+    int ret;
+
+#if defined(POLARSSL_THREADING_C)
+    if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    ret = entropy_gather_internal( ctx );
+
+#if defined(POLARSSL_THREADING_C)
+    if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
+        return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+int entropy_func( void *data, unsigned char *output, size_t len )
+{
+    int ret, count = 0, i, reached;
+    entropy_context *ctx = (entropy_context *) data;
+    unsigned char buf[ENTROPY_BLOCK_SIZE];
+
+    if( len > ENTROPY_BLOCK_SIZE )
+        return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
+
+#if defined(POLARSSL_THREADING_C)
+    if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    /*
+     * Always gather extra entropy before a call
+     */
+    do
+    {
+        if( count++ > ENTROPY_MAX_LOOP )
+        {
+            ret = POLARSSL_ERR_ENTROPY_SOURCE_FAILED;
+            goto exit;
+        }
+
+        if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
+            goto exit;
+
+        reached = 0;
+
+        for( i = 0; i < ctx->source_count; i++ )
+            if( ctx->source[i].size >= ctx->source[i].threshold )
+                reached++;
+    }
+    while( reached != ctx->source_count );
+
+    memset( buf, 0, ENTROPY_BLOCK_SIZE );
+
+#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
+    sha512_finish( &ctx->accumulator, buf );
+
+    /*
+     * Reset accumulator and counters and recycle existing entropy
+     */
+    memset( &ctx->accumulator, 0, sizeof( sha512_context ) );
+    sha512_starts( &ctx->accumulator, 0 );
+    sha512_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
+
+    /*
+     * Perform second SHA-512 on entropy
+     */
+    sha512( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
+#else /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
+    sha256_finish( &ctx->accumulator, buf );
+
+    /*
+     * Reset accumulator and counters and recycle existing entropy
+     */
+    memset( &ctx->accumulator, 0, sizeof( sha256_context ) );
+    sha256_starts( &ctx->accumulator, 0 );
+    sha256_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
+
+    /*
+     * Perform second SHA-256 on entropy
+     */
+    sha256( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
+#endif /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
+
+    for( i = 0; i < ctx->source_count; i++ )
+        ctx->source[i].size = 0;
+
+    memcpy( output, buf, len );
+
+    ret = 0;
+
+exit:
+#if defined(POLARSSL_THREADING_C)
+    if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
+        return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+#if defined(POLARSSL_FS_IO)
+int entropy_write_seed_file( entropy_context *ctx, const char *path )
+{
+    int ret = POLARSSL_ERR_ENTROPY_FILE_IO_ERROR;
+    FILE *f;
+    unsigned char buf[ENTROPY_BLOCK_SIZE];
+
+    if( ( f = fopen( path, "wb" ) ) == NULL )
+        return( POLARSSL_ERR_ENTROPY_FILE_IO_ERROR );
+
+    if( ( ret = entropy_func( ctx, buf, ENTROPY_BLOCK_SIZE ) ) != 0 )
+        goto exit;
+
+    if( fwrite( buf, 1, ENTROPY_BLOCK_SIZE, f ) != ENTROPY_BLOCK_SIZE )
+    {
+        ret = POLARSSL_ERR_ENTROPY_FILE_IO_ERROR;
+        goto exit;
+    }
+
+    ret = 0;
+
+exit:
+    fclose( f );
+    return( ret );
+}
+
+int entropy_update_seed_file( entropy_context *ctx, const char *path )
+{
+    FILE *f;
+    size_t n;
+    unsigned char buf[ ENTROPY_MAX_SEED_SIZE ];
+
+    if( ( f = fopen( path, "rb" ) ) == NULL )
+        return( POLARSSL_ERR_ENTROPY_FILE_IO_ERROR );
+
+    fseek( f, 0, SEEK_END );
+    n = (size_t) ftell( f );
+    fseek( f, 0, SEEK_SET );
+
+    if( n > ENTROPY_MAX_SEED_SIZE )
+        n = ENTROPY_MAX_SEED_SIZE;
+
+    if( fread( buf, 1, n, f ) != n )
+    {
+        fclose( f );
+        return( POLARSSL_ERR_ENTROPY_FILE_IO_ERROR );
+    }
+
+    fclose( f );
+
+    entropy_update_manual( ctx, buf, n );
+
+    return( entropy_write_seed_file( ctx, path ) );
+}
+#endif /* POLARSSL_FS_IO */
+
+#if defined(POLARSSL_SELF_TEST)
+/*
+ * Dummy source function
+ */
+static int entropy_dummy_source( void *data, unsigned char *output,
+                                 size_t len, size_t *olen )
+{
+    ((void) data);
+
+    memset( output, 0x2a, len );
+    *olen = len;
+
+    return( 0 );
+}
+
+/*
+ * The actual entropy quality is hard to test, but we can at least
+ * test that the functions don't cause errors and write the correct
+ * amount of data to buffers.
+ */
+int entropy_self_test( int verbose )
+{
+    int ret = 0;
+    entropy_context ctx;
+    unsigned char buf[ENTROPY_BLOCK_SIZE] = { 0 };
+    unsigned char acc[ENTROPY_BLOCK_SIZE] = { 0 };
+    size_t i, j;
+
+    if( verbose != 0 )
+        polarssl_printf( "  ENTROPY test: " );
+
+    entropy_init( &ctx );
+
+    ret = entropy_add_source( &ctx, entropy_dummy_source, NULL, 16 );
+    if( ret != 0 )
+        goto cleanup;
+
+    if( ( ret = entropy_gather( &ctx ) ) != 0 )
+        goto cleanup;
+
+    if( ( ret = entropy_update_manual( &ctx, buf, sizeof buf ) ) != 0 )
+        goto cleanup;
+
+    /*
+     * To test that entropy_func writes correct number of bytes:
+     * - use the whole buffer and rely on ASan to detect overruns
+     * - collect entropy 8 times and OR the result in an accumulator:
+     *   any byte should then be 0 with probably 2^(-64), so requiring
+     *   each of the 32 or 64 bytes to be non-zero has a false failure rate
+     *   of at most 2^(-58) which is acceptable.
+     */
+    for( i = 0; i < 8; i++ )
+    {
+        if( ( ret = entropy_func( &ctx, buf, sizeof( buf ) ) ) != 0 )
+            goto cleanup;
+
+        for( j = 0; j < sizeof( buf ); j++ )
+            acc[j] |= buf[j];
+    }
+
+    for( j = 0; j < sizeof( buf ); j++ )
+    {
+        if( acc[j] == 0 )
+        {
+            ret = 1;
+            goto cleanup;
+        }
+    }
+
+cleanup:
+    entropy_free( &ctx );
+
+    if( verbose != 0 )
+    {
+        if( ret != 0 )
+            polarssl_printf( "failed\n" );
+        else
+            polarssl_printf( "passed\n" );
+
+        polarssl_printf( "\n" );
+    }
+
+    return( ret != 0 );
+}
+#endif /* POLARSSL_SELF_TEST */
+
+#endif /* POLARSSL_ENTROPY_C */
+