Diff: mbedtls/source/entropy.c

Revision:

11:cada08fc8a70

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbedtls/source/entropy.c	Thu Jun 09 17:08:36 2016 +0000
@@ -0,0 +1,493 @@
+/*
+ *  Entropy accumulator implementation
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_ENTROPY_C)
+
+#include "mbedtls/entropy.h"
+#include "mbedtls/entropy_poll.h"
+
+#include <string.h>
+
+#if defined(MBEDTLS_FS_IO)
+#include <stdio.h>
+#endif
+
+#if defined(MBEDTLS_SELF_TEST)
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#define mbedtls_printf     printf
+#endif /* MBEDTLS_PLATFORM_C */
+#endif /* MBEDTLS_SELF_TEST */
+
+#if defined(MBEDTLS_HAVEGE_C)
+#include "mbedtls/havege.h"
+#endif
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_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 mbedtls_entropy_init( mbedtls_entropy_context *ctx )
+{
+    memset( ctx, 0, sizeof(mbedtls_entropy_context) );
+
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_init( &ctx->mutex );
+#endif
+
+#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
+    mbedtls_sha512_starts( &ctx->accumulator, 0 );
+#else
+    mbedtls_sha256_starts( &ctx->accumulator, 0 );
+#endif
+#if defined(MBEDTLS_HAVEGE_C)
+    mbedtls_havege_init( &ctx->havege_data );
+#endif
+
+#if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
+#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
+    mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,
+                                MBEDTLS_ENTROPY_MIN_PLATFORM,
+                                MBEDTLS_ENTROPY_SOURCE_STRONG );
+#endif
+#if defined(MBEDTLS_TIMING_C)
+    mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL,
+                                MBEDTLS_ENTROPY_MIN_HARDCLOCK,
+                                MBEDTLS_ENTROPY_SOURCE_WEAK );
+#endif
+#if defined(MBEDTLS_HAVEGE_C)
+    mbedtls_entropy_add_source( ctx, mbedtls_havege_poll, &ctx->havege_data,
+                                MBEDTLS_ENTROPY_MIN_HAVEGE,
+                                MBEDTLS_ENTROPY_SOURCE_STRONG );
+#endif
+#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
+    mbedtls_entropy_add_source( ctx, mbedtls_hardware_poll, NULL,
+                                MBEDTLS_ENTROPY_MIN_HARDWARE,
+                                MBEDTLS_ENTROPY_SOURCE_STRONG );
+#endif
+#endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
+}
+
+void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
+{
+#if defined(MBEDTLS_HAVEGE_C)
+    mbedtls_havege_free( &ctx->havege_data );
+#endif
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_free( &ctx->mutex );
+#endif
+    mbedtls_zeroize( ctx, sizeof( mbedtls_entropy_context ) );
+}
+
+int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
+                        mbedtls_entropy_f_source_ptr f_source, void *p_source,
+                        size_t threshold, int strong )
+{
+    int index, ret = 0;
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    index = ctx->source_count;
+    if( index >= MBEDTLS_ENTROPY_MAX_SOURCES )
+    {
+        ret = MBEDTLS_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[index].strong    = strong;
+
+    ctx->source_count++;
+
+exit:
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Entropy accumulator update
+ */
+static int entropy_update( mbedtls_entropy_context *ctx, unsigned char source_id,
+                           const unsigned char *data, size_t len )
+{
+    unsigned char header[2];
+    unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];
+    size_t use_len = len;
+    const unsigned char *p = data;
+
+    if( use_len > MBEDTLS_ENTROPY_BLOCK_SIZE )
+    {
+#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
+        mbedtls_sha512( data, len, tmp, 0 );
+#else
+        mbedtls_sha256( data, len, tmp, 0 );
+#endif
+        p = tmp;
+        use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
+    }
+
+    header[0] = source_id;
+    header[1] = use_len & 0xFF;
+
+#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
+    mbedtls_sha512_update( &ctx->accumulator, header, 2 );
+    mbedtls_sha512_update( &ctx->accumulator, p, use_len );
+#else
+    mbedtls_sha256_update( &ctx->accumulator, header, 2 );
+    mbedtls_sha256_update( &ctx->accumulator, p, use_len );
+#endif
+
+    return( 0 );
+}
+
+int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
+                           const unsigned char *data, size_t len )
+{
+    int ret;
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    ret = entropy_update( ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len );
+
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Run through the different sources to add entropy to our accumulator
+ */
+static int entropy_gather_internal( mbedtls_entropy_context *ctx )
+{
+    int ret, i, have_one_strong = 0;
+    unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
+    size_t olen;
+
+    if( ctx->source_count == 0 )
+        return( MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED );
+
+    /*
+     * Run through our entropy sources
+     */
+    for( i = 0; i < ctx->source_count; i++ )
+    {
+        if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
+            have_one_strong = 1;
+
+        olen = 0;
+        if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
+                        buf, MBEDTLS_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;
+        }
+    }
+
+    if( have_one_strong == 0 )
+        return( MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE );
+
+    return( 0 );
+}
+
+/*
+ * Thread-safe wrapper for entropy_gather_internal()
+ */
+int mbedtls_entropy_gather( mbedtls_entropy_context *ctx )
+{
+    int ret;
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    ret = entropy_gather_internal( ctx );
+
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
+{
+    int ret, count = 0, i, done;
+    mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
+    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
+
+    if( len > MBEDTLS_ENTROPY_BLOCK_SIZE )
+        return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    /*
+     * Always gather extra entropy before a call
+     */
+    do
+    {
+        if( count++ > ENTROPY_MAX_LOOP )
+        {
+            ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
+            goto exit;
+        }
+
+        if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
+            goto exit;
+
+        done = 1;
+        for( i = 0; i < ctx->source_count; i++ )
+            if( ctx->source[i].size < ctx->source[i].threshold )
+                done = 0;
+    }
+    while( ! done );
+
+    memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
+
+#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
+    mbedtls_sha512_finish( &ctx->accumulator, buf );
+
+    /*
+     * Reset accumulator and counters and recycle existing entropy
+     */
+    memset( &ctx->accumulator, 0, sizeof( mbedtls_sha512_context ) );
+    mbedtls_sha512_starts( &ctx->accumulator, 0 );
+    mbedtls_sha512_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
+
+    /*
+     * Perform second SHA-512 on entropy
+     */
+    mbedtls_sha512( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
+#else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
+    mbedtls_sha256_finish( &ctx->accumulator, buf );
+
+    /*
+     * Reset accumulator and counters and recycle existing entropy
+     */
+    memset( &ctx->accumulator, 0, sizeof( mbedtls_sha256_context ) );
+    mbedtls_sha256_starts( &ctx->accumulator, 0 );
+    mbedtls_sha256_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
+
+    /*
+     * Perform second SHA-256 on entropy
+     */
+    mbedtls_sha256( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
+#endif /* MBEDTLS_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(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+#if defined(MBEDTLS_FS_IO)
+int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path )
+{
+    int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
+    FILE *f;
+    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
+
+    if( ( f = fopen( path, "wb" ) ) == NULL )
+        return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
+
+    if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
+        goto exit;
+
+    if( fwrite( buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f ) != MBEDTLS_ENTROPY_BLOCK_SIZE )
+    {
+        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
+        goto exit;
+    }
+
+    ret = 0;
+
+exit:
+    fclose( f );
+    return( ret );
+}
+
+int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path )
+{
+    FILE *f;
+    size_t n;
+    unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
+
+    if( ( f = fopen( path, "rb" ) ) == NULL )
+        return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
+
+    fseek( f, 0, SEEK_END );
+    n = (size_t) ftell( f );
+    fseek( f, 0, SEEK_SET );
+
+    if( n > MBEDTLS_ENTROPY_MAX_SEED_SIZE )
+        n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
+
+    if( fread( buf, 1, n, f ) != n )
+    {
+        fclose( f );
+        return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
+    }
+
+    fclose( f );
+
+    mbedtls_entropy_update_manual( ctx, buf, n );
+
+    return( mbedtls_entropy_write_seed_file( ctx, path ) );
+}
+#endif /* MBEDTLS_FS_IO */
+
+#if defined(MBEDTLS_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 mbedtls_entropy_self_test( int verbose )
+{
+    int ret = 0;
+    mbedtls_entropy_context ctx;
+    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
+    unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
+    size_t i, j;
+
+    if( verbose != 0 )
+        mbedtls_printf( "  ENTROPY test: " );
+
+    mbedtls_entropy_init( &ctx );
+
+    /* First do a gather to make sure we have default sources */
+    if( ( ret = mbedtls_entropy_gather( &ctx ) ) != 0 )
+        goto cleanup;
+
+    ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16,
+                                      MBEDTLS_ENTROPY_SOURCE_WEAK );
+    if( ret != 0 )
+        goto cleanup;
+
+    if( ( ret = mbedtls_entropy_update_manual( &ctx, buf, sizeof buf ) ) != 0 )
+        goto cleanup;
+
+    /*
+     * To test that mbedtls_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 = mbedtls_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:
+    mbedtls_entropy_free( &ctx );
+
+    if( verbose != 0 )
+    {
+        if( ret != 0 )
+            mbedtls_printf( "failed\n" );
+        else
+            mbedtls_printf( "passed\n" );
+
+        mbedtls_printf( "\n" );
+    }
+
+    return( ret != 0 );
+}
+#endif /* MBEDTLS_SELF_TEST */
+
+#endif /* MBEDTLS_ENTROPY_C */