Import mbedtls-2.27.0

Imports Mbed TLS 2.27.0 from https://github.com/ARMmbed/mbedtls.git
commit f71e28780841 ("Merge pull request #843 from
paul-elliott-arm/mbedtls-2.27.0rc0-pr") (tag mbedtls-2.27.0, v2.27.0).

Files that are not needed are removed.

 cd lib/libmbedtls
 rm -rf mbedtls
 cp -R path/to/mbedtls-2.27.0/mbedtls .
 cd mbedtls
 rm CMakeLists.txt DartConfiguration.tcl Makefile
 rm .gitignore .travis.yml .pylintrc .globalrc .mypy.ini BRANCHES.md
 rm include/.gitignore include/CMakeLists.txt library/.gitignore
 rm library/CMakeLists.txt library/Makefile
 rm -rf .git .github doxygen configs programs scripts tests visualc yotta
 rm -rf 3rdparty ChangeLog.d docs
 rm -rf include/mbedtls/config_psa.h include/psa
 rm library/psa_* library/mps_*
 cd ..
 git add mbedtls

This is a complete overwrite of previous code so earlier changes in the
previous branch import/mbedtls-2.22.0 will be added on top of this commit.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
diff --git a/lib/libmbedtls/mbedtls/library/entropy.c b/lib/libmbedtls/mbedtls/library/entropy.c
index e40c8ec..12fd3b9 100644
--- a/lib/libmbedtls/mbedtls/library/entropy.c
+++ b/lib/libmbedtls/mbedtls/library/entropy.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  Entropy accumulator implementation
  *
- *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
+ *  Copyright The Mbed TLS Contributors
+ *  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.
@@ -15,15 +15,9 @@
  *  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
+#include "common.h"
 
 #if defined(MBEDTLS_ENTROPY_C)
 
@@ -122,6 +116,11 @@
 
 void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
 {
+    /* If the context was already free, don't call free() again.
+     * This is important for mutexes which don't allow double-free. */
+    if( ctx->accumulator_started == -1 )
+        return;
+
 #if defined(MBEDTLS_HAVEGE_C)
     mbedtls_havege_free( &ctx->havege_data );
 #endif
@@ -138,7 +137,7 @@
 #endif
     ctx->source_count = 0;
     mbedtls_platform_zeroize( ctx->source, sizeof( ctx->source ) );
-    ctx->accumulator_started = 0;
+    ctx->accumulator_started = -1;
 }
 
 int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
@@ -472,15 +471,21 @@
 #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;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    FILE *f = NULL;
     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 )
+    {
+        ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
         goto exit;
+    }
+
+    if( ( f = fopen( path, "wb" ) ) == NULL )
+    {
+        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
+        goto exit;
+    }
 
     if( fwrite( buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f ) != MBEDTLS_ENTROPY_BLOCK_SIZE )
     {
@@ -493,7 +498,9 @@
 exit:
     mbedtls_platform_zeroize( buf, sizeof( buf ) );
 
-    fclose( f );
+    if( f != NULL )
+        fclose( f );
+
     return( ret );
 }