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/base64.c b/lib/libmbedtls/mbedtls/library/base64.c
index 0401c06..1a05226 100644
--- a/lib/libmbedtls/mbedtls/library/base64.c
+++ b/lib/libmbedtls/mbedtls/library/base64.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  RFC 1521 base64 encoding/decoding
  *
- *  Copyright (C) 2006-2015, 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_BASE64_C)
 
@@ -72,6 +66,99 @@
 #define BASE64_SIZE_T_MAX   ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
 
 /*
+ * Constant flow conditional assignment to unsigned char
+ */
+static void mbedtls_base64_cond_assign_uchar( unsigned char * dest, const unsigned char * const src,
+                                       unsigned char condition )
+{
+    /* MSVC has a warning about unary minus on unsigned integer types,
+     * but this is well-defined and precisely what we want to do here. */
+#if defined(_MSC_VER)
+#pragma warning( push )
+#pragma warning( disable : 4146 )
+#endif
+
+    /* Generate bitmask from condition, mask will either be 0xFF or 0 */
+    unsigned char mask = ( condition | -condition );
+    mask >>= 7;
+    mask = -mask;
+
+#if defined(_MSC_VER)
+#pragma warning( pop )
+#endif
+
+    *dest = ( ( *src ) & mask ) | ( ( *dest ) & ~mask );
+}
+
+/*
+ * Constant flow conditional assignment to uint_32
+ */
+static void mbedtls_base64_cond_assign_uint32( uint32_t * dest, const uint32_t src,
+                                       uint32_t condition )
+{
+    /* MSVC has a warning about unary minus on unsigned integer types,
+     * but this is well-defined and precisely what we want to do here. */
+#if defined(_MSC_VER)
+#pragma warning( push )
+#pragma warning( disable : 4146 )
+#endif
+
+    /* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */
+    uint32_t mask = ( condition | -condition );
+    mask >>= 31;
+    mask = -mask;
+
+#if defined(_MSC_VER)
+#pragma warning( pop )
+#endif
+
+    *dest = ( src & mask ) | ( ( *dest ) & ~mask );
+}
+
+/*
+ * Constant flow check for equality
+ */
+static unsigned char mbedtls_base64_eq( size_t in_a, size_t in_b )
+{
+    size_t difference = in_a ^ in_b;
+
+    /* MSVC has a warning about unary minus on unsigned integer types,
+     * but this is well-defined and precisely what we want to do here. */
+#if defined(_MSC_VER)
+#pragma warning( push )
+#pragma warning( disable : 4146 )
+#endif
+
+    difference |= -difference;
+
+#if defined(_MSC_VER)
+#pragma warning( pop )
+#endif
+
+    /* cope with the varying size of size_t per platform */
+    difference >>= ( sizeof( difference ) * 8 - 1 );
+
+    return (unsigned char) ( 1 ^ difference );
+}
+
+/*
+ * Constant flow lookup into table.
+ */
+static unsigned char mbedtls_base64_table_lookup( const unsigned char * const table,
+                                                 const size_t table_size, const size_t table_index )
+{
+    size_t i;
+    unsigned char result = 0;
+
+    for( i = 0; i < table_size; ++i )
+    {
+        mbedtls_base64_cond_assign_uchar( &result, &table[i], mbedtls_base64_eq( i, table_index ) );
+    }
+
+    return result;
+}
+
+/*
  * Encode a buffer into base64 format
  */
 int mbedtls_base64_encode( unsigned char *dst, size_t dlen, size_t *olen,
@@ -111,10 +198,17 @@
         C2 = *src++;
         C3 = *src++;
 
-        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
-        *p++ = base64_enc_map[(((C1 &  3) << 4) + (C2 >> 4)) & 0x3F];
-        *p++ = base64_enc_map[(((C2 & 15) << 2) + (C3 >> 6)) & 0x3F];
-        *p++ = base64_enc_map[C3 & 0x3F];
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( ( C1 >> 2 ) & 0x3F ) );
+
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( ( ( ( C1 &  3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
+
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) ) & 0x3F ) );
+
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( C3 & 0x3F ) );
     }
 
     if( i < slen )
@@ -122,11 +216,15 @@
         C1 = *src++;
         C2 = ( ( i + 1 ) < slen ) ? *src++ : 0;
 
-        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
-        *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( ( C1 >> 2 ) & 0x3F ) );
+
+        *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                            ( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) ) & 0x3F ) );
 
         if( ( i + 1 ) < slen )
-             *p++ = base64_enc_map[((C2 & 15) << 2) & 0x3F];
+             *p++ = mbedtls_base64_table_lookup( base64_enc_map, sizeof( base64_enc_map ),
+                                                 ( ( ( C2 & 15 ) << 2 ) & 0x3F ) );
         else *p++ = '=';
 
         *p++ = '=';
@@ -147,6 +245,7 @@
     size_t i, n;
     uint32_t j, x;
     unsigned char *p;
+    unsigned char dec_map_lookup;
 
     /* First pass: check for validity and get output length */
     for( i = n = j = 0; i < slen; i++ )
@@ -177,10 +276,12 @@
         if( src[i] == '=' && ++j > 2 )
             return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
 
-        if( src[i] > 127 || base64_dec_map[src[i]] == 127 )
+        dec_map_lookup = mbedtls_base64_table_lookup( base64_dec_map, sizeof( base64_dec_map ), src[i] );
+
+        if( src[i] > 127 || dec_map_lookup == 127 )
             return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
 
-        if( base64_dec_map[src[i]] < 64 && j != 0 )
+        if( dec_map_lookup < 64 && j != 0 )
             return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
 
         n++;
@@ -210,8 +311,10 @@
         if( *src == '\r' || *src == '\n' || *src == ' ' )
             continue;
 
-        j -= ( base64_dec_map[*src] == 64 );
-        x  = ( x << 6 ) | ( base64_dec_map[*src] & 0x3F );
+        dec_map_lookup = mbedtls_base64_table_lookup( base64_dec_map, sizeof( base64_dec_map ), *src );
+
+        mbedtls_base64_cond_assign_uint32( &j, j - 1, mbedtls_base64_eq( dec_map_lookup, 64 ) );
+        x  = ( x << 6 ) | ( dec_map_lookup & 0x3F );
 
         if( ++n == 4 )
         {