I would like to use the latest version of Mbed TLS (2.26.0) on the Thingy:91 and then realize a TLS connection using this version. As a first step I integrated this particular version of Mbed TLS into the at_client sample project. For this I followed the steps listed below. Good news is that it compiles and links.
When i compare my result with the Mbed TLS (2.16.8) integration provided by the SDK (CONFIG_MBEDTLS=y) I see that the two defines (MBEDTLS_NET_C, MBEDTLS_TIMING_C) are active in constrast to my approach. And that step 6 (check for is regular file) seems not to be necessary.
Therefore, I would like know how I can remove these differences?
Is there an easier way to reach my goal than the steps below? (Maybe via CONFIG_MBEDTLS_VANILLA_BACKEND ?)
Developing on Windows with SEGGER Embdedded Studio 5.34a and toolchain version 1.5.0 for target thingy91_nrf9160ns.
1. Copy include and library folder from Mbed TLS (github.com/.../mbedtls, tag 2.26.0) to at_client root folder (C:\Users\<username>\ncs\v1.5.0\nrf\samples\nrf9160\at_client)
2. Remove .gitignore, CMakeLists.txt from copied folders include and library
3. Remove Makefile from library
4. Edit CMakeLists.txt in at_client in order to add source and include files from Mbed TLS to the project and to define MBEDTLS_USE_PSA_CRYPTO, CONFIG_POSIX_FS. Add folder $ENV{ZEPHYR_BASE}/include/posix to provide dirent.h and sys/stat.h. CMakeLists.txt is as follows:
cmake_minimum_required(VERSION 3.13.1)
find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(NONE)
# NORDIC SDK APP START
file(GLOB app_sources library/*.c )
target_sources(app PRIVATE src/main.c ${app_sources})
target_compile_definitions(app PRIVATE MBEDTLS_USE_PSA_CRYPTO CONFIG_POSIX_FS)
target_include_directories(app PRIVATE library include include/mbedtls include/psa $ENV{ZEPHYR_BASE}/include/posix)
# NORDIC SDK APP END
4. Create at_client project in Segger Embedded Studio via File → Open nRF CONNECT SDK Project ...
Select thingy91_nrf9160ns as platform
5. In at_client project open include/mbedtls/config.h via File → Open and modify defines as follows
#define MBEDTLS_NO_PLATFORM_ENTROPY
//#define MBEDTLS_NET_C
//#define MBEDTLS_TIMING_C
6. In file library/x509_crt.c comment out two lines (1650,1651)
// if( !S_ISREG( sb.st_mode ) )
// continue;
Now the project builds (compiles and links) succesfully.
