XUtils

mbedTLS

An open source, portable, easy to use, readable and flexible SSL library, previously known as PolarSSL. [Apache2] [website](https://tls.mbed.org/)

C/C++
https://github.com/ARMmbed/mbedtls

Make

We require GNU Make. To build the library and the sample programs, GNU Make and a C compiler are sufficient. Some of the more advanced build targets require some Unix/Linux tools.

We intentionally only use a minimum of functionality in the makefiles in order to keep them as simple and independent of different toolchains as possible, to allow users to more easily move between different platforms. Users who need more features are recommended to use CMake.

In order to build from the source code using GNU Make, just enter at the command line:

make

In order to run the tests, enter:

make check

The tests need Python to be built and Perl to be run. If you don’t have one of them installed, you can skip building the tests with:

make no_test

You’ll still be able to run a much smaller set of tests with:

programs/test/selftest

In order to build for a Windows platform, you should use WINDOWS_BUILD=1 if the target is Windows but the build environment is Unix-like (for instance when cross-compiling, or compiling from an MSYS shell), and WINDOWS=1 if the build environment is a Windows shell (for instance using mingw32-make) (in that case some targets will not be available).

Setting the variable SHARED in your environment will build shared libraries in addition to the static libraries. Setting DEBUG gives you a debug build. You can override CFLAGS and LDFLAGS by setting them in your environment or on the make command line; compiler warning options may be overridden separately using WARNING_CFLAGS. Some directory-specific options (for example, -I directives) are still preserved.

Please note that setting CFLAGS overrides its default value of -O2 and setting WARNING_CFLAGS overrides its default value (starting with -Wall -Wextra), so if you just want to add some warning options to the default ones, you can do so by setting CFLAGS=-O2 -Werror for example. Setting WARNING_CFLAGS is useful when you want to get rid of its default content (for example because your compiler doesn’t accept -Wall as an option). Directory-specific options cannot be overridden from the command line.

Depending on your platform, you might run into some issues. Please check the Makefiles in library/, programs/ and tests/ for options to manually add or remove for specific platforms. You can also check the Mbed TLS Knowledge Base for articles on your platform or issue.

In case you find that you need to do something else as well, please let us know what, so we can add it to the Mbed TLS Knowledge Base.

CMake

In order to build the source using CMake in a separate directory (recommended), just enter at the command line:

mkdir /path/to/build_dir && cd /path/to/build_dir
cmake /path/to/mbedtls_source
cmake --build .

In order to run the tests, enter:

ctest

The test suites need Python to be built and Perl to be executed. If you don’t have one of these installed, you’ll want to disable the test suites with:

cmake -DENABLE_TESTING=Off /path/to/mbedtls_source

If you disabled the test suites, but kept the programs enabled, you can still run a much smaller set of tests with:

programs/test/selftest

To configure CMake for building shared libraries, use:

cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On /path/to/mbedtls_source

There are many different build modes available within the CMake buildsystem. Most of them are available for gcc and clang, though some are compiler-specific:

  • Release. This generates the default code without any unnecessary information in the binary files.
  • Debug. This generates debug information and disables optimization of the code.
  • Coverage. This generates code coverage information in addition to debug information.
  • ASan. This instruments the code with AddressSanitizer to check for memory errors. (This includes LeakSanitizer, with recent version of gcc and clang.) (With recent version of clang, this mode also instruments the code with UndefinedSanitizer to check for undefined behaviour.)
  • ASanDbg. Same as ASan but slower, with debug information and better stack traces.
  • MemSan. This instruments the code with MemorySanitizer to check for uninitialised memory reads. Experimental, needs recent clang on Linux/x86_64.
  • MemSanDbg. Same as MemSan but slower, with debug information, better stack traces and origin tracking.
  • Check. This activates the compiler warnings that depend on optimization and treats all warnings as errors.

Switching build modes in CMake is simple. For debug mode, enter at the command line:

cmake -D CMAKE_BUILD_TYPE=Debug /path/to/mbedtls_source

To list other available CMake options, use:

cmake -LH

Note that, with CMake, you can’t adjust the compiler or its flags after the initial invocation of cmake. This means that CC=your_cc make and make CC=your_cc will not work (similarly with CFLAGS and other variables). These variables need to be adjusted when invoking cmake for the first time, for example:

CC=your_cc cmake /path/to/mbedtls_source

If you already invoked cmake and want to change those settings, you need to remove the build directory and create it again.

Note that it is possible to build in-place; this will however overwrite the provided Makefiles (see scripts/tmp_ignore_makefiles.sh if you want to prevent git status from showing them as modified). In order to do so, from the Mbed TLS source directory, use:

cmake .
make

If you want to change CC or CFLAGS afterwards, you will need to remove the CMake cache. This can be done with the following command using GNU find:

find . -iname '*cmake*' -not -name CMakeLists.txt -exec rm -rf {} +

You can now make the desired change:

CC=your_cc cmake .
make

Regarding variables, also note that if you set CFLAGS when invoking cmake, your value of CFLAGS doesn’t override the content provided by cmake (depending on the build mode as seen above), it’s merely prepended to it.

Consuming Mbed TLS

Mbed TLS provides a package config file for consumption as a dependency in other CMake projects. You can include Mbed TLS’s CMake targets yourself with:

find_package(MbedTLS)

If prompted, set MbedTLS_DIR to ${YOUR_MBEDTLS_INSTALL_DIR}/cmake. This creates the following targets:

  • MbedTLS::mbedcrypto (Crypto library)
  • MbedTLS::mbedtls (TLS library)
  • MbedTLS::mbedx509 (X509 library)

You can then use these directly through target_link_libraries():

add_executable(xyz)

target_link_libraries(xyz
    PUBLIC MbedTLS::mbedtls
           MbedTLS::mbedcrypto
           MbedTLS::mbedx509)

This will link the Mbed TLS libraries to your library or application, and add its include directories to your target (transitively, in the case of PUBLIC or INTERFACE link libraries).

Articles

  • coming soon...