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README for TF-PSA-Crypto

The TF-PSA-Crypto repository provides an implementation of the [PSA Cryptography API] (https://arm-software.github.io/psa-api) (version 1.1). This encompasses the on-going extensions to the PSA Cryptography API (e.g. PAKE).

The PSA Cryptography API implementation is organized around the PSA Cryptography driver interface aiming to ease the support of cryptographic accelerators and processors.

Configuration

The TF-PSA-Crypto repository should build out of the box on most systems. Its configuration is based on C preprocessor macros gathered in include/psa/crypto_config.h. The C preprocessor macros or configuration options are organized into four groups:

  1. General configuration options, options that are not related to a specific part of the implementation of the PSA Cryptography API.
  2. Configuration, using PSA_WANT_xxx macros as defined in psa-conditional-inclusion-c.md, of which parts of the PSA Cryptography API the user wishes to enable: cryptographic algorithms, key types, elliptic curves ...
  3. Configuration of the PSA cryptography core as defined in psa-driver-interface.md which provides the key management, the generation of random numbers and the dispatch to drivers.
  4. Configuration of the built-in implementation of the PSA driver interface as defined in psa-driver-interface.md: non-functional configuration related to performance/size trade-offs.

The file include/psa/crypto_config.h can be edited manually, or in a more programmatic way using the Python 3 script scripts/config.py (use --help for usage instructions).

Compiler options can be set using conventional environment variables such as CC and CFLAGS when using the CMake build system (see below).

Documentation

Documentation for the PSA Cryptography API is available on GitHub.

To generate a local copy of the library documentation in HTML format:

  1. Make sure that Doxygen is installed.
  2. Run mkdir /path/to/build_dir && cd /path/to/build_dir
  3. Run cmake /path/to/tf/psa/crypto/source
  4. Run make apidoc
  5. Browse apidoc/index.html or apidoc/modules.html.

Compiling

The build system is CMake. The CMake build system creates one library: libtfpsacrypto.

Tool versions

You need the following tools to build the library from the main branch with the provided CMake files. TF-PSA-Crypto minimum tool version requirements are set based on the versions shipped in the latest or penultimate (depending on the release cadence) long-term support releases of major Linux distributions, namely at time of writing: Ubuntu 20.04, RHEL 8, SLES 15 ...

  • A C99 toolchain (compiler, linker, archiver). We actively test with GCC 5.4, Clang 3.8. More recent versions should work. Slightly older versions may work.
  • Python 3.6.5 and later to generate some source files (see below), the test code, and to generate sample programs.
  • Perl to run the tests, and to generate some source files in the main branch.
  • CMake 3.16.3 or later.
  • Microsoft Visual Studio 2019 or later (if using Visual Studio).
  • Doxygen 1.8.14 or later.

Generated source files

The TF-PSA-Crypto build system generates some library, sample program and test C files as well as test data files. Their content depends only on the PSA cryptography source code, not on the platform or on the library configuration.

The following tools are required for the generation of those files:

  • Python 3 and some Python packages, for some library source files, sample programs and test data. To install the necessary packages, run 
    python3 -m pip install -r scripts/basic.requirements.txt
  • A C compiler for the host platform, for some test data.

When not cross-compiling, the build system generates the files automatically.

When cross-compiling, before to run the build system, you must set the CC environment variable to a C compiler for the host platform, then run tests/scripts/check-generated-files.sh -u.

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/tf/psa/crypto/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/tf/psa/crypto/source

To configure CMake for building shared libraries, use:

cmake -DUSE_SHARED_TF_PSA_CRYPTO_LIBRARY=On /path/to/tf/psa/crypto/source

There are many different build modes available within the CMake build system. 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.
  • 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/tf/psa/crypto/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/tf/psa/crypto/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, use:

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 TF-PSA-Crypto

The TF-PSA-Crypto repository provides a package config file for consumption as a dependency in other CMake projects. You can include TF-PSA-Crypto CMake targets yourself with:

find_package(TF-PSA-Crypto)

If prompted, set TF-PSA-Crypto_DIR to ${YOUR_TF_PSA_CRYPTO_INSTALL_DIR}/cmake. This creates the TF-PSA-Crypto::tfpsacrypto target.

You can then use it directly through target_link_libraries():

add_executable(xyz)

target_link_libraries(xyz PUBLIC TF-PSA-Crypto::tfpsacrypto)

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

TF-PSA-Crypto as a subproject

The TF-PSA-Crypto repository supports being built as a CMake subproject. One can use add_subdirectory() from a parent CMake project to include TF-PSA-Crypto as a subproject.

Microsoft Visual Studio

The TF-PSA-Crypto library can be built with Microsoft Visual Studio Community suitably installed as a CMake project. For a general documentation about CMake projects in Visual Studio, please refer to its documentation.

The following instructions have been tested on Microsoft Visual Studio Community 2019 Version 16.11.26. The TF-PSA-Crypto library and its tests build out of the box with: . Visual Studio Community installed with the default "Desktop development with C++" and "Python development" workloads. . Python libraries needed for code and test generation installed as defined in basic.requirements.txt. Refer to the Visual Studio documentation of Python environments. . When cloning the TF-PSA-Crypto repository in Visual Studio, a CMakeSettings.json is created at the root of the repository. In that file, add the line "environments": [ {"CC" : "cl"} ] to the configuration. That way when building the library and its tests, a CC environment variable is set with value "cl". This is needed by Python scripts that generate test cases. The CMakeSettings.json file can be edited in Visual Studio by following Project > CMake Settings for TF-PSA-Crypto > Edit JSON. . If necessary (it may have been done automatically when updating CMakeSettings.json), generate the CMake cache: Project > Generate Cache . Build the library: Build > Build All . The test suites can then be run: Test > Run CTests for TF-PSA-Crypto

Example programs

We've included example programs for different features and uses in programs/. Please note that the goal of these sample programs is to demonstrate specific features of the library, and the code may need to be adapted to build a real-world application.

Tests

The TF-PSA-Crypto repository includes an elaborate test suite in tests/ that initially requires Python to generate the tests files (e.g. test\_suite\_psa\_crypto.c). These files are generated from a function file (e.g. suites/test\_suite\_psa\_crypto.function) and a data file (e.g. suites/test\_suite\_psa\_crypto.data). The function file contains the test functions. The data file contains the test cases, specified as parameters that will be passed to the test function.

License

Unless specifically indicated otherwise in a file, TF-PSA-Crypto files are provided under the Apache-2.0 license. See the LICENSE file for the full text of this license. Contributors must accept that their contributions are made under the Apache-2.0 license.