README.md
1README for Mbed TLS
2===================
3
4Mbed TLS is a C library that implements cryptographic primitives, X.509 certificate manipulation and the SSL/TLS and DTLS protocols. Its small code footprint makes it suitable for embedded systems.
5
6Mbed TLS includes a reference implementation of the [PSA Cryptography API](#psa-cryptography-api). This is currently a preview for evaluation purposes only.
7
8Configuration
9-------------
10
11Mbed TLS should build out of the box on most systems. Some platform specific options are available in the fully documented configuration file `include/mbedtls/mbedtls_config.h`, which is also the place where features can be selected. This file can be edited manually, or in a more programmatic way using the Python 3 script `scripts/config.py` (use `--help` for usage instructions).
12
13Compiler options can be set using conventional environment variables such as `CC` and `CFLAGS` when using the Make and CMake build system (see below).
14
15We provide some non-standard configurations focused on specific use cases in the `configs/` directory. You can read more about those in `configs/README.txt`
16
17Documentation
18-------------
19
20The main Mbed TLS documentation is available via [ReadTheDocs](https://mbed-tls.readthedocs.io/).
21
22Documentation for the PSA Cryptography API is available [on GitHub](https://arm-software.github.io/psa-api/crypto/).
23
24To generate a local copy of the library documentation in HTML format, tailored to your compile-time configuration:
25
261. Make sure that [Doxygen](http://www.doxygen.nl/) is installed.
271. Run `make apidoc`.
281. Browse `apidoc/index.html` or `apidoc/modules.html`.
29
30For other sources of documentation, see the [SUPPORT](SUPPORT.md) document.
31
32Compiling
33---------
34
35There are currently three active build systems used within Mbed TLS releases:
36
37- GNU Make
38- CMake
39- Microsoft Visual Studio
40
41The main systems used for development are CMake and GNU Make. Those systems are always complete and up-to-date. The others should reflect all changes present in the CMake and Make build system, although features may not be ported there automatically.
42
43The Make and CMake build systems create three libraries: libmbedcrypto, libmbedx509, and libmbedtls. Note that libmbedtls depends on libmbedx509 and libmbedcrypto, and libmbedx509 depends on libmbedcrypto. As a result, some linkers will expect flags to be in a specific order, for example the GNU linker wants `-lmbedtls -lmbedx509 -lmbedcrypto`.
44
45### Tool versions
46
47You need the following tools to build the library with the provided makefiles:
48
49* GNU Make 3.82 or a build tool that CMake supports.
50* A C99 toolchain (compiler, linker, archiver). We actively test with GCC 5.4, Clang 3.8, IAR 8 and Visual Studio 2013. More recent versions should work. Slightly older versions may work.
51* Python 3.6 to generate the test code, and to generate sample programs in the development branch.
52* Perl to run the tests, and to generate some source files in the development branch.
53* CMake 3.10.2 or later (if using CMake).
54* Microsoft Visual Studio 2013 or later (if using Visual Studio).
55* Doxygen 1.8.11 or later (if building the documentation; slightly older versions should work).
56
57### Generated source files in the development branch
58
59The source code of Mbed TLS includes some files that are automatically generated by scripts and whose content depends only on the Mbed TLS source, not on the platform or on the library configuration. These files are not included in the development branch of Mbed TLS, but the generated files are included in official releases. This section explains how to generate the missing files in the development branch.
60
61The following tools are required:
62
63* Perl, for some library source files and for Visual Studio build files.
64* Python 3 and some Python packages, for some library source files, sample programs and test data. To install the necessary packages, run:
65 ```
66 python3 -m pip install --user -r scripts/basic.requirements.txt
67 ```
68 Depending on your Python installation, you may need to invoke `python` instead of `python3`. To install the packages system-wide, omit the `--user` option.
69* A C compiler for the host platform, for some test data.
70
71If you are cross-compiling, you must set the `CC` environment variable to a C compiler for the host platform when generating the configuration-independent files.
72
73Any of the following methods are available to generate the configuration-independent files:
74
75* If not cross-compiling, running `make` with any target, or just `make`, will automatically generate required files.
76* On non-Windows systems, when not cross-compiling, CMake will generate the required files automatically.
77* Run `make generated_files` to generate all the configuration-independent files.
78* On Unix/POSIX systems, run `tests/scripts/check-generated-files.sh -u` to generate all the configuration-independent files.
79* On Windows, run `scripts\make_generated_files.bat` to generate all the configuration-independent files.
80
81### Make
82
83We 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.
84
85We 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.
86
87In order to build from the source code using GNU Make, just enter at the command line:
88
89 make
90
91In order to run the tests, enter:
92
93 make check
94
95The 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:
96
97 make no_test
98
99You'll still be able to run a much smaller set of tests with:
100
101 programs/test/selftest
102
103In 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).
104
105Setting 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.
106
107Please 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.
108
109Depending 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](https://mbed-tls.readthedocs.io/en/latest/kb/) for articles on your platform or issue.
110
111In 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](https://mbed-tls.readthedocs.io/en/latest/kb/).
112
113### CMake
114
115In order to build the source using CMake in a separate directory (recommended), just enter at the command line:
116
117 mkdir /path/to/build_dir && cd /path/to/build_dir
118 cmake /path/to/mbedtls_source
119 cmake --build .
120
121In order to run the tests, enter:
122
123 ctest
124
125The 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:
126
127 cmake -DENABLE_TESTING=Off /path/to/mbedtls_source
128
129If you disabled the test suites, but kept the programs enabled, you can still run a much smaller set of tests with:
130
131 programs/test/selftest
132
133To configure CMake for building shared libraries, use:
134
135 cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On /path/to/mbedtls_source
136
137There are many different build modes available within the CMake buildsystem. Most of them are available for gcc and clang, though some are compiler-specific:
138
139- `Release`. This generates the default code without any unnecessary information in the binary files.
140- `Debug`. This generates debug information and disables optimization of the code.
141- `Coverage`. This generates code coverage information in addition to debug information.
142- `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.)
143- `ASanDbg`. Same as ASan but slower, with debug information and better stack traces.
144- `MemSan`. This instruments the code with MemorySanitizer to check for uninitialised memory reads. Experimental, needs recent clang on Linux/x86\_64.
145- `MemSanDbg`. Same as MemSan but slower, with debug information, better stack traces and origin tracking.
146- `Check`. This activates the compiler warnings that depend on optimization and treats all warnings as errors.
147
148Switching build modes in CMake is simple. For debug mode, enter at the command line:
149
150 cmake -D CMAKE_BUILD_TYPE=Debug /path/to/mbedtls_source
151
152To list other available CMake options, use:
153
154 cmake -LH
155
156Note that, with CMake, you can't adjust the compiler or its flags after the
157initial invocation of cmake. This means that `CC=your_cc make` and `make
158CC=your_cc` will *not* work (similarly with `CFLAGS` and other variables).
159These variables need to be adjusted when invoking cmake for the first time,
160for example:
161
162 CC=your_cc cmake /path/to/mbedtls_source
163
164If you already invoked cmake and want to change those settings, you need to
165remove the build directory and create it again.
166
167Note that it is possible to build in-place; this will however overwrite the
168provided Makefiles (see `scripts/tmp_ignore_makefiles.sh` if you want to
169prevent `git status` from showing them as modified). In order to do so, from
170the Mbed TLS source directory, use:
171
172 cmake .
173 make
174
175If you want to change `CC` or `CFLAGS` afterwards, you will need to remove the
176CMake cache. This can be done with the following command using GNU find:
177
178 find . -iname '*cmake*' -not -name CMakeLists.txt -exec rm -rf {} +
179
180You can now make the desired change:
181
182 CC=your_cc cmake .
183 make
184
185Regarding variables, also note that if you set CFLAGS when invoking cmake,
186your value of CFLAGS doesn't override the content provided by cmake (depending
187on the build mode as seen above), it's merely prepended to it.
188
189#### Consuming Mbed TLS
190
191Mbed TLS provides a package config file for consumption as a dependency in other
192CMake projects. You can include Mbed TLS's CMake targets yourself with:
193
194 find_package(MbedTLS)
195
196If prompted, set `MbedTLS_DIR` to `${YOUR_MBEDTLS_INSTALL_DIR}/cmake`. This
197creates the following targets:
198
199- `MbedTLS::mbedcrypto` (Crypto library)
200- `MbedTLS::mbedtls` (TLS library)
201- `MbedTLS::mbedx509` (X509 library)
202
203You can then use these directly through `target_link_libraries()`:
204
205 add_executable(xyz)
206
207 target_link_libraries(xyz
208 PUBLIC MbedTLS::mbedtls
209 MbedTLS::mbedcrypto
210 MbedTLS::mbedx509)
211
212This will link the Mbed TLS libraries to your library or application, and add
213its include directories to your target (transitively, in the case of `PUBLIC` or
214`INTERFACE` link libraries).
215
216#### Mbed TLS as a subproject
217
218Mbed TLS supports being built as a CMake subproject. One can
219use `add_subdirectory()` from a parent CMake project to include Mbed TLS as a
220subproject.
221
222### Microsoft Visual Studio
223
224The build files for Microsoft Visual Studio are generated for Visual Studio 2013.
225
226The solution file `mbedTLS.sln` contains all the basic projects needed to build the library and all the programs. The files in tests are not generated and compiled, as these need Python and perl environments as well. However, the selftest program in `programs/test/` is still available.
227
228In the development branch of Mbed TLS, the Visual Studio solution files need to be generated first as described in [“Generated source files in the development branch”](#generated-source-files-in-the-development-branch).
229
230Example programs
231----------------
232
233We've included example programs for a lot of different features and uses in [`programs/`](programs/README.md).
234Please 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.
235
236Tests
237-----
238
239Mbed TLS includes an elaborate test suite in `tests/` that initially requires Python to generate the tests files (e.g. `test\_suite\_mpi.c`). These files are generated from a `function file` (e.g. `suites/test\_suite\_mpi.function`) and a `data file` (e.g. `suites/test\_suite\_mpi.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.
240
241For machines with a Unix shell and OpenSSL (and optionally GnuTLS) installed, additional test scripts are available:
242
243- `tests/ssl-opt.sh` runs integration tests for various TLS options (renegotiation, resumption, etc.) and tests interoperability of these options with other implementations.
244- `tests/compat.sh` tests interoperability of every ciphersuite with other implementations.
245- `tests/scripts/test-ref-configs.pl` test builds in various reduced configurations.
246- `tests/scripts/depends.py` test builds in configurations with a single curve, key exchange, hash, cipher, or pkalg on.
247- `tests/scripts/all.sh` runs a combination of the above tests, plus some more, with various build options (such as ASan, full `mbedtls_config.h`, etc).
248
249Instead of manually installing the required versions of all tools required for testing, it is possible to use the Docker images from our CI systems, as explained in [our testing infrastructure repository](https://github.com/Mbed-TLS/mbedtls-test/blob/master/README.md#quick-start).
250
251Porting Mbed TLS
252----------------
253
254Mbed TLS can be ported to many different architectures, OS's and platforms. Before starting a port, you may find the following Knowledge Base articles useful:
255
256- [Porting Mbed TLS to a new environment or OS](https://mbed-tls.readthedocs.io/en/latest/kb/how-to/how-do-i-port-mbed-tls-to-a-new-environment-OS/)
257- [What external dependencies does Mbed TLS rely on?](https://mbed-tls.readthedocs.io/en/latest/kb/development/what-external-dependencies-does-mbedtls-rely-on/)
258- [How do I configure Mbed TLS](https://mbed-tls.readthedocs.io/en/latest/kb/compiling-and-building/how-do-i-configure-mbedtls/)
259
260Mbed TLS is mostly written in portable C99; however, it has a few platform requirements that go beyond the standard, but are met by most modern architectures:
261
262- Bytes must be 8 bits.
263- All-bits-zero must be a valid representation of a null pointer.
264- Signed integers must be represented using two's complement.
265- `int` and `size_t` must be at least 32 bits wide.
266- The types `uint8_t`, `uint16_t`, `uint32_t` and their signed equivalents must be available.
267- Mixed-endian platforms are not supported.
268- SIZE_MAX must be at least as big as INT_MAX and UINT_MAX.
269
270PSA cryptography API
271--------------------
272
273### PSA API
274
275Arm's [Platform Security Architecture (PSA)](https://developer.arm.com/architectures/security-architectures/platform-security-architecture) is a holistic set of threat models, security analyses, hardware and firmware architecture specifications, and an open source firmware reference implementation. PSA provides a recipe, based on industry best practice, that allows security to be consistently designed in, at both a hardware and firmware level.
276
277The [PSA cryptography API](https://arm-software.github.io/psa-api/crypto/) provides access to a set of cryptographic primitives. It has a dual purpose. First, it can be used in a PSA-compliant platform to build services, such as secure boot, secure storage and secure communication. Second, it can also be used independently of other PSA components on any platform.
278
279The design goals of the PSA cryptography API include:
280
281* The API distinguishes caller memory from internal memory, which allows the library to be implemented in an isolated space for additional security. Library calls can be implemented as direct function calls if isolation is not desired, and as remote procedure calls if isolation is desired.
282* The structure of internal data is hidden to the application, which allows substituting alternative implementations at build time or run time, for example, in order to take advantage of hardware accelerators.
283* All access to the keys happens through key identifiers, which allows support for external cryptoprocessors that is transparent to applications.
284* The interface to algorithms is generic, favoring algorithm agility.
285* The interface is designed to be easy to use and hard to accidentally misuse.
286
287Arm welcomes feedback on the design of the API. If you think something could be improved, please open an issue on our Github repository. Alternatively, if you prefer to provide your feedback privately, please email us at [`mbed-crypto@arm.com`](mailto:mbed-crypto@arm.com). All feedback received by email is treated confidentially.
288
289### PSA implementation in Mbed TLS
290
291Mbed TLS includes a reference implementation of the PSA Cryptography API.
292However, it does not aim to implement the whole specification; in particular it does not implement all the algorithms.
293
294The X.509 and TLS code can use PSA cryptography for most operations. To enable this support, activate the compilation option `MBEDTLS_USE_PSA_CRYPTO` in `mbedtls_config.h`. Note that TLS 1.3 uses PSA cryptography for most operations regardless of this option. See `docs/use-psa-crypto.md` for details.
295
296### Upcoming features
297
298Future releases of this library will include:
299
300* A driver programming interface, which makes it possible to use hardware accelerators instead of the default software implementation for chosen algorithms.
301* Support for external keys to be stored and manipulated exclusively in a separate cryptoprocessor.
302* A configuration mechanism to compile only the algorithms you need for your application.
303* A wider set of cryptographic algorithms.
304
305License
306-------
307
308Unless specifically indicated otherwise in a file, Mbed TLS files are provided under the [Apache-2.0](https://spdx.org/licenses/Apache-2.0.html) license. See the [LICENSE](LICENSE) file for the full text of this license. Contributors must accept that their contributions are made under both the Apache-2.0 AND [GPL-2.0-or-later](https://spdx.org/licenses/GPL-2.0-or-later.html) licenses. This enables LTS (Long Term Support) branches of the software to be provided under either the Apache-2.0 OR GPL-2.0-or-later licenses.
309
310Contributing
311------------
312
313We gratefully accept bug reports and contributions from the community. Please see the [contributing guidelines](CONTRIBUTING.md) for details on how to do this.
314
315Contact
316-------
317
318* To report a security vulnerability in Mbed TLS, please email <mbed-tls-security@lists.trustedfirmware.org>. For more information, see [`SECURITY.md`](SECURITY.md).
319* To report a bug or request a feature in Mbed TLS, please [file an issue on GitHub](https://github.com/Mbed-TLS/mbedtls/issues/new/choose).
320* Please see [`SUPPORT.md`](SUPPORT.md) for other channels for discussion and support about Mbed TLS.
321