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
6Configuration
7-------------
8
9Mbed TLS should build out of the box on most systems. Some platform specific options are available in the fully documented configuration file `include/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 Perl script `scripts/config.pl` (use `--help` for usage instructions).
10
11Compiler options can be set using conventional environment variables such as `CC` and `CFLAGS` when using the Make and CMake build system (see below).
12
13Compiling
14---------
15
16There are currently three active build systems used within Mbed TLS releases:
17
18- GNU Make
19- CMake
20- Microsoft Visual Studio (Microsoft Visual Studio 2010 or later)
21
22The 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.
23
24The 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`. Also, when loading shared libraries using dlopen(), you'll need to load libmbedcrypto first, then libmbedx509, before you can load libmbedtls.
25
26### Make
27
28We 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.
29
30We 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.
31
32In order to build from the source code using GNU Make, just enter at the command line:
33
34 make
35
36In order to run the tests, enter:
37
38 make check
39
40The 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:
41
42 make no_test
43
44You'll still be able to run a much smaller set of tests with:
45
46 programs/test/selftest
47
48In 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).
49
50Setting 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.
51
52Please note that setting `CFLAGS` overrides its default value of `-O2` and setting `WARNING_CFLAGS` overrides its default value (starting with `-Wall -W`), 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.
53
54Depending 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://tls.mbed.org/kb) for articles on your platform or issue.
55
56In 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://tls.mbed.org/kb).
57
58### CMake
59
60In order to build the source using CMake in a separate directory (recommended), just enter at the command line:
61
62 mkdir /path/to/build_dir && cd /path/to/build_dir
63 cmake /path/to/mbedtls_source
64 make
65
66In order to run the tests, enter:
67
68 make test
69
70The 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:
71
72 cmake -DENABLE_TESTING=Off /path/to/mbedtls_source
73
74If you disabled the test suites, but kept the programs enabled, you can still run a much smaller set of tests with:
75
76 programs/test/selftest
77
78To configure CMake for building shared libraries, use:
79
80 cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On /path/to/mbedtls_source
81
82There are many different build modes available within the CMake buildsystem. Most of them are available for gcc and clang, though some are compiler-specific:
83
84- `Release`. This generates the default code without any unnecessary information in the binary files.
85- `Debug`. This generates debug information and disables optimization of the code.
86- `Coverage`. This generates code coverage information in addition to debug information.
87- `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.)
88- `ASanDbg`. Same as ASan but slower, with debug information and better stack traces.
89- `MemSan`. This instruments the code with MemorySanitizer to check for uninitialised memory reads. Experimental, needs recent clang on Linux/x86\_64.
90- `MemSanDbg`. Same as MemSan but slower, with debug information, better stack traces and origin tracking.
91- `Check`. This activates the compiler warnings that depend on optimization and treats all warnings as errors.
92
93Switching build modes in CMake is simple. For debug mode, enter at the command line:
94
95 cmake -D CMAKE_BUILD_TYPE=Debug /path/to/mbedtls_source
96
97To list other available CMake options, use:
98
99 cmake -LH
100
101Note that, with CMake, you can't adjust the compiler or its flags after the
102initial invocation of cmake. This means that `CC=your_cc make` and `make
103CC=your_cc` will *not* work (similarly with `CFLAGS` and other variables).
104These variables need to be adjusted when invoking cmake for the first time,
105for example:
106
107 CC=your_cc cmake /path/to/mbedtls_source
108
109If you already invoked cmake and want to change those settings, you need to
110remove the build directory and create it again.
111
112Note that it is possible to build in-place; this will however overwrite the
113provided Makefiles (see `scripts/tmp_ignore_makefiles.sh` if you want to
114prevent `git status` from showing them as modified). In order to do so, from
115the Mbed TLS source directory, use:
116
117 cmake .
118 make
119
120If you want to change `CC` or `CFLAGS` afterwards, you will need to remove the
121CMake cache. This can be done with the following command using GNU find:
122
123 find . -iname '*cmake*' -not -name CMakeLists.txt -exec rm -rf {} +
124
125You can now make the desired change:
126
127 CC=your_cc cmake .
128 make
129
130Regarding variables, also note that if you set CFLAGS when invoking cmake,
131your value of CFLAGS doesn't override the content provided by cmake (depending
132on the build mode as seen above), it's merely prepended to it.
133
134### Microsoft Visual Studio
135
136The build files for Microsoft Visual Studio are generated for Visual Studio 2010.
137
138The 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.
139
140Example programs
141----------------
142
143We've included example programs for a lot of different features and uses in [`programs/`](programs/README.md). Most programs only focus on a single feature or usage scenario, so keep that in mind when copying parts of the code.
144
145Tests
146-----
147
148Mbed 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.
149
150For machines with a Unix shell and OpenSSL (and optionally GnuTLS) installed, additional test scripts are available:
151
152- `tests/ssl-opt.sh` runs integration tests for various TLS options (renegotiation, resumption, etc.) and tests interoperability of these options with other implementations.
153- `tests/compat.sh` tests interoperability of every ciphersuite with other implementations.
154- `tests/scripts/test-ref-configs.pl` test builds in various reduced configurations.
155- `tests/scripts/key-exchanges.pl` test builds in configurations with a single key exchange enabled
156- `tests/scripts/all.sh` runs a combination of the above tests, plus some more, with various build options (such as ASan, full `config.h`, etc).
157
158Configurations
159--------------
160
161We provide some non-standard configurations focused on specific use cases in the `configs/` directory. You can read more about those in `configs/README.txt`
162
163Porting Mbed TLS
164----------------
165
166Mbed 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:
167
168- [Porting Mbed TLS to a new environment or OS](https://tls.mbed.org/kb/how-to/how-do-i-port-mbed-tls-to-a-new-environment-OS)
169- [What external dependencies does Mbed TLS rely on?](https://tls.mbed.org/kb/development/what-external-dependencies-does-mbedtls-rely-on)
170- [How do I configure Mbed TLS](https://tls.mbed.org/kb/compiling-and-building/how-do-i-configure-mbedtls)
171
172License
173-------
174
175Unless specifically indicated otherwise in a file, Mbed TLS files are provided under the [Apache-2.0](https://spdx.org/licenses/Apache-2.0.html) OR [GPL-2.0-or-later](https://spdx.org/licenses/GPL-2.0-or-later.html) licenses. A copy of these licenses can be found in [apache-2.0.txt](./apache-2.0.txt) and [gpl-2.0.txt](./gpl-2.0.txt). Contributors must accept that their contributions are made under both the Apache-2.0 AND GPL-2.0-or-later licenses.
176
177Contributing
178------------
179
180We gratefully accept bug reports and contributions from the community. Please see the [contributing guidelines](CONTRIBUTING.md) for details on how to do this.
181
182Contact
183-------
184
185* To report a security vulnerability in Mbed TLS, please email <mbed-tls-security@lists.trustedfirmware.org>. For more information, see [`SECURITY.md`](SECURITY.md).
186* To report a bug or request a feature in Mbed TLS, please [file an issue on GitHub](https://github.com/ARMmbed/mbedtls/issues/new/choose).
187* Please see [`SUPPORT.md`](SUPPORT.md) for other channels for discussion and support about Mbed TLS.
188