README.cmake.md: Document minimum required CMake version for --preset

[thirdparty/openvpn.git] / README.mbedtls

This version of OpenVPN has mbed TLS support. To enable, follow the
instructions below:

To build and install,

	./configure --with-crypto-library=mbedtls
	make
	make install

This version requires mbed TLS version >= 2.0.0 or >= 3.2.1.

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Warning:

As of mbed TLS 2.17, it can be licensed *only* under the Apache v2.0 license.
That license is incompatible with OpenVPN's GPLv2.

We are currently in the process of resolving this problem, but for now, if you
wish to distribute OpenVPN linked with mbed TLS, there are two options:

 * Ensure that your case falls under the system library exception in GPLv2, or

 * Use an earlier version of mbed TLS. Version 2.16.12 is the last release
   that may be licensed under GPLv2. Unfortunately, this version is
   unsupported and won't receive any more updates.

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Due to limitations in the mbed TLS library, the following features are missing
in the mbed TLS version of OpenVPN:

 * PKCS#12 file support
 * --capath support - Loading certificate authorities from a directory
 * Windows CryptoAPI support
 * X.509 alternative username fields (must be "CN")

Plugin/Script features:

 * X.509 subject line has a different format than the OpenSSL subject line
 * X.509 certificate tracking

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Mbed TLS 3 has implemented (parts of) the TLS 1.3 protocol, but we have disabled
support in OpenVPN because the TLS-Exporter function is not yet implemented.