libssh/README.mbedtls

When built with mbedTLS, libssh currently does not support ECDSA key comparison.
Since the comparison function is used during the verification of publickey
authentication requests a libssh server will not be able to deal with ECDSA
keys.

In general, if the ssh_key_cmp function is used with mbedTLS, ECDSA key
comparison won't work.
add mbedtls crypto support Summary: This patch adds support for mbedTLS as a crypto backend for libssh. mbedTLS is an SSL/TLS library that has been designed to mainly be used in embedded systems. It is loosely coupled and has a low memory footprint. mbedTLS also provides a cryptography library (libmbedcrypto) that can be used without the TLS modules. The patch is unfortunately quite big, since several new files had to be added. DSA is disabled at compile time, since mbedTLS doesn't support DSA Patch review and feedback would be appreciated, and if any issues or suggestions appear, I'm willing to work on them. Signed-off-by: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr> Test Plan: * The patch has been tested with a Debug and MinSizeRel build, with libssh unit tests, client tests and the pkd tests. * All the tests have been run with valgrind's memcheck, drd and helgrind tools. * The examples/samplessh client works when built with the patch. Reviewers: asn, aris Subscribers: simonsj Differential Revision: https://bugs.libssh.org/D1 2017-12-28 13:10:43 +03:00			`When built with mbedTLS, libssh currently does not support ECDSA key comparison.`
			`Since the comparison function is used during the verification of publickey`
			`authentication requests a libssh server will not be able to deal with ECDSA`
			`keys.`

			`In general, if the ssh_key_cmp function is used with mbedTLS, ECDSA key`
			`comparison won't work.`