OTP 22.1 ssl env protocol_version causes malformed_handshake_data alert

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OTP 22.1 ssl env protocol_version causes malformed_handshake_data alert

Danil Zagoskin-2
Hi!

While upgrading to OTP 22.1 I've hit an issue with ssl.

The problem: when connecting to a TLS server with a client certificate,
  'ssl_handshake:select_hashsign' may fail with '{error,badarg}',
  causing 'Handshake Failure - malformed_handshake_data'

This happens because 'SupportedHashSigns = undefined',
  which comes from 'ssl:handle_options' in 'ssl_connection:init'.

    signature_algs = handle_option(signature_algs, Opts, undefined, Role, undefined, HighestVersion),
    ^^^   this returns 'undefined' because 'tls_v1:default_signature_algs(HighestVersion)' returns 'undefined'

And the problem here was 'HighestVersion = {3,1}' which seemed wrong.

When 'versions' option is not passed, HighestVersion is the head of list returned from 'tls_record:supported_protocol_versions()',
  and that function just maps 'protocol_version' environment parameter.
If the first version specified in environment is low, the 'HighestVersion' will contain not a highest version.

So, after setting default ssl protocol versions like this:
  'application:set_env(ssl, protocol_version, [tlsv1,'tlsv1.1','tlsv1.2']).'
the client raises an alert while handling '#certificate_request{}' from server.



OTP 21 and earlier tolerated the version order in 'protocol_version' env, and the code was like this:
  signature_algs = handle_hashsigns_option(..., tls_version(RecordCb:highest_protocol_version(Versions)))


If the new behaviour is intended, it may be useful to describe it in the man page:
If 'HighestVersion' should always contain a highest version, the obvious
  (but may be not the best) fix is to sort default versions in 'ssl:handle_options',
  like it is done for specified 'versions'.


Obvious workaround for this is to store 'protocol_version' env parameter starting from highest version.


--
Danil Zagoskin | [hidden email]