escript demonstrating bad negotiation in OTP SSL server

badhello.escript

#!/usr/bin/env escript
% This escript sends malformed SSLv3 client_hello to specified server
% and prints negotiated version and cipher suite
%
% Usage example:    ./badhello.escript localhost 9998

-module(badhello).
-include_lib("ssl/src/ssl_handshake.hrl").

client_hello() ->
  <<22, 3,0, 49:16,   % handshake, SSL 3.0, length
    1, 45:24,         % client_hello, length
    3,0,              % SSL 3.0
    16#deadbeef:256,  % 32 'random' bytes = 256 bits
    0,                % no session ID
    6:16, 0,255, 0,61, 0,57,
                      % three cipher suites -- null, one with sha256 hash and one with sha hash
    1, 0              % no compression
  >>.


main([Host, PortStr]) ->
  run(Host, list_to_integer(PortStr)).

run(Host, Port) ->
  {ok, S} = gen_tcp:connect(Host, Port, [binary, {active, false}]),
  ok = gen_tcp:send(S, client_hello()),
  {ok, <<22, RecMajor:8, RecMinor:8, _RecLen:16, 2, HelloLen:24>>} = gen_tcp:recv(S, 9, 10000),
  {ok, <<HelloBin:HelloLen/binary>>} = gen_tcp:recv(S, HelloLen, 5000),
  #server_hello{} = ServerHello = tls_handshake:decode_handshake({RecMajor, RecMinor}, 2, HelloBin),
  #server_hello{
    server_version = ServerVer,
    cipher_suite = CipherSuite } = ServerHello,
  io:format("Received server_hello of version ~w with cipher suite ~w~n", [ServerVer, ssl:suite_definition(CipherSuite)]).