def export_keying_material(self, label, olen, context=None):
outp = _no_zero_allocator("<STR_LIT>", olen)<EOL>context_buf = _ffi.NULL<EOL>context_len = <NUM_LIT:0><EOL>use_context = <NUM_LIT:0><EOL>if context is not None:<EOL><INDENT>context_buf = context<EOL>context_len = len(context)<EOL>use_context = <NUM_LIT:1><EOL><DEDENT>success = _lib.SSL_export_keying_material(self._ssl, outp, olen,<EOL>label, len(label),<EOL>context_buf, context_len,<EOL>use_context)<EOL>_openssl_assert(success == <NUM_LIT:1>)<EOL>return _ffi.buffer(outp, olen)[:]<EOL>
Obtain keying material for application use.

:param: label - a disambiguating label string as described in RFC 5705
:param: olen - the length of the exported key material in bytes
:param: context - a per-association context value
:return: the exported key material bytes or None