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src/ssl/ssl_engine.c  view on Meta::CPAN

	return rc->oxa == rc->oxb && rc->oxa != rc->oxc;
}

/*
 * The "no encryption" mode has no overhead. It limits the payload size
 * to the maximum size allowed by the standard (16384 bytes); the caller
 * is responsible for possibly enforcing a smaller fragment length.
 */
static void
clear_max_plaintext(const br_sslrec_out_clear_context *cc,
	size_t *start, size_t *end)
{
	size_t len;

	(void)cc;
	len = *end - *start;
	if (len > 16384) {
		*end = *start + 16384;
	}
}

/*
 * In "no encryption" mode, encryption is trivial (a no-operation) so
 * we just have to encode the header.
 */
static unsigned char *
clear_encrypt(br_sslrec_out_clear_context *cc,
	int record_type, unsigned version, void *data, size_t *data_len)
{
	unsigned char *buf;

	(void)cc;
	buf = (unsigned char *)data - 5;
	buf[0] = record_type;
	br_enc16be(buf + 1, version);
	br_enc16be(buf + 3, *data_len);
	*data_len += 5;
	return buf;
}

/* see bearssl_ssl.h */
const br_sslrec_out_class br_sslrec_out_clear_vtable = {
	sizeof(br_sslrec_out_clear_context),
	(void (*)(const br_sslrec_out_class *const *, size_t *, size_t *))
		&clear_max_plaintext,
	(unsigned char *(*)(const br_sslrec_out_class **,
		int, unsigned, void *, size_t *))
		&clear_encrypt
};

/* ==================================================================== */
/*
 * In this part of the file, we handle the various record types, and
 * communications with the handshake processor.
 */

/*
 * IMPLEMENTATION NOTES
 * ====================
 *
 * The handshake processor is written in T0 and runs as a coroutine.
 * It receives the contents of all records except application data, and
 * is responsible for producing the contents of all records except
 * application data.
 *
 * A state flag is maintained, which specifies whether application data
 * is acceptable or not. When it is set:
 *
 * -- Application data can be injected as payload data (provided that
 *    the output buffer is ready for that).
 *
 * -- Incoming application data records are accepted, and yield data
 *    that the caller may retrieve.
 *
 * When the flag is cleared, application data is not accepted from the
 * application, and incoming application data records trigger an error.
 *
 *
 * Records of type handshake, alert or change-cipher-spec are handled
 * by the handshake processor. The handshake processor is written in T0
 * and runs as a coroutine; it gets invoked whenever one of the following
 * situations is reached:
 *
 * -- An incoming record has type handshake, alert or change-cipher-spec,
 *    and yields data that can be read (zero-length records are thus
 *    ignored).
 *
 * -- An outgoing record has just finished being sent, and the "application
 *    data" flag is cleared.
 *
 * -- The caller wishes to perform a close (call to br_ssl_engine_close()).
 *
 * -- The caller wishes to perform a renegotiation (call to
 *    br_ssl_engine_renegotiate()).
 *
 * Whenever the handshake processor is entered, access to the payload
 * buffers is provided, along with some information about explicit
 * closures or renegotiations.
 */

/* see bearssl_ssl.h */
void
br_ssl_engine_set_suites(br_ssl_engine_context *cc,
	const uint16_t *suites, size_t suites_num)
{
	if ((suites_num * sizeof *suites) > sizeof cc->suites_buf) {
		br_ssl_engine_fail(cc, BR_ERR_BAD_PARAM);
		return;
	}
	memcpy(cc->suites_buf, suites, suites_num * sizeof *suites);
	cc->suites_num = suites_num;
}

/*
 * Give control to handshake processor. 'action' is 1 for a close,
 * 2 for a renegotiation, or 0 for a jump due to I/O completion.
 */
static void
jump_handshake(br_ssl_engine_context *cc, int action)
{
	/*
	 * We use a loop because the handshake processor actions may
	 * allow for more actions; namely, if the processor reads all
	 * input data, then it may allow for output data to be produced,
	 * in case of a shared in/out buffer.
	 */
	for (;;) {
		size_t hlen_in, hlen_out;

		/*
		 * Get input buffer. We do not want to provide
		 * application data to the handshake processor (we could
		 * get called with an explicit close or renegotiation
		 * while there is application data ready to be read).
		 */
		cc->hbuf_in = recvpld_buf(cc, &hlen_in);
		if (cc->hbuf_in != NULL
			&& cc->record_type_in == BR_SSL_APPLICATION_DATA)
		{
			hlen_in = 0;
		}