Function pg_GSS_read

src/interfaces/libpq/fe-secure-gssapi.c:271–433

* Read up to len bytes of data into ptr from a GSSAPI-encrypted connection. * * The connection must be already set up for GSSAPI encryption (i.e., GSSAPI * transport negotiation is complete). * * Returns the number of data bytes read, or on failure, returns -1 * with errno set appropriately. If the errno indicates a non-retryable * error, a message is added to conn->errorMessage. For retr

 * caller should call again once the socket is ready.
 */
ssize_t
pg_GSS_read(PGconn *conn, void *ptr, size_t len)
{
	OM_uint32	major,
				minor;
	gss_buffer_desc input = GSS_C_EMPTY_BUFFER,
				output = GSS_C_EMPTY_BUFFER;
	ssize_t		ret;
	size_t		bytes_returned = 0;
	gss_ctx_id_t gctx = conn->gctx;

	/*
	 * The plan here is to read one incoming encrypted packet into
	 * PqGSSRecvBuffer, decrypt it into PqGSSResultBuffer, and then dole out
	 * data from there to the caller.  When we exhaust the current input
	 * packet, read another.
	 */
	while (bytes_returned < len)
	{
		int			conf_state = 0;

		/* Check if we have data in our buffer that we can return immediately */
		if (PqGSSResultNext < PqGSSResultLength)
		{
			size_t		bytes_in_buffer = PqGSSResultLength - PqGSSResultNext;
			size_t		bytes_to_copy = Min(bytes_in_buffer, len - bytes_returned);

			/*
			 * Copy the data from our result buffer into the caller's buffer,
			 * at the point where we last left off filling their buffer.
			 */
			memcpy((char *) ptr + bytes_returned, PqGSSResultBuffer + PqGSSResultNext, bytes_to_copy);
			PqGSSResultNext += bytes_to_copy;
			bytes_returned += bytes_to_copy;

			/*
			 * At this point, we've either filled the caller's buffer or
			 * emptied our result buffer.  Either way, return to caller.  In
			 * the second case, we could try to read another encrypted packet,
			 * but the odds are good that there isn't one available.  (If this
			 * isn't true, we chose too small a max packet size.)  In any
			 * case, there's no harm letting the caller process the data we've
			 * already returned.
			 */
			break;
		}

		/* Result buffer is empty, so reset buffer pointers */
		PqGSSResultLength = PqGSSResultNext = 0;

		/*
		 * Because we chose above to return immediately as soon as we emit
		 * some data, bytes_returned must be zero at this point.  Therefore
		 * the failure exits below can just return -1 without worrying about
		 * whether we already emitted some data.
		 */
		Assert(bytes_returned == 0);