oft.c

Linux下的多协议即时通讯程序源代码

/*
 * Purple's oscar protocol plugin
 * This file is the legal property of its developers.
 * Please see the AUTHORS file distributed alongside this file.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/*
 * I feel like this is a good place to explain OFT, so I'm going to
 * do just that.  Each OFT packet has a header type.  I guess this
 * is pretty similar to the subtype of a SNAC packet.  The type
 * basically tells the other client the meaning of the OFT packet.
 * There are two distinct types of file transfer, which I usually
 * call "sendfile" and "getfile."  Sendfile is when you send a file
 * to another AIM user.  Getfile is when you share a group of files,
 * and other users request that you send them the files.
 *
 * A typical sendfile file transfer goes like this:
 *   1) Sender sends a channel 2 ICBM telling the other user that
 *      we want to send them a file.  At the same time, we open a
 *      listener socket (this should be done before sending the
 *      ICBM) on some port, and wait for them to connect to us.
 *      The ICBM we sent should contain our IP address and the port
 *      number that we're listening on.
 *   2) The receiver connects to the sender on the given IP address
 *      and port.  After the connection is established, the receiver
 *      sends an ICBM signifying that we are ready and waiting.
 *   3) The sender sends an OFT PROMPT message over the OFT
 *      connection.
 *   4) The receiver of the file sends back an exact copy of this
 *      OFT packet, except the cookie is filled in with the cookie
 *      from the ICBM.  I think this might be an attempt to verify
 *      that the user that is connected is actually the guy that
 *      we sent the ICBM to.  Oh, I've been calling this the ACK.
 *   5) The sender starts sending raw data across the connection
 *      until the entire file has been sent.
 *   6) The receiver knows the file is finished because the sender
 *      sent the file size in an earlier OFT packet.  So then the
 *      receiver sends the DONE thingy (after filling in the
 *      "received" checksum and size) and closes the connection.
 */

#include "oscar.h"
#include "peer.h"

#include "util.h"

#define CHECKSUM_BUFFER_SIZE 256 * 1024

struct _ChecksumData
{
	PeerConnection *conn;
	PurpleXfer *xfer;
	GSourceFunc callback;
	size_t size;
	guint32 checksum;
	size_t total;
	FILE *file;
	guint8 buffer[CHECKSUM_BUFFER_SIZE];
	guint timer;
};

void
peer_oft_checksum_destroy(ChecksumData *checksum_data)
{
	checksum_data->conn->checksum_data = NULL;
	fclose(checksum_data->file);
	if (checksum_data->timer > 0)
		purple_timeout_remove(checksum_data->timer);
	g_free(checksum_data);
}

/**
 * Calculate oft checksum of buffer
 *
 * Prevcheck should be 0xFFFF0000 when starting a checksum of a file.  The
 * checksum is kind of a rolling checksum thing, so each time you get bytes
 * of a file you just call this puppy and it updates the checksum.  You can
 * calculate the checksum of an entire file by calling this in a while or a
 * for loop, or something.
 *
 * Thanks to Graham Booker for providing this improved checksum routine,
 * which is simpler and should be more accurate than Josh Myer's original
 * code. -- wtm
 *
 * This algorithm works every time I have tried it.  The other fails
 * sometimes.  So, AOL who thought this up?  It has got to be the weirdest
 * checksum I have ever seen.
 *
 * @param buffer Buffer of data to checksum.  Man I'd like to buff her...
 * @param bufsize Size of buffer.
 * @param prevchecksum Previous checksum.
 * @param odd Whether an odd number of bytes have been processed before this call
 */
static guint32
peer_oft_checksum_chunk(const guint8 *buffer, int bufferlen, guint32 prevchecksum, int odd)
{
	guint32 checksum, oldchecksum;
	int i = 0;
	unsigned short val;

	checksum = (prevchecksum >> 16) & 0xffff;
	if (odd)
	{
		/*
		 * This is one hell of a hack, but it should always work.
		 * Essentially, I am reindexing the array so that index 1
		 * is the first element.  Since the odd and even bytes are
		 * detected by the index number.
		 */
		i = 1;
		bufferlen++;
		buffer--;
	}
	for (; i < bufferlen; i++)
	{
		oldchecksum = checksum;
		if (i & 1)
			val = buffer[i];
		else
			val = buffer[i] << 8;
		checksum -= val;
		/*
		 * The following appears to be necessary.... It happens
		 * every once in a while and the checksum doesn't fail.
		 */
		if (checksum > oldchecksum)
			checksum--;
	}
	checksum = ((checksum & 0x0000ffff) + (checksum >> 16));
	checksum = ((checksum & 0x0000ffff) + (checksum >> 16));
	return checksum << 16;
}

static gboolean
peer_oft_checksum_file_piece(gpointer data)
{
	ChecksumData *checksum_data;
	gboolean repeat;

	checksum_data = data;
	repeat = FALSE;

	if (checksum_data->total < checksum_data->size)
	{
		size_t bytes = MIN(CHECKSUM_BUFFER_SIZE,
				checksum_data->size - checksum_data->total);

		bytes = fread(checksum_data->buffer, 1, bytes, checksum_data->file);
		if (bytes != 0)
		{
			checksum_data->checksum = peer_oft_checksum_chunk(checksum_data->buffer, bytes, checksum_data->checksum, checksum_data->total & 1);
			checksum_data->total += bytes;
			repeat = TRUE;
		}
	}

	if (!repeat)
	{
		purple_debug_info("oscar", "Checksum of %s calculated\n",
				purple_xfer_get_local_filename(checksum_data->xfer));
		if (checksum_data->callback != NULL)
			checksum_data->callback(checksum_data);
		peer_oft_checksum_destroy(checksum_data);
	}

	return repeat;
}

/**
 * Calculate oft checksum of a file in a series of calls to
 * peer_oft_checksum_file_piece().  We do it this way because
 * calculating the checksum on large files can take a long time,
 * and we want to return control to the UI so that the application
 * doesn't appear completely frozen.
 *
 * @param conn The connection used for this file transfer.
 * @param xfer The file transfer needing this checksum.
 * @param callback The function to call upon calculation of the checksum.
 * @param size The maximum size to check.
 */

static void
peer_oft_checksum_file(PeerConnection *conn, PurpleXfer *xfer, GSourceFunc callback, size_t size)
{
	ChecksumData *checksum_data;

	purple_debug_info("oscar", "Calculating checksum of %s\n",
			purple_xfer_get_local_filename(xfer));

	checksum_data = g_malloc0(sizeof(ChecksumData));
	checksum_data->conn = conn;
	checksum_data->xfer = xfer;
	checksum_data->callback = callback;
	checksum_data->size = size;
	checksum_data->checksum = 0xffff0000;
	checksum_data->file = fopen(purple_xfer_get_local_filename(xfer), "rb");

	if (checksum_data->file == NULL)
	{
		purple_debug_error("oscar", "Unable to open %s for checksumming: %s\n",
				purple_xfer_get_local_filename(xfer), strerror(errno));
		callback(checksum_data);
		g_free(checksum_data);
	}
	else
	{
		checksum_data->timer = purple_timeout_add(10,
				peer_oft_checksum_file_piece, checksum_data);
		conn->checksum_data = checksum_data;
	}
}

static void
peer_oft_copy_xfer_data(PeerConnection *conn, OftFrame *frame)
{
	g_free(conn->xferdata.name);

	memcpy(&(conn->xferdata), frame, sizeof(OftFrame));
	conn->xferdata.name = g_memdup(frame->name, frame->name_length);
}

/**
 * Free any OFT related data.
 */
void
peer_oft_close(PeerConnection *conn)
{
	/*
	 * If canceled by local user, and we're receiving a file, and
	 * we're not connected/ready then send an ICBM cancel message.
	 */
	if ((purple_xfer_get_status(conn->xfer) == PURPLE_XFER_STATUS_CANCEL_LOCAL) &&
		!conn->ready)
	{
		aim_im_sendch2_cancel(conn);
	}

	if (conn->sending_data_timer != 0)
	{
		purple_timeout_remove(conn->sending_data_timer);
		conn->sending_data_timer = 0;
	}
}

/**
 * Write the given OftFrame to a ByteStream and send it out
 * on the established PeerConnection.
 */
static void
peer_oft_send(PeerConnection *conn, OftFrame *frame)
{
	size_t length;
	ByteStream bs;

	length = 192 + MAX(64, frame->name_length + 1);
	byte_stream_new(&bs, length);
	byte_stream_putraw(&bs, conn->magic, 4);
	byte_stream_put16(&bs, length);
	byte_stream_put16(&bs, frame->type);
	byte_stream_putraw(&bs, frame->cookie, 8);
	byte_stream_put16(&bs, frame->encrypt);
	byte_stream_put16(&bs, frame->compress);
	byte_stream_put16(&bs, frame->totfiles);
	byte_stream_put16(&bs, frame->filesleft);
	byte_stream_put16(&bs, frame->totparts);
	byte_stream_put16(&bs, frame->partsleft);
	byte_stream_put32(&bs, frame->totsize);
	byte_stream_put32(&bs, frame->size);
	byte_stream_put32(&bs, frame->modtime);
	byte_stream_put32(&bs, frame->checksum);
	byte_stream_put32(&bs, frame->rfrcsum);
	byte_stream_put32(&bs, frame->rfsize);
	byte_stream_put32(&bs, frame->cretime);
	byte_stream_put32(&bs, frame->rfcsum);
	byte_stream_put32(&bs, frame->nrecvd);
	byte_stream_put32(&bs, frame->recvcsum);
	byte_stream_putraw(&bs, frame->idstring, 32);
	byte_stream_put8(&bs, frame->flags);
	byte_stream_put8(&bs, frame->lnameoffset);
	byte_stream_put8(&bs, frame->lsizeoffset);
	byte_stream_putraw(&bs, frame->dummy, 69);
	byte_stream_putraw(&bs, frame->macfileinfo, 16);
	byte_stream_put16(&bs, frame->nencode);
	byte_stream_put16(&bs, frame->nlanguage);
	/*
	 * The name can be more than 64 characters, but if it is less than
	 * 64 characters it is padded with NULLs.
	 */
	byte_stream_putraw(&bs, frame->name, MAX(64, frame->name_length + 1));

	peer_connection_send(conn, &bs);

	g_free(bs.data);
}

void
peer_oft_send_prompt(PeerConnection *conn)
{
	conn->xferdata.type = PEER_TYPE_PROMPT;
	peer_oft_send(conn, &conn->xferdata);
}

static void
peer_oft_send_ack(PeerConnection *conn)
{
	conn->xferdata.type = PEER_TYPE_ACK;

	/* Fill in the cookie */
	memcpy(conn->xferdata.cookie, conn->cookie, 8);

	peer_oft_send(conn, &conn->xferdata);
}

static void
peer_oft_send_resume_accept(PeerConnection *conn)
{
	conn->xferdata.type = PEER_TYPE_RESUMEACCEPT;

	/* Fill in the cookie */
	memcpy(conn->xferdata.cookie, conn->cookie, 8);

	peer_oft_send(conn, &conn->xferdata);
}

static void
peer_oft_send_done(PeerConnection *conn)
{
	conn->xferdata.type = PEER_TYPE_DONE;
	conn->xferdata.filesleft = 0;
	conn->xferdata.partsleft = 0;
	conn->xferdata.nrecvd = purple_xfer_get_bytes_sent(conn->xfer);
	peer_oft_send(conn, &conn->xferdata);
}

/**
 * This function exists so that we don't remove the outgoing
 * data watcher while we're still sending data.  In most cases
 * any data we're sending will be instantly wisked away to a TCP
 * buffer maintained by our operating system... but we want to
 * make sure the core doesn't start sending file data while
 * we're still sending OFT frame data.  That would be bad.
 */
static gboolean
start_transfer_when_done_sending_data(gpointer data)
{
	PeerConnection *conn;

	conn = data;

	if (purple_circ_buffer_get_max_read(conn->buffer_outgoing) == 0)
	{
		conn->sending_data_timer = 0;
		conn->xfer->fd = conn->fd;
		conn->fd = -1;
		purple_xfer_start(conn->xfer, conn->xfer->fd, NULL, 0);
		return FALSE;
	}

	return TRUE;
}

/**
 * This function is similar to the above function, except instead
 * of starting the xfer it will destroy the connection.  This is
 * used when you want to send one final message across the peer
 * connection, and then close everything.
 */
static gboolean
destroy_connection_when_done_sending_data(gpointer data)
{
	PeerConnection *conn;

	conn = data;

	if (purple_circ_buffer_get_max_read(conn->buffer_outgoing) == 0)
	{
		conn->sending_data_timer = 0;
		peer_connection_destroy(conn, conn->disconnect_reason, NULL);
		return FALSE;
	}

	return TRUE;
}

/*
 * This is called when a buddy sends us some file info.  This happens when they
 * are sending a file to you, and you have just established a connection to them.
 * You should send them the exact same info except use the real cookie.  We also
 * get like totally ready to like, receive the file, kay?
 */
static void
peer_oft_recv_frame_prompt(PeerConnection *conn, OftFrame *frame)
{
	/* Record the file information and send an ack */