mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-24 12:23:32 +01:00
85 lines
2.7 KiB
C
85 lines
2.7 KiB
C
/* Copyright (c) 2001 Matej Pfajfar.
|
|
* Copyright (c) 2001-2004, Roger Dingledine.
|
|
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
|
|
* Copyright (c) 2007-2017, The Tor Project, Inc. */
|
|
/* See LICENSE for licensing information */
|
|
|
|
#include "or.h"
|
|
#include "buffers.h"
|
|
#include "proto_cell.h"
|
|
|
|
#include "connection_or.h"
|
|
|
|
/** True iff the cell command <b>command</b> is one that implies a
|
|
* variable-length cell in Tor link protocol <b>linkproto</b>. */
|
|
static inline int
|
|
cell_command_is_var_length(uint8_t command, int linkproto)
|
|
{
|
|
/* If linkproto is v2 (2), CELL_VERSIONS is the only variable-length cells
|
|
* work as implemented here. If it's 1, there are no variable-length cells.
|
|
* Tor does not support other versions right now, and so can't negotiate
|
|
* them.
|
|
*/
|
|
switch (linkproto) {
|
|
case 1:
|
|
/* Link protocol version 1 has no variable-length cells. */
|
|
return 0;
|
|
case 2:
|
|
/* In link protocol version 2, VERSIONS is the only variable-length cell */
|
|
return command == CELL_VERSIONS;
|
|
case 0:
|
|
case 3:
|
|
default:
|
|
/* In link protocol version 3 and later, and in version "unknown",
|
|
* commands 128 and higher indicate variable-length. VERSIONS is
|
|
* grandfathered in. */
|
|
return command == CELL_VERSIONS || command >= 128;
|
|
}
|
|
}
|
|
|
|
/** Check <b>buf</b> for a variable-length cell according to the rules of link
|
|
* protocol version <b>linkproto</b>. If one is found, pull it off the buffer
|
|
* and assign a newly allocated var_cell_t to *<b>out</b>, and return 1.
|
|
* Return 0 if whatever is on the start of buf_t is not a variable-length
|
|
* cell. Return 1 and set *<b>out</b> to NULL if there seems to be the start
|
|
* of a variable-length cell on <b>buf</b>, but the whole thing isn't there
|
|
* yet. */
|
|
int
|
|
fetch_var_cell_from_buf(buf_t *buf, var_cell_t **out, int linkproto)
|
|
{
|
|
char hdr[VAR_CELL_MAX_HEADER_SIZE];
|
|
var_cell_t *result;
|
|
uint8_t command;
|
|
uint16_t length;
|
|
const int wide_circ_ids = linkproto >= MIN_LINK_PROTO_FOR_WIDE_CIRC_IDS;
|
|
const int circ_id_len = get_circ_id_size(wide_circ_ids);
|
|
const unsigned header_len = get_var_cell_header_size(wide_circ_ids);
|
|
*out = NULL;
|
|
if (buf_datalen(buf) < header_len)
|
|
return 0;
|
|
buf_peek(buf, hdr, header_len);
|
|
|
|
command = get_uint8(hdr + circ_id_len);
|
|
if (!(cell_command_is_var_length(command, linkproto)))
|
|
return 0;
|
|
|
|
length = ntohs(get_uint16(hdr + circ_id_len + 1));
|
|
if (buf_datalen(buf) < (size_t)(header_len+length))
|
|
return 1;
|
|
|
|
result = var_cell_new(length);
|
|
result->command = command;
|
|
if (wide_circ_ids)
|
|
result->circ_id = ntohl(get_uint32(hdr));
|
|
else
|
|
result->circ_id = ntohs(get_uint16(hdr));
|
|
|
|
buf_drain(buf, header_len);
|
|
buf_peek(buf, (char*) result->payload, length);
|
|
buf_drain(buf, length);
|
|
|
|
*out = result;
|
|
return 1;
|
|
}
|
|
|