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/* tcp_parser.c
*
* This file contains functions to parse TCP headers.
*
* File begun on 2018-11-13
*
* Created by:
* - Théo Bertin (theo.bertin@advens.fr)
*
* With:
* - François Bernard (francois.bernard@isen.yncrea.fr)
* - Tianyu Geng (tianyu.geng@isen.yncrea.fr)
*
* This file is part of rsyslog.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
* -or-
* see COPYING.ASL20 in the source distribution
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "config.h"
#include "parsers.h"
#define SMB_PORT 445
#define HTTP_PORT 80
#define HTTP_PORT_ALT 8080
#define FTP_PORT 21
#define FTP_PORT_DATA 20
struct tcp_header_s {
uint16_t srcPort;
uint16_t dstPort;
uint32_t seq;
uint32_t ack;
uint8_t dor;
uint8_t flags;
uint16_t windowSize;
uint16_t checksum;
uint16_t urgPointer;
uint8_t options[];
};
typedef struct tcp_header_s tcp_header_t;
static char flagCodes[10] = "FSRPAUECN";
/*
* This function parses the bytes in the received packet to extract TCP metadata.
*
* its parameters are:
* - a pointer on the list of bytes representing the packet
* the first byte must be the beginning of the TCP header
* - the size of the list passed as first parameter
* - a pointer on a json_object, containing all the metadata recovered so far
* this is also where TCP metadata will be added
*
* This function returns a structure containing the data unprocessed by this parser
* or the ones after (as a list of bytes), and the length of this data.
*/
data_ret_t *tcp_parse(const uchar *packet, int pktSize, struct json_object *jparent) {
DBGPRINTF("tcp_parse\n");
DBGPRINTF("packet size %d\n", pktSize);
if (pktSize < 20) {
DBGPRINTF("TCP packet too small : %d\n", pktSize);
RETURN_DATA_AFTER(0)
}
/* Union to prevent cast from uchar to tcp_header_t */
union {
const uchar *pck;
tcp_header_t *hdr;
} tcp_header_to_char;
tcp_header_to_char.pck = packet;
tcp_header_t *tcp_header = tcp_header_to_char.hdr;
uint8_t i, pos = 0;
char flags[10] = {0};
for (i = 0; i < 8; ++i) {
if (tcp_header->flags & (0x01 << i))
flags[pos++] = flagCodes[i];
}
if (tcp_header->dor & 0x01)
flags[pos++] = flagCodes[9];
uint16_t srcPort = ntohs(tcp_header->srcPort);
uint16_t dstPort = ntohs(tcp_header->dstPort);
uint8_t headerLength = (tcp_header->dor & 0xF0) >> 2; //>>4 to offset but <<2 to get offset as bytes
json_object_object_add(jparent, "net_src_port", json_object_new_int(srcPort));
json_object_object_add(jparent, "net_dst_port", json_object_new_int(dstPort));
json_object_object_add(jparent, "TCP_seq_number", json_object_new_int64(ntohl(tcp_header->seq)));
json_object_object_add(jparent, "TCP_ack_number", json_object_new_int64(ntohl(tcp_header->ack)));
json_object_object_add(jparent, "net_flags", json_object_new_string(flags));
if (srcPort == SMB_PORT || dstPort == SMB_PORT) {
return smb_parse(packet + headerLength, pktSize - headerLength, jparent);
}
if (srcPort == FTP_PORT || dstPort == FTP_PORT || srcPort == FTP_PORT_DATA || dstPort == FTP_PORT_DATA) {
return ftp_parse(packet + headerLength, pktSize - headerLength, jparent);
}
if (srcPort == HTTP_PORT || dstPort == HTTP_PORT ||
srcPort == HTTP_PORT_ALT || dstPort == HTTP_PORT_ALT) {
return http_parse(packet + headerLength, pktSize - headerLength, jparent);
}
DBGPRINTF("tcp return after header length (%u)\n", headerLength);
RETURN_DATA_AFTER(headerLength)
}
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