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/* arp_parser.c
*
* This file contains functions to parse ARP and RARP 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"
struct arp_header_s {
uint16_t hwType;
uint16_t pType;
uint8_t hwAddrLen;
uint8_t pAddrLen;
uint16_t opCode;
uint8_t pAddr[];
};
typedef struct arp_header_s arp_header_t;
/*
* This function parses the bytes in the received packet to extract ARP metadata.
*
* its parameters are:
* - a pointer on the list of bytes representing the packet
* the first byte must be the beginning of the ARP 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 ARP 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 *arp_parse(const uchar *packet, int pktSize, struct json_object *jparent) {
DBGPRINTF("arp_parse\n");
DBGPRINTF("packet size %d\n", pktSize);
if (pktSize < 28) { /* too small for ARP header*/
DBGPRINTF("ARP packet too small : %d\n", pktSize);
RETURN_DATA_AFTER(0);
}
/* Union to prevent cast from uchar to arp_header_t */
union {
const uchar *pck;
arp_header_t *hdr;
} arp_header_to_char;
arp_header_to_char.pck = packet;
arp_header_t *arp_header = arp_header_to_char.hdr;
char pAddrSrc[20], pAddrDst[20];
json_object_object_add(jparent, "ARP_hwType", json_object_new_int(ntohs(arp_header->hwType)));
json_object_object_add(jparent, "ARP_pType", json_object_new_int(ntohs(arp_header->pType)));
json_object_object_add(jparent, "ARP_op", json_object_new_int(ntohs(arp_header->opCode)));
if (ntohs(arp_header->hwType) == 1) { /* ethernet addresses */
char hwAddrSrc[20], hwAddrDst[20];
ether_ntoa_r((struct ether_addr *)arp_header->pAddr, hwAddrSrc);
ether_ntoa_r((struct ether_addr *)(arp_header->pAddr + arp_header->hwAddrLen + arp_header->pAddrLen),
hwAddrDst);
json_object_object_add(jparent, "ARP_hwSrc", json_object_new_string((char *)hwAddrSrc));
json_object_object_add(jparent, "ARP_hwDst", json_object_new_string((char *)hwAddrDst));
}
if (ntohs(arp_header->pType) == ETHERTYPE_IP) {
inet_ntop(AF_INET, (void *)(arp_header->pAddr + arp_header->hwAddrLen), pAddrSrc, 20);
inet_ntop(AF_INET, (void *)(arp_header->pAddr + 2 * arp_header->hwAddrLen + arp_header->pAddrLen),
pAddrDst, 20);
json_object_object_add(jparent, "ARP_pSrc", json_object_new_string((char *)pAddrSrc));
json_object_object_add(jparent, "ARP_pDst", json_object_new_string((char *)pAddrDst));
}
RETURN_DATA_AFTER(28);
}
/*
* This function parses the bytes in the received packet to extract RARP metadata.
* This is a copy of ARP handler, as structure is the same but protocol code and name are different
*
* its parameters are:
* - a pointer on the list of bytes representing the packet
* the first byte must be the beginning of the RARP 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 RARP 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 *rarp_parse(const uchar *packet, int pktSize, struct json_object *jparent) {
DBGPRINTF("rarp_parse\n");
DBGPRINTF("packet size %d\n", pktSize);
if (pktSize < 28) { /* too small for RARP header*/
DBGPRINTF("RARP packet too small : %d\n", pktSize);
RETURN_DATA_AFTER(0);
}
/* Union to prevent cast from uchar to arp_header_t */
union {
const uchar *pck;
arp_header_t *hdr;
} arp_header_to_char;
arp_header_to_char.pck = packet;
arp_header_t *rarp_header = arp_header_to_char.hdr;
char pAddrSrc[20], pAddrDst[20];
json_object_object_add(jparent, "RARP_hwType", json_object_new_int(ntohs(rarp_header->hwType)));
json_object_object_add(jparent, "RARP_pType", json_object_new_int(ntohs(rarp_header->pType)));
json_object_object_add(jparent, "RARP_op", json_object_new_int(ntohs(rarp_header->opCode)));
if (ntohs(rarp_header->hwType) == 1) { /* ethernet addresses */
char *hwAddrSrc = ether_ntoa((struct ether_addr *)rarp_header->pAddr);
char *hwAddrDst = ether_ntoa((struct ether_addr *)(rarp_header->pAddr +
rarp_header->hwAddrLen +
rarp_header->pAddrLen));
json_object_object_add(jparent, "RARP_hwSrc", json_object_new_string((char *)hwAddrSrc));
json_object_object_add(jparent, "RARP_hwDst", json_object_new_string((char *)hwAddrDst));
}
if (ntohs(rarp_header->pType) == ETHERTYPE_IP) {
inet_ntop(AF_INET, (void *)(rarp_header->pAddr + rarp_header->hwAddrLen), pAddrSrc, 20);
inet_ntop(AF_INET, (void *)(rarp_header->pAddr + 2 * rarp_header->hwAddrLen + rarp_header->pAddrLen),
pAddrDst, 20);
json_object_object_add(jparent, "RARP_pSrc", json_object_new_string((char *)pAddrSrc));
json_object_object_add(jparent, "RARP_pDst", json_object_new_string((char *)pAddrDst));
}
RETURN_DATA_AFTER(28);
}
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