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pcapng.c
1964 lines (1576 loc) · 73.6 KB
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pcapng.c
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/*******************************************************************************
*
* Copyright (c) 2012-2021 Robert Krause (ruport@f00l.de)
*
* This file is part of Pcapfix.
*
* Pcapfix is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or any later version.
*
* Pcapfix 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with
* Pcapfix. If not, see http://www.gnu.org/licenses/.
*
******************************************************************************/
#include "pcapfix.h"
#include "pcapng.h"
/* Header of all pcapng blocks */
struct block_header {
u_int32_t block_type; /* block type */
u_int32_t total_length; /* block length */
};
/* Header of all pcapng options */
struct option_header {
u_int16_t option_code; /* option code - depending of block (0 - end of opts, 1 - comment are in common) */
u_int16_t option_length; /* option length - length of option in bytes (will be padded to 32bit) */
};
/* Section Header Block (SHB) - ID 0x0A0D0D0A */
struct section_header_block {
u_int32_t byte_order_magic; /* byte order magic - indicates swapped data */
u_int16_t major_version; /* major version of pcapng (1 atm) */
u_int16_t minor_version; /* minor version of pcapng (0 atm) */
int64_t section_length; /* length of section - can be -1 (parsing necessary) */
};
/* Interface Description Block (IDB) - ID 0x00000001 */
struct interface_description_block {
u_int16_t linktype; /* the link layer type (was -network- in classic pcap global header) */
u_int16_t reserved; /* 2 bytes of reserved data */
u_int32_t snaplen; /* maximum number of bytes dumped from each packet (was -snaplen- in classic pcap global header */
};
/* Packet Block (PB) - ID 0x00000002 (OBSOLETE - EPB should be used instead) */
struct packet_block {
u_int16_t interface_id; /* the interface the packet was captured from - identified by interface description block in current section */
u_int16_t drops_count; /* packet dropped by IF and OS since prior packet */
u_int32_t timestamp_high; /* high bytes of timestamp */
u_int32_t timestamp_low; /* low bytes of timestamp */
u_int32_t caplen; /* length of packet in the capture file (was -incl_len- in classic pcap packet header) */
u_int32_t len; /* length of packet when transmitted (was -orig_len- in classic pcap packet header) */
};
/* Simple Packet Block (SPB) - ID 0x00000003 */
struct simple_packet_block {
u_int32_t len; /* length of packet when transmitted (was -orig_len- in classic pcap packet header) */
};
/* Name Resolution Block (NRB) - ID 0x00000004 */
struct name_resolution_block {
u_int16_t record_type; /* type of record (ipv4 / ipv6) */
u_int16_t record_length; /* length of record value */
};
/* Interface Statistics Block - ID 0x00000005 */
struct interface_statistics_block {
u_int32_t interface_id; /* the interface the stats refer to - identified by interface description block in current section */
u_int32_t timestamp_high; /* high bytes of timestamp */
u_int32_t timestamp_low; /* low bytes of timestamp */
};
/* Enhanced Packet Block (EPB) - ID 0x00000006 */
struct enhanced_packet_block {
u_int32_t interface_id; /* the interface the packet was captured from - identified by interface description block in current section */
u_int32_t timestamp_high; /* high bytes of timestamp */
u_int32_t timestamp_low; /* low bytes of timestamp */
u_int32_t caplen; /* length of packet in the capture file (was -incl_len- in classic pcap packet header) */
u_int32_t len; /* length of packet when transmitted (was -orig_len- in classic pcap packet header) */
};
/*
* Function: fix_pcapng
* ---------------------
* tries to fix a pcapng file
*
* pcap: file pointer to input file
* pcap_fix: file pointer to output file
*
* returns: >0 success (number of corruptions fixed)
* 0 success (nothing to fix)
* -1 error (not a pcap file)
* -2 error (unable to repair)
* -3 error (EOF while reading input file)
*
*/
int fix_pcapng(FILE *pcap, FILE *pcap_fix) {
struct block_header bh; /* Block Header */
struct option_header oh; /* Option Header */
struct section_header_block shb; /* Section Header Block */
struct interface_description_block idb; /* Interface Description Block */
struct packet_block pb; /* Packet Block */
struct simple_packet_block spb; /* Simple Packet Block */
struct name_resolution_block nrb; /* Name Resolution Block */
struct interface_statistics_block isb; /* Interface Statistics Block */
struct enhanced_packet_block epb; /* Enhanced Packet Block */
char *data; /* Storage for packet data */
char *new_block; /* Storage for new (maybe repaired) block to finally write into ouput file */
// we use a buffer to cache 1mb of writing... this way writing is faster and
// we can read and write the file at the same time
char *writebuffer;
off_t writepos = 0;
off_t bytes; /* written bytes/blocks counter */
off_t padding; /* calculation for padding bytes */
off_t pos; /* current block position in input file */
off_t filesize; /* size of input file */
unsigned int block_pos; /* current position inside -new_block- to write further data to */
unsigned int check; /* variable to check end of blocks sizes */
unsigned int count; /* option / record counter to create EOO/EOR if necessary */
unsigned int shb_num; /* number of SHB counter */
unsigned int idb_num; /* number of IDB counter */
unsigned int step; /* step counter for progress bar */
unsigned int packets;
off_t left; /* bytes left to proceed until current blocks end is reached */
int fixes; /* corruptions counter */
int res; /* return values */
/* init write buffer */
writebuffer = malloc(1024000);
/* get file size of input file */
fseeko(pcap, 0, SEEK_END);
filesize = ftello(pcap);
fseeko(pcap, 0, SEEK_SET);
/* init variables */
pos = 0; /* begin file check at position 0 */
packets = 0;
fixes = 0; /* no corruptions fixed yet */
shb_num = 0; /* no SHBs progressed yet */
idb_num = 0; /* no IDBs progressed yet */
step = 1; /* progress bar starts at 0 steps */
/* loop every block inside pcapng file until end of file is reached */
while ( pos < (off_t) (filesize-sizeof(bh))) {
/* print out progress bar if in non-verbose mode */
if ((verbose == 0) && (5*(float)pos/(float)filesize > step)) {
print_progress(pos, filesize);
step++;
}
/* read the header of the current block */
bytes = fread(&bh, sizeof(bh), 1, pcap);
if (bytes != 1) return -3;
/* check for invalid block length / file cut off OR block size < 12 bytes */
if (bh.total_length > filesize-pos || bh.total_length < 12) {
/* block size is invalid (too small / larger than bytes in input file) */
if (verbose >= 1) {
if (bh.total_length > filesize-pos) printf("[-] Block Length (%" PRIu16 ") exceeds file size (%" FMT_OFF_T ").\n", bh.total_length, filesize);
else printf("[-] Block Length (%" PRIu16 ") is too small.\n", bh.total_length);
}
/* search for next valid block */
if (verbose >= 1) printf("[*] Trying to align next block...\n");
res = find_valid_block(pcap, filesize);
/* block found? */
if (res == 0) {
/* another valid block has been found in the file */
if (verbose >= 1) printf("[+] GOT Next Block at Position %" FMT_OFF_T "\n", ftello(pcap));
/* adjust total blocks length to match next block */
bh.total_length = ftello(pcap)-pos;
} else {
/* there are no more blocks inside the file */
if (verbose >= 1) printf("[*] No more valid Blocks found inside file! (maybe it was the last one)\n");
/* adjust total blocks length to end of file */
bh.total_length = filesize-pos;
}
if (bh.total_length < 12) {
printf("[-] Block too small ==> SKIPPING\n");
/* reset input file pointer to next block */
fseeko(pcap, pos+bh.total_length, SEEK_SET);
continue;
}
if (verbose >= 1) printf("[*] Assuming this blocks size as %" PRIu32 " bytes.\n", bh.total_length);
else printf("[-] Invalid Block size => CORRECTED.\n");
/* reset input file pointer behind block header */
fseeko(pcap, pos+sizeof(struct block_header), SEEK_SET);
/* increase corruptions counter */
fixes++;
}
/* how many bytes are left until the final block size (end of block) is reached */
left = bh.total_length-sizeof(bh)-sizeof(check);
/* allocate memory for the new block - that will be written to repaired output file finally */
new_block = malloc(bh.total_length);
/* copy the current blocks header into repaired block */
memcpy(new_block, &bh, sizeof(bh));
block_pos = sizeof(bh);
/* what is the type of block at current position ? */
switch (bh.block_type) {
/* Section Header Block */
case TYPE_SHB:
if (verbose >= 1) printf("[*] FOUND: Section Header Block at position %" FMT_OFF_T " (%" PRIu16 " bytes)\n", pos, bh.total_length);
/* read section header block into struct */
bytes = fread(&shb, sizeof(shb), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(shb);
/* check for pcap's magic bytes () */
if (shb.byte_order_magic == BYTE_ORDER_MAGIC) {
if (verbose >= 1) printf("[+] Byte Order Magic: 0x%x\n", shb.byte_order_magic);
} else if (shb.byte_order_magic == htonl(BYTE_ORDER_MAGIC)) {
if (verbose >= 1) printf("[+] Byte Order Magic: 0x%x (SWAPPED)\n", shb.byte_order_magic);
swapped = 1;
} else {
printf("[-] Unknown Byte Order Magic: 0x%x ==> CORRECTED.\n", shb.byte_order_magic);
shb.byte_order_magic = BYTE_ORDER_MAGIC;
fixes++;
}
/* check for major version number (2) */
if (conshort(shb.major_version) == 1) { /* current major version is 2 */
if (verbose >= 1) printf("[+] Major version number: %hu\n", conshort(shb.major_version));
} else {
printf("[-] Major version number: %hu ==> CORRECTED.\n", conshort(shb.major_version));
shb.major_version = conshort(1);
fixes++;
}
/* check for minor version number */
if (conshort(shb.minor_version) == 0) { /* current minor version is 4 */
if (verbose >= 1) printf("[+] Minor version number: %hu\n", conshort(shb.minor_version));
} else {
printf("[-] Minor version number: %hu ==> CORRECTED.\n", conshort(shb.minor_version));
shb.minor_version = conshort(0);
fixes++;
}
/* section length */
if (shb.section_length == -1) {
if (verbose >= 1) printf("[*] Section length: %" PRId64 "\n", shb.section_length);
} else {
if (verbose >= 1) printf("[*] Section length: %" PRId64 " ==> SETTING TO -1\n", shb.section_length);
shb.section_length = -1;
}
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(shb)) {
bh.total_length = block_pos+sizeof(shb);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy section header block into repaired block */
memcpy(new_block+block_pos, &shb, sizeof(shb));
block_pos += sizeof(shb);
/* options */
count = 0 ;
while (left > 0) {
/* read option header into struct */
bytes = fread(&oh, sizeof(oh), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(oh);
/* which option did we get ? */
switch (oh.option_code) {
/* End of Options */
case 0x00:
if (verbose >= 2) printf("[+] OPTION: End of Options... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Comment Option */
case 0x01:
if (verbose >= 2) printf("[+] OPTION: Comment... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Hardware Information */
case 0x02:
if (verbose >= 2) printf("[+] OPTION: Hardware... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Operating System Information */
case 0x03:
if (verbose >= 2) printf("[+] OPTION: Operating System... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* User Application Information */
case 0x04:
if (verbose >= 2) printf("[+] OPTION: Userappl... (%" PRIu16 " bytes)\n", oh.option_length);
break;
}
/* Invalid Option? */
if (oh.option_code > 0x04) {
printf("[-] Unknown option code: 0x%04x (%" PRIu16 " bytes) ==> SKIPPING.\n", oh.option_code, oh.option_length);
/* increase corruptions counter */
fixes++;
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* option is valid */
/* calculate padding for current option value */
padding = oh.option_length;
if (oh.option_length%4 != 0) padding += (4-oh.option_length%4);
/* check oversize */
if (padding > (unsigned)left) {
printf("[-] Option size (%" FMT_OFF_T ") exceeds remaining block space (%" FMT_OFF_T "). ==> SKIPPING OPTION.\n", padding, left);
fixes++;
/* because this block oversizes, there should not be any further option */
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(oh)) {
bh.total_length = block_pos+sizeof(oh);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy option header into repaired block */
memcpy(new_block+block_pos, &oh, sizeof(oh));
block_pos += sizeof(oh);
/* end of options? -> do not write any further */
if (oh.option_code == 0x00 && oh.option_length == 0x00) break;
/* read data of current option */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* write option data to repaired block */
memcpy(new_block+block_pos, data, padding);
block_pos += padding;
/* clean up memory */
free(data);
count++;
}
break;
/* Packet Block */
case TYPE_PB:
packets++;
/* check oversize */
if (sizeof(pb) > (unsigned)left) {
printf("[-] Packet #%u exceeds size of block header (%zu > %" FMT_OFF_T ") ==> SKIPPING.\n", packets, sizeof(pb), left);
/* set to "invalid block" */
bh.block_type = -1;
break;
}
/* check for the mandatory SBH that MUST be before any packet! */
if (shb_num == 0) {
/* no SBH before this packet, we NEED to create one */
printf("[-] No Section Block header found ==> CREATING.\n");
write_shb(pcap_fix, writebuffer, &writepos);
/* increase counters */
shb_num++;
fixes++;
}
if (verbose >= 1) printf("[*] FOUND Packet #%u: Packet Block at position %" FMT_OFF_T " (%" PRIu16 " bytes)\n", packets, pos, bh.total_length);
/* read packet block into struct */
bytes = fread(&pb, sizeof(pb), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(pb);
/* pre-check too large interface number (1024) */
if (pb.interface_id > 1024) {
/* interface id is unusal high --> this field is probably corrupted */
printf("[-] Probably corrupted Interface ID #%" PRIu32 " (too high?) ==> CORRECTED.\n", pb.interface_id);
pb.interface_id = 1;
fixes++;
}
/* check for the mandatory IDB that MUST identify every packets interface_id */
while (pb.interface_id >= idb_num) {
/* no IDB is identifying this packet, we need to create one - until the ID has been reached */
printf("[-] Missing IDB for Interface #%" PRIu32 " ==> CREATING (#%u).\n", pb.interface_id, idb_num);
write_idb(pcap_fix, writebuffer, &writepos);
/* increase counters */
idb_num++;
fixes++;
}
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(pb)) {
bh.total_length = block_pos+sizeof(pb);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy packet block into repaired block */
memcpy(new_block+block_pos, &pb, sizeof(pb));
block_pos += sizeof(pb);
/* check for oversized caplen */
if (pb.caplen > (unsigned)left) {
printf("[-] Capture length (%" PRIu32 ") exceeds block size (%" FMT_OFF_T ") ==> CORRECTED.\n", pb.caplen, left);
pb.caplen = left;
}
/* calculate padding for packet data */
padding = pb.caplen;
if (pb.caplen % 4 != 0) padding += (4 - pb.caplen % 4);
/* read packet data from input file */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy packet data into repaired block */
memcpy(new_block+block_pos, data, padding);
block_pos += padding;
/* clean up memory */
free(data);
/* options */
count = 0;
while (left > 0) {
/* read options header */
bytes = fread(&oh, sizeof(oh), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(oh);
/* which option did we get ? */
switch (oh.option_code) {
/* End of Options */
case 0x00:
if (verbose >= 2) printf("[+] OPTION: End of Options... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Comment Option */
case 0x01:
if (verbose >= 2) printf("[+] OPTION: Comment... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Link Layer Flags */
case 0x02:
if (verbose >= 2) printf("[+] OPTION: Link Layer Flags... (%" PRIu16 " bytes)\n", oh.option_length);
break;
/* Packet Hash */
case 0x03:
if (verbose >= 2) printf("[+] OPTION: Packet Hash... (%" PRIu16 " bytes)\n", oh.option_length);
break;
}
/* Invalid Option? */
if (oh.option_code > 0x03) {
printf("[-] Unknown option code: 0x%04" PRIx16 " (%" PRIu16 " bytes) ==> SKIPPING.\n", oh.option_code, oh.option_length);
/* increase corruptions counter */
fixes++;
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* option is valid */
/* calculate padding for current option value */
padding = oh.option_length;
if (oh.option_length%4 != 0) padding += (4-oh.option_length%4);
/* check oversize */
if (padding > (unsigned)left) {
printf("[-] Option size (%" FMT_OFF_T ") exceeds remaining block space (%" FMT_OFF_T "). ==> SKIPPING OPTION.\n", padding, left);
fixes++;
/* because this block oversizes, there should not be any further option */
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(oh)) {
bh.total_length = block_pos+sizeof(oh);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy options header into repaired block */
memcpy(new_block+block_pos, &oh, sizeof(oh));
block_pos += sizeof(oh);
/* end of options? -> do not write any further */
if (oh.option_code == 0x00 && oh.option_length == 0x00) break;
/* read data of current option */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy option data to repaired block */
memcpy(new_block+block_pos, data, padding);
block_pos += padding;
/* clean up memory */
free(data);
count++;
}
break;
/* Simple Packet Block */
case TYPE_SPB:
packets++;
/* check for the mandatory SBH that MUST be before any packet! */
if (shb_num == 0) {
/* no SBH before this packet, we NEED to create one */
printf("[-] No Section Block header found ==> CREATING.\n");
write_shb(pcap_fix, writebuffer, &writepos);
/* increase counters */
shb_num++;
fixes++;
}
if (verbose >= 1) printf("[*] FOUND Packet #%u: Simple Packet Block at position %" FMT_OFF_T " (%" PRIu16 " bytes)\n", packets, pos, bh.total_length);
/* read simple packet block */
bytes = fread(&spb, sizeof(spb), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(spb);
/* output data */
if (verbose >= 1) printf("[*] SPB original packet length: %u bytes\n", spb.len);
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(spb)) {
bh.total_length = block_pos+sizeof(spb);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy simple packet block into repaired file */
memcpy(new_block+block_pos, &spb, sizeof(spb));
block_pos += sizeof(spb);
/* calculate padding for packet data */
/* spb.len is NOT the length of packet inside file (origlen != caplen); we need to calculate caplen using block length (left) */
/* decrease by two to avoid oversize padding */
padding = left-2;
if (padding % 4 != 0) padding += (4 - left % 4);
/* read packet data from input file */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy packet data into repaired block */
memcpy(new_block+block_pos, data, padding);
block_pos += padding;
/* clean up memory */
free(data);
break;
/* Interface Description Block */
case TYPE_IDB:
/* check for the mandatory SBH that MUST be before any packet! */
if (shb_num == 0) {
/* no SBH before this packet, we NEED to create one */
printf("[-] No Section Block header found ==> CREATING.\n");
write_shb(pcap_fix, writebuffer, &writepos);
/* increase counters */
shb_num++;
fixes++;
}
if (verbose >= 1) printf("[*] FOUND: Interface Description Block (%u bytes)\n", bh.total_length);
/* read interface description block */
bytes = fread(&idb, sizeof(idb), 1, pcap); /* read first bytes of input file into struct */
if (bytes != 1) return -3;
left -= sizeof(idb);
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(idb)) {
bh.total_length = block_pos+sizeof(idb);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy interface description block into repaired block */
memcpy(new_block+block_pos, &idb, sizeof(idb));
block_pos += sizeof(idb);
/* options */
count = 0;
while (left > 0) {
/* read options header */
bytes = fread(&oh, sizeof(oh), 1, pcap);
if (bytes != 1) return -3;
left -= sizeof(oh);
/* which option did we get? */
switch (oh.option_code) {
/* End of Options */
case 0x00:
if (verbose >= 2) printf("[+] OPTION: End of Options... (%u bytes)\n", oh.option_length);
break;
/* Comment Option */
case 0x01:
if (verbose >= 2) printf("[+] OPTION: Comment... (%u bytes)\n", oh.option_length);
break;
/* Interface Name */
case 0x02:
if (verbose >= 2) printf("[+] OPTION: Interface Name... (%u bytes)\n", oh.option_length);
break;
/* Interface Description */
case 0x03:
if (verbose >= 2) printf("[+] OPTION: Interface Description... (%u bytes)\n", oh.option_length);
break;
/* IPv4 Address of Interface */
case 0x04:
if (verbose >= 2) printf("[+] OPTION: IPv4 Address... (%u bytes)\n", oh.option_length);
break;
/* IPv6 Address of Interface */
case 0x05:
if (verbose >= 2) printf("[+] OPTION: IPv6 Address... (%u bytes)\n", oh.option_length);
break;
/* MAC Address of Interface */
case 0x06:
if (verbose >= 2) printf("[+] OPTION: MAC Address... (%u bytes)\n", oh.option_length);
break;
/* EUI Address of Interface */
case 0x07:
if (verbose >= 2) printf("[+] OPTION: EUI Address... (%u bytes)\n", oh.option_length);
break;
/* Interface Speed */
case 0x08:
if (verbose >= 2) printf("[+] OPTION: Interface Speed... (%u bytes)\n", oh.option_length);
break;
/* Resolution of Timestamps */
case 0x09:
if (verbose >= 2) printf("[+] OPTION: Resolution of Timestamps... (%u bytes)\n", oh.option_length);
break;
/* Timezone */
case 0x0a:
if (verbose >= 2) printf("[+] OPTION: Timezone... (%u bytes)\n", oh.option_length);
break;
/* Filter expression used */
case 0x0b:
if (verbose >= 2) printf("[+] OPTION: Filter expression... (%u bytes)\n", oh.option_length);
break;
/* Operating System */
case 0x0c:
if (verbose >= 2) printf("[+] OPTION: Operating System... (%u bytes)\n", oh.option_length);
break;
/* Frame Check Sequence Length */
case 0x0d:
if (verbose >= 2) printf("[+] OPTION: Frame Check Sequence Length... (%u bytes)\n", oh.option_length);
break;
/* Timestamp Offset */
case 0x0e:
if (verbose >= 2) printf("[+] OPTION: Timestamp Offset... (%u bytes)\n", oh.option_length);
break;
}
/* Invalid Option? */
if (oh.option_code > 0x0e) {
printf("[-] Unknown option code: 0x%04x (%u bytes) ==> SKIPPING.\n", oh.option_code, oh.option_length);
/* increase corruptions counter */
fixes++;
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* option is valid */
/* calculate padding for current option value */
padding = oh.option_length;
if (oh.option_length%4 != 0) padding += (4-oh.option_length%4);
/* check oversize */
if (padding > (unsigned)left) {
printf("[-] Option size (%" FMT_OFF_T ") exceeds remaining block space (%" FMT_OFF_T "). ==> SKIPPING OPTION.\n", padding, left);
fixes++;
/* because this block oversizes, there should not be any further option */
/* is this the first option we check? */
if (count == 0) {
/* there are NO options inside this block; skipping EOO option */
if (verbose >= 1) printf("[*] No Options inside -> no need for End of Options...\n");
break;
}
/* there have been other options before this corruption, we need EOO option */
if (verbose >= 1) printf("[*] %u Options inside -> Finishing with End of Options...\n", count);
/* adjust option header to end of options */
oh.option_code = 0x00;
oh.option_length = 0x00;
}
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(oh)) {
bh.total_length = block_pos+sizeof(oh);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy options header into repaired block */
memcpy(new_block+block_pos, &oh, sizeof(oh));
block_pos += sizeof(oh);
/* end of options? -> do not write any further*/
if (oh.option_code == 0x00 && oh.option_length == 0x00) break;
/* read option data */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* write option data into repaired block */
memcpy(new_block+block_pos, data, padding);
block_pos += padding;
/* clean up memory */
free(data);
count++;
}
break;
/* Name Resolution Block */
case TYPE_NRB:
/* check for the mandatory SBH that MUST be before any packet! */
if (shb_num == 0) {
/* no SBH before this packet, we NEED to create one */
printf("[-] No Section Block header found ==> CREATING.\n");
write_shb(pcap_fix, writebuffer, &writepos);
/* increase counters */
shb_num++;
fixes++;
}
if (verbose >= 1) printf("[*] FOUND: Name Resolution Block at position %" FMT_OFF_T " (%" PRIu16 " bytes)\n", pos, bh.total_length);
/* process records */
count = 0;
while (left > 0) {
/* read name resolution block */
bytes = fread(&nrb, sizeof(nrb), 1, pcap); /* read first bytes of input file into struct */
if (bytes != 1) return -3;
left -= sizeof(nrb);
/* which type of record did we get? */
switch (nrb.record_type) {
/* End of Records */
case 0x00:
if (verbose >= 2) printf("[+] RECORD: End of Records... (%u bytes)\n", nrb.record_length);
break;
/* IPv4 Record */
case 0x01:
if (verbose >= 2) printf("[+] RECORD: IPv4 Record... (%u bytes)\n", nrb.record_length);
break;
/* IPv6 Record */
case 0x02:
if (verbose >= 2) printf("[+] RECORD: IPv6 Record... (%u bytes)\n", nrb.record_length);
break;
}
/* Invalid Record? */
if (nrb.record_type > 0x02) {
printf("[-] Unknown record type: 0x%04x (%u bytes) ==> SKIPPING.\n", nrb.record_type, nrb.record_length);
/* increase corruptions counter */
fixes++;
/* is this the first record we check? */
if (count == 0) {
/* there are NO records inside this block; skipping EOR record */
if (verbose >= 1) printf("[*] No Records inside -> no need for End of Records...\n");
break;
}
/* there have been other records before this corruption, we need EOR record */
if (verbose >= 1) printf("[*] %u Records inside -> Finishing with End of Records...\n", count);
/* adjust option header to end of options */
nrb.record_type = 0x00;
nrb.record_length = 0x00;
}
/* record is valid */
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+sizeof(nrb)) {
bh.total_length = block_pos+sizeof(nrb);
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* write name resolution block into repaired block */
memcpy(new_block+block_pos, &nrb, sizeof(nrb));
block_pos += sizeof(nrb);
/* end of records? -> do not write any further */
if (nrb.record_type == 0x00 && nrb.record_length == 0x00) break;
/* calculate padding for current record value */
padding = nrb.record_length;
if (nrb.record_length % 4 != 0) padding += (4 - nrb.record_length % 4);
/* read record value from input file */
data = malloc(padding);
bytes = fread(data, padding, 1, pcap);
left -= padding;
/* check if enough space is aligned in memory block */
if (bh.total_length < block_pos+padding) {
bh.total_length = block_pos+padding;
printf("[-] Given block total length is too small ==> FIXED (%" PRIu32 ")\n", bh.total_length);
new_block = realloc(new_block, bh.total_length);
memcpy(new_block, &bh, sizeof(bh));
fixes++;
}
/* copy record value into repaired buffer */