Alright, so for some weird reason, there is no DNS header in Linux.
that’s why I decided to write one:
/*
DNS Header for packet forging
Copyright (C) 2016 unh0lys0da
This program 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
(at your option) any later version.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define DNS_OPCODE_QUERY 0
#define DNS_OPCODE_IQUERY 1
#define DNS_OPCODE_STATUS 2
#define DNS_OPCODE_NOTIFY 4
#define DNS_OPCODE_UPGRADE 5
#define DNS_RCODE_NOERROR 0
#define DNS_RCODE_FORMERR 1
#define DNS_RCODE_SERVFAIL 2
#define DNS_RCODE_NXDOMAIN 3
#define DNS_RCODE_NOTIMP 4
#define DNS_RCODE_REFUSED 5
#define DNS_RCODE_YXDOMAIN 6
#define DNS_RCODE_YXRRSET 7
#define DNS_RCODE_NXRRSET 8
#define DNS_RCODE_NOTAUTH 9
#define DNS_RCODE_NOTZONE 10
#define DNS_RCODE_BADVERS 16
#define DNS_RCODE_BADSIG 16
#define DNS_RCODE_BADKEY 17
#define DNS_RCODE_BADTIME 18
#define DNS_RCODE_BADMODE 19
#define DNS_RCODE_BADNAME 20
#define DNS_RCODE_BADALG 21
#define DNS_RCODE_BADTRUNC 22
#define DNS_RCODE_BADCOOKIE 23
#include <endian.h>
#include <stdint.h>
#include <strings.h>
typedef struct {
uint16_t id;
# if __BYTE_ORDER == __BIG_ENDIAN
uint16_t qr:1;
uint16_t opcode:4;
uint16_t aa:1;
uint16_t tc:1;
uint16_t rd:1;
uint16_t ra:1;
uint16_t zero:3;
uint16_t rcode:4;
# elif __BYTE_ORDER == __LITTLE_ENDIAN
uint16_t rd:1;
uint16_t tc:1;
uint16_t aa:1;
uint16_t opcode:4;
uint16_t qr:1;
uint16_t rcode:4;
uint16_t zero:3;
uint16_t ra:1;
# else
# error "Adjust your <bits/endian.h> defines"
# endif
uint16_t qcount; /* question count */
uint16_t ancount; /* Answer record count */
uint16_t nscount; /* Name Server (Autority Record) Count */
uint16_t adcount; /* Additional Record Count */
} dnshdr;
/* DNS QTYPES */
#define DNS_QTYPE_A 1
#define DNS_QTYPE_NS 2
#define DNS_QTYPE_CNAME 5
#define DNS_QTYPE_SOA 6
#define DNS_QTYPE_PTR 12
#define DNS_QTYPE_MX 15
#define DNS_QTYPE_TXT 16
#define DNS_QTYPE_RP 17
#define DNS_QTYPE_AFSDB 18
#define DNS_QTYPE_SIG 24
#define DNS_QTYPE_KEY 25
#define DNS_QTYPE_AAAA 28
#define DNS_QTYPE_LOC 29
#define DNS_QTYPE_SRV 33
#define DNS_QTYPE_NAPTR 35
#define DNS_QTYPE_KX 36
#define DNS_QTYPE_CERT 37
#define DNS_QTYPE_DNAME 39
#define DNS_QTYPE_OPT 41
#define DNS_QTYPE_APL 42
#define DNS_QTYPE_DS 43
#define DNS_QTYPE_SSHFP 44
#define DNS_QTYPE_IPSECKEY 45
#define DNS_QTYPE_RRSIG 46
#define DNS_QTYPE_NSEC 47
#define DNS_QTYPE_DNSKEY 48
#define DNS_QTYPE_DHCID 49
#define DNS_QTYPE_NSEC3 50
#define DNS_QTYPE_NSEC3PARAM 51
#define DNS_QTYPE_TLSA 52
#define DNS_QTYPE_HIP 55
#define DNS_QTYPE_CDS 59
#define DNS_QTYPE_CDNSKEY 60
#define DNS_QTYPE_TKEY 249
#define DNS_QTYPE_TSIG 250
#define DNS_QTYPE_IXFR 251
#define DNS_QTYPE_AXFR 252
#define DNS_QTYPE_ALL 255 /* AKA: * QTYPE */
#define DNS_QTYPE_URI 256
#define DNS_QTYPE_CAA 257
#define DNS_QTYPE_TA 32768
#define DNS_QTYPE_DLV 32769
/* DNS QCLASS */
#define DNS_QCLASS_RESERVED 0
#define DNS_QCLASS_IN 1
#define DNS_QCLASS_CH 3
#define DNS_QCLASS_HS 4
#define DNS_QCLASS_NONE 254
#define DNS_QCLASS_ANY 255
/*
Function to change url to dns format
For example: www.google.com would become:
3www6google3com0
size, can be used if you want to know the size of the returned pointer,
because strlen reads until nullbyte and therefore doesnt include qtype and qclass.
*/
unsigned char* dns_format ( char *url, int *size, unsigned short int qtype, unsigned short int qclass )
{
int i, c = 0, len = strlen(url);
char *buf = (char *) malloc(len+6);
buf[len+1] = 0;
for(i=len;i>=0;i--){
if(url[i] == '.') {
buf[i+1] = c;
c = 0;
}
else {
buf[i+1] = url[i];
c++;
}
}
buf[0] = c;
uint16_t* qt = buf+len+2;
*qt = qtype;
uint16_t* qc = buf+len+4;
*qc = qclass;
if(size) *size = len+6;
return buf;
}
It doesn’t yet cover the full DNS protocol, but it’s enough to write a DNS Amplification attack tool for example. (I’ll write one soon).
To use this header, save it as dns.h.
Then move it to the folder of your C program.
In the C program include it by putting #include "dns.h" on top of your program.
Tell me what you think ^^