iodine/src/dns.c

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/*
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* Copyright (c) 2006-2007 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
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*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <arpa/inet.h>
#include <arpa/nameser.h>
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#ifdef DARWIN
#include <arpa/nameser8_compat.h>
#endif
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#include <time.h>
#include <err.h>
#include <stdio.h>
#include <stdint.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
#include <ctype.h>
#include "dns.h"
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#include "encoding.h"
#include "read.h"
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int
dns_encode(char *buf, size_t buflen, struct query *q, qr_t qr, char *data, size_t datalen)
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{
HEADER *header;
short name;
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char *p;
int len;
memset(buf, 0, buflen);
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header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = (qr == QR_ANSWER);
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header->opcode = 0;
header->aa = (qr == QR_ANSWER);
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header->tc = 0;
header->rd = (qr == QR_QUERY);
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header->ra = 0;
p = buf + sizeof(HEADER);
switch (qr) {
case QR_ANSWER:
header->ancount = htons(1);
header->qdcount = htons(1);
name = 0xc000 | ((p - buf) & 0x3fff);
putname(&p, sizeof(q->name), q->name);
putshort(&p, q->type);
putshort(&p, C_IN);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0);
putshort(&p, datalen);
putdata(&p, data, datalen);
break;
case QR_QUERY:
header->qdcount = htons(1);
header->arcount = htons(1);
putname(&p, datalen, data);
putshort(&p, q->type);
putshort(&p, C_IN);
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/* EDNS0 */
putbyte(&p, 0x00); /* Root */
putshort(&p, 0x0029); /* OPT */
putshort(&p, 0x1000); /* Payload size: 4096 */
putshort(&p, 0x0000); /* Higher bits/edns version */
putshort(&p, 0x8000); /* Z */
putshort(&p, 0x0000); /* Data length */
break;
}
len = p - buf;
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return len;
}
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int
dns_decode(char *buf, size_t buflen, struct query *q, qr_t qr, char *packet, size_t packetlen)
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{
char name[QUERY_NAME_SIZE];
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char rdata[4*1024];
HEADER *header;
short qdcount;
short ancount;
uint32_t ttl;
short class;
short type;
char *data;
short rlen;
int id;
int rv;
rv = 0;
header = (HEADER*)packet;
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/* Reject short packets */
if (packetlen < sizeof(HEADER))
return 0;
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if (header->qr != qr) {
warnx("header->qr does not match the requested qr");
return -1;
}
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data = packet + sizeof(HEADER);
qdcount = ntohs(header->qdcount);
ancount = ntohs(header->ancount);
id = ntohs(header->id);
rlen = 0;
switch (qr) {
case QR_ANSWER:
if(qdcount != 1 || ancount != 1) {
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switch (header->rcode) {
case REFUSED:
warnx("Got REFUSED as reply");
break;
case NOTIMP:
warnx("Got NOTIMP as reply");
break;
case NXDOMAIN:
warnx("Got NXDOMAIN as reply");
break;
case SERVFAIL:
warnx("Got SERVFAIL as reply");
break;
case NOERROR:
default:
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warnx("no query or answer in reply packet");
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break;
}
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return -1;
}
if (q != NULL)
q->id = id;
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readname(packet, packetlen, &data, name, sizeof(name));
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readname(packet, packetlen, &data, name, sizeof(name));
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readlong(packet, &data, &ttl);
readshort(packet, &data, &rlen);
rv = MIN(rlen, sizeof(rdata));
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rv = readdata(packet, &data, rdata, rv);
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if(type == T_NULL && rv > 2) {
rv = MIN(rv, buflen);
memcpy(buf, rdata, rv);
}
break;
case QR_QUERY:
if (qdcount != 1) {
warnx("no query on query");
return -1;
}
readname(packet, packetlen, &data, name, sizeof(name) - 1);
name[sizeof(name)-1] = '\0';
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readshort(packet, &data, &type);
readshort(packet, &data, &class);
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if(type != T_NULL) {
rv = 0;
break;
}
strncpy(q->name, name, sizeof(q->name));
q->name[sizeof(q->name) - 1] = '\0';
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q->type = type;
q->id = id;
rv = strlen(q->name);
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break;
}
return rv;
}