iodine/src/dns.c

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/*
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* Copyright (c) 2006 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 <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#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 <netdb.h>
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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 <unistd.h>
#include <string.h>
#include <ctype.h>
#include "dns.h"
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#include "encoding.h"
#include "read.h"
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static int decodepacket(const char*, char*, int);
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static char *topdomain;
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/* XXX: only used from server, remove! */
void
dns_set_topdomain(const char *domain)
{
topdomain = strdup(domain);
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}
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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);
p += dns_encode_hostname(q->name, p, strlen(q->name));
putshort(&p, q->type);
putshort(&p, C_IN);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0);
/*
* XXX: This is jidder! This is used to detect if there's packets to be sent.
*/
q->id = 0;
putshort(&p, datalen);
putdata(&p, data, datalen);
break;
case QR_QUERY:
header->qdcount = htons(1);
header->arcount = htons(1);
p += dns_encode_hostname(data, p, datalen);
putshort(&p, q->type);
putshort(&p, C_IN);
// 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 rdata[4*1024];
HEADER *header;
short qdcount;
short ancount;
char name[255];
uint32_t ttl;
short class;
short type;
char *data;
short rlen;
int id;
int rv;
rv = 0;
header = (HEADER*)packet;
// 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) {
warnx("no query or answer in answer");
return -1;
}
if (q != NULL)
q->id = header->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[256] = 0;
readshort(packet, &data, &type);
readshort(packet, &data, &class);
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if(type != T_NULL) {
rv = 0;
break;
}
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strncpy(q->name, name, 257);
q->type = type;
q->id = id;
rv = decodepacket(name, buf, buflen);
break;
}
return rv;
}
int
dns_build_hostname(char *buf, size_t buflen, char *data, size_t datalen, char *topdomain)
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{
int avail;
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int written;
int encoded;
char *b;
avail = MIN(0xFF, buflen) - strlen(topdomain) - 2;
memset(buf, 0, buflen);
b = buf;
written = encode_data(data, datalen, avail, b);
encoded = strlen(buf);
b += encoded;
if (*b != '.') {
*b++ = '.';
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}
strncpy(b, topdomain, strlen(topdomain)+1);
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return written;
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}
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int
dns_encode_hostname(const char *host, char *buffer, int size)
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{
char *h;
char *p;
char *word;
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int left;
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h = strdup(host);
memset(buffer, 0, size);
p = buffer;
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left = size;
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word = strtok(h, ".");
while(word) {
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if (strlen(word) > 63 || strlen(word) > left) {
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free(h);
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return -1;
}
left -= (strlen(word) + 1);
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*p++ = (char)strlen(word);
memcpy(p, word, strlen(word));
p += strlen(word);
word = strtok(NULL, ".");
}
*p++ = 0;
free(h);
return p - buffer;
}
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void
dnsd_send(int fd, struct query *q, char *data, int datalen)
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{
char buf[64*1024];
int len;
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len = dns_encode(buf, sizeof(buf), q, QR_ANSWER, data, datalen);
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sendto(fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen);
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}
static int
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decodepacket(const char *name, char *buf, int buflen)
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{
/*
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int len;
char *domain;
domain = strstr(name, topdomain);
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len = decode_data(buf, buflen, name, domain);
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if (len == buflen)
return -1;
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return len;
*/
return 0;
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}