iodine/src/dns.c
Erik Ekman 9a45c4aa66 Change license wording to follow ISC license exactly
"Permission to use, copy, modify, and distribute this software" is now
"Permission to use, copy, modify, and/or distribute this software".

Add license header to source files missing one.
2014-08-07 21:18:33 +02:00

615 lines
14 KiB
C

/*
* Copyright (c) 2006-2014 Erik Ekman <yarrick@kryo.se>,
* 2006-2009 Bjorn Andersson <flex@kryo.se>
*
* Permission to use, copy, modify, and/or 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 <time.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include <ctype.h>
#ifdef WINDOWS32
#include "windows.h"
#else
#ifdef ANDROID
#include "android_dns.h"
#endif
#include <arpa/nameser.h>
#ifdef DARWIN
#define BIND_8_COMPAT
#include <arpa/nameser_compat.h>
#endif
#include <netinet/in.h>
#include <arpa/inet.h>
#include <err.h>
#endif
#include "dns.h"
#include "encoding.h"
#include "read.h"
int dnsc_use_edns0 = 1;
#define CHECKLEN(x) if (buflen < (x) + (unsigned)(p-buf)) return 0
int
dns_encode(char *buf, size_t buflen, struct query *q, qr_t qr, char *data, size_t datalen)
{
HEADER *header;
short name;
char *p;
int len;
int ancnt;
if (buflen < sizeof(HEADER))
return 0;
memset(buf, 0, buflen);
header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = (qr == QR_ANSWER);
header->opcode = 0;
header->aa = (qr == QR_ANSWER);
header->tc = 0;
header->rd = (qr == QR_QUERY);
header->ra = 0;
p = buf + sizeof(HEADER);
switch (qr) {
case QR_ANSWER:
header->qdcount = htons(1);
name = 0xc000 | ((p - buf) & 0x3fff);
/* Question section */
putname(&p, buflen - (p - buf), q->name);
CHECKLEN(4);
putshort(&p, q->type);
putshort(&p, C_IN);
/* Answer section */
if (q->type == T_CNAME || q->type == T_A) {
/* data is expected to be like "Hblabla.host.name.com\0" */
char *startp;
int namelen;
CHECKLEN(10);
putshort(&p, name);
if (q->type == T_A)
/* answer CNAME to A question */
putshort(&p, T_CNAME);
else
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0); /* TTL */
startp = p;
p += 2; /* skip 2 bytes length */
putname(&p, buflen - (p - buf), data);
CHECKLEN(0);
namelen = p - startp;
namelen -= 2;
putshort(&startp, namelen);
ancnt = 1;
} else if (q->type == T_MX || q->type == T_SRV) {
/* Data is expected to be like
"Hblabla.host.name.com\0Hanother.com\0\0"
For SRV, see RFC2782.
*/
char *mxdata = data;
char *startp;
int namelen;
ancnt = 1;
while (1) {
CHECKLEN(10);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0); /* TTL */
startp = p;
p += 2; /* skip 2 bytes length */
CHECKLEN(2);
putshort(&p, 10 * ancnt); /* preference */
if (q->type == T_SRV) {
/* weight, port (5060 = SIP) */
CHECKLEN(4);
putshort(&p, 10);
putshort(&p, 5060);
}
putname(&p, buflen - (p - buf), mxdata);
CHECKLEN(0);
namelen = p - startp;
namelen -= 2;
putshort(&startp, namelen);
mxdata = mxdata + strlen(mxdata) + 1;
if (*mxdata == '\0')
break;
ancnt++;
}
} else if (q->type == T_TXT) {
/* TXT has binary or base-X data */
char *startp;
int txtlen;
CHECKLEN(10);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0); /* TTL */
startp = p;
p += 2; /* skip 2 bytes length */
puttxtbin(&p, buflen - (p - buf), data, datalen);
CHECKLEN(0);
txtlen = p - startp;
txtlen -= 2;
putshort(&startp, txtlen);
ancnt = 1;
} else {
/* NULL has raw binary data */
CHECKLEN(10);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0); /* TTL */
datalen = MIN(datalen, buflen - (p - buf));
CHECKLEN(2);
putshort(&p, datalen);
CHECKLEN(datalen);
putdata(&p, data, datalen);
CHECKLEN(0);
ancnt = 1;
}
header->ancount = htons(ancnt);
break;
case QR_QUERY:
/* Note that iodined also uses this for forward queries */
header->qdcount = htons(1);
datalen = MIN(datalen, buflen - (p - buf));
putname(&p, datalen, data);
CHECKLEN(4);
putshort(&p, q->type);
putshort(&p, C_IN);
/* EDNS0 to advertise maximum response length
(even CNAME/A/MX, 255+255+header would be >512) */
if (dnsc_use_edns0) {
header->arcount = htons(1);
CHECKLEN(11);
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;
return len;
}
int
dns_encode_ns_response(char *buf, size_t buflen, struct query *q, char *topdomain)
/* Only used when iodined gets an NS type query */
/* Mostly same as dns_encode_a_response() below */
{
HEADER *header;
int len;
short name;
short topname;
short nsname;
char *ipp;
int domain_len;
char *p;
if (buflen < sizeof(HEADER))
return 0;
memset(buf, 0, buflen);
header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = 1;
header->opcode = 0;
header->aa = 1;
header->tc = 0;
header->rd = 0;
header->ra = 0;
p = buf + sizeof(HEADER);
header->qdcount = htons(1);
header->ancount = htons(1);
header->arcount = htons(1);
/* pointer to start of name */
name = 0xc000 | ((p - buf) & 0x3fff);
domain_len = strlen(q->name) - strlen(topdomain);
if (domain_len < 0 || domain_len == 1)
return -1;
if (strcasecmp(q->name + domain_len, topdomain))
return -1;
if (domain_len >= 1 && q->name[domain_len - 1] != '.')
return -1;
/* pointer to start of topdomain; instead of dots at the end
we have length-bytes in front, so total length is the same */
topname = 0xc000 | ((p - buf + domain_len) & 0x3fff);
/* Query section */
putname(&p, buflen - (p - buf), q->name); /* Name */
CHECKLEN(4);
putshort(&p, q->type); /* Type */
putshort(&p, C_IN); /* Class */
/* Answer section */
CHECKLEN(12);
putshort(&p, name); /* Name */
putshort(&p, q->type); /* Type */
putshort(&p, C_IN); /* Class */
putlong(&p, 3600); /* TTL */
putshort(&p, 5); /* Data length */
/* pointer to ns.topdomain */
nsname = 0xc000 | ((p - buf) & 0x3fff);
CHECKLEN(5);
putbyte(&p, 2);
putbyte(&p, 'n');
putbyte(&p, 's');
putshort(&p, topname); /* Name Server */
/* Additional data (A-record of NS server) */
CHECKLEN(12);
putshort(&p, nsname); /* Name Server */
putshort(&p, T_A); /* Type */
putshort(&p, C_IN); /* Class */
putlong(&p, 3600); /* TTL */
putshort(&p, 4); /* Data length */
/* ugly hack to output IP address */
ipp = (char *) &q->destination;
CHECKLEN(4);
putbyte(&p, *(ipp++));
putbyte(&p, *(ipp++));
putbyte(&p, *(ipp++));
putbyte(&p, *ipp);
len = p - buf;
return len;
}
int
dns_encode_a_response(char *buf, size_t buflen, struct query *q)
/* Only used when iodined gets an A type query for ns.topdomain or www.topdomain */
/* Mostly same as dns_encode_ns_response() above */
{
HEADER *header;
int len;
short name;
char *ipp;
char *p;
if (buflen < sizeof(HEADER))
return 0;
memset(buf, 0, buflen);
header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = 1;
header->opcode = 0;
header->aa = 1;
header->tc = 0;
header->rd = 0;
header->ra = 0;
p = buf + sizeof(HEADER);
header->qdcount = htons(1);
header->ancount = htons(1);
/* pointer to start of name */
name = 0xc000 | ((p - buf) & 0x3fff);
/* Query section */
putname(&p, buflen - (p - buf), q->name); /* Name */
CHECKLEN(4);
putshort(&p, q->type); /* Type */
putshort(&p, C_IN); /* Class */
/* Answer section */
CHECKLEN(12);
putshort(&p, name); /* Name */
putshort(&p, q->type); /* Type */
putshort(&p, C_IN); /* Class */
putlong(&p, 3600); /* TTL */
putshort(&p, 4); /* Data length */
/* ugly hack to output IP address */
ipp = (char *) &q->destination;
CHECKLEN(4);
putbyte(&p, *(ipp++));
putbyte(&p, *(ipp++));
putbyte(&p, *(ipp++));
putbyte(&p, *ipp);
len = p - buf;
return len;
}
#undef CHECKLEN
unsigned short
dns_get_id(char *packet, size_t packetlen)
{
HEADER *header;
header = (HEADER*)packet;
if (packetlen < sizeof(HEADER))
return 0;
return ntohs(header->id);
}
#define CHECKLEN(x) if (packetlen < (x) + (unsigned)(data-packet)) return 0
int
dns_decode(char *buf, size_t buflen, struct query *q, qr_t qr, char *packet, size_t packetlen)
{
char name[QUERY_NAME_SIZE];
char rdata[4*1024];
HEADER *header;
short qdcount;
short ancount;
uint32_t ttl;
unsigned short class;
unsigned short type;
char *data;
unsigned short rlen;
int id;
int rv;
q->id2 = 0;
rv = 0;
header = (HEADER*)packet;
/* Reject short packets */
if (packetlen < sizeof(HEADER))
return 0;
if (header->qr != qr) {
warnx("header->qr does not match the requested qr");
return -1;
}
data = packet + sizeof(HEADER);
qdcount = ntohs(header->qdcount);
ancount = ntohs(header->ancount);
id = ntohs(header->id);
id = id & 0xFFFF; /* Kill any sign extension */
rlen = 0;
if (q != NULL)
q->rcode = header->rcode;
switch (qr) {
case QR_ANSWER:
if(qdcount < 1) {
/* We need a question */
return -1;
}
if (q != NULL)
q->id = id;
/* Read name even if no answer, to give better error message */
readname(packet, packetlen, &data, name, sizeof(name));
CHECKLEN(4);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
/* if CHECKLEN okay, then we're sure to have a proper name */
if (q != NULL) {
/* We only need the first char to check it */
q->name[0] = name[0];
q->name[1] = '\0';
}
if (ancount < 1) {
/* DNS errors like NXDOMAIN have ancount=0 and
stop here. CNAME may also have A; MX/SRV may have
multiple results. */
return -1;
}
/* Here type is still the question type */
if (type == T_NULL || type == T_PRIVATE) {
/* Assume that first answer is what we wanted */
readname(packet, packetlen, &data, name, sizeof(name));
CHECKLEN(10);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readlong(packet, &data, &ttl);
readshort(packet, &data, &rlen);
rv = MIN(rlen, sizeof(rdata));
rv = readdata(packet, &data, rdata, rv);
if (rv >= 2 && buf) {
rv = MIN(rv, buflen);
memcpy(buf, rdata, rv);
} else {
rv = 0;
}
}
else if ((type == T_A || type == T_CNAME) && buf) {
/* Assume that first answer is what we wanted */
readname(packet, packetlen, &data, name, sizeof(name));
CHECKLEN(10);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readlong(packet, &data, &ttl);
readshort(packet, &data, &rlen);
memset(name, 0, sizeof(name));
readname(packet, packetlen, &data, name, sizeof(name) - 1);
name[sizeof(name)-1] = '\0';
strncpy(buf, name, buflen);
buf[buflen - 1] = '\0';
rv = strlen(buf);
}
else if ((type == T_MX || type == T_SRV) && buf) {
/* We support 250 records, 250*(255+header) ~= 64kB.
Only exact 10-multiples are accepted, and gaps in
numbering are not jumped over (->truncated).
Hopefully DNS servers won't mess around too much.
*/
char names[250][QUERY_NAME_SIZE];
char *rdatastart;
unsigned short pref;
int i;
int offset;
memset(names, 0, sizeof(names));
for (i=0; i < ancount; i++) {
readname(packet, packetlen, &data, name, sizeof(name));
CHECKLEN(12);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readlong(packet, &data, &ttl);
readshort(packet, &data, &rlen);
rdatastart = data;
readshort(packet, &data, &pref);
if (type == T_SRV) {
/* skip weight, port */
data += 4;
CHECKLEN(0);
}
if (pref % 10 == 0 && pref >= 10 &&
pref < 2500) {
readname(packet, packetlen, &data,
names[pref / 10 - 1],
QUERY_NAME_SIZE - 1);
names[pref / 10 - 1][QUERY_NAME_SIZE-1] = '\0';
}
/* always trust rlen, not name encoding */
data = rdatastart + rlen;
CHECKLEN(0);
}
/* output is like Hname10.com\0Hname20.com\0\0 */
offset = 0;
i = 0;
while (names[i][0] != '\0') {
int l = MIN(strlen(names[i]), buflen-offset-2);
if (l <= 0)
break;
memcpy(buf + offset, names[i], l);
offset += l;
*(buf + offset) = '\0';
offset++;
i++;
}
*(buf + offset) = '\0';
rv = offset;
}
else if (type == T_TXT && buf) {
/* Assume that first answer is what we wanted */
readname(packet, packetlen, &data, name, sizeof(name));
CHECKLEN(10);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
readlong(packet, &data, &ttl);
readshort(packet, &data, &rlen);
rv = readtxtbin(packet, &data, rlen, rdata, sizeof(rdata));
if (rv >= 1) {
rv = MIN(rv, buflen);
memcpy(buf, rdata, rv);
} else {
rv = 0;
}
}
/* Here type is the answer type (note A->CNAME) */
if (q != NULL)
q->type = type;
break;
case QR_QUERY:
if (qdcount < 1) {
warnx("no question section in name query");
return -1;
}
memset(name, 0, sizeof(name));
readname(packet, packetlen, &data, name, sizeof(name) - 1);
name[sizeof(name)-1] = '\0';
CHECKLEN(4);
readshort(packet, &data, &type);
readshort(packet, &data, &class);
if (q == NULL) {
rv = 0;
break;
}
strncpy(q->name, name, sizeof(q->name));
q->name[sizeof(q->name) - 1] = '\0';
q->type = type;
q->id = id;
rv = strlen(q->name);
break;
}
return rv;
}