unsigned
dns_resolve_alias(struct NetFrame *frame, const unsigned char *px, unsigned length, struct DNS *dns, const char *alias, int depth)
{
unsigned i;
for (i=dns->question_count; i<dns->record_count; i++) {
struct DNSRECORD *rec = &dns->records[i];
char name[256];
unsigned name_length;
name_length = dns_extract_name(frame, px, length, rec->name_offset, name, sizeof(name));
if ((rec->type != 1 && rec->type != 5)|| (rec->clss&0x7FFF) != 1)
continue;
if (stricmp(alias, name) == 0) {
switch (rec->type) {
case 1:
return ex32be(px+rec->rdata_offset);
case 5:
name_length = dns_extract_name(frame, px, length, rec->rdata_offset, name, sizeof(name));
if (depth > 10)
FRAMERR(frame, "dns: too much recursion, alias=\"%s\"\n", alias);
else
return dns_resolve_alias(frame, px, length, dns, name, depth+1);
}
}
}
/*FRAMERR(frame, "dns: could not resolve IP for alias=\"%s\"\n", alias);*/
return 0;
}
/****************************************************************************
* Expands the packet's SOA record to a full uncompressed SOA record so
* that we can compare it with the origin SOA that we parsed.
*
* @param buf
* The target buffer that will hold the expanded SOA record.
* @param buf_offset
* The current offset into this buffer. We'll move this index
* forward as we append to the buffer
* @param buf_size
* The size of the buffer, to prevent buffer overruns.
* @param soa
* The compressed SOA record from the packet.
* @param soa_length
* The RDLENGTH (compressed length) of the packet SOA record.
* @param hdr
* The beginning of the packet header, which we need when decompressing
* names (because DNS name compression is done as offsets from the
* start of the packet).
****************************************************************************/
int expand_soa(
unsigned char *buf, unsigned *buf_offset, size_t buf_size,
const unsigned char *soa, unsigned soa_length,
const unsigned char *hdr)
{
struct DomainPointer d;
unsigned soa_offset = (unsigned)(soa-hdr);
unsigned soa_max = soa_length + soa_offset;
/* Decompress the first DNS name in the record (which is the
* primary DNS server name) */
d.name = buf + *buf_offset;
dns_extract_name(hdr, soa_offset, soa_max, &d);
soa_offset = dns_name_skip(hdr, soa_offset, soa_max);
*buf_offset += d.length;
buf[*buf_offset] = 0;
*buf_offset += 1;
/* Decompress the second DNS name in the record (which is the
* contact email address */
d.name = buf + *buf_offset;
dns_extract_name(hdr, soa_offset, soa_max, &d);
soa_offset = dns_name_skip(hdr, soa_offset, soa_max);
*buf_offset += d.length;
buf[*buf_offset] = 0;
*buf_offset += 1;
/* remainder */
if (soa_offset > soa_max)
return Failure;
memcpy(buf + *buf_offset, hdr+soa_offset, soa_max-soa_offset);
*buf_offset += soa_max - soa_offset;
return Success;
}
/*TODO: currently, nobody references this function*/
void dns_dynamic_update(struct Ferret *ferret, struct NetFrame *frame, const unsigned char *px, unsigned length, struct DNS *dns)
{
unsigned i;
for (i=0; i<dns->answer_count; i++) {
char name[256];
unsigned name_length;
unsigned x;
struct DNSRECORD *rec = &dns->answers[i];
name_length = dns_extract_name(frame, px, length, rec->name_offset, name, sizeof(name));
x = rec->clss<<16 | rec->type;
SAMPLE(ferret,"DynDNS", JOT_NUM("Prereq", x));
switch (rec->type) {
case 0x0001: /*A*/
switch (rec->clss) {
case 0x0001: /*INTERNET*/
{
unsigned ip_address = ex32be(px+rec->rdata_offset);
if (rec->rdata_length != 4)
FRAMERR(frame, "dns: data not 4-bytes long, was %d-bytes instead (class=%d, type=%d, name=%s)\n", rec->rdata_length, rec->clss, rec->type, name);
JOTDOWN(ferret,
JOT_IPv4("ID-IP", ip_address),
JOT_PRINT("name", name, name_length),
0);
JOTDOWN(ferret,
JOT_SZ("proto","NETBIOS"),
JOT_SZ("op","register"),
JOT_SRC("ip.src", frame),
JOT_PRINT("name", name, name_length),
JOT_IPv4("address", ip_address),
0);
}
break;
default:
FRAMERR(frame, "dns: unknown class=%d (type=%d, name=%s)\n", rec->clss, rec->type, name);
}
break;
}
}
}
static void extract_name(
unsigned char *dst, unsigned *dst_offset, size_t dst_max,
const unsigned char *src, unsigned *src_offset, size_t src_max)
{
struct DomainPointer rrname;
if (*dst_offset + 256 > dst_max)
return;
rrname.name = dst + *dst_offset;
dns_extract_name(src, *src_offset, (unsigned)src_max, &rrname);
*dst_offset += rrname.length;
dst[*dst_offset] = 0;
*dst_offset += 1;
*src_offset = dns_name_skip(src, *src_offset, (unsigned)src_max);
}
void process_dns(struct Ferret *ferret, struct NetFrame *frame, const unsigned char *px, unsigned length)
{
unsigned offset;
struct DNS dns[1];
unsigned record_count;
unsigned total_records;
unsigned i;
/* Count the number of DNS packets we process. This includes
* all types of DNS */
ferret->statistics.dns++;
memset(dns, 0, sizeof(dns[0]));
if (length < 12) {
/* Regress: defcon2008-dns2.pcap(95639) */
; //FRAMERR(frame, "dns: frame too short\n");
return;
}
/* Parse the DNS header, the 'fixed' portion of the packet
* before the variable length records
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
ID A 16 bit identifier assigned by the program that
generates any kind of query. This identifier is copied
the corresponding reply and can be used by the requester
to match up replies to outstanding queries.
QR A one bit field that specifies whether this message is a
query (0), or a response (1).
OPCODE A four bit field that specifies kind of query in this
message. This value is set by the originator of a query
and copied into the response. The values are:
0 a standard query (QUERY)
1 an inverse query (IQUERY)
2 a server status request (STATUS)
3-15 reserved for future use
AA Authoritative Answer - this bit is valid in responses,
and specifies that the responding name server is an
authority for the domain name in question section.
Note that the contents of the answer section may have
multiple owner names because of aliases. The AA bit
corresponds to the name which matches the query name, or
the first owner name in the answer section.
TC TrunCation - specifies that this message was truncated
due to length greater than that permitted on the
transmission channel.
RD Recursion Desired - this bit may be set in a query and
is copied into the response. If RD is set, it directs
the name server to pursue the query recursively.
Recursive query support is optional.
RA Recursion Available - this be is set or cleared in a
response, and denotes whether recursive query support is
available in the name server.
Z Reserved for future use. Must be zero in all queries
and responses.
RCODE Response code - this 4 bit field is set as part of
responses. The values have the following
interpretation:
0 No error condition
1 Format error - The name server was
unable to interpret the query.
2 Server failure - The name server was
unable to process this query due to a
problem with the name server.
3 Name Error - Meaningful only for
responses from an authoritative name
server, this code signifies that the
domain name referenced in the query does
not exist.
4 Not Implemented - The name server does
not support the requested kind of query.
5 Refused - The name server refuses to
perform the specified operation for
policy reasons. For example, a name
server may not wish to provide the
information to the particular requester,
or a name server may not wish to perform
a particular operation (e.g., zone
6-15 Reserved for future use.
QDCOUNT an unsigned 16 bit integer specifying the number of
entries in the question section.
ANCOUNT an unsigned 16 bit integer specifying the number of
resource records in the answer section.
NSCOUNT an unsigned 16 bit integer specifying the number of name
server resource records in the authority records
section.
ARCOUNT an unsigned 16 bit integer specifying the number of
resource records in the additional records section.
*/
dns->id = ex16be(px+0);
dns->is_response = ((px[2]&0x80) != 0);
dns->opcode = (px[2]>>3)&0x01F;
dns->flags = ex16be(px+2)&0x7F0;
dns->rcode = px[3]&0x0F;
dns->question_count = ex16be(px+4);
dns->answer_count = ex16be(px+6);
dns->authority_count = ex16be(px+8);
dns->additional_count = ex16be(px+10);
/* Remember a total count of the records. There are a lot of corrupted packets
* with data after the counted records, so we need to stop parsing once all
* the counted records have been parsed. */
total_records = dns->question_count + dns->answer_count + dns->authority_count + dns->additional_count;
offset = 12;
record_count = 0;
/* After parsing the fixed header, we no PRE-PROCESS the variable length records.
* All we want to do at this point is to find their locations within the packet.
* The reason we want to pre-process these is that some records will refer to
* other records in the same packet. A good example are CNAME records
* that require looking up other records in order to fully resolve. We can
* do the resolution easier if we can preprocess the list first */
while (offset < length && record_count < 100) {
struct DNSRECORD *rec = &dns->records[record_count];
/* Even if there is remaining data in the packet, do not parse past
* the total count of all the records */
if (record_count >= total_records) {
SAMPLE(ferret,"dns", JOT_NUM("too-many-records", total_records));
break;
}
/* NAME
* The first part of a DNS record is the variable length name. The name
* consists of a sequence of LABELS. Each label starts with a tag. The
* tag can be one of three things:
* - a value of zero, which ends the name
* - a length from 1-63, which means we need to continue processing
* more labels
* - a two-byte 'pointer' to the remainder of the name, which means that
* we stop pre-processing the name. We don't actually parse out the
* full name at this stage in the code (so we won't follow that pointer),
* we are just concerned with skipping the name at this point. */
rec->name_offset = offset;
while (offset < length) {
/* Test for end label */
if (px[offset] == 0x00) {
offset++;
break;
}
/* Test for compression 'pointer' */
if (px[offset] & 0xC0) {
offset += 2;
break;
}
/* Skip the 'length' number of bytes, plus the length byte itself */
offset += px[offset] + 1;
if (offset > length) {
FRAMERR(frame, "dns: past end of packet\n");
return;
}
}
/* Now parse out the 'type' and 'class' fields. These are the
* 4 bytes immediately following the name */
if (offset + 4 > length) {
FRAMERR(frame, "dns: past end of packet\n");
return;
}
rec->type = ex16be(px+offset+0);
rec->clss = ex16be(px+offset+2);
offset += 4;
record_count++;
/* If this is a 'question' record, then we don't do any further processing.
* Since question records are just asking for data, they don't contain
* any data themselves. Otherwise, if the record will contain data that
* we need to also parse */
if (record_count <= dns->question_count)
continue;
/* This bit of code parses out the remainder of the data in the record. For
* the most part, we just need to parse the 'length' field for the record
* data, remember it for use later, then skip the remainder of this record
* and continue processing the next record */
if (offset + 6 > length) {
/* Regress: defcon2008-dns2.pcap(88069) */
FRAMERR(frame, "dns: past end of packet\n");
return;
}
rec->ttl = ex32be(px+offset+0);
rec->rdata_length = ex16be(px+offset+4);
offset += 6;
rec->rdata_offset = offset;
offset += rec->rdata_length;
if (offset > length) {
FRAMERR(frame, "dns: past end of packet\n");
return;
}
}
dns->record_count = record_count;
/* We stored the records in one large array, but there are four kinds
* of records (questions, answers, authority, additional). We figure out
* which records belong to which type according to the counts */
if (dns->question_count > record_count) {
dns->question_count = record_count;
FRAMERR(frame, "%s: bad record count\n", "DNS");
}
if (dns->answer_count > record_count - dns->question_count) {
dns->answer_count = record_count - dns->question_count;
/* Regress: defcon2008-dns2.pcap(158112) */
; //FRAMERR(frame, "%s: bad record count\n", "DNS");
}
if (dns->authority_count > record_count - dns->question_count - dns->answer_count) {
dns->authority_count = record_count - dns->question_count - dns->answer_count;
FRAMERR(frame, "%s: bad record count\n", "DNS");
}
if (dns->additional_count > record_count - dns->question_count - dns->answer_count - dns->authority_count) {
dns->additional_count = record_count - dns->question_count - dns->answer_count - dns->authority_count;
FRAMERR(frame, "%s: bad record count\n", "DNS");
}
dns->questions = &dns->records[0];
dns->answers = &dns->records[dns->question_count];
dns->authorities = &dns->records[dns->question_count + dns->answer_count];
dns->additionals = &dns->records[dns->question_count + dns->answer_count + dns->authority_count];
/*
* First, we parse out all the question records. These don't contain any data
* themselves, but they do give us interesting information about what a client
* is looking for. Also, some protocols, such as NetBIOS and mDNS/Bonjour will
* tell us additional information about the client.
*/
if (dns->is_response && dns->rcode == 0)
for (i=0; i<dns->question_count; i++) {
struct DNSRECORD *rec = &dns->questions[i];
dns_parse_question_record(ferret, frame, px, length, rec, dns);
}
/* Now parse all the resource records after the questions */
for (i=0; i<dns->answer_count; i++) {
struct DNSRECORD *rec = &dns->answers[i];
dns_parse_resource_record(ferret, frame, px, length, rec, dns);
}
for (i=0; i<dns->authority_count; i++) {
struct DNSRECORD *rec = &dns->authorities[i];
dns_parse_resource_record(ferret, frame, px, length, rec, dns);
}
for (i=0; i<dns->additional_count; i++) {
struct DNSRECORD *rec = &dns->additionals[i];
dns_parse_resource_record(ferret, frame, px, length, rec, dns);
}
#if 0
switch (dns->opcode) {
case 0x00: /*query request*/
case 0x10: /*query response */
switch (dns->rcode) {
case 0:
case 3: /* No such name */
SAMPLE(ferret,"DNS", JOT_NUM("rcode", dns->rcode));
break;
case 2: /* Server error */
SAMPLE(ferret,"DNS", JOT_NUM("rcode", dns->rcode));
break;
default:
FRAMERR(frame, "dns: unknown rcode=%d (opcode=%d)\n", dns->rcode, dns->opcode);
}
break;
case 0x06: /*release*/
switch (dns->rcode) {
case 0:
for (i=0; i<dns->additional_count; i++) {
char name[256];
unsigned name_length;
struct DNSRECORD *rec = &dns->additionals[i];
if (rec->type == 0x8001)
FRAMERR(frame, "test\n");
name_length = dns_extract_name(frame, px, length, rec->name_offset, name, sizeof(name));
switch (rec->type) {
case 0x0020: /*NETBIOS */
switch (rec->clss) {
case 0x0001: /*INTERNET*/
{
unsigned ip_address = ex32be(px+rec->rdata_offset+2);
char netbios_name[256];
if (rec->rdata_length != 6)
FRAMERR(frame, "dns: data not 4-bytes long, was %d-bytes instead (class=%d, type=%d, name=%s)\n", rec->rdata_length, rec->clss, rec->type, name);
translate_netbios_name(frame, name, netbios_name, sizeof(netbios_name));
JOTDOWN(ferret,
JOT_SZ("proto","NETBIOS"),
JOT_SZ("op","release"),
JOT_DST("ip.src", frame),
JOT_PRINT("name", netbios_name, strlen(netbios_name)),
JOT_IPv4("address", ip_address),
0);
JOTDOWN(ferret,
JOT_IPv4("ID-IP", ip_address),
JOT_PRINT("netbios", netbios_name, strlen(netbios_name)),
0);
}
break;
default:
FRAMERR(frame, "dns: unknown class=%d (type=%d, name=%s)\n", rec->clss, rec->type, name);
}
break;
default:
FRAMERR(frame, "dns: unknown type=%d (class=%d, name=%s)\n", rec->type, rec->clss, name);
}
}
}
break;
case 0x05: /*netbios registration request*/
if (frame->dst_port == 53)
dns_dynamic_update(ferret, frame, px, length, dns);
else
process_request_update(ferret, frame, px, length, dns);
break;
case 0x08:
for (i=0; i<dns->additional_count; i++)
DECODEANSWER(ferret, frame, px, length, dns, &dns->additionals[i], "refresh");
break;
case 0x01: /*inverse query request*/
case 0x11: /*inverse query reqsponse*/
case 0x02: /*status request*/
case 0x12: /*status response*/
case 0x04: /*notify request*/
case 0x14: /*notify response*/
case 0x15: /*update response*/
case 0x0f: /*multi-home registration*/
for (i=0; i<dns->additional_count; i++)
DECODEANSWER(ferret, frame, px, length, dns, &dns->additionals[i], "multi-home");
break;
default:
FRAMERR(frame, "dns: unknown opcode %d\n", dns->opcode);
}
#endif
}
static void
dns_parse_question_record(struct Ferret *ferret, struct NetFrame *frame,
const unsigned char *px, unsigned length,
struct DNSRECORD *rec, struct DNS *dns)
{
char name[512]; /* reserve a longer name than the max theoretical limit */
unsigned name_length;
/* If this is actually a bonjour packet, then pass it off to the
* Bonjour module */
if (!dns->is_response && frame->dst_port == 5353)
bonjour_parse_question_record(ferret, frame, px, length, rec, dns);
else if (dns->is_response && frame->src_port == 5353)
bonjour_parse_question_record(ferret, frame, px, length, rec, dns);
/* First, let's extract a pretty version of the name */
name_length = dns_extract_name(frame, px, length, rec->name_offset, name, sizeof(name));
switch (rec->type<<16 | rec->clss) {
case TYPECLASS(1,1): /* type=A(IPv4 address), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","A"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
case TYPECLASS(2,1): /* type=NS(name-server), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","NS"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
case TYPECLASS(6,1): /* type=SOA(Start of Authority), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","SOA"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
case TYPECLASS(10,1): /* type=NULL, class=INTERNET*/
/* Regress: defcon2008-dns2.pcap(100803): name=Vaaaaiaqaac.tunnel.fastcoder.net */
/* I'm not sure what this is, other than passing data as Null records.
* This would be a good thing for an intrusion-detection system to trigger
* on. */
break;
case TYPECLASS(12,1): /* type=PTR(pointer, aka. reverse), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("op","reverse"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
case TYPECLASS(13,1): /* type=HINFO, class=INTERNET*/
/* Regress: defcon2008-dns2.pcap(292428) */
break;
case TYPECLASS(15,1): /* type=MX, class=INTERNET*/
/* Regress: defcon2008-dns2.pcap(18661) */
break;
case TYPECLASS(16,1): /* type=TXT(text), class=INTERNET*/
/* CASE: I see these in mDNS. A machine sends out a query for a
* record to the multi-cast address right before it then multi-casts
* the answer. I don't think there is anything useful to extract here
* at this time */
if (!is_valid_opcode(dns->opcode, OP_QUERY, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
break;
case TYPECLASS(35,1): /* type=NAPTR(naming authority pointer), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, OP_QUERY, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
/* Reference: defcon2008-dns2.pcap(277617) */
break;
case TYPECLASS(0x1c,1): /* type=AAAA(IPv6 address), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","AAAA"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
case TYPECLASS(0x1c,0x8001): /* type=AAAA(IPv6 address), class=mDNS-FLUSH*/
if (!is_valid_opcode(dns->opcode, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
/* TODO: move this to the mDNS-Bonjour parser */
JOTDOWN(ferret,
JOT_SZ("proto","MDNS"),
JOT_SZ("query","AAAA"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("flush", name, name_length),
0);
break;
case TYPECLASS(0x21,1): /* type=SRV(Service Location), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, OP_QUERY, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","srv"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
/*case TYPECLASS(255,1):*/ /* type=ANY, class=INTERNET*/
case TYPECLASS(255,0x8001): /* type=ANY, class=FLUSH(mDNS/Bonjour)*/
if (!is_valid_opcode(dns->opcode, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("op","flush"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
if (endsWith(name, "._ipp._tcp.local")) {
JOTDOWN(ferret,
"Bonjour", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("Printer", name, name_length-strlen("._ipp._tcp.local")),
0);
} else if (endsWith(name, ".local"))
JOTDOWN(ferret,
"ID-IP", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length-strlen(".local")),
0);
else
FRAMERR(frame, "%s: unknown value: %s\n", "dns", name);
break;
case TYPECLASS(255,1): /* type=ANY, class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("query","ANY"),
"ip.src", dns->is_response?REC_FRAMEDST:REC_FRAMESRC, frame, -1,
JOT_PRINT("name", name, name_length),
0);
break;
default:
FRAMERR(frame, "dns: unknown [type=0x%x(%d), class=0x%x(%d)] name=%s)\n",
rec->type, rec->type,
rec->clss, rec->clss,
name);
}
}
/**
* This is the main function of the DNS parser.
*
* This is where the each DNS 'answer' (or 'additional' or 'authoritative')
* record is parsed. Mostly, we ignore the return code, though some functions
* pay attention to and provide slightly different information depending
* upon the opcode.
*/
static void
dns_parse_resource_record(struct Ferret *ferret, struct NetFrame *frame,
const unsigned char *px, unsigned length,
struct DNSRECORD *rec, struct DNS *dns)
{
char name[512]; /* reserve a longer name than the max theoretical limit */
unsigned name_length;
char name2[512]; /* reserve a longer name than the max theoretical limit */
unsigned name2_length;
unsigned ip_address;
unsigned offset = rec->rdata_offset;
unsigned offset_max = MIN(rec->rdata_offset+rec->rdata_length, length);
/* MULTICAST DNS (mDNS): handle the multicast DNS records differently
* from normal DNS records. */
if (!dns->is_response && frame->dst_port == 5353) {
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
return;
} else if (dns->is_response && (frame->src_port == 5353 || (frame->dst_port == 5353 && frame->src_port != 53))) {
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
return;
}
/* NETBIOS: handle NetBIOS records differently from normal DNS records */
if (!dns->is_response && frame->dst_port == 137) {
netbios_parse_resource_record(ferret, frame, px, length, rec, dns);
return;
} else if (dns->is_response && frame->src_port == 137) {
netbios_parse_resource_record(ferret, frame, px, length, rec, dns);
return;
}
/* First, let's extract a pretty version of the name */
name_length = dns_extract_name(frame, px, length, rec->name_offset, name, sizeof(name));
if (rec->type == 0x8001)
FRAMERR(frame, "TODO\n");
if (rec->clss == 0xfe)
return;
/* RFC2671 - Extension Mechanisms for DNS (EDNS0) */
if (rec->type == 41) {
/* Regress: defcon2008/dump000.pca(12541) */
/* TODO: parse this */
return;
}
/* Haven't implemented dynamic update yet
* TODO: */
if (dns->opcode == 21 || dns->opcode == 5)
return;
switch (rec->type<<16 | rec->clss) {
case TYPECLASS(1,0x8001): /* type=A(IPv4 address), class=INTERNET(cache flush) */
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
break;
case TYPECLASS(1,1): /* type=A(IPv4 address), class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, 5, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
ip_address = ex32be(px+rec->rdata_offset);
if (rec->rdata_length != 4)
FRAMERR(frame, "dns: data not 4-bytes long, was %d-bytes instead (class=%d, type=%d, name=%s)\n", rec->rdata_length, rec->clss, rec->type, name);
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_IPv4("address", ip_address),
0);
break;
case TYPECLASS(2,1): /* type=NS, class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
name2_length = dns_extract_name(frame, px, length, rec->rdata_offset, name2, sizeof(name2));
ip_address = dns_resolve_alias(frame, px, length, dns, name2, 0);
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_PRINT("Name-Server", name2, name2_length),
JOT_IPv4("address", ip_address),
0);
break;
case TYPECLASS(5,1): /*type=CNAME(aliased canonical name), class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, 5, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
name2_length = dns_extract_name(frame, px, length, rec->rdata_offset, name2, sizeof(name2));
ip_address = dns_resolve_alias(frame, px, length, dns, name2, 0);
if (ip_address != 0) {
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_IPv4("alias",ip_address),
0);
}
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_PRINT("alias", name2, name2_length),
0);
break;
case TYPECLASS(6,1): /*type=SOA, class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
/*
* Authoritative Name Server
*/
name2_length = dns_extract_name(frame, px, length, offset, name2, sizeof(name2));
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_SZ("SOA", "Start of zone authority"),
JOT_PRINT("Name-Server", name2, name2_length),
0);
ip_address = dns_resolve_alias(frame, px, length, dns, name2, 0);
if (ip_address)
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_SZ("SOA", "Start of zone authority"),
JOT_PRINT("Name-Server", name2, name2_length),
JOT_IPv4("address", ip_address),
0);
skip_name(px, length, &offset);
/* Contact */
if (offset < offset_max) {
name2_length = dns_extract_name(frame, px, length, offset, name2, sizeof(name2));
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_SZ("SOA", "Start of zone authority"),
JOT_PRINT("Contact", name2, name2_length),
0);
skip_name(px, length, &offset);
}
break;
case TYPECLASS(10,1): /* type=NULL, class=INTERNET*/
/* Regress: defcon2008-dns2.pcap(100803): name=Vaaaaiaqaac.tunnel.fastcoder.net */
/* I'm not sure what this is, other than passing data as Null records.
* This would be a good thing for an intrusion-detection system to trigger
* on. */
break;
case TYPECLASS(12,0x8001): /*type=PTR, class=INTERNET */
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
break;
case TYPECLASS(12,1): /*type=PTR(pointer reverse lookup), class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
if (name_length > 6 && memcmp(name+name_length-6, ".local", 6) == 0) {
JOTDOWN(ferret,
JOT_SRC("ID-IP", frame),
JOT_PRINT("Service", name,name_length),
0);
/* Extract MAC address */
{
const unsigned char *p_name;
unsigned name_length;
const unsigned char *p_mac = find_mac(px, MIN(length, rec->rdata_offset+rec->rdata_length), rec->rdata_offset, &p_name, &name_length);
if (p_mac) {
JOTDOWN(ferret,
JOT_SRC("ID-IP", frame),
JOT_PRINT("mac", p_mac, 19),
0);
JOTDOWN(ferret,
JOT_SRC("ID-IP", frame),
JOT_PRINT("name", p_name, name_length),
0);
}
}
} else if (endsWith(name, ".in-addr.arpa")) {
/* Extract a 4-byte IPv4 address
* Example: "18.0.0.10.in-addr.arpa"*/
unsigned ipv4=0;
unsigned i;
unsigned j=0;
for (i=0; i<4; i++) {
unsigned num = 0;
for (; name[j] && name[j] != '.'; j++) {
if ('0' <= name[j] && name[j] <= '9')
num = num * 10 + name[j]-'0';
}
while (name[j] == '.')
j++;
ipv4 |= num<<(i*8);
}
/* Now get the name it points to */
name2_length = dns_extract_name(frame, px, length, offset, name2, sizeof(name2));
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name2, name2_length),
JOT_IPv4("ID-IP", ipv4),
JOT_SRC("dnssrv", frame),
0);
} else
; //FRAMERR(frame, "dns: unknown PTR record\n");
break;
case TYPECLASS(13,0x8001): /*type=HINFO, class=INTERNET */
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
break;
case TYPECLASS(15,1): /*type=MX, class=INTERNET */
/* Regress: defcon2008-dns2.pcap(18661) */
break;
case TYPECLASS(16,0x8001): /*type=TXT, class=INTERNET(cache flush)*/
bonjour_parse_resource_record(ferret, frame, px, length, rec, dns);
break;
case TYPECLASS(16,1): /*type=TXT, class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, 5, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
if (stricmp(name, "current.cvd.clamav.net") == 0) {
/* This is a single string containing a version string, like:
* 0.91.1:44:3855:1186270141:1
*/
break;
} else if (starts_with("_DM-NOTIFICATION.", name, strlen(name))) {
/* Regress: defcon2008\dump001.pcap(87082) */
/* TODO */
break;
} else if (endsWith(name, "._workstation._tcp.local")) {
/* Regress: defcon2008-dns2.pcap(56127): "mike-desktop [00:0c:29:f6:58:ca]._workstation._tcp.local" */
break;
} else if (endsWith(name, ".asn.cymru.com")) {
/* Regress: defcon2008-dns2.pcap(98958) */
/* This is a system for mapping IP to ASN numbers:
* http://www.team-cymru.org/Services/ip-to-asn.html */
break;
} else if (endsWith(name, ".wrs.trendmicro.com")) {
/* Regress: defcon2008-dns2.pcap(184904) */
/* Appears to check whether IP addresses are trustworthy */
break;
} else {
FRAMERR(frame, "%s: unknown TXT record %s", "DNS", name);
}
break;
case TYPECLASS(0x1c,1): /*type=AAAA(IPv6 address), class=INTERNET*/
case TYPECLASS(0x1c,255): /*type=AAAA(IPv6 address), class=INTERNET*/
if (!is_valid_opcode(dns->opcode, 0x10, 5, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
switch (dns->opcode) {
case 0x10:
{
const unsigned char *ipv6_address = px+rec->rdata_offset;
if (rec->rdata_length != 16)
FRAMERR(frame, "dns: data not 16-bytes long, was %d-bytes instead (class=%d, type=%d, name=%s)\n", rec->rdata_length, rec->clss, rec->type, name);
JOTDOWN(ferret,
JOT_SZ("proto","DNS"),
JOT_SZ("op","lookup"),
JOT_SRC("ip.src", frame),
JOT_PRINT("name", name, name_length),
JOT_IPv6("address", ipv6_address, 16),
0);
}
case 5: /* dynamic update*/
/* Regress: defcon2008-dns2.pcap(7958) */
break;
default:
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
}
break;
case TYPECLASS(33,1): /*type=SRV, class=INTERNET */
if (!is_valid_opcode(dns->opcode, 0x10, -1)) {
FRAMERR(frame, "%s: unknown opcode=%d\n", "DNS", dns->opcode);
return;
}
if (rec->rdata_length < 7)
FRAMERR(frame, "dns: unknown type=%d (class=%d, name=%s)\n", rec->type, rec->clss, name);
else {
unsigned port = px[rec->rdata_offset+4]<<8 | px[rec->rdata_offset+5];
name2_length = dns_extract_name(frame, px, length, rec->rdata_offset+6, name2, sizeof(name2));
ip_address = dns_resolve_alias(frame, px, length, dns, name2, 0);
if (ip_address != 0) {
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_PRINT("Server", name2, name2_length),
JOT_NUM("Port", port),
JOT_IPv4("IPv4",ip_address),
0);
} else
JOTDOWN(ferret,
JOT_PRINT("ID-DNS", name, name_length),
JOT_PRINT("Server", name2, name2_length),
JOT_NUM("Port", port),
0);
}
break;
default:
FRAMERR(frame, "dns: unknown type=%d (class=%d, name=%s)\n", rec->type, rec->clss, name);
}
}
static int
grab_dns_response(struct Catalog *catalog, const unsigned char *px, unsigned offset, unsigned max)
{
struct DNS_Incoming dns[1];
unsigned i;
struct DomainPointer domain;
unsigned char domain_buffer[256];
char unsigned tmp_buffer[65536];
unsigned tmp_offset;
unsigned src_offset;
/* kludge */
px += offset;
offset = 0;
max -= offset;
domain.name = domain_buffer;
proto_dns_parse(dns, px, offset, max);
if (!dns->is_valid)
return Failure;
if (!dns->qr)
return Failure;
for (i=dns->qdcount; i<dns->rr_count; i++) {
int type;
int xclass;
unsigned ttl;
unsigned rdlength;
const unsigned char *rdata;
offset = dns->rr_offset[i];
/* extract the domain name */
dns_extract_name(px, offset, max, &domain);
offset = dns_name_skip(px, offset, max);
/* extract the data */
if (offset + 10 > max)
continue;
type = px[offset+0]<<8 | px[offset+1];
xclass = px[offset+2]<<8 | px[offset+3];
if (xclass != 1)
continue;
ttl = px[offset+4]<<24 | px[offset+5]<<16 | px[offset+6]<<8 | px[offset+7];
rdlength = px[offset+8]<<8 | px[offset+9];
rdata = &px[offset + 10];
offset += 10;
/* insert the data into the catalog */
if (offset + rdlength > max)
continue;
else
offset += rdlength;
tmp_offset = 0;
src_offset = (unsigned)(rdata - px);
switch (type) {
case 41: /*OPT*/
continue;
case TYPE_NS:
case TYPE_CNAME:
extract_name( tmp_buffer, &tmp_offset, sizeof(tmp_buffer),
px, &src_offset, max);
rdata = tmp_buffer;
rdlength = tmp_offset;
break;
case TYPE_SOA:
extract_name( tmp_buffer, &tmp_offset, sizeof(tmp_buffer),
px, &src_offset, max);
extract_name( tmp_buffer, &tmp_offset, sizeof(tmp_buffer),
px, &src_offset, max);
extract_copy( tmp_buffer, &tmp_offset, sizeof(tmp_buffer),
px, &src_offset, max,
offset-src_offset);
rdata = tmp_buffer;
rdlength = tmp_offset;
break;
case TYPE_RRSIG:
//printf(".");
break;
}
zonefile_load(
domain,
root,
type,
ttl,
rdlength,
rdata,
10000,
catalog);
}
return Success;
}
/**
* DNS: Handles DNS-messages according to Receive-handle diagram.
* Sets dns_result_ip for given dns_domain_name (see dns_get_ip)
* or signals error condition occurs during DNS-resolving process
* by setting dns_error flag.
*
* @param packet DNS-packet to be handled
* @param packetsize length of the packet
* @return ZERO - packet handled successfully;
* NON ZERO - packet was not handled (e.g. bad format)
* @see dns_get_ip
* @see receive_ether
* @see dnshdr
*/
int32_t
handle_dns(uint8_t * packet, int32_t packetsize)
{
struct dnshdr * dnsh = (struct dnshdr *) packet;
uint8_t * resp_section = packet + sizeof(struct dnshdr);
/* This string stores domain name from DNS-packets */
static int8_t handle_domain_name[0x100];
int i;
// verify ID - is it response for our query?
if (dnsh -> id != htons(0x1234))
return 0;
// Is it DNS response?
if ((dnsh -> flags & htons(DNS_FLAG_MSGTYPE)) != htons(DNS_FLAG_SRESPONSE))
return 0;
// Is error condition occurs? (check error field in incoming packet)
if ((dnsh -> flags & htons(DNS_FLAG_RCODE)) != DNS_RCODE_NERROR) {
dns_error = 1;
return 0;
}
/* Pass all (qdcount) records in question section */
for (i = 0; i < htons(dnsh -> qdcount); i++) {
// pass QNAME
resp_section = dns_extract_name((uint8_t *) dnsh, (int8_t *) resp_section,
handle_domain_name);
if (resp_section == NULL) {
return -1; // incorrect domain name (bad packet)
}
// pass QTYPE & QCLASS
resp_section += 4;
}
/* Handle all (ancount) records in answer section */
for (i = 0; i < htons(dnsh -> ancount); i++) {
// retrieve domain name from the packet
resp_section = dns_extract_name((uint8_t *) dnsh, (int8_t *) resp_section,
handle_domain_name);
if (resp_section == NULL) {
return -1; // incorrect domain name (bad packet)
}
// Check the class of the query (should be IN for Internet)
if (* (uint16_t *) (resp_section + 2) == htons(DNS_QCLASS_IN)) {
// check if retrieved name fit raw or canonical domain name
if (!strcmp((char *) handle_domain_name, (char *) dns_domain_name) ||
!strcmp((char *) handle_domain_name, (char *) dns_domain_cname)) {
switch (htons(* (uint16_t *) resp_section)) {
case DNS_QTYPE_A :
// rdata contains IP
dns_result_ip = htonl(* (uint32_t *) (resp_section + 10));
return 0; // IP successfully obtained
case DNS_QTYPE_CNAME :
// rdata contains canonical name, store it for further requests
if (dns_extract_name((uint8_t *) dnsh, (int8_t *) resp_section + 10,
dns_domain_cname) == NULL) {
// incorrect domain name (bad packet)
return -1;
}
break;
case DNS_QTYPE_AAAA :
memcpy(dns_result_ipv6, (resp_section + 10), 16);
return 0; // IP successfully obtained
break;
}
}
// continue with next record in answer section
resp_section += htons(* (uint16_t *) (resp_section + 8)) + 10;
}
}
return 0; // Packet successfully handled but IP wasn't obtained
}