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DNSQuery.cc
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DNSQuery.cc
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//
// Copyright 2009-2017 M. Shulhan (ms@kilabit.info). All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
#include "DNSQuery.hh"
namespace vos {
const char* _DNS_HDR_TYPE_NAME[] = {
"query"
, "response"
};
const char* _DNS_HDR_OPCODE_NAME[] = {
"QUERY"
, "IQUERY"
, "STATUS"
};
const char* _DNS_HDR_RCODE_NAME[RCODE_SIZE + 1] = {
"OK"
, "FORMAT_ERROR"
, "SERVER_FAILURE"
, "NAME_ERROR"
, "NOT_IMPLEMENTED"
, "REFUSED"
, "UNKNOWN"
};
const char* DNSQuery::__cname = "DNSQuery";
/**
* @method : DNSQuery::DNSQuery
*/
DNSQuery::DNSQuery() : Buffer()
, _id(0)
, _flag(0)
, _n_qry(0)
, _n_ans(0)
, _n_aut(0)
, _n_add(0)
, _q_len (0)
, _q_type(0)
, _q_class(0)
, _name()
, _bfr_type(BUFFER_IS_UDP)
, _rr_ans()
, _rr_aut()
, _rr_add()
, _rr_ans_p(NULL)
, _rr_aut_p(NULL)
, _rr_add_p(NULL)
, _ans_ttl_max(0)
, _attrs (DNS_IS_QUERY)
{}
/**
* @method : DNSQuery::~DNSQuery
*/
DNSQuery::~DNSQuery()
{}
/**
* @method : DNSQuery::set_buffer
* @param :
* > bfr : pointer to DNS packet.
* > type : type of DNS packet origin, TCP or UDP.
* @return :
* < 0 : success.
* < -1 : fail.
* @desc : set DNSQuery packet to 'bfr'.
*/
int DNSQuery::set(const Buffer* bfr, const int type)
{
if (!bfr) {
return -1;
}
if (type != BUFFER_IS_UDP && type != BUFFER_IS_TCP) {
return -1;
}
if (_id) {
reset();
}
_bfr_type = type;
Error err = copy(bfr);
if (err != NULL) {
return -1;
}
return 0;
}
DNSQuery* DNSQuery::duplicate ()
{
DNSQuery* dup = new DNSQuery ();
if (! dup) {
return NULL;
}
Error err = dup->copy_raw (_v, _i);
if (err != NULL) {
delete dup;
dup = NULL;
return NULL;
}
dup->_q_len = _q_len;
dup->_q_type = _q_type;
dup->_q_class = _q_class;
dup->_name.copy (&_name);
dup->_ans_ttl_max = _ans_ttl_max;
dup->_attrs = _attrs;
return dup;
}
/**
* @method : DNSQuery::to_udp
* @param :
* > tcp : pointer to DNS packet from TCP socket or buffer.
* @return :
* < 0 : success.
* < -1 : fail.
* @desc : set content of DNSQuery buffer to UDP packet using packet
* from TCP. If 'tcp' is nil then convert the current buffer for UDP packet.
*/
int DNSQuery::to_udp(const Buffer *tcp)
{
if (!tcp) {
if (_bfr_type == BUFFER_IS_UDP) {
return 0;
}
_i -= DNS_TCP_HDR_SIZE;
memmove(_v, &_v[DNS_TCP_HDR_SIZE], _i);
_v[_i] = 0;
} else {
Error err = copy_raw(tcp->v(DNS_TCP_HDR_SIZE)
, tcp->len() - DNS_TCP_HDR_SIZE);
if (err != NULL) {
return -1;
}
}
_bfr_type = BUFFER_IS_UDP;
return 0;
}
/**
* @method : DNSQuery::to_tcp
* @param :
* > udp : pointer to DNS packet from UDP socket or buffer.
* @return :
* < 0 : success.
* < -1 : fail.
* @desc : set content of DNSQuery buffer to TCP packet using packet
* from UDP. If udp is nil then convert the current buffer for TCP packet.
*/
int DNSQuery::to_tcp(const Buffer* udp)
{
uint16_t size;
Error err;
if (!udp) {
if (_bfr_type == BUFFER_IS_TCP) {
return 0;
}
err = shiftr(DNS_TCP_HDR_SIZE);
if (err != NULL) {
return -1;
}
size = (uint16_t)(_i - DNS_TCP_HDR_SIZE);
size = htons(size);
memcpy(_v, &size, DNS_TCP_HDR_SIZE);
} else {
err = resize(udp->len() + DNS_TCP_HDR_SIZE);
if (err != NULL) {
return -1;
}
reset();
size = (uint16_t) udp->len();
memcpy(_v, &size, DNS_TCP_HDR_SIZE);
_i = DNS_TCP_HDR_SIZE;
err = append(udp);
if (err != NULL) {
return -1;
}
}
_bfr_type = BUFFER_IS_TCP;
return 0;
}
void DNSQuery::set_header (uint16_t id, uint16_t flag, uint16_t n_qry
, uint16_t n_ans
, uint16_t n_aut
, uint16_t n_add)
{
_id = htons (id);
_flag = htons (flag);
_n_qry = htons (n_qry);
_n_ans = htons (n_ans);
_n_aut = htons (n_aut);
_n_add = htons (n_add);
memcpy(_v , &_id , 2);
memcpy(&_v[2] , &_flag , 2);
memcpy(&_v[4] , &_n_qry , 2);
memcpy(&_v[6] , &_n_ans , 2);
memcpy(&_v[8] , &_n_aut , 2);
memcpy(&_v[10] , &_n_add , 2);
_i = DNS_HDR_SIZE;
_id = ntohs(_id);
_flag = ntohs(_flag);
_n_qry = ntohs(_n_qry);
_n_ans = ntohs(_n_ans);
_n_aut = ntohs(_n_aut);
_n_add = ntohs(_n_add);
}
/**
* @method : DNSQuery::create_question
* @param :
* > qname : a domain name.
* @return :
* < 0 : success.
* < -1 : fail.
* @desc : create question packet data to be send to server.
*/
int DNSQuery::create_question(const char* qname, const int type)
{
if (!qname) {
return -1;
}
size_t len = 0;
Buffer label;
reset(DNSQ_DO_ALL);
set_header ((uint16_t) (rand() % 65536)
, HDR_IS_QUERY | OPCODE_QUERY
, 1, 0, 0, 0);
_q_type = htons((uint16_t) type);
_q_class = htons(QUERY_C_IN);
_name.copy_raw(qname);
len = _name.len() + 16;
if (len > _l) {
Error err = resize(len);
if (err != NULL) {
return -1;
}
}
_i = DNS_HDR_SIZE;
DNS_rr::APPEND_DNS_LABEL (this, qname
, (unsigned int) strlen (qname));
append_bin(&_q_type, 2);
append_bin(&_q_class, 2);
_q_type = ntohs(_q_type);
_q_class = ntohs(_q_class);
return 0;
}
/**
* @method : DNSQuery::extract
* @param extract_rr : if !0 extract RR also.
* @return 0 : success, or buffer is empty.
* @return -1 : fail at extracting header.
* @return -2 : fail at extracting question.
* @return -3 : fail at extracting RR.
* @desc : extract contents of buffer (DNS packet).
*/
int DNSQuery::extract (const char extract_rr_flag)
{
if (is_empty()) {
return 0;
}
int s = 0;
int len = 0;
if (_bfr_type == BUFFER_IS_TCP) {
s = to_udp();
if (s < 0) {
return -1;
}
}
reset(DNSQ_DO_DATA_ONLY);
s = extract_header();
if (s < 0) {
return -1;
}
len = extract_question();
if (len <= 0) {
return -2;
}
s = extract_resource_record (extract_rr_flag);
if (s != 0) {
return -3;
}
return 0;
}
/**
* @method : DNSQuery::extract_header
* @return :
* < 0 : success.
* < -1 : fail.
* @desc : extract header of DNS packet.
*/
int DNSQuery::extract_header()
{
if (_i < DNS_HDR_SIZE) {
return -1;
}
memcpy(&_id , _v , 2);
memcpy(&_flag , &_v[2] , 2);
memcpy(&_n_qry , &_v[4] , 2);
memcpy(&_n_ans , &_v[6] , 2);
memcpy(&_n_aut , &_v[8] , 2);
memcpy(&_n_add , &_v[10] , 2);
_id = ntohs(_id);
_flag = ntohs(_flag);
_n_qry = ntohs(_n_qry);
_n_ans = ntohs(_n_ans);
_n_aut = ntohs(_n_aut);
_n_add = ntohs(_n_add);
return 0;
}
/**
* @method : DNSQuery::extract_question
* @return >0 : success, length of question, from header + label + type +
* class.
* @return -1 : fail.
* @desc : extract question data from buffer.
*/
int DNSQuery::extract_question()
{
// start from header length.
size_t startp = DNS_HDR_SIZE;
int len = 0;
// check if buffer size is smaller
if (startp > _i) {
return -1;
}
// extract question label
_name.reset();
len = extract_label(&_name, startp);
if (len < 0) {
return -1;
}
startp = startp + size_t(len);
// check 4 byte more for question type and class
len = int(startp) + 4;
if (size_t(len) > _i) {
return -1;
}
// extract question type and class
memcpy(&_q_type, &_v[startp], 2);
startp += 2;
memcpy(&_q_class, &_v[startp], 2);
_q_type = ntohs(_q_type);
_q_class = ntohs(_q_class);
// set question length, label length + 4 byte
_q_len = (uint16_t) (len - DNS_HDR_SIZE);
return len;
}
/**
* @method : DNSQuery::extract_resource_record
* @desc : Extract resourse record.
* @param extract_flag : what type of RR that will be extracted.
* @return 0 : success.
* @return -1 : fail, question is empty.
* @return -2 : fail at extracting RR answer.
* @return -3 : fail at extracting RR authority.
* @return -4 : fail at extracting RR additional.
*/
int DNSQuery::extract_resource_record (const char extract_flag)
{
int i = 0;
size_t len = 0;
DNS_rr* rr = NULL;
// check if question has been extracted.
if (_q_len == 0) {
int s = extract_question ();
if (s <= 0) {
return -1;
}
}
if (extract_flag < DNSQ_EXTRACT_RR_ANSWER) {
// nothing to extract, flag is zero.
return 0;
}
// now that we got _q_len, start extracting from there.
len = _q_len + DNS_HDR_SIZE;
_rr_ans_p = &_v[len];
for (i = 0; i < _n_ans; ++i) {
rr = extract_rr(&len);
if (!rr) {
return -2;
}
set_max_ttl_from_rr (rr);
_rr_ans.push_tail(rr);
}
if (extract_flag >= DNSQ_EXTRACT_RR_AUTH) {
_rr_aut_p = &_v[len];
for (i = 0; i < _n_aut; ++i) {
rr = extract_rr(&len);
if (!rr) {
return -3;
}
_rr_aut.push_tail(rr);
}
_rr_add_p = &_v[len];
if (extract_flag >= DNSQ_EXTRACT_RR_ADD) {
for (i = 0; i < _n_add; ++i) {
rr = extract_rr(&len);
if (!rr) {
return -4;
}
_rr_add.push_tail(rr);
}
}
}
return 0;
}
void DNSQuery::set_max_ttl_from_rr (const DNS_rr* rr)
{
if (rr->_type != _q_type) {
return;
}
if (rr->_class != _q_class) {
return;
}
if (rr->_ttl > _ans_ttl_max) {
_ans_ttl_max = rr->_ttl;
}
}
/**
* @method : DNSQuery::extract_rr
* @param:
* > offset : pointer to position of buffer after RR has been
* extracted.
* > type : type of the last extracted rr.
* @return:
* < DNS_rr* : success.
* < NULL : fail.
* @desc : extract Resource-Record (RR) from buffer 'bfr'.
*/
DNS_rr* DNSQuery::extract_rr(size_t* offset)
{
int s = 0;
DNS_rr* rr = new DNS_rr();
Error err;
if (!rr) {
return NULL;
}
/* Get RR NAME */
s = extract_label(&rr->_name, *offset);
if (s < 0) {
goto err;
}
rr->_name_len = (uint16_t) s;
*offset += size_t(s);
/* Check if buffer is wide enough to have rr type */
s = int(*offset) + 2;
if (size_t(s) > _i) {
return rr;
}
/* Get RR TYPE (2 bytes) */
memcpy(&rr->_type, &_v[*offset], 2);
rr->_type = ntohs(rr->_type);
*offset += 2;
/* Check if buffer is wide enough to have rr class */
s = int(*offset) + 2;
if (size_t(s) > _i) {
return rr;
}
/* Get RR CLASS (2 bytes) */
memcpy(&rr->_class, &_v[*offset], 2);
rr->_class = ntohs(rr->_class);
*offset += 2;
/* Check 4 byte TTL */
s = int(*offset) + 4;
if (size_t(s) > _i) {
return rr;
}
/* Get RR TTL */
memcpy(&rr->_ttl, &_v[*offset], 4);
rr->_ttl = ntohl(rr->_ttl);
rr->_ttl_p = &_v[*offset];
*offset += 4;
/* Check 2 bytes for DATALEN */
s = int(*offset) + 2;
if (size_t(s) > _i) {
return rr;
}
/* Get RR DATALEN */
memcpy(&rr->_len, &_v[*offset], 2);
rr->_len = ntohs(rr->_len);
*offset += 2;
/* Check if packet length is less equal than DATALEN */
s = int(*offset + rr->_len);
if (size_t(s) > _i) {
return rr;
}
/* Check if buffer size is enough, if not resize it DATALEN */
if (rr->_len > rr->size()) {
err = rr->resize(rr->_len);
if (err != NULL) {
goto err;
}
}
/* Get RR DATA */
rr->copy_raw(&_v[*offset], rr->_len);
switch (rr->_type) {
case QUERY_T_ADDRESS:
inet_ntop(AF_INET, rr->v(), (char*) rr->_data.v()
, socklen_t(rr->_data.size()));
rr->_data.set_len(strlen(rr->_data.v()));
*offset += 4;
break;
case QUERY_T_NAMESERVER:
case QUERY_T_CNAME:
s = extract_label(&rr->_data, *offset);
if (s != rr->_len) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_SOA:
s = extract_label(&rr->_data, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
s = extract_label(&rr->_data2, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
if ((*offset + 20) > _i) {
goto err;
}
memcpy(&rr->_serial, &_v[*offset], 4);
rr->_serial = ntohl(rr->_serial);
*offset += 4;
memcpy(&rr->_refresh, &_v[*offset], 4);
rr->_refresh = ntohl(rr->_refresh);
*offset += 4;
memcpy(&rr->_retry, &_v[*offset], 4);
rr->_retry = ntohl(rr->_retry);
*offset += 4;
memcpy(&rr->_expire, &_v[*offset], 4);
rr->_expire = ntohl(rr->_expire);
*offset += 4;
memcpy(&rr->_minimum, &_v[*offset], 4);
rr->_minimum = ntohl(rr->_minimum);
*offset += 4;
break;
case QUERY_T_PTR:
s = extract_label(&rr->_data, *offset);
if (s != rr->_len) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_HINFO:
s = extract_label(&rr->_data, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
s = extract_label(&rr->_data2, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_MX:
memcpy(&rr->_priority, &_v[*offset], 2);
rr->_priority = ntohs(rr->_priority);
*offset += 2;
s = extract_label(&rr->_data, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_TXT:
s = _extract_TXT(rr, *offset);
if (s != rr->_len) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_SRV:
memcpy(&rr->_priority, &_v[*offset], 2);
rr->_priority = ntohs(rr->_priority);
*offset += 2;
memcpy(&rr->_weight, &_v[*offset], 2);
rr->_weight = ntohs(rr->_weight);
*offset += 2;
memcpy(&rr->_port, &_v[*offset], 2);
rr->_port = ntohs(rr->_port);
*offset += 2;
s = extract_label(&rr->_data, *offset);
if (s < 0) {
goto err;
}
*offset += size_t(s);
break;
case QUERY_T_AAAA:
inet_ntop (AF_INET6, rr->v(), (char*) rr->_data.v()
, socklen_t(rr->_data.size()));
rr->_data.set_len(strlen(rr->_data.v()));
*offset += 16;
break;
default:
fprintf(stderr
, "[%s] extract_rr: (%s) Record type '%d' is not handle yet!\n"
, __cname, _name.chars(), rr->_type);
goto err;
}
return rr;
err:
if (LIBVOS_DEBUG) {
fprintf(stderr
, "[%s] extract_rr: error extracting record type '%d'!"
, __cname, rr->_type);
}
delete rr;
return NULL;
}
/**
* @method : DNSQuery::extract_label
* @param :
* > label : return value, content of DNS packet.
* > bfr_off : buffer offset.
* @return :
* > >=0 : success, length of label.
* < -1 : fail.
* @desc : read a label from DNS packet buffer.
*/
int DNSQuery::extract_label(Buffer* label, const size_t bfr_off)
{
int len = 0;
int ret_len = 0;
uint16_t offset = 0;
const char* p = (const char*)&_v[bfr_off];
/* Check buffer offset overflow */
if (bfr_off > _i) {
return -1;
}
while (*p) {
/* Bitmask to check for POINTER */
if ((*p & 0xC0) == 0xC0) {
/* If we never used pointer before */
if (!offset) {
ret_len += 2;
}
/* Get POINTER */
memcpy(&offset, p, 2);
offset = ntohs(offset);
offset &= 0x3FFF;
if (offset > _i) {
return -1;
}
/* Jump to POINTER offset */
p = (const char*) &_v[offset];
/* If we never get length before */
} else if (len == 0) {
/* Get LENGTH of message (1 byte) */
len = *p;
p++;
/* If this is the last message LENGTH == 0 */
if (label->len() > 0) {
label->appendc('.');
}
if (!offset) {
ret_len += len + 1;
}
} else {
/* Pick each character by LENGTH */
while (*p && len > 0) {
label->appendc(*p);
--len;
p++;
}
}
}
if (!offset) {
ret_len++;
}
return ret_len;
}
/**
* `_extract_TXT()` will copy `n` octact of data from answer buffer.
* The length of TXT record is defined in RDLENGTH of RR.
*/
int DNSQuery::_extract_TXT(DNS_rr* rr, const size_t offset)
{
const char* p = &_v[offset];
int len = *p;
p++;
rr->_data.copy_raw(p, size_t(len));
return len + 1;
}
/**
@method : DNSQuery::create_answer
@param :
> name : host name.
> type : RR type.
> clas : RR class.
> ttl : time to live value for record.
> data_len : length of data.
> data : data.
> attrs : additional attribute for dns object.
@return :
< 0 : success.
< 1 : fail.
@desc : Create packet of DNS answer for hostname 'hname' with list of
address in 'addrs'.
*/
int DNSQuery::create_answer (const char* name
, uint16_t type, uint16_t clas
, uint32_t ttl
, uint16_t data_len, const char* data
, uint32_t attrs)
{
uint16_t v = 0;
reset (DNSQ_DO_ALL);
_bfr_type = BUFFER_IS_UDP;
_name.copy_raw (name);
_q_type = type;
_q_class = clas;
_ans_ttl_max = ttl;
_attrs = attrs;
set_header (0
, HDR_IS_RESPONSE | OPCODE_QUERY
, 1, (uint16_t) 1, 0, 0);
/* Create question section */
DNS_rr::APPEND_DNS_LABEL (this, name
, (unsigned int) strlen (name));
v = htons (_q_type);
append_bin (&v, 2);
v = htons (_q_class);
append_bin (&v, 2);
/* Create answer section */
DNS_rr* rr_answer = DNS_rr::INIT (name, type, clas, ttl, data_len
, data);
if (!rr_answer) {
return 1;
}
append_raw(rr_answer->v(), rr_answer->len());
_rr_ans.push_tail(rr_answer);
return 0;
}
/**
* @method : DNSQuery::remove_rr_aut
* @desc : remove authority record from buffer.
*
* buffer MUST be extracted before calling this function, using
* extract() method.
*/
void DNSQuery::remove_rr_aut()
{
if (is_empty() || !_rr_aut_p) {
return;
}
if (_n_add > 0 && _rr_add_p) {
int rr_aut_len = (int)(_rr_add_p - _rr_aut_p);
int rr_add_len = (int)(&_v[_i] - _rr_add_p);
memmove((void *)_rr_aut_p, _rr_add_p, size_t(rr_add_len));
_i = _i - size_t(rr_aut_len);
} else {
ssize_t s = _rr_aut_p - _v;
if (s < 0) {
_i = 0;
} else {
_i = size_t(s);
}
}
_rr_aut.reset();
_i++;
_rr_aut_p = NULL;
_v[_i] = 0;
_n_aut = 0;
memset(&_v[DNS_AUT_CNT_POS], 0, 2);
}
/**
* @method : DNSQuery::remove_rr_add
* @desc : remove additional record from buffer.
*
* buffer MUST be extracted before calling this function, using
* extract() method.
*/
void DNSQuery::remove_rr_add()
{
if (is_empty() || !_rr_add_p) {
return;
}
ssize_t s = 0;
s = (_rr_add_p - _v);
if (s < 0) {
_i = 0;
} else {
_i = size_t(s);
}
_rr_add.reset();
_rr_add_p = NULL;
_v[_i] = 0;
_n_add = 0;
memset(&_v[DNS_ADD_CNT_POS], 0, 2);
}
/**
* @method : DNSQuery::set_id
* @param :
* > id : a new identifier for DNS packet.
* @desc : set a new transaction ID for DNS packet buffer.
*/
void DNSQuery::set_id(const int id)
{
if (is_empty()) {
return;
}
char* p = _v;
_id = htons((uint16_t) id);
if (BUFFER_IS_TCP == _bfr_type) {
p = &_v[2];
}
memset(p, 0, 2);
memcpy(p, &_id, 2);
_id = (uint16_t) id;
}
/**
* set_tc will set TrunCated flag on header to `flag` value (0 for not
* truncated, 1 for truncated).
*/
void DNSQuery::set_tc(const int flag)
{
if (is_empty()) {
return;
}
char* p = _v;
if (BUFFER_IS_TCP == _bfr_type) {
p = &_v[2];
}
// Move pointer to flag address.
p = p + 2;
// Get current flag.
memcpy(&_flag, p, 2);
_flag = ntohs(_flag);
// Set flag to on or off.
if (flag == 1) {
_flag = _flag | RTYPE_TC_ON;
} else {
_flag = _flag & RTYPE_TC_OFF;
}
// Set flag in header back.
_flag = htons((uint16_t) flag);
memcpy(p, &_flag, 2);
_flag = ntohs(_flag);
}
/**
* @method : DNSQuery::set_rr_answer_ttl
* @param :
* > ttl : time to live, in seconds. Default to UINT_MAX.
* @desc : set TTL value in each RR Answer record to 'ttl'. DNSQuery
* object must be extracted before calling this function.