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nmap_dns.cc
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nmap_dns.cc
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/***************************************************************************
* nmap_dns.cc -- Handles parallel reverse DNS resolution for target IPs *
* *
***********************IMPORTANT NMAP LICENSE TERMS************************
*
* The Nmap Security Scanner is (C) 1996-2024 Nmap Software LLC ("The Nmap
* Project"). Nmap is also a registered trademark of the Nmap Project.
*
* This program is distributed under the terms of the Nmap Public Source
* License (NPSL). The exact license text applying to a particular Nmap
* release or source code control revision is contained in the LICENSE
* file distributed with that version of Nmap or source code control
* revision. More Nmap copyright/legal information is available from
* https://nmap.org/book/man-legal.html, and further information on the
* NPSL license itself can be found at https://nmap.org/npsl/ . This
* header summarizes some key points from the Nmap license, but is no
* substitute for the actual license text.
*
* Nmap is generally free for end users to download and use themselves,
* including commercial use. It is available from https://nmap.org.
*
* The Nmap license generally prohibits companies from using and
* redistributing Nmap in commercial products, but we sell a special Nmap
* OEM Edition with a more permissive license and special features for
* this purpose. See https://nmap.org/oem/
*
* If you have received a written Nmap license agreement or contract
* stating terms other than these (such as an Nmap OEM license), you may
* choose to use and redistribute Nmap under those terms instead.
*
* The official Nmap Windows builds include the Npcap software
* (https://npcap.com) for packet capture and transmission. It is under
* separate license terms which forbid redistribution without special
* permission. So the official Nmap Windows builds may not be redistributed
* without special permission (such as an Nmap OEM license).
*
* Source is provided to this software because we believe users have a
* right to know exactly what a program is going to do before they run it.
* This also allows you to audit the software for security holes.
*
* Source code also allows you to port Nmap to new platforms, fix bugs, and
* add new features. You are highly encouraged to submit your changes as a
* Github PR or by email to the [email protected] mailing list for possible
* incorporation into the main distribution. Unless you specify otherwise, it
* is understood that you are offering us very broad rights to use your
* submissions as described in the Nmap Public Source License Contributor
* Agreement. This is important because we fund the project by selling licenses
* with various terms, and also because the inability to relicense code has
* caused devastating problems for other Free Software projects (such as KDE
* and NASM).
*
* The free version of Nmap is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Warranties,
* indemnification and commercial support are all available through the
* Npcap OEM program--see https://nmap.org/oem/
*
***************************************************************************/
// mass_dns - Parallel Asynchronous DNS Resolution
//
// One of Nmap's features is to perform reverse DNS queries
// on large number of IP addresses. Nmap supports 2 different
// methods of accomplishing this:
//
// System Resolver (specified using --system-dns):
// Performs sequential getnameinfo() calls on all the IPs.
// As reliable as your system resolver, almost guaranteed
// to be portable, but intolerably slow for scans of hundreds
// or more because the result from each query needs to be
// received before the next one can be sent.
//
// Mass/Async DNS (default):
// Attempts to resolve host names in parallel using a set
// of DNS servers. DNS servers are found here:
//
// --dns-servers <serv1[,serv2],...> (all platforms - overrides everything else)
//
// /etc/resolv.conf (only on unix)
//
// These registry keys: (only on windows)
//
// HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\NameServer
// HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DhcpNameServer
// HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\*\NameServer
// HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\*\DhcpNameServer
//
//
// Also, most systems maintain a file "/etc/hosts" that contains
// IP to hostname mappings. We also try to consult these files. Here
// is where we look for the files:
//
// Unix: /etc/hosts
//
// Windows:
// for 95/98/Me: WINDOWS_DIR\hosts
// for NT/2000/XP Pro: WINDOWS_DIR\system32\drivers\etc\hosts
// for XP Home: WINDOWS_DIR\system32\drivers\etc\hosts
// --see http:https://accs-net.com/hosts/how_to_use_hosts.html
//
//
// Created by Doug Hoyte <doug at hcsw.org> http:https://www.hcsw.org
// DNS Caching and aging added by Eddie Bell [email protected] 2007
// IPv6 and improved DNS cache by Gioacchino Mazzurco <[email protected]> 2015
// TODO:
//
// * Tune performance parameters
//
// * Figure out best way to estimate completion time
// and display it in a ScanProgressMeter
#ifdef WIN32
#include "nmap_winconfig.h"
/* Need DnetName2PcapName */
#include "libnetutil/netutil.h"
#endif
#include "nmap.h"
#include "NmapOps.h"
#include "nmap_dns.h"
#include "nsock.h"
#include "nmap_error.h"
#include "nmap_tty.h"
#include "tcpip.h"
#include "timing.h"
#include "Target.h"
#include <stdlib.h>
#include <limits.h>
#include <list>
extern NmapOps o;
//------------------- Performance Parameters ---------------------
// Algorithm:
//
// A batch of num_requests requests is passed to nmap_mass_dns():
// void nmap_mass_dns(DNS::Request requests[], int num_requests);
//
// mass_dns sends out CAPACITY_MIN of these requests to the DNS
// servers detected, alternating in sequence.
// When a request is fulfilled (either a resolved domain, NXDomain,
// or confirmed ServFail) CAPACITY_UP_STEP is added to the current
// capacity of the server the request was found by.
// When a request times out and retries on the same server,
// the server's capacity is scaled by CAPACITY_MINOR_DOWN_STEP.
// When a request times out and moves to the next server in
// sequence, the server's capacity is scaled by CAPACITY_MAJOR_DOWN_STEP.
// mass_dns tries to maintain the current number of "outstanding
// queries" on each server to that of its current capacity. The
// packet is dropped if it cycles through all specified DNS
// servers.
// Since multiple DNS servers can be specified, different sequences
// of timers are maintained. These are the various retransmission
// intervals for each server before we move on to the next DNS server:
// In milliseconds
// Each row MUST be terminated with -1
static int read_timeouts[][4] = {
{ 4000, 4000, 5000, -1 }, // 1 server
{ 2500, 4000, -1, -1 }, // 2 servers
{ 2500, 3000, -1, -1 }, // 3+ servers
};
#define CAPACITY_MIN 10
#define CAPACITY_MAX 200
#define CAPACITY_UP_STEP 2
#define CAPACITY_MINOR_DOWN_SCALE 0.9
#define CAPACITY_MAJOR_DOWN_SCALE 0.7
// Each request will try to resolve on at most this many servers:
#define SERVERS_TO_TRY 3
//------------------- Other Parameters ---------------------
// How often to display a short debugging summary if debugging is
// specified. Lower numbers means it's displayed more often.
#define SUMMARY_DELAY 50
// Minimum debugging level to display packet trace
#define TRACE_DEBUG_LEVEL 4
// The amount of time we wait for nsock_write() to complete before
// retransmission. This should almost never happen. (in milliseconds)
#define WRITE_TIMEOUT 100
//------------------- Internal Structures ---------------------
struct dns_server;
struct request;
typedef struct sockaddr_storage sockaddr_storage;
struct dns_server {
std::string hostname;
sockaddr_storage addr;
size_t addr_len;
nsock_iod nsd;
int connected;
int reqs_on_wire;
int capacity;
int write_busy;
std::list<request *> to_process;
std::list<request *> in_process;
};
struct request {
DNS::Request *targ;
struct timeval timeout;
int tries;
int servers_tried;
dns_server *first_server;
dns_server *curr_server;
u16 id;
};
/*keeps record of a request going through a particular DNS server
helps in attaining faster lookup based on ID */
struct info{
dns_server *server;
request *tpreq;
};
class HostElem
{
public:
HostElem(const std::string & name_, const sockaddr_storage & ip) :
name(name_), addr(ip), cache_hits(0) {}
~HostElem() {}
/* Ages entries and return true with a cache hit of 0 (the least used) */
static bool isTimeToClean(HostElem he)
{
if(he.cache_hits)
{
he.cache_hits >>= 1;
return false;
}
return true;
}
const std::string name;
const sockaddr_storage addr;
u8 cache_hits;
};
class HostCacheLine : public std::list<HostElem>{};
class HostCache
{
public:
// TODO: avoid hardcode this constant
HostCache() : lines_count(256), hash_mask(lines_count-1),
hosts_storage(new HostCacheLine[lines_count]), elements_count(0)
{}
~HostCache()
{
delete[] hosts_storage;
}
u32 hash(const sockaddr_storage &ip) const
{
u32 ret = 0;
switch (ip.ss_family)
{
case AF_INET:
{
u8 * ipv4 = (u8 *) &((const struct sockaddr_in *) &ip)->sin_addr;
// Shuffle bytes a little so we avoid awful performances in commons
// usages patterns like 10.0.1-255.1 and lines_count 256
ret = ipv4[0] + (ipv4[1]<<3) + (ipv4[2]<<5) + (ipv4[3]<<7);
break;
}
case AF_INET6:
{
const struct sockaddr_in6 * sa6 = (const struct sockaddr_in6 *) &ip;
u32 * ipv6 = (u32 *) sa6->sin6_addr.s6_addr;
ret = ipv6[0] + ipv6[1] + ipv6[2] + ipv6[3];
break;
}
}
return ret & hash_mask;
}
/* Add to the dns cache. If there are too many entries
* we age and remove the least frequently used ones to
* make more space. */
bool add( const sockaddr_storage & ip, const std::string & hname)
{
std::string discard;
if(lookup(ip, discard)) return false;
if(elements_count >= lines_count) prune();
HostElem he(hname, ip);
hosts_storage[hash(ip)].push_back(he);
++elements_count;
return true;
}
u32 prune()
{
u32 original_count = elements_count;
for(u32 i = 0; i < lines_count; ++i)
{
std::list<HostElem>::iterator it = find_if(hosts_storage[i].begin(),
hosts_storage[i].end(),
HostElem::isTimeToClean);
while ( it != hosts_storage[i].end() )
{
it = hosts_storage[i].erase(it);
assert(elements_count > 0);
--elements_count;
}
}
return original_count - elements_count;
}
/* Search for a hostname in the cache and increment
* its cache hit counter if found */
bool lookup(const sockaddr_storage & ip, std::string & name)
{
std::list<HostElem>::iterator hostI;
u32 ip_hash = hash(ip);
for( hostI = hosts_storage[ip_hash].begin();
hostI != hosts_storage[ip_hash].end();
++hostI)
{
if (sockaddr_storage_equal(&hostI->addr, &ip))
{
if(hostI->cache_hits < UCHAR_MAX)
hostI->cache_hits++;
name = hostI->name;
return true;
}
}
return false;
}
protected:
const u32 lines_count;
const u32 hash_mask;
HostCacheLine * const hosts_storage;
u32 elements_count;
};
//------------------- Globals ---------------------
u16 DNS::Factory::progressiveId = get_random_u16();
static std::list<dns_server> servs;
static std::list<request *> new_reqs;
static std::list<request *> deferred_reqs;
static std::map<u16, info> records;
static int total_reqs;
static nsock_pool dnspool=NULL;
/* The DNS cache, not just for entries from /etc/hosts. */
static HostCache host_cache;
static int stat_actual, stat_ok, stat_nx, stat_sf, stat_trans, stat_dropped, stat_cname;
static struct timeval starttv;
static int read_timeout_index;
static int firstrun=1;
static ScanProgressMeter *SPM;
//------------------- Prototypes and macros ---------------------
static void read_evt_handler(nsock_pool, nsock_event, void *);
static void put_dns_packet_on_wire(request *req);
#define ACTION_FINISHED 0
#define ACTION_SYSTEM_RESOLVE 1
#define ACTION_TIMEOUT 2
//------------------- Misc code ---------------------
static void output_summary() {
int tp = stat_ok + stat_nx + stat_dropped;
struct timeval now;
memcpy(&now, nsock_gettimeofday(), sizeof(struct timeval));
if (o.debugging && (tp%SUMMARY_DELAY == 0))
log_write(LOG_STDOUT, "mass_dns: %.2fs %d/%d [#: %lu, OK: %d, NX: %d, DR: %d, SF: %d, TR: %d]\n",
TIMEVAL_FSEC_SUBTRACT(now, starttv),
tp, stat_actual,
(unsigned long) servs.size(), stat_ok, stat_nx, stat_dropped, stat_sf, stat_trans);
}
static void check_capacities(dns_server *tpserv) {
if (tpserv->capacity < CAPACITY_MIN) tpserv->capacity = CAPACITY_MIN;
if (tpserv->capacity > CAPACITY_MAX) tpserv->capacity = CAPACITY_MAX;
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "CAPACITY <%s> = %d\n", tpserv->hostname.c_str(), tpserv->capacity);
}
// Closes all nsis created in connect_dns_servers()
static void close_dns_servers() {
std::list<dns_server>::iterator serverI;
for(serverI = servs.begin(); serverI != servs.end(); serverI++) {
if (serverI->connected) {
nsock_iod_delete(serverI->nsd, NSOCK_PENDING_SILENT);
serverI->connected = 0;
serverI->to_process.clear();
serverI->in_process.clear();
}
}
}
// Puts as many packets on the line as capacity will allow
static void do_possible_writes() {
std::list<dns_server>::iterator servI;
request *tpreq;
for(servI = servs.begin(); servI != servs.end(); servI++) {
if (servI->write_busy == 0 && servI->reqs_on_wire < servI->capacity) {
tpreq = NULL;
if (!servI->to_process.empty()) {
tpreq = servI->to_process.front();
servI->to_process.pop_front();
} else if (!new_reqs.empty()) {
tpreq = new_reqs.front();
assert(tpreq != NULL);
tpreq->first_server = tpreq->curr_server = &*servI;
new_reqs.pop_front();
}
if (tpreq) {
if (o.debugging >= TRACE_DEBUG_LEVEL)
log_write(LOG_STDOUT, "mass_dns: TRANSMITTING for <%s> (server <%s>)\n", tpreq->targ->repr(), servI->hostname.c_str());
stat_trans++;
put_dns_packet_on_wire(tpreq);
}
}
}
}
// nsock write handler
static void write_evt_handler(nsock_pool nsp, nsock_event evt, void *req_v) {
info record;
request *req = (request *) req_v;
req->curr_server->write_busy = 0;
req->curr_server->in_process.push_front(req);
record.tpreq = req;
record.server = req->curr_server;
records[req->id] = record;
do_possible_writes();
}
// Takes a DNS request structure and actually puts it on the wire
// (calls nsock_write()). Does various other tasks like recording
// the time for the timeout.
static void put_dns_packet_on_wire(request *req) {
static const size_t maxlen = 512;
u8 packet[maxlen];
size_t plen=0;
struct timeval now, timeout;
req->id = DNS::Factory::progressiveId;
req->curr_server->write_busy = 1;
req->curr_server->reqs_on_wire++;
DNS::Request &reqt = *req->targ;
switch(reqt.type) {
case DNS::A:
case DNS::AAAA:
plen = DNS::Factory::buildSimpleRequest(reqt.name, reqt.type, packet, maxlen);
break;
case DNS::PTR:
assert(reqt.ssv.size() > 0);
plen = DNS::Factory::buildReverseRequest(reqt.ssv.front(), packet, maxlen);
break;
default:
break;
}
memcpy(&now, nsock_gettimeofday(), sizeof(struct timeval));
TIMEVAL_MSEC_ADD(timeout, now, read_timeouts[read_timeout_index][req->tries]);
memcpy(&req->timeout, &timeout, sizeof(struct timeval));
req->tries++;
nsock_write(dnspool, req->curr_server->nsd, write_evt_handler, WRITE_TIMEOUT, req, reinterpret_cast<const char *>(packet), plen);
}
// Processes DNS packets that have timed out
// Returns time until next read timeout
static int deal_with_timedout_reads() {
std::list<dns_server>::iterator servI;
std::list<dns_server>::iterator servItemp;
std::list<request *>::iterator reqI;
std::list<request *>::iterator nextI;
std::map<u16, info>::iterator infoI;
request *tpreq;
struct timeval now;
int tp, min_timeout = INT_MAX;
memcpy(&now, nsock_gettimeofday(), sizeof(struct timeval));
if (keyWasPressed())
SPM->printStats((double) (stat_ok + stat_nx + stat_dropped) / stat_actual, &now);
for(servI = servs.begin(); servI != servs.end(); servI++) {
nextI = servI->in_process.begin();
if (nextI == servI->in_process.end()) continue;
do {
reqI = nextI++;
tpreq = *reqI;
tp = TIMEVAL_MSEC_SUBTRACT(tpreq->timeout, now);
if (tp > 0 && tp < min_timeout) min_timeout = tp;
if (tp <= 0) {
servI->capacity = (int) (servI->capacity * CAPACITY_MINOR_DOWN_SCALE);
check_capacities(&*servI);
servI->in_process.erase(reqI);
records.erase(tpreq->id);
servI->reqs_on_wire--;
// If we've tried this server enough times, move to the next one
if (read_timeouts[read_timeout_index][tpreq->tries] == -1) {
servI->capacity = (int) (servI->capacity * CAPACITY_MAJOR_DOWN_SCALE);
check_capacities(&*servI);
servItemp = servI;
servItemp++;
if (servItemp == servs.end()) servItemp = servs.begin();
tpreq->curr_server = &*servItemp;
tpreq->tries = 0;
tpreq->servers_tried++;
if (tpreq->curr_server == tpreq->first_server || tpreq->servers_tried == SERVERS_TO_TRY) {
// Either give up on the IP
// or, for maximum reliability, put the server back into processing
// Note it's possible that this will never terminate.
// FIXME: Find a good compromise
// **** We've already tried all servers... give up
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "mass_dns: *DR*OPPING <%s>\n", tpreq->targ->repr());
output_summary();
stat_dropped++;
total_reqs--;
records.erase(tpreq->id);
delete tpreq;
tpreq = NULL;
// **** OR We start at the back of this server's queue
//servItemp->to_process.push_back(tpreq);
} else {
servItemp->to_process.push_back(tpreq);
}
} else {
servI->to_process.push_back(tpreq);
}
}
} while (nextI != servI->in_process.end());
}
if (min_timeout > 500) return 500;
else return min_timeout;
}
static void process_request(int action, info &reqinfo) {
request *tpreq = reqinfo.tpreq;
dns_server *server = reqinfo.server;
switch (action) {
case ACTION_SYSTEM_RESOLVE:
case ACTION_FINISHED:
server->capacity += CAPACITY_UP_STEP;
check_capacities(&*server);
records.erase(tpreq->id);
server->in_process.remove(tpreq);
server->reqs_on_wire--;
total_reqs--;
if (action == ACTION_SYSTEM_RESOLVE) {
deferred_reqs.push_back(tpreq);
}
else {
delete tpreq;
tpreq = NULL;
}
break;
case ACTION_TIMEOUT:
memcpy(&tpreq->timeout, nsock_gettimeofday(), sizeof(struct timeval));
deal_with_timedout_reads();
break;
default:
assert(false);
break;
}
}
// After processing a DNS response, we search through the IPs we're
// looking for and update their results as necessary.
static bool process_result(const std::string &name, const DNS::Record *rr, info &reqinfo, bool already_matched)
{
DNS::Request *reqt = reqinfo.tpreq->targ;
const struct sockaddr_storage *ss = NULL;
const DNS::A_Record *a_rec = NULL;
sockaddr_storage ip;
ip.ss_family = AF_UNSPEC;
switch (reqt->type) {
case DNS::A:
case DNS::AAAA:
if (!already_matched && name != reqt->name) {
return false;
}
a_rec = static_cast<const DNS::A_Record *>(rr);
reqt->ssv.push_back(a_rec->value);
if (o.debugging >= TRACE_DEBUG_LEVEL)
{
log_write(LOG_STDOUT, "mass_dns: OK MATCHED <%s> to <%s>\n",
reqt->name.c_str(),
inet_ntop_ez(&a_rec->value, sizeof(struct sockaddr_storage)));
}
break;
case DNS::PTR:
ss = &reqt->ssv.front();
if (!already_matched) {
if (!DNS::Factory::ptrToIp(name, ip) ||
!sockaddr_storage_equal(&ip, ss)) {
return false;
}
}
reqt->name = static_cast<const DNS::PTR_Record *>(rr)->value;
host_cache.add(*ss, reqt->name);
if (o.debugging >= TRACE_DEBUG_LEVEL)
{
log_write(LOG_STDOUT, "mass_dns: OK MATCHED <%s> to <%s>\n",
inet_ntop_ez(ss, sizeof(struct sockaddr_storage)),
reqt->name.c_str());
}
break;
default:
assert(false);
break;
}
return true;
}
// Nsock read handler. One nsock read for each DNS server exists at each
// time. This function uses various helper functions as defined above.
static void read_evt_handler(nsock_pool nsp, nsock_event evt, void *) {
const u8 *buf;
int buflen;
if (total_reqs >= 1)
nsock_read(nsp, nse_iod(evt), read_evt_handler, -1, NULL);
if (nse_type(evt) != NSE_TYPE_READ || nse_status(evt) != NSE_STATUS_SUCCESS) {
if (o.debugging)
log_write(LOG_STDOUT, "mass_dns: warning: got a %s:%s in %s()\n",
nse_type2str(nse_type(evt)),
nse_status2str(nse_status(evt)), __func__);
return;
}
buf = (unsigned char *) nse_readbuf(evt, &buflen);
DNS::Packet p;
size_t readed_bytes = p.parseFromBuffer(buf, buflen);
if(readed_bytes < DNS::DATA) return;
// We should have 1+ queries:
u16 &f = p.flags;
if(p.queries.empty() || !DNS_HAS_FLAG(f, DNS::RESPONSE) ||
!DNS_HAS_FLAG(f, DNS::OP_STANDARD_QUERY) ||
(f & DNS::ZERO) || DNS_HAS_ERR(f, DNS::ERR_FORMAT) ||
DNS_HAS_ERR(f, DNS::ERR_NOT_IMPLEMENTED) || DNS_HAS_ERR(f, DNS::ERR_REFUSED))
return;
// Check for matching request
std::map<u16, info>::iterator infoI = records.find(p.id);
if (infoI == records.end()) {
return;
}
info &reqinfo = infoI->second;
if (DNS_HAS_ERR(f, DNS::ERR_NAME) || p.answers.empty())
{
process_request(ACTION_FINISHED, reqinfo);
if (o.debugging >= TRACE_DEBUG_LEVEL)
log_write(LOG_STDOUT, "mass_dns: NXDOMAIN <id = %d>\n", p.id);
output_summary();
stat_nx++;
return;
}
if (DNS_HAS_ERR(f, DNS::ERR_SERVFAIL))
{
process_request(ACTION_TIMEOUT, reqinfo);
if (o.debugging >= TRACE_DEBUG_LEVEL)
log_write(LOG_STDOUT, "mass_dns: SERVFAIL <id = %d>\n", p.id);
stat_sf++;
return;
}
bool processing_successful = false;
sockaddr_storage ip;
ip.ss_family = AF_UNSPEC;
std::string alias;
DNS::Request *reqt = reqinfo.tpreq->targ;
for(std::list<DNS::Answer>::const_iterator it = p.answers.begin();
it != p.answers.end(); ++it )
{
const DNS::Answer &a = *it;
if(a.record_class == DNS::CLASS_IN)
{
if (reqt->type == a.record_type) {
processing_successful = process_result(a.name, a.record, reqinfo, a.name == alias);
if (!processing_successful && o.debugging) {
log_write(LOG_STDOUT, "mass_dns: Mismatched record for request %s\n", reqt->repr());
}
}
else if (a.record_type == DNS::CNAME) {
const DNS::CNAME_Record *cname = static_cast<const DNS::CNAME_Record *>(a.record);
if((reqt->type == DNS::PTR && DNS::Factory::ptrToIp(a.name, ip))
|| a.name == reqt->name || (!alias.empty() && a.name == alias))
{
alias = cname->value;
if (o.debugging >= TRACE_DEBUG_LEVEL)
{
log_write(LOG_STDOUT, "mass_dns: CNAME found for <%s> to <%s>\n", a.name.c_str(), alias.c_str());
}
}
}
}
}
if (!processing_successful) {
if (DNS_HAS_FLAG(f, DNS::TRUNCATED)) {
// TODO: TCP fallback, or only use system resolver if user didn't specify --dns-servers
process_request(ACTION_SYSTEM_RESOLVE, reqinfo);
}
else if (!alias.empty()) {
if (o.debugging >= TRACE_DEBUG_LEVEL)
{
log_write(LOG_STDOUT, "mass_dns: CNAME for <%s> not processed.\n", reqt->repr());
}
// TODO: Send a PTR request for alias instead. Meanwhile, we'll just fall
// back to using system resolver. Alternative: report the canonical name
// (alias), but that's not very useful.
process_request(ACTION_SYSTEM_RESOLVE, reqinfo);
}
else {
if (o.debugging >= TRACE_DEBUG_LEVEL) {
log_write(LOG_STDOUT, "mass_dns: Unable to process the response for %s\n", reqt->repr());
}
}
}
else {
output_summary();
stat_ok++;
process_request(ACTION_FINISHED, reqinfo);
}
do_possible_writes();
// Close DNS servers if we're all done so that we kill
// all events and return from nsock_loop immediateley
if (total_reqs == 0)
close_dns_servers();
}
// nsock connect handler - Empty because it doesn't really need to do anything...
static void connect_evt_handler(nsock_pool, nsock_event, void *) {}
// Adds DNS servers to the dns_server list. They can be separated by
// commas or spaces - NOTE this doesn't actually do any connecting!
static void add_dns_server(char *ipaddrs) {
std::list<dns_server>::iterator servI;
const char *hostname;
struct sockaddr_storage addr;
size_t addr_len = sizeof(addr);
for (hostname = strtok(ipaddrs, " ,"); hostname != NULL; hostname = strtok(NULL, " ,")) {
if (resolve(hostname, 0, (struct sockaddr_storage *) &addr, &addr_len,
o.spoofsource ? o.af() : PF_UNSPEC) != 0)
continue;
for(servI = servs.begin(); servI != servs.end(); servI++) {
// Already added!
if (memcmp(&addr, &servI->addr, sizeof(addr)) == 0) break;
}
// If it hasn't already been added, add it!
if (servI == servs.end()) {
dns_server tpserv;
tpserv.hostname = hostname;
memcpy(&tpserv.addr, &addr, sizeof(addr));
tpserv.addr_len = addr_len;
servs.push_front(tpserv);
if (o.debugging) log_write(LOG_STDOUT, "mass_dns: Using DNS server %s\n", hostname);
}
}
}
// Creates a new nsi for each DNS server
static void connect_dns_servers() {
std::list<dns_server>::iterator serverI;
for(serverI = servs.begin(); serverI != servs.end(); serverI++) {
serverI->nsd = nsock_iod_new(dnspool, NULL);
if (o.spoofsource) {
struct sockaddr_storage ss;
size_t sslen;
o.SourceSockAddr(&ss, &sslen);
nsock_iod_set_localaddr(serverI->nsd, &ss, sslen);
}
if (o.ipoptionslen)
nsock_iod_set_ipoptions(serverI->nsd, o.ipoptions, o.ipoptionslen);
serverI->reqs_on_wire = 0;
serverI->capacity = CAPACITY_MIN;
serverI->write_busy = 0;
nsock_connect_udp(dnspool, serverI->nsd, connect_evt_handler, NULL, (struct sockaddr *) &serverI->addr, serverI->addr_len, 53);
nsock_read(dnspool, serverI->nsd, read_evt_handler, -1, NULL);
serverI->connected = 1;
}
}
#ifdef WIN32
static bool interface_is_known_by_guid(const char *guid) {
const struct interface_info *iflist;
int i, n;
iflist = getinterfaces(&n, NULL, 0);
if (iflist == NULL)
return false;
for (i = 0; i < n; i++) {
char pcap_name[1024];
const char *pcap_guid;
if (!DnetName2PcapName(iflist[i].devname, pcap_name, sizeof(pcap_name)))
continue;
pcap_guid = strchr(pcap_name, '{');
if (pcap_guid == NULL)
continue;
if (strcasecmp(guid, pcap_guid) == 0)
return true;
}
return false;
}
// Reads the Windows registry and adds all the nameservers found via the
// add_dns_server() function.
void win32_read_registry() {
HKEY hKey;
HKEY hKey2;
char keybasebuf[2048];
char buf[2048], keyname[2048], *p;
DWORD sz, i;
Snprintf(keybasebuf, sizeof(keybasebuf), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters");
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keybasebuf,
0, KEY_READ, &hKey) != ERROR_SUCCESS) {
if (firstrun) error("mass_dns: warning: Error opening registry to read DNS servers. Try using --system-dns or specify valid servers with --dns-servers");
return;
}
sz = sizeof(buf);
if (RegQueryValueEx(hKey, "NameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
sz = sizeof(buf);
if (RegQueryValueEx(hKey, "DhcpNameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
RegCloseKey(hKey);
Snprintf(keybasebuf, sizeof(keybasebuf), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces");
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keybasebuf,
0, KEY_ENUMERATE_SUB_KEYS, &hKey) == ERROR_SUCCESS) {
for (i=0; sz = sizeof(buf), RegEnumKeyEx(hKey, i, buf, &sz, NULL, NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS; i++) {
// If we don't have pcap, interface_is_known_by_guid will crash. Just use any servers we can find.
if (o.have_pcap && !interface_is_known_by_guid(buf)) {
if (o.debugging > 1)
log_write(LOG_PLAIN, "Interface %s is not known; ignoring its nameservers.\n", buf);
continue;
}
Snprintf(keyname, sizeof(keyname), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces\\%s", buf);
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keyname,
0, KEY_READ, &hKey2) == ERROR_SUCCESS) {
sz = sizeof(buf);
if (RegQueryValueEx(hKey2, "DhcpNameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
sz = sizeof(buf);
if (RegQueryValueEx(hKey2, "NameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
RegCloseKey(hKey2);
}
}
RegCloseKey(hKey);
}
}
#endif // WIN32
// Parses /etc/resolv.conf (unix) and adds all the nameservers found via the
// add_dns_server() function.
static void parse_resolvdotconf() {
FILE *fp;
char buf[2048], *tp;
char fmt[32];
char ipaddr[INET6_ADDRSTRLEN+1];
fp = fopen("/etc/resolv.conf", "r");
if (fp == NULL) {
if (firstrun) gh_perror("mass_dns: warning: Unable to open /etc/resolv.conf. Try using --system-dns or specify valid servers with --dns-servers");
return;
}
Snprintf(fmt, sizeof(fmt), "nameserver %%%us", INET6_ADDRSTRLEN);
while (fgets(buf, sizeof(buf), fp)) {
tp = buf;
// Clip off comments #, \r, \n
while (*tp != '\r' && *tp != '\n' && *tp != '#' && *tp) tp++;
*tp = '\0';
tp = buf;
// Skip any leading whitespace
while (*tp == ' ' || *tp == '\t') tp++;
if (sscanf(tp, fmt, ipaddr) == 1) add_dns_server(ipaddr);
}
fclose(fp);
}
static void parse_etchosts(const char *fname) {
FILE *fp;
char buf[2048], hname[256], ipaddrstr[INET6_ADDRSTRLEN+1], *tp;
sockaddr_storage ia;
fp = fopen(fname, "r");
if (fp == NULL) return; // silently is OK
while (fgets(buf, sizeof(buf), fp)) {