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nmap/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) 1996-2010 Insecure.Com LLC. Nmap is *
* also a registered trademark of Insecure.Com LLC. This program is free *
* software; you may redistribute and/or modify it under the terms of the *
* GNU General Public License as published by the Free Software *
* Foundation; Version 2 with the clarifications and exceptions described *
* below. This guarantees your right to use, modify, and redistribute *
* this software under certain conditions. If you wish to embed Nmap *
* technology into proprietary software, we sell alternative licenses *
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* *
* Note that the GPL places important restrictions on "derived works", yet *
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* misunderstandings, we consider an application to constitute a *
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* This program is distributed in the hope that it will be useful, but *
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* *
***************************************************************************/
// mass_rdns - Parallel Asynchronous Reverse 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://accs-net.com/hosts/how_to_use_hosts.html
//
//
// Created by Doug Hoyte
// doug at hcsw.org
// http://www.hcsw.org
/*
* DNS Caching and ageing added by Eddie Bell ejlbell@gmail.com 2007
*/
// TODO:
//
// * Tune performance parameters
//
// * Figure out best way to estimate completion time
// and display it in a ScanProgressMeter
#ifdef WIN32
#include "nmap_winconfig.h"
#endif
#include <stdlib.h>
#include <limits.h>
#include <list>
#include <vector>
#include <algorithm>
#include "nmap.h"
#include "NmapOps.h"
#include "nmap_dns.h"
#include "nsock.h"
#include "utils.h"
#include "nmap_tty.h"
#include "timing.h"
#include "Target.h"
extern NmapOps o;
//------------------- Performance Parameters ---------------------
// Algorithm:
//
// A batch of num_targets hosts is passed to nmap_mass_rdns():
// void nmap_mass_rdns(Target **targets, int num_targets)
//
// mass_dns sends out CAPACITY_MIN of these hosts 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
// Size of hash table used to hold the hosts from /etc/hosts
#define HASH_TABLE_SIZE 256
// Hash macro for etchosts
#define IP_HASH(x) (ntohl(x)%HASH_TABLE_SIZE)
//------------------- Internal Structures ---------------------
typedef struct dns_server_s dns_server;
typedef struct request_s request;
typedef struct host_elem_s host_elem;
struct dns_server_s {
char *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_s {
Target *targ;
struct timeval timeout;
int tries;
int servers_tried;
dns_server *first_server;
dns_server *curr_server;
u16 id;
};
struct host_elem_s {
char *name;
u32 addr;
u8 cache_hits;
};
//------------------- Globals ---------------------
static std::list<dns_server *> servs;
static std::list<request *> new_reqs;
static std::list<request *> cname_reqs;
static int total_reqs;
static nsock_pool dnspool=NULL;
/* The DNS cache, not just for entries from /etc/hosts. */
static std::list<host_elem *> etchosts[HASH_TABLE_SIZE];
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 u16 id_counter;
static int firstrun=1;
static ScanProgressMeter *SPM;
//------------------- Prototypes and macros ---------------------
static void put_dns_packet_on_wire(request *req);
static char *lookup_etchosts(u32 ip);
static void addto_etchosts(u32 ip, const char *hname);
#define ACTION_FINISHED 0
#define ACTION_CNAME_LIST 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_rdns: %.2fs %d/%d [#: %lu, OK: %d, NX: %d, DR: %d, SF: %d, TR: %d]\n",
TIMEVAL_MSEC_SUBTRACT(now, starttv) / 1000.0,
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, 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) {
nsi_delete((*serverI)->nsd, NSOCK_PENDING_SILENT);
(*serverI)->connected = 0;
(*serverI)->to_process.clear();
(*serverI)->in_process.clear();
}
}
}
// Inserts an integer (endian non-specifically) into a DNS packet.
// Returns number of bytes written
static int add_integer_to_dns_packet(char *packet, int c) {
char tpnum[4];
int tplen;
sprintf(tpnum, "%d", c);
tplen = strlen(tpnum);
packet[0] = (char) tplen;
memcpy(packet+1, tpnum, tplen);
return tplen+1;
}
// Puts as many packets on the line as capacity will allow
static void do_possible_writes() {
std::list<dns_server *>::iterator servI;
dns_server *tpserv;
request *tpreq;
for(servI = servs.begin(); servI != servs.end(); servI++) {
tpserv = *servI;
if (tpserv->write_busy == 0 && tpserv->reqs_on_wire < tpserv->capacity) {
tpreq = NULL;
if (!tpserv->to_process.empty()) {
tpreq = tpserv->to_process.front();
tpserv->to_process.pop_front();
} else if (!new_reqs.empty()) {
tpreq = new_reqs.front();
tpreq->first_server = tpreq->curr_server = tpserv;
new_reqs.pop_front();
}
if (tpreq) {
if (o.debugging >= TRACE_DEBUG_LEVEL)
log_write(LOG_STDOUT, "mass_rdns: TRANSMITTING for <%s> (server <%s>)\n", tpreq->targ->targetipstr() , tpserv->hostname);
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) {
request *req = (request *) req_v;
req->curr_server->write_busy = 0;
req->curr_server->in_process.push_front(req);
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) {
char packet[512];
int plen=0;
u32 ip;
struct timeval now, timeout;
ip = (u32) ntohl(req->targ->v4host().s_addr);
packet[0] = (req->id >> 8) & 0xFF;
packet[1] = req->id & 0xFF;
plen += 2;
memcpy(packet+plen, "\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00", 10);
plen += 10;
plen += add_integer_to_dns_packet(packet+plen, ip & 0xFF);
plen += add_integer_to_dns_packet(packet+plen, (ip>>8) & 0xFF);
plen += add_integer_to_dns_packet(packet+plen, (ip>>16) & 0xFF);
plen += add_integer_to_dns_packet(packet+plen, (ip>>24) & 0xFF);
memcpy(packet+plen, "\x07in-addr\004arpa\x00\x00\x0c\x00\x01", 18);
plen += 18;
req->curr_server->write_busy = 1;
req->curr_server->reqs_on_wire++;
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, 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;
dns_server *tpserv;
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++) {
tpserv = *servI;
nextI = tpserv->in_process.begin();
if (nextI == tpserv->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) {
tpserv->capacity = (int) (tpserv->capacity * CAPACITY_MINOR_DOWN_SCALE);
check_capacities(tpserv);
tpserv->in_process.erase(reqI);
tpserv->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) {
tpserv->capacity = (int) (tpserv->capacity * CAPACITY_MAJOR_DOWN_SCALE);
check_capacities(tpserv);
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_rdns: *DR*OPPING <%s>\n", tpreq->targ->targetipstr());
output_summary();
stat_dropped++;
total_reqs--;
delete tpreq;
// **** 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 {
tpserv->to_process.push_back(tpreq);
}
}
} while (nextI != tpserv->in_process.end());
}
if (min_timeout > 500) return 500;
else return min_timeout;
}
// After processing a DNS response, we search through the IPs we're
// looking for and update their results as necessary.
// Returns non-zero if this matches a query we're looking for
static int process_result(u32 ia, char *result, int action, u16 id) {
std::list<dns_server *>::iterator servI;
std::list<request *>::iterator reqI;
dns_server *tpserv;
request *tpreq;
for(servI = servs.begin(); servI != servs.end(); servI++) {
tpserv = *servI;
for(reqI = tpserv->in_process.begin(); reqI != tpserv->in_process.end(); reqI++) {
tpreq = *reqI;
if (id == tpreq->id) {
if (ia != 0 && tpreq->targ->v4host().s_addr != ia)
continue;
if (action == ACTION_CNAME_LIST || action == ACTION_FINISHED) {
tpserv->capacity += CAPACITY_UP_STEP;
check_capacities(tpserv);
if (result) {
tpreq->targ->setHostName(result);
addto_etchosts(tpreq->targ->v4hostip()->s_addr, result);
}
tpserv->in_process.remove(tpreq);
tpserv->reqs_on_wire--;
total_reqs--;
if (action == ACTION_CNAME_LIST) cname_reqs.push_back(tpreq);
if (action == ACTION_FINISHED) delete tpreq;
} else {
memcpy(&tpreq->timeout, nsock_gettimeofday(), sizeof(struct timeval));
deal_with_timedout_reads();
}
do_possible_writes();
// Close DNS servers if we're all done so that we kill
// all events and return from nsock_loop immediatley
if (total_reqs == 0)
close_dns_servers();
return 1;
}
}
}
return 0;
}
// Gets an IP address from a X.X.X.X.in-addr.arpa DNS
// encoded string inside a packet.
// maxlen is the very maximum length (in total bytes)
// that should be processed
static u32 parse_inaddr_arpa(unsigned char *buf, int maxlen) {
u32 ip=0;
int i, j;
if (maxlen <= 0) return 0;
for (i=0; i<=3; i++) {
if (buf[0] < 1 || buf[0] > 3) return 0;
maxlen -= buf[0] + 1;
if (maxlen <= 0) return 0;
for (j=1; j<=buf[0]; j++) if (!isdigit((int) buf[j])) return 0;
ip |= atoi((char *) buf+1) << (8*i);
buf += buf[0] + 1;
}
if (maxlen < 14) return 0; // length of the following string
if (strcasecmp((char *) buf, "\x07in-addr\004arpa\0")) return 0;
return ntohl(ip);
}
// Turns a DNS packet encoded name (see the RFC) and turns it into
// a normal decimal separated hostname.
// ASSUMES NAME LENGTH/VALIDITY HAS ALREADY BEEN VERIFIED
static int encoded_name_to_normal(unsigned char *buf, char *output, int outputsize){
while (buf[0]) {
if (buf[0] >= outputsize-1) return -1;
memcpy(output, buf+1, buf[0]);
outputsize -= buf[0];
output += buf[0];
buf += buf[0]+1;
if (buf[0]) {
*output++ = '.';
outputsize--;
} else {
*output = '\0';
}
}
return 0;
}
// Takes a pointer to the start of a DNS name inside a packet. It makes
// sure that there is enough space in the name, deals with compression, etc.
static int advance_past_dns_name(u8 *buf, int buflen, int curbuf,
int *nameloc) {
int compression=0;
if (curbuf <= 0 || curbuf >= buflen) return -1;
if ((buf[curbuf] & 0xc0)) {
// Need 2 bytes for compression info
if (curbuf + 1 >= buflen) return -1;
// Compression is OK
compression = curbuf+2;
curbuf = (buf[curbuf+1] + (buf[curbuf] << 8)) & 0x3FFF;
if (curbuf < 0 || curbuf >= buflen) return -1;
}
if (nameloc != NULL) *nameloc = curbuf;
while(buf[curbuf]) {
if (curbuf + buf[curbuf] >= buflen || buf[curbuf] <= 0) return -1;
curbuf += buf[curbuf] + 1;
}
if (compression) return compression;
else return curbuf+1;
}
// 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 *nothing) {
u8 *buf;
int buflen, curbuf=0;
int i, nameloc, rdlen, atype, aclass;
int errcode=0;
int queries, answers;
u16 packet_id;
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);
// Size of header is 12, and we must have additional data as well
if (buflen <= 12) return;
packet_id = buf[1] + (buf[0] << 8);
// Check that this is a response, standard query, and that no truncation was performed
// 0xFA == 11111010 (we're not concerned with AA or RD bits)
if ((buf[2] & 0xFA) != 0x80) return;
// Check that the zero field is all zeros and there is no error condition.
// We don't care if recursion is available or not since we might be querying
// an authoritative DNS server.
if (buf[3] != 0x80 && buf[3] != 0) {
if ((buf[3] & 0xF) == 2) errcode = 2;
else if ((buf[3] & 0xF) == 3) errcode = 3;
else return;
}
queries = buf[5] + (buf[4] << 8);
answers = buf[7] + (buf[6] << 8);
// With a normal resolution, we should have 1+ queries and 1+ answers.
// If the domain doesn't resolve (NXDOMAIN or SERVFAIL) we should have
// 1+ queries and 0 answers:
if (errcode) {
int found;
// NXDomain means we're finished (doesn't exist for sure)
// but SERVFAIL might just mean a server timeout
found = process_result(0, NULL, errcode == 3 ? ACTION_FINISHED : ACTION_TIMEOUT, packet_id);
if (errcode == 2 && found) {
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "mass_rdns: SERVFAIL <id = %d>\n", packet_id);
stat_sf++;
} else if (errcode == 3 && found) {
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "mass_rdns: NXDOMAIN <id = %d>\n", packet_id);
output_summary();
stat_nx++;
}
return;
}
if (queries <= 0 || answers <= 0) return;
curbuf = 12;
// Need to safely skip past QUERY section
for (i=0; i<queries; i++) {
curbuf = advance_past_dns_name(buf, buflen, curbuf, &nameloc);
if (curbuf == -1) return;
// Make sure we have the QTYPE and QCLASS fields
if (curbuf + 4 >= buflen) return;
curbuf += 4;
}
// We're now at the ANSWER section
for (i=0; i<answers; i++) {
curbuf = advance_past_dns_name(buf, buflen, curbuf, &nameloc);
if (curbuf == -1) return;
// Make sure we have the TYPE (2), CLASS (2), TTL (4), and
// RDLENGTH (2) fields
if (curbuf + 10 >= buflen) return;
atype = buf[curbuf+1] + (buf[curbuf+0] << 8);
aclass = buf[curbuf+3] + (buf[curbuf+2] << 8);
rdlen = buf[curbuf+9] + (buf[curbuf+8] << 8);
curbuf += 10;
if (atype == 12 && aclass == 1) {
// TYPE 12 is PTR
struct in_addr ia;
char outbuf[512];
ia.s_addr = parse_inaddr_arpa(buf+nameloc, buflen-nameloc);
if (ia.s_addr == 0) return;
curbuf = advance_past_dns_name(buf, buflen, curbuf, &nameloc);
if (curbuf == -1 || curbuf > buflen) return;
if (encoded_name_to_normal(buf+nameloc, outbuf, sizeof(outbuf)) == -1) return;
if (process_result(ia.s_addr, outbuf, ACTION_FINISHED, packet_id)) {
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "mass_rdns: OK MATCHED <%s> to <%s>\n", inet_ntoa(ia), outbuf);
output_summary();
stat_ok++;
}
} else if (atype == 5 && aclass == 1) {
// TYPE 5 is CNAME
struct in_addr ia;
ia.s_addr = parse_inaddr_arpa(buf+nameloc, buflen-nameloc);
if (ia.s_addr == 0) return;
if (o.debugging >= TRACE_DEBUG_LEVEL) log_write(LOG_STDOUT, "mass_rdns: CNAME found for <%s>\n", inet_ntoa(ia));
process_result(ia.s_addr, NULL, ACTION_CNAME_LIST, packet_id);
} else {
if (rdlen < 0 || rdlen + curbuf >= buflen) return;
curbuf += rdlen;
}
if (curbuf >= buflen) return;
}
}
// nsock connect handler - Empty because it doesn't really need to do anything...
static void connect_evt_handler(nsock_pool nsp, nsock_event evt, void *servers) {
}
// 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;
dns_server *tpserv;
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, 0, (struct sockaddr_storage *) &addr, &addr_len, PF_UNSPEC)) continue;
for(servI = servs.begin(); servI != servs.end(); servI++) {
tpserv = *servI;
// Already added!
if (memcmp(&addr, &tpserv->addr, sizeof(addr)) == 0) break;
}
// If it hasn't already been added, add it!
if (servI == servs.end()) {
tpserv = new dns_server;
tpserv->hostname = strdup(hostname);
memcpy(&tpserv->addr, &addr, sizeof(addr));
tpserv->addr_len = addr_len;
servs.push_front(tpserv);
if (o.debugging) log_write(LOG_STDOUT, "mass_rdns: Using DNS server %s\n", hostname);
}
}
}
void free_dns_servers() {
std::list<dns_server *>::iterator servI;
dns_server *tpserv;
for(servI = servs.begin(); servI != servs.end();servI++){
tpserv = *servI;
if(tpserv){
if(tpserv->hostname)
free(tpserv->hostname);
delete tpserv;
}
}
servs.clear();
}
// Creates a new nsi for each DNS server
static void connect_dns_servers() {
std::list<dns_server *>::iterator serverI;
dns_server *s;
for(serverI = servs.begin(); serverI != servs.end(); serverI++) {
s = *serverI;
s->nsd = nsi_new(dnspool, NULL);
if (o.spoofsource) {
struct sockaddr_storage ss;
size_t sslen;
o.SourceSockAddr(&ss, &sslen);
nsi_set_localaddr(s->nsd, &ss, sslen);
}
if (o.ipoptionslen)
nsi_set_ipoptions(s->nsd, o.ipoptions, o.ipoptionslen);
s->reqs_on_wire = 0;
s->capacity = CAPACITY_MIN;
s->write_busy = 0;
nsock_connect_udp(dnspool, s->nsd, connect_evt_handler, NULL, (struct sockaddr *) &s->addr, s->addr_len, 53);
nsock_read(dnspool, s->nsd, read_evt_handler, -1, NULL);
s->connected = 1;
}
}
#ifdef WIN32
// Reads the Windows registry and adds all the nameservers found via the
// add_dns_server() function.
void win32_read_registry(char *controlset) {
HKEY hKey;
HKEY hKey2;
char keybasebuf[2048];
char buf[2048], keyname[2048], *p;
DWORD sz, i;
Snprintf(keybasebuf, sizeof(keybasebuf), "SYSTEM\\%s\\Services\\Tcpip\\Parameters", controlset);
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\\%s\\Services\\Tcpip\\Parameters\\Interfaces", controlset);
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keybasebuf,
0, KEY_ENUMERATE_SUB_KEYS, &hKey) == ERROR_SUCCESS) {
sz = sizeof(buf);
for (i=0; RegEnumKeyEx(hKey, i, buf, &sz, NULL, NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS; i++) {
Snprintf(keyname, sizeof(keyname), "SYSTEM\\%s\\Services\\Tcpip\\Parameters\\Interfaces\\%s", controlset, 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);
}
sz = sizeof(buf);
}
RegCloseKey(hKey);
}
}
#endif
// 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];
fp = fopen("/etc/resolv.conf", "r");
if (fp == NULL) {
if (firstrun) error("mass_dns: warning: Unable to open /etc/resolv.conf. Try using --system-dns or specify valid servers with --dns-servers");
return;
}
/* Customize a sscanf format to sizeof(ipaddr). */
Snprintf(fmt, sizeof(fmt), "nameserver %%%us", (unsigned int) sizeof(ipaddr));
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[16], *tp;
struct in_addr ia;
fp = fopen(fname, "r");
if (fp == NULL) return; // silently is OK
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, "%15s %255s", ipaddrstr, hname) == 2) {
if (inet_pton(AF_INET, ipaddrstr, &ia))
addto_etchosts(ia.s_addr, hname);
}
}
fclose(fp);
}
void free_etchosts() {
host_elem *he;
std::list<host_elem *>::iterator hi;
int i;
for(i=0; i < HASH_TABLE_SIZE; i++){
for(hi = etchosts[i].begin(); hi != etchosts[i].end(); hi++) {
he = *hi;
if(he) {
free(he->name);
delete he;
}
}
etchosts[i].clear();
}
}
/* Executed when the DNS cache is full, ages entries
* and removes any with a cache hit of 0 (the least used) */
bool remove_and_age(host_elem *host) {
if(host->cache_hits) {
host->cache_hits /=2;
return false;
} else
return true;
}
/* Add to the dns cache. If there are too many entries
* we age and remove the least frequently used ones to
* make more space. */
static void addto_etchosts(u32 ip, const char *hname) {
static u16 total_size = 0;
std::list<host_elem*>::iterator it;
host_elem *he;
int i;
if(lookup_etchosts(ip) != NULL)
return;
while(total_size >= HASH_TABLE_SIZE) {
for(i = 0; i < HASH_TABLE_SIZE; i++) {
while((it = find_if(etchosts[i].begin(), etchosts[i].end(), remove_and_age)) != etchosts[i].end()) {
etchosts[i].erase(it);
/* We don't want total_size to become out of sync with the actual number
of entries. */
assert(total_size > 0);
total_size--;
}
}
}
he = new host_elem;
he->name = strdup(hname);
he->addr = ip;
he->cache_hits = 0;
etchosts[IP_HASH(ip)].push_back(he);
total_size++;
}
/* Search for a hostname in the cache and increment
* its cache hit counter if found */
static char *lookup_etchosts(u32 ip) {
std::list<host_elem *>::iterator hostI;
host_elem *tpelem;
int localIP_Hash = IP_HASH(ip);
for(hostI = etchosts[localIP_Hash].begin(); hostI != etchosts[localIP_Hash].end(); hostI++) {
tpelem = *hostI;
if (tpelem->addr == ip) {
if(tpelem->cache_hits < UCHAR_MAX)
tpelem->cache_hits++;
return tpelem->name;
}
}
return NULL;
}
/* External interface to dns cache */
const char *lookup_cached_host(u32 ip) {
const char *tmp = lookup_etchosts(ip);
return tmp;
}
static void etchosts_init(void) {
static int initialized = 0;
if (initialized) return;
initialized = 1;
#ifdef WIN32
char windows_dir[1024];
char tpbuf[2048];
int has_backslash;
if (!GetWindowsDirectory(windows_dir, sizeof(windows_dir)))
fatal("Failed to determine your windows directory");
// If it has a backslash it's C:\, otherwise something like C:\WINNT
has_backslash = (windows_dir[strlen(windows_dir)-1] == '\\');
// Windows 95/98/Me:
Snprintf(tpbuf, sizeof(tpbuf), "%s%shosts", windows_dir, has_backslash ? "" : "\\");
parse_etchosts(tpbuf);
// Windows NT/2000/XP/2K3:
Snprintf(tpbuf, sizeof(tpbuf), "%s%ssystem32\\drivers\\etc\\hosts", windows_dir, has_backslash ? "" : "\\");
parse_etchosts(tpbuf);
#else
parse_etchosts("/etc/hosts");
#endif
}
/* Initialize the global servs list of DNS servers. If the --dns-servers option
* was given, use the listed servers; otherwise get the list from resolv.conf or
* the Windows registry. If o.mass_dns is false, the list of servers is empty.
* This function caches the results from the first time it is run. */
static void init_servs(void) {
static bool initialized = false;
if (initialized)
return;
initialized = true;
if (!o.mass_dns)
return;
if (o.dns_servers) {
add_dns_server(o.dns_servers);
} else {
#ifndef WIN32
parse_resolvdotconf();
#else
win32_read_registry("CurrentControlSet");
#endif
}
}
//------------------- Main loops ---------------------
// Actual main loop
static void nmap_mass_rdns_core(Target **targets, int num_targets) {
Target **hostI;
std::list<request *>::iterator reqI;
request *tpreq;
int timeout;
char *tpname;
int i;
bool lasttrace = false;
char spmobuf[1024];
// If necessary, set up the dns server list
init_servs();
if (servs.size() == 0 && firstrun) error("mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled. Try using --system-dns or specify valid servers with --dns-servers");
// If necessary, set up the /etc/hosts hashtable
etchosts_init();
total_reqs = 0;
id_counter = get_random_u16();
// Set up the request structure
for(hostI = targets; hostI < targets+num_targets; hostI++) {
if (!((*hostI)->flags & HOST_UP) && !o.resolve_all) continue;
// See if it's in /etc/hosts or cached
tpname = lookup_etchosts((u32) (*hostI)->v4hostip()->s_addr);
if (tpname) {
(*hostI)->setHostName(tpname);
continue;
}
tpreq = new request;
tpreq->targ = *hostI;
tpreq->tries = 0;
tpreq->servers_tried = 0;
tpreq->id = id_counter++;
new_reqs.push_back(tpreq);
stat_actual++;
total_reqs++;
}
if (total_reqs == 0 || servs.size() == 0) return;
// And finally, do it!
if ((dnspool = nsp_new(NULL)) == NULL)
fatal("Unable to create nsock pool in %s()", __func__);
if ((lasttrace = o.packetTrace()))
nsp_settrace(dnspool, NSOCK_TRACE_LEVEL, o.getStartTime());
connect_dns_servers();
cname_reqs.clear();
read_timeout_index = MIN(sizeof(read_timeouts)/sizeof(read_timeouts[0]), servs.size()) - 1;
Snprintf(spmobuf, sizeof(spmobuf), "Parallel DNS resolution of %d host%s.", num_targets, num_targets-1 ? "s" : "");
SPM = new ScanProgressMeter(spmobuf);
while (total_reqs > 0) {
timeout = deal_with_timedout_reads();
do_possible_writes();
if (total_reqs <= 0) break;
/* Because this can change with runtime interaction */
if (o.packetTrace() != lasttrace) {
lasttrace = !lasttrace;
if (lasttrace)
nsp_settrace(dnspool, NSOCK_TRACE_LEVEL, o.getStartTime());
else nsp_settrace(dnspool, 0, o.getStartTime());
}
nsock_loop(dnspool, timeout);
}
SPM->endTask(NULL, NULL);
delete SPM;
close_dns_servers();
nsp_delete(dnspool);
if (cname_reqs.size() && o.debugging)
log_write(LOG_STDOUT, "Performing system-dns for %d domain names that use CNAMEs\n", (int) cname_reqs.size());
if (cname_reqs.size()) {
Snprintf(spmobuf, sizeof(spmobuf), "System CNAME DNS resolution of %u host%s.", (unsigned) cname_reqs.size(), cname_reqs.size()-1 ? "s" : "");
SPM = new ScanProgressMeter(spmobuf);
for(i=0, reqI = cname_reqs.begin(); reqI != cname_reqs.end(); reqI++, i++) {
struct sockaddr_storage ss;
size_t sslen;
char hostname[MAXHOSTNAMELEN + 1] = "";
if (keyWasPressed())
SPM->printStats((double) i / cname_reqs.size(), NULL);
tpreq = *reqI;
if (tpreq->targ->TargetSockAddr(&ss, &sslen) != 0)
fatal("Failed to get target socket address.");
if (getnameinfo((struct sockaddr *)&ss, sslen, hostname,
sizeof(hostname), NULL, 0, NI_NAMEREQD) == 0) {
stat_ok++;
stat_cname++;
tpreq->targ->setHostName(hostname);
}
delete tpreq;
}
SPM->endTask(NULL, NULL);
delete SPM;
}
cname_reqs.clear();
}
static void nmap_system_rdns_core(Target **targets, int num_targets) {
Target **hostI;
Target *currenths;
struct sockaddr_storage ss;
size_t sslen;
char hostname[MAXHOSTNAMELEN + 1] = "";
char spmobuf[1024];
int i;
for(hostI = targets; hostI < targets+num_targets; hostI++) {
currenths = *hostI;
if (((currenths->flags & HOST_UP) || o.resolve_all) && !o.noresolve) stat_actual++;
}
Snprintf(spmobuf, sizeof(spmobuf), "System DNS resolution of %d host%s.", num_targets, num_targets-1 ? "s" : "");
SPM = new ScanProgressMeter(spmobuf);
for(i=0, hostI = targets; hostI < targets+num_targets; hostI++, i++) {
currenths = *hostI;
if (keyWasPressed())
SPM->printStats((double) i / stat_actual, NULL);
if (((currenths->flags & HOST_UP) || o.resolve_all) && !o.noresolve) {
if (currenths->TargetSockAddr(&ss, &sslen) != 0)
fatal("Failed to get target socket address.");
if (getnameinfo((struct sockaddr *)&ss, sslen, hostname,
sizeof(hostname), NULL, 0, NI_NAMEREQD) == 0) {
stat_ok++;
currenths->setHostName(hostname);
}
}
}
SPM->endTask(NULL, NULL);
delete SPM;
}
// Publicly available function. Basically just a wrapper so we
// can record time information, restart statistics, etc.
void nmap_mass_rdns(Target **targets, int num_targets) {
struct timeval now;
gettimeofday(&starttv, NULL);
stat_actual = stat_ok = stat_nx = stat_sf = stat_trans = stat_dropped = stat_cname = 0;
// mass_dns only supports IPv4.
if (o.mass_dns && o.af() == AF_INET)
nmap_mass_rdns_core(targets, num_targets);
else
nmap_system_rdns_core(targets, num_targets);
gettimeofday(&now, NULL);
if (stat_actual > 0) {
if (o.debugging || o.verbose >= 3) {
if (o.mass_dns && o.af() == AF_INET) {
// #: Number of DNS servers used
// OK: Number of fully reverse resolved queries
// NX: Number of confirmations of 'No such reverse domain eXists'
// DR: Dropped IPs (no valid responses were received)
// SF: Number of IPs that got 'Server Failure's
// TR: Total number of transmissions necessary. The number of domains is ideal, higher is worse
log_write(LOG_STDOUT, "DNS resolution of %d IPs took %.2fs. Mode: Async [#: %lu, OK: %d, NX: %d, DR: %d, SF: %d, TR: %d, CN: %d]\n",
stat_actual, TIMEVAL_MSEC_SUBTRACT(now, starttv) / 1000.0,
(unsigned long) servs.size(), stat_ok, stat_nx, stat_dropped, stat_sf, stat_trans, stat_cname);
} else {
log_write(LOG_STDOUT, "DNS resolution of %d IPs took %.2fs. Mode: System [OK: %d, ??: %d]\n",
stat_actual, TIMEVAL_MSEC_SUBTRACT(now, starttv) / 1000.0,
stat_ok, stat_actual - stat_ok);
}
}
}
firstrun=0;
}
// Returns a list of known DNS servers
std::list<std::string> get_dns_servers() {
init_servs();
// If the user said --system-dns (!o.mass_dns), we should never return a list
// of servers.
assert(o.mass_dns || servs.empty());
std::list<dns_server *>::iterator servI;
std::list<std::string> serverList;
for(servI = servs.begin(); servI != servs.end(); servI++) {
serverList.push_back(inet_socktop((struct sockaddr_storage *) &(*servI)->addr));
}
return serverList;
}
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