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a91c7f75e49da4f686c3804747bb8947d09e64ff
nmap/nmap_dns.cc
david a91c7f75e4 Fix an infinite loop in nmap_dns.cc. 
This changes the DNS engine to use addto_etchosts to add entries from
/etc/hosts into the DNS cache, rather than just inserting them using
push_front.

The reason for this is that there is a static unsigned variable in
addto_etchosts that keeps track of how many entries there are in the
cache. Using push_front bypassed this variable, allowing the entries in
/etc/hosts to sneak in under the radar. Thus is was possible for the
cache to contain, say, 266 entries when it thought it only had 256.

When the cache size is greater than or equal to 256, addto_etchosts runs
a deletion pass aiming to reduce the number of entries to 126. But the
peculiar loop logic of that function means that more than 256 entries
can be deleted. (How many more depends in part on how many entries there
are in /etc/hosts. There must be at least one for the hang to occur.)
When this happens, the signed counter underflows and becomes large
positive, ~65000. The code empties the cache trying to get the counter
under 127, but it can never happen.

To reproduce the hang, make an /etc/hosts file like this:

1.0.0.1 host-1-1
1.0.0.2 host-1-2
1.0.0.3 host-1-3
1.0.0.4 host-1-4
1.0.0.5 host-1-5
1.0.0.6 host-1-6
1.0.0.7 host-1-7
1.0.0.8 host-1-8
1.0.0.9 host-1-9
1.0.0.10 host-1-10
2.0.0.1 host-2
3.0.0.1 host-3
...
254.0.0.1 host-254
255.0.0.1 host-255

The hang can occur with even one entry in /etc/hosts, but saturating the
cache like this makes the hang less dependent on network conditions.
Then list-scan a netblock that is greater in size than 256 and is dense
in DNS entries (at least 256 entries per 4096 IP addresses). For
example,

nmap -sL scanme.nmap.org/22

works for me currently.
2008-03-14 21:45:41 +00:00

1317 lines
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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) 1996-2008 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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* license Nmap technology such as host discovery, port scanning, OS *
* detection, and version detection. *
* *
* 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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***************************************************************************/
// 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
//------------------- 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_in addr;
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;
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(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_in addr;
size_t addr_len = sizeof(addr);
for (hostname = strtok(ipaddrs, " ,"); hostname != NULL; hostname = strtok(NULL, " ,")) {
if (!resolve(hostname, (struct sockaddr_storage *) &addr, &addr_len, PF_INET)) 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));
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);
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, sizeof(struct sockaddr), 53);
nsock_read(dnspool, s->nsd, read_evt_handler, -1, NULL);
s->connected = 1;
}
}
#ifdef WIN32
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) or the registry (win32) and adds
// all the nameservers found via the add_dns_server() function.
static void parse_resolvdotconf() {
#ifndef WIN32
FILE *fp;
char buf[2048], *tp;
char ipaddr[16];
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;
}
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, "nameserver %15s", ipaddr) == 1) add_dns_server(ipaddr);
}
fclose(fp);
#else
win32_read_registry("CurrentControlSet");
#endif
}
static void parse_etchosts(char *fname) {
FILE *fp;
char buf[2048], hname[256], ipaddrstr[16], *tp;
struct in_addr ia;
host_elem *he;
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 is no space we age and
* remove the least frequently used entries until there
* is 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);
if((total_size--) < HASH_TABLE_SIZE/2)
break;
}
}
}
he = new host_elem;
he->name = strdup(hname);
he->addr = ip;
he->cache_hits = 0;
etchosts[ip % HASH_TABLE_SIZE].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;
for(hostI = etchosts[ip % HASH_TABLE_SIZE].begin(); hostI != etchosts[ip % HASH_TABLE_SIZE].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==NULL?"":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
}
//------------------- 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 (o.mass_dns == false) {
Target *currenths;
struct sockaddr_storage ss;
size_t sslen;
char hostname[MAXHOSTNAMELEN + 1] = "";
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;
return;
}
// If necessary, set up the dns server list from resolv.conf
if (servs.size() == 0) {
if (o.dns_servers) add_dns_server(o.dns_servers);
else parse_resolvdotconf();
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, 5, 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, 5, 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();
}
// 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;
nmap_mass_rdns_core(targets, num_targets);
gettimeofday(&now, NULL);
if (stat_actual > 0) {
if (o.debugging || o.verbose >= 3) {
if (o.mass_dns) {
// #: 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;
}
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