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b55ff2d68f847a50180d40c57a2110174b0d8c32
nmap/nmap_dns.cc
henri b55ff2d68f Don't associate nsock logging info to a nspool. 
Make current loglevel and current log callback global
to the library. Attaching them to the nsock pool doesn't
bring any benefit and prevents from logging activity in
code sections that don't have access to a pool (such as
proxy chain specification parsing).

Updated external calls and nsock tests accordingly.
2015-06-27 08:21:53 +00:00

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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) 1996-2015 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 ("GPL"), BUT ONLY WITH ALL OF THE CLARIFICATIONS *
* AND EXCEPTIONS DESCRIBED HEREIN. 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 (contact sales@nmap.com). Dozens of software *
* vendors already license Nmap technology such as host discovery, port *
* scanning, OS detection, version detection, and the Nmap Scripting *
* Engine. *
* *
* Note that the GPL places important restrictions on "derivative works", *
* yet it does not provide a detailed definition of that term. To avoid *
* misunderstandings, we interpret that term as broadly as copyright law *
* allows. For example, we consider an application to constitute a *
* derivative work for the purpose of this license if it does any of the *
* following with any software or content covered by this license *
* ("Covered Software"): *
* *
* o Integrates source code from Covered Software. *
* *
* o Reads or includes copyrighted data files, such as Nmap's nmap-os-db *
* or nmap-service-probes. *
* *
* o Is designed specifically to execute Covered Software and parse the *
* results (as opposed to typical shell or execution-menu apps, which will *
* execute anything you tell them to). *
* *
* o Includes Covered Software in a proprietary executable installer. The *
* installers produced by InstallShield are an example of this. Including *
* Nmap with other software in compressed or archival form does not *
* trigger this provision, provided appropriate open source decompression *
* or de-archiving software is widely available for no charge. For the *
* purposes of this license, an installer is considered to include Covered *
* Software even if it actually retrieves a copy of Covered Software from *
* another source during runtime (such as by downloading it from the *
* Internet). *
* *
* o Links (statically or dynamically) to a library which does any of the *
* above. *
* *
* o Executes a helper program, module, or script to do any of the above. *
* *
* This list is not exclusive, but is meant to clarify our interpretation *
* of derived works with some common examples. Other people may interpret *
* the plain GPL differently, so we consider this a special exception to *
* the GPL that we apply to Covered Software. Works which meet any of *
* these conditions must conform to all of the terms of this license, *
* particularly including the GPL Section 3 requirements of providing *
* source code and allowing free redistribution of the work as a whole. *
* *
* As another special exception to the GPL terms, Insecure.Com LLC grants *
* permission to link the code of this program with any version of the *
* OpenSSL library which is distributed under a license identical to that *
* listed in the included docs/licenses/OpenSSL.txt file, and distribute *
* linked combinations including the two. *
* *
* Any redistribution of Covered Software, including any derived works, *
* must obey and carry forward all of the terms of this license, including *
* obeying all GPL rules and restrictions. For example, source code of *
* the whole work must be provided and free redistribution must be *
* allowed. All GPL references to "this License", are to be treated as *
* including the terms and conditions of this license text as well. *
* *
* Because this license imposes special exceptions to the GPL, Covered *
* Work may not be combined (even as part of a larger work) with plain GPL *
* software. The terms, conditions, and exceptions of this license must *
* be included as well. This license is incompatible with some other open *
* source licenses as well. In some cases we can relicense portions of *
* Nmap or grant special permissions to use it in other open source *
* software. Please contact fyodor@nmap.org with any such requests. *
* Similarly, we don't incorporate incompatible open source software into *
* Covered Software without special permission from the copyright holders. *
* *
* If you have any questions about the licensing restrictions on using *
* Nmap in other works, are happy to help. As mentioned above, we also *
* offer alternative license to integrate Nmap into proprietary *
* applications and appliances. These contracts have been sold to dozens *
* of software vendors, and generally include a perpetual license as well *
* as providing for priority support and updates. They also fund the *
* continued development of Nmap. Please email sales@nmap.com for further *
* information. *
* *
* If you have received a written license agreement or contract for *
* Covered Software stating terms other than these, you may choose to use *
* and redistribute Covered Software under those terms instead of these. *
* *
* 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 send your changes *
* to the dev@nmap.org mailing list for possible incorporation into the *
* main distribution. By sending these changes to Fyodor or one of the *
* Insecure.Org development mailing lists, or checking them into the Nmap *
* source code repository, it is understood (unless you specify otherwise) *
* that you are offering the Nmap Project (Insecure.Com LLC) the *
* unlimited, non-exclusive right to reuse, modify, and relicense the *
* code. Nmap will always be available Open Source, but this is important *
* because the inability to relicense code has caused devastating problems *
* for other Free Software projects (such as KDE and NASM). We also *
* occasionally relicense the code to third parties as discussed above. *
* If you wish to specify special license conditions of your *
* contributions, just say so when you send them. *
* *
* This program 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. See the Nmap *
* license file for more details (it's in a COPYING file included with *
* Nmap, and also available from https://svn.nmap.org/nmap/COPYING) *
* *
***************************************************************************/
// 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 aging 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 "nmap.h"
#include "NmapOps.h"
#include "nmap_dns.h"
#include "nsock.h"
#include "nmap_error.h"
#include "nmap_tty.h"
#include "timing.h"
#include "Target.h"
#include <stdlib.h>
#include <limits.h>
#include <list>
#include <vector>
#include <algorithm>
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 ---------------------
struct dns_server;
struct request;
struct host_elem;
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 {
Target *targ;
struct timeval timeout;
int tries;
int servers_tried;
dns_server *first_server;
dns_server *curr_server;
u16 id;
};
struct host_elem {
std::string 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 const 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.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();
}
}
}
// 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;
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();
tpreq->first_server = tpreq->curr_server = &*servI;
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() , 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) {
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;
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);
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_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 {
servI->to_process.push_back(tpreq);
}
}
} while (nextI != servI->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;
request *tpreq;
for(servI = servs.begin(); servI != servs.end(); servI++) {
for(reqI = servI->in_process.begin(); reqI != servI->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) {
servI->capacity += CAPACITY_UP_STEP;
check_capacities(&*servI);
if (result) {
tpreq->targ->setHostName(result);
addto_etchosts(tpreq->targ->v4hostip()->s_addr, result);
}
servI->in_process.remove(tpreq);
servI->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 immediateley
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(const unsigned char *buf, char *output, int outputsize) {
int len;
char *p;
p = output;
/* Special case: keep the trailing dot only for the name ".". */
if (buf[0] == 0) {
if (p + 2 > output + outputsize)
return -1;
*p++ = '.';
*p++ = '\0';
return 0;
}
while ((len = buf[0]) != 0) {
/* Add a dot before every component but the first. */
if (p > output) {
if (p + 1 > output + outputsize)
return -1;
*p++ = '.';
}
if (p + len > output + outputsize)
return -1;
memcpy(p, buf + 1, len);
p += len;
buf += 1 + len;
}
if (p + 1 > output + outputsize)
return -1;
*p++ = '\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;
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_rdns: 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) {
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];
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 (strcmp(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 (!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
// 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;
}
Snprintf(fmt, sizeof(fmt), "nameserver %%%us", INET6_ADDRSTRLEN-1);
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);
}
/* 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.name = 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 const char *lookup_etchosts(u32 ip) {
std::list<host_elem>::iterator hostI;
int localIP_Hash = IP_HASH(ip);
for(hostI = etchosts[localIP_Hash].begin(); hostI != etchosts[localIP_Hash].end(); hostI++) {
if (hostI->addr == ip) {
if(hostI->cache_hits < UCHAR_MAX)
hostI->cache_hits++;
return hostI->name.c_str();
}
}
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();
#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;
const char *tpname;
int i;
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
assert((*hostI)->af() == AF_INET);
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 = nsock_pool_new(NULL)) == NULL)
fatal("Unable to create nsock pool in %s()", __func__);
nsock_set_log_function(nmap_nsock_stderr_logger);
nmap_adjust_loglevel(o.packetTrace());
nsock_pool_set_device(dnspool, o.device);
if (o.proxy_chain)
nsock_pool_set_proxychain(dnspool, o.proxy_chain);
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 */
nmap_adjust_loglevel(o.packetTrace());
nsock_loop(dnspool, timeout);
}
SPM->endTask(NULL, NULL);
delete SPM;
close_dns_servers();
nsock_pool_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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