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idle_scan.cc
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idle_scan.cc
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/***************************************************************************
* idle_scan.cc -- Includes the function specific to "Idle Scan" support *
* (-sI). This is an extraordinarily cool scan type that can allow for *
* completely blind scanning (eg no packets sent to the target from your *
* own IP address) and can also be used to penetrate firewalls and scope *
* out router ACLs. This is one of the "advanced" scans meant for *
* experienced Nmap users. *
* *
***********************IMPORTANT NMAP LICENSE TERMS************************
* *
* The Nmap Security Scanner is (C) 1996-2017 Insecure.Com LLC ("The Nmap *
* Project"). Nmap is also a registered trademark of the Nmap Project. *
* 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, the Nmap Project 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. *
* *
* The Nmap Project has permission to redistribute Npcap, a packet *
* capturing driver and library for the Microsoft Windows platform. *
* Npcap is a separate work with it's own license rather than this Nmap *
* license. Since the Npcap license does not permit redistribution *
* without special permission, our Nmap Windows binary packages which *
* contain Npcap may not be redistributed without special permission. *
* *
* 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 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) *
* *
***************************************************************************/
/* $Id$ */
/* IPv6 fragment ID sequence algorithms. http://seclists.org/nmap-dev/2013/q3/369.
Android 4.1 (Linux 3.0.15) | Per host, incremental (1)
FreeBSD 7.4 | Random
FreeBSD 9.1 | Random
iOS 6.1.2 | Random
Linux 2.6.32 | Per host, incremental (2)
Linux 3.2 | Per host, incremental (1)
Linux 3.8 | Per host, incremental
OpenBSD 4.6 | Random
OpenBSD 5.2 | Random
OS X 10.6.7 | Global, incremental (3)
OS X 10.8.3 | Random
Solaris 11 | Per host, incremental
Windows Server 2003 R2 Standard 64bit, SP2 | Global, incremental
Windows Server 2008 Standard 32bit, SP1 | Global, incremental
Windows Server 2008 R2 Standard 64bit, SP1 | Global, incremental by 2
Windows Server 2012 Standard 64bit | Global, incremental by 2
Windows XP Professional 32bit, SP3 | Global, incremental (4)
Windows Vista Business 64bit, SP1 | Global, incremental
Windows 7 Home Premium 32bit, SP1 | Global, incremental by 2
Windows 7 Ultimate 32bit, SP1 | Global, incremental by 2
Windows 8 Enterprise 32 bit | Global, incremental by 2
*/
#include "libnetutil/npacket.h"
#include "idle_scan.h"
#include "timing.h"
#include "osscan2.h"
#include "nmap.h"
#include "scan_lists.h"
#include "NmapOps.h"
#include "services.h"
#include "Target.h"
#include "nmap_error.h"
#include "output.h"
#include "tcpip.h"
#include "struct_ip.h"
#include <stdio.h>
extern NmapOps o;
#ifdef WIN32
/* from libdnet's intf-win32.c */
extern "C" int g_has_npcap_loopback;
#endif
struct idle_proxy_info {
Target host; /* contains name, IP, source IP, timing info, etc. */
int seqclass; /* IP ID sequence class (IPID_SEQ_* defined in nmap.h) */
u32 latestid; /* The most recent IP ID we have received from the proxy */
u16 probe_port; /* The port we use for probing IP ID infoz */
u16 max_groupsz; /* We won't test groups larger than this ... */
u16 min_groupsz; /* We won't allow the group size to fall below this
level. Affected by --min-parallelism */
double current_groupsz; /* Current group size being used ... depends on
conditions ... won't be higher than
max_groupsz */
int senddelay; /* Delay between sending pr0be SYN packets to target
(in microseconds) */
int max_senddelay; /* Maximum time we are allowed to wait between
sending probes (when we send a bunch in a row.
In microseconds. */
pcap_t *pd; /* A Pcap descriptor which (starting in
initialize_idleproxy) listens for TCP packets from
the probe_port of the proxy box */
int rawsd; /* Socket descriptor for sending probe packets to the proxy */
struct eth_nfo eth; // For when we want to send probes via raw IP instead.
struct eth_nfo *ethptr; // points to eth if filled out, otherwise NULL
};
/* Finds the IPv6 extension header for fragmentation in an IPv6 packet, and returns
* the identification value of the fragmentation header
*/
int ipv6_get_fragment_id(const struct ip6_hdr *ip6, unsigned int len) {
const unsigned char *p, *end;
u8 hdr;
struct ip6_ext_data_fragment *frag_header = NULL;
if (len < sizeof(*ip6))
return -1;
p = (unsigned char *) ip6;
end = p + len;
hdr = ip6->ip6_nxt;
p += sizeof(*ip6);
/* If the first extension header is not the fragmentation, we search our way
* through the extension headers until we find the fragmentation header */
while (p < end && hdr != IP_PROTO_FRAGMENT) {
if (p + 2 > end)
return -1;
hdr = *p;
p += (*(p + 1) + 1) * 8;
}
if (hdr != IP_PROTO_FRAGMENT || (p + 2 + sizeof(ip6_ext_data_fragment)) > end)
return -1;
frag_header = (struct ip6_ext_data_fragment *)( p + 2 );
return (ntohl(frag_header->ident));
}
/* Sends an IP ID probe to the proxy machine and returns the IP ID.
This function handles retransmissions, and returns -1 if it fails.
Proxy timing is adjusted, but proxy->latestid is NOT ADJUSTED --
you'll have to do that yourself. Probes_sent is set to the number
of probe packets sent during execution */
static int ipid_proxy_probe(struct idle_proxy_info *proxy, int *probes_sent,
int *probes_rcvd) {
struct timeval tv_end;
int tries = 0;
int trynum;
int sent = 0, rcvd = 0;
int maxtries = 3; /* The maximum number of tries before we give up */
struct timeval tv_sent[3], rcvdtime;
int ipid = -1;
int to_usec;
unsigned int bytes;
int base_port;
struct ip *ip;
struct tcp_hdr *tcp = NULL;
static u32 seq_base = 0;
static u32 ack = 0;
static int packet_send_count = 0; /* Total # of probes sent by this program -- to ensure that our sequence # always changes */
u32 packetlen = 0;
u8 *ipv6_packet = NULL;
struct sockaddr_storage ss;
size_t sslen;
struct ip6_hdr *ip6 = NULL;
const void *ipv6_data;
u8 hdr;
int res;
if (o.magic_port_set)
base_port = o.magic_port;
else
base_port = o.magic_port + get_random_u8();
if (seq_base == 0)
seq_base = get_random_u32();
if (!ack)
ack = get_random_u32();
do {
gettimeofday(&tv_sent[tries], NULL);
/* Time to send the pr0be!*/
if (o.af() == AF_INET)
send_tcp_raw(proxy->rawsd, proxy->ethptr,
proxy->host.v4sourceip(), proxy->host.v4hostip(),
o.ttl, false,
o.ipoptions, o.ipoptionslen,
base_port + tries, proxy->probe_port,
seq_base + (packet_send_count++ * 500) + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS, TCP_SYN_PROBE_OPTIONS_LEN,
NULL, 0);
else {
ipv6_packet = build_tcp_raw_ipv6(proxy->host.v6sourceip(), proxy->host.v6hostip(),
0x00, 0x0000,
o.ttl,
base_port + tries, proxy->probe_port,
seq_base + (packet_send_count++ * 500) + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS, TCP_SYN_PROBE_OPTIONS_LEN,
NULL, 0,
&packetlen);
proxy->host.TargetSockAddr(&ss, &sslen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send IPv6 packet");
free(ipv6_packet);
}
sent++;
tries++;
/* Now it is time to wait for the response ... */
to_usec = proxy->host.to.timeout;
gettimeofday(&tv_end, NULL);
while ((ipid == -1 || sent > rcvd) && to_usec > 0) {
to_usec = proxy->host.to.timeout - TIMEVAL_SUBTRACT(tv_end, tv_sent[tries - 1]);
if (to_usec < 0)
to_usec = 0; // Final no-block poll
ip = (struct ip *) readip_pcap(proxy->pd, &bytes, to_usec, &rcvdtime, NULL, true);
gettimeofday(&tv_end, NULL);
if (ip) {
if (o.af() == AF_INET) {
if (bytes < (4 * ip->ip_hl) + 14U)
continue;
if (ip->ip_p == IPPROTO_TCP)
tcp = ((struct tcp_hdr *) (((char *) ip) + 4 * ip->ip_hl));
} else if (o.af() == AF_INET6) {
if (ip->ip_v != 6) {
error("IPv6 packet with a version field != 6 received");
} else {
ip6 = (struct ip6_hdr *) ip;
ipv6_data = ipv6_get_data(ip6, &packetlen, &hdr);
if (hdr == IPPROTO_TCP && ipv6_data != NULL) {
tcp = (struct tcp_hdr *) ipv6_data;
}
}
}
if (tcp) {
if (ntohs(tcp->th_dport) < base_port || ntohs(tcp->th_dport) - base_port >= tries || ntohs(tcp->th_sport) != proxy->probe_port || ((tcp->th_flags & TH_RST) == 0)) {
if (ntohs(tcp->th_dport) > o.magic_port && ntohs(tcp->th_dport) < (o.magic_port + 260)) {
if (o.debugging) {
error("Received IP ID zombie probe response which probably came from an earlier prober instance ... increasing rttvar from %d to %d",
proxy->host.to.rttvar, (int) (proxy->host.to.rttvar * 1.2));
}
proxy->host.to.rttvar = (int) (proxy->host.to.rttvar * 1.2);
rcvd++;
} else if (o.debugging > 1) {
char straddr[INET6_ADDRSTRLEN];
if (o.af() == AF_INET)
inet_ntop(AF_INET, &(ip->ip_src), straddr, sizeof(straddr));
else if (o.af() == AF_INET6)
inet_ntop(AF_INET6, &(ip6->ip6_src), straddr, sizeof(straddr));
error("Received unexpected response packet from %s during IP ID zombie probing:", straddr);
readtcppacket((unsigned char *) ip, MIN(ntohs(ip->ip_len), bytes));
}
continue;
}
trynum = ntohs(tcp->th_dport) - base_port;
rcvd++;
if (o.af() == AF_INET)
ipid = ntohs(ip->ip_id);
else if (o.af() == AF_INET6)
ipid = ipv6_get_fragment_id(ip6, bytes);
adjust_timeouts2(&(tv_sent[trynum]), &rcvdtime, &(proxy->host.to));
}
}
}
} while (ipid == -1 && tries < maxtries);
if (probes_sent)
*probes_sent = sent;
if (probes_rcvd)
*probes_rcvd = rcvd;
return ipid;
}
static u16 byteswap_u16(u16 h) {
return ((h&0xff) << 8) | ((h>>8)&0xff);
}
/* Returns the number of increments between an early IP ID and a later
one, assuming the given IP ID Sequencing class. Returns -1 if the
distance cannot be determined */
static int ipid_distance(int seqclass , u32 startid, u32 endid) {
if (seqclass == IPID_SEQ_INCR)
return endid - startid;
if (seqclass == IPID_SEQ_BROKEN_INCR) {
/* Convert to network byte order */
startid = byteswap_u16((u16) startid);
endid = byteswap_u16((u16) endid);
return endid - startid;
}
if (seqclass == IPID_SEQ_INCR_BY_2) {
return (endid - startid)/2;
}
return -1;
}
static void initialize_proxy_struct(struct idle_proxy_info *proxy) {
proxy->seqclass = proxy->latestid = proxy->probe_port = 0;
proxy->max_groupsz = proxy->min_groupsz = 0;
proxy->current_groupsz = 0;
proxy->senddelay = 0;
proxy->max_senddelay = 0;
proxy->pd = NULL;
proxy->rawsd = -1;
proxy->ethptr = NULL;
}
/* Forces the permanent use of the IPv6 extension header for fragmentation in each IPv6 packet sent from
* the idle host to the target or the attacker
* This is achieved by first sending a ping, and afterwards an ICMPv6 Packet Too Big message
* which states that the response from the ping was too big, our MTU is smaller than the IPv6 minimum MTU */
static void ipv6_force_fragmentation(struct idle_proxy_info *proxy, Target *target) {
int hardtimeout = 9000000; /* Generally don't wait more than 9 secs total */
char filter[512]; /* Libpcap filter string */
struct ip *ip;
/* The maximum data size we can create without fragmenting, considering that the headers also need place */
char data[IP6_MTU_MIN - IPv6_HEADER_LEN - ETH_HDR_LEN - ICMPv6_MIN_HEADER_LEN];
unsigned int datalen, bytes;
const unsigned int proxy_reply_timeout = 2000;
const void *rdata; //the data received in the echo response
struct timeval tmptv, rcvdtime, ipv6_packet_send_time;
struct abstract_ip_hdr hdr;
bool response_received = false;
struct icmpv6_hdr *icmp6_header;
u8 *ipv6_packet = NULL;
u32 packetlen = 0;
u16 pingid = 0;
u16 seq = 0;
struct sockaddr_storage ss;
size_t sslen;
int res;
assert(proxy);
/* First, we force the proxy to provide us with a fragmentation header in each packet
by sending an ping and afterwards an ICMPv6 Packet Too Big */
memset(data,'A', sizeof(data));
pingid = get_random_u16();
seq = get_random_u16();
/* pcap, to get the answer. Max size here is the IPv6 minimum MTU */
if ((proxy->pd = my_pcap_open_live(proxy->host.deviceName(), IP6_MTU_MIN, (o.spoofsource) ? 1 : 0, 50)) == NULL)
fatal("%s", PCAP_OPEN_ERRMSG);
Snprintf(filter, sizeof(filter), "icmp6 and src host %s and dst host %s", proxy->host.targetipstr(), proxy->host.sourceipstr());
if (o.debugging)
log_write(LOG_STDOUT, "Packet capture filter (device %s): %s\n", proxy->host.deviceFullName(), filter);
/* Make a ping that is in total 1280 byte long and send it */
proxy->host.TargetSockAddr(&ss, &sslen);
ipv6_packet = build_icmpv6_raw(proxy->host.v6sourceip(), proxy->host.v6hostip(), 0x00, 0x0000, o.ttl, seq , pingid, ICMPV6_ECHO, 0x00, data, sizeof(data) , &packetlen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send ICMPv6 Echo Request to the idle host");
free(ipv6_packet);
gettimeofday(&ipv6_packet_send_time, NULL);
/* Now let's wait for the answer */
while (!response_received) {
gettimeofday(&tmptv, NULL);
ip = (struct ip *) readip_pcap(proxy->pd, &bytes, proxy_reply_timeout, &rcvdtime, NULL, true);
if (!ip) {
if (TIMEVAL_SUBTRACT(tmptv, ipv6_packet_send_time) >= hardtimeout) {
fatal("Idle scan zombie %s (%s) port %hu cannot be used because it has not returned any of our ICMPv6 Echo Requests -- perhaps it is down or firewalled.",
proxy->host.HostName(), proxy->host.targetipstr(),
proxy->probe_port);
}
continue;
}
datalen = bytes;
rdata = ip_get_data(ip, &datalen, &hdr);
if (hdr.version == 6 && hdr.proto == IPPROTO_ICMPV6) {
icmp6_header = (struct icmpv6_hdr *) rdata;
if (icmp6_header->icmpv6_type == ICMPV6_ECHOREPLY) {
const struct icmpv6_msg_echo *echo;
echo = (struct icmpv6_msg_echo *) ((u8 *) icmp6_header + sizeof(*icmp6_header));
if (ntohs(echo->icmpv6_id) == pingid && ntohs(echo->icmpv6_seq) == seq)
response_received=true;
}
}
}
if (proxy->pd)
pcap_close(proxy->pd);
/* Now we can tell the idle host that its reply was too big, we want it smaller than the IPV6 minimum MTU */
/* the data contains first the MTU we want, and then the received IPv6 package */
*(uint32_t *)&data = ntohl(IP6_MTU_MIN - 2);
memcpy(&data[4], ip, sizeof(data)-4);
ipv6_packet = build_icmpv6_raw(proxy->host.v6sourceip(), proxy->host.v6hostip(), 0x00, 0x0000, o.ttl, 0x00 , 0x00, 0x02, 0x00, data, sizeof(data) , &packetlen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send spoofed ICMPv6 Echo Request to the idle host");
free(ipv6_packet);
/* Now we do the same in the name of the target */
/* No pcap this time, we won't receive the answer */
memset(data,'A', sizeof(data));
pingid = get_random_u16();
seq = get_random_u16();
ipv6_packet = build_icmpv6_raw(target->v6hostip(), proxy->host.v6hostip(), 0x00, 0x0000, o.ttl, seq , pingid, ICMPV6_ECHO, 0x00, data, sizeof(data) , &packetlen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send ICMPv6 Echo Request to the idle host");
free(ipv6_packet);
/* Now we guess what answer the decoy host sent to the target, so that we can piggyback this on the ICMPV6 Packet too Big message */
ipv6_packet = build_icmpv6_raw(proxy->host.v6hostip(), target->v6hostip(), 0x00, 0x0000, o.ttl, seq , pingid, ICMPV6_ECHOREPLY, 0x00, data, sizeof(data) , &packetlen);
*(uint32_t *)&data = ntohl(IP6_MTU_MIN - 2);
memcpy(&data[4], ipv6_packet, sizeof(data)-4);
free(ipv6_packet);
ipv6_packet = build_icmpv6_raw(target->v6hostip(), proxy->host.v6hostip(), 0x00, 0x0000, o.ttl, 0x00 , 0x00, 0x02, 0x00, data, sizeof(data) , &packetlen);
/* give the decoy host time to reply to the target */
usleep(10000);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send ICMPv6 PTB to the idle host");
free(ipv6_packet);
}
/* takes a proxy name/IP, resolves it if necessary, tests it for IP ID
suitability, and fills out an idle_proxy_info structure. If the
proxy is determined to be unsuitable, the function whines and exits
the program */
#define NUM_IPID_PROBES 6
static void initialize_idleproxy(struct idle_proxy_info *proxy, char *proxyName,
Target *target, const struct scan_lists *ports) {
unsigned int probes_sent = 0, probes_returned = 0;
int hardtimeout = 9000000; /* Generally don't wait more than 9 secs total */
unsigned int bytes, to_usec;
int timedout = 0;
char *p, *q = NULL, *r;
char *endptr = NULL;
int seq_response_num;
int newipid;
unsigned int i;
char filter[512]; /* Libpcap filter string */
char name[FQDN_LEN + 1];
struct sockaddr_storage ss;
size_t sslen;
u32 sequence_base;
u32 ack = 0;
struct timeval probe_send_times[NUM_IPID_PROBES], tmptv, rcvdtime;
u32 lastipid = 0;
struct ip *ip;
struct tcp_hdr *tcp;
int distance;
u32 ipids[NUM_IPID_PROBES];
u8 probe_returned[NUM_IPID_PROBES];
struct route_nfo rnfo;
assert(proxyName);
u8 *ipv6_packet = NULL;
u32 packetlen = 0;
const struct ip6_hdr *ip6;
u8 ip6hdr;
const void *ip6data;
bool retried_forcing_fragmentation = false;
assert(proxy);
assert(proxyName);
int res;
ack = get_random_u32();
for (i = 0; i < NUM_IPID_PROBES; i++)
probe_returned[i] = 0;
initialize_proxy_struct(proxy);
initialize_timeout_info(&proxy->host.to);
proxy->min_groupsz = o.min_parallelism ? o.min_parallelism : 4;
proxy->max_groupsz = MAX(proxy->min_groupsz, o.max_parallelism ? o.max_parallelism : 100);
proxy->max_senddelay = 100000;
/* If we have an IPv6 address, we specify the port with [address]:port */
if (o.af() == AF_INET)
q = strchr(proxyName, ':');
else if (o.af() == AF_INET6) {
r = strstr(proxyName, "]:");
if (r != NULL)
q = strchr(r, ':');
else
q = NULL;
}
/* If we have a : in IPv4 or [] in IPv6, we strip them off */
if (o.af() == AF_INET && q != NULL ) {
/* I'm lazy, using a size_t we already had around */
sslen = MIN(strcspn(proxyName,":"), sizeof(name) - 1);
strncpy(name, proxyName, sslen);
/* Ensure NULL termination */
name[sslen] = '\0';
}
else if (o.af() == AF_INET6 && strchr(proxyName, '[') != NULL && strchr(proxyName, ']') != NULL) {
sslen = MIN(strcspn(proxyName,"]") - strcspn(proxyName, "[") - 1, sizeof(name) - 1);
strncpy(name, strchr(proxyName, '[') + 1, sslen);
name[sslen] = '\0';
}
else
strncpy(name, proxyName, sizeof(name));
if (q) {
q++;
proxy->probe_port = strtoul(q, &endptr, 10);
if (*q == 0 || !endptr || *endptr != '\0' || !proxy->probe_port) {
fatal("Invalid port number given in IP ID zombie specification: %s", proxyName);
}
} else {
if (ports->syn_ping_count > 0) {
proxy->probe_port = ports->syn_ping_ports[0];
} else if (ports->ack_ping_count > 0) {
proxy->probe_port = ports->ack_ping_ports[0];
} else {
u16 *ports;
int count;
getpts_simple(DEFAULT_TCP_PROBE_PORT_SPEC, SCAN_TCP_PORT, &ports, &count);
assert(count > 0);
proxy->probe_port = ports[0];
free(ports);
}
}
proxy->host.setHostName(name);
int rc = resolve(name, 0, &ss, &sslen, o.pf());
if (rc != 0) {
fatal("Could not resolve idle scan zombie host \"%s\": %s", name, gai_strerror(rc));
}
proxy->host.setTargetSockAddr(&ss, sslen);
/* Lets figure out the appropriate source address to use when sending
the probes */
proxy->host.TargetSockAddr(&ss, &sslen);
if (!nmap_route_dst(&ss, &rnfo))
fatal("Unable to find appropriate source address and device interface to use when sending packets to %s", proxyName);
if (o.spoofsource) {
o.SourceSockAddr(&ss, &sslen);
proxy->host.setSourceSockAddr(&ss, sslen);
proxy->host.setDeviceNames(o.device, o.device);
} else {
proxy->host.setDeviceNames(rnfo.ii.devname, rnfo.ii.devfullname);
proxy->host.setSourceSockAddr(&rnfo.srcaddr, sizeof(rnfo.srcaddr));
}
if (rnfo.direct_connect) {
proxy->host.setDirectlyConnected(true);
} else {
proxy->host.setDirectlyConnected(false);
proxy->host.setNextHop(&rnfo.nexthop, sizeof(rnfo.nexthop));
}
proxy->host.setIfType(rnfo.ii.device_type);
if (rnfo.ii.device_type == devt_ethernet)
proxy->host.setSrcMACAddress(rnfo.ii.mac);
/* Now lets send some probes to check IP ID algorithm ... */
/* First we need a raw socket ... */
if ((o.sendpref & PACKET_SEND_ETH) && (proxy->host.ifType() == devt_ethernet
#ifdef WIN32
|| (g_has_npcap_loopback && proxy->host.ifType() == devt_loopback)
#endif
)) {
if (!setTargetNextHopMAC(&proxy->host))
fatal("%s: Failed to determine dst MAC address for Idle proxy", __func__);
memcpy(proxy->eth.srcmac, proxy->host.SrcMACAddress(), 6);
memcpy(proxy->eth.dstmac, proxy->host.NextHopMACAddress(), 6);
proxy->eth.ethsd = eth_open_cached(proxy->host.deviceName());
if (proxy->eth.ethsd == NULL)
fatal("%s: Failed to open ethernet device (%s)", __func__, proxy->host.deviceName());
proxy->rawsd = -1;
proxy->ethptr = &proxy->eth;
} else {
#ifdef WIN32
win32_fatal_raw_sockets(proxy->host.deviceName());
#endif
proxy->rawsd = nmap_raw_socket();
if (proxy->rawsd < 0)
pfatal("socket troubles in %s", __func__);
unblock_socket(proxy->rawsd);
proxy->eth.ethsd = NULL;
proxy->ethptr = NULL;
}
if (proxy->host.af() == AF_INET6)
ipv6_force_fragmentation(proxy, target);
/* Now for the pcap opening nonsense ...
Snaplen will be the IPv6 minimum MTU of 1280, because an IPv6 packet
may have any number of extension header up to the minimal IPv6 MTU */
if ((proxy->pd = my_pcap_open_live(proxy->host.deviceName(), IP6_MTU_MIN, (o.spoofsource) ? 1 : 0, 50)) == NULL)
fatal("%s", PCAP_OPEN_ERRMSG);
p = (char *) proxy->host.targetipstr();
q = (char *) proxy->host.sourceipstr();
/* libpcap doesn't find the source port in IPv6 if there is an extension header. So we check for this later in the tcp header. */
Snprintf(filter, sizeof(filter), "tcp and src host %s and dst host %s", p, q);
set_pcap_filter(proxy->host.deviceFullName(), proxy->pd, filter);
if (o.debugging)
log_write(LOG_STDOUT, "Packet capture filter (device %s): %s\n", proxy->host.deviceFullName(), filter);
/* Windows nonsense -- I am not sure why this is needed, but I should
get rid of it at sometime */
sequence_base = get_random_u32();
/* Yahoo! It is finally time to send our probes! */
while (probes_sent < NUM_IPID_PROBES) {
if (o.scan_delay)
enforce_scan_delay(NULL);
else if (probes_sent != 0)
usleep(30000);
/* TH_SYN|TH_ACK is what the proxy will really be receiving from
the target, and is more likely to get through firewalls. But
TH_SYN allows us to get a nonzero ACK back so we can associate
a response with the exact request for timing purposes. So I
think I'll use TH_SYN, although it is a tough call. */
/* We can't use decoys 'cause that would screw up the IP IDs */
if (o.af() == AF_INET)
send_tcp_raw(proxy->rawsd, proxy->ethptr,
proxy->host.v4sourceip(), proxy->host.v4hostip(),
o.ttl, false,
o.ipoptions, o.ipoptionslen,
o.magic_port + probes_sent + 1, proxy->probe_port,
sequence_base + probes_sent + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS, TCP_SYN_PROBE_OPTIONS_LEN,
NULL, 0);
else if (o.af() == AF_INET6) {
ipv6_packet = build_tcp_raw_ipv6(proxy->host.v6sourceip(), proxy->host.v6hostip(),
0x00, 0x0000,
o.ttl,
o.magic_port + probes_sent + 1, proxy->probe_port,
sequence_base + probes_sent + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS, TCP_SYN_PROBE_OPTIONS_LEN,
NULL, 0,
&packetlen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send IPv6 packet");
free(ipv6_packet);
}
gettimeofday(&probe_send_times[probes_sent], NULL);
probes_sent++;
/* Time to collect any replies */
while (probes_returned < probes_sent && !timedout) {
to_usec = (probes_sent == NUM_IPID_PROBES) ? hardtimeout : 1000;
ip = (struct ip *) readip_pcap(proxy->pd, &bytes, to_usec, &rcvdtime, NULL, true);
gettimeofday(&tmptv, NULL);
if (!ip) {
if (probes_sent < NUM_IPID_PROBES)
break;
if (TIMEVAL_SUBTRACT(tmptv, probe_send_times[probes_sent - 1]) >= hardtimeout) {
timedout = 1;
}
continue;
} else if (TIMEVAL_SUBTRACT(tmptv, probe_send_times[probes_sent - 1]) >= hardtimeout) {
timedout = 1;
}
if (o.af() == AF_INET) {
if (ip->ip_v != 4) {
error("Received a packet with version field != 4");
continue;
}
if (lastipid != 0 && ip->ip_id == lastipid) {
continue; /* probably a duplicate */
}
lastipid = ip->ip_id;
if (bytes < (4 * ip->ip_hl) + 14U)
continue;
if (ip->ip_p == IPPROTO_TCP) {
tcp = ((struct tcp_hdr *) (((char *) ip) + 4 * ip->ip_hl));
/* Checking now for the source port, which we were not able to do in the libpcap filter */
if (ntohs(tcp->th_sport) != proxy->probe_port) {
continue;
}
if (ntohs(tcp->th_dport) < (o.magic_port + 1) || ntohs(tcp->th_dport) - o.magic_port > NUM_IPID_PROBES || ((tcp->th_flags & TH_RST) == 0)) {
if (o.debugging > 1)
error("Received unexpected response packet from %s during initial IP ID zombie testing", inet_ntoa(ip->ip_src));
continue;
}
seq_response_num = probes_returned;
/* The stuff below only works when we send SYN packets instead of
SYN|ACK, but then are slightly less stealthy and have less chance
of sneaking through the firewall. Plus SYN|ACK is what they will
be receiving back from the target */
probes_returned++;
ipids[seq_response_num] = ntohs(ip->ip_id);
probe_returned[seq_response_num] = 1;
adjust_timeouts2(&probe_send_times[seq_response_num], &rcvdtime, &(proxy->host.to));
}
} else if (o.af() == AF_INET6) {
if (ip->ip_v != 6) {
error("Received a packet with version field != 6");
continue;
} else {
ip6 = (struct ip6_hdr *) ip;
newipid = ipv6_get_fragment_id(ip6, bytes);
if (newipid < 0 ) {
/* ok, the idle host does not seem to append the extension header for fragmentation. Let's try this once more,
* maybe the idle host just adjusted its Path MTU. If we keep on having the problem, we quit */
if (!retried_forcing_fragmentation) {
ipv6_force_fragmentation(proxy, target);
retried_forcing_fragmentation = true;
} else
fatal("IPv6 packet without fragmentation header received - issues with the zombie?");
}
/* now that the additional ipv6 stuff is done, we do as for IPv4 */
if (lastipid != 0 && newipid == (int)lastipid) {
continue; /* probably a duplicate */
}
lastipid = newipid;
ip6data = ipv6_get_data(ip6, &packetlen, &ip6hdr);
if (ip6hdr == IPPROTO_TCP && ip6data != NULL) {
tcp = (struct tcp_hdr *) ip6data;
/* Checking now for the source port, which we were not able to do in the libpcap filter */
if (ntohs(tcp->th_sport) != proxy->probe_port) {
continue;
}
}else
{
error("Malformed packet received");
continue;
}
if (ntohs(tcp->th_dport) < (o.magic_port + 1) || ntohs(tcp->th_dport) - o.magic_port > NUM_IPID_PROBES || ((tcp->th_flags & TH_RST) == 0)) {
if (o.debugging > 1)
error("Received unexpected response packet from %s during initial IP ID zombie testing", inet_ntoa(ip->ip_src));
continue;
}
seq_response_num = probes_returned;
/* The stuff below only works when we send SYN packets instead of
SYN|ACK, but then are slightly less stealthy and have less chance
of sneaking through the firewall. Plus SYN|ACK is what they will
be receiving back from the target */
probes_returned++;
ipids[seq_response_num] = newipid;
probe_returned[seq_response_num] = 1;
adjust_timeouts2(&probe_send_times[seq_response_num], &rcvdtime, &(proxy->host.to));
}
}
}
}
/* Yeah! We're done sending/receiving probes ... now lets ensure all of our responses are adjacent in the array */
for (i = 0, probes_returned = 0; i < NUM_IPID_PROBES; i++) {
if (probe_returned[i]) {
if (i > probes_returned)
ipids[probes_returned] = ipids[i];
probes_returned++;
}
}
if (probes_returned == 0)
fatal("Idle scan zombie %s (%s) port %hu cannot be used because it has not returned any of our probes -- perhaps it is down or firewalled.",
proxy->host.HostName(), proxy->host.targetipstr(),
proxy->probe_port);
if (o.af() == AF_INET)
proxy->seqclass = get_ipid_sequence_16(probes_returned, ipids, 0);
else
proxy->seqclass = get_ipid_sequence_32(probes_returned, ipids, 0);
switch (proxy->seqclass) {
case IPID_SEQ_INCR:
case IPID_SEQ_INCR_BY_2:
case IPID_SEQ_BROKEN_INCR:
log_write(LOG_PLAIN, "Idle scan using zombie %s (%s:%hu); Class: %s\n", proxy->host.HostName(), proxy->host.targetipstr(), proxy->probe_port, ipidclass2ascii(proxy->seqclass));
break;
default:
fatal("Idle scan zombie %s (%s) port %hu cannot be used because IP ID sequence class is: %s. Try another proxy.", proxy->host.HostName(), proxy->host.targetipstr(), proxy->probe_port, ipidclass2ascii(proxy->seqclass));
}
proxy->latestid = ipids[probes_returned - 1];
proxy->current_groupsz = MIN(proxy->max_groupsz, 30);
if (probes_returned < NUM_IPID_PROBES) {
/* Yikes! We're already losing packets ... clamp down a bit ... */
if (o.debugging)
error("Idle scan initial zombie qualification test: %d probes sent, only %d returned", NUM_IPID_PROBES, probes_returned);
proxy->current_groupsz = MIN(12, proxy->max_groupsz);
proxy->current_groupsz = MAX(proxy->current_groupsz, proxy->min_groupsz);
proxy->senddelay += 5000;
}
/* OK, through experimentation I have found that some hosts *cough*
Solaris APPEAR to use simple IP ID incrementing, but in reality they
assign a new IP ID base to each host which connects with them. This
is actually a good idea on several fronts, but it totally
frustrates our efforts (which rely on side-channel IP ID info
leaking to different hosts). The good news is that we can easily
detect the problem by sending some spoofed packets "from" the first
target to the zombie and then probing to verify that the proxy IP ID
changed. This will also catch the case where the Nmap user is
behind an egress filter or other measure that prevents this sort of
sp00fery */
/* this behavior gets quite common in IPv6 so now its even more important to check */
if (target->v4hostip() || target->v6hostip()) {
for (probes_sent = 0; probes_sent < 4; probes_sent++) {
if (probes_sent != 0)
usleep(50000);
if (target->v4hostip()) {
send_tcp_raw(proxy->rawsd, proxy->ethptr,
target->v4hostip(), proxy->host.v4hostip(),
o.ttl, false,
o.ipoptions, o.ipoptionslen,
o.magic_port, proxy->probe_port,
sequence_base + probes_sent + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS,
TCP_SYN_PROBE_OPTIONS_LEN, NULL, 0);
} else {
ipv6_packet = build_tcp_raw_ipv6(target->v6hostip(), proxy->host.v6hostip(),
0x00, 0x0000,
o.ttl,
o.magic_port, proxy->probe_port,
sequence_base + probes_sent + 1, ack, 0, TH_SYN | TH_ACK, 0, 0,
(u8 *) TCP_SYN_PROBE_OPTIONS,
TCP_SYN_PROBE_OPTIONS_LEN, NULL, 0,
&packetlen);
res = send_ip_packet(proxy->rawsd, proxy->ethptr, &ss, ipv6_packet, packetlen);
if (res == -1)
fatal("Error occurred while trying to send IPv6 packet ");
free(ipv6_packet);
}
}
/* Sleep a little while to give packets time to reach their destination */
usleep(300000);
newipid = ipid_proxy_probe(proxy, NULL, NULL);
if (newipid == -1)
newipid = ipid_proxy_probe(proxy, NULL, NULL); /* OK, we'll give it one more try */
if (newipid < 0)
fatal("Your IP ID Zombie (%s; %s) is behaving strangely -- suddenly cannot obtain IP ID", proxy->host.HostName(), proxy->host.targetipstr());
distance = ipid_distance(proxy->seqclass, proxy->latestid, newipid);
if (distance <= 0) {
fatal("Your IP ID Zombie (%s; %s) is behaving strangely -- suddenly cannot obtain valid IP ID distance.", proxy->host.HostName(), proxy->host.targetipstr());
} else if (distance == 1) {
fatal("Even though your Zombie (%s; %s) appears to be vulnerable to IP ID sequence prediction (class: %s), our attempts have failed. This generally means that either the Zombie uses a separate IP ID base for each host (like Solaris), or because you cannot spoof IP packets (perhaps your ISP has enabled egress filtering to prevent IP spoofing), or maybe the target network recognizes the packet source as bogus and drops them", proxy->host.HostName(), proxy->host.targetipstr(), ipidclass2ascii(proxy->seqclass));
}
if (o.debugging && distance != 5) {
error("WARNING: IP ID spoofing test sent 4 packets and expected a distance of 5, but instead got %d", distance);
}
proxy->latestid = newipid;
}
}
/* Adjust timing parameters up or down given that an idlescan found a
count of 'testcount' while the 'realcount' is as given. If the
testcount was correct, timing is made more aggressive, while it is
slowed down in the case of an error */
static void adjust_idle_timing(struct idle_proxy_info *proxy,
Target *target, int testcount,
int realcount) {
static int notidlewarning = 0;
if (o.debugging > 1) {
log_write(LOG_STDOUT, "%s: tested/true %d/%d -- old grpsz/delay: %f/%d ",
__func__, testcount, realcount, proxy->current_groupsz, proxy->senddelay);
} else if (o.debugging && testcount != realcount) {
error("%s: testcount: %d realcount: %d -- old grpsz/delay: %f/%d",