Masscan: Scan your total Net in under 5 minutes

sudo correct form-secure --have interaction-certain install git invent gcc
git clone https://github.com/robertdavidgraham/masscan
cd masscan
invent

# masscan -p80,8000-8100 10.0.0.0/8 2603: 3001:second00:da00::/112

Masscan can attain bigger than handsome detect whether or no longer ports are launch. It will also
total the TCP connection and interplay with the utility at that
port in advise to rob straightforward “banner” data.

Masscan helps banner checking on the following protocols:

• FTP
• HTTP
• IMAP4
• memcached
• POP3
• SMTP
• SSH
• SSL
• SMBv1
• SMBv2
• Telnet
• RDP
• VNC

The topic with that is that masscan contains its possess TCP/IP stack
destroy free the system you trip it on. When the local system receives
a SYN-ACK from the probed target, it responds with a RST packet that kills
the connection sooner than masscan can rob the banner.

The most attention-grabbing technique to demolish that is to construct masscan a separate IP
address. This would peek love one of the following examples:

# masscan 10.0.0.0/8 -p80 --banners --source-ip 192.168.1.200
  # masscan 2a00: 1450: 4007: 810::/112 -p80 --banners --source-ip 2603: 3001:second00:da00: 91d7:b54:b498: 859d

The address you utilize has to be on the local subnet and no longer otherwise
be venerable by one more system. Masscan will warn you that you own made a
mistake, but it’s seemingly you’ll per chance per chance even’ve tousled the opposite machine’s communications
for a lot of minutes, so watch out.

In some cases, much like WiFi, this is never imaginable. In these cases, it’s seemingly you’ll per chance per chance even
firewall the port that masscan makes use of. This prevents the local TCP/IP stack
from seeing the packet, but masscan tranquil sees it because it bypasses the
local stack. For Linux, this would per chance peek love:

# iptables -A INPUT -p tcp --dport 61000 -j DROP
# masscan 10.0.0.0/8 -p80 --banners --source-port 61000

You per chance want to favor ports that invent no longer war with ports Linux may well per chance otherwise
favor for source-ports. Chances are you’ll per chance per chance per chance per chance also glimpse the fluctuate Linux makes use of, and reconfigure
that change, by having a peek in the file:

/proc/sys/rep/ipv4/ip_local_port_range

On the most up-to-date version of Kali Linux (2018-August), that change is 32768 to 60999, so
it’s most reasonable to tranquil favor ports either below 32768 or 61000 and above.

Atmosphere an iptables rule entirely lasts unless the following reboot. It is well-known to look up
assign the configuration depending upon your distro, much just like the use of iptables-assign
and/or iptables-power.

On Mac OS X and BSD, there are the same steps. To search out out the ranges to maintain some distance from,
use a advise love the following:

# sysctl rep.inet.ip.portrange.first rep.inet.ip.portrange.last

On FreeBSD and older MacOS, use an ipfw advise:

# sudo ipfw add 1 instruct tcp from any to any 40000 in
# masscan 10.0.0.0/8 -p80 --banners --source-port 40000

On more moderen MacOS and OpenBSD, use the pf packet-filter utility.
Edit the file /etc/pf.conf to add a line love the following:

block in proto tcp from any to any port 40000

Then to allow the firewall, trip the advise:

If the firewall is already running, then either reboot or reload the foundations
with the following advise:

Dwelling windows doesn’t answer with RST packets, so neither of these tactics
are obligatory. Nevertheless, masscan is tranquil designed to work entirely the use of its
possess IP address, so it’s most reasonable to tranquil trip that technique when imaginable, even when it’s
no longer strictly obligatory.

The same thing is wished for other checks, much just like the --heartbleed test,
which is handsome a compose of banner checking.

Easy the arrangement to scan your total Net

While recommended for smaller, inner networks, this system is genuinely designed
alongside with your total Net in thoughts. It will also peek something love this:

# masscan 0.0.0.0/0 -p0-65535

Scanning your total Net is sinful. For one thing, parts of the Net react
badly to being scanned. For one more thing, some sites note scans and add you
to a ban list, which will secure you firewalled from recommended parts of the Net.
Therefore, it’s most reasonable to exclude heaps of ranges. To blacklist or exclude ranges,
it’s most reasonable to make use of the following syntax:

# masscan 0.0.0.0/0 -p0-65535 --excludefile exclude.txt

This handsome prints the implications to the advise-line. You per chance desire them
saved to a file as a replace. Therefore, you’d like something love:

# masscan 0.0.0.0/0 -p0-65535 -oX scan.xml

This protects the implications in an XML file, allowing you to without procure 22 situation dump the
results in a database or something.

However, this entirely goes on the default price of 100 packets/second, which will
have interaction forever to scan the Net. It is well-known to fling it up as so:

# masscan 0.0.0.0/0 -p0-65535 --max-price 100000

This may occasionally increase the price to 100,000 packets/second, which will scan the
total Net (minus excludes) in about 10 hours per port (or 655,360 hours
if scanning all ports).

The item to stumble on about this advise-line is that these are all nmap
love minded alternate strategies. Moreover, “invisible” alternate strategies love minded with nmap
are also role for you: -sS -Pn -n --randomize-hosts --ship-eth. Likewise,
the layout of the XML file is inspired by nmap. There are, clearly, a
lot of variations, for the explanation that asynchronous nature of this system
results in a fundamentally diversified technique to the sphere.

The above advise-line is rather cumbersome. Rather then placing the total lot
on the advise-line, it’s going to also also be saved in a file as a replace. The above settings
would peek love this:

# My Scan
price =  100000.00
output-layout = xml
output-dwelling = all
output-filename = scan.xml
ports = 0-65535
fluctuate = 0.0.0.0-255.255.255.255
excludefile = exclude.txt

To utilize this configuration file, use the -c:

This also makes issues more straightforward for these that repeat a scan.

By default, masscan first loads the configuration file
/etc/masscan/masscan.conf. Any later configuration parameters override what’s
in this default configuration file. That’s where I assign my “excludefile”
parameter so that I invent no longer ever put out of your mind it. It handsome works automatically.

Getting output

By default, masscan produces rather colossal textual state recordsdata, but it absolutely’s easy
to remodel them into every other layout. There are 5 supported output formats:

1. xml: Factual use the parameter -oX .
   Or, use the parameters --output-layout xml and --output-filename .

2. binary: Right here is the masscan builtin layout. It produces noteworthy smaller recordsdata so that
   when I scan the Net my disk doesn’t beget up. They must tranquil be parsed,
   though. The advise-line choice --readscan will read binary scan recordsdata.
   Using --readscan with the -oX choice will invent an XML version of the
   results file.

3. grepable: Right here is an implementation of the Nmap -oG
   output that may well per chance even be without procure 22 situation parsed by advise-line tools. Factual use the
   parameter -oG . Or, use the parameters --output-layout grepable and
   --output-filename .

4. json: This protects the implications in JSON layout. Factual use the
   parameter -oJ . Or, use the parameters --output-layout json and
   --output-filename .

5. list: Right here is a straightforward list with one host and port pair
   per line. Factual use the parameter -oL . Or, use the parameters
   --output-layout list and --output-filename . The layout is:

   Comparability with Nmap

   The do sensible, every effort has been taken to invent this system familiar
   to nmap users, even supposing it be fundamentally diversified. Masscan is tuned
   for enormous replace scanning of heaps of machines, whereas nmap is designed for
   intensive scanning of a single machine or a runt fluctuate.

   Two well-known variations are:

   • no default ports to scan, you’ll need to specify -p
   • target hosts are IP addresses or straightforward ranges, no longer DNS names, nor
     the funky subnet ranges nmap can use (love 10.0.0-255.0-255).

   Chances are you’ll per chance per chance per chance per chance also acquire of masscan as having the following settings completely
   enabled:

   • -sS: this does SYN scan entirely (currently, will alternate in due course)
   • -Pn: doesn’t ping hosts first, which is elementary to the async operation
   • -n: no DNS decision happens
   • --randomize-hosts: scan fully randomized, persistently, it’s seemingly you’ll per chance per chance even’t alternate this
   • --ship-eth: sends the use of uncooked libpcap

   If you happen to’d love a list of additional nmap love minded settings, use the following
   advise:

   Transmit price (IMPORTANT!!)

   This program spews out packets very immediate. On Dwelling windows, or from VMs,
   it’s going to attain 300,000 packets/second. On Linux (no virtualization) it’s going to
   attain 1.6 million packets-per-second. That’s immediate satisfactory to melt most networks.

   Point out that it’s going to entirely melt your possess network. It randomizes the target
   IP addresses so that it should not crush any distant network.

   By default, the price is determined to 100 packets/second. To amplify the price to
   a million use something love --price 1000000.

   When scanning the IPv4 Net, it’s seemingly you’ll be scanning a total bunch subnets,
   so even supposing there is a excessive price of packets going out, every
   target subnet will acquire a runt price of incoming packets.

   Nevertheless, with IPv6 scanning, you will are inclined to focal level on a single
   target subnet with billions of addresses. Thus, your default
   behavior will crush the target network. Networks typically
   shatter under the burden that masscan can generate.

   This half describes the foremost make complications with this system.

   Code Layout

   The file famous.c contains the famous() goal, as you would request. It also
   contains the transmit_thread() and receive_thread() capabilities. These
   capabilities own been deliberately flattened and carefully commented so that you
   can read the make of this system merely by stepping line-by-line by
   every of these.

   Asynchronous

   Right here is an asynchronous make. In other words, it’s to nmap what
   the nginx web-server is to Apache. It has separate transmit and acquire
   threads which may well per chance per chance be largely impartial from one one more. It is the same compose of
   make stumbled on in scanrand, unicornscan, and ZMap.

   Due to it be asynchronous, it runs as immediate as the underlying packet transmit
   enables.

   Randomization

   A key distinction between Masscan and other scanners is the technique it randomizes
   targets.

   The elementary theory is to own a single index variable that starts at
   zero and is incremented by one for every probe. In C code, that is expressed
   as:

   for (i = 0; i < fluctuate; i++) {
       scan(i);
   }
   

   Now we must translate the index into an IP address. Shall we explain that you genuinely want to
   scan all "inner most" IP addresses. That is at menace of be the desk of ranges love:

   192.168.0.0/16
   10.0.0.0/8
   172.16.0.0/12
   

   In this instance, the foremost 64k indexes are appended to 192.168.x.x to compose
   the target address. Then, the following 16-million are appended to 10.x.x.x.
   The last indexes in the fluctuate are applied to 172.16.x.x.

   In this instance, we entirely own three ranges. When scanning your total Net,
   we own in note bigger than 100 ranges. That's because it's most reasonable to blacklist
   or exclude heaps of sub-ranges. This chops up the desired fluctuate into hundreds
   of smaller ranges.

   This results in a single of the slowest parts of the code. We transmit 10 million
   packets per second and must remodel an index variable to an IP address
   for every probe. We resolve this by doing a "binary search" in a runt
   quantity of memory. At this packet price, cache efficiencies initiate to dominate
   over algorithm efficiencies. There are heaps of more environment friendly tactics in
   idea, but they all require so noteworthy memory as to be slower in note.

   We call the goal that translates from an index into an IP address
   the favor() goal. In use, it looks love:

   for (i = 0; i < fluctuate; i++) {
       ip = favor(addresses, i);
       scan(ip);
   }
   

   Masscan helps no longer entirely IP address ranges, but also port ranges. This implies
   we must favor from the index variable both an IP address and a port. This
   is rather straightforward:

   fluctuate = ip_count port_count;
   for (i = 0; i < fluctuate; i++) {
       ip   = favor(addresses, i / port_count);
       port = favor(ports,     i % port_count);
       scan(ip, port);
   }
   

   This results in one more costly half of the code. The division/modulus
   directions are around 90 clock cycles, or 30 nanoseconds, on x86 CPUs. When
   transmitting at a price of 10 million packets/second, we own entirely
   100 nanoseconds per packet. I glimpse no technique to optimize this any greater. Fortunately,
   though, two such operations may well per chance even be done concurrently, so doing two
   of these, as proven above, will not be any more costly than doing one.

   There are genuinely some easy optimizations for the above performance complications,
   but they all count on i++, the truth that the index variable will increase one
   by one by the scan. If truth be told, we must randomize this variable. We
   want to randomize the advise of IP addresses that we scan or we are going to blast the
   heck out of target networks that aren't constructed for this stage of fling. We
   want to spread our web site visitors evenly over the target.

   The technique we randomize is merely by encrypting the index variable. By definition,
   encryption is random and creates a 1-to-1 mapping between the distinctive index
   variable and the output. This implies that whereas we linearly fight by the
   fluctuate, the output IP addresses are fully random. In code, this looks love:

   fluctuate = ip_count port_count;
   for (i = 0; i < fluctuate; i++) {
       x = encrypt(i);
       ip   = favor(addresses, x / port_count);
       port = favor(ports,     x % port_count);
       scan(ip, port);
   }
   

   This also has a prime price. For the explanation that change is an unpredictable size as a replace
   of a nice even energy of two, we won't use low-price binary tactics love
   AND (&) and XOR (^). As an alternative, we must make use of costly operations love
   MODULUS (%). In my fresh benchmarks, it be taking 40 nanoseconds to
   encrypt the variable.

   This structure enables for a total bunch chilly aspects. For instance, it helps
   "shards". Chances are you'll per chance per chance per chance per chance also role up 5 machines every doing a fifth of the scan or
   fluctuate / shard_count. Shards may well per chance even be more than one machines, or merely more than one
   network adapters on the same machine, or even (if you desire) more than one IP
   source addresses on the same network adapter.

   Or, it's seemingly you'll per chance per chance even use a 'seed' or 'key' to the encryption goal, so that you secure
   a diversified advise on every occasion you scan, love x = encrypt(seed, i).

   We may well per chance conclude the scan by exiting out of this system, and merely
   remembering the fresh price of i, and restart it later. I attain that a lot
   at some stage in building. I glimpse something going harmful with my Net scan, so
   I hit to demolish the scan, then restart it after I've fastened the bug.

   One more goal is retransmits/retries. Packets every as soon as in some time secure dropped on the
   Net, so it's seemingly you'll per chance per chance even ship two packets back-to-back. Nevertheless, something that
   drops one packet may well per chance merely tumble the immediately following packet. Therefore, you
   want to ship the copy about 1 second apart. Right here is easy. We already own
   a 'price' variable, which is the replace of packets-per-second price we are
   transmitting at, so the retransmit goal is merely to make use of i + price
   as the index. One in every of for the time being I'll attain a watch of the Net,
   and differentiate "back-to-back", "1 second", "10 second", and "1 minute"
   retransmits this technique in advise to glimpse if there's any distinction in what
   gets dropped.

   C10 Scalability

   The asynchronous technique is smartly-known as a technique to the "c10k field".
   Masscan is designed for the following stage of scalability, the "C10M field".

   The C10M solution is to bypass the kernel. There are three famous kernel
   bypasses in Masscan:

   • customized network driver
   • user-mode TCP stack
   • user-mode synchronization

   Masscan can use the PF_RING DNA driver. This driver DMAs packets without extend
   from user-mode memory to the network driver with zero kernel involvement.
   That enables software program, even with a unhurried CPU, to transmit packets on the most
   price the hardware enables. If you happen to assign 8 10-gbps network playing cards in a computer,
   this means it's going to also transmit at 100-million packets/second.

   Masscan has its possess constructed-in TCP stack for grabbing banners from TCP
   connections. This implies it's going to without procure 22 situation give a favor to 10 million concurrent TCP
   connections, assuming clearly that the computer has satisfactory memory.

   Masscan has no "mutex". As much as date mutexes (aka. futexes) are mostly user-mode,
   but they've two complications. The first field is that they role off cache-strains
   to bounce hasty back-and-forth between CPUs. The second is that when there
   is contention, they are able to attain a system call into the kernel, which kills
   performance. A mutex on the immediate path of a program severely limits scalability.
   As an alternative, Masscan makes use of "rings" to synchronize issues, much like when the
   user-mode TCP stack in the acquire thread needs to transmit a packet without
   interfering with the transmit thread.

   Portability

   The code runs effectively on Linux, Dwelling windows, and Mac OS X. Your total well-known bits are
   in unprecedented C (C90). Therefore, it compiles on Visual Studio with Microsoft's
   compiler, the Clang/LLVM compiler on Mac OS X, and GCC on Linux.

   Dwelling windows and Macs aren't tuned for packet transmit, and secure entirely about 300,000
   packets-per-second, whereas Linux can attain 1,500,000 packets/second. That's
   almost definitely faster than you'd like anyway.

   Stable code

   A bounty is equipped for vulnerabilities, glimpse the VULNINFO.md file for more
   data.

   This project makes use of protected capabilities love strcpy_s() in desire to unsafe capabilities
   love strcpy().

   This project has computerized unit regression assessments (invent regress).

   Compatibility

   Rather a couple of effort has long previous into making the enter/output peek love nmap, which
   all individuals who does port scans is (or must tranquil be) familiar with.

   IPv6 and IPv4 coexistence

   Masscan helps IPv6, but there's not any particular mode, both are supported
   on the same time. (There'll not be this form of thing as a -6 choice -- it be persistently accessible).

   In any instance you glimpse of masscan usage,
   merely assign an IPv6 address where you glimpse an IPv4 address. Chances are you'll per chance per chance per chance per chance also encompass
   IPv4 and IPv6 addresses concurrently in the same scan. Output involves
   the appropriate address on the same do, without a particular marking.

   Factual undergo in thoughts that IPv6 address home is genuinely tall. You per chance invent no longer want to scan
   for enormous ranges, other than per chance the foremost 64k addresses of a subnet that were assigned
   through DHCPv6.

   As an alternative, you'll doubtless want to scan colossal lists of addresses saved
   in a file (--encompass-file filename.txt) that to acquire from other sources.
   Delight in everywhere in the do else, this file can possess lists of both IPv4 and IPv6 addresses.
   The test file I take advantage of contains 8 million addresses. Files of that size desire a couple
   extra seconds to be read on startup (masscan forms the addresses and eliminates
   duplicates sooner than scanning).

   Do not put out of your mind that masscan contains its possess network stack. Thus, the local machine
   you trip masscan from doesn't must tranquil be IPv6 enabled -- though the local
   network needs with a knowing to route IPv6 packets.

   PF_RING

   To secure previous 2 million packets/second, you'd like an Intel 10-gbps Ethernet
   adapter and a certain driver known as "PF_RING ZC" from ntop. Masscan doesn't must tranquil be rebuilt in advise to make use of PF_RING. To utilize PF_RING,
   it be well-known to supply the following parts:

   • libpfring.so (installed in /usr/lib/libpfring.so)
   • pf_ring.ko (their kernel driver)
   • ixgbe.ko (their version of the Intel 10-gbps Ethernet driver)

   You invent no longer want to supply their version of libpcap.so.

   When Masscan detects that an adapter is called something love zc:enp1s0 as a replace
   of something love enp1s0, it's going to automatically switch to PF_RING ZC mode.

   A more ingredient discussion may well per chance even be stumbled on in PoC||GTFO 0x15.

   Regression testing

   The project consists of a constructed-in unit test:

   $ invent test
   bin/masscan --selftest
   selftest: success!
   

   This assessments heaps of tricky bits of the code. You may well tranquil attain this after building.

   Efficiency testing

   To test performance, trip something love the following to a throw-away address,
   to maintain some distance from overloading your local router:

   $ bin/masscan 0.0.0.0/4 -p80 --price 100000000 --router-mac 66-55-44-33-22-11
   

   The synthetic --router-mac retains packets on the local network segments so that
   they may well per chance per chance no longer exit to the Net.

   Chances are you'll per chance per chance per chance per chance also furthermore test in "offline" mode, which is how immediate this system runs
   without the transmit overhead:

   $ bin/masscan 0.0.0.0/4 -p80 --price 100000000 --offline
   

   This second benchmark exhibits roughly how immediate this system would trip if it were
   the use of PF_RING, which has near zero overhead.

   By the technique, the randomization algorithm makes heavy use of "integer arithmetic",
   a chronically unhurried operation on CPUs. As much as date CPUs own doubled the fling
   at which they construct this calculation, making masscan noteworthy faster.

   This software program created by Robert Graham:
   email: [email protected]
   twitter: @ErrataRob

   

   Sneha Gupta
   

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