Endlessh: An SSH Tarpit


Endlessh is an SSH tarpit that very slowly sends an never-ending, random
SSH banner
. It keeps SSH purchasers locked up for hours and even days
at a time. The scheme is to attach your proper SSH server on some other port
after which let the script kiddies rating caught on this tarpit as a substitute of
bothering a proper server.

Since the tarpit is in the banner earlier than any cryptographic alternate
occurs, this program would no longer depend upon any cryptographic libraries. It’s
a easy, single-threaded, standalone C program. It uses poll() to
trap a pair of purchasers at a time.


Utilization data is printed with -h.

Utilization: endlessh [-vhs] [-d MS] [-f CONFIG] [-l LEN] [-m LIMIT] [-p PORT]
  -4        Bind to IPv4 handiest
  -6        Bind to IPv6 handiest
  -d INT    Message millisecond delay [10000]
  -f        Area and cargo config file [/etc/endlessh/config]
  -h        Print this abet message and exit
  -l INT    Most banner line dimension (3-255) [32]
  -m INT    Most type of purchasers [4096]
  -p INT    Listening port [2222]
  -s        Print diagnostics to syslog as a substitute of identical old output
  -v        Print diagnostics (repeatable)

Argument uncover matters. The configuration file is loaded when the -f
argument is processed, so handiest the decisions that be conscious will override the
configuration file.

By default no log messages are produced. The first -v permits unusual
logging and a second -v permits debugging logging (noisy). All log
messages are sent to identical old output by default. -s causes them to be
sent to syslog.

endlessh -v >endlessh.log 2>endlessh.err

A SIGTERM signal will gracefully shut down the daemon, allowing it to
write an whole, constant log.

A SIGHUP signal requests a reload of the configuration file (-f).

A SIGUSR1 signal will print connections stats to the log.

Pattern Configuration File

The configuration file has similar syntax to OpenSSH.

# The port on which to hear for recent SSH connections.
Port 2222

# The never-ending banner is allotted one line at a time. Right here is the delay
# in milliseconds between particular person lines.
Lengthen 10000

# The scale of every and each line is randomized. This controls basically the most
# dimension of every and each line. Shorter lines could presumably per chance motivate purchasers on for longer if
# they provide up after a determined type of bytes.
MaxLineLength 32

# Most type of connections to settle for at a time. Connections beyond
# this will no longer be straight away rejected, but will wait in the queue.
MaxClients 4096

# Area the part stage for the log.
#   0 = Silent
#   1 = Traditional, necessary log messages
#   2 = Very noisy debugging data
LogLevel 0

# Area the household of the listening socket
#   0 = Spend IPv4 Mapped IPv6 (Both v4 and v6, default)
#   4 = Spend IPv4 handiest
#   6 = Spend IPv6 handiest
BindFamily 0

Carry out complications

Some more esoteric programs require additional configuration when building.

RHEL 6 / CentOS 6

This formulation uses a model of glibc older than 2.17 (December 2012), and
clock_gettime(2) is tranquil in librt. For these programs chances are high you’ll presumably per chance want to
link against librt:

carry out LDLIBS=-lrt

Solaris / illumos

These programs rep no longer encompass the total necessary functionality in libc and
the linker requires some additional libraries:

carry out CC=gcc LDLIBS='-lnsl -lrt -lsocket'

If you will no longer be the exercise of GCC or Clang, also override CFLAGS and LDFLAGS
to grab away GCC-instruct ideas. As an instance, on Solaris:

carry out CFLAGS=-quick LDFLAGS= LDLIBS='-lnsl -lrt -lsocket'

The feature check macros on these programs is rarely always kindly, so chances are high you’ll presumably per chance additionally
want to make exercise of -D__EXTENSIONS__ in CFLAGS.

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