Netcat: Difference between revisions

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netcat can refer to the following projects. Each implementation has similar functionalities, but the command line options may differ.
netcat can refer to the following projects. Each implementation has similar functionalities, but the command line options may differ.


# GNU <code>netcat</code> (which is symlinked to <code>nc</code> on some Linux systems, leading to confusion)  
#GNU <code>netcat</code> (which is symlinked to <code>nc</code> on some Linux systems, leading to confusion)
# OpenBSD <code>nc</code>
#OpenBSD <code>nc</code>
# Nmap's <code>ncat</code> (which is also symlinked to nc) with lots of features including SSL support and proxy connections.
#Nmap's <code>ncat</code> (which is also symlinked to nc) with lots of features including SSL support and proxy connections.


== Usage ==
==Usage==
For the most part, netcat and ncat are very similar. The older OpenBSD nc has less features.
For the most part, netcat and ncat are very similar. The older OpenBSD nc has less features.
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=== SSL with ncat ===
===SSL with ncat===
ncat allows for creating SSL server or client.
ncat allows for creating SSL server or client.
{| class="wikitable"
{| class="wikitable"
!
!Description
!
!Command
|-
|-
|Connect to a server using SSL
|Connect to a server using SSL
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<code>ncat --listen 443 --ssl --ssl-key key.pem --ssl-cert cert.pem</code>
<code>ncat --listen 443 --ssl --ssl-key key.pem --ssl-cert cert.pem</code>
|}
|}
<br />
 
== Tasks ==
 
=== Create a remote shell ===
With ncat, you can use the --exec option to spawn a program on a new connection.
{{Highlight
| code = hostA# ncat --exec /bin/sh -l 8888
 
hostB# ncat  hostA 8888
## Any command you type goes to /bin/sh on hostA
| lang = terminal
}}
If you want to do this a bit more securely, you can also:
 
* Enable SSL with <code>--ssl</code>.
* Restrict access to a specific host with <code>--allow $sourceIP</code>.

Revision as of 21:58, 17 December 2021

netcat/nc/ncat are utilities that sends and receives data using TCP or UDP.

netcat can refer to the following projects. Each implementation has similar functionalities, but the command line options may differ.

  1. GNU netcat (which is symlinked to nc on some Linux systems, leading to confusion)
  2. OpenBSD nc
  3. Nmap's ncat (which is also symlinked to nc) with lots of features including SSL support and proxy connections.

Usage

For the most part, netcat and ncat are very similar. The older OpenBSD nc has less features.

nc netcat ncat
Listen on a port nc -l -p $port netcat -l $port ncat -l -p $port
Send to a port nc $port netcat $port ncat $port
Send to a port, using a specific source port n/a netcat -p $sport $dest $dport ncat -p $sport $dest $dport

SSL with ncat

ncat allows for creating SSL server or client.

Description Command
Connect to a server using SSL ncat -C --ssl <server> 443
Verify a server's SSL ncat -C --ssl-verify <server> 443
Listen using SSL (auto generated) ncat --listen --ssl
Listen using SSL (manual SSL certs) openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365

ncat --listen 443 --ssl --ssl-key key.pem --ssl-cert cert.pem

Tasks

Create a remote shell

With ncat, you can use the --exec option to spawn a program on a new connection. 

hostA# ncat --exec /bin/sh -l 8888

hostB# ncat  hostA 8888
## Any command you type goes to /bin/sh on hostA

If you want to do this a bit more securely, you can also:

  • Enable SSL with --ssl.
  • Restrict access to a specific host with --allow $sourceIP.