Minimum securization for sshd

I run an RaspberryPi inside my home network with ssh access allowed. One of the first things I’d done was to install fail2ban package.

I know this is not enough by far. A really secure configuration requires more intel in it but I let it that way just to check how much penetration attemps I’ll see.

After a fast review in the /var/log/fail2ban.log file I notice that almost everything were ssh tries to log in the system. Which is perfectly normal because the system only exposes a web server and the sshd daemon.

An easy and fast securization for your home systems with ssh is to edit the /etc/hosts.allow and the /etc/host deny files to concrete what IP’s are allow to log in via ssh and deny all the rest. You may do the same secure configuration via /etc/ssh/sshd_config what it requieres more ssh knowledge and I prefer dedicate another post to it.

To allow you home network edit your /etc/host.allow and add:
sshd: # this allow your local lan
sshd: # this allow your localhost

To deny any other IP edit your /etc/hosts.deny and add:
sshd: ALL

How to install a concrete binary in a rpm distro

How to install a concrete binary in a rpm based distribution? Let’s asume you have a rpm based distro. I will wrote this little howto using a CentOS 7.8.

For instance you need to install iwlist but you don’t know what package provides you that binary. You have to type:

# yum provides iwlist

Your local database will return you something like this:

[pbenavent@localhost ~]$ yum provides iwlist
Complementos cargados:fastestmirror
Determining fastest mirrors
* base:
* epel:
* extras:
* updates:
1:wireless-tools-29-13.el7.x86_64 : Wireless ethernet configuration tools
Repositorio : @epel
Resultado obtenido desde:
Nombre del archivo : /usr/sbin/iwlist

Now you know the package name that you need to install, so the only thing you need to do is installed:

# yum install wireless-tools

As you may notice by reading the above lines, it’s assumed that your repository have indexed in its information the binary and package you’re querying for. In this particular exemple, the binary was iwlist and in the answer you read the full path indexed (/usr/bin/iwlist) wich is provided by EPEL repos. Remember the EPEL repo it’s not installed by defaul.