TCP Wrappers in Linux

Introduction

Tcp Wrapper is a Library which provides control access and logging for the services over a server which accepts tcp connections.Most of the Linux Systems are compiled with tcp wrappers. it is a network filter ACL(access control list) that is used to filter the network access.

How TCP Wrappers Help?

• helps in system logging
• pattern matching access control
• verifies the hostname
• Protection against spoofing attacks

in these four ways tcp wrappers be helpful to us.

Explanation

 Now to check if a program is compiled with tcp wrapper we use following command.

ldd /path/to/program | grep wrap

and this is gonna provide us information if the service is compiled with wrapper library. See example Below.

as we can see that libwrap.so is dependency for sshd service.

Further we can use /etc/hosts.allow & /etc/hosts.deny Files to control system access. Let's Say i want to Deny all to access MySQL service and allow only Localhost. Following will be Configuration for it.

You can Set WildCard for it aswell to allow a list or a network. Let's say you want to allow a subnet as 192.168.*.* for SSH services.

 

In case of any queries Let me know. Thanks

TCP Wrappers in Linux

By: Adeel Chaudhary on: 07:53