R-Services

Frequently Abused Commands

Command	Service Daemon	Port	TCP/UDP	Description
rcp	rshd	514	TCP	Copy a file or directory bidirectionally from the local system to the remote system (or vice versa) or from one remote system to another. It works like the cp command on Linux but provides no warning to the user for overwriting existing files on a system.
rsh	rshd	514	TCP	Opens a shell on a remote machine without a login procedure. Relies upon the trusted entries in the /etc/hosts.equiv and .rhosts files for validation.
rexec	rexecd	512	TCP	Enables a user to run shell commands on a remote machine. Requires authentication through the use of a username and password through an unencrypted network socket. Authentication is overridden by the trusted entries in the /etc/hosts.equiv and .rhosts files.
rlogin	rlogind	513	TCP	Enables a user to log in to a remote host over the network. It works similarly to telnet but can only connect to Unix-like hosts. Authentication is overridden by the trusted entries in the /etc/hosts.equiv and .rhosts files.

Trusted Hosts File

/etc/hosts.equiv

The /etc/hosts.equiv file contains a list of trusted hosts and is used to grant access to other systems on the network. When users on one of these hosts attempt to access the system, they are automatically granted access without further authentication.

.rhosts

The .rhosts file contains a list of trusted hosts and is used to grant access to other systems on the network. When users on one of these hosts attempt to access the system, they are automatically granted access without further authentication.

Note: The hosts.equiv file is recognized as the global configuration regarding all users on a system, whereas .rhosts provides a per-user configuration.

Scanning for R-Services

sudo nmap -sV -p 512,513,514 10.0.17.2

Logging in Using Rlogin

rlogin 10.0.17.2 -l htb-student

Listing Authenticated Users Using Rwho

rwho

Listing Authenticated Users Using Rusers

rusers -al 10.0.17.5