illumos: manual page: in.rlogind.8

IN.RLOGIND(8) Maintenance Procedures IN.RLOGIND(8)

NAME

in.rlogind, rlogind - remote login server

SYNOPSIS

/usr/sbin/in.rlogind [-k5eExXciPp] [-s tos] [-S keytab]
[-M realm]

DESCRIPTION

in.rlogind is the server for the rlogin(1) program. The server provides
a remote login facility with authentication based on Kerberos V5 or
privileged port numbers.

in.rlogind is invoked by inetd(8) when a remote login connection is
established. When Kerberos V5 authentication is required (see option -k
below), the authentication sequence is as follows:

o Check Kerberos V5 authentication.

o Check authorization according to the rules in
krb5_auth_rules(7).

o Prompt for a password if any checks fail and /etc/pam.conf is
configured to do so.

In order for Kerberos authentication to work, a host/<FQDN> Kerberos
principal must exist for each Fully Qualified Domain Name associated with
the in.rlogind server. Each of these host/<FQDN> principals must have a
keytab entry in the /etc/krb5/krb5.keytab file on the in.rlogind server.
An example principal might be:

host/bigmachine.eng.example.com

See kadmin(8) for instructions on adding a principal to a krb5.keytab
file. See for a discussion of Kerberos authentication.

If Kerberos V5 authentication is not enabled, then the authentication
procedure follows the standard rlogin protocol:

o The server checks the client's source port. If the port is not
in the range 512-1023, the server aborts the connection.

o The server checks the client's source address. If an entry for
the client exists in both /etc/hosts and /etc/hosts.equiv, a
user logging in from the client is not prompted for a
password. If the address is associated with a host for which
no corresponding entry exists in /etc/hosts, the user is
prompted for a password, regardless of whether or not an
entry for the client is present in /etc/hosts.equiv. See
hosts(5) and hosts.equiv(5).

Once the source port and address have been checked, in.rlogind allocates
a pseudo-terminal and manipulates file descriptors so that the subsidiary
half of the pseudo-terminal becomes the stdin, stdout, and stderr for a
login process. The login process is an instance of the login(1) program,
invoked with the -r.

The login process then proceeds with the pam(3PAM) authentication
process. See SECURITY below. If automatic authentication fails, it
reprompts the user to login.

The parent of the login process manipulates the manager side of the
pseudo-terminal, operating as an intermediary between the login process
and the client instance of the rlogin program. In normal operation, a
packet protocol is invoked to provide Ctrl-S and Ctrl-Q type facilities
and propagate interrupt signals to the remote programs. The login process
propagates the client terminal's baud rate and terminal type, as found in
the environment variable, TERM.

OPTIONS

The following options are supported:

-5
Same as -k, for backwards compatibility.

-c
Requires Kerberos V5 clients to present a cryptographic
checksum of initial connection information like the name of
the user that the client is trying to access in the
initial authenticator. This checksum provides additionl
security by preventing an attacker from changing the initial
connection information. This option is mutually exclusive
with the -i option.

-e
Creates an encrypted session.

-E
Same as -e, for backwards compatibility.

-i
Ignores authenticator checksums if provided. This option
ignores authenticator checksums presented by current
Kerberos clients to protect initial connection information.
Option -i is the opposite of option -c.

-k
Allows Kerberos V5 authentication with the .k5login access
control file to be trusted. If this authentication system is
used by the client and the authorization check is passed,
then the user is allowed to log in.

-M realm
Uses the indicated Kerberos V5 realm. By default, the daemon
will determine its realm from the settings in the
krb5.conf(5) file.

-p
Prompts for authentication only if other authentication
checks fail.

-P
Prompts for a password in addition to other authentication
methods.

-s tos
Sets the IP TOS option.

-S keytab
Sets the KRB5 keytab file to use. The /etc/krb5/krb5.keytab
file is used by default.

-x
Same as -e, for backwards compatibility.

-X
Same as -e, for backwards compatibility.

USAGE

rlogind and in.rlogind are IPv6-enabled. See ip6(4P). IPv6 is not
currently supported with Kerberos V5 authentication.

Typically, Kerberized rlogin service runs on port 543 (klogin) and
Kerberized, encrypted rlogin service runs on port 2105 (eklogin). The
corresponding FMRI entries are:

svc:/network/login:klogin (rlogin with kerberos)
svc:/network/login:eklogin (rlogin with kerberos and encryption)

SECURITY

in.rlogind uses pam(3PAM) for authentication, account management, and
session management. The PAM configuration policy, listed through
/etc/pam.conf, specifies the modules to be used for in.rlogind. Here is
a partial pam.conf file with entries for the rlogin command using the
"rhosts" and UNIX authentication modules, and the UNIX account, session
management, and password management modules.

rlogin auth sufficient pam_rhosts_auth.so.1
rlogin auth requisite pam_authtok_get.so.1
rlogin auth required pam_dhkeys.so.1
rlogin auth required pam_unix_auth.so.1

rlogin account required pam_unix_roles.so.1
rlogin account required pam_unix_projects.so.1
rlogin account required pam_unix_account.so.1

rlogin session required pam_unix_session.so.1

With this configuration, the server checks the client's source address.
If an entry for the client exists in both /etc/hosts and
/etc/hosts.equiv, a user logging in from the client is not prompted for a
password. If the address is associated with a host for which no
corresponding entry exists in /etc/hosts, the user is prompted for a
password, regardless of whether or not an entry for the client is present
in /etc/hosts.equiv. See hosts(5) and hosts.equiv(5).

When running a Kerberized rlogin service (with or without the encryption
option), the pam service name that should be used is "krlogin".

If there are no entries for the rlogin service, then the entries for the
"other" service will be used. If multiple authentication modules are
listed, then the user may be prompted for multiple passwords. Removing
the pam_rhosts_auth.so.1 entry will disable the /etc/hosts.equiv and
~/.rhosts authentication protocol and the user would always be forced to
type the password. The sufficient flag indicates that authentication
through the pam_rhosts_auth.so.1 module is sufficient to authenticate the
user. Only if this authentication fails is the next authentication module
used.

DIAGNOSTICS

All diagnostic messages are returned on the connection associated with
the stderr, after which any network connections are closed. An error is
indicated by a leading byte with a value of 1.

Hostname for your address unknown.

No entry in the host name database existed for the client's machine.

Try again.

A fork by the server failed.

/usr/bin/sh: ...

The user's login shell could not be started.

NOTES

The authentication procedure used here assumes the integrity of each
client machine and the connecting medium. This is insecure, but it is
useful in an ``open'' environment.

A facility to allow all data exchanges to be encrypted should be present.

The pam_unix(7) module is no longer supported. Similar functionality is
provided by pam_authtok_check(7), pam_authtok_get(7),
pam_authtok_store(7), pam_dhkeys(7), pam_passwd_auth(7),
pam_unix_account(7), pam_unix_auth(7), and pam_unix_session(7).

The in.rlogind service is managed by the service management facility,
smf(7), under the service identifier:

svc:/network/login:rlogin (rlogin)
svc:/network/login:klogin (rlogin with kerberos)
svc:/network/login:eklogin (rlogin with kerberos and encryption)

Administrative actions on this service, such as enabling, disabling, or
requesting restart, can be performed using svcadm(8). Responsibility for
initiating and restarting this service is delegated to inetd(8). Use
inetadm(8) to make configuration changes and to view configuration
information for this service. The service's status can be queried using
the svcs(1) command.

February 5, 2022 IN.RLOGIND(8)