KLOGIND(8)KLOGIND(8)NAME
klogind - remote login server
SYNOPSIS
klogind [ -kr54cpPef ] [[ -w[ip|maxhostlen[,[no]striplocal ]] ] [ -D
port ]
DESCRIPTION
Klogind is the server for the rlogin(1) program. The server is based
on rlogind(8) but uses Kerberos authentication.
The klogind server is invoked by inetd(8) when it receives a connection
on the port indicated in /etc/inetd.conf. A typical /etc/inetd.conf
configuration line for klogind might be:
klogin stream tcp nowait root /usr/cygnus/sbin/klogind klogind -e5c
When a service request is received, the following protocol is initi‐
ated:
1) Check authentication.
2) Check authorization via the access-control files .k5login and
.klogin in the user's home directory.
3) Prompt for password if any checks fail and the -p option was
supplied.
If the authentication succeeds, login the user by calling the accompa‐
nying login.krb5 or /bin/login, according to the definition of
DO_NOT_USE_K_LOGIN.
The configuration of klogind is done by command line arguments passed
by inetd. The options are:
-5 Allow 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. If the user has no
.k5login file, the login will be authorized if the results of
krb5_aname_to_localname conversion matches the account name.
Unless special rules are configured, this will be true if and
only if the Kerberos principal of the connecting user is in
the default local realm and the principal portion matches the
account name.
-4 Allow Kerberos V4 authentication with the .klogin access con‐
trol 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.
-k Allow Kerberos V5 and Kerberos V4 as acceptable authentica‐
tion mechanisms. This is the same as including -4 and -5.
-p
If all other authorization checks fail, prompt the user for
a password If this option is not included, access is denied
without successful authentication and authorization using one
of the previous mechanisms.
-P Prompt the user for a password. If the -P option is passed,
then the password is verified in addition to all other
checks.
-e Create an encrypted session.
-c Require Kerberos V5 clients to present a cryptographic check‐
sum 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. To benefit from this security, only Kerberos V5
should be trusted; Kerberos V4 and rhosts authentication do
not include this checksum. If this option is specified,
older Kerberos V5 clients that do not send a checksum in the
authenticator will not be able to authenticate to this
server. This option is mutually exclusive with the -i
option.
If neither the -c or -i options are specified,then
checksums are validated if presented. Since it is difficult
to remove a checksum from an authenticator without making the
authenticator invalid, this default mode is almost as signif‐
icant of a security improvement as -c if new clients are
used. It has the additional advantage of backwards compata‐
bility with some clients. Unfortunately, clients before Ker‐
beros V5, Beta5, generate invalid checksums; if these clients
are used, the -i option must be used.
-i Ignore authenticator checksums if provided. This option
ignore authenticator checksusm presented by current Kerberos
clients to protect initial connection information; it is the
opposite of -c. This option is provided because some older
clients--particularly clients predating the release of Ker‐
beros V5 Beta5 (May 1995)--present bogus checksums that pre‐
vent Kerberos authentication from succeeding in the default
mode.
The parent of the login process manipulates the master side of the pse‐
duo terminal, operating as an intermediary between the login process
and the client instance of the rlogin(1) program. In normal operation,
the packet protocol described in pty(4) is invoked to provide ^S/^Q
type facilities and propagate interrupt signals to the remote programs.
The login process propagates the client terminal's baud rate and termi‐
nal type, as found in the environment variable, ``TERM''; see envi‐
ron(7). The screen or window size of the terminal is requested from
the client, and window size changes from the client are propagated to
the pseudo terminal.
Klogind supports the following options to control the form of the host‐
name passed to login(1):
-w [ip|maxhostlen[,[no]striplocal]]
Controls the form of the remote hostname passed to login(1).
Specifying ip results in the numeric IP address always being
passed to login(1). Specifying a number, maxhostlen, sets the
maximum length of the hostname passed to login(1) before it will
be passed as a numeric IP address. If maxhostlen is 0, then the
system default, as determined by the utmp or utmpx structures,
is used. The nostriplocal and striplocal options, which must be
preceded by a comma, control whether or not the local host
domain is stripped from the remote hostname. By default, the
equivalent of striplocal is in effect.
Klogind supports five options which are used for testing purposes:
-S keytab Set the keytab file to use.
-M realm Set the Kerberos realm to use.
-L login Set the login program to use. This option only has an effect
if DO_NOT_USE_K_LOGIN was not defined when klogind was com‐
piled.
-D port Run in standalone mode, listening on port. The daemon will
exit after one connection and will not background itself.
-f Allows for standalone daemon operation. A new child is
started for each incoming connection and waits for it to fin‐
ish before accepting the next connection. This automagically
figures out which port to bind to if no port is specified.
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.
``Try again.''
A fork by the server failed.
``/bin/sh: ...''
The user's login shell could not be started.
SEE ALSOrlogind(8), rlogin(1)BUGS
A more extensible protocol should be used.
KLOGIND(8)