System Administration Commands in.telnetd(1M)
NAME
in.telnetd, telnetd - DARPA TELNET protocol server
SYNOPSIS
/usr/sbin/in.telnetd [-a authmode] [-EXUh] [-s tos]
[-S keytab] [-M realm]
DESCRIPTION
in.telnetd is a server that supports the DARPA standard TEL-
NET virtual terminal protocol. in.telnetd is normally
invoked in the internet server (see inetd(1M)), for requests to connect to the TELNET port as indicated by the /etc/services file (see services(4)).in.telnetd operates by allocating a pseudo-terminal device
for a client, then creating a login process which has theslave side of the pseudo-terminal as its standard input,
output, and error. in.telnetd manipulates the master side of
the pseudo-terminal, implementing the TELNET protocol and
passing characters between the remote client and the login process.When a TELNET session starts up, in.telnetd sends TELNET
options to the client side indicating a willingness to do remote echo of characters, and to suppress go ahead. Thepseudo-terminal allocated to the client is configured to
operate in "cooked" mode, and with XTABS, ICRNL and ONLCR enabled. See termio(7I).in.telnetd is willing to do: echo, binary, suppress go
ahead, and timing mark. in.telnetd is willing to have the
remote client do: binary, terminal type, terminal size, logout option, and suppress go ahead.in.telnetd also allows environment variables to be passed,
provided that the client negotiates this during the initial option negotiation. The DISPLAY environment variable may be sent this way, either by the TELNET general environment passing methods, or by means of the XDISPLOC TELNET option. DISPLAY can be passed in the environment option during the same negotiation where XDISPLOC is used. Note that if you use both methods, use the same value for both. Otherwise, the results may be unpredictable. These options are specified in Internet standards RFC 1096, RFC 1408, RFC 1510, RFC 1571, RFC 2941, RFC 2942, RFC 2946,SunOS 5.11 Last change: 10 Nov 2005 1
System Administration Commands in.telnetd(1M)
and RFC 1572. The following Informational draft is also sup-
ported: RFC 2952.The banner printed by in.telnetd is configurable. The
default is (more or less) equivalent to `uname -sr` and will
be used if no banner is set in /etc/default/telnetd. To set
the banner, add a line of the form BANNER="..."to /etc/default/telnetd. Nonempty banner strings are fed to
shells for evaluation. The default banner may be obtained byBANNER="\\r\\n\\r\\n`uname -s` `uname -r`\\r\\n\\r\\n"
and no banner will be printed if /etc/default/telnetd con-
tains BANNER="" OPTIONS The following options are supported:-a authmode This option may be used for specifying what
mode should be used for authentication. There are several valid values for authmode: valid Only allows connections when the remote user can provide validauthentication information to iden-
tify the remote user, and is allowed access to the specified account without providing a password. user Only allows connections when the remote user can provide validauthentication information to iden-
tify the remote user. The login(1) command will provide any additional user verification needed if the remote user is not allowed automatic access to the specified account.SunOS 5.11 Last change: 10 Nov 2005 2
System Administration Commands in.telnetd(1M)
none This is the default state. Authenti-
cation information is not required. If no or insufficient authentication information is provided, then thelogin(1) program provides the neces-
sary user verification. off This disables the authentication code. All user verification happens through the login(1) program.-E Disables encryption support negotiation.
-h Disables displaying host specific information
before login has been completed.-M realm Uses the indicated Kerberos V5 realm. By
default, the daemon will determine its realm from the settings in the krb5.conf(4) file.-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.-U Refuses connections that cannot be mapped to
a name through the getnameinfo(3SOCKET) func-
tion.-X Disables Kerberos V5 authentication support
negotiation.USAGE
telnetd and in.telnetd are IPv6-enabled. See ip6(7P).
SECURITYin.telnetd can authenticate using Kerberos V5 authentica-
tion, pam(3PAM), or both. By default, the telnet server will accept valid Kerberos V5 authentication credentials from atelnet client that supports Kerberos. in.telnetd can also
support an encrypted session from such a client if theSunOS 5.11 Last change: 10 Nov 2005 3
System Administration Commands in.telnetd(1M)
client requests it. The telnet protocol only uses single DES for sessionprotection-clients request service tickets with single DES
session keys. The KDC must know that host service principals that offer the telnet service support single DES, which, in practice, means that such principals must have single DES keys in the KDC database. In order for Kerberos authentication to work, a host/Kerberos principal must exist for each Fully Qualified Domain Name associated with the telnetd server. Each of
these host/principals must have a keytab entry in the /etc/krb5/krb5.keytab file on the telnetd server. An example
principal might be: host/bigmachine.eng.example.com See kadmin(1M) or gkadmin(1M) for instructions on adding a principal to a krb5.keytab file. See for a discussion of Kerberos authentication.in.telnetd uses pam(3PAM) for authentication, account
management, session management, and password management. The PAM configuration policy, listed through /etc/pam.conf,specifies the modules to be used for in.telnetd. Here is a
partial pam.conf file with entries for the telnet command using the UNIX authentication, account management, session management, and password management modules.telnet auth requisite pam_authtok_get.so.1
telent auth required pam_dhkeys.so.1
telent auth required pam_unix_auth.so.1
telnet account requisite pam_roles.so.1
telnet account required pam_projects.so.1
telnet account required pam_unix_account.so.1
telnet session required pam_unix_session.so.1
telnet password required pam_dhkeys.so.1
telent password requisite pam_authtok_get.so.1
telnet password requisite pam_authtok_check.so.1
telnet password required pam_authtok_store.so.1
SunOS 5.11 Last change: 10 Nov 2005 4
System Administration Commands in.telnetd(1M)
If there are no entries for the telnet 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. For a Kerberized telnet service, the correct PAM service name is ktelnet. FILES/etc/default/telnetd
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | service/network/telnet ||_____________________________|_____________________________|
SEE ALSO
login(1), svcs(1), telnet(1), gkadmin(1M), inetadm(1M), inetd(1M), kadmin(1M), svcadm(1M), pam(3PAM), getnameinfo(3SOCKET), issue(4), krb5.conf(4), pam.conf(4),services(4), attributes(5), pam_authtok_check(5),
pam_authtok_get(5), pam_authtok_store(5), pam_dhkeys(5),
pam_passwd_auth(5), pam_unix_account(5), pam_unix_auth(5),
pam_unix_session(5), smf(5), ip6(7P), termio(7I)
Alexander, S. RFC 1572, TELNET Environment Option. Network Information Center, SRI International, Menlo Park, Calif., January 1994. Borman, Dave. RFC 1408, TELNET Environment Option. Network Information Center, SRI International, Menlo Park, Calif., January 1993.Borman, Dave. RFC 1571, TELNET Environment Option Interoper-
ability Issues. Network Information Center, SRI Interna-
tional, Menlo Park, Calif., January 1994.SunOS 5.11 Last change: 10 Nov 2005 5
System Administration Commands in.telnetd(1M)
Crispin, Mark. RFC 727, TELNET Logout Option. Network Infor-
mation Center, SRI International, Menlo Park, Calif., April 1977.Marcy, G. RFC 1096, TELNET X Display Location Option. Net-
work Information Center, SRI International, Menlo Park, Calif., March 1989. Postel, Jon, and Joyce Reynolds. RFC 854, TELNET ProtocolSpecification. Network Information Center, SRI Interna-
tional, Menlo Park, Calif., May 1983. Waitzman, D. RFC 1073, TELNET Window Size Option. Network Information Center, SRI International, Menlo Park, Calif., October 1988. Kohl, J., Neuman, C., The Kerberos Network Authentication Service (V5), RFC 1510. September 1993. Ts'o, T. and J. Altman, Telnet Authentication Option, RFC 2941. September 2000. Ts'o, T., Telnet Authentication: Kerberos Version 5, RFC 2942. September 2000. Ts'o, T., Telnet Data Encryption Option, RFC 2946. September 2000. Ts'o, T., Telnet Encryption: DES 64 bit Cipher Feedback, RFC 2952. September 2000. NOTES Some TELNET commands are only partially implemented. Binary mode has no common interpretation except between similar operating systems. The terminal type name received from the remote client is converted to lower case.SunOS 5.11 Last change: 10 Nov 2005 6
System Administration Commands in.telnetd(1M)
The packet interface to the pseudo-terminal should be used
for more intelligent flushing of input and output queues.in.telnetd never sends TELNET go ahead commands.
The pam_unix(5) module is no longer supported.. Similar
functionality is provided by pam_authtok_check(5),
pam_authtok_get(5), pam_authtok_store(5), pam_dhkeys(5),
pam_passwd_auth(5), pam_unix_account(5), pam_unix_auth(5),
and pam_unix_session(5).
The in.telnetd service is managed by the service management
facility, smf(5), under the service identifier: svc:/network/telnet Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(1M). Responsibility for initiating and restarting this service is delegated to inetd(1M). Use inetadm(1M) tomake configuration changes and to view configuration infor-
mation for this service. The service's status can be queried using the svcs(1) command.SunOS 5.11 Last change: 10 Nov 2005 7