Manual Pages for UNIX Darwin command on man telnetd

TELNETD(8) BSD System Manager's Manual TELNETD(8)

NAME

tteellnneettdd - DARPA TELNET protocol server

SYNOPSIS

//uussrr//lliibbeexxeecc//tteellnneettdd [-UUhhllkknnss] [-DD debugmode] [-IIinitid] [-SS tos]

[-XX authtype] [-aa authmode] [-eeddeebbuugg] [-pp loginprog]

[-rrlowpty-highpty] [-uu len] [-ddeebbuugg [port]]

DESCRIPTION

The tteellnneettdd command is a server which supports the DARPA standard TELNET virtual terminal protocol. TTeellnneettdd is normally invoked by the internet

server (see inetd(8)) for requests to connect to the TELNET port as indi-

cated by the /etc/services file (see services(5)). The -ddeebbuugg option may

be used to start up tteellnneettdd manually, instead of through inetd(8). If started up this way, port may be specified to run tteellnneettdd on an alternate TCP port number. The tteellnneettdd command accepts the following options:

-aa authmode

This option may be used for specifying what mode should be used for authentication. Note that this option is only useful if tteellnneettdd has been compiled with support for the AUTHENTICATION option. There are several valid values for authmode: ddeebbuugg Turn on authentication debugging code. uusseerr Only allow connections when the remote user can provide valid authentication information to identify the remote

user, and is allowed access to the specified account with-

out providing a password. vvaalliidd Only allow connections when the remote user can provide valid authentication information to identify 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. ootthheerr Only allow connections that supply some authentication information. This option is currently not supported by any of the existing authentication mechanisms, and is thus

the same as specifying -aa vvaalliidd.

nnoonnee This is the default state. Authentication information is

not required. If no or insufficient authentication infor-

mation is provided, then the login(1) program will provide the necessary user verification. ooffff Disable the authentication code. All user verification will happen through the login(1) program.

-DD debugmode

This option may be used for debugging purposes. This allows tteellnneettdd to print out debugging information to the connection,

allowing the user to see what tteellnneettdd is doing. There are sev-

eral possible values for debugmode: ooppttiioonnss Print information about the negotiation of TELNET options. rreeppoorrtt Print the ooppttiioonnss information, plus some additional information about what processing is going on. nneettddaattaa Display the data stream received by tteellnneettdd. ppttyyddaattaa Display data written to the pty. eexxeerrcciissee Has not been implemented yet.

-ddeebbuugg Enable debugging on each socket created by tteellnneettdd (see SODEBUG

in socket(2)).

-eeddeebbuugg

If tteellnneettdd has been compiled with support for data encryption,

then the -eeddeebbuugg option may be used to enable encryption debug-

ging code.

-pp loginprog

Specify an alternate login(1) command to run to complete the login. The alternate command must understand the same command arguments as the standard login.

-hh Disable the printing of host-specific information before login

has been completed.

-II initid

This option is only applicable to UNICOS systems prior to 7.0. It specifies the ID from /etc/inittab to use when init starts login sessions. The default ID is fe.

-kk This option is only useful if tteellnneettdd has been compiled with both

linemode and kludge linemode support. If the -kk option is speci-

fied, then if the remote client does not support the LINEMODE option, then tteellnneettdd will operate in character at a time mode. It will still support kludge linemode, but will only go into kludge linemode if the remote client requests it. (This is done

by the client sending DONT SUPPRESS-GO-AHEAD and DONT ECHO.) The

-kk option is most useful when there are remote clients that do

not support kludge linemode, but pass the heuristic (if they

respond with WILL TIMING-MARK in response to a DO TIMING-MARK)

for kludge linemode support.

-ll Specify line mode. Try to force clients to use line- at-a-time

mode. If the LINEMODE option is not supported, it will go into kludge linemode.

-nn Disable TCP keep-alives. Normally tteellnneettdd enables the TCP keep-

alive mechanism to probe connections that have been idle for some period of time to determine if the client is still there, so that idle connections from machines that have crashed or can no longer be reached may be cleaned up.

-rr lowpty-highpty

This option is only enabled when tteellnneettdd is compiled for UNICOS.

It specifies an inclusive range of pseudo-terminal devices to

use. If the system has sysconf variable SCCRAYNPTY config-

ured, the default pty search range is 0 to SCCRAYNPTY; other-

wise, the default range is 0 to 128. Either lowpty or highpty may be omitted to allow changing either end of the search range.

If lowpty is omitted, the - character is still required so that

tteellnneettdd can differentiate highpty from lowpty.

-ss This option is only enabled if tteellnneettdd is compiled with support

for SecurID cards. It causes the -ss option to be passed on to

flag to indicate that only SecurID validated logins are allowed, and is usually useful for controlling remote logins from outside of a firewall.

-SS tos

-uu len This option is used to specify the size of the field in the utmp

structure that holds the remote host name. If the resolved host name is longer than len, the dotted decimal value will be used

instead. This allows hosts with very long host names that over-

flow this field to still be uniquely identified. Specifying -uu00

indicates that only dotted decimal addresses should be put into the utmp file.

-UU This option causes tteellnneettdd to refuse connections from addresses

that cannot be mapped back into a symbolic name via the gethostbyaddr(3) routine.

-XX authtype

This option is only valid if tteellnneettdd has been built with support for the authentication option. It disables the use of authtype authentication, and can be used to temporarily disable a specific authentication type without having to recompile tteellnneettdd.

TTeellnneettdd operates by allocating a pseudo-terminal device (see pty(4)) for

a client, then creating a login process which has the slave side of the

pseudo-terminal as stdin, stdout and stderr. TTeellnneettdd 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 is started up, tteellnneettdd sends TELNET options to the client side indicating a willingness to do the following TELNET options, which are described in more detail below: DO AUTHENTICATION WILL ENCRYPT DO TERMINAL TYPE DO TSPEED DO XDISPLOC

DO NEW-ENVIRON

DO ENVIRON WILL SUPPRESS GO AHEAD DO ECHO DO LINEMODE DO NAWS WILL STATUS DO LFLOW

DO TIMING-MARK

The pseudo-terminal allocated to the client is configured to operate in

``cooked'' mode, and with XTABS and CRMOD enabled (see tty(4)). TTeellnneettdd has support for enabling locally the following TELNET options: WILL ECHO When the LINEMODE option is enabled, a WILL ECHO or WONT ECHO will be sent to the client to indicate the current state of terminal echoing. When terminal echo is not desired, a WILL ECHO is sent to indicate that tteellnneettdd will take care of echoing any data that needs to be echoed to the terminal, and then nothing is echoed. When terminal echo is desired, a WONT ECHO is sent to indicate that tteellnneettdd will not be doing any terminal echoing, so the client should do any terminal echoing that is needed. WILL BINARY Indicate that the client is willing to send a 8 bits of data, rather than the normal 7 bits of the Network Virtual Terminal. WILL SGA Indicate that it will not be sending IAC GA, go ahead, commands. WILL STATUS Indicate a willingness to send the client, upon request, of the current status of all TELNET options.

WILL TIMING-MARK Whenever a DO TIMING-MARK command is received, it is

always responded to with a WILL TIMING-MARK.

WILL LOGOUT When a DO LOGOUT is received, a WILL LOGOUT is sent in response, and the TELNET session is shut down. WILL ENCRYPT Only sent if tteellnneettdd is compiled with support for data encryption, and indicates a willingness to decrypt the data stream. TTeellnneettdd has support for enabling remotely the following TELNET options: DO BINARY Sent to indicate that tteellnneettdd is willing to receive an 8 bit data stream.

DO LFLOW Requests that the client handle flow control charac-

ters remotely. DO ECHO This is not really supported, but is sent to identify a 4.2BSD telnet(1) client, which will improperly respond with WILL ECHO. If a WILL ECHO is received, a DONT ECHO will be sent in response.

DO TERMINAL-TYPE Indicate a desire to be able to request the name of

the type of terminal that is attached to the client side of the connection. DO SGA Indicate that it does not need to receive IAC GA, the go ahead command. DO NAWS Requests that the client inform the server when the window (display) size changes.

DO TERMINAL-SPEED Indicate a desire to be able to request information

about the speed of the serial line to which the client is attached. DO XDISPLOC Indicate a desire to be able to request the name of the X Window System display that is associated with the telnet client.

DO NEW-ENVIRON Indicate a desire to be able to request environment

variable information, as described in RFC 1572. DO ENVIRON Indicate a desire to be able to request environment variable information, as described in RFC 1408. DO LINEMODE Only sent if tteellnneettdd is compiled with support for linemode, and requests that the client do line by line processing.

DO TIMING-MARK Only sent if tteellnneettdd is compiled with support for both

linemode and kludge linemode, and the client responded with WONT LINEMODE. If the client responds with WILL TM, the it is assumed that the client supports kludge

linemode. Note that the [-kk] option can be used to

disable this. DO AUTHENTICATION Only sent if tteellnneettdd is compiled with support for authentication, and indicates a willingness to receive authentication information for automatic login. DO ENCRYPT Only sent if tteellnneettdd is compiled with support for data encryption, and indicates a willingness to decrypt the data stream. NNOOTTEESS By default tteellnneettdd will read the he, hn, and im capabilities from /etc/gettytab and use that information (if present) to determine what to display before the login: prompt. You can also use a System V style /etc/issue file by using the if capability, which will override im. The

information specified in either im or if will be displayed to both con-

sole and remote logins. FILES /etc/services /etc/gettytab /etc/inittab (UNICOS systems only) /etc/iptos (if supported) /usr/ucb/bftp (if supported)

RRFFCC-885555 TELNET OPTION SPECIFICATIONS

RRFFCC-885566 TELNET BINARY TRANSMISSION

RRFFCC-885577 TELNET ECHO OPTION

RRFFCC-885588 TELNET SUPPRESS GO AHEAD OPTION

RRFFCC-885599 TELNET STATUS OPTION

RRFFCC-886600 TELNET TIMING MARK OPTION

RRFFCC-886611 TELNET EXTENDED OPTIONS - LIST OPTION

RRFFCC-888855 TELNET END OF RECORD OPTION

RRFFCC-11007733 Telnet Window Size Option

RRFFCC-11007799 Telnet Terminal Speed Option

RRFFCC-11009911 Telnet Terminal-Type Option

RRFFCC-11009966 Telnet X Display Location Option

RRFFCC-11112233 Requirements for Internet Hosts - Application and Support

RRFFCC-11118844 Telnet Linemode Option

RRFFCC-11337722 Telnet Remote Flow Control Option

RRFFCC-11441166 Telnet Authentication Option

RRFFCC-11441111 Telnet Authentication: Kerberos Version 4

RRFFCC-11441122 Telnet Authentication: SPX

RRFFCC-11557711 Telnet Environment Option Interoperability Issues

RRFFCC-11557722 Telnet Environment Option

BUGS

Some TELNET commands are only partially implemented. Because of bugs in the original 4.2 BSD telnet(1), tteellnneettdd performs some dubious protocol exchanges to try to discover if the remote client is, in fact, a 4.2 BSD telnet(1). Binary mode has no common interpretation except between similar operating systems (Unix in this case). The terminal type name received from the remote client is converted to lower case. TTeellnneettdd never sends TELNET IAC GA (go ahead) commands. HISTORY IPv6 support was added by WIDE/KAME project. BSD March 1, 1994 BSD