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Diffstat (limited to 'crypto/telnet/telnetd/telnetd.8')
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diff --git a/crypto/telnet/telnetd/telnetd.8 b/crypto/telnet/telnetd/telnetd.8 new file mode 100644 index 0000000..f618385 --- /dev/null +++ b/crypto/telnet/telnetd/telnetd.8 @@ -0,0 +1,607 @@ +.\" Copyright (c) 1983, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)telnetd.8 8.4 (Berkeley) 6/1/94 +.\" +.Dd June 1, 1994 +.Dt TELNETD 8 +.Os BSD 4.2 +.Sh NAME +.Nm telnetd +.Nd DARPA +.Tn TELNET +protocol server +.Sh SYNOPSIS +.Nm /usr/libexec/telnetd +.Op Fl BUhlkns +.Op Fl D Ar debugmode +.Op Fl I Ns Ar initid +.Op Fl S Ar tos +.Op Fl X Ar authtype +.Op Fl a Ar authmode +.Op Fl edebug +.Op Fl r Ns Ar lowpty-highpty +.Op Fl u Ar len +.Op Fl debug Op Ar port +.Sh DESCRIPTION +The +.Nm telnetd +command is a server which supports the +.Tn DARPA +standard +.Tn TELNET +virtual terminal protocol. +.Nm Telnetd +is normally invoked by the internet server (see +.Xr inetd 8 ) +for requests to connect to the +.Tn TELNET +port as indicated by the +.Pa /etc/services +file (see +.Xr services 5 ) . +The +.Fl debug +option may be used to start up +.Nm telnetd +manually, instead of through +.Xr inetd 8 . +If started up this way, +.Ar port +may be specified to run +.Nm telnetd +on an alternate +.Tn TCP +port number. +.Pp +The +.Nm telnetd +command accepts the following options: +.Bl -tag -width "-a authmode" +.It Fl a Ar authmode +This option may be used for specifying what mode should +be used for authentication. +Note that this option is only useful if +.Nm telnetd +has been compiled with support for the +.Dv AUTHENTICATION +option. +There are several valid values for +.Ar authmode: +.Bl -tag -width debug +.It debug +Turns on authentication debugging code. +.It user +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 +without providing a password. +.It valid +Only allow connections when the remote user +can provide valid authentication information +to identify the remote user. +The +.Xr login 1 +command will provide any additional user verification +needed if the remote user is not allowed automatic +access to the specified account. +.It other +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 +.Fl a +.Cm valid . +.It none +This is the default state. +Authentication information is not required. +If no or insufficient authentication information +is provided, then the +.Xr login 1 +program will provide the necessary user +verification. +.It off +This disables the authentication code. +All user verification will happen through the +.Xr login 1 +program. +.El +.It Fl B +Specifies bftp server mode. In this mode, +.Nm telnetd +causes login to start a +.Xr bftp 1 +session rather than the user's +normal shell. In bftp daemon mode normal +logins are not supported, and it must be used +on a port other than the normal +.Tn TELNET +port. +.It Fl D Ar debugmode +This option may be used for debugging purposes. +This allows +.Nm telnetd +to print out debugging information +to the connection, allowing the user to see what +.Nm telnetd +is doing. +There are several possible values for +.Ar debugmode: +.Bl -tag -width exercise +.It Cm options +Prints information about the negotiation of +.Tn TELNET +options. +.It Cm report +Prints the +.Cm options +information, plus some additional information +about what processing is going on. +.It Cm netdata +Displays the data stream received by +.Nm telnetd. +.It Cm ptydata +Displays data written to the pty. +.It Cm exercise +Has not been implemented yet. +.El +.It Fl debug +Enables debugging on each socket created by +.Nm telnetd +(see +.Dv SO_DEBUG +in +.Xr socket 2 ) . +.It Fl edebug +If +.Nm telnetd +has been compiled with support for data encryption, then the +.Fl edebug +option may be used to enable encryption debugging code. +.It Fl h +Disables the printing of host-specific information before +login has been completed. +.It Fl I Ar initid +This option is only applicable to +.Tn UNICOS +systems prior to 7.0. +It specifies the +.Dv ID +from +.Pa /etc/inittab +to use when init starts login sessions. The default +.Dv ID +is +.Dv fe. +.It Fl k +This option is only useful if +.Nm telnetd +has been compiled with both linemode and kludge linemode +support. If the +.Fl k +option is specified, then if the remote client does not +support the +.Dv LINEMODE +option, then +.Nm telnetd +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 by the client sending +.Dv DONT SUPPRESS-GO-AHEAD +and +.Dv DONT ECHO . ) +The +.Fl k +option is most useful when there are remote clients +that do not support kludge linemode, but pass the heuristic +(if they respond with +.Dv WILL TIMING-MARK +in response to a +.Dv DO TIMING-MARK) +for kludge linemode support. +.It Fl l +Specifies line mode. Tries to force clients to use line- +at-a-time mode. +If the +.Dv LINEMODE +option is not supported, it will go +into kludge linemode. +.It Fl n +Disable +.Dv TCP +keep-alives. Normally +.Nm telnetd +enables the +.Tn 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. +.It Fl r Ar lowpty-highpty +This option is only enabled when +.Nm telnetd +is compiled for +.Dv UNICOS. +It specifies an inclusive range of pseudo-terminal devices to +use. If the system has sysconf variable +.Dv _SC_CRAY_NPTY +configured, the default pty search range is 0 to +.Dv _SC_CRAY_NPTY; +otherwise, the default range is 0 to 128. Either +.Ar lowpty +or +.Ar highpty +may be omitted to allow changing +either end of the search range. If +.Ar lowpty +is omitted, the - character is still required so that +.Nm telnetd +can differentiate +.Ar highpty +from +.Ar lowpty . +.It Fl s +This option is only enabled if +.Nm telnetd +is compiled with support for +.Tn SecurID +cards. +It causes the +.Fl s +option to be passed on to +.Xr login 1 , +and thus is only useful if +.Xr login 1 +supports the +.Fl s +flag to indicate that only +.Tn SecurID +validated logins are allowed, and is +usually useful for controlling remote logins +from outside of a firewall. +.It Fl S Ar tos +.It Fl u Ar len +This option is used to specify the size of the field +in the +.Dv utmp +structure that holds the remote host name. +If the resolved host name is longer than +.Ar len , +the dotted decimal value will be used instead. +This allows hosts with very long host names that +overflow this field to still be uniquely identified. +Specifying +.Fl u0 +indicates that only dotted decimal addresses +should be put into the +.Pa utmp +file. +.ne 1i +.It Fl U +This option causes +.Nm telnetd +to refuse connections from addresses that +cannot be mapped back into a symbolic name +via the +.Xr gethostbyaddr 3 +routine. +.It Fl X Ar authtype +This option is only valid if +.Nm telnetd +has been built with support for the authentication option. +It disables the use of +.Ar authtype +authentication, and +can be used to temporarily disable +a specific authentication type without having to recompile +.Nm telnetd . +.El +.Pp +.Nm Telnetd +operates by allocating a pseudo-terminal device (see +.Xr pty 4 ) +for a client, then creating a login process which has +the slave side of the pseudo-terminal as +.Dv stdin , +.Dv stdout +and +.Dv stderr . +.Nm Telnetd +manipulates the master side of the pseudo-terminal, +implementing the +.Tn TELNET +protocol and passing characters +between the remote client and the login process. +.Pp +When a +.Tn TELNET +session is started up, +.Nm telnetd +sends +.Tn TELNET +options to the client side indicating +a willingness to do the +following +.Tn TELNET +options, which are described in more detail below: +.Bd -literal -offset indent +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 +.Ed +.Pp +The pseudo-terminal allocated to the client is configured +to operate in \*(lqcooked\*(rq mode, and with +.Dv XTABS and +.Dv CRMOD +enabled (see +.Xr tty 4 ) . +.Pp +.Nm Telnetd +has support for enabling locally the following +.Tn TELNET +options: +.Bl -tag -width "DO AUTHENTICATION" +.It "WILL ECHO" +When the +.Dv LINEMODE +option is enabled, a +.Dv WILL ECHO +or +.Dv WONT ECHO +will be sent to the client to indicate the +current state of terminal echoing. +When terminal echo is not desired, a +.Dv WILL ECHO +is sent to indicate that +.Tn telnetd +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 +.Dv WONT ECHO +is sent to indicate that +.Tn telnetd +will not be doing any terminal echoing, so the +client should do any terminal echoing that is needed. +.It "WILL BINARY" +Indicates that the client is willing to send a +8 bits of data, rather than the normal 7 bits +of the Network Virtual Terminal. +.It "WILL SGA" +Indicates that it will not be sending +.Dv IAC GA, +go ahead, commands. +.It "WILL STATUS" +Indicates a willingness to send the client, upon +request, of the current status of all +.Tn TELNET +options. +.It "WILL TIMING-MARK" +Whenever a +.Dv DO TIMING-MARK +command is received, it is always responded +to with a +.Dv WILL TIMING-MARK +.ne 1i +.It "WILL LOGOUT" +When a +.Dv DO LOGOUT +is received, a +.Dv WILL LOGOUT +is sent in response, and the +.Tn TELNET +session is shut down. +.It "WILL ENCRYPT" +Only sent if +.Nm telnetd +is compiled with support for data encryption, and +indicates a willingness to decrypt +the data stream. +.El +.Pp +.Nm Telnetd +has support for enabling remotely the following +.Tn TELNET +options: +.Bl -tag -width "DO AUTHENTICATION" +.It "DO BINARY" +Sent to indicate that +.Tn telnetd +is willing to receive an 8 bit data stream. +.It "DO LFLOW" +Requests that the client handle flow control +characters remotely. +.It "DO ECHO" +This is not really supported, but is sent to identify a 4.2BSD +.Xr telnet 1 +client, which will improperly respond with +.Dv WILL ECHO. +If a +.Dv WILL ECHO +is received, a +.Dv DONT ECHO +will be sent in response. +.It "DO TERMINAL-TYPE" +Indicates a desire to be able to request the +name of the type of terminal that is attached +to the client side of the connection. +.It "DO SGA" +Indicates that it does not need to receive +.Dv IAC GA, +the go ahead command. +.It "DO NAWS" +Requests that the client inform the server when +the window (display) size changes. +.It "DO TERMINAL-SPEED" +Indicates a desire to be able to request information +about the speed of the serial line to which +the client is attached. +.It "DO XDISPLOC" +Indicates a desire to be able to request the name +of the X windows display that is associated with +the telnet client. +.It "DO NEW-ENVIRON" +Indicates a desire to be able to request environment +variable information, as described in RFC 1572. +.It "DO ENVIRON" +Indicates a desire to be able to request environment +variable information, as described in RFC 1408. +.It "DO LINEMODE" +Only sent if +.Nm telnetd +is compiled with support for linemode, and +requests that the client do line by line processing. +.It "DO TIMING-MARK" +Only sent if +.Nm telnetd +is compiled with support for both linemode and +kludge linemode, and the client responded with +.Dv WONT LINEMODE. +If the client responds with +.Dv WILL TM, +the it is assumed that the client supports +kludge linemode. +Note that the +.Op Fl k +option can be used to disable this. +.It "DO AUTHENTICATION" +Only sent if +.Nm telnetd +is compiled with support for authentication, and +indicates a willingness to receive authentication +information for automatic login. +.It "DO ENCRYPT" +Only sent if +.Nm telnetd +is compiled with support for data encryption, and +indicates a willingness to decrypt +the data stream. +.Sh ENVIRONMENT +.Sh FILES +.Pa /etc/services +.br +.Pa /etc/inittab +(UNICOS systems only) +.br +.Pa /etc/iptos +(if supported) +.br +.Pa /usr/ucb/bftp +(if supported) +.Sh "SEE ALSO" +.Xr telnet 1 , +.Xr login 1 , +.Xr bftp 1 +(if supported) +.Sh STANDARDS +.Bl -tag -compact -width RFC-1572 +.It Cm RFC-854 +.Tn TELNET +PROTOCOL SPECIFICATION +.It Cm RFC-855 +TELNET OPTION SPECIFICATIONS +.It Cm RFC-856 +TELNET BINARY TRANSMISSION +.It Cm RFC-857 +TELNET ECHO OPTION +.It Cm RFC-858 +TELNET SUPPRESS GO AHEAD OPTION +.It Cm RFC-859 +TELNET STATUS OPTION +.It Cm RFC-860 +TELNET TIMING MARK OPTION +.It Cm RFC-861 +TELNET EXTENDED OPTIONS - LIST OPTION +.It Cm RFC-885 +TELNET END OF RECORD OPTION +.It Cm RFC-1073 +Telnet Window Size Option +.It Cm RFC-1079 +Telnet Terminal Speed Option +.It Cm RFC-1091 +Telnet Terminal-Type Option +.It Cm RFC-1096 +Telnet X Display Location Option +.It Cm RFC-1123 +Requirements for Internet Hosts -- Application and Support +.It Cm RFC-1184 +Telnet Linemode Option +.It Cm RFC-1372 +Telnet Remote Flow Control Option +.It Cm RFC-1416 +Telnet Authentication Option +.It Cm RFC-1411 +Telnet Authentication: Kerberos Version 4 +.It Cm RFC-1412 +Telnet Authentication: SPX +.It Cm RFC-1571 +Telnet Environment Option Interoperability Issues +.It Cm RFC-1572 +Telnet Environment Option +.Sh BUGS +Some +.Tn TELNET +commands are only partially implemented. +.Pp +Because of bugs in the original 4.2 BSD +.Xr telnet 1 , +.Nm telnetd +performs some dubious protocol exchanges to try to discover if the remote +client is, in fact, a 4.2 BSD +.Xr telnet 1 . +.Pp +Binary mode +has no common interpretation except between similar operating systems +(Unix in this case). +.Pp +The terminal type name received from the remote client is converted to +lower case. +.Pp +.Nm Telnetd +never sends +.Tn TELNET +.Dv IAC GA +(go ahead) commands. |