telnetd Manual

Release 1 (November 2, 2022)

Peter Simons <simons@peti.rhein.de>
Steve Holland <sdh4@cornell.edu>

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1 Copyright

GNU GENERAL PUBLIC LICENSE

Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
                         675 Mass Ave, Cambridge, MA 02139, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

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1.1 Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software–to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors’ reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.


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1.2 TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  1. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

    Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

  2. You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

    You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

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    These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

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  9. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
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  11. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

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1.3 NO WARRANTY

BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

@end enumerate
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2 What is telnetd

telnetd is an abbreviation and stands for “telnet daemon”. telnetd is a small program that is called by your TCP/IP protocol stack, namely AmiTCP, and handles incoming telnet requests. Thus it enables you to control your Amiga from another machine using a shell or whatever you prefer.

Naturally, telnet is limited to simple I/O and does not feature windows, gadgets or any other graphical user interface stuff. This means, that you can call programs which do operate in the so called terminal modus and do not open their own window for user input and output. Most Internet related tools do so, for example AmigaElm, Arn, Emacs, etc… If you start a program that relies on any mouse interaction, your machine will hang.

For further details you should consult your AmiTCP handbook regarding telnet.


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3 How to install telnetd

First of all, you’ll need to install AmiTCP properly, but that is not described here, I’m afraid. :-) The installation of telnetd is pretty trivial, though: Just copy the telnetd binary included in this distribution archie into ‘AmiTCP:serv’. Furthermore, copy the fakesr.device into your ‘DEVS:’ directory. Then you’ll have to edit the config file of your internet daemon, which calls telnetd if a request for a telnet session has been received. This file is called ‘AmiTCP:db/inetd.conf’. Go to the last line and insert the following line there:

telnet    stream tcp nowait root   AmiTCP:serv/telnetd

Finally you’ll have to edit your password file, which contains the names of the valid users, their passwords and the shell they should log into. This file is called ‘AmiTCP:db/passwd’. Here is an example entry:

user|passwd|uid|gid|realname|home|shell
simons|2Ln2ZavvleZxU|1|1|Peter Simons|S:|*NewShell * from s:remote-startup

These entries have the follwing meaning:

user

This is the name of the user on our machine. This name must be provided when telnetd prompts for “Login:”.

passwd

This is the DES-encrypted password of the user, which is required to authenticiate. This password should not be sent manually, but only by the passwd-utility from AmiTCP. If you set the passwd to “*” using a text editor, this user will not be prompted for a password but the login is accepted without authenticiation. Usually not a good thing to do… but well, there you have it.

uid
gid
realname

These entries are not used by telnetd, please consult your manual about their meaning.

home

Here you can specify the home directory of this user, usually ‘S:’. The home directory is set by inetd automatically and all Internet related programs will look there for their configuartion and data files, unless they’re configured otherwise. It doesn’t have any direct effect for telnetd, though.

shell

Here you can specify the command that should be issued for this user. Usually this should be a shell. This is done as shown above for the example user simons. The star (“*”) before the “newshell” means that telnetd redirects the standard input and output of the called program itself and sends them over the net to the other machine. If you omit the star, the following things will automatically be appended at the end of the command: “-DEVICE fakesr.device -UNIT 0”. Actually, the number of the UNIT may differ, depending on how many active telnet session your machine has at the moment.

However, this is useful to call programs which are usually issued by getty of the UUCP package, like AxShell and uucico. Usually, you will want to specify the star operator, though. I never needed the other feature myself and it is quite probably, that it does not work rock solid.

If you want to have users that are allowd to receive mail and to FTP, but NOT to telnet into your machine, then you may specify “noshell” at the shell part and telnetd will refuse their login attempt.

The previously mentioned remote-login script need not necessarily exist, I just use it for minor initialisation, for example:

Cd RAM:
alias exit endcli

or

FailAt 99999
rexx:rx rexx:uucp2bjoern
endcli

You may as well omit it and simply call “*newshell *”.


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4 Known problems

telnetd has been tested here quite a lot and it has worked for me pretty well. There are some known problems, though, especially with the VT emulation. Loging in from an Amiga or UNIX machine usually doesn’t make any problems at all, but I have experienced weird stuff when using Windows, MS-DOS or even Napsaterm of AmiTCP. It may have something to do with the fact that telnetd doesn’t emulate or interprete a lot but mostly pipes the incoming characters to the shell and vice versa. Actually, I am pretty damn sure that it has something to do with this fact.

However, I don’t have the time to fix this rather tricky problem at the moment and since telnetd works after all, you might be able to ignore it. :-) It’s nothing serious anyway, it’s just that sometimes a newline too much or too little is displayed. That doesn’t really hurt IMHO.

Another problem is that telnetd wil hang if you call anything that opens a window and since the Amiga is lacking the resource tracking capabilities of, say, UNIX, I am not able to close that application remotely in case the user who logged in quits usins <CTRL-c>. so be careful what you start from your shell!

Last but not least, offering a shell over telnetd is totally insecure. The Amiga does not have any multiuser mechanisms and you’ll will definitely run into problems if someone hacks your account. Maybe MultiUser.Library is a solution for this, but as far as I know does the current version not work together with AmiTCP 4.2. In case this library is updated any time, telnetd will support it quite nicely as it uses the usergroup.library to determine the data of the user who logged in.


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5 The author

If you want to contact me (e-mail preferred), you may use the following addresses:

SnailMail:

Peter Simons, Kaiser-Konrad-Stra�e 80, 53225 Bonn, Germany

Voice:

+49 228 471397

E-Mail:

simons@peti.rhein.de


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5.1 About the author

Congratulations! Amongst the 12.42% of software users who actually bother to read the documentation, you are one of the brightest as you have apparently chosen to read the hidden gem in it: The section “About The Author”.

Disclaimer(1): Although this has not been written by Peter Simons himself, it is not necessarily more objectively than it would have been if he did it himself.

As a first approximation to the author, let us have a look at a text he wrote about himself in a list of systems in his home domain. (It may be of interest to some that his self-description has been 4.46 times as long as the actual technical data of his site.)

I (Peter Simons) was born on Sep 4th 1973 as child of a plain supermodel and a nobel price winner and I had a very nice childhood, although it has always been some kind of nuisance to me that the people used to overlook my really notable IQ because of my extraordinarily handsome appearance.

Note for the reader: I have not known Peter as a child, but you may approximate his look of today by imagining a friendly ice bear with a full beard. (Still a very handsome ice bear, as his ex-girl-friend would probably remark, if she bothered about “all that computer stuff” like this text.)

Although Peter is not really a computer freak - telnetd probably owes its existence to the boring breaks between playing and watching basketball, meeting girls, going to parties, watching M*A*S*H, etc. - the adoption of his nickname “Peti” as site name for his A3000 homebox (peti.rhein.de) symbolizes the fusion of man and machine to a system of high productivity. Furthermore, the natural environment of Peter is best-suited for computer people: The stationer’s shop near his home is the only one I know offering Amigas, Amiga literature and Fish disks just as natural as the more mundane things a stationer sells.

<abrupt and unreasonable break>

This “About The Author” section is shareware. If you want to know how it ends or if you have moulded an opinion about Peter Simons utilizing the information provided herein, send me all your money.

Arno Eigenwillig <arno@yaps.dinoco.de>


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6 Acknowledgments

Steve Holland <sdh4@cornell.edu>

Actually, it is a bit impudent to mention my name at all in this package, because more than 90% of the program is written by Steve. telnetd is mostly based on his package formerly called “TnServ”, which has been available long before I even thought about looking at TCP/IP. Unfortunately, Steve didn’t have the time to support his program any longer and hence, I took the project over.

All of the protocol stuff, and most of the AmiTCP routines were written by him and all I did was to base my efforts on his code. I may have done some work, though, but lets face it: Until I add a GUI, PGP support and a routine that turns lead into gold, this is still his program.

Michael van Elst
Petra Zeidler

Both of you have thought me a whole lot about TCP/IP. Petra helped me to install AS225r2, what I was using back then, when I made my first steps with SLIP. Michael has configured my first Ethernet at home and explained me all that stuff with netmasks, broadcasts, etc… it all sounded like black magic to me. What I know about TCP/IP have I learned from you — and perhaps a bit from Douglas E. Comers book. But really not much.

Bernhard Moellemann

Thanks for organizing the fabulous computer meeting in Karlsruhe in the last two years. These meetings were always a lot of fun a fantastic opportunity to practise the theoretical knowledge one has about networks. Not to mention the opportunity to learn something completely new and unexpected…

Andreas M. Kirchwitz
Kai ‘wusel’ Siering
Henning Schmiedehausen

Thanks for the general spirit of inspiration you three bring to USENET. Oh, and for keeping the net clean of course. :-)

Arno Eigenwillig

This name speaks for itself. (2) Thanks Arno, for all those funny phone calls, for testing how much IP traffic my machine can really handle and for forwarding every bloo… uh… interesting news article you see on the net. :-)

Ms. Sylvia Drautzburg

For giving me so much joy — and so much trouble in the recent months. She’ll probably never read this anyway, but that’s what I said about the stuff I wrote for Judith in LharcUUCP’s manual, too, and it turned out to be pretty wrong. Anyway Sylvia, have a nice life.

I think I’ll better come to an end now, before this manual start to sound like a stupid cracker intro. So many nice people out there.


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Footnotes

(1)

What documentation can get along without disclaimer nowadays?

(2)

I bet many of you americans do regret now, that you never paid attention in your German courses!


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