peter wrote:
Retrieved utelnetd 0.1.11 from here. https://public.pengutronix.de/software/utelnetd/
OK, let's look at this thing. The tarball from the above web site
contains:
hobbit:~/tmp$ tar tzvf ~/Downloads/utelnetd-0.1.11.tar.gz
drwxr-xr-x frogger/frogger 0 2008-08-11 05:44 utelnetd-0.1.11/
-rw-r--r-- frogger/frogger 16430 2003-08-06 11:02 utelnetd-0.1.11/utelnetd.c -rw-r--r-- frogger/frogger 17982 2000-03-06 05:39 utelnetd-0.1.11/LICENSE -rw-r--r-- frogger/frogger 1120 2008-08-11 05:44 utelnetd-0.1.11/Makefile -rw-r--r-- frogger/frogger 2545 2008-08-11 05:43 utelnetd-0.1.11/ChangeLog -rw-r--r-- frogger/frogger 532 2003-08-08 03:26 utelnetd-0.1.11/README
Can't get much simpler than that. I extracted it, then ran "make"
as the instuctions said. The program built with a few warnings:
hobbit:~/tmp/utelnetd-0.1.11$ make
gcc -I. -pipe -DSHELLPATH=\"/bin/login\" -Wall -fomit-frame-pointer -c -o utelnetd.o utelnetd.c
...
gcc -I. -pipe -DSHELLPATH=\"/bin/login\" -Wall -fomit-frame-pointer utelnetd.o -o utelnetd
strip --remove-section=.comment --remove-section=.note utelnetd hobbit:~/tmp/utelnetd-0.1.11$ ls -l utelnetd
-rwxr-xr-x 1 greg greg 22984 Nov 24 21:44 utelnetd*
I won't try to guess how important the warnings are.
The README file does not tell you how to *run* it. It only tells you
how to compile it.
For whatever it's worth, I also found what I'm guessing is a fork of
this project, at <
https://github.com/shalzz/aruba-ap-310/tree/master/utils/utelnetd-0.1.3>.
It credits the pengutronix site as the original source.
Unfortunately, the URL it points to is now gone.
So much for trying to find documentation that way.
In the .c file, there is the following function:
void show_usage(void)
{
printf("Usage: telnetd [-p port] [-i interface] [-l loginprogram] [-d]\n");
printf("\n");
printf(" -p port specify the tcp port to connect to\n");
printf(" -i interface specify the network interface to listen on\n");
printf(" (default: all interfaces)\n");
printf(" -l loginprogram program started by the server\n");
printf(" -d daemonize\n");
printf("\n");
exit(1);
}
I will assume this is the full documentation. There doesn't appear to be
any more.
So, then the question becomes: do you *trust* this program? Do you think
it's safe to run this thing, as root, on your system? And have it
read your username and password, and create a login session for you?
If your answer is "yes", then read that show_usage function's output,
and act accordingly. If you omit the -d option, it should be simple
to write a systemd unit file for this. Or you could go old school
and use the -d option from rc.local. Or anything else you want to do.
Personally, I would never choose to run this program on my system.
Even if I trust the program not to do anything malicious, even assuming it
has no bugs or back doors or anything like that, the thing it's *trying to
do* is just a bad idea. Unencrypted login sessions, with passwords being
sent in the clear over a network, are inherently insecure. This is 2024.
You can run an sshd on the oldest, cheapest computer you can possibly
find that actually powers up. Running a telnet daemon shouldn't even
be considered a real choice.
Anyway, the program compiles just fine on Debian 12. There is no need
to complain to the Debian GCC maintainers that their compiler has a
problem just because you don't know how "make" works.
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