LinuxQuestions.org

LinuxQuestions.org (/questions/)
-   Linux - Newbie (https://www.linuxquestions.org/questions/linux-newbie-8/)
-   -   remote telnet without password (https://www.linuxquestions.org/questions/linux-newbie-8/remote-telnet-without-password-602707/)

shipon_97 11-27-2007 05:50 AM

remote telnet without password
 
Dear friends ,

I want to telnet another server without pressing any "username" and "password" .

I can ftp to another server using following cpmmand :

lflt root:passwd@192.168.10. << !

Like the above way, can I telnet remote server ? If it is possible , then plz help me .. ...

matthewg42 11-27-2007 06:28 AM

You can use ssh instead of telnet, and configure public key authentication. That is the "proper" way to do it.

If you want to incur the wrath of all self-respecting nerds who care about security (and all nerds should care about security), you can write a small script using expect to automate telnet logins and then pass control back to the user.

A typical expect script would look something like this:
Code:

#!/usr/bin/expect

spawn "telnet" "the.host.machine"

expect "Login:"
send "youruser\r"
expect "Password:"
send "yourpassword\r"
expect "Login successful"
interact

There are two main problems with this approach:
  • telnet send the login credentials un-encrypted, so anyone who can see network traffic along the route to the remote host can sniff your password with minimal effort. For this reason, telnet should really be avoided whenever possible.
  • you have to store the username and password in a script. This might seem like no big deal, but it is. Firstly it's a security risk. That password is written to the drive. Someone may get access to the file and read it, or they may get hold of the disk after it is decommissioned, and get the password, even if the drive has been wiped - it is still possible to recover data from "deleted" disks a lot of the time...
    A more immediate problem is maintainability. If you write one script to do this, you will probably write another. And another. Sooner or later you end up with dozens of scripts, scattered all over the place, and then... you need to change your password and it is a nightmare to update everything.

So my advice is do not use expect/telnet. Not that I expect you follow this advice (get it? expect? -nevermind)...

b0uncer 11-27-2007 07:43 AM

I agree, and advice you to stay out of telnet when possible, and moreover never store/write your username/passwords in cleartext to any files nor commands. If it was ok, your Linux would never hide the password you are typing, your Windows would never print asterisks when you're typing a password, and we wouldn't need ssh nor public key authentication.

So, shortly said:
- telnet is easy, but so is ssh - just as easy
- telnet is convenient, you don't need any fancy public keys generated! And anybody who wants can capture the packets you send/receive, and see everything in plain text, your passwords and all
- expect is nice, you can automate your logins - and basically hand over your login information to anyone who is able to break into your account (or in telnet's case just capture the packages with any one of the simple tools freely available on the net, possibly preinstalled on their OS too)
- if you have no valuable information to exchange, you don't need to connect to the other end
- if you do connect to the other end, you have some valuable information you'd like to send or receive, and you wouldn't want everybody to be able to do that; this is why you want to secure the connection, and not use the most unsecure options available
- after configuring ssh it's just as easy to use as telnet (or anything), so there is no sane reason not to do it

matthewg42 11-27-2007 09:07 AM

Quote:

Originally Posted by b0uncer (Post 2972170)
- after configuring ssh it's just as easy to use as telnet (or anything), so there is no sane reason not to do it

You're quite right, and yet so many people are reluctant to use it for some reason. I think the usual reason for this is that they are not the admin on one or both machines, and think that if they ask for ssh or sshd to be installed it will be too much hassle.

The failure of understanding in this case is how much hassle it will be to get another job when their shortcut leads to a security compromise...

blueCow 11-27-2007 04:35 PM

I cannot believe anyone is still using telnet. For one, its not enabled by default on any modern system anymore. So you have to be savvy enough to edit your inetd.conf to enable it. If you know this much you should definitely be using openssh (or the ssh server of your choice). If typing passwords is not your thing, setting up public key authentication is ridiculously easy. It's a total of 7-8 commands.

ernieskaggs 08-30-2017 12:32 PM

Answer the question
 
Jesus, just answer the [removed] question or shut the [removed] up. No one cares about what a proper system administrator should do. The question is how do you enable telenet without a password in linux. No one gives a [removed] about why you shouldn't.

TB0ne 08-30-2017 12:49 PM

Quote:

Originally Posted by ernieskaggs (Post 5753793)
Jesus, just answer the [removed] question or shut the [removed] up. No one cares about what a proper system administrator should do. The question is how do you enable telenet without a password in linux. No one [removed] a shit about why you shouldn't.

Did you happen to notice that this thread had been closed for TEN YEARS before you reopened it? And the question was answered, and a script was even provided to do what they wanted.

And while YOU may not care, many others come here to actually learn to do what's right. Telnet shouldn't be used in the manner asked for, that's why SSH is around.

jeremy 08-30-2017 12:54 PM

@ernieskaggs Additionally, the behavior and language you exhibited in your first post isn't acceptable at LQ. If you'd like to continue participating here, you'll need to refrain from it moving forward.

--jeremy

sundialsvcs 08-30-2017 02:52 PM

So far as I am aware, telnet does not have a "password free" feature. But, ssh does, and it basically does the same thing.

But be aware that you should exclude password-prompting as an option, so that in order to connect you must have an authorized-key and so that ssh will not invite you to enter a password if you don't. To enter, you must possess a key.

(As I have previously mentioned, you should use OpenVPN with tls-auth and unique digital certificates as your outer bastion, allowing reach to "ssh" only if you have successfully passed through the tunnel. This will conceal the existence of the tunnel, presenting to the public a system with "no open ports." Those who possess non-revoked credentials may pass through the secret door easily. All others cannot even discover its existence.)

jefro 08-30-2017 03:09 PM

Old post.

11-27-07, 05:50 AM

jeremy 08-30-2017 03:15 PM

@jefro, this was already pointed out in post #7.

--jeremy

jefro 08-30-2017 06:59 PM

Tried to limit more from posting.

Can you edit post #7?

Pretty sure we know who this new user is. :)

TB0ne 08-31-2017 07:42 AM

Quote:

Originally Posted by jefro (Post 5753945)
Tried to limit more from posting.

Can you edit post #7?

Pretty sure we know who this new user is. :)

What do I need to edit in post #7, exactly?

rtmistler 08-31-2017 12:42 PM

Quote:

Originally Posted by TB0ne (Post 5754079)
What do I need to edit in post #7, exactly?

It's been taken care of and I did not alter your part of the post TB0ne, however please be aware that when you quote a profane post, edits to the original post, which I believe Jeremy did, do not transfer automatically over to the quoted one which resided as part of your post. As a result, a few members cited, quite reasonably, that the offending language needed to be removed from the quote within there.

No biggie, however people should try to be aware of that little detail.

I will add that with a questionable question, such as an incomplete one, or something else, I do find it helpful to quote the poster, because if they edit later, as some people do, it confuses things.

And ernieskaggs, welcome to LQ. Please watch the language in the future, and as you can see, there are open threads sometimes which are years past and updates to them may be helpful, or may not be. Looking forward to seeing you on other discussions which are more current.

TB0ne 08-31-2017 12:43 PM

Quote:

Originally Posted by rtmistler (Post 5754166)
It's been taken care of and I did not alter your part of the post TB0ne, however please be aware that when you quote a profane post, edits to the original post, which I believe Jeremy did, do not transfer automatically over to the quoted one which resided as part of your post. As a result, a few members cited, quite reasonably, that the offending language needed to be removed from the quote within there.

No biggie, however people should try to be aware of that little detail.

I will add that with a questionable question, such as an incomplete one, or something else, I do find it helpful to quote the poster, because if they edit later, as some people do, it confuses things.

And ernieskaggs, welcome to LQ. Please watch the language in the future, and as you can see, there are open threads sometimes which are years past and updates to them may be helpful, or may not be. Looking forward to seeing you on other discussions which are more current.

Ahhhh......you are indeed correct, and my apologies. I should have either quick-replied or edited my post. COMPLETELY missed that.


All times are GMT -5. The time now is 03:11 PM.