I configured my Raspberry Pi SSH-server to only accept ssh keys when logging in. Really clever I thought, until now.
The thing is, I've added a forced command for one key like this to authorized_keys:
command="cd /home/pi/Sites/" ssh-rsa [bla bla bla] [my comment]
And when trying to log in now, it says just
Connection to MYSITE closed.
What I presume is that the forced command is being run and after that no interactive shell is being launched and therefore the connection is closed. Is there any way to connect anyway and undo the changes I've done to the authorized_keys-file?
What I presume is that the forced command is being run and after that no interactive shell is being launched and therefore the connection is closed.
Exactly.
Is there any way to connect anyway and undo the changes I've done to the authorized_keys-file?
No. This is a feature. If you would be able to override this, it would be going around security policy that you defined (well ... this exactly does not make a lot of sense).
As already pointed out, if you don't have different authorized key, different user with authorized keys or passwords, you will have to get to the remote location and modify that file physically on the SD card.
For the next time, if you want to cd to some directory and start interactive bash, you will need
command="cd /tmp/;bash" s
Related
What I would do is using Putty (or other solution) on Windows to connect to a SAN switch and get results from a command with ssh.
I use Powershell as scripting language and it could be done easily but i don't want to save the password in the script.
I'm looking for a solution to use Putty from command line and set the password not stored in clear in the script.
What I thought is to launch the script with \RUNAS (through a Scheduled task) and pass the actual credentials directly to Putty. (The switch would have the same password as the account used with the Runas). Is that possible?
Or is there any solution using putty with a certificate or something like this?
You may want to consider using key authentication as opposed to a password.
People will say use a password in addition to the key, but if your alternative is storing the password on your PC in a file anyway, someone with access to your machine owns you in either case.. So you just need to generate the keys. The requirement is: no-one but you has access to that key file.
http://www.linuxproblem.org/art_9.html
I'm in the same boat, have to use Windows, but for me www.mingw.org which gives you a shell, and the basic *nix tools - extremely useful for SSH, connect to remote Linux VPS, etc.. Cygwin, of course which is similar, and has an easier tool (setup.exe if I recall) to install new apps. I actually use git-bash with is mingw with git. No-GUIs. I've found this easy to just drop to the mingw shell when I need to use ssh openssl cut awk etc..
So running any remote command using SSH from the command line without third-party programs like Putty, or those with GUIs, etc.. Using the key authentication and offing password auth completely in ssh on the remote device (at least on devices where you have control) is some additional lockdown for the remote device, especially if you're the only one need access it.
Which leaves, scheduling the script. There should be a way to do that via batch file and Windows or within the command line environment.
I'll suggest following options:
use password authentication. Store the text file with password in a file with limited access (some service account) and launch your script under this account's credentials
same as above, but instead of text file use certificate file
write a small program (C#) which uses DPAPI to store the certificate or password in service account-specific store.
combine any of the above with the use of BitLocker/EFS
No options are can protect you from an attacker having admin access to the server, but implementing them will give an increasing (in order of number) headache to someone who will be trying to break it.
The script will be a weak spot in any case, though.
This is probably not the answer you're looking for, but I wouldn't use Putty for this, and would rather communicate with the SSH server directly using SSH.NET library. It's available in both source and binary form, and you could use it from PowerShell too if you like.
Examples: http://sshnet.codeplex.com/wikipage?title=Draft%20for%20Documentation%20page.
Then you'd have a lot of options to store your login credentials securely.
I recommend setting up 2-factor authentication on the ssh machine that you have to communicate with IF you can't use key authentication.
Google's 2 factor authentication can be implemented for ssh and is relatively easy to set up as long as SE linux is disabled...if it isn't disabled, you can add an exception and that would essentially help reduce the risk of compromise and increase security.
I need to copy a file from a remote machine to my local machine and I need to automate it.
I've tried SCP command and it's working, however, I could not automate the part wherein it is asking for the password of the user of the local machine and the remote machine.
Based on this article I can Perform SSH Login Without Password Using ssh-keygen & ssh-copy-id
after following all the instructions written there, I tried to access the remote machine using this
ssh lalala#XXX.XXX.XXX.XXX
it works, it doesnt ask for the password anymore. But when I tried copying a file from that machine using the command below,
scp lalala#XXX.XXX.XXX.XXX:'/a/b/c.txt' lelele#XXX.XXX.XXX.YYY:'/b/c/'
it still asks for the password of the localmachine which is the lelele#XXX.XXX.XXX.YYY
I wonder if I did something wrong? what could it be? is there something wrong with the format of the command?
BTW, im using Centos, and I'm planning to code it using python
If you are copying to your local machine why don't you just do
scp lalala#XXX.XXX.XXX.XXX:'/a/b/c.txt' /b/c/
?
I tried your line on some machine with similar setup and didn't get asked for password; I got an error instead, but this is probably due to differences in our configurations. I tried mine and it worked.
Regarding whether your connection succeeds in the remote machine you could tail this file there:
tail -f /var/log/secure
If you see no error there you can be sure (well, never say always) your layout with the generated keys is working.
In this case I bet you'll see no error there
I think you may have multiple ssh keys and set identies only as yes. If so, please check this answer: https://askubuntu.com/a/999306/398861
I know that we shuld do
ssh user#target
but where do we specify the password ?
Hmm thanks for all your replies.
My requirement is I have to start up some servers on different machines. All servers should be started with one shell script. Well, entering password every time seems little bad but I guess I will have to resort to that option. One reason why I don't want to save the public keys is I may not connect to same machines every time. It is easy to go back and modify the script to change target addresses though.
The best way to do this is by generating a private/public key pair, and storing your public key on the remote server. This is a secure way to login w/o typing in a password each time.
Read more here
This cannot be done with a simple ssh command, for security reasons. If you want to use the password route with ssh, the following link shows some scripts to get around this, if you are insistent:
Scripts to automate password entry
The ssh command will prompt for your password. It is unsafe to specify passwords on the commandline, as the full command that is executed is typically world-visible (e.g. ps aux) and also gets saved in plain text in your command history file. Any well written program (including ssh) will prompt for the password when necessary, and will disable teletype echoing so that it isn't visible on the terminal.
If you are attempting to execute ssh from cron or from the background, use ssh-agent.
The way I have done this in the past is just to set up a pair of authentication keys.
That way, you can log in without ever having to specify a password and it works in shell scripts. There is a good tutorial here:
http://linuxproblem.org/art_9.html
SSH Keys are the standard/suggested solution. The keys must be setup for the user that the script will run as.
For that script user, see if you have any keys setup in ~/.ssh/ (Key files will end with a .pub extension)
If you don't have any keys setup you can run:
ssh-keygen -t rsa
which will generate ~/.ssh/id_rsa.pub (the -t option has other types as well)
You can then copy the contents of this file to ~(remote-user)/.ssh/authorized_keys on the remote machine.
As the script user, you can test that it works by:
ssh remote-user#remote-machine
You should be logged in without a password prompt.
Along the same lines, now when your script is run from that user, it can auto SSH to the remote machine.
If you really want to use password authentication , you can try expect. See here for an example
I have my Hudson CI server setup. I have a CVS repo that I can only checkout stuff via ssh. But I see no way to convince Hudson to check out via ssh. I tried all sorts of options when supplying my connection string.
Has anyone done this? I gotta think it has been done.
If I still remember CVS, I thought you have to set CVS_RSH environment variable to ssh. I suspect you need to set this so that your Tomcat process gets this value inherited.
You can check Hudson system information to see exactly what environment variables the JVM is seeing (and passes along to the build.)
I wrote up an article that tackles this you can find it here:
http://www.openscope.net/2011/01/03/configure-ssh-authorized-keys-for-cvs-access/
Essentially you want to set up passphraseless ssh keys for your build user. This will allow authentication to occur without the need to work out some kind of way to key in your password.
<edit> i.e. Essentially the standard .ssh key client & server install/exchange.
http://en.wikipedia.org/wiki/Secure_Shell#Key_management
for the jenkins user account:
install user key (public & private part) in ~/.ssh (generate it fresh or use existing user key)
on cvs server:
install user key (public part) in ~/.ssh
add to authorized_keys
back on jenkins user account:
access cvs from command-line as jenkins user and accept remote host key (to known_hosts)
* note any time remote server changes key/ip you will need to manually access cvs and accept key again *
</edit>
There's another way to do it but you have to manually log from the build machine to your cvs server and keep the ssh session open so hudson/jenkins can piggyback the connection. Seemed kinda pointless to me though since you want your CI server to be as hands off as possible.
I'm not sure if this is possible or not.
What I'm looking for is a way to tell telnet to use a certain IP address to log into and then run commands where the commands change based on a user's MAC address.
Basically it would be:
tell telnet to use x.x.x.x as the IP to log into and put in the correct username and password
tell telnet to run commands (based on the user's MAC address) that can change based on which user stats you want to see, for example: show macaddress
export the output to notepad
close
expect can do this. If you don't have Tcl but Python, try Pexpect.
If you just want to run one command, use ssh (which allows you to log in, run a command and which will return with the error code of the command, so you can handle errors, too).
If you want to run more than a single command, write a script, use scp to copy that script to the other side and then execute the script with ssh. I've used this approach with great success to build a simple spider that could run a script to gather system information over a large number of hosts.
I think you're looking for expect (it automates these kind of interactive applications). Here is a gratis chapter from the authority on expect, the book "Exploring Expect".
Also you should use SSH if this is over the internet. Telnet is insecure as it's a plain text protocol.
Not to blow my own horn, but you may be able to twist a personal app of mine (note: Sorry, I've removed this.) to this end.
There's currently no documentation other than what is on that page and no public source code (though I've been meaning to get onto that, and will work that out tomorrow if you're interested), but I'd be happy to answer any questions.
That said, any MUD client could be turned to the same use too.