I am trying to configure a SSH Key-Based Authentication and after i created one, i want to copy the SSH Public Key to my server. When i give the following command on git bash : ssh-copy-id username#remote_host , i am asked for a password.
remote_host must be the floating_ip of the VM that i am trying to connect to ?
Which password should i type in ?
It would be really helpful if you could answer my questions.
On the first SSH operation (here an ssh-copy-id), you would need the password of the remote account, in order for the command to add your public kay to said remote user account ~/.ssh/authorized_keys.
Only then subsequent SSH commands would work without asking for password (only passphrase, if your private key is passphrase-protected, and if you have not added the private key to an ssh agent, for caching said passphrase).
Can someone confirm if it's safe to add a private key (.pem) to ~/.ssh/authorized_keys on a computer that will be connecting to a remote server (where the public key will be). I plan on using cat private-key.pem >> ~/.ssh/authorized_keys to add it. I've already changed the permissions on authorized_keys using chmod 600 ~/.ssh/authorized_keys
I've been looking the last hour and all I can see are references to the public key on the remote server. Struggling to find much relevant info on whether the above is safe or not.
I want to do the above so I can add IdentityFile ~/.ssh/authorized_keys to ~/.ssh/config to allow me connect quickly.
Sorry if this is obvious but it's been a while since I've used SSH. Thanks for looking
No. It is not. To the authorized keys, you should put public key!
You can generate public key from private key using ssh-keygen:
ssh-keygen -y -f private-key.pem > public-key.pub
I remember there is a command to send public key to the remote host that I want. I want to use that feature to send one of my public keys to the other host. How can I do that?
You are looking for ssh-copy-id. All this command does is create .ssh and .ssh/authorized_keys and set their permissions appropriately if they don't exist. Then it appends your public key to the end of .ssh/authorized_keys.
You might be looking for this command:
cat ~/.ssh/id_rsa.pub | ssh user#hostname 'cat >> .ssh/authorized_keys'
It appends your public key to the servers authorized keys.
Source
If your server is already set up to not accept password-based login, you might get a Permission denied (publickey) error.
This is another method to send the key, using netcat, so you don't have to authenticate. It will only work over a local network, but you can use port forwarding to do this over the internet.
On the server:
$ nc -l 55555 >> ~/.ssh/authorized_keys
On the client (replace HOSTNAME with the hostname or IP of the server):
$ nc HOSTNAME 55555 < ~/.ssh/id_rsa.pub
You can replace 55555 with an open port of your choice.
source: chat over lan from linux to linux?
Appendix for total newbies: I don't think anyone's mentioned this yet, but if you get ERROR: failed to open ID file '/home/username/.pub': No such file, you need to generate a key first. The Ubuntu help pages have a great guide on Generating RSA Keys.
In other answers there's no example for ssh-copy-id so here it is(first you need to generate the key)
ssh-copy-id user#url
When i ssh to a machine, sometime i get this error warning and it prompts to say "yes" or "no". This cause some trouble when running from scripts that automatically ssh to other machines.
Warning Message:
The authenticity of host '<host>' can't be established.
ECDSA key fingerprint is SHA256:TER0dEslggzS/BROmiE/s70WqcYy6bk52fs+MLTIptM.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'pc' (ECDSA) to the list of known hosts.
Is there a way to automatically say "yes" or ignore this?
Depending on your ssh client, you can set the StrictHostKeyChecking option to no on the command line, and/or send the key to a null known_hosts file. You can also set these options in your config file, either for all hosts or for a given set of IP addresses or host names.
ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no
EDIT
As #IanDunn notes, there are security risks to doing this. If the resource you're connecting to has been spoofed by an attacker, they could potentially replay the destination server's challenge back to you, fooling you into thinking that you're connecting to the remote resource while in fact they are connecting to that resource with your credentials. You should carefully consider whether that's an appropriate risk to take on before altering your connection mechanism to skip HostKeyChecking.
Reference.
Old question that deserves a better answer.
You can prevent interactive prompt without disabling StrictHostKeyChecking (which is insecure).
Incorporate the following logic into your script:
if [ -z "$(ssh-keygen -F $IP)" ]; then
ssh-keyscan -H $IP >> ~/.ssh/known_hosts
fi
It checks if public key of the server is in known_hosts. If not, it requests public key from the server and adds it to known_hosts.
In this way you are exposed to Man-In-The-Middle attack only once, which may be mitigated by:
ensuring that the script connects first time over a secure channel
inspecting logs or known_hosts to check fingerprints manually (to be done only once)
To disable (or control disabling), add the following lines to the beginning of /etc/ssh/ssh_config...
Host 192.168.0.*
StrictHostKeyChecking=no
UserKnownHostsFile=/dev/null
Options:
The Host subnet can be * to allow unrestricted access to all IPs.
Edit /etc/ssh/ssh_config for global configuration or ~/.ssh/config for user-specific configuration.
See http://linuxcommando.blogspot.com/2008/10/how-to-disable-ssh-host-key-checking.html
Similar question on superuser.com - see https://superuser.com/a/628801/55163
Make sure ~/.ssh/known_hosts is writable. That fixed it for me.
The best way to go about this is to use 'BatchMode' in addition to 'StrictHostKeyChecking'. This way, your script will accept a new hostname and write it to the known_hosts file, but won't require yes/no intervention.
ssh -o BatchMode=yes -o StrictHostKeyChecking=no user#server.example.com "uptime"
This warning is issued due the security features, do not disable this feature.
It's just displayed once.
If it still appears after second connection, the problem is probably in writing to the known_hosts file.
In this case you'll also get the following message:
Failed to add the host to the list of known hosts
You may fix it by changing owner of changing the permissions of the file to be writable by your user.
sudo chown -v $USER ~/.ssh/known_hosts
Edit your config file normally located at '~/.ssh/config', and at the beggining of the file, add the below lines
Host *
User your_login_user
StrictHostKeyChecking no
IdentityFile ~/my_path/id_rsa.pub
User set to your_login_user says that this settings belongs to your_login_user
StrictHostKeyChecking set to no will avoid the prompt
IdentityFile is path to RSA key
This works for me and my scripts, good luck to you.
Ideally, you should create a self-managed certificate authority. Start with generating a key pair:
ssh-keygen -f cert_signer
Then sign each server's public host key:
ssh-keygen -s cert_signer -I cert_signer -h -n www.example.com -V +52w /etc/ssh/ssh_host_rsa_key.pub
This generates a signed public host key:
/etc/ssh/ssh_host_rsa_key-cert.pub
In /etc/ssh/sshd_config, point the HostCertificate to this file:
HostCertificate /etc/ssh/ssh_host_rsa_key-cert.pub
Restart the sshd service:
service sshd restart
Then on the SSH client, add the following to ~/.ssh/known_hosts:
#cert-authority *.example.com ssh-rsa AAAAB3Nz...cYwy+1Y2u/
The above contains:
#cert-authority
The domain *.example.com
The full contents of the public key cert_signer.pub
The cert_signer public key will trust any server whose public host key is signed by the cert_signer private key.
Although this requires a one-time configuration on the client side, you can trust multiple servers, including those that haven't been provisioned yet (as long as you sign each server, that is).
For more details, see this wiki page.
Do this -> chmod +w ~/.ssh/known_hosts. This adds write permission to the file at ~/.ssh/known_hosts. After that the remote host will be added to the known_hosts file when you connect to it the next time.
With reference to Cori's answer, I modified it and used below command, which is working. Without exit, remaining command was actually logging to remote machine, which I didn't want in script
ssh -o StrictHostKeyChecking=no user#ip_of_remote_machine "exit"
Add these to your /etc/ssh/ssh_config
Host *
UserKnownHostsFile=/dev/null
StrictHostKeyChecking=no
Generally this problem occurs when you are modifying the keys very oftenly. Based on the server it might take some time to update the new key that you have generated and pasted in the server. So after generating the key and pasting in the server, wait for 3 to 4 hours and then try. The problem should be solved. It happened with me.
The following steps are used to authenticate yourself to the host
Generate a ssh key. You will be asked to create a password for the key
ssh-keygen -f ~/.ssh/id_ecdsa -t ecdsa -b 521
(above uses the recommended encryption technique)
Copy the key over to the remote host
ssh-copy-id -i ~/.ssh/id_ecdsa user#host
N.B the user # host will be different to you. You will need to type in the password for this server, not the keys password.
You can now login to the server securely and not get an error message.
ssh user#host
All source information is located here:
ssh-keygen
For anyone who finds this and is simply looking to prevent the prompt on first connection, but still wants ssh to strictly check the key on subsequent connections (trust on first use), you can set StrictHostKeyChecking to accept-new in ~/.ssh/config, which will do what you're looking for. You can read more about it in man ssh_config. I strongly discourage disabling key checking altogether.
Run this in host server it's premonition issue
chmod -R 700 ~/.ssh
I had the same error and wanted to draw attention to the fact that - as it just happened to me - you might just have wrong privileges.You've set up your .ssh directory as either regular or root user and thus you need to be the correct user. When this error appeared, I was root but I configured .ssh as regular user. Exiting root fixed it.
This is trying to establish password-less authentication. So, if you try to run that command manually once, it will ask to provide the password there. After entering password, it saves that password permanently, and it will never ask again to type 'yes' or 'no'.
For me the reason is that I have wrong permission on ~/.ssh/known_hosts.
I have no write permission on known_hosts file. So it ask me again and again.
In my case, the host was unkown and instead of typing yes to the question are you sure you want to continue connecting(yes/no/[fingerprint])? I was just hitting enter .
I solve the issue which gives below written error:
Error:
The authenticity of host 'XXX.XXX.XXX' can't be established.
RSA key fingerprint is 09:6c:ef:cd:55:c4:4f:ss:5a:88:46:0a:a9:27:83:89.
Solution:
1. install any openSSH tool.
2. run command ssh
3. it will ask for do u add this host like.
accept YES.
4. This host will add in the known host list.
5. Now you are able to connect with this host.
This solution is working now......
I need to create a script that automatically setup a ssh tunnel. I think that a dedicated ssh key without password is a good start but I couldn't find if this is possible and how to do it.
This key should have limited privileges (only set the tunnel up) but I need another private key (with a password) for myself.
Thanks !
Ok, I've found the answer.
First, ssh-keygen -f theNewPrivateKey otherwise it will overwrite the old private key.
Second, ssh -i theNewPrivateKey me#mycomputer the -i option changes the private key used for the authentication.
Now I can try my script.
Edit: how does my new key has limited privileges:
When copying the public key to $HOME/.ssh/authorized_keys2 file of the target computer, I added this:
command="sleep 99999999999" ssh-dss AAAAB3NzaC1kc3MA...
(+ the rest of the key)
Then the only command allowed is to wait forever.
Since the purpose of creating this key was to create a reverse ssh tunnel this should be fine.
I then create the tunnel:
ssh -T -R 7878:localhost:22 -i .ssh/mynewkey me#myhomecomputer
Finally I can log from my home computer:
ssh myworklogin#localhost -p7878
I hope that this does not have security issues. If this is a bad thing, please let me know !
Try the
ssh-keygen
command.
I had a similar situation where i had to synch a server content automatically without having to proivide the password in my robocopy script.
This Link helped me.