This morning PyCharm started warning me:
Warning: remote host identification has changed! IT IS
POSSIBLE THAT SOMEONE IS DOING SOMETHING
NASTY! Someone could be eavesdropping on you
right now (man-in-the-middle-attack)! It is also
possible that the host key has just been changed. The
fingerprint for the ssh-ed25519 key sent by the
remote host is
[redacted A]
Do you want to update the key in
/Users/[myhome]/.ssh/known_hosts and resume
connecting?
Then it asks if I want to change ~/Users/[myhome]/.ssh/known_hosts.
The target host is used as an sftp to transfer my code to the remote server. Its name is an alias for two data transfer nodes. I can look at their ssh public keys using ssh-keyscan -t ed25519 alias.remotehost.com and I get a key that matches the one in my known_hosts file. I can also connect to a different remote server, at which time I do not get a warning about changed ssh keys, and ssh-keyscan the original remote host and I get the same keys in known_hosts.
The key that PyCharm says is new does not match any of the now twice confirmed ssh keys. The format of the PyCharm-message-derived key is even totally different from the keys from ssh-keyscan.
What is going on? I don't want to just blast through a security warning, and I'd like some guidance on where to look to see why PyCharm is giving me this warning that I cannot confirm otherwise.
The reason is not necessarily a security issue. Did you double-check your SSH configuration, in particular the known_hosts file used by PyCharm is the same you're checking?
https://man.openbsd.org/ssh_config#UserKnownHostsFile
You may want to take a look at the PyCharm SSH Configurations ... Connection Parameters; for example the different format you're seeing might be related to storing hosts in hash format option (to be confirmed):
https://www.jetbrains.com/help/pycharm/settings-tools-ssh-configurations.html
You can try to recreate a SSH configuration from scratch as described here:
https://www.jetbrains.com/help/pycharm/create-ssh-configurations.html
If you're 100% sure that the key in the known_hosts file is the right one and matches your target server's, this will remove the entry in known_hosts file and you should be again prompted to accept the server key on the next connection:
ssh-keygen -R <host>
(where host is your target server, IP or hostname: "alias.remotehost.com" in your example; you can provide the path for the file using -f <path>)
References
ssh remote host identification has changed
https://stackabuse.com/how-to-fix-warning-remote-host-identification-has-changed-on-mac-and-linux/
https://youtrack.jetbrains.com/issue/CPP-19720
I'm trying to use the private key from my openpgp card from my Debian laptop to a RPi. I followed the different hints found on google, in particular:
extra-socket in ~/.gnupg/gpg-agent.conf
removed it again when founding that this extra socket already will be created in /run/user/<uid>/gnupg
forward this socket using ~/.ssh/config
Host homegear
HostName homegear
RemoteForward ~/.gnupg/S.gpg-agent /run/user/1000/gnupg/S.gpg-agent.extra
changed the order of the both sockets in the RemoteForward line since I'm always confused which one should be the first one
add the following into /etc/ssh/sshd_config of the RPi
StreamLocalBindUnlink yes
reload the gpg-agent on the laptop
open new ssh connection to RPi
But I always get
Warning: remote port forwarding failed for listen path ~/.gnupg/S.gpg-agent
when connecting to the RPi.
openssh on both laptop and RPi is 7.4 (Debian Stretch), gpg is 2.1.18.
Forwarding the agent connect to be used as ssh private key (for connecting to gitlab from RPi) works perfectly, forwarding gpg private key (for signing commits) doesn't. I'm a bit helpless at the moment. Is there anything obviously wrong? Or is there still a problem with forwarding unix domain socket and I need to use the socat workaround?
Thank you!
I've run into exactly the same issue except between two Macs running 10.14.2 and GPG 2.2.11, and the only way I was able to get it to work was to specify the absolute path to the sockets on both ends. :( Having a relative path for either the remote or local socket both failed in various ways, which makes it a bit of a pain if you're connecting as different usernames on various machines.
I was able to work around that by specifying a number of different Match exec blocks in my ~/.ssh/config:
# Source machine is a personal Mac, connecting to another personal Mac on my local network
Match exec "hostname | grep -F .core" Host *.core
RemoteForward /Users/virtualwolf/.gnupg/S.gpg-agent /Users/virtualwolf/.gnupg/S.gpg-agent.extra
# Source machine is a personal Mac, connecting to my Linux box
Match exec "hostname | grep -F .core" Host <name of the host block for my Linux box>
RemoteForward /home/virtualwolf/.gnupg/S.gpg-agent /Users/virtualwolf/.gnupg/S.gpg-agent.extra
# Source machine is my work Mac, connecting to my Linux box
Match exec "hostname | grep -F <work machine name>" Host <name of the host block for my Linux box>
RemoteForward /home/virtualwolf/.gnupg/S.gpg-agent /Users/<work username>/.gnupg/S.gpg-agent.extra
(SSH bits are taken from this answer).
I'm trying to log with ssh on my EC2 instance with a new dual-booted ubuntu 16.04. It's the first time i'm logging in with this client, so there is nothing in .ssh/known_hosts to be deleted, as it is suggested in many other posts like this one.
When I run :
ssh -i "my_key.pem" ubuntu#servername.amazonaws.com
I get:
The authenticity of host 'servername.amazonaws.com (serverip)' can't be established.
ECDSA key fingerprint is SHA256:***************************.
Are you sure you want to continue connecting (yes/no)?
Host key verification failed.
Since i can log with the exac same key from putty on my windows computer,and also from a mac with the same key, this doesnt seem to be key-related.
Anyone out there to help? Thanks in advance!
EDIT: i installed putty on linux, since it was working on windows. Doesnt work either.
nmap localhost gives me port 22 open.
nmap my.ip doesnt.
I tried to ssh to another address, and same results on ssh and putty :(
EDIT2: not a duplicate of BitBucket: Host key authentication failed
Problem solved: it was just me who only pressed Enter on "Are you sure you want to continue connecting (yes/no)?" and not typing yes. Thanks #Kenster
If you do not get any option to continue to connect and it fails permanently, then you could use the command with StrictHostKeyChecking=no option like following :
ssh -i "my_key.pem" ubuntu#servername.amazonaws.com -o StrictHostKeyChecking=no
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I've reinstalled my server and I am getting these messages:
[user#hostname ~]$ ssh root#pong
###########################################################
# WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! #
###########################################################
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
6e:45:f9:a8:af:38:3d:a1:a5:c7:76:1d:02:f8:77:00.
Please contact your system administrator.
Add correct host key in /home/hostname /.ssh/known_hosts to get rid of this message.
Offending RSA key in /var/lib/sss/pubconf/known_hosts:4
RSA host key for pong has changed and you have requested strict checking.
Host key verification failed.
I have tried various solutions that I found on the Internet. My known_hosts file (normally in ~/.ssh/known_hosts) is in /var/lib/sss/pubconf/known_hosts. I've tried to edit it, but it remains in one state. I have installed ipa-client and have Fedora 19. How do I resolve this warning?
All the answers answered so far work only if you do not have Freeipa installed.
The right answer for freeipa in comments below from adrin is here.
Here is the simplest solution:
ssh-keygen -R <host>
For example,
ssh-keygen -R 192.168.3.10
From the ssh-keygen man page:
-R hostname Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts (see the -H option above).
Use
ssh-keygen -R [hostname]
Example with an ip address/hostname would be:
ssh-keygen -R 168.9.9.2
This will update the offending of your host from the known_hosts. You can also provide the path of the known_hosts with -f flag.
I had this same error occur after I recreated a Digital Ocean Ubuntu image. I used the following command with my server IP in place of [IP_ADDRESS]
ssh-keygen -R [IP_ADDRESS]
The sledgehammer is to remove every known host in one fell swoop:
rm ~/.ssh/known_hosts
On Monterey
sudo rm /var/root/.ssh/known_hosts
I come up against this as we use small subnets of short-lived servers from a jump box, and frequently have internal IP address reuse of servers that share the same ssh key.
When you reinstall the server its identity changes, and you'll start to get this message. Ssh has no way of knowing whether you've changed the server it connects to, or a server-in-the-middle has been added to your network to sniff on all your communications - so it brings this to your attention.
Simply remove the key from known_hosts by deleting the relevant entry:
sed '4d' -i /var/lib/sss/pubconf/known_hosts
The 4d is on the account of Offending RSA ...known_hosts:4
The problem is that you've previously accepted an SSH connection to a remote computer and that remote computer's digital fingerprint or SHA256 hash key has changed since you last connected. Thus when you try to SSH again or use github to pull code, which also uses SSH, you get an error. Why? Because you're using the same remote computer address as before but the remote computer is responding with a different fingerprint. Therefore, it's possible that someone is spoofing the computer you previously connected to. This is a security issue.
If you're 100% sure that the remote computer isn't compromised, hacked, being spoofed, etc then all you need to do is delete the entry in your known_hosts file for the remote computer. That will solve the issue as there will no longer be a mismatch with SHA256 fingerprint IDs when connecting.
On Mac here's what I did:
1) Find the line of output that reads RSA host key for servername:port has changed and you have requested strict checking. You'll need both the servername and potentially port from that log output.
2) Back up the SSH known hosts file cp /Users/yourmacusername/.ssh/known_hosts /Users/yourmacusername/.ssh/known_hosts.bak
3) Find the line where the computer's old fingerprint is stored and delete it. You can search for the specific offending remote computer fingerprint using the servername and port from step #1. nano /Users/yourmacusername/.ssh/known_hosts
4) CTRL-X to quit and choose Y to save changes
Now type ssh -p port servername and you will receive the original prompt you did when you first tried to SSH to that computer. You will then be given the option to save that remote computer's updated SHA256 fingerprint to your known_hosts file. If you're using SSH over port 22 then the -p argument is not necessary.
Any issues you can restore the original known_hosts file: cp /Users/yourmacusername/.ssh/known_hosts.bak /Users/yourmacusername/.ssh/known_hosts
As many have already said, use ssh-keygen, i.e.
ssh-keygen -R pong
Also, you may like to consider temporarily turning off host key checking:
ssh -oStrictHostKeyChecking=no root#pong
Works for me!
Error: Offending RSA key in /var/lib/sss/pubconf/known_hosts:4
This indicates you have an offending RSA key at line no. 4
Solution 1:
1. vi /var/lib/sss/pubconf/known_hosts
2. remove line no: 4.
3. Save and Exit, and Retry.
Solution 2:
ssh-keygen -R "you server hostname or ip"
OR
Solution 3:
sed -i '4d' /root/.ssh/known_hosts
This will remove 4th line of /root/.ssh/known_hosts in place(-i).
I used the solution of mockinterface, though the sed -i didn't quite work
I solved it by deleting the line by hand with vim:
sudo vim /var/lib/sss/pubconf/known_hosts
You can use any other text editor you want, but probably you'll need to show your administrative privileges
FINAL Solution!
It is showing due to the stored invalid ECDSA key. So we have to remove the ECDSA key from our master/controller machine by using the below command:
ssh-keygen -R 192.168.0.132
Here 192.168.0.132 is the remote system IP.
Edit /home/hostname /.ssh/known_hosts,and delete the 4 lines, and save it.
Then run ssh root#pong again, you will see message like this:Are you sure you want to continue connecting (yes/no)? yes, just print yes.
Note: If you got some problem, read the hints first, it will help.
The other answers here are good and working, anyway, I solved the problem by deleting ~/.ssh/known_hosts. This certainly solves the problem, but it's probably not the best approach.
updated your ssh key, getting the above message is normal.
Just edit ~/.ssh/known_hosts and delete line 4, as the message pointed you
Offending RSA key in /Users/isaacalves/.ssh/known_hosts:4
or use ssh-keygen to delete the invalid key
ssh-keygen -R "you server hostname or ip"
This is because your remote computer settings have changed. Remove your current keys for that.
vim /root/.ssh/known_hosts
Delete the line of the IP you are connecting.
In my case it happened because I previously had ssh connection with a machine with same ip(say 192.152.51.10) and the system was considering the RSA key(stored in /home/user_name/.ssh/known_hosts) of the previous host which resulted in mismatch.
To resolve this issue, you have to remove previously stored RSA key for the ip 192.152.51.10.
ssh-keygen -f "/home/user_name/.ssh/known_hosts" -R 192.152.51.10
Simple one-liner solution, tested on mac:
sed '/212.156.48.110/d' ~/.ssh/known_hosts > ~/.ssh/known_hosts
Deletes only the target ssh host IP from know hosts.
where 212.156.48.110 is replaced by the target host IP address.
Cause: Happened because the target IP was already known for a different machine due to port forwarding. Deleting the target IP before connecting will fix the issue.
I use PowerShell in Windows 10 for ssh.
My problem was in the Windows directory: C:\Users\youruser\.ssh
Delete the file known_hosts in that directory to forget the old value.
You may also use use File Explorer to locate and delete the file.
If you are trying to connect to running docker container on port 2222 with the command and you get the error
mian#tdowrick2~$ ssh pos#localhost -p 2222
Then to solve this problem, on your local computer (i.e. host machine not container) go to cd ~/.ssh/ and open known_hosts file with text editor. Remove the line starting with [localhost]:2222 and save the file. Now try to ssh again
mian#tdowrick2~$ ssh pos#localhost -p 2222
Error will disappear but you have to do it each time the container restart.
My solution is:
vi ~/.ssh/known_hosts
delete the line that contains your want connected ip.
This is better than delete all of the known_hosts
Remove that the entry from known_hosts using:
ssh-keygen -R *ip_address_or_hostname*
This will remove the problematic IP or hostname from known_hosts file and try to connect again.
From the man pages:
-R hostname
Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts (see the -H option
above).
Sometimes, if for any reason, you need to reinstall a server, when connecting by ssh we will find that you server say that the identification has changed.
If we know that it is not an attack, but that we have reinstated the system, we can remove the old identification from the known_hosts using ssh-keygen:
ssh-keygen -R <host/ip:hostname>
root/.ssh/known_hosts updated.
Original contents retained as /root/.ssh/known_hosts.old
When connecting again we will ask you to validate the new fingerprint:
ssh -l user <host/ip:hostname>
The authenticity of host '<host/ip:hostname>' can't
be established.
RSA key fingerprint is 3f:3d:a0:bb:59:24:35:6d:e5:a0:1a:3f:9c:86:81:90.
Are you sure you want to continue connecting (yes/no)? yes
Use this command:
truncate -s 0 /home/SYSTEM_NAME/.ssh/known_hosts
I had this problem, and the reason is very simple, I have a duplicated IP address to ssh login, so after modify this problem, everthing is solved.
Only client side problem(duplicate key for ip):
Solve variants:
For clear one ip(default port 22):
ssh-keygen -f -R 7.7.7.7
For one ip(non default port):
ssh-keygen -f -R 7.7.7.7:333
Fast clear all ips:
cd ~; rm .ssh/known_hosts
7.7.7.7 - ssh your server ip connect
333 - non standart port
Just do:
cd /home/user/.ssh/ -> here user will be your username, i.e. /home/jon/ for example.
Then
gedit known_hosts & and delete the contents inside it.
Now ssh again, it should work.
I had the same error in my machine, and I clear the known_hosts file, and after that, it works fine.
Simply clear the known_hosts which is present in /home/{username}/.ssh/known_hosts
vi /home/{username}/.ssh/known_hosts
remove every line inside known hosts and exit after that you will be able to login.
OR
run this command
ssh-keygen -R "hostname/ip_address"
SOLUTION:
1- delete from "$HOME/.ssh/known_hosts" the line referring to the host towards which is impossible to connect.
2- execute this command: ssh-keygen -R "IP_ADDRESSorHOSTNAME" (substitute "IP_ADDRESSorHOSTNAME" with your destination ip or destination hostname)
3- Retry ssh connection (if it fails please check permission on .ssh directory, it has to be 700)
My solution on UBUNTU (linux):
1.You have to delete the content from "known_hosts" file which is in "/home/YOUR_USERNAME/.ssh/known_hosts"
2.Generate a new ssh key like "ssh-keygen -t rsa -C "your.email#example.com" -b 4096"
3.Copy-paste your new ssh key in your git repository (gitlab in my case) SSH keys.
It works for me !
AWS EC2.
Find the ip in the message it gives you.
run
vim /home/ec2-user/.ssh/known_hosts
Use the arrow keys to find the ip from the message and click.
dd
This will delete that line then run escape
:wp
This will save then you are good to go.