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I'm having a problem; git returns this alert:
The authenticity of host 'bitbucket.org (104.192.143.2)' can't be established.
RSA key fingerprint is SHA256:zzXQOXSRBEiUtuE8AikJYKwbHaxvSc0ojez9YXaGp1
Are you sure you want to continue connecting (yes/no)?
When I choose yes, it returns this:
Warning: Permanently added 'bitbucket.org,104.192.143.2' (RSA) to the list of known hosts.
ssh_packet_read: Connection closed
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
What is the problem?
Where must I add the RSA number? Please, I'm desperate. :(
The authenticity of host 'bitbucket.org (104.192.143.2)' can't be established. RSA key fingerprint is SHA256:zzXQOXSRBEiUtuE8AikJYKwbHaxvSc0ojez9YXaGp1 Are you sure you want to continue connecting (yes/no)?
This is normal and it's safe to say yes. ssh is being overly paranoid by asking you to confirm it. You can turn it off by setting StrictHostKeyChecking to no in your ssh config.
Remembering the public key of each server you connect to is a security feature of ssh to protect you from a man-in-the-middle attack. It goes something like this:
The first time you ssh to a host its public key (that's all that SHA256:zzXQ... stuff) is remembered, usually in ~/.ssh/known_hosts.
Every time thereafter ssh will check that the same host is still using the same key. This authenticates that bitbucket.org is still the same server you were talking to the first time.
If the keys don't match it could mean one of two things. First is that the server admin reinstalled their ssh server and forgot to keep the same key. This is common for small sites, but unlikely for something like bitbucket.org.
The second possibility is that the ssh server has been hijacked. It doesn't matter how. One common way is for a rogue DNS server to return their own malicious IP address instead of the real address for bitbucket.org. Common enough on public wifi connections.
As for why it won't connect after confirming, it's right there in the error message.
$ git clone git#bitbucket.org:RobeJablonski/sda-robert.git
Cloning into 'sda-robert'...
conq: repository access denied.
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
The repository exists, that can be verified, so you don't have access rights (neither do I). Bitbucket determines who you are using your ssh key. This means you're not logging in with the right key. It has to be the same key as is associated with your account on BitBucket.
You can find your BitBucket ssh keys in your Bitbucket settings under https://bitbucket.org/account/user//ssh-keys/. Then you have to check if ssh is using that key. You can check what it's using using ssh -v git#bitbucket.org. It will spew out a lot of stuff but you're looking for the last instance of debug1: Offering RSA public key: /Users/blah/.ssh/blah.
Once you find that, check if /Users/blah/.ssh/blah.pub matches what BitBucket thinks your ssh key is. If they don't match, then you'll have to find the matching key and configure ssh to use that key for bitbucket.org.
If you've lost the key, you should change your ssh key on bitbucket.org.
Make sure you have followed below steps in your application server:
Have you created public key:
cd ~/.ssh/
To generate keygeneration:
ssh-keygen
Copy public key value (NOT PRIVATE KEY)
cat ~/.ssh/id_rsa.pub
Install git :
sudo apt install git
ATLASSIAN SETUP :
SETTINGS -> Access keys -> Add key
https://bitbucket.org/compassitesinc/your-repository/admin/access-keys/
Make sure your email address added to the User group (with admin permission)
SETTINGS -> User and group access
Add your email address with admin access
Inside your application root directory clone your repository.
cd /var/www/html/
git clone git#bitbucket.org:organization_name/repo_application.git repo_application
You need to create an SSH key on the machine you wish to connect to GitHub or Bitbucket, then add that key to your online account. You can do this by following this:
https://confluence.atlassian.com/bitbucket/set-up-ssh-for-git-728138079.html
I'm following the ssh github tutorial, and I'm confused about the difference between ssh-add and ssh-agent. The tutorial seems to imply that I will need to enter a password every time I want to use my ssh key, and to stop that, I need to give the key somehow to the ssh agent. However, I am not prompted to enter a password until I run the command ssh-add, and according to the man page
ssh-add adds RSA or DSA identities to the authentication agent, ssh-agent(1).
If the point of an agent is to not have to use a password, why is the agent asking me to create a password?
Here's the code I'm running and my understanding of ssh-add:
ssh-keygen -t rsa -C "your_email#example.com"
# Creates a new ssh key, using the provided email as a label
# Generating public/private rsa key pair. Public key is like a padlock, private key is like a padlock key.
# Enter file in which to save the key (/Users/you/.ssh/id_rsa): [Press enter]
#This is like taking the padlock and they key together and sticking them in a box.
#-------------------------------
ssh-add id_rsa
#ssh-add is like sticking your key in a safe. Instead of putting your keys on a hook in your house, where anyone can pick it up, you put your key in a safe protected by a password.
Enter passphrase (empty for no passphrase): [Type a passphrase]
Enter same passphrase again: [Type passphrase again]
#The safe now has a password.
What is the relationship between ssh-add and ssh-agent? Am I right in assuming the following:
that doing an SSH keygen without an add is sort of like leaving your keys out in your apartment, where anyone you let into your apartment can pick them up, make a copy, and get to all of your stuff?
Doing an SSH keygen with an add is like sticking your keys in a safe with a combination, so that even if you let somebody into your apartment, they still can't get to all of your keys?
That ssh-add is an action taken by a program called ssh-agent?
Assume that you have several Linux machines to manage and you setup ssh login by creating a public private key pair issuing ssh-keygen -t rsa. Assume that you didnt set a passphrase while creating your keys. Now you will copy your public key to all the machines where you want to login by issuing ssh-copy-id -i ~/.ssh/id_rsa.pub user#somehost. Now, with your keys, you will be able to login to all the machines where you copied your keys.
Since you didnt create a passphrase, anyone who gets your private key can login to all the machines where your public key is added. Assume you let your machine to be used by some of your friends and one of him is evil-minded. To prevent this, you set a passphrase to your private key. So whenever you login using your key, you will be prompted for the passphrase and so only you(who knows the passphrase) can login.
But it becomes cumbersome to type the passphrase whenever you login to other machines. So you can give your passphrase to ssh-agent once and it will use it whenever required. You use ssh-add to give your keys to ssh-agent. You can always check what all keys your ssh-agent is managing by issuing ssh-add -l.
I'm getting the standard
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 RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
error message. However, the system (Appworx) that executes the command (sftp I think, not that it matters) is automated and I can't easily accept the new key, even after checking with the third party vendor that it is a valid change. I can add a new shell script that I can execute from the same system (and user), but there doesn't seem to be a command or command-line argument that will tell ssh to accept the key. I can't find anything in the man page or on Google. Surely this is possible?
The answers here are terrible advice. You should never turn off StrictHostKeyChecking in any real-world system (e.g. it's probably okay if you're just playing on your own local home network – but for anything else don't do it).
Instead use:
ssh-keygen -R hostname
That will force the known_hosts file to be updated to remove the old key for just the one server that has updated its key.
Then when you use:
ssh user#hostname
It will ask you to confirm the fingerprint – as it would for any other "new" (i.e. previously unseen) server.
While common wisdom is not to disable host key checking, there is a built-in option in SSH itself to do this. It is relatively unknown, since it's new (added in Openssh 6.5).
This is done with -o StrictHostKeyChecking=accept-new.
WARNING: use this only if you absolutely trust the IP\hostname you are going to SSH to:
ssh -o StrictHostKeyChecking=accept-new mynewserver.example.com
Note, StrictHostKeyChecking=no will add the public key to ~/.ssh/known_hosts even if the key was changed.
accept-new is only for new hosts. From the man page:
If this flag is set to “accept-new” then ssh will automatically add
new host keys to the user known hosts files, but will not permit
connections to hosts with changed host keys. If this flag
is set to “no” or “off”, ssh will automatically add new host keys
to the user known hosts files and allow connections to hosts with
changed hostkeys to proceed, subject to some restrictions.
If this flag is set to ask (the default), new host keys will be
added to the user known host files only after the user has confirmed
that is what they really want to do, and ssh will refuse to
connect to hosts whose host key has changed.
The host keys of known hosts will be verified automatically in all cases.
Why -o StrictHostKeyChecking=no is evil?
When you do not check the host key you might land with an SSH session on a different computer (yes, this is possible with IP Hijacking). A hostile server, which you don't own can be then used to steal a password and all sort of data.
Accepting a new unknown key is also pretty dangerous.
One should only do it if there is an absolute trust in the network or that the server was not compromised.
Personally, I use this flag only when I boot machines in a cloud environment with cloud-init immediately after the machine started.
Here's how to tell your client to trust the key. A better approach is to give it the key in advance, which I've described in the second paragraph. This is for an OpenSSH client on Unix, so I hope it's relevant to your situation.
You can set the StrictHostKeyChecking parameter. It has options yes, no, and ask. The default is ask. To set it system wide, edit /etc/ssh/ssh_config; to set it just for you, edit ~/.ssh/config; and to set it for a single command, give the option on the command line, e.g.
ssh -o "StrictHostKeyChecking no" hostname
An alternative approach if you have access to the host keys for the remote system is to add them to your known_hosts file in advance, so that SSH knows about them and won't ask the question. If this is possible, it's better from a security point of view. After all, the warning might be right and you really might be subject to a man-in-the-middle attack.
For instance, here's a script that will retrieve the key and add it to your known_hosts file:
ssh -o 'StrictHostKeyChecking no' hostname cat /etc/ssh/ssh_host_dsa_key.pub >>~/.ssh/known_hosts
Since you are trying to automate this by running a bash script on the host that is doing the ssh-ing, and assuming that:
You don't want to ignore host keys because that's an additional security risk.
Host keys on the host you're ssh-ing to rarely change, and if they do there's a good, well-known reason such as "the target host got rebuilt"
You want to run this script once to add the new key to known_hosts, then leave known_hosts alone.
Try this in your bash script:
# Remove old key
ssh-keygen -R $target_host
# Add the new key
ssh-keyscan $target_host >> ~/.ssh/known_hosts
You just have to update the current fingerprint that's being sent from server. Just Type in the following and you'll be good to go :)
ssh-keygen -f "/home/your_user_name/.ssh/known_hosts" -R "server_ip"
Just adding the most 'modern' approach.
Like all other answers - this means you are BLINDLY accepting a key from a host. Use CAUTION!
HOST=hostname ssh-keygen -R $HOST && ssh-keyscan -Ht ed25519 $HOST >> "$HOME/.ssh/known_hosts"
First remove any entry using -R, and then generate a hashed (-H) known_hosts entry which we append to the end of the file.
As with this answer prefer ed25519.
Get a list of SSH host IPs (or DNS name) output to a file > ssh_hosts
Run a one-liner to populate the ~/.ssh/known_hosts on the control node (often do this to prepare target nodes for Ansible run)
NOTE: Assume we prefer ed25519 type of host key
# add the target hosts key fingerprints
while read -r line; do ssh-keyscan -t ed25519 $line >> ~/.ssh/known_hosts; done<ssh_hosts
# add the SSH Key('s) public bit to target hosts `authorized_keys` file
while read -r line; do ssh-copy-id -i /path/to/key -f user#$line; done<ssh_hosts
ssh -o UserKnownHostsFile=/dev/null user#host
Add following file
~/.ssh/config
and this in the file as content
StrictHostKeyChecking no
This setting will make sure that ssh will never ask for fingerprint check again.
This should be added very carefully as this would be really dangerous and allow to access all fingerprints.
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......
How can I convince that id_dsa is not stored in ~/.ssh when connecting to one particular host.
The obvious question is why. The answer is this key is more sensitive and needs to be password protected while the other is used for automation.
While this is not a programming problem, I would not be surprised to learn this requires a programming solution.
Theres a handy trick you can use to make it really easy, oddly, I just discussed this 30 minutes ago with a friend.
~/.ssh/config
IdentityFile ~/.ssh/ident/%r#%h
IdentityFile ~/.ssh/id_rsa
IdentityFile ~/.ssh/id_dsa
This makes it really easy to use a fallback pattern, as the options are run through top to bottom.
Then to specify a specific key for "Bob#someHost" you just have to create the file
~/.ssh/ident/Bob#someHost
And it will try that first when logging into that host.
If the file cannot be found, or the key is rejected, it will try the next one, in this case,
~/.ssh/id_rsa
The benefit of this technique is you don't have to add a new entry every time you add another host, all you have to do is create the keyfile in the right place and it does the rest automatically.
In your .ssh/config, set something like:
Host somehost
IdentityFile /path/to/extra_secret_key
I have one host that has IdentityFile set to ~/.ssh/iddsa_aux, but the parameter should accept any path name.
From the ssh man page:
-i identity_file
Selects a file from which the identity (private key) for RSA or
DSA authentication is read. The default is ~/.ssh/identity for
protocol version 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for pro-
tocol version 2. Identity files may also be specified on a per-
host basis in the configuration file. It is possible to have
multiple -i options (and multiple identities specified in config-
uration files).