Ssh agent could not open a connection to your authentication agent windows

While doing ssh-add in Github or Git you might get “could not open a connection to your authentication agent” error on Windows or Ubuntu / Linux machines. We have a quick fix in this guide.

When you are new to Github and try to add ssh-keys, you will very often face this problem.

But since this is mandatory, we need to find a way to fix this.

We will use ssh-agent to fix this with couple of commands.

So let’s first understand why we get an error – could not open a connection to your authentication agent?

Basically what happens is, when you create a new public key and try to add it, there are two points of failure.

1. SSH agent not running

As per Github documentation, this is because the ssh-agent is not running in the background and hence rejects ssh-add command.

To fix this run below command :

$ eval "$(ssh-agent -s)"
> Agent pid 59566

Then simply re-run the add command :

$ ssh-add ~/.ssh/id_rsa

This should work in most cases. However, if you are using fish shell, you might have to handle it differently.

This is because fish shell has different syntax and does not understand bash format.

The below command should work in the case of fish.

eval "ssh-agent -s"

And then because the export command is not recognized by fish, to add keys we will use set -x the command

First set SSH_AUTH_SOCK and SSH_AGENT_PID .

$ set -x SSH_AUTH_SOCK /tmp/ssh-qSWfVCBEZQcc/agent.4858
$ set -x SSH_AGENT_PID 4859

Now run add command.

$ ssh-add ~/.ssh/id_rsa

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2. SSH_AUTH_SOCK not set

You can also encounter this situation when SSH_AUTH_SOCK variable is not set and hence the ssh-add cannot contact an authentication agent.

Verify first that ssh-agent is running on your system by running a command

$ ssh-agent

You should see similar output.

SSH_AUTH_SOCK=/var/folders/65/y74h47ts5sq4f8rdd3z4bny00000gn/T//ssh-NbiggsEgBMbk/agent.33762; export SSH_AUTH_SOCK;
SSH_AGENT_PID=33763; export SSH_AGENT_PID;
echo Agent pid 33763;

Now just run below command to set ssh-agent to the terminal.

eval $(ssh-agent)

If you do not want to do these manual steps every time you open a new shell window, add eval $(ssh-agent)command to your shell profile.

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In the case of bash, it will be ~/.bash_profile.

Let us know if your issue is not solved and still could not open a connection to your authentication agent.

The error “Could not open a connection to your authentication agent” can occur when you do not follow the complete instructions on how to set up your SSH identities. Follow the instructions below to get it right.

Reproduce The Error

If you are following instructions for setting up SSH for Github, for instance, you will need to add your private key to the ssh-agent at some point with this command:

$ ssh-add ~/.ssh/id_rsa

When everything it needs is already in place, this is a simple step that shouldn’t give you any problem. However, many people run into this error:

Could not open a connection to your authentication agent

As the error message has pointed out, the ssh-add command failed to connect to an authentication agent to add your private key.

SSH Authentication Agent

The authentication agent has an important role in the SSH protocol. It acts like the key manager, storing and allowing you to use certificates and keys in a much more convenient manner.

Most SSH client implementations, such as OpenSSH, support asymmetric cryptography. This security scheme employs a pair of keys: public and private. You can (and must) share the public key to the SSH server while keeping the private key secret. This is the gold standard for communication encryption, providing a scalable solution for secure identity authentication.

It is technically possible to use SSH with only passwords. But because of their superior security, most organizations require SSH keys as the authentication method. Whether you use SSH for Git, to connect to a remote server, or to transfer files, your setup process is highly likely to involve these cryptography keys.

OpenSSH can generate these keys for you with ‘ssh-keygen’ if you haven’t. The public key will need to be sent to your SSH server/provider. And in each new login session, you will need to add your private key to SSH so the server can verify your identity.

Since private keys are encrypted at rest, they will need to be decrypted first. The ‘ssh-add’ command can do this for you, but it needs the passphrase you have used to encrypt the key.

You can type this manually every time you establish an SSH connection, but it can get tedious quickly. Keep in mind that your SSH client’s process stops running after you end the remote login session. You will need another tool to save the passphrase if you don’t want to type it repeatedly. That is when the authentication agent ‘ssh-agent’ comes into play.

This program can run in the background and store the decrypted private key in a secure manner. Every time your SSH client needs to identify itself, it can connect to and use this key, eliminating the need for entering the passphrase.

Solution

You will need to start the authentication agent before using ‘ssh-add’ for the first time in your login session:

Linux/macOS

eval $(ssh-agent)

Windows (PowerShell)

Start-Service ssh-agent

Then you can add your private key:

Linux/macOS

ssh-add ~/.ssh/id_rsa

Windows (PowerShell)

ssh-add $env:USERPROFILE\.ssh\id_rsa

The console will ask for the passphrase, which will be used to decrypt your DSA or RSA identity and add it to the authentication agent.

Summary

The message “Could not open a connection to your authentication agent” indicates that you haven’t started the SSH authentication agent during your login session. Because of this, it can’t help your SSH client verify your identity with ‘ssh-add’. Start ‘ssh-agent’ and make sure it is running to solve the problem.

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Could not open a connection to your authentication agent. is an error that occurs when you perform an operation that requires authentication and Secure Socket Shell (SSH) can’t find the authentication agent, “SSH agent“.

This article will teach you why SSH could not find the agent and how you can fix it across different shell environments, from bash to Cygwin. We’ve fine-tuned the entire article to ensure that you get the best learning experience that will fix the error for you. With that said, get your favorite she’ll environment ready, and let’s connect you to your authentication agent.

Why Secure Socket Shell Can’t Connect to Your Authentication Agent?

Secure Socket Shell (SSH) can’t connect to your authentication agent because the agent is not running or you did not start it correctly. As a result, SSH could not find it because starting it correctly will allow SSH to find it via an environment variable (SSH_AUTH_SOCK).

– The Authentication Agent Is Not Running

When the authentication agent is not running, any attempt to use the “SSH-add” command to add a SSH key, like your RSA private key when required, will fail. This happens because adding a private key using the “SSH-add” command requires that the authorization should be running.

That’s because part of the job of this agent is to know the user’s identity and your RSA private key is an example. So, when you call “SSH-add”, SSH will look for this agent and if it can’t find it, it will show an error message that it could not connect to your authentication agent.

– Wrong Startup of the Authentication Agent

Starting the authentication agent is one thing, starting it correctly is another thing and if you don’t get the latter right, you’ll run into an error. That’s because when you start the agent correctly, it will create an environment variable that will tell SSH the socket it can use to connect to the agent.

But if you start it wrongly, the agent will be running but SSH will not find it because the “socket” to find it does not exist. The following bash session is an example:

From the session above, calling “SSH-agent” directly is what we called “starting it wrongly”. Here, the agent will be running but the SSH will not find it, as a result, the “SSH-add” command will result in an error.

How Secure Socket Shell Can Connect to Your Authentication Agent?

Secure Socket Shell can connect to your authentication agent if you use any of the following:

• Start the “SSH-agent” with “eval”
• Use “exec” on the “SSH-agent”
• Create a command alias in “.bashrc”
• Create a “.bashrc” file for Cygwin and MsysGit
• Set SSH_AUTH_SOCK and SSH_AGENT_PID environment variables

– Start the “SSH-agent” With “Eval”

When you start the “SSH-agent” with the “eval” command, SSH will not complain that it could not find the authentication agent. That’s because “eval” will evaluate the “SSH-agent” and it will also create the SSH_AUTH_SOCK environment variable that allows SSH to find the agent. The following is how to start the agent with the “eval” command:

1. Open your terminal.
2. Type the following and press enter: eval `SSH-agent -s`

The completion of the previous steps ensures that you can add your RSA private key with “SSH-add” without a connection error. Mind you, the backticks around “SSH-agent -s” is not an error rather it allows the execution of “SSH-agent -s” and the output is sent to “eval. If you’re on Windows, “eval” will not work but you can do the following:

1. Install Git Bash.
2. Type the following and press enter: eval $(SSH-agent)
3. Use the following if the previous step does not work for you: eval “$(SSH-agent -s)”

Finally, running “SSH-agent” with eval multiple times in the same shell environment will lead to multiple copies of “SSH-agent” running in memory. Some scripts can prevent this, so add the following to your bash “~/.profile” file

– Use “Exec” on the “SSH-agent”

You can use the “exec” command to start the “SSH-agent” if you’re on CentOS and your shell environment is Zshell or Fish Shell. It works like the “eval” command but it will not create a new process of the “SSH-agent”. Now, use the following to run “SSH-agent” on bash using the “exec” command:

1. Open your terminal.
2. Type the following and replace XXXX with the name of your shell: “exec SSH-agent XXXX”. For example, for Fish Shell, the command will be “exec SSH-agent fish”.

Once the agent is running, you can add your RSA key to the SSH connection using “SSH-add”.

– Create a Command Alias in “.Bashrc”

A command alias in your “.bashrc” file will prevent the connection error between SSH and the connection agent. With this alias, you’ll save a few keystrokes and you don’t have to type “eval” every time to start “SSH-agent” because the alias will do this for you automatically. To create this alias, do the following:

1. Launch your terminal and open the “.bashrc” file.
2. Type the following and replace “name_of_your_alias” with your alias: alias name_of_your_alias=’eval `SSH-agent -s`’

Use the alias on the command line and behind the scenes, it will start the “SSH-agent” with eval. So, you’ll not get a connection error when you’re using “SSH-add” to add a private key to the SSH connection.

– Create a “.Bashrc” File for Cygwin and Msysgit

Using a “.bashrc” for Cygwin and MsysGit will solve the Windows could not open a connection to your authentication agent error. The following steps show you how to create the “.bashrc” file that allows you to run the connection agent without an error:

1. Locate your “home” folder and create a “.bashrc” file.
2. Open this file in your favorite editor and paste the following: eval `SSH-agent -s` SSH-add
3. Ensure the previous commands are on different lines. Also, we assume that your RSA key is in “~/.SSH/id_rsa”. If not, write the full path location after “SSH-add”.
4. Confirm that the contents of the config file in “~/.SSH/config” is “ForwardAgent yes”. If not, create the file and update it with the latter.
5. Restart MsysGit and it’ll prompt for your password.

– Set SSH_auth_sock and SSH_agent_pid Environment Variables

If you can set the SSH_AUTH_SOCK and SSH_AGENT_PID variables on Windows, you can use “SSH-add” without calling “SSH-agent” explicitly. The following steps show you how to do this:

1. Open the command prompt and run the following: SSH-agent -s > temp.txt
2. Open the “temp.txt” file and confirm that it has three lines. These are SSH_AUTH_SOCK, SSH_AGENT_PID, and an “echo” statement.
3. Copy the value of SSH_AUTH_SOCK and switch back to the command prompt.
4. Set the SSH_AUTH_SOCK as a variable using the following: set SSH_AUTH_SOCK = the_value_that_you_copied_in_step_3.
5. Open the “temp.txt” file again and copy the number process identification number on line three. The latter should be “echo Agent PID XXXX”. Where “XXXX” is the number that you should copy.
6. Switch back to the command prompt and type the following: set SSH_AGENT_PID=the_number_from_step_5
7. Repeat the same steps for Linux, but replace the “set” command with “export”. The latter is exclusive to Linux.

The completion of the previous steps ensures that you can call “SSH-add” to add your SSH key and you’ll not get a connection error. Finally, if you get another error like the agent has no identities. while using “SSH-add”, ensure that your key exists and you’re not calling “SSH-add” on an empty file.

Conclusion

This article explained why SSH complained that it could not find your authentication agent and how you can fix it. We discussed lots of technical stuff, but remember the following:

• When you start the authentication agent wrongly, SSH will not find it and you’ll get an error if you try “SSH-add” with your RSA private key.
• SSH_AUTH_SOCK is the environment variable that SSH will use to find the authentication agent.
• SSH will connect to your authentication agent if you start the agent using “eval” or “exec” commands.

At this stage, you know how SSH can find your authentication agent and you can use “SSH-add” without an error. Bookmark our article for future reference and share it with your colleagues.