This guide goes through setting up SSH keys on macOS Mojave 10.14 back to Mac OSX 10.11 and also a secure password-less SSH connection between a local macOS workstation and a remote server also running a Linux variant operating system.
Jul 09, 2019 Public Key Infrastructure (PKI) security is about using two unique keys: the Public Key is encrypted within your SSL Certificate, while the Private Key is generated on your server and kept secret. All the information sent from a browser to a website server is encrypted with the Public Key, and gets decrypted on the server side with the Private Key. Manually generating your SSH key in Windows ›. Right-click in the text field labeled Public key for pasting into OpenSSH authorizedkeys file and choose Select All. Right-click again in the same text field and choose Copy. Importing your SSH key.
The process requires generating a public and private key on the local computer and then adding the public key to the remote servers authorised list. What is great about this is that it allows a password prompt free session, handy for a lot of uses.
First thing that you need to do on your macOS machine is to create a directory that will store your SSH keys. Then you will generate a public and private key for your account, launch the Terminal and punch in some commands:
Create a .ssh Directory
Change to the home directory
Create a SSH directory name .ssh and move into it
Make sure that the file permissions are set to read/write/execute only for the user
Create your private and public key, the blank quotes at the end of the command gives the private key no password, so allowing for passwordless logins!
Change into the .ssh directory and list the contents of that .ssh directory
Thats your SSH keys created, the private key is the id_rsa and the public one is the id_rsa.pub, don’t give out the private one always keep that one only on your local machine.
Sharing the Public Key
Create an authorized_keys in the .ssh directory of the remote computer that you want to connect to.
You can create automatic logins by adding the contents of your public key to the authorized_keys file on the remote device.
To see and copy your public key use the cat command and copy the contents:
On the remote computer if needed, change the permssions on the authorized_keys file to write to add the public key, on a new line paste in your public key, and change permissions back to read only after for security.
Allow write on authorised_keys
Paste the entire id_rsa.pub content with vi or nano into the authorized_keys file, if using nano use the -w flag to not use incorrect line breaks.
If the remote host does not have an “authorized_keys” file simply create one and after the public key is pasted in don’t forget to takeaway write permissions.
Going Both Ways
Public Key Definition
So now when you connect via SSH no password is prompted as the remote computer has your public key which is only decrypted by your private key held in your local .ssh/ directory. If you want the communications to be bilateral then repeat the process in the opposite order between the two.
Now the two computers can securely connect with no password prompting, making it ideal to script between the two for file copies or back ups.
Doing it Quicker
Now instead of typing in
Make an alias in your bash shell you could alias it to
Reload the the shell
Then all you have to type in is the alias
Related
Real talk: passwords are bad. Passwords are notoriously hard to remember, yet easy for attackers to break. A secure password is a long, meaningless string containing a mix of letters, numbers, and symbols. Because they’re so hard to remember, it’s tempting to use the same password everywhere, which means you have to change all your passwords if just one login gets compromised.
Fortunately for us, SSH allows connections to be authenticated using keys. Key-based authentication is a huge improvement over a simple username and password combination.
Instead of a password, you have a pair of matched keys: one public, and one private. Anyone with access to the public key can use it to encrypt information, which can only be decrypted using the corresponding private key.
First, we need some keys to use.
- Did your server provide you with keys?
- Great! Let’s skip down a bit.
- Don’t have any keys?
- Not to worry, we can generate them.
Generate Your Keypair
If you’re using Transmit 5, Code Editor, Transmit for iOS, or Prompt, you can generate keypairs from inside the app.
If you’re on a Mac, we can generate your keypair from the command line. Open a Terminal window and enter the following command:
The $ symbol indicates a command prompt. Everything after the $ is a command to be entered.
Press Return, and you’ll see this:
The first decision to make is where to keep your key, and what to call it. For now we’ll just stick with the defaults.
Hit Return to create a keypair using the default name id_rsa and put it in the .ssh folder in your home folder.
Nerd Stuff! The Finder in macOS keeps that .ssh folder hidden. To see your .ssh folder in the Finder, press Command+Shift+G, then enter ~/.ssh. Also! The tilde (~) is filesystem shorthand for your user’s home folder. So when we say ~/.ssh, that means /Users/YOU/.ssh.
Next you can opt to encrypt your private key with a passphrase.
The passphrase is an extra layer of security on your private key. With a passphrase, not only does someone need to gain access to your private key, they also need your passphrase in order to make use of it.
To set a passphrase, enter it here.
To skip setting a passphrase, hit Return without typing anything.
Whether you set a passphrase or not, you’ll be asked to confirm it. Enter the passphrase again, or just press Return.
Your keypair has been generated.
Note that the private key is called “id_rsa” and the public key is “id_rsa.pub”, and they’re both in a folder called “.ssh” in your home folder.
The Public Key
The public key (the one ending in .pub) goes on the remote server. If your server administrator provided you with a key to use, they’ve likely already taken care of this for you. If not, you’ll need to find a way to put your public key on the server.
In most cases, this means connecting with a username and password. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and append the entire contents of your public key onto the end of the file.
Your public key is a text file with a single long line. Enter this command to see it:
It should look like this:
Note:This is just an example. This is not a valid public key.
The Private Key
The private key stays private. The .ssh folder in your home folder is a good place to keep it. Enter this command to see it:
Your private key should look something like this:
Note:This is just an example. This is not a valid private key.
The ~/.ssh/config File
Along with your public and private keys, your .ssh folder can contain a file called config containing settings and preferences relating to your keys and servers. There are too many possible options to list here, and not every possibility is supported (or even practical) in every app.
You may need to create the config file if it doesn’t already exist.
As a basic example, here’s what you’d put in your config so that the key called exampleKey is used when connecting with the username user to the server example.com.
This is a great way to tell apps which key file goes with which server, especially if you use non-standard names for your keys, you keep your keys outside of ~/.ssh, or if you use passphrase-encrypted keys, which Coda and Transmit cannot validate.
You probably won’t ever need to touch your config file. There are a handful of special-snowflake situations where setting an option in the config file is the only way to make it work. Your server administrator can guide you if problems arise.
Though all of our apps offer some level of support for key-based authentication, there are some differences from app to app in how keys are handled.
Supported Formats
Generally, our apps support ECDSA, RSA and DSA keys in PEM format.
Transmit 5 and Prompt 2 have additional support for Ed25519, ECDSA, RSA and DSA keys in OpenSSH format.
OpenSSH has deprecated the DSA public key algorithm due to its inherent weakness. DSA keys are disabled by default in macOS Sierra. We strongly recommend against using DSA keys if possible.
PuTTY/PPK
Keys in the PuTTY format (PPK) are not supported. If you have a PuTTY key, you can convert it to OpenSSH/PEM by following these instructions under the Dealing with Private Keys in Other Formats section.
The Present
We’re using an SSH library based on libssh2 and OpenSSL. This library, used in Transmit 5, Coda 2, Prompt, Transmit iOS, and Code Editor, currently supports the following:
- KexAlgorithms
- diffie-hellman-group-exchange-sha1
- diffie-hellman-group14-sha1
- diffie-hellman-group1-sha1
- diffie-hellman-group-exchange-sha256
- ecdh-sha2-nistp256
- ecdh-sha2-nistp384
- ecdh-sha2-nistp521
- Ciphers
- aes128-ctr
- aes192-ctr
- aes256-ctr
- aes128-cbc
- aes192-cbc
- aes256-cbc
- blowfish-cbc
- arcfour
- arcfour128
- cast128-cbc
- 3des-cbc
- MACs
- sha2-512-etm@openssh.com
- sha2-512
- sha2-256-etm@openssh.com
- sha2-256
- sha1
- sha1 96
- ripemd160
Beyond what libssh2 includes, we’ve added support for ECDSA and EtM. We’ll continue to refine and improve this library, and push our changes to the upstream libssh2 project.
Legacy releases
Transmit 4 and Coda 1 used the OpenSSH library built-in to Mac OS X. This means key support in Transmit 4 and Coda 1 is limited to what the OS-provided library supports.
Host Key Verification
The first time you connect to a server, we keep a local copy of the key the server uses to identify itself. On future connections, we can use this stored key to verify that the server we’re connecting to now is the same one we’ve connected to before. Without host key verification, we’d be vulnerable to man-in-the-middle attacks.
If an app warns that the host key has changed, it means this server’s key looks different from the key we stored the first time we connected to this server. If this is unexpected, you should reject the changed key, cease connecting to this server, and contact your server administrator.
In Transmit (version 5 and later), Code Editor and Prompt, the host key fingerprint is displayed the first time you connect to a new server.
In Coda, Transmit iOS, and older versions of Transmit, the host key is blindly accepted on first connection. This is generally fine, but it’s something to be aware of if you’re on an untrusted local network.
To view the host key fingerprint used in Coda or Transmit, open the file ~/.ssh/known_hosts and find the line that corresponds to your server. If you need to reset the host key for a server, just remove the entire line for that server from the known_hosts file.
In Code Editor and Prompt, you can view the fingerprint at any time from the server settings.
Advanced Features
Prompt and the terminal in Code Editor support agent forwarding. Coda, Transmit, and Transmit iOS do not.
Port forwarding, X11 forwarding, and ProxyCommand are not currently supported.
App-Specific Notes
Coda
In the Server pane of Coda’s Site configuration sheet, there is a button with a key icon to the right of the password field. This button opens a file picker that allows you to choose a private key to use when connecting to this server. Coda automatically attempts to use any keys it finds in your .ssh folder.
When choosing a key via this button, Coda will attempt to verify the format of the key to make sure that it’s valid and supported.
If your key is encrypted with a passphrase, Coda’s key-chooser will be unable to verify it. See the config file workaround above.
If you’ve specified an encrypted key for use with this server in your config file, you can leave the key button alone and put the passphrase in Coda’s password field.
The Terminal, Source Control, and MySQL functions in Coda also support keys, but you will need to add your key to the config file.
Transmit 5
In the latest version of Transmit we’ve added the ability to store keys right in Transmit itself. Additionally, Transmit 5 still supports keys defined in in your config file.
For a more comprehensive overview of the many ways Transmit 5 can be configured to use key-based authentication please see Transmit 5 SFTP Authentication.
Transmit 4
When connecting to an SFTP server, there is a button with a key icon to the right of the password field. This button works in much the same way as the same button in Coda: it opens a file picker that allows you to choose a private key for use when connecting to this server. Transmit will automatically attempt to use any keys it finds in your .ssh folder.
When choosing a key via this button, Transmit will attempt to verify the format of the key to make sure that it’s valid and supported.
If your key is encrypted with a passphrase, Transmit’s key-chooser will be unable to verify it. See the config file workaround above.
If you’ve specified an encrypted key for use with this server in your config file, you can leave the key button alone and put the passphrase in Transmit’s password field.
Prompt
When creating a new server connection, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.
Important! If you want to use a key with a passphrase for agent forwarding, you must enter the passphrase when adding the key to the server connection.
You can view, import, and create keys in the Keys pane of Prompt’s Settings.
To add a key for use in Prompt, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.
Generate New Key
Pgp Key
To generate a new key, tap the + button on the Keys pane of Prompt’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type, and size. Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.
Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.
Copy from Clipboard
To import a key from the iOS Clipboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the Clipboard, go to Prompt’s Settings, tap Keys, then tap the + button and choose Copy from Clipboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Prompt will import the key for you.
Import from iTunes
Use iTunes File Sharing to import your private key. Note that Prompt does not support importing arbitrary files via iTunes File Sharing; this only works for keys.
Agent Forwarding
To enable agent forwarding in Prompt, toggle the Agent Forwarding switch in the Server settings. If your key uses a passphrase, you’ll need to have entered it when you added the key to the server entry.
Code Editor
When creating a remote server connection in a new Site, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.
Important! If you want to use a key with a passphrase for agent forwarding, you must enter the passphrase when adding the key to the server connection.
You can view, import, and create keys in the Keys pane of Coda’s Settings.
To add a key for use in Coda, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.
Generate New Key
To generate a new key, tap the + button on the Keys pane of Coda’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type, and size. Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.
Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.
Import From Pasteboard
To import a key from the iOS Pasteboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the pasteboard, go to Coda’s Settings, tap Keys, then tap the + button and choose Import from Pasteboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Coda will import the key for you.
Import from Local
Use this option to import a private key from the Local file storage on your iOS device. One example where this is useful is if you’ve got your private key on your Mac. Use Coda to connect to your Mac on the same local network, then transfer the key into Coda’s Local file storage. Once the key is in Coda’s local file storage, it can be imported for use.
Import from iTunes
Use iTunes File Sharing to import your private key. Note that Coda does not support importing arbitrary files via iTunes File Sharing; this only works for keys.
Agent Forwarding
To enable agent forwarding in Code Editor, toggle the Agent Forwarding switch in the Terminal pane of the Site’s settings. If your key uses a passphrase, you’ll need to have entered it when you added the key to the server entry.
Transmit iOS
When creating a new server connection, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.
You can view, import, and create keys in the Keys pane of Transmit’s Settings.
To add a key for use in Transmit, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.
Generate New Key
To generate a new key, tap the + button on the Keys pane of Transmit’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type (we recommend RSA), and size (we recommend 2048 or 4096). Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.
Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.
Import From Pasteboard
To import a key from the iOS Pasteboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the pasteboard, go to Transmit’s Settings, tap Keys, then tap the + button and choose Import from Pasteboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Transmit will import the key for you.
Import from Local
Use this option to import a private key from the Local file storage on your iOS device. One example where this is useful is if you’ve got your private key on your Mac. Use Transmit to connect to your Mac on the same local network, then transfer the key into Transmit’s Local file storage. Once the key is in Transmit’s local file storage, it can be imported for use in Transmit.
Import from iTunes
Use iTunes File Sharing to import your private key. Note that Transmit does not support importing arbitrary files via iTunes File Sharing; this only works for keys.
Troubleshooting
Why does it say my key is not in a supported format?
The most common reason you’d see this error is if you select a passphrase-encrypted key via the key chooser button in either Coda or Transmit on macOS. Coda and Transmit want to validate the key before letting you use it, but the encryption prevents that from happening. (Admittedly, this is not ideal, and should be improved.)
As a workaround, add your key to the ~/.ssh/config file, skip the key button altogether, and put the passphrase in the password field.
Private Key
You’ll also get this error if you use a key in an unsupported format, such as a PuTTy key. Make sure you’re using a supported key.
Why can’t I import my key from the pasteboard?
Most of the time this is a format issue. Are you sure you’re using a supported key?
Double-check that it’s the private key, not the public key. They look different (see the abovesections on each), so it should be easy to tell.
One particularly nasty gotcha to watch out for involves the text substitution feature of macOS. For example, let’s say you copy and paste the contents of your private key somewhere easily accessible from your iOS device. You might notice that macOS has helpfully changed runs of hyphens (----) into em-dashes (––).
Your private key used to look like this:
But it now looks like this:
It’s a subtle difference, but it’s enough to break your key. Watch out!