SSH

Unable to negotiate with 1domain.com port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss

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This error for ssh can be solved with the following information. -Reattempt your SSH connection, adding the following to your command line: -oHostKeyAlgorithms=+ssh-rsa ie. or You can also try modifying the local(your computer) SSH configuration to add the below values to make this change permanent. -Type sudo nano ~/.ssh/config, then enter your administrative password if … Read more

SSH key that uses Ed25519 algorithm

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To test, you will need a client and test server. The client server is where we generate the keys. When we generate keys, there will be a private key and a public key. Then we copy the public key to the test server. When we ssh to the test server, the private key we have … Read more

Generate ssh keys on linux and use with PuTTY on Windows

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Log into the Linux server as the user you are going to use to connect with ssh. Generate the key.

ssh-keygen -t rsa -b 4096 -C "email@domain.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user/.ssh/id_rsa.
Your public key has been saved in /home/user/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:3/dDa9R+zzDpGNt/EU9Jusj/snbKt3+B8F+ULnxXtWk email@domain.com
The key's randomart image is:
+---[RSA 4096]----+
|                 |
|               ..|
|              o *|
|           . . E+|
|        S . = =o=|
|         . + * O=|
|          . + @.*|
|            .@ %=|
|            ++@+#|
+----[SHA256]-----+

Now copy the id_rsa key to your Windows desktop. This can be done by copying and pasting the contents of the file or using an SCP client such as PSCP which is supplied with the PuTTY install or FileZilla.

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How To Create SSH Keys With PuTTY to Connect to CentOS7

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Generating OpenSSH-compatible Keys for Use with PuTTY

To generate a set of RSA keys with PuTTYgen:

  1. Start the PuTTYgen utility, by double-clicking on its .exe file;
  2. For Type of key to generate, select RSA;
  3. In the Number of bits in a generated key field, specify either 2048 or 4096 (increasing the bits makes it harder to crack the key by brute-force methods);
  4. Click the Generate button;
  5. Move your mouse pointer around in the blank area of the Key section, below the progress bar (to generate some randomness) until the progress bar is full;
  6. A private/ public key pair has now been generated;
  7. In the Key comment field, enter any comment you’d like, to help you identify this key pair, later (e.g. your e-mail address; home; office; etc.) — the key comment is particularly useful in the event you end up creating more than one key pair;
  8. Optional: Type a passphrase in the Key passphrase field & re-type the same passphrase in the Confirm passphrase field (if you would like to use your keys for automated processes, however, you should not create a passphrase);
  9. Click the Save public key button & choose whatever filename you’d like (some users create a folder in their computer named my_keys);
  10. Click the Save private key button & choose whatever filename you’d like (you can save it in the same location as the public key, but it should be a location that only you can access and that you will NOT lose! If you lose your keys and have disabled username/password logins, you will no longer be able log in!);
  11. Right-click in the text field labeled Public key for pasting into OpenSSH authorized_keys file and choose Select All;
    Right-click again in the same text field and choose Copy.
  12. NOTE: PuTTY and OpenSSH use different formats for public SSH keys. If the SSH Key you copied starts with “—- BEGIN SSH2 PUBLIC KEY …”, it is in the wrong format. Be sure to follow the instructions carefully. Your key should start with “ssh-rsa AAAA ….”
  13. Save The Public Key On The Server

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Log in with an SSH private key on Linux

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Using a text editor, create a file in which to store your private key. This example uses the file private_key.txt. To edit the file in nano, type the following command # nano deployment_key.txt Paste the private key into the file. Be sure to include the BEGIN and END lines. —–BEGIN RSA PRIVATE KEY—– MIIEowIBAAKCAQEAx9ODcgSZFhPnZmW/VGWy/bXLKFBhOoTP9k4dhcJq17ZuG9KB … … Read more

How can I keep my SSH sessions Alive

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Here is how to keep your ssh session from freezing and how to keep ssh alive. Edit your ssh config file. Change to the following variables # nano /etc/ssh/sshd_config TCPKeepAlive yes ClientAliveInterval 60 ClientAliveCountMax 10000 Then, restart ssh On CentOS: # service sshd restart Stopping sshd: [ OK ] Starting sshd: [ OK ] TCPKeepAlive … Read more

How to Secure SSH with Google Authenticator’s Two-Factor Authentication

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Source: http://www.howtogeek.com/121650/how-to-secure-ssh-with-google-authenticators-two-factor-authentication/ Also, for CentOS: http://www.tecmint.com/ssh-two-factor-authentication/ Want to secure your SSH server with easy-to-use two-factor authentication? Google provides the necessary software to integrate Google Authenticator’s time-based one-time password (TOTP) system with your SSH server. You’ll have to enter the code from your phone when you connect.

Change OpenSSH Port CentOS

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Want to change the ssh port for ssh? Here is a good tutorial. (Note: If you are making these changes – ssh to the server and keep the terminal open as you make the changes. Test with a new terminal. This way if something is amiss – you are not locked out.) Edit /etc/ssh/sshd_config, enter: … Read more