Merge pull request #7 from IceCodeNew/migrate-terrapin-attack

disable AES CTR ciphers to mitigate the Terrapin attack

sshd_config

@@ -1,11 +1,11 @@
 # Name: K4YT3X Hardened OpenSSH Configuration
 # Author: K4YT3X
 # Date Created: October 5, 2020
-# Last Updated: November 20, 2020
+# Last Updated: December 21, 2023
 
 # Licensed under the GNU General Public License Version 3 (GNU GPL v3),
 #   available at: https://www.gnu.org/licenses/gpl-3.0.txt
-# (C) 2020 K4YT3X
+# (C) 2020-2023 K4YT3X
 
 ########## Binding ##########
 
@@ -96,7 +96,9 @@ PubkeyAuthentication yes
 ########## Cryptography ##########
 
 # explicitly define cryptography algorithms to avoid the use of weak algorithms
-Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
+# AES CTR modes have been removed to mitigate the Terrapin attack
+#   https://terrapin-attack.com/
+Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com
 HostKeyAlgorithms rsa-sha2-512,rsa-sha2-256,ssh-ed25519
 MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com