update ssh

technology/applications/network/SSH.md

@@ -4,7 +4,9 @@ aliases:
 website: https://www.openssh.com/
 obj: application
 repo: https://github.com/openssh/openssh-portable
+rev: 2024-08-26
 ---
+
 # SSH
 Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line login and remote command execution, but any network service can be secured with SSH.
 
@@ -161,4 +163,30 @@ User-based settings (everything here only applies to `user1`):
 Match User user1
     PasswordAuthentication no
     AllowTcpForwarding yes
-```
+```
+
+#### `authorized_keys`
+The `~/.ssh/authorized_keys` file is used to enable passwordless authentication using SSH keys. You can specify multiple allowed SSH keys one per line. The syntax is:
+```
+[options] key_type key [user@host]
+```
+
+Example:
+```
+ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA7V4+1E...
+```
+
+Common Options:
+- `command="command_to_run"`: Restricts the key to only execute a specific command. The SSH session will automatically execute this command upon login, and the user won't get an interactive shell.
+- `from="hostname_or_ip_address"`: Limits the use of the key to a specific hostname or IP address, or a range of addresses.
+- `no-port-forwarding`: Disables port forwarding for the key.
+- `no-agent-forwarding`: Disables SSH agent forwarding for the key.
+- `no-X11-forwarding`: Disables X11 forwarding for the key.
+- `no-pty`: Disables the allocation of a pseudo-terminal for the key. This means the user won't get an interactive shell session.
+- `permitopen="host:port"`: Restricts port forwarding to a specific host and port.
+- `environment="VAR=value"`: Sets environment variables for the session when the key is used to log in.
+
+Options are comma-seperated if you want to specify multiple.
+
+#### `.ssh/rc`
+The `~/.ssh/rc` file is a script that can be executed automatically whenever an SSH session is established. This can be configured globally with `/etc/ssh/sshrc`.