Merged PR 450: Terminal Service Class

## Summary
This PR is the base implementation of the Terminal Service Class, containing the skeleton structure for #2711.

## Test process
Future me's problem - see #2714

## Checklist
- [X] PR is linked to a **work item**
- [X] **acceptance criteria** of linked ticket are met
- [X] performed **self-review** of the code
- [ ] written **tests** for any new functionality added with this PR
- [] updated the **documentation** if this PR changes or adds functionality
- [ ] written/updated **design docs** if this PR implements new functionality
- [X] updated the **change log**
- [X] ran **pre-commit** checks for code style
- [ ] attended to any **TO-DOs** left in the code

Related work items: #2711

src/primaite/simulator/network/hardware/nodes/host/host_node.py

@@ -15,6 +15,7 @@ from primaite.simulator.system.services.arp.arp import ARP, ARPPacket
 from primaite.simulator.system.services.dns.dns_client import DNSClient
 from primaite.simulator.system.services.icmp.icmp import ICMP
 from primaite.simulator.system.services.ntp.ntp_client import NTPClient
+from primaite.simulator.system.services.terminal.terminal import Terminal
 from primaite.utils.validators import IPV4Address
 
 _LOGGER = getLogger(__name__)
@@ -306,6 +307,7 @@ class HostNode(Node):
         "NTPClient": NTPClient,
         "WebBrowser": WebBrowser,
         "NMAP": NMAP,
+        "Terminal": Terminal,
     }
     """List of system software that is automatically installed on nodes."""
 

src/primaite/simulator/network/protocols/ssh.py

@@ -0,0 +1,71 @@
+# © Crown-owned copyright 2024, Defence Science and Technology Laboratory UK
+
+from enum import IntEnum
+from typing import Dict, Optional
+
+from primaite.interface.request import RequestResponse
+from primaite.simulator.network.protocols.packet import DataPacket
+
+# TODO: Elaborate / Confirm / Validate -  See 2709.
+#       Placeholder implementation for Terminal Class implementation.
+
+
+class SSHTransportMessage(IntEnum):
+    """
+    Enum list of Transport layer messages that can be handled by the simulation.
+
+    Each msg value is equivalent to the real-world.
+    """
+
+    SSH_MSG_USERAUTH_REQUEST = 50
+    """Requests User Authentication."""
+
+    SSH_MSG_USERAUTH_FAILURE = 51
+    """Indicates User Authentication failed."""
+
+    SSH_MSG_USERAUTH_SUCCESS = 52
+    """Indicates User Authentication failed was successful."""
+
+    SSH_MSG_SERVICE_REQUEST = 24
+    """Requests a service - such as executing a command."""
+
+    # These two msgs are invented for primAITE however are modelled on reality
+
+    SSH_MSG_SERVICE_FAILED = 25
+    """Indicates that the requested service failed."""
+
+    SSH_MSG_SERVICE_SUCCESS = 26
+    """Indicates that the requested service was successful."""
+
+
+class SSHConnectionMessage(IntEnum):
+    """Int Enum list of all SSH's connection protocol messages that can be handled by the simulation."""
+
+    SSH_MSG_CHANNEL_OPEN = 80
+    """Requests an open channel - Used in combination with SSH_MSG_USERAUTH_REQUEST."""
+
+    SSH_MSG_CHANNEL_OPEN_CONFIRMATION = 81
+    """Confirms an open channel."""
+
+    SSH_MSG_CHANNEL_OPEN_FAILED = 82
+    """Indicates that channel opening failure."""
+
+    SSH_MSG_CHANNEL_DATA = 84
+    """Indicates that data is being sent through the channel."""
+
+    SSH_MSG_CHANNEL_CLOSE = 87
+    """Closes the channel."""
+
+
+class SSHPacket(DataPacket):
+    """Represents an SSHPacket."""
+
+    transport_message: SSHTransportMessage = None
+
+    connection_message: SSHConnectionMessage = None
+
+    ssh_command: Optional[str] = None  # This is the request string
+
+    ssh_output: Optional[RequestResponse] = None  # The Request Manager's returned RequestResponse
+
+    user_account: Optional[Dict] = None  # The user account we will use to login if we do not have a current connection.