feat: implement session management and terminal handling with UI updates and backend support

uvm/images.py

@@ -89,6 +89,11 @@ check_python
 """
 
 
+# The original v4 template shipped this exact agent without an ownership
+# manifest. Recognize that payload when creating from a cached v4 template.
+_V4_TEMPLATE_AGENT_SHA256 = "dfdd4bd6ee3dc06fbdbda6402cb2c54921cff22190d8da889209559800f8b948"
+
+
 def guest_agent_files() -> dict[str, bytes]:
     """The same standalone payload is used by the builder and offline upgrades."""
     return {
@@ -283,7 +288,7 @@ class ImageStore:
         )
         if marker is None or marker.path.read_text(encoding="utf-8") not in {
             "uvm-ubuntu-jammy-v1\n", "uvm-ubuntu-jammy-v2\n", "uvm-ubuntu-jammy-v3\n",
-            "uvm-ubuntu-jammy-v4\n",
+            "uvm-ubuntu-jammy-v4\n", "uvm-ubuntu-jammy-v5\n",
         }:
             return None
         profile = self._read_guest_file(
@@ -374,7 +379,10 @@ class ImageStore:
             existing = self._agent_file(disk, path, files / f"existing-{index}")
             if existing is not None:
                 digest = hashlib.sha256(existing.path.read_bytes()).hexdigest()
-                if digest not in {hashes[path], old_hashes.get(path)}:
+                allowed = {hashes[path], old_hashes.get(path)}
+                if not old_hashes and path == "/usr/lib/uvm/agent.py":
+                    allowed.add(_V4_TEMPLATE_AGENT_SHA256)
+                if digest not in allowed:
                     raise UvmError(f"refusing to overwrite a customized guest agent file: {path}")
             source = files / f"payload-{index}"
             source.write_bytes(content)

uvm/install.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+import hashlib
+import json
 import os
 import shlex
 import shutil
@@ -397,12 +399,17 @@ class Installer:
         machine_id.symlink_to("../../../etc/machine-id")
         for key in (root / "etc/ssh").glob("ssh_host_*_key*"):
             key.unlink()
-        for guest_path, contents in guest_agent_files().items():
+        agent_payloads = guest_agent_files()
+        for guest_path, contents in agent_payloads.items():
             path = root / guest_path.lstrip("/")
             path.parent.mkdir(parents=True, exist_ok=True)
             path.parent.chmod(0o755)
             path.write_bytes(contents)
             path.chmod(0o644)
+        manifest = root / "etc/uvm-agent-files.json"
+        manifest.write_text(json.dumps({name: hashlib.sha256(data).hexdigest() for name, data in agent_payloads.items()},
+                                       sort_keys=True) + "\n", encoding="utf-8")
+        manifest.chmod(0o600)
         self._runner.run(("systemctl", "--root", root, "enable", "ssh.service", "systemd-networkd.service",
                           "uvm-agent.service"), capture=True)
         self._runner.run(("systemctl", "--root", root, "set-default", "multi-user.target"), capture=True)