storage: add GET endpoint to generate a recovery key

Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>

subiquity/common/apidef.py

@@ -331,6 +331,10 @@ class API:
             def GET() -> List[Disk]:
                 ...
 
+        class generate_recovery_key:
+            def GET() -> str:
+                ...
+
         class v2:
             def GET(
                 wait: bool = False,

subiquity/models/filesystem.py

@@ -22,6 +22,7 @@ import math
 import os
 import pathlib
 import platform
+import secrets
 import tempfile
 from abc import ABC, abstractmethod
 from typing import List, Optional, Set, Tuple, Union
@@ -2047,3 +2048,10 @@ class FilesystemModel(object):
         if self.reset_partition is not None:
             during.add("efibootmgr")
         return (before, during)
+
+    @staticmethod
+    def generate_recovery_key() -> str:
+        """Return a new recovery key suitable for LUKS encryption. The key will
+        consist of 48 decimal digits."""
+        digits = 48
+        return str(secrets.randbelow(10**digits)).zfill(digits)

subiquity/server/controllers/filesystem.py

@@ -932,6 +932,9 @@ class FilesystemController(SubiquityController, FilesystemManipulator):
             install_minimum_size=minsize,
         )
 
+    async def generate_recovery_key_GET(self) -> str:
+        return self.model.generate_recovery_key()
+
     async def v2_GET(
         self,
         wait: bool = False,