Add basics checks for token validity in the autoinstall JSON schema

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

autoinstall-schema.json

@@ -264,7 +264,11 @@
             "type": "object",
             "properties": {
                 "token": {
-                    "type": "string"
+                    "type": "string",
+                    "minLength": 24,
+                    "maxLength": 30,
+                    "pattern": "^C[1-9A-HJ-NP-Za-km-z]+$",
+                    "description": "A valid token starts with a C and is followed by 23 to 29 Base58 characters.\nSee https://pkg.go.dev/github.com/btcsuite/btcutil/base58#CheckEncode"
                 }
             }
         },

examples/autoinstall.yaml

@@ -43,7 +43,8 @@ snaps:
 updates: all
 timezone: Pacific/Guam
 ubuntu-advantage:
-  token: "dummy-token"
+  # Token that passes the basic format checking but is invalid (i.e. contains more than 16 bytes of random data)
+  token: C1NWcZTHLteJXGVMM6YhvHDpGrhyy7
 storage:
   config:
   - {type: disk, ptable: gpt, path: /dev/vdb, wipe: superblock, preserve: false, grub_device: true, id: disk-1}

scripts/runtests.sh

@@ -161,7 +161,7 @@ python3 scripts/check-yaml-fields.py .subiquity/var/log/installer/subiquity-curt
 python3 scripts/check-yaml-fields.py <(python3 scripts/check-yaml-fields.py .subiquity/etc/cloud/cloud.cfg.d/99-installer.cfg datasource.None.userdata_raw) \
         locale='"en_GB.UTF-8"' \
         timezone='"Pacific/Guam"' \
-        ubuntu_advantage.token='"dummy-token"' \
+        ubuntu_advantage.token='"C1NWcZTHLteJXGVMM6YhvHDpGrhyy7"' \
         'snap.commands=[snap install --channel=3.2/stable etcd]'
 grep -q 'finish: subiquity/Install/install/postinstall/install_package1: SUCCESS: installing package1' \
      .subiquity/subiquity-server-debug.log

subiquity/server/controllers/ubuntu_advantage.py

@@ -22,6 +22,10 @@ from subiquity.server.controller import SubiquityController
 
 log = logging.getLogger("subiquity.server.controllers.ubuntu_advantage")
 
+TOKEN_DESC = """\
+A valid token starts with a C and is followed by 23 to 29 Base58 characters.
+See https://pkg.go.dev/github.com/btcsuite/btcutil/base58#CheckEncode"""
+
 
 class UbuntuAdvantageController(SubiquityController):
     """ Represent the server-side Ubuntu Advantage controller. """
@@ -35,6 +39,10 @@ class UbuntuAdvantageController(SubiquityController):
         "properties": {
             "token": {
                 "type": "string",
+                "minLength": 24,
+                "maxLength": 30,
+                "pattern": "^C[1-9A-HJ-NP-Za-km-z]+$",
+                "description": TOKEN_DESC,
             },
         },
     }