add: computer title generation for zero-touch deployment

landscape/client/deployment.py

@@ -6,9 +6,14 @@
 
 from landscape import VERSION
 from landscape.client import DEFAULT_CONFIG
+from landscape.client import snap_http
+from landscape.client.snap_utils import get_assertions
+from landscape.client.snap_utils import is_snap
 from landscape.client.upgraders import UPGRADE_MANAGERS
 from landscape.lib import logging
 from landscape.lib.config import BaseConfiguration as _BaseConfiguration
+from landscape.lib.format import expandvars
+from landscape.lib.network import get_fqdn
 from landscape.lib.persist import Persist
 
 
@@ -77,6 +82,12 @@ class Configuration(BaseConfiguration):
 
     DEFAULT_URL = "https://landscape.canonical.com/message-system"
 
+    def __init__(self):
+        super().__init__()
+
+        if is_snap():
+            self.auto_configure_snap()
+
     def make_parser(self):
         """Parser factory for supported options.
 
@@ -189,6 +200,24 @@ def juju_filename(self):
         backwards-compatibility."""
         return os.path.join(self.data_path, "juju-info.json")
 
+    def auto_configure_snap(self):
+        """Automatically configure the client snap."""
+        client_conf = snap_http.get_conf("landscape-client").result
+        auto_enroll_conf = client_conf.get("auto-register", {})
+
+        enabled = auto_enroll_conf.get("enabled", False)
+        configured = auto_enroll_conf.get("configured", False)
+        if not enabled or configured:
+            return
+
+        title = generate_computer_title(auto_enroll_conf)
+        if title:
+            self.computer_title = title
+            auto_enroll_conf["configured"] = True
+            client_conf.update("auto-register", auto_enroll_conf)
+            snap_http.set_conf("landscape-client", client_conf)
+            self.write()
+
 
 def get_versioned_persist(service):
     """Get a L{Persist} database with upgrade rules applied.
@@ -204,3 +233,31 @@ def get_versioned_persist(service):
         upgrade_manager.initialize(persist)
     persist.save(service.persist_filename)
     return persist
+
+
+def generate_computer_title(auto_enroll_conf):
+    assertions = get_assertions("serial")
+    wait_for_serial = auto_enroll_conf.get("wait-for-serial-as", True)
+    if not assertions and wait_for_serial:
+        return
+    serial = assertions[0]["serial"]
+    model = assertions[0]["model"]
+    brand = assertions[0]["brand-id"]
+
+    hostname = get_fqdn()
+    wait_for_hostname = auto_enroll_conf.get("wait-for-hostname", False)
+    if "localhost" in hostname and wait_for_hostname:
+        return
+
+    computer_title_pattern = auto_enroll_conf.get(
+        "computer-title-pattern",
+        "${hostname}",
+    )
+
+    return expandvars(
+        computer_title_pattern,
+        serial=serial,
+        hostname=hostname,
+        model=model,
+        brand=brand,
+    )

landscape/client/snap_utils.py

@@ -0,0 +1,45 @@
+import os
+
+import yaml
+
+from landscape.client import snap_http
+from landscape.client.snap_http import SnapdHttpException
+
+
+def is_snap() -> bool:
+    """Is the landscape-client a snap?"""
+    return os.environ.get("SNAP_REVISION") is not None
+
+
+def get_assertions(assertion_type: str):
+    """Get and parse assertions."""
+    try:
+        response = snap_http.get_assertions(assertion_type)
+    except SnapdHttpException:
+        return
+
+    # the snapd API returns multiple assertions as a stream of
+    # bytes separated by double newlines, something like this:
+    # <assertion1-headers>: <value>
+    # <assertion1-headers>: <value>
+    #
+    # signature
+    #
+    # <assertion2-headers>: <value>
+    # <assertion2-headers>: <value>
+    #
+    # signature
+
+    # extract the assertion headers + their signatures as separate assertions
+    assertions = []
+    result = response.result.decode()
+    if result:
+        sections = result.split("\n\n")
+        rest = sections
+        while rest:
+            headers, signature, *rest = rest
+            assertion = yaml.safe_load(headers)
+            assertion["signature"] = signature
+            assertions.append(assertion)
+
+    return assertions

landscape/client/watchdog.py

@@ -41,6 +41,7 @@
 from landscape.lib.logging import rotate_logs
 from landscape.lib.twisted_util import gather_results
 
+
 GRACEFUL_WAIT_PERIOD = 10
 MAXIMUM_CONSECUTIVE_RESTARTS = 5
 RESTART_BURST_DELAY = 30  # seconds

landscape/lib/format.py

@@ -1,4 +1,5 @@
 import inspect
+import re
 
 
 def format_object(object):
@@ -29,3 +30,35 @@ def format_percent(percent):
     if not percent:
         percent = 0.0
     return f"{float(percent):.02f}%"
+
+
+def expandvars(pattern: str, **kwargs) -> str:
+    """Expand the pattern by replacing the params with values in `kwargs`.
+
+    This implements a small subset of shell parameter expansion and the
+    patterns can only be in the following forms:
+        - ${parameter}
+        - ${parameter:offset} - start at `offset` to the end
+        - ${parameter:offset:length} - start at `offset` to `offset + length`
+    For simplicity, `offset` and `length` MUST be positive values.
+    """
+    regex = re.compile(
+        r"\$\{([a-zA-Z][a-zA-Z0-9]*)(?::([0-9]+))?(?::([0-9]+))?\}",
+        re.MULTILINE,
+    )
+
+    def _replace(match):
+        param = match.group(1)
+        result = kwargs[param]
+
+        offset, length = match.group(2), match.group(3)
+        if offset:
+            start = int(offset)
+            end = None
+            if length:
+                end = start + int(length)
+            return result[start:end]
+
+        return result
+
+    return re.sub(regex, _replace, pattern)

landscape/lib/tests/test_format.py

@@ -1,5 +1,6 @@
 import unittest
 
+from landscape.lib.format import expandvars
 from landscape.lib.format import format_delta
 from landscape.lib.format import format_object
 from landscape.lib.format import format_percent
@@ -63,3 +64,91 @@ def test_format_int(self):
 
     def test_format_none(self):
         self.assertEqual(format_percent(None), "0.00%")
+
+
+class ExpandVarsTest(unittest.TestCase):
+    def test_expand_without_offset_and_length(self):
+        self.assertEqual(
+            expandvars("${serial}", serial="f315cab5"),
+            "f315cab5",
+        )
+        self.assertEqual(
+            expandvars("before:${serial}", serial="f315cab5"),
+            "before:f315cab5",
+        )
+        self.assertEqual(
+            expandvars("${serial}:after", serial="f315cab5"),
+            "f315cab5:after",
+        )
+        self.assertEqual(
+            expandvars("be$fore:${serial}:after", serial="f315cab5"),
+            "be$fore:f315cab5:after",
+        )
+
+    def test_expand_with_offset(self):
+        self.assertEqual(
+            expandvars("${serial:7}", serial="01234567890abcdefgh"),
+            "7890abcdefgh",
+        )
+        self.assertEqual(
+            expandvars("before:${serial:7}", serial="01234567890abcdefgh"),
+            "before:7890abcdefgh",
+        )
+        self.assertEqual(
+            expandvars("${serial:7}:after", serial="01234567890abcdefgh"),
+            "7890abcdefgh:after",
+        )
+        self.assertEqual(
+            expandvars(
+                "be$fore:${serial:7}:after",
+                serial="01234567890abcdefgh",
+            ),
+            "be$fore:7890abcdefgh:after",
+        )
+
+    def test_expand_with_offset_and_length(self):
+        self.assertEqual(
+            expandvars("${serial:7:0}", serial="01234567890abcdefgh"),
+            "",
+        )
+        self.assertEqual(
+            expandvars("before:${serial:7:2}", serial="01234567890abcdefgh"),
+            "before:78",
+        )
+        self.assertEqual(
+            expandvars("${serial:7:2}:after", serial="01234567890abcdefgh"),
+            "78:after",
+        )
+        self.assertEqual(
+            expandvars(
+                "be$fore:${serial:7:2}:after",
+                serial="01234567890abcdefgh",
+            ),
+            "be$fore:78:after",
+        )
+
+    def test_expand_multiple(self):
+        self.assertEqual(
+            expandvars(
+                "${model:8:7}-${serial:0:8}",
+                model="generic-classic",
+                serial="f315cab5-ba74-4d3c-be85-713406455773",
+            ),
+            "classic-f315cab5",
+        )
+
+    def test_expand_offset_longer_than_substitute(self):
+        self.assertEqual(
+            expandvars("${serial:50}", serial="01234567890abcdefgh"),
+            "",
+        )
+
+    def test_expand_length_longer_than_substitute(self):
+        self.assertEqual(
+            expandvars("${serial:1:100}", serial="01234567890abcdefgh"),
+            "1234567890abcdefgh",
+        )
+
+    def test_expand_with_unknown_param(self):
+        with self.assertRaises(KeyError):
+            expandvars("${serial}-${unknown}", serial="01234567890abcdefgh")

setup_client.py

@@ -25,6 +25,7 @@
     "landscape.client.patch",
     "landscape.client.reactor",
     "landscape.client.service",
+    "landscape.client.snap_utils",
     "landscape.client.sysvconfig",
     "landscape.client.watchdog",
 ]