generate contents for ovf-env.xml when provisioning via IMDS (canonic…

…al#959)

Azure Linux Agent (WaLinuxAgent) waits for the ovf-env.xml file 
to be written by cloud-init when cloud-init provisions the VM. This 
file is written whenever cloud-init reads its contents from the 
provisioning ISO. 
With this change, when there is no provisioning ISO, 
DataSourceAzure will generate the ovf-env.xml file based on the 
metadata obtained from Azure IMDS.

cloudinit/sources/DataSourceAzure.py

@@ -45,7 +45,8 @@
     is_byte_swapped,
     dhcp_log_cb,
     push_log_to_kvp,
-    report_failure_to_fabric)
+    report_failure_to_fabric,
+    build_minimal_ovf)
 
 LOG = logging.getLogger(__name__)
 
@@ -540,6 +541,18 @@ def crawl_metadata(self):
             )
             crawled_data['metadata']['disable_password'] = imds_disable_password  # noqa: E501
 
+        if metadata_source == 'IMDS' and not crawled_data['files']:
+            try:
+                contents = build_minimal_ovf(
+                    username=imds_username,
+                    hostname=imds_hostname,
+                    disableSshPwd=imds_disable_password)
+                crawled_data['files'] = {'ovf-env.xml': contents}
+            except Exception as e:
+                report_diagnostic_event(
+                    "Failed to construct OVF from IMDS data %s" % e,
+                    logger_func=LOG.debug)
+
         # only use userdata from imds if OVF did not provide custom data
         # userdata provided by IMDS is always base64 encoded
         if not userdata_raw:

cloudinit/sources/helpers/azure.py

@@ -344,6 +344,40 @@ def http_with_retries(url, **kwargs) -> str:
     raise exc
 
 
+def build_minimal_ovf(
+        username: str,
+        hostname: str,
+        disableSshPwd: str) -> bytes:
+    OVF_ENV_TEMPLATE = textwrap.dedent('''\
+        <ns0:Environment xmlns:ns0="http://schemas.dmtf.org/ovf/environment/1"
+         xmlns:ns1="http://schemas.microsoft.com/windowsazure"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+          <ns1:ProvisioningSection>
+            <ns1:Version>1.0</ns1:Version>
+            <ns1:LinuxProvisioningConfigurationSet>
+              <ns1:ConfigurationSetType>LinuxProvisioningConfiguration
+              </ns1:ConfigurationSetType>
+              <ns1:UserName>{username}</ns1:UserName>
+              <ns1:DisableSshPasswordAuthentication>{disableSshPwd}
+              </ns1:DisableSshPasswordAuthentication>
+              <ns1:HostName>{hostname}</ns1:HostName>
+            </ns1:LinuxProvisioningConfigurationSet>
+          </ns1:ProvisioningSection>
+          <ns1:PlatformSettingsSection>
+            <ns1:Version>1.0</ns1:Version>
+            <ns1:PlatformSettings>
+              <ns1:ProvisionGuestAgent>true</ns1:ProvisionGuestAgent>
+            </ns1:PlatformSettings>
+          </ns1:PlatformSettingsSection>
+        </ns0:Environment>
+        ''')
+    ret = OVF_ENV_TEMPLATE.format(
+        username=username,
+        hostname=hostname,
+        disableSshPwd=disableSshPwd)
+    return ret.encode('utf-8')
+
+
 class AzureEndpointHttpClient:
 
     headers = {