utils/ssh: Allow passing known_hosts path via strict_host_check value

Allow passing a known_hosts file path to strict_host_check.

devlib/utils/ssh.py

@@ -17,6 +17,7 @@
 import os
 import stat
 import logging
+from pathlib import Path
 import subprocess
 import re
 import threading
@@ -174,6 +175,18 @@ def _read_paramiko_streams_internal(stdout, stderr, select_timeout, callback, in
         return (callback_state, exit_code)
 
 
+def _resolve_known_hosts(strict_host_check):
+    if strict_host_check:
+        if isinstance(strict_host_check, (str, os.PathLike)):
+            path = Path(strict_host_check)
+        else:
+            path = Path('~/.ssh/known_hosts').expandvars()
+    else:
+        path = Path('/dev/null')
+
+    return str(path.resolve())
+
+
 def telnet_get_shell(host,
                   username,
                   password=None,
@@ -407,7 +420,9 @@ class SshConnection(SshConnectionBase):
         with _handle_paramiko_exceptions():
             client = SSHClient()
             if self.strict_host_check:
-                client.load_system_host_keys()
+                client.load_system_host_keys(_resolve_known_hosts(
+                    self.strict_host_check
+                ))
             client.set_missing_host_key_policy(policy)
             client.connect(
                 hostname=self.host,
@@ -818,16 +833,12 @@ class TelnetConnection(SshConnectionBase):
         return '{}@{}:{}'.format(self.username, self.host, path)
 
     def _get_default_options(self):
-        if self.strict_host_check:
-            options = {
-                'StrictHostKeyChecking': 'yes',
-            }
-        else:
-            options = {
-                'StrictHostKeyChecking': 'no',
-                'UserKnownHostsFile': '/dev/null',
-            }
-        return options
+        check = self.strict_host_check
+        known_hosts = _resolve_known_hosts(check)
+        return {
+            'StrictHostKeyChecking': 'yes' if check else 'no',
+            'UserKnownHostsFile': str(known_hosts),
+        }
 
     def push(self, sources, dest, timeout=30):
         # Quote the destination as SCP would apply globbing too

doc/connection.rst

@@ -177,7 +177,11 @@ Connection Types
     :param platform: Specify the platform to be used. The generic :class:`~devlib.platform.Platform`
                      class is used by default.
     :param sudo_cmd: Specify the format of the command used to grant sudo access.
-    :param strict_host_check: Specify the ssh connection parameter ``StrictHostKeyChecking``,
+    :param strict_host_check: Specify the ssh connection parameter
+			     ``StrictHostKeyChecking``. If a path is passed
+			     rather than a boolean, it will be taken for a
+			     ``known_hosts`` file.  Otherwise, the default
+			     ``$HOME/.ssh/known_hosts`` will be used.
     :param use_scp: Use SCP for file transfers, defaults to SFTP.
     :param poll_transfers: Specify whether file transfers should be polled. Polling
                            monitors the progress of file transfers and periodically