ssh: ensure keyfile has the right permissions

The key file must only be readable by the owner. If the specified key
file has different access permissions, create a temporary copy with the
right permissions and use that.

wlauto/utils/ssh.py

@@ -14,10 +14,14 @@
 #
 
 
+import os
+import stat
 import logging
 import subprocess
 import re
 import threading
+import tempfile
+import shutil
 
 import pxssh
 from pexpect import EOF, TIMEOUT, spawn
@@ -81,6 +85,25 @@ class TelnetConnection(pxssh.pxssh):
         return True
 
 
+def check_keyfile(keyfile):
+    """
+    keyfile must have the right access premissions in order to be useable. If the specified
+    file doesn't, create a temporary copy and set the right permissions for that.
+
+    Returns either the ``keyfile`` (if the permissions on it are correct) or the path to a
+    temporary copy with the right permissions.
+    """
+    desired_mask = stat.S_IWUSR | stat.S_IRUSR
+    actual_mask = os.stat(keyfile).st_mode & 0xFF
+    if actual_mask != desired_mask:
+        tmp_file = os.path.join(tempfile.gettempdir(), os.path.basename(keyfile))
+        shutil.copy(keyfile, tmp_file)
+        os.chmod(tmp_file, desired_mask)
+        return tmp_file
+    else:  # permissions on keyfile are OK
+        return keyfile
+
+
 class SshShell(object):
 
     default_password_prompt = '[sudo] password'
@@ -97,10 +120,10 @@ class SshShell(object):
         self.host = host
         self.username = username
         self.password = password
-        self.keyfile = keyfile
+        self.keyfile = check_keyfile(keyfile)
         self.port = port
         timeout = self.timeout if timeout is None else timeout
-        self.conn = ssh_get_shell(host, username, password, keyfile, port, timeout, telnet)
+        self.conn = ssh_get_shell(host, username, password, self.keyfile, port, timeout, telnet)
 
     def push_file(self, source, dest, timeout=30):
         dest = '{}@{}:{}'.format(self.username, self.host, dest)