Fix (Experimental): sh: raise AuthorizationError and generate diagnos…

…e messages when ClusterShell fails with 255

crmsh/sh.py

@@ -25,6 +25,7 @@
 import socket
 import subprocess
 import typing
+from io import StringIO
 
 from . import constants
 from .pyshim import cache
@@ -45,15 +46,26 @@ def __init__(self, msg, cmd):
 class AuthorizationError(Error):
     def __init__(self, cmd: str, host: typing.Optional[str], user: str, msg: str):
         super().__init__(
-            'Failed to run command on {optional_user}{host}: {msg}: {cmd}'.format(
+            'Failed to run command {cmd} on {optional_user}{host}: {msg} {diagnose}'.format(
                 optional_user=f'{user}@' if user is not None else '',
-                host=host, msg=msg, cmd=cmd
+                host=host, msg=msg, cmd=cmd,
+                diagnose=self.diagnose(),
             ),
             cmd
         )
         self.host = host
         self.user = user
 
+    @staticmethod
+    def diagnose() -> str:
+        if user_of_host.instance().use_ssh_agent():
+            with StringIO() as buf:
+                if 'SSH_AUTH_SOCK' not in os.environ:
+                    buf.write('Environmental variable SSH_AUTH_SOCK does not exists.')
+                    if 'SUDO_USER' in os.environ:
+                        buf.write(' Please make sure environmental variables are preserved across sudo calls.')
+                return buf.getvalue()
+
 
 class CommandFailure(Error):
     def __init__(self, cmd: str, host: typing.Optional[str], user: typing.Optional[str], msg: str):
@@ -309,7 +321,7 @@ def subprocess_run_without_input(self, host: typing.Optional[str], user: typing.
             local_user, remote_user = self.user_of_host.user_pair_for_ssh(host)
             result = self.local_shell.su_subprocess_run(
                 local_user,
-                'ssh {} {} {}@{} sudo -H -u {} {} /bin/sh'.format(
+                'ssh {} {} -o BatchMode=yes {}@{} sudo -H -u {} {} /bin/sh'.format(
                     '-A' if self.forward_ssh_agent else '',
                     constants.SSH_OPTION,
                     remote_user,
@@ -319,6 +331,7 @@ def subprocess_run_without_input(self, host: typing.Optional[str], user: typing.
                     constants.SSH_OPTION,
                 ),
                 input=cmd.encode('utf-8'),
+                start_new_session=True,
                 **kwargs,
             )
             if self.raise_ssh_error and result.returncode == 255:
@@ -331,7 +344,6 @@ def get_rc_and_error(self, host: typing.Optional[str], user: str, cmd: str):
             host, user, cmd,
             stdout=subprocess.PIPE,
             stderr=subprocess.STDOUT,
-            start_new_session=True,
         )
         if result.returncode == 0:
             return 0, None
@@ -463,4 +475,4 @@ def subprocess_run_without_input(self, host: str, user: typing.Optional[str], cm
 
 
 def cluster_shell():
-    return ClusterShell(LocalShell(), user_of_host.instance())
+    return ClusterShell(LocalShell(), user_of_host.instance(), raise_ssh_error=True)