lib.ec.SSHClientInternal|SSHClientCmd: Own .py

Move the code of SSHClientInternal and SSCClientCmd into lib.ec.ssh,
as "Paramiko" and "Exec", respectively. This makes the class layout
a little more modular, and along the way fixes a bug where
SSHClientInternal could be instantiated but was unusable (if the
Paramiko is not installed).

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ec/SSHClient.py

@@ -2,9 +2,9 @@
 
 from typing import Any
 
-import os, abc, shlex, sys
+import os, abc, sys
 
-from ..util import run_cmd, pretty_cmd
+from ..util import pretty_cmd
 from ..log import *
 from ..ExecContext import ExecContext, Result
 from urllib.parse import urlparse
@@ -19,7 +19,7 @@ class SSHClient(ExecContext):
             log(ERR, f'Failed to parse SSH URI "{uri}"')
             raise
         self.__hostname = parsed.hostname
-        self.__password: parsed.password
+        self.__password = parsed.password
         self.__username = parsed.username
 
     @abc.abstractmethod
@@ -93,89 +93,18 @@ class SSHClient(ExecContext):
     def username(self) -> str:
         return self.__username
 
-class SSHClientInternal(SSHClient): # export
-
-    def __init__(self, *args, **kwargs) -> None:
-        super().__init__(*args, **kwargs)
-        self.__timeout: float|None = None # Untested
-        self.___ssh: Any|None = None
-
-    def __ssh_connect(self):
-        import paramiko # type: ignore # error: Library stubs not installed for "paramiko"
-        ret = paramiko.SSHClient()
-        ret.set_missing_host_key_policy(paramiko.AutoAddPolicy())
-        try:
-            ret.connect(
-                hostname=self.hostname,
-                username=self.username,
-                allow_agent=True
-            )
-        except Exception as e:
-            log(ERR, f'Failed to connect to {self.hostname} with key file {path_to_key} ({str(e)})')
-            raise
-        s = ret.get_transport().open_session()
-        # set up the agent request handler to handle agent requests from the server
-        paramiko.agent.AgentRequestHandler(s)
-        return ret
-
-    @property
-    def __ssh(self):
-        if self.___ssh is None:
-            self.___ssh = self.__ssh_connect()
-        return self.___ssh
-
-    @property
-    def __scp(self):
-        return SCPClient(self.__ssh.get_transport())
-
-    async def _run_ssh(self, cmd: list[str], cmd_input: str|None) -> Result:
-        try:
-            stdin, stdout, stderr = self.__ssh.exec_command(shlex.join(cmd), timeout=self.__timeout)
-        except Exception as e:
-            log(ERR, f'Command failed for {self.uri}: "{shlex.join(cmd)}"')
-            raise
-        if cmd_input is not None:
-            stdin.write(cmd_input)
-        exit_status = stdout.channel.recv_exit_status()
-        return Result(stdout.read(), stderr.read(), exit_status)
-
-class SSHClientCmd(SSHClient): # export
-
-    def __init__(self, *args, **kwargs) -> None:
-        self.__askpass: str|None = None
-        self.__askpass_orig: dict[str, str|None] = dict()
-        super().__init__(*args, **kwargs)
-
-    def __del__(self):
-        for key, val in self.__askpass_orig.items():
-            if val is None:
-                del os.environ[key]
-            else:
-                os.environ[key] = val
-        if self.__askpass is not None:
-            os.remove(self.__askpass)
-
-    def __init_askpass(self):
-        if self.__askpass is None and self.password is not None:
-            import sys, tempfile
-            prefix = os.path.basename(sys.argv[0]) + '-'
-            f = tempfile.NamedTemporaryFile(mode='w+t', prefix=prefix, delete=False)
-            os.chmod(f.name, 0o0700)
-            self.__askpass = f.name
-            f.write(f'#!/bin/bash\n\necho -n "{self.password}\n"')
-            f.close()
-            for key, val in {'SSH_ASKPASS': self.__askpass, 'SSH_ASKPASS_REQUIRE': 'force'}.items():
-                self.__askpass_orig[key] = os.getenv(key)
-                os.environ[key] = val
-
-    async def _run_ssh(self, cmd: list[str], cmd_input: str|None) -> Result:
-        self.__init_askpass()
-        return await run_cmd(['ssh', self.hostname, shlex.join(cmd)],
-                             output_encoding='bytes', cmd_input=cmd_input)
-
 def ssh_client(*args, **kwargs) -> SSHClient: # export
-    try:
-        return SSHClientInternal(*args, **kwargs)
-    except:
-        pass
-    return SSHClientCmd(*args, **kwargs)
+    from importlib import import_module
+    errors: list[str] = []
+    for name in ['Paramiko', 'Exec']:
+        try:
+            return getattr(import_module(f'jw.pkg.lib.ec.ssh.{name}'), name)(*args, **kwargs)
+        except Exception as e:
+            msg = f'Can\'t instantiate SSH client class {name} ({str(e)})'
+            errors.append(msg)
+            log(DEBUG, f'{msg}, trying next')
+    msg = f'No working SSH clients for {" ".join(args)}'
+    log(ERR, f'----- {msg}')
+    for error in errors:
+        log(ERR, error)
+    raise Exception(msg)