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/ssh/Exec.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import shlex
+
+from ...util import run_cmd
+from ..SSHClient import SSHClient as Base
+
+if TYPE_CHECKING:
+    from ...ExecContext import Result
+
+class Exec(Base): # 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)], cmd_input=cmd_input)
+