lib.ec.ssh: Don't quote shell operators

Naively join()ing a command list to be executed remotely via SSH also
quotes shell operators which doesn't work, of course. Work around
that. The workaround will not always work but covers lots of cases.

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

src/python/jw/pkg/lib/ec/ssh/AsyncSSH.py

@@ -6,6 +6,8 @@ from ...log import *
 from ...ExecContext import Result
 from ..SSHClient import SSHClient as Base
 
+from .util import join_cmd
+
 _USE_DEFAULT_KNOWN_HOSTS = object()
 
 class AsyncSSH(Base):
@@ -52,7 +54,7 @@ class AsyncSSH(Base):
         if not cmd:
             raise ValueError("cmd must not be empty")
 
-        inner = f"exec {shlex.join(cmd)}"
+        inner = f"exec {join_cmd(cmd)}"
         if wd is not None:
             inner = f"cd {shlex.quote(wd)} && {inner}"
 

src/python/jw/pkg/lib/ec/ssh/Exec.py

@@ -2,10 +2,9 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING
 
-import shlex
-
 from ...util import run_cmd
 from ..SSHClient import SSHClient as Base
+from .util import join_cmd
 
 if TYPE_CHECKING:
     from ...ExecContext import Result
@@ -41,5 +40,5 @@ class Exec(Base):
 
     async def _run_ssh(self, cmd: list[str], cmd_input: str|None, *args, **kwargs) -> Result:
         self.__init_askpass()
-        return await run_cmd(['ssh', self.hostname, shlex.join(cmd)], cmd_input=cmd_input)
+        return await run_cmd(['ssh', self.hostname, join_cmd(cmd)], cmd_input=cmd_input)
 

src/python/jw/pkg/lib/ec/ssh/Paramiko.py

@@ -3,12 +3,13 @@ from __future__ import annotations
 from typing import TYPE_CHECKING
 
 import paramiko # type: ignore # error: Library stubs not installed for "paramiko"
-import shlex
 
 from ...log import *
 from ...ExecContext import Result
 from ..SSHClient import SSHClient as Base
 
+from .util import join_cmd
+
 class Paramiko(Base):
 
     def __init__(self, *args, **kwargs) -> None:
@@ -45,9 +46,9 @@ class Paramiko(Base):
 
     async def _run_ssh(self, cmd: list[str], cmd_input: str|None, *args, **kwargs) -> Result:
         try:
-            stdin, stdout, stderr = self.__ssh.exec_command(shlex.join(cmd), timeout=self.__timeout)
+            stdin, stdout, stderr = self.__ssh.exec_command(join_cmd(cmd), timeout=self.__timeout)
         except Exception as e:
-            log(ERR, f'Command failed for {self.uri}: "{shlex.join(cmd)}"')
+            log(ERR, f'Command failed for {self.uri}: "{join_cmd(cmd)}"')
             raise
         if cmd_input is not None:
             stdin.write(cmd_input)

src/python/jw/pkg/lib/ec/ssh/util.py

@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+
+from typing import Iterable
+
+import shlex
+
+DEFAULT_SHELL_OPERATORS = {
+    # redirections
+    ">", ">>", "<", "<<", "<<-", "<&", ">&", "<>", ">|",
+    "1>", "1>>", "2>", "2>>",
+
+    # pipelines / control
+    "|", "||", "&", "&&", ";",
+
+    # grouping
+    "(", ")",
+}
+
+def join_cmd(
+    cmd: Iterable[str],
+    operators: set[str] = DEFAULT_SHELL_OPERATORS,
+) -> str:
+    """
+    Join a token list into a POSIX-shell command string.
+
+    Tokens in `operators` are emitted verbatim.
+    Everything else is shell-quoted with shlex.quote().
+
+    Example:
+        ["echo", "hello world", ">", "/tmp/out file"]
+        -> "echo 'hello world' > '/tmp/out file'"
+    """
+    ret: list[str] = []
+    for token in cmd:
+        if not isinstance(token, str):
+            token = str(token)
+        if token in operators:
+            ret.append(token)
+        else:
+            ret.append(shlex.quote(token))
+    return ' '.join(ret)