Don't use 'sudo' when running as root

This cancels the need to install and configure `sudo` or `doas` on
single-user installations (e.g.: a VM dedicated to running pmbootstrap).

Fixes: https://gitlab.com/postmarketOS/pmbootstrap/-/issues/2224
Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230529203922.22161-1-hugo@whynothugo.nl%3E

pmb/chroot/root.py

@@ -78,8 +78,10 @@ def root(args, cmd, suffix="native", working_dir="/", output="log",
     executables = executables_absolute_path()
     cmd_chroot = [executables["chroot"], chroot, "/bin/sh", "-c",
                   pmb.helpers.run.flat_cmd(cmd, working_dir)]
-    cmd_sudo = [pmb.config.sudo, "env", "-i", executables["sh"], "-c",
-                pmb.helpers.run.flat_cmd(cmd_chroot, env=env_all)]
+    cmd_sudo = pmb.config.sudo([
+        "env", "-i", executables["sh"], "-c",
+        pmb.helpers.run.flat_cmd(cmd_chroot, env=env_all)]
+    )
     return pmb.helpers.run_core.core(args, msg, cmd_sudo, None, output,
                                      output_return, check, True,
                                      disable_timeout)

pmb/config/__init__.py

@@ -58,7 +58,16 @@ required_programs = [
     "ps",
     "tar",
 ]
-sudo = which_sudo()
+
+
+def sudo(cmd: list[str]) -> list[str]:
+    """Adapt a command to run as root."""
+    sudo = which_sudo()
+    if sudo:
+        return [sudo, *cmd]
+    else:
+        return cmd
+
 
 # Keys saved in the config file (mostly what we ask in 'pmbootstrap init')
 config_keys = [

pmb/config/sudo.py

@@ -2,13 +2,20 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 import os
 import shutil
+from functools import lru_cache
 
 
-def which_sudo():
-    """
+@lru_cache()
+def which_sudo() -> str | None:
+    """Returns a command required to run commands as root, if any.
+
     Find whether sudo or doas is installed for commands that require root.
     Allows user to override preferred sudo with PMB_SUDO env variable.
     """
+
+    if os.getuid() == 0:
+        return None
+
     supported_sudos = ['doas', 'sudo']
 
     user_set_sudo = os.getenv("PMB_SUDO")

pmb/helpers/run.py

@@ -72,7 +72,7 @@ def root(args, cmd, working_dir=None, output="log", output_return=False,
     """
     if env:
         cmd = ["sh", "-c", flat_cmd(cmd, env=env)]
-    cmd = [pmb.config.sudo] + cmd
+    cmd = pmb.config.sudo(cmd)
 
     return user(args, cmd, working_dir, output, output_return, check, env,
                 True)

test/test_run_core.py

@@ -83,7 +83,7 @@ def test_foreground_pipe(args):
     assert ret == (-9, "first\n")
 
     # Kill with output timeout as root
-    cmd = [pmb.config.sudo, "sh", "-c", "printf first; sleep 2; printf second"]
+    cmd = pmb.config.sudo(["sh", "-c", "printf first; sleep 2; printf second"])
     args.timeout = 0.3
     ret = func(args, cmd, output_return=True, output_timeout=True,
                sudo=True)
@@ -99,9 +99,11 @@ def test_foreground_pipe(args):
     # Check if all child processes are killed after timeout.
     # The first command uses ps to get its process group id (pgid) and echo it
     # to stdout. All of the test commands will be running under that pgid.
-    cmd = [pmb.config.sudo, "sh", "-c",
-           "pgid=$(ps -o pgid= | grep ^${1:-$$});echo $pgid | tr -d '\n';" +
-           "sleep 10 | sleep 20 | sleep 30"]
+    cmd = pmb.config.sudo([
+        "sh", "-c",
+        "pgid=$(ps -o pgid= | grep ^${1:-$$});echo $pgid | tr -d '\n';"
+        "sleep 10 | sleep 20 | sleep 30"
+    ])
     args.timeout = 0.3
     ret = func(args, cmd, output_return=True, output_timeout=True,
                sudo=True)