chroot: combine user.py and root.py into run.py (MR 2252)

These are small related utility functions, combine them together.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/chroot/run.py

@@ -0,0 +1,127 @@
+# Copyright 2023 Oliver Smith
+# SPDX-License-Identifier: GPL-3.0-or-later
+import os
+from pathlib import Path, PurePath
+import shutil
+from typing import Sequence
+
+import pmb.config
+import pmb.chroot
+import pmb.chroot.binfmt
+import pmb.helpers.run
+import pmb.helpers.run_core
+from pmb.core import Chroot
+from pmb.core.types import Env, PathString, PmbArgs
+
+
+def executables_absolute_path():
+    """
+    Get the absolute paths to the sh and chroot executables.
+    """
+    ret = {}
+    for binary in ["sh", "chroot"]:
+        path = shutil.which(binary, path=pmb.config.chroot_host_path)
+        if not path:
+            raise RuntimeError(f"Could not find the '{binary}'"
+                               " executable. Make sure that it is in"
+                               " your current user's PATH.")
+        ret[binary] = path
+    return ret
+
+
+def root(args: PmbArgs, cmd: Sequence[PathString], chroot: Chroot=Chroot.native(), working_dir: PurePath=PurePath("/"), output="log",
+         output_return=False, check=None, env={},
+         disable_timeout=False, add_proxy_env_vars=True):
+    """
+    Run a command inside a chroot as root.
+
+    :param env: dict of environment variables to be passed to the command, e.g.
+                {"JOBS": "5"}
+    :param working_dir: chroot-relative working directory
+    :param add_proxy_env_vars: if True, preserve HTTP_PROXY etc. vars from host
+                               environment. pmb.chroot.user sets this to False
+                               when calling pmb.chroot.root, because it already
+                               makes the variables part of the cmd argument.
+
+    See pmb.helpers.run_core.core() for a detailed description of all other
+    arguments and the return value.
+    """
+
+    # Convert any Path objects to their string representation
+    cmd_str = [os.fspath(x) for x in cmd]
+
+    # Readable log message (without all the escaping)
+    msg = f"({chroot}) % "
+    for key, value in env.items():
+        msg += f"{key}={value} "
+    if working_dir != PurePath("/"):
+        msg += f"cd {working_dir}; "
+    msg += " ".join(cmd_str)
+
+    # Merge env with defaults into env_all
+    env_all: Env = {"CHARSET": "UTF-8",
+               "HISTFILE": "~/.ash_history",
+               "HOME": "/root",
+               "LANG": "UTF-8",
+               "PATH": pmb.config.chroot_path,
+               "PYTHONUNBUFFERED": "1",
+               "SHELL": "/bin/ash",
+               "TERM": "xterm"}
+    for key, value in env.items():
+        env_all[key] = value
+    if add_proxy_env_vars:
+        pmb.helpers.run_core.add_proxy_env_vars(env_all)
+
+    # Build the command in steps and run it, e.g.:
+    # cmd: ["echo", "test"]
+    # cmd_chroot: ["/sbin/chroot", "/..._native", "/bin/sh", "-c", "echo test"]
+    # cmd_sudo: ["sudo", "env", "-i", "sh", "-c", "PATH=... /sbin/chroot ..."]
+    executables = executables_absolute_path()
+    cmd_chroot = [executables["chroot"], chroot.path, "/bin/sh", "-c",
+                  pmb.helpers.run_core.flat_cmd(cmd_str, Path(working_dir))]
+    cmd_sudo = pmb.config.sudo([
+        "env", "-i", executables["sh"], "-c",
+        pmb.helpers.run_core.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)
+
+
+def user(args: PmbArgs, cmd, chroot: Chroot=Chroot.native(), working_dir: Path = Path("/"), output="log",
+         output_return=False, check=None, env={}):
+    """
+    Run a command inside a chroot as "user". We always use the BusyBox
+    implementation of 'su', because other implementations may override the PATH
+    environment variable (#1071).
+
+    :param env: dict of environment variables to be passed to the command, e.g.
+                {"JOBS": "5"}
+
+    See pmb.helpers.run_core.core() for a detailed description of all other
+    arguments and the return value.
+    """
+    env = env.copy()
+    pmb.helpers.run_core.add_proxy_env_vars(env)
+
+    if "HOME" not in env:
+        env["HOME"] = "/home/pmos"
+
+    flat_cmd = pmb.helpers.run_core.flat_cmd(cmd, env=env)
+    cmd = ["busybox", "su", "pmos", "-c", flat_cmd]
+    return pmb.chroot.root(args, cmd, chroot, working_dir, output,
+                           output_return, check, {},
+                           add_proxy_env_vars=False)
+
+
+def exists(args: PmbArgs, username, chroot: Chroot=Chroot.native()):
+    """
+    Checks if username exists in the system
+
+    :param username: User name
+    :returns: bool
+    """
+    output = pmb.chroot.root(args, ["getent", "passwd", username],
+                             chroot, output_return=True, check=False)
+    return len(output) > 0
+