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core/exec-invoke: suppress placeholder home only in build_environment()

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Currently, get_fixed_user() employs USER_CREDS_SUPPRESS_PLACEHOLDER,
meaning home path is set to NULL if it's empty or root. However,
the path is also used for applying WorkingDirectory=~, and we'd
spuriously use the invoking user's home as fallback even if
User= is changed in that case.

Let's instead delegate such suppression to build_environment(),
so that home is proper initialized for usage at other steps.
shell doesn't actually suffer from such problem, but it's changed
too for consistency.

Alternative to #34789
This commit is contained in:
Mike Yuan 2024-11-18 19:41:07 +01:00
parent d911778877
commit b718b86e1b
No known key found for this signature in database
GPG Key ID: 417471C0A40F58B3
2 changed files with 28 additions and 8 deletions
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16
src/core/exec-invoke.c
View File

@ -855,10 +855,7 @@ static int get_fixed_user(
assert(user_or_uid);
assert(ret_username);
/* Note that we don't set $HOME or $SHELL if they are not particularly enlightening anyway
* (i.e. are "/" or "/bin/nologin"). */
r = get_user_creds(&user_or_uid, ret_uid, ret_gid, ret_home, ret_shell, USER_CREDS_CLEAN|USER_CREDS_SUPPRESS_PLACEHOLDER);
r = get_user_creds(&user_or_uid, ret_uid, ret_gid, ret_home, ret_shell, USER_CREDS_CLEAN);
if (r < 0)
return r;
@ -1883,7 +1880,10 @@ static int build_environment(
}
}
if (home && set_user_login_env) {
/* Note that we don't set $HOME or $SHELL if they are not particularly enlightening anyway
* (i.e. are "/" or "/bin/nologin"). */
if (home && set_user_login_env && !empty_or_root(home)) {
x = strjoin("HOME=", home);
if (!x)
return -ENOMEM;
@ -1892,7 +1892,7 @@ static int build_environment(
our_env[n_env++] = x;
}
if (shell && set_user_login_env) {
if (shell && set_user_login_env && !shell_is_placeholder(shell)) {
x = strjoin("SHELL=", shell);
if (!x)
return -ENOMEM;
@ -3775,7 +3775,7 @@ static int acquire_home(const ExecContext *c, const char **home, char **ret_buf)
if (!c->working_directory_home)
return 0;
if (c->dynamic_user)
if (c->dynamic_user || (c->user && is_this_me(c->user) <= 0))
return -EADDRNOTAVAIL;
r = get_home_dir(ret_buf);
@ -4533,7 +4533,7 @@ int exec_invoke(
r = acquire_home(context, &home, &home_buffer);
if (r < 0) {
*exit_status = EXIT_CHDIR;
return log_exec_error_errno(context, params, r, "Failed to determine $HOME for user: %m");
return log_exec_error_errno(context, params, r, "Failed to determine $HOME for the invoking user: %m");
}
/* If a socket is connected to STDIN/STDOUT/STDERR, we must drop O_NONBLOCK */

20
test/units/TEST-07-PID1.working-directory.sh Executable file
View File

@ -0,0 +1,20 @@
#!/usr/bin/env bash
# SPDX-License-Identifier: LGPL-2.1-or-later
set -eux
set -o pipefail
# shellcheck source=test/units/util.sh
. "$(dirname "$0")"/util.sh
(! systemd-run --wait -p DynamicUser=yes \
-p EnvironmentFile=-/usr/lib/systemd/systemd-asan-env \
-p WorkingDirectory='~' true)
assert_eq "$(systemd-run --pipe --uid=root -p WorkingDirectory='~' pwd)" "/root"
assert_eq "$(systemd-run --pipe --uid=nobody -p WorkingDirectory='~' pwd)" "/"
assert_eq "$(systemd-run --pipe --uid=testuser -p WorkingDirectory='~' pwd)" "/home/testuser"
(! systemd-run --wait -p DynamicUser=yes -p User=testuser \
-p EnvironmentFile=-/usr/lib/systemd/systemd-asan-env \
-p WorkingDirectory='~' true)