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run: disable --expand-environment by default for --scope

Browse Source 
The intention was to have this option enabled by default everywhere,
but unfortunately at least one case was found where it breaks
compatibility of a program using systemd-run --scopes and expecting
variables not to be expanded:

https://sources.debian.org/src/pbuilder/0.231/pbuilder-checkparams/#L400

Example run:

systemd-run --quiet --scope --description=pbuilder_build_xfce4-notes-plugin_1.10.0-1.dsc '--slice=system-pbuilder-build-xfce4\x2dnotes\x2dplugin_1.10.0\x2d1-449932.slice' chroot /var/cache/pbuilder/build/449932 dpkg-query -W '--showformat=${Version}' apt

Restore backward compatibility and make the option disabled by default
when --scope is used, and enabled by default for other types.

In case --expand-environment is not specified and a '$' character is
detected, print a warning to nudge users toward specifying the
parameter as needed. In the future we can then flip the default.

Follow-up for 2ed7a221fa
This commit is contained in:
Luca Boccassi 2023-07-19 22:56:02 +01:00
parent e51846adc0
commit 8167c56bfa
2 changed files with 32 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
man/systemd-run.xml
View File

@ -177,15 +177,19 @@
<varlistentry>
<term><option>--expand-environment=<replaceable>BOOL</replaceable></option></term>
<listitem><para>Expand environment variables in command arguments. If enabled (the default),
environment variables specified as <literal>${<replaceable>VARIABLE</replaceable>}</literal> will be
expanded in the same way as in commands specified via <varname>ExecStart=</varname> in units. With
<listitem><para>Expand environment variables in command arguments. If enabled, environment variables
specified as <literal>${<replaceable>VARIABLE</replaceable>}</literal> will be expanded in the same
way as in commands specified via <varname>ExecStart=</varname> in units. With
<varname>--scope</varname>, this expansion is performed by <command>systemd-run</command> itself, and
in other cases by the service manager that spawns the command. Note that this is similar to, but not
the same as variable expansion in
<citerefentry project='man-pages'><refentrytitle>bash</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and other shells.</para>
<para>The default is to enable this option in all cases, except for <varname>--scope</varname> where
it is disabled by default, for backward compatibility reasons. Note that this will be changed in a
future release, where it will be switched to enabled by default as well.</para>
<para>See
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for a description of variable expansion. Disabling variable expansion is useful if the specified

32
src/run/run.c
View File

@ -45,7 +45,7 @@ static const char *arg_unit = NULL;
static const char *arg_description = NULL;
static const char *arg_slice = NULL;
static bool arg_slice_inherit = false;
static bool arg_expand_environment = true;
static int arg_expand_environment = -1;
static bool arg_send_sighup = false;
static BusTransport arg_transport = BUS_TRANSPORT_LOCAL;
static const char *arg_host = NULL;
@ -291,11 +291,17 @@ static int parse_argv(int argc, char *argv[]) {
arg_slice_inherit = true;
break;
case ARG_EXPAND_ENVIRONMENT:
r = parse_boolean_argument("--expand-environment=", optarg, &arg_expand_environment);
case ARG_EXPAND_ENVIRONMENT: {
bool b;
r = parse_boolean_argument("--expand-environment=", optarg, &b);
if (r < 0)
return r;
arg_expand_environment = b;
break;
}
case ARG_SEND_SIGHUP:
arg_send_sighup = true;
@ -732,7 +738,7 @@ static int transient_service_set_properties(sd_bus_message *m, const char *pty_p
/* We disable environment expansion on the server side via ExecStartEx=:.
* ExecStartEx was added relatively recently (v243), and some bugs were fixed only later.
* So use that feature only if required. It will fail with older systemds. */
bool use_ex_prop = !arg_expand_environment;
bool use_ex_prop = arg_expand_environment == 0;
assert(m);
@ -896,7 +902,7 @@ static int transient_service_set_properties(sd_bus_message *m, const char *pty_p
if (use_ex_prop)
r = sd_bus_message_append_strv(
m,
STRV_MAKE(arg_expand_environment ? NULL : "no-env-expand"));
STRV_MAKE(arg_expand_environment > 0 ? NULL : "no-env-expand"));
else
r = sd_bus_message_append(m, "b", false);
if (r < 0)
@ -1197,7 +1203,7 @@ static int bus_call_with_hint(
if (r < 0) {
log_error_errno(r, "Failed to start transient %s unit: %s", name, bus_error_message(&error, r));
if (!arg_expand_environment &&
if (arg_expand_environment == 0 &&
sd_bus_error_has_names(&error,
SD_BUS_ERROR_UNKNOWN_PROPERTY,
SD_BUS_ERROR_PROPERTY_READ_ONLY))
@ -1614,7 +1620,7 @@ static int start_transient_scope(sd_bus *bus) {
if (!arg_quiet)
log_info("Running scope as unit: %s", scope);
if (arg_expand_environment) {
if (arg_expand_environment > 0) {
_cleanup_strv_free_ char **expanded_cmdline = NULL, **unset_variables = NULL, **bad_variables = NULL;
r = replace_env_argv(arg_cmdline, env, &expanded_cmdline, &unset_variables, &bad_variables);
@ -1868,6 +1874,18 @@ static int run(int argc, char* argv[]) {
arg_description = description;
}
/* For backward compatibility reasons env var expansion is disabled by default for scopes, and
* enabled by default for everything else. Try to detect it and print a warning, so that we can
* change it in the future and harmonize it. */
if (arg_expand_environment < 0) {
arg_expand_environment = !arg_scope;
if (!arg_quiet && arg_scope && strchr(arg_description, '$'))
log_warning("Scope command line contains environment variable, which is not expanded"
" by default for now, but will be expanded by default in the future."
" Use --expand-environment=yes/no to explicitly control it as needed.");
}
/* If --wait is used connect via the bus, unconditionally, as ref/unref is not supported via the limited direct
* connection */
if (arg_wait || arg_stdio != ARG_STDIO_NONE || (arg_runtime_scope == RUNTIME_SCOPE_USER && arg_transport != BUS_TRANSPORT_LOCAL))