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sysusers: allow admin/runtime overrides to command-line config

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When used in a package installation script, we want to invoke systemd-sysusers
before that package is installed (so it can contain files owned by the newly
created user), so the configuration to use is specified on the command
line. This should be a copy of the configuration that will be installed as
/usr/lib/sysusers.d/package.conf. We still want to obey any overrides in
/etc/sysusers.d or /run/sysusers.d in the usual fashion. Otherwise, we'd get a
different result when systemd-sysusers is run with a copy of the new config on
the command line and when systemd-sysusers is run at boot after package
instalation. In the second case any files in /etc or /run have higher priority,
so the same should happen when the configuration is given on the command line.
More generally, we want the behaviour in this special case to be as close to
the case where the file is finally on disk as possible, so we have to read all
configuration files, since they all might contain overrides and additional
configuration that matters. Even files that have lower priority might specify
additional groups for the user we are creating. Thus, we need to read all
configuration, but insert our new configuration somewhere with the right
priority.

If --target=/path/to/file.conf is given on the command line, we gather the list
of files, and pretend that the command-line config is read from
/path/to/file.conf (doesn't matter if the file on disk actually exists or
not). All package scripts should use this option to obtain consistent and
idempotent behaviour.

The corner case when --target= is specified and there are no positional
arguments is disallowed.

v1:
- version with --config-name=
v2:
- disallow --config-name= and no positional args
v3:
- remove --config-name=
v4:
- add --target= and rework the code completely
v5:
- fix argcounting bug and add example in man page
v6:
- rename --target to --replace
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2018-01-31 15:37:02 +01:00
parent 6e888894fc
commit d16a1c1bb6
4 changed files with 200 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

55
man/systemd-sysusers.xml
View File

@ -69,15 +69,18 @@
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
<para>If invoked with no arguments, it applies all directives from
all files found. If one or more filenames are passed on the
command line, only the directives in these files are applied. If
only the basename of a file is specified, all directories as
specified in
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
are searched for a matching file. If the string
<literal>-</literal> is specified instead of a filename, entries from the
standard input of the process are read.</para>
<para>If invoked with no arguments, it applies all directives from all files
found in the directories specified by
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
When invoked with positional arguments, if option
<option>--replace=<replaceable>PATH</replaceable></option> is specified, arguments
specified on the command line are used instead of the configuration file
<replaceable>PATH</replaceable>. Otherwise, just the configuration specified by
the command line arguments is executed. The string <literal>-</literal> may be
specified instead of a filename to instruct <command>systemd-sysusers</command>
to read the configuration from standard input. If only the basename of a file is
specified, all configuration directories are searched for a matching file and
the file found that has the highest priority is executed.</para>
</refsect1>
<refsect1>
@ -94,6 +97,40 @@
paths. </para></listitem>
</varlistentry>
<varlistentry>
<term><option>--replace=<replaceable>PATH</replaceable></option></term>
<listitem><para>When this option is given, one ore more positional arguments
must be specified. All configuration files found in the directories listed in
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
will be read, and the configuration given on the command line will be
handled instead of and with the same priority as the configuration file
<replaceable>PATH</replaceable>.</para>
<para>This option is intended to be used when package installation scripts
are running and files belonging to that package are not yet available on
disk, so their contents must be given on the command line, but the admin
configuration might already exist and should be given higher priority.
</para>
<example>
<title>RPM installation script for radvd</title>
<programlisting>echo 'u radvd - "radvd daemon"' | \
systemd-sysusers --replace=/usr/lib/sysusers.d/radvd.conf -</programlisting>
<para>This will create the radvd user as if
<filename>/usr/lib/sysusers.d/radvd.conf</filename> was already on disk.
An admin might override the configuration specified on the command line by
placing <filename>/etc/sysusers.d/radvd.conf</filename> or even
<filename>/etc/sysusers.d/00-overrides.conf</filename>.</para>
<para>Note that this is the expanded from, and when used in a package, this
would be written using a macro with "radvd" and a file containing the
configuration line as arguments.</para>
</example>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--inline</option></term>
<listitem><para>Treat each positional argument as a separate configuration

64
src/basic/conf-files.c
View File

@ -154,6 +154,70 @@ static int conf_files_list_strv_internal(char ***strv, const char *suffix, const
return 0;
}
int conf_files_insert(char ***strv, const char *root, const char *dirs, const char *path) {
/* Insert a path into strv, at the place honouring the usual sorting rules:
* - we first compare by the basename
* - and then we compare by dirname, allowing just one file with the given
* basename.
* This means that we will
* - add a new entry if basename(path) was not on the list,
* - do nothing if an entry with higher priority was already present,
* - do nothing if our new entry matches the existing entry,
* - replace the existing entry if our new entry has higher priority.
*/
char *t;
unsigned i;
int r;
for (i = 0; i < strv_length(*strv); i++) {
int c;
c = base_cmp(*strv + i, &path);
if (c == 0) {
const char *dir;
/* Oh, we found our spot and it already contains something. */
NULSTR_FOREACH(dir, dirs) {
char *p1, *p2;
p1 = path_startswith((*strv)[i], root);
if (p1)
/* Skip "/" in dir, because p1 is without "/" too */
p1 = path_startswith(p1, dir + 1);
if (p1)
/* Existing entry with higher priority
* or same priority, no need to do anything. */
return 0;
p2 = path_startswith(path, dir);
if (p2) {
/* Our new entry has higher priority */
t = path_join(root, path, NULL);
if (!t)
return log_oom();
return free_and_replace((*strv)[i], t);
}
}
} else if (c > 0)
/* Following files have lower priority, let's go insert our
* new entry. */
break;
/* … we are not there yet, let's continue */
}
t = path_join(root, path, NULL);
if (!t)
return log_oom();
r = strv_insert(strv, i, t);
if (r < 0)
free(t);
return r;
}
int conf_files_list_strv(char ***strv, const char *suffix, const char *root, unsigned flags, const char* const* dirs) {
_cleanup_strv_free_ char **copy = NULL;

1
src/basic/conf-files.h
View File

@ -28,3 +28,4 @@ enum {
int conf_files_list(char ***ret, const char *suffix, const char *root, unsigned flags, const char *dir, ...);
int conf_files_list_strv(char ***ret, const char *suffix, const char *root, unsigned flags, const char* const* dirs);
int conf_files_list_nulstr(char ***ret, const char *suffix, const char *root, unsigned flags, const char *dirs);
int conf_files_insert(char ***strv, const char *root, const char *dirs, const char *path);

118
src/sysusers/sysusers.c
View File

@ -75,6 +75,7 @@ typedef struct Item {
} Item;
static char *arg_root = NULL;
static const char *arg_replace = NULL;
static bool arg_inline = false;
static const char conf_file_dirs[] = CONF_PATHS_NULSTR("sysusers.d");
@ -1746,6 +1747,7 @@ static void help(void) {
" -h --help Show this help\n"
" --version Show package version\n"
" --root=PATH Operate on an alternate filesystem root\n"
" --replace=PATH Treat arguments as replacement for PATH\n"
" --inline Treat arguments as configuration lines\n"
, program_invocation_short_name);
}
@ -1755,6 +1757,7 @@ static int parse_argv(int argc, char *argv[]) {
enum {
ARG_VERSION = 0x100,
ARG_ROOT,
ARG_REPLACE,
ARG_INLINE,
};
@ -1762,6 +1765,7 @@ static int parse_argv(int argc, char *argv[]) {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, ARG_VERSION },
{ "root", required_argument, NULL, ARG_ROOT },
{ "replace", required_argument, NULL, ARG_REPLACE },
{ "inline", no_argument, NULL, ARG_INLINE },
{}
};
@ -1788,6 +1792,16 @@ static int parse_argv(int argc, char *argv[]) {
return r;
break;
case ARG_REPLACE:
if (!path_is_absolute(optarg) ||
!endswith(optarg, ".conf")) {
log_error("The argument to --replace= must an absolute path to a config file");
return -EINVAL;
}
arg_replace = optarg;
break;
case ARG_INLINE:
arg_inline = true;
break;
@ -1799,14 +1813,76 @@ static int parse_argv(int argc, char *argv[]) {
assert_not_reached("Unhandled option");
}
if (arg_replace && optind >= argc) {
log_error("When --replace= is given, some configuration items must be specified");
return -EINVAL;
}
return 1;
}
static int parse_arguments(char **args) {
char **arg;
unsigned pos = 1;
int r;
STRV_FOREACH(arg, args) {
if (arg_inline)
/* Use (argument):n, where n==1 for the first positional arg */
r = parse_line("(argument)", pos, *arg);
else
r = read_config_file(*arg, false);
if (r < 0)
return r;
pos++;
}
return 0;
}
static int read_config_files(const char* dirs, char **args) {
_cleanup_strv_free_ char **files = NULL;
_cleanup_free_ char *p = NULL;
char **f;
int r;
r = conf_files_list_nulstr(&files, ".conf", arg_root, 0, dirs);
if (r < 0)
return log_error_errno(r, "Failed to enumerate sysusers.d files: %m");
if (arg_replace) {
r = conf_files_insert(&files, arg_root, dirs, arg_replace);
if (r < 0)
return log_error_errno(r, "Failed to extend sysusers.d file list: %m");
p = path_join(arg_root, arg_replace, NULL);
if (!p)
return log_oom();
}
STRV_FOREACH(f, files)
if (p && path_equal(*f, p)) {
log_debug("Parsing arguments at position \"%s\"…", *f);
r = parse_arguments(args);
if (r < 0)
return r;
} else {
log_debug("Reading config file \"%s\"…", *f);
/* Just warn, ignore result otherwise */
(void) read_config_file(*f, true);
}
return 0;
}
int main(int argc, char *argv[]) {
_cleanup_close_ int lock = -1;
Iterator iterator;
int r, k;
int r;
Item *i;
char *n;
@ -1826,34 +1902,18 @@ int main(int argc, char *argv[]) {
goto finish;
}
if (optind < argc) {
int j;
for (j = optind; j < argc; j++) {
if (arg_inline)
/* Use (argument):n, where n==1 for the first positional arg */
r = parse_line("(argument)", j - optind + 1, argv[j]);
else
r = read_config_file(argv[j], false);
if (r < 0)
goto finish;
}
} else {
_cleanup_strv_free_ char **files = NULL;
char **f;
r = conf_files_list_nulstr(&files, ".conf", arg_root, 0, conf_file_dirs);
if (r < 0) {
log_error_errno(r, "Failed to enumerate sysusers.d files: %m");
goto finish;
}
STRV_FOREACH(f, files) {
k = read_config_file(*f, true);
if (k < 0 && r == 0)
r = k;
}
}
/* If command line arguments are specified along with --replace, read all
* configuration files and insert the positional arguments at the specified
* place. Otherwise, if command line arguments are specified, execute just
* them, and finally, without --replace= or any positional arguments, just
* read configuration and execute it.
*/
if (arg_replace || optind >= argc)
r = read_config_files(conf_file_dirs, argv + optind);
else
r = parse_arguments(argv + optind);
if (r < 0)
goto finish;
/* Let's tell nss-systemd not to synthesize the "root" and "nobody" entries for it, so that our detection
* whether the names or UID/GID area already used otherwise doesn't get confused. After all, even though