util: add shell_maybe_quote() call for preparing a string for shell cmdline inclusion

If necessary the passed string is enclosed in "", and all special
characters escapes.

This also ports over usage in bus-util.c and job.c to use this, instead
of a incorrect local implementation that forgets to properly escape.

src/core/job.c

@@ -674,15 +674,13 @@ static void job_print_status_message(Unit *u, JobType t, JobResult result) {
                         break;
 
                 case JOB_FAILED: {
-                        bool quotes;
+                        _cleanup_free_ char *quoted = NULL;
 
-                        quotes = chars_intersect(u->id, SHELL_NEED_QUOTES);
+                        quoted = shell_maybe_quote(u->id);
 
                         manager_flip_auto_status(u->manager, true);
                         unit_status_printf(u, ANSI_HIGHLIGHT_RED_ON "FAILED" ANSI_HIGHLIGHT_OFF, format);
-                        manager_status_printf(u->manager, STATUS_TYPE_NORMAL, NULL,
-                                              "See \"systemctl status %s%s%s\" for details.",
-                                              quotes ? "'" : "", u->id, quotes ? "'" : "");
+                        manager_status_printf(u->manager, STATUS_TYPE_NORMAL, NULL, "See 'systemctl status %s' for details.", strna(quoted));
                         break;
                 }
 

src/libsystemd/sd-bus/bus-util.c

@@ -1735,16 +1735,15 @@ static int check_wait_response(BusWaitForJobs *d, bool quiet) {
                 else if (streq(d->result, "unsupported"))
                         log_error("Operation on or unit type of %s not supported on this system.", strna(d->name));
                 else if (!streq(d->result, "done") && !streq(d->result, "skipped")) {
-                        if (d->name) {
-                                bool quotes;
+                        _cleanup_free_ char *quoted = NULL;
 
-                                quotes = chars_intersect(d->name, SHELL_NEED_QUOTES);
+                        if (d->name)
+                                quoted = shell_maybe_quote(d->name);
 
-                                log_error("Job for %s failed. See \"systemctl status %s%s%s\" and \"journalctl -xe\" for details.",
-                                          d->name,
-                                          quotes ? "'" : "", d->name, quotes ? "'" : "");
-                        } else
-                                log_error("Job failed. See \"journalctl -xe\" for details.");
+                        if (quoted)
+                                log_error("Job for %s failed. See 'systemctl status %s' and 'journalctl -xe' for details.", d->name, quoted);
+                        else
+                                log_error("Job failed. See 'journalctl -xe' for details.");
                 }
         }
 

src/shared/util.c

@@ -1332,7 +1332,8 @@ char *cescape(const char *s) {
 
         assert(s);
 
-        /* Does C style string escaping. */
+        /* Does C style string escaping. May be be reversed with
+         * cunescape(). */
 
         r = new(char, strlen(s)*4 + 1);
         if (!r)
@@ -1542,7 +1543,7 @@ char *xescape(const char *s, const char *bad) {
 
         /* Escapes all chars in bad, in addition to \ and all special
          * chars, in \xFF style escaping. May be reversed with
-         * cunescape. */
+         * cunescape(). */
 
         r = new(char, strlen(s) * 4 + 1);
         if (!r)
@@ -8035,3 +8036,43 @@ int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char
 
         return 0;
 }
+
+char *shell_maybe_quote(const char *s) {
+        const char *p;
+        char *r, *t;
+
+        assert(s);
+
+        /* Encloses a string in double quotes if necessary to make it
+         * OK as shell string. */
+
+        for (p = s; *p; p++)
+                if (*p <= ' ' ||
+                    *p >= 127 ||
+                    strchr(SHELL_NEED_QUOTES, *p))
+                        break;
+
+        if (!*p)
+                return strdup(s);
+
+        r = new(char, 1+strlen(s)*2+1+1);
+        if (!r)
+                return NULL;
+
+        t = r;
+        *(t++) = '"';
+        t = mempcpy(t, s, p - s);
+
+        for (; *p; p++) {
+
+                if (strchr(SHELL_NEED_ESCAPE, *p))
+                        *(t++) = '\\';
+
+                *(t++) = *p;
+        }
+
+        *(t++)= '"';
+        *t = 0;
+
+        return r;
+}

src/shared/util.h

@@ -1090,3 +1090,5 @@ int syslog_parse_priority(const char **p, int *priority, bool with_facility);
 void cmsg_close_all(struct msghdr *mh);
 
 int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath);
+
+char *shell_maybe_quote(const char *s);

src/test/test-util.c

@@ -1542,6 +1542,24 @@ static void test_sparse_write(void) {
         test_sparse_write_one(fd, test_e, sizeof(test_e));
 }
 
+static void test_shell_maybe_quote_one(const char *s, const char *expected) {
+        _cleanup_free_ char *r;
+
+        assert_se(r = shell_maybe_quote(s));
+        assert_se(streq(r, expected));
+}
+
+static void test_shell_maybe_quote(void) {
+
+        test_shell_maybe_quote_one("", "");
+        test_shell_maybe_quote_one("\\", "\"\\\\\"");
+        test_shell_maybe_quote_one("\"", "\"\\\"\"");
+        test_shell_maybe_quote_one("foobar", "foobar");
+        test_shell_maybe_quote_one("foo bar", "\"foo bar\"");
+        test_shell_maybe_quote_one("foo \"bar\" waldo", "\"foo \\\"bar\\\" waldo\"");
+        test_shell_maybe_quote_one("foo$bar", "\"foo\\$bar\"");
+}
+
 int main(int argc, char *argv[]) {
         log_parse_environment();
         log_open();
@@ -1619,6 +1637,7 @@ int main(int argc, char *argv[]) {
         test_same_fd();
         test_uid_ptr();
         test_sparse_write();
+        test_shell_maybe_quote();
 
         return 0;
 }