su: properly quote command

Previously the command passed to the elevated shell was placed
in literal double quotes on the command line.  Instead it should
be subject to full quoting by the quote_arg() function.

Tweak command line processing.

Costs 24-32 bytes.

1 files changed, 15 insertions, 8 deletions

diff --git a/loginutils/suw32.c b/loginutils/suw32.c
index 3500c08db..79637dd77 100644
--- a/loginutils/suw32.c
+++ b/loginutils/suw32.c
@@ -27,14 +27,19 @@
 int suw32_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int suw32_main(int argc UNUSED_PARAM, char **argv)
 {
-        char *opt_command = NULL;
         SHELLEXECUTEINFO info;
-        char *bb_path, *cwd;
+        unsigned opts, c_opt;
+        char *command, *bb_path, *cwd;
         DECLARE_PROC_ADDR(BOOL, ShellExecuteExA, SHELLEXECUTEINFOA *);
 
-        getopt32(argv, "c:", &opt_command);
-        if (argv[optind])
+        opts = getopt32(argv, "c");
+        c_opt = opts & 1;
+        argv += optind;
+        command = c_opt ? *argv++ : NULL;
+        if ((c_opt && !command) || (!c_opt && command) || *argv) {
+                // -c without CMD, operand without -c , or surplus arguments
                 bb_show_usage();
+        }
 
         /* ShellExecuteEx() needs backslash as separator in UNC paths. */
         bb_path = xstrdup(bb_busybox_exec_path);
@@ -58,10 +63,12 @@ int suw32_main(int argc UNUSED_PARAM, char **argv)
          */
         cwd = xmalloc_realpath(getcwd(NULL, 0));
         info.lpParameters =
-                xasprintf("--busybox ash -d \"%s\" -t \"BusyBox ash (Admin)\" ", cwd);
-        if (opt_command)
-                info.lpParameters =
-                        xasprintf("%s -s -c \"%s\"", info.lpParameters, opt_command);
+                xasprintf("--busybox ash -d %s -t \"BusyBox ash (Admin)\"",
+                                                quote_arg(cwd));
+        if (c_opt) {
+                info.lpParameters = xappendword(info.lpParameters, "-s -c --");
+                info.lpParameters = xappendword(info.lpParameters, quote_arg(command));
+        }
         /* info.lpDirectory = NULL; */
         info.nShow = SW_SHOWNORMAL;