From 2908a94a565c162eea751f1d7042b75cdc8cd13d Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Wed, 7 Aug 2024 12:32:11 +0100
Subject: su: add test mode

Testing some uses of 'su' can be challenging because any errors
appear in the new console window which may close as a result.

Add the '-t' option to enable test mode.  This starts a new shell
using ShellExecuteEx(), but without elevated privileges and a new
console.  All other options and arguments are handled much as
before, though some differences in behaviour are to be expected due
to the lack of elevated privilege.

Adds 80-96 bytes.

(GitHub issue #438)
---
 loginutils/suw32.c | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/loginutils/suw32.c b/loginutils/suw32.c
index 821071388..11935e326 100644
--- a/loginutils/suw32.c
+++ b/loginutils/suw32.c
@@ -16,14 +16,15 @@
 //kbuild:lib-$(CONFIG_SUW32) += suw32.o
 
 //usage:#define suw32_trivial_usage
-//usage:       "[-W] [-N|-s SHELL] [root]\n"
-//usage:       "or:    su [-W] [-N|-s SHELL] -c CMD_STRING [[--] root [ARG0 [ARG...]]]\n"
-//usage:       "or:    su [-W] [-N|-s SHELL] [--] root [arbitrary sh arguments]"
+//usage:       "[-tW] [-N|-s SHELL] [root]\n"
+//usage:       "or:    su [-tW] [-N|-s SHELL] -c CMD_STRING [[--] root [ARG0 [ARG...]]]\n"
+//usage:       "or:    su [-tW] [-N|-s SHELL] [--] root [arbitrary sh arguments]"
 //usage:#define suw32_full_usage "\n\n"
 //usage:       "Run shell with elevated privileges\n"
 //usage:     "\n    -c CMD    Command to pass to 'sh -c'"
 //usage:     "\n    -s SHELL  Use specified shell"
 //usage:     "\n    -N        Don't close console when shell exits"
+//usage:     "\n    -t        Test mode, no elevation"
 //usage:     "\n    -W        Wait for shell exit code"
 
 #include "libbb.h"
@@ -32,10 +33,13 @@
 enum {
 	OPT_c = (1 << 0),
 	OPT_s = (1 << 1),
-	OPT_N = (1 << 2),
-	OPT_W = (1 << 3)
+	OPT_t = (1 << 2),
+	OPT_N = (1 << 3),
+	OPT_W = (1 << 4)
 };
 
+#define test_mode (opt & OPT_t)
+
 int suw32_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int suw32_main(int argc UNUSED_PARAM, char **argv)
 {
@@ -47,25 +51,25 @@ int suw32_main(int argc UNUSED_PARAM, char **argv)
 	char *bb_path, *cwd, *realcwd, *q, *args;
 	DECLARE_PROC_ADDR(BOOL, ShellExecuteExA, SHELLEXECUTEINFOA *);
 
+	opt = getopt32(argv, "^c:s:tNW" "\0" "s--N:N--s", &opt_command, &opt_shell);
+	argv += optind;
+	if (argv[0]) {
+		if (!test_mode && strcmp(argv[0], "root") != 0) {
+			bb_error_msg_and_die("unknown user '%s'", argv[0]);
+		}
+		++argv;
+	}
+
 #if ENABLE_DROP || ENABLE_CDROP || ENABLE_PDROP
 	// If privilege has been dropped (ELEVATED_PRIVILEGE but not
 	// ADMIN_ENABLED) ShellExecuteEx() thinks we already have elevated
 	// privilege and doesn't raise privilege.  In that case, give up.
-	if (elevation_state() == ELEVATED_PRIVILEGE) {
+	if (!test_mode && elevation_state() == ELEVATED_PRIVILEGE) {
 		xfunc_error_retval = 2;
 		bb_error_msg_and_die("unable to restore privilege");
 	}
 #endif
 
-	opt = getopt32(argv, "^c:s:NW" "\0" "s--N:N--s", &opt_command, &opt_shell);
-	argv += optind;
-	if (argv[0]) {
-		if (strcmp(argv[0], "root") != 0) {
-			bb_error_msg_and_die("unknown user '%s'", argv[0]);
-		}
-		++argv;
-	}
-
 	/* ShellExecuteEx() needs backslash as separator in UNC paths. */
 	if (opt_shell) {
 		bb_path = file_is_win32_exe(opt_shell);
@@ -74,17 +78,21 @@ int suw32_main(int argc UNUSED_PARAM, char **argv)
 		args = NULL;
 	} else {
 		bb_path = xstrdup(bb_busybox_exec_path);
-		args = xasprintf("--busybox ash -t \"BusyBox ash (Admin)\"");
+		args = xstrdup("--busybox ash");
+		if (!test_mode)
+			args = xappendword(args, "-t \"BusyBox ash (Admin)\"");
 	}
 	slash_to_bs(bb_path);
 
 	memset(&info, 0, sizeof(SHELLEXECUTEINFO));
 	info.cbSize = sizeof(SHELLEXECUTEINFO);
 	/* info.fMask = SEE_MASK_DEFAULT; */
-	if (opt & OPT_W)
+	if (opt & (OPT_t|OPT_W))
 		info.fMask |= SEE_MASK_NOCLOSEPROCESS;
+	if (test_mode)
+		info.fMask |= SEE_MASK_NO_CONSOLE;
 	/* info.hwnd = NULL; */
-	info.lpVerb = "runas";
+	info.lpVerb = !test_mode ? "runas" : "open";
 	info.lpFile = bb_path;
 	/*
 	 * It seems that when ShellExecuteEx() runs binaries residing in
@@ -139,7 +147,7 @@ int suw32_main(int argc UNUSED_PARAM, char **argv)
 		goto end;
 	}
 
-	if (opt & OPT_W) {
+	if (opt & (OPT_t|OPT_W)) {
 		DWORD r;
 
 		WaitForSingleObject(info.hProcess, INFINITE);
-- 
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