From 52a850159daee33b96ca30deea3a91588e8a26ce Mon Sep 17 00:00:00 2001
From: TING-JUN WANG <levi900227@gmail.com>
Date: Tue, 25 Jun 2024 00:49:47 +0800
Subject: [PATCH] fix: complete. Some filesystem not support SUID

---
 tool/Makefile    | 14 ++++++++------
 tool/setup_uid.c | 19 ++++++++++++++++++-
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/tool/Makefile b/tool/Makefile
index 95afa3e..f34ea92 100644
--- a/tool/Makefile
+++ b/tool/Makefile
@@ -1,12 +1,14 @@
 CC = gcc
 CFLAGS = -Wall -Wextra -std=c99
 
-all: setup_uid
+all: setup-uid
 
-setup_uid: setup_uid.c
-	$(CC) $(CFLAGS) -o setup_uid setup_uid.c
-	sudo chown root:root setup_uid
-	sudo chmod +s setup_uid
+setup-uid: setup_uid.c
+	$(CC) $(CFLAGS) -o setup-uid setup_uid.c
+	sudo chown root:root setup-uid
+	sudo cp ./setup-uid /usr/bin
+	sudo chmod +s /usr/bin/setup-uid
 
 clean:
-	sudo rm setup_uid
+	sudo rm setup-uid
+	sudo rm /usr/bin/setup-uid
diff --git a/tool/setup_uid.c b/tool/setup_uid.c
index 7500b8d..680f50d 100644
--- a/tool/setup_uid.c
+++ b/tool/setup_uid.c
@@ -1,8 +1,10 @@
+#define _GNU_SOURCE         /* See feature_test_macros(7) */
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
 #include <unistd.h>
 #include <string.h>
+#include <sys/types.h>
 
 bool check_user(char *filename, char *username, unsigned long *new_start) {
     /*
@@ -57,7 +59,7 @@ void insert_user(char *filename, char *username, unsigned long start) {
         exit(1);
     }
     char new_line[100];
-    sprintf(new_line, "%s:%lu:%d\n", username, start, 65535);
+    sprintf(new_line, "%s:%lu:%d\n", username, start, 65536);
     fputs(new_line, fp);
     fclose(fp);
     printf("[SUCCESS] %s has been inserted in %s\n", username, filename);
@@ -65,8 +67,23 @@ void insert_user(char *filename, char *username, unsigned long start) {
 
 
 int main() {
+    int ret;
     char *username = getlogin();
 
+    uid_t ruid, euid, suid;
+    getresuid(&ruid, &euid, &suid);
+    printf("ruid=%d, euid=%d, suid=%d\n", ruid, euid, suid);
+
+    ret = setuid(0);
+    printf("ret=%d\n", ret);
+    if (ret != 0) {
+        perror("Error:");
+        exit(1);
+    }
+
+    getresuid(&ruid, &euid, &suid);
+    printf("ruid=%d, euid=%d, suid=%d\n", ruid, euid, suid);
+
     char filenames[2][20] = {
         "/etc/subuid", "/etc/subgid"
     };