SUID and SGID are two special permissions in the Linux operating system, which allow ordinary users to have root user permissions when executing certain commands. This article will provide an in-depth analysis of SUID and SGID permissions, including their role, how to set them up and how to prevent malicious use, as well as their security points in Linux.
Table of contents
1.The role of SUID and SGID permissions
2. How to set SUID and SGID permissions
3. How to prevent malicious use of SUID and SGID permissions
1.The role of SUID and SGID permissions
SUID (Set User ID) permissions are used to set permissions when the owner of a file can use the file. If a file has SUID permissions, the owner of the file will have the permissions of the root user to be able to execute the file. SGID (Set Group ID) permissions are used to set the permissions when the group to which the file belongs can use the file. If a file has SGID permissions, all members of the group to which the file belongs will have the permissions of the root user to be able to execute the file.
2. How to set SUID and SGID permissions
To set SUID and SGID permissions you need to use the chmod command. For example, to set SUID permissions for file abc, you can use the following command:
chmod +s abc
To set SGID permissions for file abc, you can use the following command:
chmod g+s abc
3. How to prevent malicious use of SUID and SGID permissions
Since SUID and SGID permissions can give ordinary users the permissions of the root user, malicious users may abuse these permissions, causing system security to be compromised. To prevent malicious use of SUID and SGID permissions, you can take the following measures:
(1) Ordinary users are prohibited from setting SUID and SGID permissions. You can use the u=s or g=s option of the chmod command to prevent ordinary users from setting SUID and SGID permissions.
(2) Ensure that only the root user can set SUID and SGID permissions. You can use the u=s or g=s option of the chmod command to ensure that only the root user can set SUID and SGID permissions.
(3) Regularly check the SUID and SGID permissions in the system. You can use find command and chmod command to search all files in your system and check if they have SUID and SGID permissions. If you find maliciously set SUID and SGID permissions, you should delete or modify them promptly.
4. Security points in Linux
In Linux, SUID and SGID permissions are very important security points. You should ensure that only the root user can set SUID and SGID permissions, and you should regularly check the SUID and SGID permissions in your system to prevent malicious use. In addition, you should also ensure that other security measures in the system are properly implemented, such as prohibiting ordinary users from using sudo commands, regularly backing up system data, etc.