Special permission of Linux File: suid sgid sticky

Philosophy of life 2020-11-09 15:42:20
special permission linux file suid


One . About special permissions for files

1. File and directory settings are more than basic permissions :r,w,x, There are also so-called special permissions . Special permissions will have some “ Privilege ”. The special permission is :suid sgid sticky

2. Special permissions for files :suid sgid sticky

  • ​ SUID(set uid Set user ID): limit : Can only be set on binary executables . Invalid directory setting . function : When the program is running, the permissions change from the executor to the program owner
  • ​ SGID: limit : Both can be set for binary executables , You can also set the directory . function : In setting up the SGID Permission directory when creating a file , The group of the newly created file inherits the group of the parent directory
  • ​ Stickybit: Sticky bit permissions are for directories , Invalid for file , Also called anti delete bit

3. this 3 The corresponding value of special permissions is

SUID SGID Stickybit
u+s or u=4 g+s or g=2 o+t or o=1

Two .suid

1.SUID Properties are commonly used on executables , When the user executes the file , Temporary ownership of the execution file . Use ”ls -l” perhaps ”ll” Command to browse files , If the third digit of the executable owner's permission is a lowercase ”s”, This indicates that the execution file has SUID attribute . such as /usr/bin/passwd file

[elk@node5 ~]$ which passwd
/bin/passwd
[elk@node5 ~]$ whereis passwd
passwd: /usr/bin/passwd /etc/passwd /usr/share/man/man1/passwd.1.gz
[elk@node5 ~]$ ll /bin/passwd
-rwsr-xr-x. 1 root root 27832 Jun 10 2014 /bin/passwd
[elk@node5 ~]$ ll /usr/bin/passwd
-rwsr-xr-x. 1 root root 27832 Jun 10 2014 /usr/bin/passwd

2. Ordinary users elk, No, right shadow Permission to write files , however elk The user to use passwd When you change your password , You can modify shadow Contents of the file , What's the reason ?

[root@node5 ~]# ll /etc/shadow
----------. 1 root root 1179 9 month 19 2017 /etc/shadow
[root@node5 ~]# su - mk
Last login : Two 5 month 8 21:07:24 CST 2018pts/0 On
[elk@node5 ~]$ passwd
[root@node5 ~]# vim /etc/shadow # see shadow The document has been elk User modification succeeded .

because mk User execution passwd On command , Authority will be upgraded to root user , So it can be modified successfully .

3. to less Command addition suid jurisdiction

[elk@node5 ~]$ which less
/bin/less
[elk@node5 ~]$ ll /bin/less
-rwxr-xr-x. 1 root root 158240 Jul 31 2015 /bin/less
[elk@node5 ~]$ ll /etc/shadow
---------- 1 root root 1242 Oct 14 02:20 /etc/shadow
[elk@node5 ~]$ less /etc/shadow
/etc/shadow: Permission denied
[elk@node5 ~]$ exit
logout
[root@node5 ~]# chmod u+s /bin/less
[root@node5 ~]# su - elk
Last login: Thu Oct 15 11:39:37 CST 2020 on pts/3
[elk@node5 ~]$ less /etc/shadow
tss:!!:18341::::::
postgres:$6$W/xWXomt$Vry4J0aBsW4EyiMDW90kfzi45lAWKeYwBPBJzdiX3Yj1twH6zn7D9cG8PJXAMhcwTaIiuJNZxCtLFh/Ht6CwK/:18365::::::
esnode:$6$fznP2Oqd$02x2dTMV0kP5Ra780.sw.W06KZVl7ua8sA7QBMfEsYp0iUs1ukz.9H/iqYjToLLLa1TPSGWDC6a8yVJFZCVV5/:18378:0:99999:7:::
elk:$6$An7lKn2Q$dSuliu1h.Wn42GsrRwKPDS6bgEmTR8TlMsWMHIVWIEXOVbsKwvBcKDDNv.Mxki7aOwV8EBASQFAGQ9W.N/LeV.:18548:0:99999:7:::
logstash:$6$9yY5A65j$YzViQt8dC7mb9ID4my1x1o2dZX3ovQbTfsMr3f5UaJkt3THQRMOmt0pq2YIN0W.zlyU/hRlZe.9vocyFepTYl1:18548:0:99999:7:::
# perform less When ordered , User rights have been raised to root jurisdiction
[root@node5 ~]# ps -ef | grep less
root 68019 67976 0 14:57 pts/3 00:00:00 less /etc/shadow
root 68034 58078 0 14:57 pts/5 00:00:00 grep --color=auto less
[elk@node5 ~]$ ll /bin/less
-rwsr-xr-x. 1 root root 158240 Jul 31 2015 /bin/less
[elk@node5 ~]$ exit
logout
[root@node5 ~]# chmod u-s /bin/less
[root@node5 ~]# ll /bin/less
-rwxr-xr-x. 1 root root 158240 Jul 31 2015 /bin/less
[root@node5 ~]# chmod 4755 /bin/less
[root@node5 ~]# ll /bin/less
-rwsr-xr-x. 1 root root 158240 Jul 31 2015 /bin/less
[root@node5 ~]# chmod u-s /bin/less
[root@node5 ~]# ll /bin/less
-rwxr-xr-x. 1 root root 158240 Jul 31 2015 /bin/less

in addition :chmod 4755 /usr/bin/less # Equate to chmod u+s /usr/bin/less

3、 ... and .SGID

1.SGID Both can be set for binary executables , You can also set directories .
2.SGID The function of : In setting up the SGID Permission directory when creating a file , The group of the newly created file inherits the permissions of the parent directory .

[root@node5 ~]# mkdir ceshi
[root@node5 ~]# ll -d ceshi
drwxr-xr-x 2 root root 6 Oct 15 15:10 ceshi
[root@node5 ~]# chmod g+s ceshi
[root@node5 ~]# !ll
ll -d ceshi
drwxr-sr-x 2 root root 6 Oct 15 15:10 ceshi
[root@node5 ~]# chown :elk ceshi
[root@node5 ~]# !ll
ll -d ceshi
drwxr-sr-x 2 root elk 6 Oct 15 15:10 ceshi
[root@node5 ~]# touch ceshi/ceshi.txt
[root@node5 ~]# ll ceshi/ceshi.txt
-rw-r--r-- 1 root elk 0 Oct 15 15:12 ceshi/ceshi.txt

Four .Stickybit

1.Stickybit Only for catalog .
2.Stickybit The function of : The only files created in the directory are root、 Document creator 、 The directory owner can delete .

3.Stickybit Usage of :chmod o+t /tmp/test/

4. example : In the system tmp That's what the catalog looks like

[root@node5 ~]# ll -d /tmp
drwxrwxrwt. 10 root root 4096 Oct 15 10:12 /tmp
版权声明
本文为[Philosophy of life]所创,转载请带上原文链接,感谢

  1. 【计算机网络 12(1),尚学堂马士兵Java视频教程
  2. 【程序猿历程,史上最全的Java面试题集锦在这里
  3. 【程序猿历程(1),Javaweb视频教程百度云
  4. Notes on MySQL 45 lectures (1-7)
  5. [computer network 12 (1), Shang Xuetang Ma soldier java video tutorial
  6. The most complete collection of Java interview questions in history is here
  7. [process of program ape (1), JavaWeb video tutorial, baidu cloud
  8. Notes on MySQL 45 lectures (1-7)
  9. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  10. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  11. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  12. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  13. 【递归,Java传智播客笔记
  14. [recursion, Java intelligence podcast notes
  15. [adhere to painting for 386 days] the beginning of spring of 24 solar terms
  16. K8S系列第八篇(Service、EndPoints以及高可用kubeadm部署)
  17. K8s Series Part 8 (service, endpoints and high availability kubeadm deployment)
  18. 【重识 HTML (3),350道Java面试真题分享
  19. 【重识 HTML (2),Java并发编程必会的多线程你竟然还不会
  20. 【重识 HTML (1),二本Java小菜鸟4面字节跳动被秒成渣渣
  21. [re recognize HTML (3) and share 350 real Java interview questions
  22. [re recognize HTML (2). Multithreading is a must for Java Concurrent Programming. How dare you not
  23. [re recognize HTML (1), two Java rookies' 4-sided bytes beat and become slag in seconds
  24. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  25. RPC 1: how to develop RPC framework from scratch
  26. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  27. RPC 1: how to develop RPC framework from scratch
  28. 一次性捋清楚吧,对乱糟糟的,Spring事务扩展机制
  29. 一文彻底弄懂如何选择抽象类还是接口,连续四年百度Java岗必问面试题
  30. Redis常用命令
  31. 一双拖鞋引发的血案,狂神说Java系列笔记
  32. 一、mysql基础安装
  33. 一位程序员的独白:尽管我一生坎坷,Java框架面试基础
  34. Clear it all at once. For the messy, spring transaction extension mechanism
  35. A thorough understanding of how to choose abstract classes or interfaces, baidu Java post must ask interview questions for four consecutive years
  36. Redis common commands
  37. A pair of slippers triggered the murder, crazy God said java series notes
  38. 1、 MySQL basic installation
  39. Monologue of a programmer: despite my ups and downs in my life, Java framework is the foundation of interview
  40. 【大厂面试】三面三问Spring循环依赖,请一定要把这篇看完(建议收藏)
  41. 一线互联网企业中,springboot入门项目
  42. 一篇文带你入门SSM框架Spring开发,帮你快速拿Offer
  43. 【面试资料】Java全集、微服务、大数据、数据结构与算法、机器学习知识最全总结,283页pdf
  44. 【leetcode刷题】24.数组中重复的数字——Java版
  45. 【leetcode刷题】23.对称二叉树——Java版
  46. 【leetcode刷题】22.二叉树的中序遍历——Java版
  47. 【leetcode刷题】21.三数之和——Java版
  48. 【leetcode刷题】20.最长回文子串——Java版
  49. 【leetcode刷题】19.回文链表——Java版
  50. 【leetcode刷题】18.反转链表——Java版
  51. 【leetcode刷题】17.相交链表——Java&python版
  52. 【leetcode刷题】16.环形链表——Java版
  53. 【leetcode刷题】15.汉明距离——Java版
  54. 【leetcode刷题】14.找到所有数组中消失的数字——Java版
  55. 【leetcode刷题】13.比特位计数——Java版
  56. oracle控制用户权限命令
  57. 三年Java开发,继阿里,鲁班二期Java架构师
  58. Oracle必须要启动的服务
  59. 万字长文!深入剖析HashMap,Java基础笔试题大全带答案
  60. 一问Kafka就心慌?我却凭着这份,图灵学院vip课程百度云