Without sxid, suid & sgid will be in danger- Shangwen network xUP Nange

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# Said in the previous

as everyone knows ,Linux Except under the system r 、w 、x Beyond these basic permissions , also suid 、 sgid as well as sticky This is commonly known as the existence of the three brothers of special authority ; What are the functions of these three special permissions , The following is true suid 、 sgid as well as sticky Explain the role of ：

• SUID jurisdiction ：
  It can only be applied to executable files , When the user executes the execution file , Will temporarily have the permission of the owner of the execution file .passwd The command enables SUID function , So most users are using passwd When the command changes the password , Will temporarily own passwd Order the owner root User's rights .
• SGID jurisdiction ：
  SGID Attributes can be applied to directories or executables . When SGID When attributes are applied to a directory , The owning group of all files or subdirectories created in this directory will be the owning group of this directory . such as /upwendir The owning group of the directory is upwen, When /upwendir The directory has SGID Attribute , Any owning group of files or subdirectories created by users in this directory will upwen; When SGID When attributes are applied to an executable , Other users will temporarily have the permissions of the executable group when using the executable .
• Stikcy jurisdiction ：
  Sticky Attributes can only be applied to directories , When the directory has Sticky Attribute all the files or subdirectories in this directory. No matter what the permissions are, only the owner of the file or subdirectory and root User can delete .
  that , Although the above three permissions are called special permissions , But in fact, it also has security risks and hidden dangers , Next , Let's list bash Command by giving suid The scenario of raising rights with special permission ,Let 's go ! ! !

# once SUID/SGID The case of raising power

We build a new one upnange The average user , And through the bash Give orders to suid(chmod u+s) jurisdiction ：

Next , We carry out bash -p Carry out the right raising operation , At this time upnange Users can view it at will /etc/shadow file ：

# Use sXid Monitor what's going on SUID/SGID

##sXid Definition

SUID/SGID There may be security risks in the file . To reduce risk , We have been from root Has deleted s position , These programs don't absolutely need this privilege , But future and existing files may enable these without notice s position .
sXid It's a multi in one suid/sgid Monitoring program , It aims at regularly starting from cron function . Basically, it will track your s[ug]id Any changes in files and folders . If there is any new 、 No longer set 、 Or they have changed bits or other modes , Then it will report the changes in an easy to read format via email or command line .sXid The task will be performed automatically to find all on your server SUID/SGID And report them .

##sXid install

Source package installation sXid.

After installation ,sXid The corresponding program installation path is /usr/local/bin/sxid

##sXid To configure

We need to put the configuration file in /usr/local/etc/ Under the table of contents :
You can modify... In the configuration file , hold EMAIL=“root” Change to the required user .
Add the following content to the planning task , In this way, you can check periodically according to the planned task Linux Systematic suid | sgid Changes to ：

Conduct manual inspection after configuration

# Said at the end

This time, , We know through bash Raise the right suid&sgid scene , be based on sXid monitor Linux Systematic uid&sgid, These are what we become Linux The essential basic skills of the great God ;UP Brother Nan, help the little friends come here first , Later, through the feedback used by the big guys , Welcome to join the group 11372462, communication IT Industry development and knowledge , I feel this article is useful , You can also ask for attention CSDN, Focus on UPWEN The public, .UP Nange continues to output the purest IT Industry development and knowledge ！