Monitor System User Changes¶

This will demonstrate how to use Scheck to implement a Lua script for checking sensitive files.

• Version: 1.0.7-5-gb83de2d
• Release Date: 2022-08-30 03:31:26
• Supported Operating Systems: linux/arm, linux/arm64, linux/386, linux/amd64

Prerequisites¶

• Scheck is already installed

Development Steps¶

1. Navigate to the installation directory and edit the enable field in the configuration file scheck.conf to set it to true:

...
[scoutput]
   # ##Messages generated during Security Check can be sent to local, http, Alibaba Cloud sls.
   # ##Remote server, e.g., http(s)://your.url
  [scoutput.http]
    enable = true
    output = "http://127.0.0.1:9529/v1/write/security"
  [scoutput.log]
    # ##Local storage can be configured
    enable = false
    output = "/var/log/scheck/event.log"
...

1. Create a manifest file files.manifest under the directory /usr/local/scheck/custom.rules.d (this directory is for user-defined scripts), and edit it as follows:

id         = 'users-checker'
category   = 'system'
level      = 'warn'
title      = 'Monitor System User Changes'
desc       = '{{.Content}}'
cron       = '*/10 * * * *'
instanceId = 'id-xxx'
os_arch    = ["Linux"]

1. In the same directory as the manifest file, create a script file users.lua, and edit it as follows:

   local function check()
       local cache_key="current_users"
       local currents=users()
   
       local old=get_cache(cache_key)
       if not old then
           set_cache(cache_key, currents)
           return
       end
   
       local adds={}
       for i,v in ipairs(currents) do
           local exist=false
           for ii,vv in ipairs(old) do
               if vv["username"] == v["username"] then
                   exist = true
                   break
               end
           end
           if not exist then
               table.insert(adds, v["username"])
           end
       end
   
       local dels={}
       for i,v in ipairs(old) do
           local exist=false
           for ii,vv in ipairs(currents) do
               if vv["username"] == v["username"] then
                   exist = true
                   break
               end
           end
           if not exist then
               table.insert(dels, v["username"])
           end
       end
   
       local content=''
       if #adds > 0 then
           content=content..'New users: '..table.concat(adds, ',')
       end
       if #dels > 0 then
           if content ~= '' then content=content..'; ' end
           content=content..'Deleted users: '..table.concat(dels, ',')
       end
       if content ~= '' then
           trigger({Content=content})
           set_cache(cache_key, currents)
       end
   end
   
   check()
   

2. When a user is added, it will be detected within the next 10 seconds and trigger the trigger function, sending the event to the file /var/log/scheck/event.log, adding a line of data, for example:

users-checker,category=system,level=warn,title=Monitor System User Changes message="New users: xxx" 1617262230001916515