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Check the Change Implementation of Sensitive Files

This time, we will show how to use Scheck to check the lua script implementation of sensitive files.

  • Version: 1.0.7-5-gb83de2d
  • Release date: 2022-08-30 03:31:26
  • Operating system support: linux/arm,linux/arm64,linux/386,linux/amd64

Preconditions

Development Steps

  1. Go to the installation directory and edit the configuration file scheck.conf to set the enable field totrue:
...
[scoutput]
   # ##Messages generated during Sheck can be sent to local, http and Alibaba Cloud sls
   # ##Remote server, such as http(s)://your.url
  [scoutput.http]
    enable = true
    output = "http://127.0.0.1:9529/v1/write/security"
  [scoutput.log]
    # ##Configurable local storage
    enable = false
    output = "/var/log/scheck/event.log"
...
  1. Create a new manifest file files.manifest under the directory /usr/local/scheck/custom.rules.d (this directory is the user-defined script directory) and edit it as follows:
id       = 'check-file'
category = 'system'
level    = 'warn'
title    = 'monitor file changes'
desc     = 'the File {{.File}} has changed'
cron     = '*/10 * * * *' #Indicate that the lua script is executed every 10 seconds
os_arch  = ["Linux"]
  1. Create a new script file files.lua in the manifest file sibling directory and edit it as follows:
local files={
    '/etc/passwd',
    '/etc/group'
}

local function check(file)
    local cache_key=file
    local hashval = file_hash(file)

    local old = get_cache(cache_key)
    if not old then
        set_cache(cache_key, hashval)
        return
    end

    if old ~= hashval then
        trigger({File=file})
        set_cache(cache_key, hashval)
    end
end

for i,v in ipairs(files) do
    check(v)
end
  1. When a sensitive file is altered, the next 10 seconds will detect and trigger the trigger function, sending the event to the file /var/log/scheck/event.log, adding a row of data, for example: 
check-file-01,category=security,level=warn,title=monitor file changes message="file /etc/passwd changed" 1617262230001916515

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