Centralized configuration (agent.conf)

Introduction

Agents can be configured remotely by using the agent.conf file. The following capabilities can be configured remotely:

File Integrity monitoring (syscheck)
Rootkit detection (rootcheck)
Log data collection (localfile)
Security policy monitoring (wodle name="open-scap", wodle name="cis-cat")
Remote commands (wodle name="command")
Labels for agent alerts (labels)
Security Configuration Assessment (sca)
System inventory (syscollector)
Avoid events flooding (client_buffer)
Configure osquery wodle (wodle name="osquery")

Note

When setting up remote commands in the shared agent configuration, you must enable remote commands for Agent Modules. This is enabled by adding the following line to the /var/ossec/etc/local_internal_options.conf file in the agent:

wazuh_command.remote_commands=1

Agent groups

New in version 3.0.0.

Agents can be grouped together in order to send them unique centralized configuration that is group specific. Each agent can belong to more than one group and unless otherwise configured, all agents belong to a group called default.

Note

Check the agent_groups manual to learn how to add groups and assign agents to them.

The manager pushes all files included in the group folder to the agents belonging to this group. For example, all files in /var/ossec/etc/shared/default will be pushed to all agents belonging to the default group.

In case an agent is assigned to multiple groups, all the files contained in each group folder will be merged into one, and subsequently sent to the agents, being the last one the group with the highest priority.

The file ar.conf (active response status) will always be sent to agents even if it is not present in the group folder.

The agent will store the shared files in /var/ossec/etc/shared, not in a group folder.

Below are the files that would be found in this folder on an agent assigned to the debian group. Notice that these files are pushed to the agent from the manager's /var/ossec/etc/shared/debian folder.

Manager

Agent (Group: 'debian')

/var/ossec/etc/shared/
├── ar.conf
├── debian
│   ├── agent.conf
│   ├── cis_debian_linux_rcl.txt
│   ├── cis_rhel5_linux_rcl.txt
│   ├── cis_rhel6_linux_rcl.txt
│   ├── cis_rhel7_linux_rcl.txt
│   ├── cis_rhel_linux_rcl.txt
│   ├── cis_sles11_linux_rcl.txt
│   ├── cis_sles12_linux_rcl.txt
│   ├── custom_rootcheck.txt
│   ├── debian_ports_check.txt
│   ├── debian_test_files.txt
│   ├── merged.mg
│   ├── rootkit_files.txt
│   ├── rootkit_trojans.txt
│   ├── system_audit_rcl.txt
│   ├── system_audit_ssh.txt
│   ├── win_applications_rcl.txt
│   ├── win_audit_rcl.txt
│   └── win_malware_rcl.txt
└── default
    ├── agent.conf
    ├── cis_debian_linux_rcl.txt
    ├── cis_rhel5_linux_rcl.txt
    ├── cis_rhel6_linux_rcl.txt
    ├── cis_rhel7_linux_rcl.txt
    ├── cis_rhel_linux_rcl.txt
    ├── cis_sles11_linux_rcl.txt
    ├── cis_sles12_linux_rcl.txt
    ├── merged.mg
    ├── rootkit_files.txt
    ├── rootkit_trojans.txt
    ├── system_audit_rcl.txt
    ├── system_audit_ssh.txt
    ├── win_applications_rcl.txt
    ├── win_audit_rcl.txt
    └── win_malware_rcl.txt

/var/ossec/etc/shared/
├── ar.conf
├── agent.conf
├── cis_debian_linux_rcl.txt
├── cis_rhel5_linux_rcl.txt
├── cis_rhel6_linux_rcl.txt
├── cis_rhel7_linux_rcl.txt
├── cis_rhel_linux_rcl.txt
├── cis_sles11_linux_rcl.txt
├── cis_sles12_linux_rcl.txt
├── custom_rootcheck.txt
├── debian_ports_check.txt
├── debian_test_files.txt
├── merged.mg
├── rootkit_files.txt
├── rootkit_trojans.txt
├── system_audit_rcl.txt
├── system_audit_ssh.txt
├── win_applications_rcl.txt
├── win_audit_rcl.txt
└── win_malware_rcl.txt

The proper syntax of agent.conf is shown below along with the process for pushing the configuration from the manager to the agent.

agent.conf

The agent.conf is only valid on server installations.

The agent.conf may exist in each group folder at /var/ossec/etc/shared.

For example, for the group1 group, it is in /var/ossec/etc/shared/group1. Each of these files should be readable by the ossec user.

Options

name	Allows assignment of the block to one particular agent.
	Allowed values	Any agent name
os	Allows assignment of the block to an operating system.
	Allowed values	Any OS family
profile	Allows assignment of a profile name to a block. Any agent configured to use the defined profile may use the block.
	Allowed values	Any defined profile

Examples

<agent_config name=”agent01”>
...
<agent_config os="Linux">
...
<agent_config profile="UnixHost">

Centralized configuration process

The following is an example of how a centralized configuration can be done.

Configure the agent.conf file:

Edit the file corresponding to the agent group. For example, for the default group, edit the file /var/ossec/etc/shared/default/agent.conf. If the file does not exist, create it:

# touch /var/ossec/etc/shared/default/agent.conf
# chown ossec:ossec /var/ossec/etc/shared/default/agent.conf
# chmod 640 /var/ossec/etc/shared/default/agent.conf

Several configurations may be created based on the name, OS or profile of an agent.

<agent_config name="agent_name">
    <localfile>
        <location>/var/log/my.log</location>
        <log_format>syslog</log_format>
    </localfile>
</agent_config>

<agent_config os="Linux">
    <localfile>
        <location>/var/log/linux.log</location>
        <log_format>syslog</log_format>
    </localfile>
</agent_config>

<agent_config profile="database">
    <localfile>
        <location>/var/log/database.log</location>
        <log_format>syslog</log_format>
    </localfile>
</agent_config>

Note

The profile option uses the values defined on the <config-profile> setting from the client configuration.

Run /var/ossec/bin/verify-agent-conf:

Each time you make a change to the agent.conf file, it is important to check for configuration errors. If any errors are reported by this check, they must be fixed before the next step. Failure to perform this step may allow errors to be pushed to agents which may prevent the agents from running. At that point, it is very likely that you will be forced to visit each agent manually to recover them.
Push the configuration to the agents:

With every agent keepalive (10 seconds default), the manager looks to see if a new version of agent.conf is available. When a new version is available, it automatically pulls the new file. However, the new agent.conf is not used by the agent until the next time the agent is restarted, as in step 5.

Note

Restarting the manager will make the new agent.conf file available to the agents more quickly.

Confirm that the agent received the configuration:

The agent_groups tool or the API can show whether the group is synchronized in the agent:

# curl -u foo:bar -X GET "http://localhost:55000/agents/001/group/is_sync?pretty"

{
    "error": 0,
    "data": {
        "synced": true
    }
}

# /var/ossec/bin/agent_groups -S -i 001

Agent '001' is synchronized.

Restart the agent:
By default, the agent restarts by itself automatically when it receives a new shared configuration.

If auto_restart has been disabled (in the <client> section of Local configuration), the agent will have to be manually restarted so that the new agent.conf file will be used. This can be done as follows:
# /var/ossec/bin/agent_control -R -u 1032
Wazuh agent_control: Restarting agent: 1032

Precedence

It's important to understand which configuration file takes precedence between ossec.conf and agent.conf when central configuration is used. When central configuration is utilized, the local and the shared configuration are merged, however, the ossec.conf file is read before the shared agent.conf and the last configuration of any setting will overwrite the previous. Also, if a file path for a particular setting is set in both of the configuration files, both paths will be included in the final configuration.

For example:

Let's say we have this configuration in the ossec.conf file:

<sca>
  <enabled>no</enabled>
  <scan_on_start>yes</scan_on_start>
  <interval>12h</interval>
  <skip_nfs>yes</skip_nfs>

  <policies>
    <policy>system_audit_rcl.yml</policy>
    <policy>system_audit_ssh.yml</policy>
    <policy>system_audit_pw.yml</policy>
  </policies>
</sca>

and this configuration in the agent.conf file.

<sca>
  <enabled>yes</enabled>

  <policies>
    <policy>cis_debian_linux_rcl.yml</policy>
  </policies>
</sca>

The final configuration will enable the Security Configuration Assessment module. In addition, it will add the cis_debian_linux_rcl.yml to the list of scanned policies. In other words, the configuration located at agent.conf will overwrite the one of the ossec.conf.

How to ignore shared configuration

Whether for any reason you don't want to apply the shared configuration in a specific agent, it can be disabled by adding the following line to the /var/ossec/etc/local_internal_options.conf file in that agent:

agent.remote_conf=0

Download configuration files from remote location

Wazuh manager has the capability to download configuration files like merged.mg as well as other files to be merged for the groups that you want to.

To use this feature, we need to put a yaml file named files.yml under the directory /var/ossec/etc/shared/. When the manager starts, it will read and parse the file.

The files.yml has the following structure as shown in the following example:

groups:
    my_group_1:
        files:
            agent.conf: https://example.com/agent.conf
            rootcheck.txt: https://example.com/rootcheck.txt
            merged.mg: https://example.com/merged.mg
        poll: 15

    my_group_2:
        files:
            agent.conf: https://example.com/agent.conf
        poll: 200

agents:
    001: my_group_1
    002: my_group_2
    003: another_group

Here we can distinct the two main blocks: groups and agents.

In the groups block we define the group name from which we want to download the files.
- If the group doesn't exists, it will be created.
- If a file has the name merged.mg, only this file will be downloaded. Then it will be validated.
- The poll label indicates the download rate in seconds of the specified files.
In the agents block, we define for each agent the group to which we want it to belong.
This configuration can be changed on the fly. The manager will reload the file and parse it again so there is no need to restart the manager every time.

The information about the parsing is shown on the /var/ossec/logs/ossec.log file. For example:
- Parsing is successful:
INFO: Successfully parsed of yaml file: /etc/shared/files.yml
- File has been changed:
INFO: File '/etc/shared/files.yml' changed. Reloading data
- Parsing failed due to bad token:
INFO: Parsing file '/etc/shared/files.yml': unexpected identifier: 'group'
- Download of file failed:
ERROR: Failed to download file from url: https://example.com/merged.mg
- Downloaded merged.mg file is corrupted or not valid:
ERROR: The downloaded file '/var/download/merged.mg' is corrupted.