Centralized configuration (agent.conf)

Introduction

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

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

Agents can be grouped together in order to send them a 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 /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 wazuh user.

Options

name

Assigns the block to agents with specific names.

Allowed values

Any regular expression that matches the agent name.

os

Assigns the block to agents on specific operating systems.

Allowed values

Any regular expression that matches the agent OS information.

profile

Assigns the block to agents with specific profiles as defined in client configuration.

Allowed values

Any regular expression that matches the agent profile.

Centralized configuration process

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

  1. 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 wazuh:wazuh /var/ossec/etc/shared/default/agent.conf
# chmod 660 /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.

  2. 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.

  3. Push the configuration to the agents:

    With every agent keepalive (10 seconds default), the agent sends to the manager the checksum of its merge.md file and the manager compares it with the current one. If the received checksum differs from the available one, the Wazuh manager pushes the new file to the agent. The agent will start using the new configuration after being restarted.

    Note

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

  4. Confirm that the agent received the configuration:

    The agent_groups tool or the Wazuh API endpoint GET /agents can show whether the group configuration is synchronized in the agent or not:

    # curl -k -X GET "https://localhost:55000/agents?agents_list=001&select=group_config_status&pretty=true" -H  "Authorization: Bearer $TOKEN"

    {
   "data": {
      "affected_items": [
         {
            "group_config_status": "synced",
            "id": "001"
         }
      ],
      "total_affected_items": 1,
      "total_failed_items": 0,
      "failed_items": []
   },
   "message": "All selected agents information was returned",
   "error": 0
}

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

    Agent '001' is synchronized.

  5. 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 the central configuration is used. When this 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

The 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 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 distinguish the two main blocks: groups and agents.

  1. In the groups block we define the group name from which we want to download the files.

    • If the group doesn't exist, 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.

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.