Every Wazuh agent sends data to the Wazuh manager via a secure way called OSSEC message protocol. This protocol encrypts messages using a pre-shared key. In a fresh install, if you didn't register and configure your agent during the installation time, the agent can't communicate with the manager due to the lack of this pre-shared key.
The registration process consists of a mechanism to create a trusted relationship between the Manager and an Agent. This process could be done in a Manager itself or with a registration service. This service runs on the Manager, where an Agent could request a pre-shared key using some credentials. The Manager will reply with the key and store the new Agent in a local database.
Another approach is using the Wazuh API, this is just a wrapper for local registration on Wazuh manager.
The manager uses the file
/var/ossec/etc/client.keys to store the registration record of each agent, which includes ID, name, IP, and key. Example:
001 Server1 any e20e0394dca71bacdea57d4ca25d203f836eca12eeca1ec150c2e5f4309a653a 002 ServerProd 188.8.131.52 b0c5548beda537daddb4da698424d0856c3d4e760eaced803d58c07ad1a95f4c 003 DBServer 192.168.0.1/24 8ec4843da9e61647d1ec3facab542acc26bd0e08ffc010086bb3a6fc22f6f65b
The agents also have the file
/var/ossec/etc/client.keys containing only their own registration record. Example for
001 Server1 any e20e0394dca71bacdea57d4ca25d203f836eca12eeca1ec150c2e5f4309a653a
Basic data for registering an agent
In order to register an agent, it is necessary to provide the name and the IP of the agent.
There are several ways to set the agent IP:
Any IP: Allow the agent to connect from any IP address. Example:
Fixed IP: Allow the agent to connect only from the specified IP. Example:
ServerProdhas the IP
Range IP: Allow the agent to connect from the specified range of IPs. Example:
DBServerhas the IP range
Some registration methods automatically detect the IP of the agent during the registration process.
Here you can find different methods to register the Wazuh agents:
If you're running Wazuh in cluster mode, refer to the Configuring a cluster section to get more details about the registration process in the cluster.