In a multi-tenant deployment, communication is predominately from the main account to the host account, and then from the host to the tenants. However, when a host is first registered, communication is from the host account to the main account.
Two-way communication should always be available between the main account and tenant account so that replies can be sent from the tenant to the main.
The main host and additional hosts communicate using TLS 1.2 over port 443 (this is the default port, but can be configured). Requests to the tenants are sent through the hosts (main or other) on port 443. The hosts forward the requests to the tenant, which listens on ports 18501 and higher.
With a high availability deployment, port 443 is used for communication from :
Main account to high availability group hosts
High availability group hosts to the main account
High availability group hosts to other high availability group hosts in the same host group
Main account to tenants
Host to tenant communication is over port 1850x.
There is no communication between hosts in different high availability groups.
By default, requests are encrypted using TLS using a Cortex XSOAR self-signed certificate. You can replace the certificate by creating your own certificate and private key.
Validation and authorization
Cortex XSOAR uses an internal API key so that the tenants or hosts can verify that the request originates from a main account and not from an unauthorized third party. An internal API key, kept on the main account, is used in all communications, and is passed to the tenants or host when they are created. The internal API key is passed to hosts on installer creation, and to tenants when they are created.
For requests that require authorization (such as when a user wants to view incidents from the main account) the user details are passed down in requests, so the tenant can decipher and query them.
API keys are created by Cortex XSOAR. Requests are sent from an external source, which is received by Cortex XSOAR (usually a tenant) and interpreted as a request from an administrator. In multi-tenant environments, you need to consider where to create the API key.
If created on a main account, it will propagate to all tenants, so anyone with that key can send requests to any tenant in the environment.
If created on a tenant, you can only send requests to that tenant.