Which default authentication is used by Ansible modules for Oracle Cloud Infrastructure (OCO for making API requests?

The Oracle Cloud Infrastructure (OCI) Ansible modules are built on top of the OCI SDK for Python. The SDK's default authentication mechanism is to look for a configuration file located at ~/.oci/config. This file contains the necessary credentials for API Key Authentication, including user and tenancy OCIDs, a key fingerprint, and the path to the private API key file. While other methods like instance principal are supported and are very useful when running on an OCI instance, the primary default method the SDK attempts first is API Key Authentication via the config file.

A. OAuth is a standard for authorization, but it is not the default authentication method used by the OCI Ansible modules for API requests.
B. Resource Principal Authentication is used by OCI services like Functions to authorize API calls, not the default for Ansible running on a compute instance.
C. Instance principal authentication is a valid method, but the SDK first checks for the API key config file by default before attempting to use instance principals.

1. Oracle Cloud Infrastructure Ansible Collection Documentation, SDK and CLI Configuration, "If authtype is not specified, the SDK will default to using the API key from the config file. If the config file is not found, the SDK will try to use instance principal." This explicitly states API key from the config file is the default.

2. Oracle Cloud Infrastructure Documentation, SDK for Python - Configuration, "By default, the SDK looks for a configuration file named config in the ~/.oci directory." This confirms the default behavior of the underlying SDK.