doc: initial version of security-model-strategy.md

doc/contributing/security-model-strategy.md

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+# Security Model Strategy
+
+A clear security model, with features like permissions and policy enforcement,
+is a
+[top technical priority](https://github.com/nodejs/node/blob/master/doc/contributing/technical-priorities.md#permissionspoliciessecurity-model)
+of Node.js.
+
+## High-level approach
+
+* Document the security model
+* Document threat models and current state of the art
+* Support experimentation on features like permissions and policies
+* Add a security component in Node.js certification covering
+  the Node.js security model
+
+### Document the security model
+
+The current security model for Node.js is not yet well documented.
+At a high level it is:
+
+* Node.js does not provide a sandbox, both the JavaScript and
+  native code which is run is trusted to not be malicious.
+* The project works to help code running on top of Node.js to avoid
+  making mistakes, but not doing so is not considered a
+  vulnerability in Node.js. Just because you can build something
+  vulnerable with the APIs does not mean there is a vulnerability
+  in Node.js itself.
+
+The project has a goal to better document the security model
+and this section will be expanded when that happens.
+
+Once the security model is documented the project will work
+to add a security component in Node.js certification covering
+the Node.js security model.
+
+### Document threat models and current state of the art
+
+Node.js is used in several different use cases and the
+threats may be different in each use case. The project
+should document the threat models and use that to
+help define the security model in the context of each
+of these use cases.
+
+This section will be expanded as the use case/threat
+models are defined. The initial list includes:
+
+* Server
+* Desktop application
+* Cli
+* Single executable application
+* CI/CD pipeline components
+
+### Support experimentation on features like permissions and policies
+
+The project is not currently planning to provide supported
+sandbox functionality, but wants to support experimentation on
+related features like policies and permission enforcement.
+
+Features in this category should:
+
+* be opt-in, and additional overhead when not enabled must be low
+* limit change in core to just what is needed to enable experimentation
+
+## Current implementation and assets
+
+Node.js has an experimental implementation of
+[policies](https://nodejs.org/docs/latest/api/policy.html#policies).
+
+The core implementation is in:
+
+* [`lib/internal/process/policy.js`](https://github.com/nodejs/node/blob/HEAD/lib/internal/process/policy.js)
+* [`lib/internal/policy`](https://github.com/nodejs/node/blob/HEAD/lib/internal/policy)
+
+along with integration into the CJS and ESM loaders in:
+
+* [`lib/internal/modules/esm`](https://github.com/nodejs/node/blob/HEAD/lib/internal/modules/esm)
+* [`lib/internal/modules/cjs`](https://github.com/nodejs/node/blob/HEAD/lib/internal/modules/cjs)