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# Using WebAssembly to run, extend, and secure your application

WebAssembly has outgrown the browser. It is now a powerhouse for backend security. Learn how WASI sandboxing neutralizes supply chain threats in your cloud-native apps.

- **Speakers:** [Niels Tanis](https://www.wearedevelopers.com/@niels-tanis)
- **Event:** World Congress 2023
- **Published:** August 11, 2023
- **Duration:** 25:08
- **URL:** https://www.wearedevelopers.com/videos/652-using-webassembly-to-run-extend-and-secure-your-application

## Summary

WebAssembly (Wasm) has evolved from a browser-centric solution into a robust, portable compilation target capable of securing and extending backend application architectures. Originally designed as a fast, secure binary format for running native code within web browsers, Wasm provides inherent security advantages such as linear memory sandboxing and strict control-flow integrity. By compiling native execution engines—such as the .NET Common Language Runtime (CLR)—directly to WebAssembly, developers can seamlessly execute dynamic code across diverse platforms while maintaining baseline performance and insulating the host from malicious modules.

The true backend potential of the technology emerges through the WebAssembly System Interface (WASI). Championed by the Bytecode Alliance, WASI introduces a POSIX-inspired, capability-based security model that strictly governs how non-web modules interact with host resources. Instead of granting global access by default, WASI forces systems to explicitly map permissions for file directory interactions, maximum memory consumption quotas, and compute "fuel." This zero-trust architecture has profound implications for cloud-native deployment, enabling WebAssembly to operate alongside traditional Docker containers natively, providing a significantly smaller memory footprint and a drastically reduced attack surface.

As modern engineering relies heavily on third-party dependencies, host runtimes like Wasmtime leverage this architecture to enable "nano-processes" that actively mitigate software supply chain vulnerabilities. By isolating individual dependencies into discrete execution sandboxes, the Wasm component model ensures that a compromised package cannot unilaterally access centralized system APIs. Modules must communicate via explicitly defined interface types governed by strict runtime policies. While this entire security model ultimately depends on the code correctness and rigorous fuzzing of the underlying host runtime itself, WebAssembly’s trajectory establishes it as a highly secure, rapid foundation for the next generation of serverless functions and composable microservices.

**Keywords:** webassembly runtime execution, wasi system interface, wasmtime host environment, capability-based security model, linear memory sandboxing, control-flow integrity validation, docker container alternatives, cloud-native deployment patterns, software supply chain security, webassembly component model, interface types communication, lightweight serverless functions, zero-trust nano-processes, bytecode alliance standards, compute fuel quotas

## Chapters

1. **Introduction to WebAssembly as a compilation target** (00:00) — WebAssembly acts as a high-performance compilation target capable of natively executing logic across diverse application environments.
1. **Early implementations of WebAssembly across major industries** (01:48) — Engineering teams rapidly adapted WebAssembly to migrate monolithic application code into the browser and target multiple platforms simultaneously.
1. **Core design principles of the WebAssembly standard** (03:11) — WebAssembly prioritizes fast binary instructions, readable code structures, default sandboxing, and strict backward compatibility to ensure web stability.
1. **Memory isolation and module ownership in WebAssembly** (05:08) — WebAssembly restricts memory access entirely by confining module operations to a specific contiguous mutable array without cross-module visibility.
1. **Enforcing code flow integrity within WebAssembly executions** (06:01) — The core compilation phase embeds execution maps that instantly panic and halt code flow upon detecting logical deviations.
1. **Running framework execution engines inside the browser** (07:01) — Standard framework engines compiled into WebAssembly transform default virtual machines into functional browser executables using JavaScript bridges.
1. **Extending capabilities with the WebAssembly System Interface** (08:25) — The Bytecode Alliance created WASI to safely expose external system interactions and host capabilities inside strict non-web boundaries.
1. **The coexistence of Docker and WebAssembly modules** (10:35) — Lightweight module deployments integrate alongside traditional Docker frameworks to increase system flexibility and reduce runtime footprint overhead.
1. **Enforcing local file permissions with capability-based security** (11:35) — Enforcing strict capability-based authorization parameters entirely prevents isolated modules from interacting with native system files without explicit flags.
1. **Extending managed applications with external Rust components** (15:21) — Cross-language setups require strict directory mapping constraints to maintain strong capability-based protections when calling external module dependencies.
1. **Preventing dependency vulnerabilities with the component model** (18:37) — Isolating transitive operations inside nanoprocesses effectively blocks vulnerable external packages from automatically inheriting system access rights.
1. **Testing the security posture of WebAssembly runtimes** (21:43) — Rigorous security audits and systematic fuzzing verify that underlying runtime engines gracefully resist unauthorized execution attempts.

## Related Moments

- [Core principles and security model of WebAssembly](https://www.wearedevelopers.com/videos/637-webassembly-disassembled) (from "WebAssembly: Disassembled")
- [The origins and design principles of WebAssembly](https://www.wearedevelopers.com/videos/673-fun-with-paas-how-to-use-cloud-foundry-and-its-uniqueness-in-creative-ways) (from "Fun with PaaS – How to use Cloud Foundry and its uniqueness in creative ways")
- [Core concepts of WebAssembly portability and sandboxed execution](https://www.wearedevelopers.com/videos/100094-from-bytes-to-execution-writing-a-webassembly-runtime-in-rust) (from "From Bytes to Execution: Writing a WebAssembly Runtime in Rust")
- [Core concepts and execution mechanics of WebAssembly modules](https://www.wearedevelopers.com/videos/972-webassembly-the-next-frontier-of-cloud-computing) (from "WebAssembly: The Next Frontier of Cloud Computing")
- [Origins and design goals of WebAssembly](https://www.wearedevelopers.com/videos/687-the-future-of-cloud-is-webassembly) (from "The Future of Cloud is WebAssembly")
- [Introduction to WebAssembly in a cloud computing context](https://www.wearedevelopers.com/videos/972-webassembly-the-next-frontier-of-cloud-computing) (from "WebAssembly: The Next Frontier of Cloud Computing")

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