Swift.org's SwiftNIO SSH Implementation
Original post SwiftNIO SSH Implementation
Article Summary
Cory Benfield from Apple's Cloud Services team just open-sourced SwiftNIO SSH, bringing programmatic SSH capabilities to Swift. Think libssh2, not openssh: this isn't a ready-made client, it's the building blocks for something more interesting.
SwiftNIO SSH is a new library that lets Swift developers build custom SSH clients and servers programmatically. Instead of shelling out to command-line SSH, you can now handle SSH connections directly in your Swift code, opening up creative possibilities beyond traditional remote shell access.
Key Takeaways
- Supports SSHv2 with modern crypto: Ed25519, ECDSA, AES-GCM, x25519 key exchange
- Uses child channel abstraction to handle SSH's multiplexed protocol elegantly
- Enables creative SSH uses like embedded Python interpreters or chat servers
- Handles both direct and reverse TCP port forwarding programmatically
- Fully async authentication delegates support disk reads without blocking
Swift developers can now build custom SSH implementations directly into their services without spawning subprocesses or wrapping C libraries.
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What This Article Covers
Swift developers had no built-in way to implement SSH protocol endpoints. They had to either run openssh as a subprocess or wrap C libraries like libssh2 when they needed service-to-service command invocation.
Cory Benfield's team at Apple created SwiftNIO SSH, a ChannelHandler that implements SSHv2 protocol logic. It supports session channels, TCP port forwarding, and async authentication delegates without needing external SSH binaries.
Developers can now write custom SSH servers and clients directly in Swift on any platform that SwiftNIO supports. This opens up possibilities like embedded interpreters and interactive services without the overhead of spawning subprocesses or dealing with C library bindings.
This page summarizes “SwiftNIO SSH Implementation” by Swift.org Blog, published Nov 19, 2020. All credit for the original work goes to the authors.
