## Summary
Adds support for overriding special WebSocket headers (`Host`,
`Sec-WebSocket-Key`, and `Sec-WebSocket-Protocol`) via the headers
option when creating a WebSocket connection.
## Changes
- Modified `WebSocketUpgradeClient.zig` to check for and use
user-provided special headers
- Added header value validation to prevent CRLF injection attacks
- Updated the NonUTF8Headers struct to automatically filter duplicate
headers
- When a custom `Sec-WebSocket-Protocol` header is provided, it properly
updates the subprotocols list for validation
## Implementation Details
The implementation adds minimal code by:
1. Using the existing `NonUTF8Headers` struct's methods to find valid
header overrides
2. Automatically filtering out WebSocket-specific headers in the format
method to prevent duplication
3. Maintaining a single, clean code path in `buildRequestBody()`
## Testing
Added comprehensive tests in `websocket-custom-headers.test.ts` that
verify:
- Custom Host header support
- Custom Sec-WebSocket-Key header support
- Custom Sec-WebSocket-Protocol header support
- Header override behavior when both protocols array and header are
provided
- CRLF injection prevention
- Protection of system headers (Connection, Upgrade, etc.)
- Support for additional custom headers
All existing WebSocket tests continue to pass, ensuring backward
compatibility.
## Security
The implementation includes validation to:
- Reject header values with control characters (preventing CRLF
injection)
- Prevent users from overriding critical system headers like Connection
and Upgrade
- Validate header values according to RFC 7230 specifications
## Use Cases
This feature enables:
- Testing WebSocket servers with specific header requirements
- Connecting through proxies that require custom Host headers
- Implementing custom WebSocket subprotocol negotiation
- Debugging WebSocket connections with specific keys
Fixes #[issue_number]
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
