5fccd5382447da62d66173c51a70b5faab3332cb
2
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 jaap-jan
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5fccd53824 |
Add the Avalonia app and the xterm renderer, and fix two real bugs
The terminal works end to end. A new integration test drives a real sshd in a container through a real PTY, the real pump, the real loopback WebSocket with its token and origin checks, and a ClientWebSocket standing in for the page: the login banner arrives, typed input round-trips, and `stty size` reports the 100x30 the session asked for. The only untested link left is xterm drawing bytes it was handed. The WebView is de-risked on Windows, which was the plan's largest risk. Not by assertion: with the app running there is an established TCP connection from msedgewebview2 to the data plane port, so WebView2 launched, navigated to the loopback page, executed terminal.js, and completed the WebSocket handshake against the real token and origin checks. Linux remains unproven and the package's own release notes now corroborate the concern -- Linux uses a WPE backend, and it ships a NativeWebDialog described as useful where embedded WebViews may be unavailable. Two bugs found by building it, both of which would have shipped: - ShellStream.Write buffers and needs an explicit Flush. Without one a keystroke is accepted, reported as written, and never reaches the remote: the terminal displays output perfectly and simply stops responding to input. SSH.NET's own WriteLine flushes, which is why the earlier spike never hit it. Found by isolating the pump against real SSH and reading BytesRead=51 -- banner and prompt through, nothing after. - The Windows app manifest needs a supportedOS list, or Avalonia's native control host fails outright and the terminal never starts. Also fixed a genuinely flaky test I happened to catch: SyncCursorTests tampered with the *last* base64url character, whose low bits the decoder ignores when the input length is not a multiple of three -- so a tampered cursor sometimes decoded to identical bytes and verified. It failed roughly one run in thirty, depending on a random key. Now tampers the penultimate character, which is fully significant at every length; 40 consecutive runs are clean. xterm 6.0.0 plus the fit and webgl addons are vendored as UMD bundles rather than built with npm, so a clean clone needs only the .NET SDK. Provenance and licences are recorded next to them, along with the UMD global names terminal.js depends on -- a bundle that switched to ES modules would load without error and leave Terminal undefined. The renderer acknowledges output from term.write's completion callback, not on receipt. Acknowledging early would return flow-control credit for bytes the screen has not caught up with, which is the one thing the credit window exists to measure. TerminalWorkspace moved into DodoSSH.Client.Terminal: it has no Avalonia dependency, and having it there is what let the end-to-end test exist at all. 404 tests pass, zero warnings on a clean rebuild, format clean. |
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jaap-jan
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eb354bcdd9 |
Add the SSH session layer and the terminal data plane
The throughput harness the plan requires before any UI, plus the SSH plumbing under it. 94 new tests, no WebView involved. Credit-based flow control is what makes `yes` survivable. A terminal renders at 60 Hz at best while a remote produces output as fast as the network allows, and the difference has to accumulate somewhere or be refused. Credit is reserved *before* reading, never after: because the pump cannot read more than the renderer has room for, the coalescing buffer is bounded by the window rather than by how fast the remote can talk. When credit runs out the pump stops reading, SSH's own receive window closes, and the remote sshd blocks -- backpressure to the source with no custom protocol. Verified by falsification, not just by passing: with the credit gate removed three tests fail, including the throughput harness's bounded-memory assertion. Acknowledgements are clamped because they cross into JavaScript, where a buggy or hostile page could otherwise claim to have rendered a gigabyte and talk the host into an unbounded read. Host key trust is enforced by *failing* the connection rather than prompting inside the handshake. SSH.NET raises verification synchronously, so consulting the user there would block the handshake on a UI round trip and deadlock the first time the prompt needed the UI thread. Unknown host and changed key become distinct exceptions the caller resolves asynchronously. A mismatch has no retry path at all: a dialog offering to continue is how users are trained to click through the one warning that actually indicates interception. A legitimately rebuilt server is handled by removing the pin in settings, away from the moment of connecting. The data plane serves the renderer page from the same loopback listener as the socket, which makes Origin predictable -- always http://127.0.0.1:{port} -- where a WebView virtual-host mapping would give a different origin per backend and nothing to validate. The token is substituted at serve time, so it never touches disk and never appears in a URL. Being clear about what that buys: not protection from a process running as this user, which can read our memory anyway, but from a page in the user's browser attempting WebSocket connections to loopback ports, which is a real and routine thing. Two bugs the tests caught. The accept loop handled connections serially, so an upgraded WebSocket parked it inside the receive loop and every later request went unanswered -- the page's own script among them. The suite hung rather than failed, which is how I found it. And SHA-1 is unavoidable here: RFC 6455 mandates it for Sec-WebSocket-Accept, where it authenticates nothing. Suppressed narrowly with that reasoning; the alternative, HttpListener.AcceptWebSocketAsync, throws PlatformNotSupportedException off Windows. |