Public Access
jaap-jan
5fccd53824
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.
148 lines
9.7 KiB
Markdown
148 lines
9.7 KiB
Markdown
# Platform flags
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Things known or suspected to behave differently outside Windows, plus deployment gotchas that
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have already cost time once. **Development and testing are currently Windows-only**, so anything
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here marked *unverified* has not run on the platform in question and must not be assumed to work.
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Each entry says what the risk is, why it matters, and what to do about it. Delete an entry when it
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has been verified or made moot — not when it merely stops being convenient.
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## Cryptography
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**`ChaCha20Poly1305.IsSupported` is false on macOS**, and on Windows builds before 10.0.20142.
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This is why the client uses NSec (libsodium) rather than the BCL for content encryption; see
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docs/crypto.md §1. *Already mitigated* — but if a BCL AEAD path is ever added as a fallback it
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**must** gate on `IsSupported` rather than assuming availability, or the client will fail to open
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any vault on macOS.
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**Argon2id timings are measured on one Windows machine only.** 256 MiB with t=4 took 323 ms here.
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The floor and ceiling in `EnrollmentLimits` were chosen against that number. *Unverified
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elsewhere:* recalibrate on the slowest target platform before recommending a default profile,
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because a cost that is comfortable on a desktop can make unlock unusable on a low-power laptop —
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and the parameters are stored per user at enrollment, so a bad default is a per-user migration.
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**libsodium ships native binaries per RID.** This complicates single-file and AOT publishing, and
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on macOS every native library (`libsodium`, `libSkiaSharp`, `libHarfBuzzSharp`, `libe_sqlite3`)
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must be signed **individually** with `--options runtime --timestamp` before the bundle is signed,
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or notarization fails with an error that does not name the offending file.
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## Desktop client
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**The WebView works on Windows.** `Avalonia.Controls.WebView` 12.0.1 (MIT, no licence key) hosts the
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terminal page successfully: WebView2 launches, navigates to the loopback page, runs its JavaScript and
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completes the WebSocket handshake. Verified by observing an established TCP connection from
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`msedgewebview2` to the data plane port.
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**The Windows app manifest must declare a `supportedOS` list.** Without it the process reports a
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downlevel Windows version and Avalonia's native control host fails outright — *"Unable to create child
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window for native control host"* — so the WebView, and therefore the terminal, does not start at all.
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`[STAThread]` on `Main` is equally mandatory: WebView2 checks the apartment state and refuses to
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initialise on an MTA thread.
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**WebView2 spawns a process tree, not a process.** Around 35 processes were observed for one embedded
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view. That is the concrete reason the design uses one WebView hosting N terminals rather than one per
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tab: twenty tabs would mean twenty of those trees.
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**The Avalonia WebView on Linux remains unproven, and is still the largest risk in the plan.** The
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package's own release notes say `NativeWebView` gained Linux support via a **WPE** backend
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(`libwpewebkit-2.0`), which is much less widely installed than WebKitGTK — and it ships a separate
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`NativeWebDialog` described as *"particularly useful for platforms like Linux where embedded WebView
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controls might not be available"*, which is the vendor confirming the concern. *Unverified:* a spike
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must cover Ubuntu on both Wayland and X11, Fedora KDE, and macOS 15. This is why the terminal sits
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behind `ITerminalHost`; that seam should not be collapsed away for convenience.
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**`Avalonia.Diagnostics` has no 12.x release** (latest is 11.3.18), so the developer tools overlay is
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unavailable on Avalonia 12. Development-only, so nothing ships differently — but debugging a layout
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problem currently means reasoning rather than inspecting.
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**The xterm bundles are vendored, not built.** `@xterm/xterm` 6.0.0 with the fit and webgl addons, all
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MIT, committed as UMD bundles under `WebAssets/vendor` and embedded as Avalonia resources. No npm or
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esbuild step, so a clean clone builds with the .NET SDK alone. The cost is that upgrades are a manual
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re-download; the licence and versions are recorded here so that stays visible.
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**SSH.NET's `window-change` is verified working** as of 2025.1.0 — resolved, not a flag.
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`ShellStream.ChangeWindowSize(columns, rows, width, height)` exists and the remote genuinely
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observes it: `PtyAndResizeSpikeTests` reads `stty size` back from a real sshd after resizing, and
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repeated resizes each take effect. The `IChannelSession` fallback is not needed. That suite stays
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in place as a regression guard, because an upgrade that silently stopped sending the request would
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present as wrapped output only after a resize — easy to misattribute to the terminal emulator.
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**`ShellStream.Write` buffers and requires an explicit `Flush`.** Without one a keystroke is accepted,
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reported as written, and never reaches the remote — the terminal displays output perfectly and simply
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stops responding to input. SSH.NET's own `WriteLine` flushes, which is why a spike that used it never
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hit this. `SshNetShellSession.WriteAsync` now flushes per write; batching would be wrong anyway, since
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a terminal has to put a keystroke on the wire immediately.
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**`ShellStream` does not override `ReadAsync`.** The base `Stream` implementation therefore runs
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the blocking `Read` on a thread-pool thread, so every open session parks one thread for as long as
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it is idle. Fine for the handful of tabs M1 targets; revisit before advertising many concurrent
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sessions, since the fix is either an upstream change or driving `IChannelSession` directly.
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**SSH.NET cannot share one connection between `SshClient` and `SftpClient`.** A shell plus SFTP to
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the same host means two TCP connections, two authentications and — later — two relay sockets.
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Connect SFTP lazily and reuse the cached decrypted credential so the user is not prompted twice.
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**Agent forwarding is de-scoped from v1.** It needs an upstream SSH.NET change. A vault-backed
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agent of our own plus ProxyJump covers the real use cases.
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**The SSH suite pulls `linuxserver/openssh-server` from Docker Hub**, which is rate-limited for
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unauthenticated pulls. If CI starts failing on image pulls rather than on tests, that is why.
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**MSIX packaging is ruled out, not merely deprioritised.** A packaged app runs WebView2 in an
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AppContainer where loopback connections are blocked without a `CheckNetIsolation` exemption. The
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terminal data plane *is* a loopback WebSocket, so MSIX would break the product outright. Velopack
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for Windows/macOS/AppImage; Flatpak and deb/rpm defer updates to the package manager.
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**Linux ships AppImage and Flatpak first**, specifically so the WebKit runtime is bundled rather
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than assumed present on the user's machine.
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**Opening the system browser depends on the platform handler.** `SystemBrowserLauncher` uses
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`UseShellExecute`, which delegates to `ShellExecute` on Windows, `open` on macOS and `xdg-open` on
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Linux. *Unverified off Windows:* `xdg-open` comes from `xdg-utils`, which is not guaranteed on a
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minimal desktop or inside a Flatpak sandbox — where the portal is the correct route instead. If
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sign-in silently does nothing on Linux, this is the first thing to check. `IBrowserLauncher` exists
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so a platform-specific opener can be substituted without touching the flow.
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## Build and CI
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**Integration tests need a Docker daemon** (Testcontainers). They run on `ubuntu-latest` in CI.
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macOS runners have no Docker daemon, and the Windows CI job is deliberately build-only. So
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anything proved by an integration test is proved on Linux only — which is the right place for
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server code, and no coverage at all for client platform behaviour.
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**`[CallerFilePath]` is rewritten to `/_/...` under `ContinuousIntegrationBuild`.** Any test that
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locates a fixture by source path passes locally and fails in CI. Copy fixtures to the output
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directory and read them via `AppContext.BaseDirectory` instead; `GoldenVectorTests` shows the
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pattern.
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**`dotnet format --verify-no-changes` is part of the CI gate** and exits non-zero on style
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warnings, not just whitespace. Run it before pushing; a build with zero warnings can still fail
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that step.
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## Deployment
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**PostgreSQL 18 moved its data directory** to `/var/lib/postgresql`, not `/var/lib/postgresql/data`
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as in 17 and earlier. A compose file carried over from an older version silently gets an empty
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volume — the database appears to work and loses everything on restart. Relevant to any compose
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file other than `deploy/docker-compose.dev.yml`, which is already correct.
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**Keycloak in the dev stack listens on host port 18080, not 8080.** On this machine an unrelated
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Apache Tomcat holds `127.0.0.1:8080`, and a loopback-specific bind wins over Docker's `0.0.0.0`
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publish when resolving `localhost` — so every realm request returned 404 while the container
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looked healthy. If discovery fails against a locally-published container, check for another
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process bound specifically to loopback before suspecting the container.
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**`Sync:CursorSigningKey` generates an ephemeral per-process key when unset.** Fine for a single
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node; on a multi-node deployment cursors issued by one node are rejected by another, so clients
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resync from the beginning repeatedly. Must be configured explicitly before running more than one
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instance. `WarnOnRiskyConfiguration` logs this at startup.
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**Rate limiting is not implemented yet** (M2). `POST /api/v1/me/enrollment` and the sync endpoints
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are reachable by any authenticated caller at any rate. Enrollment requires a valid access token
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and is idempotent, so the exposure is resource consumption rather than a credential-guessing
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surface — but it is still an unmetered write path.
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**`/api/v1/me` does not update `last_seen_at_utc`.** Deliberate: a GET that writes on every call is
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a smell, and nothing depends on the value yet. Revisit when device management lands, since that is
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the first feature that needs it.
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