Commit Graph
2 Commits
Author SHA1 Message Date
jaap-jan d459dac600 Stop a dead WebView2 hanging Connect with the busy flag stuck
VaultViewModel.ConnectAsync awaited TerminalWorkspace.WaitForRendererAsync
with no timeout and no token, and RunAsync clears IsBusy only after the
work returns. Whether the renderer attaches at all depends on a runtime
this application does not install: with a missing or policy-blocked
Evergreen runtime, or an AppContainer that cannot reach loopback, the
socket never arrives — so Connect never returned, the window stayed
disabled on "Connecting…" for the rest of the session, and nothing on
screen said why. Left out of 0500e43 to keep that change focused, and
recorded in docs/platform-flags.md as worth fixing on its own merits.

The gate itself is unchanged and has to stay: TerminalDataPlane.SendAsync
drops frames when no renderer is attached rather than queueing them, so a
session opened before the renderer arrives loses its SessionOpened frame
and then streams output at a terminal that was never created. Only the
wait changed — RendererAttached.WaitAsync(timeout, cancellationToken),
with the command's own token threaded through.

Fifteen seconds, on TerminalWorkspaceOptions.RendererTimeout. Attaching is
normally near-instant, since WebView2 starts with the window and the page
has usually attached while the passphrase was still being typed, but a
first run on a cold profile creates a user-data directory and starts a
process tree of some thirty-five processes first, which on a loaded
machine is seconds rather than milliseconds. A renderer that will never
attach will not attach however long the wait is, so being generous costs
only how long a broken runtime takes to say so, while being tight costs
telling someone their runtime is broken when it was merely slow.
Injectable because both new tests would otherwise sit out that budget.

The timeout is caught in VaultViewModel rather than left to RunAsync's
generic handler, because TimeoutException.Message is "The operation has
timed out" — which sends someone looking at their network or their host.
The status now names the WebView2 runtime and says to install it.

TerminalWorkspaceTests covers the half that was missing: the wait gives up
(329 ms against a 250 ms budget) and obeys its token (2 ms against a
five-minute one). Before the bound, the first of those would have hung
rather than failed. ShellFlowTests never starts its workspace, which from
the view model's side is indistinguishable from a WebView2 that failed to
initialise, so it asserts that the status names WebView2 and that IsBusy
is cleared; changing the catch to another exception type makes it fail
with "The operation has timed out.", so neither assertion is vacuous. The
success path is untouched and still covered end to end by
TerminalEndToEndTests against a real sshd container, which now passes the
test's cancellation token.

One byproduct: the doc comment on WaitForRendererAsync carried two
double-encoded em dashes, fixed now that the block is rewritten.
2026-07-29 15:26:53 +02:00
jaap-jan 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.
2026-07-28 21:58:55 +02:00