jaap-jan 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.
2026-07-28 22:30:42 +02:00

DodoSSH

A self-hosted, team-oriented SSH client with an end-to-end encrypted vault.

Manage hosts, credentials and keys in a desktop app; sync them across your devices and share them with teammates through a server you run yourself. The server stores ciphertext and never holds a key — the operator cannot read the credentials it stores.

Status: early development. See the milestone plan for what exists today.

Why

Teams either scatter SSH credentials across individual ~/.ssh directories with no sharing story, or pay per-seat for a hosted product that holds their infrastructure credentials. DodoSSH keeps the convenience of a synced, shareable vault while remaining self-hostable and zero-knowledge.

Architecture

Component Choice
Backend ASP.NET Core on .NET 10, PostgreSQL + EF Core
Client Avalonia (C#) for Windows/Linux/macOS; terminal pane is a WebView running xterm.js
Auth OIDC, provider-agnostic (Entra ID, Keycloak, Auth0, Authentik)
Vault End-to-end encrypted; X25519 + Ed25519 + XChaCha20-Poly1305, Argon2id unlock
Connections Client-direct SSH by default, with an optional raw-TCP server relay

Two consequences worth knowing before you read further:

  • Revocation is not retroactive. A removed member keeps what they already downloaded. The real remediation is rotating the SSH credential, so offboarding is built around a rotation checklist rather than a button that implies more than it delivers.
  • No session recording in relay mode. The relay forwards SSH ciphertext, so it cannot see commands. That is the cost of the relay not being able to read your traffic.

The reasoning behind each major decision is recorded in docs/adr/, starting with the E2EE trust model.

Repository layout

src/
  DodoSSH.Contracts        DTOs shared with the client — the real API contract
  DodoSSH.Crypto           DSH1 envelope, AAD derivation, the key hierarchy
  DodoSSH.Domain           entities and invariants, no EF
  DodoSSH.Infrastructure   DbContext, configurations, migrations
  DodoSSH.Api              the server
  DodoSSH.Client.Auth      OIDC code+PKCE on a loopback redirect, and the key binding
  DodoSSH.Client.Ssh       connections, PTY shells, host key trust
  DodoSSH.Client.Terminal  the loopback data plane and credit-based flow control
  DodoSSH.Client.App       Avalonia; the only project that knows about a UI toolkit
tests/                     one test project per source project
docs/adr/                  architecture decision records

Everything under src/DodoSSH.Client.* except App is deliberately free of Avalonia. That is the seam that lets the SSH layer, the terminal's flow control and the OIDC flow be tested without a UI toolkit or a browser engine — which is most of why they are testable at all.

Building

Requires the .NET SDK pinned in global.json (10.0.x).

dotnet build DodoSSH.slnx
dotnet test DodoSSH.slnx

Run the API locally:

dotnet run --project src/DodoSSH.Api

It listens on http://localhost:5233, serving /healthz/live, /healthz/ready and — in Development — /openapi/v1.json.

Development and testing are currently Windows-only. Anything known or suspected to differ on Linux and macOS is tracked in docs/platform-flags.md, along with the deployment gotchas that have already cost time once. Read it before assuming something works off-Windows.

Conventions the build enforces

  • Warnings are errors. dotnet format --verify-no-changes gates CI.
  • Package versions are centralised in Directory.Packages.props; packages.lock.json is committed and CI restores in locked mode.
  • BannedSymbols.txt bans DateTime.UtcNow (use TimeProvider), Guid.NewGuid (use CreateVersion7), sync-over-async, MD5/SHA1 and PBKDF2.
  • Public members of DodoSSH.Contracts must be declared in PublicAPI.Unshipped.txt, so a contract change is a build error rather than a client-side surprise.

Milestones

  • M0 — foundation. Repo structure, build conventions, CI, ADRs. Done.
  • M1 — vertical slice. OIDC login → enroll → create a host → open a shell. Server done: the DSH1 crypto core, the data model, sync push/pull for hosts, /me, and enrollment with the identity-provider key binding. Client done: the key hierarchy, the OIDC flow with the key binding, SSH connections with host key trust, the terminal data plane, and an Avalonia shell whose terminal works end to end against a real sshd. Remaining: the encrypted local cache and the sync client, which are what let the app read hosts from the vault instead of a form. The client currently connects to a host you type in.
  • M2 — full personal vault, robust sync, relay.
  • M3 — teams, sharing, ACLs.
  • M4 — hardening and ops, packaging, self-hosting guide.
  • M5 — multi-provider OIDC, key rotation, per-item content keys.

Licence

MIT.

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