DodoSSH/docs/adr/0013-desktop-distribution-and-updates.md

ADR 0013 — Distributing the desktop client, and letting it replace itself

• Status: accepted
• Date: 2026-08-04
• Builds on: ADR 0001, ADR 0011
• Settles: the desktop half of M4 packaging, which ADR 0011 left open

Context

ADR 0011 settled the phone and said explicitly what it was not settling: "M4's desktop packaging inherits rule 2 and not the rest." This is that inheritance, plus the thing the phone deliberately does not have.

The desktop head was not packaged at all. There were no tags, no Version property anywhere in the repository, and therefore no version: every assembly reported the SDK's default 1.0.0, and the API had been serving that string to every client that asked it for serverVersion. There was no installer and no way for anybody holding a copy to learn that a newer one existed.

That is tolerable while nobody has it. It stops being tolerable at the first release, and it stops in a particular direction: this client holds the plaintext of a team's infrastructure credentials, by construction (ADR 0001). For software like that, "the fix shipped and the user never got it" is a security outcome. ADR 0011 named the cost of shipping outside a store — "no discovery, no automatic update" — and accepted it for Android because the platform left no better option. The desktop leaves a better option, and this ADR takes it.

The new thing an updater introduces is a capability that did not exist before: something that can replace the binary on a user's machine, without the user choosing each build. ADR 0001 models the party who wants the secrets as attacking the client rather than the crypto, and ADR 0011 turns that into a question of custody — which parties can ship one person a build? An updater is a second answer to that question, so it needs the same treatment as the signing key, and it is easy to get wrong because the dangerous part does not look like a key.

Decision

1. Velopack, per-user, under %LOCALAPPDATA%, with no administrator prompt

docs/platform-flags.md had already ruled out the platform-native option, and it is worth restating because it is the kind of decision that gets reopened: MSIX is not deprioritised, it is impossible here. A packaged application runs WebView2 in an AppContainer where loopback connections are blocked without a CheckNetIsolation exemption, and the terminal data plane is a loopback WebSocket. MSIX would not degrade the product, it would remove the terminal.

Velopack's path was checked against that and reintroduces nothing: Setup.exe is an ordinary Win32 executable that unpacks a directory and creates shortcuts, there is no package manifest and no package identity, and the process therefore stays an ordinary desktop process. Manual check 16.4 is what would notice if that ever changed, because it connects a real shell from the installed build.

2. The pack id is DodoSSH.Desktop, and it is irreversible

Velopack installs to %LOCALAPPDATA%\<packId> and removes that entire directory on uninstall. ClientPaths.DataDirectory is %LOCALAPPDATA%\DodoSSH, and it holds cache.db with its -wal and -shm companions, settings.json, and device.key.

So the obvious pack id would have installed the application on top of the user's encrypted cache, and uninstalling would have deleted the device key and the outbox — the changes this machine has made and not yet pushed, which MainWindowViewModel.SignOutWarning already describes to users as existing "nowhere else in the world". The application refuses to delete that without a counted confirmation; an uninstaller would have done it silently.

Velopack's own guidance is to keep persistent files in roaming %APPDATA%. That guidance is declined, and ClientPaths already explains why: two machines writing one SQLite file through a file-sync client corrupts it, and the outbox is per-machine by design. The install moves; the profile does not.

Like the Android package id, this is a one-way door — it is the identity an installed client matches an update against, so changing it later orphans every existing install: still running, never updated, and invisible to the new one.

3. The release is cut by a person, and the forge token never goes near CI

This is the paragraph that will be argued with, so it is the one written most carefully.

The tempting argument is that a Gitea write token is not a signing key, and so — unlike the Android keystore ADR 0011 rule 1 keeps off runners — it could live in a CI secret and let a tag cut a release.

It does not survive contact with what the token can do. Velopack clients fetch from the configured source over TLS and do not verify a package signature when they apply it. So anyone who can write a release on this repository can publish an update that every installed client downloads and runs. That is precisely the capability ADR 0011 rule 1 places on a machine which is not a runner, reached through a different door — and a workflow secret is held by everyone who can change a workflow file, which for a repository with any contributors is a wider set than it looks.

So: scripts/release-windows.ps1, run by a person on a Windows machine, in two phases. Phase one builds and packs and stops. Phase two, a separate invocation, asks for the token and uploads. The split exists so that what reaches users has been installed and started by a human first, and so that the credential is in memory only for the minutes that need it.

There is a second, smaller reason the release could not be a CI job here anyway: vpk stamps and embeds the Setup.exe and Update.exe stubs with Windows tooling, and every job in ci.yml is runs-on: [linux]. Both reasons are recorded because somebody will fix one and believe they are done.

What CI does gain is the same thing the android job already does — it proves the artefact still builds. A win-x64 publish runs on main and on tags, so a restore graph that resolves for net10.0 and not for net10.0/win-x64 fails there rather than under a person midway through a release.

4. The update check points at the project's forge, and the address is a constant

ADR 0011 rule 2 carries over unchanged, and its update clause carries with it: "If an update check is ever added it points at the project's domain." Here that is git.dodotech.cloud, and it is a const in VelopackUpdateChannel rather than a setting.

The constant is the mechanism, not a convention. A configurable feed address is exactly the knob that would let an operator — or an edit to a plaintext settings.json — point the update path at the deployment, and an operator who can answer "is there a newer version" can answer "no" forever, pinning a chosen user to a build with a known hole while holding no key at all. Making it unsettable is that rule expressed in a way nobody has to remember.

ClientSettings therefore stores whether to check, and nothing else: no address, no channel, no token. A private release repository is incompatible with this design and that is worth knowing rather than discovering, because the token would have to be readable before the vault is unlocked, and this file is the one place that can be read then — which is the one place a token may not go.

◆ It was discovered. The paragraph above was written and the repository was private anyway, so every check on every client asked an address that answers 404 — Gitea does not distinguish "not there" from "not yours" — and both heads reported the running build as current. It had never once worked, on either platform, and nothing anywhere said so. Two things came out of that and both are now written down rather than assumed:

• The feed repository must be readable with no credentials, and that is a deployment precondition rather than a property of the code. It is checkable in one line, which is the only reason it is worth stating: curl -so /dev/null -w '%{http_code}' https://git.dodotech.cloud/api/v1/repos/DodoTech/DodoSSH answers 200 when the design holds and 404 when it does not. /api/v1/version answering 200 proves only that the forge is reachable, which is what made this look like nothing was wrong.
• An unreachable channel must be distinguishable from a current build. IUpdateChannel.CheckAsync used to document null as the honest answer for both, on the reasoning that the caller does the same thing either way. That is true of the six-hourly pass and false of CHECK NOW, and it is what turned a total outage into a reassuring sentence. It throws now, and UpdateViewModel keeps the distinction it always had: silent on the timer, the exception's own message on the button.

5. MinClientVersion stays unread, and if it is ever read it may not fetch

MetaResponse.MinClientVersion has existed since M1, is served, is fetched on every sign-in, and is read by nothing. Hanging the updater off it would have been natural and would have been wrong — and note the shape of the error, because it is not "inherits an existing risk". Today the field controls nothing at all. The moment an update check is conditioned on it, rule 2's sentence applies verbatim and the risk is created.

The split to preserve:

• A deployment may say "I will not serve a client this old" and draw a remediation screen. That is the deployment describing itself, which is legitimate and is what the field's own documentation asks for. That screen may carry a sentence and a link to the project's release page.
• It may not carry a button that triggers a check or a download. A link is the user going somewhere; a fetch is the operator's answer steering this process.

Under the design as built, an operator withholding or deflating the value achieves nothing — the check runs on its own timer and never consults the deployment. Inflating it denies service to their own users, which they can already do by turning the server off.

6. Self-contained, and not single-file

Self-contained because .NET 10 is recent enough that almost no machine has the runtime, and because the usual objection — that runtime security patches then require an application update — is answered by the feature this ADR is about. Velopack's deltas are per-file and the runtime files do not change between our releases, so the runtime costs almost nothing per update; it is paid on first install.

Not single-file, for four independent reasons: platform-flags.md records that libsodium ships native binaries per RID and complicates single-file publishing, and libe_sqlite3, libSkiaSharp and libHarfBuzzSharp do the same; a bundle changes wholly on every build, so deltas stop working; Velopack is a directory-based updater by design; and a self-extracting bundle puts the executable under a temp path deep enough to hit the WebView2 long-path failure that same document records. Not trimmed — EF Core is not trim-safe and TreatWarningsAsErrors turns every IL2xxx into a build break, so trimming is a project rather than a flag.

Native symbol files are excluded and ours are kept, which is worth recording as a decision because the numbers are so lopsided: libSkiaSharp.pdb and libHarfBuzzSharp.pdb are 100 MB of debug symbols for third-party native code nobody here will step through, and all fifteen of our own managed PDBs together are 0.93 MB. Dropping the two took a publish from 227 MB to 127 MB. Keeping ours means an Exception.ToString() carries file names and line numbers, which for a self-hosted product is the whole diagnostic channel — the way a fault gets reported is a user pasting a stack into an issue.

7. One version, derived from the tag

MinVer, with MinVerTagPrefix of v, matching the tags CI already triggers on. The tag was already the version of record for the API's container image; this makes it the version of record for everything, including the client's own AssemblyInformationalVersion, which is what the preferences screen prints and what Velopack compares.

MinVer's one sharp edge is that it answers plausibly rather than failing: a shallow clone with no tags yields 0.0.0-alpha.0.N. Here a wrong version is a client that never updates, so it is guarded twice — fetch-depth: 0 on every checkout, and a step that fails a tag build when the computed version and the tag disagree.

The Windows application manifest's assemblyIdentity version is deliberately left at 1.0.0.0. It is a side-by-side activation field this application does not use and nothing reads; what a person sees comes from the PE version resource, which MSBuild fills from FileVersion.

8. Unsigned for now, with a named trigger

Every installer will raise SmartScreen's "Windows protected your PC" until reputation accrues. The cost is smaller and more precisely bounded than the reflex suggests, and the bound is worth knowing: Mark-of-the-Web is applied by the browser that downloads Setup.exe, so the warning lands at first install only. In-app updates are fetched by the application's own HTTP client and applied by Update.exe from a local file, and never trip it. One dialog per user per lifetime, not one per update.

The trigger for buying an OV certificate on a hardware token is the first release the README invites a stranger to install. ADR 0011 already describes Authenticode as the easy custody case — the key stays with the developer — and the post-2023 requirement that it live on FIPS 140-2 Level 2 hardware enforces "offline, never in CI" physically rather than by policy. --signParams is the single line in the release script that changes.

Azure Trusted Signing is not the quiet default and needs its own ADR. It is cheaper and has no hardware token, and it puts a compellable third party in the signing path — which is ADR 0011 rule 3's shape one layer down, declined there for reasons that do not stop applying because the vendor changed.

Consequences

The desktop gets what ADR 0011 had to refuse the phone. Discovery is still manual — somebody has to be told where the release page is — but from the first install onward the client keeps itself current without anybody deciding to go and look. That is the sharpest edge of the Android decision, blunted on the platform where it could be.

Nothing is ever installed while the application is running. A fetched update waits for a restart the user presses, or for the next launch they were going to do anyway. This is not caution for its own sake: this application deliberately keeps shells running across a lock, and argues in LockAsync that a lock which destroyed work would simply stop being used. A restart does end every shell, so it is a decision that belongs to the person whose job is running in one — and the interface says so, in the same words the close button already uses.

The release is a manual step, and that will feel slow. It is roughly ten minutes of a person's attention per release, and the convenience being refused is the entire point of CI. Where the two collide the custody argument wins, exactly as it does for the Android keystore.

The forge grows by about 125 MB per release, forever. Measured on the first real pack rather than estimated: a 127 MB publish directory compresses to a 60 MB full .nupkg and a 64 MB Setup.exe, and both are uploaded. Velopack needs the previous full package present to build a delta against, so pruning old releases has a real cost — a client several versions behind falls back to a full download. A 64 MB asset is also large enough to meet whatever body-size limit fronts git.dodotech.cloud (nginx's client_max_body_size defaults to 1 MB), which is worth checking before the first upload rather than discovering after ten minutes of transfer.

Uninstalling leaves the vault cache behind, on purpose. %LOCALAPPDATA%\DodoSSH survives, so a reinstall finds an enrolled machine and asks for the passphrase — which is what somebody reinstalling wants. The honest cost is that device.key is left too, and the account goes on listing a device that is no longer installed. That is a wart rather than a hole: the blob is decryptable only by this machine's TPM, and Sign Out is the button that withdraws the registration. An uninstall is not a sign-out and must not pretend to be one.

Contracts and client now share a version number. DodoSSH.Contracts is packable, so a contracts-only change ships as a client version bump. One number is the point; this is the price of it.

The Android head's versionName now follows the same tag, while its integer versionCode stays hand-bumped, because Android needs a monotonic integer and SemVer does not provide one. Nothing else about ADR 0011 changes.

Rejected

• MSIX. Not a preference. It would break the terminal outright; see decision 1.
• A CI job that cuts the release on a tag. The convenience is the point of CI and the custody is the point of ADR 0011; where they collide the custody wins. See decision 3, and note that a Windows runner answers the mechanical objection while leaving the real one untouched.
• A configurable update feed. Named here because it is the change somebody will propose in good faith, for a self-hosted product where making things configurable is usually right. It is the one setting that would hand the operator the capability the whole trust model is about.
• The deployment serving the installer. Refused again, for the third ADR running, because it is genuinely the nicest onboarding available and will be proposed again.
• Conditioning updates on MinClientVersion. See decision 5. It would create the attack rather than inherit it.
• Azure Trusted Signing, for now, on custody grounds rather than on mechanics. See decision 8.
• A hand-edited version property. Considered seriously against MinVer, and it loses on the thing that matters here: the tag is already the version of record for the container image, and two places to write one number is a pair that can disagree. MinVer's silent-wrong-answer failure mode is real and is what the two CI guards in decision 7 exist for.