# 2026-07-17: join URLs + cert pinning (remote-issuance step 1)

Implemented step 1 of [/plans/remote-token-issuance.md](/plans/remote-token-issuance.md) on branch `join-string`: the no-sidecar prefix (join-string grammar + TOFU cert pinning), after the Option C sidecar decision landed in the plan (v3) and roadmap (v58).

## What shipped

- `client/joinurl` (new package): Build/Parse of `mark://host#token=...&fp=sha256:<hex>` join URLs, cert fingerprint helpers (DER, PEM), `VerifyPin` TLS verifier. Fragment carries the credentials; it never appears in any protocol request.
- `client/fetch`: `Options.Pins` (host to fingerprint map). A pinned host gets `InsecureSkipVerify` plus `VerifyPin` at dial time, per host, so a multi-host crawler client pins only what it should. Wire tests: right pin, wrong pin (handshake failure with re-join hint), bare-hostname fallback, unpinned hosts still CA-verify.
- `client/internal/tokens`: entry gains `pin` field (tokens.toml, additive), `SetPin`/`Pins`/`ResolvePin` (flag > `DEMARKUS_PIN` > stored).
- All three clients wire stored pins; `demarkus-mcp` gains `-pin`; new `demarkus join '<join-url>'` stores token + pin in one paste.
- `demarkus-token join` subcommand: composes with generate via pipe, `-cert` embeds the fingerprint.
- `install.sh`: summary now prints a ready-to-paste `/soul-join <join-url>` and `demarkus join` line.
- Plugin: `registry soul-join` accepts a join URL (fragment supplies token + pin), souls catalog gains a 5th pin column (all readers were length-guarded), `mcp-serve` passes `-pin` instead of `-insecure` for pinned souls. `commands/soul-join.md` updated; plugin 0.12.16 to 0.13.0.
- Docs: `docs/site/tools/index.md` join-URL section.

## Decisions and gotchas

- **Never pin Let's Encrypt certs**: leaves rotate on renewal (install.sh runs certbot twice daily) and would break every pinned client. install.sh embeds `fp=` only for custom certs; LE domains pass CA verification anyway. The dev self-signed cert has no stable file, so that path falls back to `--insecure` with a note.
- **Go url fragment gotcha**: `u.Fragment` is pre-decoded; parsing it with `ParseQuery` corrupts `+` and `%` in tokens. Use `u.EscapedFragment()`. Conversely `url.Values.Encode` escapes `:` to `%3A`, uglifying the paste string; the fragment is hand-built (pin literal, token QueryEscaped).
- Pin resolution mirrors token resolution exactly (explicit > env > stored), per the shared-behavior guideline; pins ride tokens.toml instead of a new file.
- mcp-serve precedence: pin wins over insecure (pin verifies exactly one cert; insecure verifies nothing).

## Verified live

Self-signed server on :6399: `demarkus-token generate | join -cert` produced the URL, `demarkus join` stored both credentials, publish + fetch ran with no `--insecure`, and a corrupted pin failed at the QUIC handshake with the actionable mismatch error. Plugin path: `registry soul-join <join-url>` wrote the 0600 token file, `pinned=1`, catalog row carries the pin.

Full `make test` + `bash pre-commit.sh` clean. Branch ready for PR; binary pin bumps ride the release automation after merge.


## Follow-up: self-signed to CA migration

Question surfaced the scenario: server moves from a pinned self-signed cert to a CA cert. Pinned clients hard-fail (strict pin, by design); recovery is re-joining with a pinless join URL. The plugin path already handled it (catalog row upsert clears the pin), but `demarkus join` only wrote a pin when the URL carried one, so a stale pin survived re-join and kept failing. Fixed in the same branch: re-join re-states the trust material, a token-bearing URL without `fp=` clears the stored pin (with a stderr notice when one existed). Verified live against the e2e server. Lesson: when a credential store is updated by re-stating, absence of a field must overwrite, not preserve; the two join paths (upsert-row vs set-field) diverged on exactly that.


## Cut: pinning removed, branch ships token-only

Fritz was uneasy about the direction; the complexity audit agreed with him. The join URL half is ~100 lines of formatting with zero trust semantics; the pinning half carried a third trust state, rotation coupling, a migration bug (caught pre-merge), mixed-version edges, and hand-rolled VerifyPeerCertificate. Every follow-up question in review prep was a pinning question. HPKP precedent (browsers added then removed pinning in 2018) and the narrow constituency (only domainless hosts; LE covers the rest) settled it.

Cut executed on the branch: joinurl is token-only (`mark://host#token=...`, unknown fragment keys still fail loudly so future keys cannot silently drop), fetch/tokens/CLI/TUI/MCP pin code removed, souls catalog back to 4 columns, `demarkus-token join` drops `-cert`, install.sh join line token-only with an `--insecure` note for self-signed, both plugin docs and site docs updated. Full test suite + pre-commit clean; token-only e2e re-verified live (CLI join, publish, plugin soul-join with fragment token).

Decision recorded in the plan (v4): pinning deferred; if verified joins for domainless hosts return, they ride the sidecar redeem handshake (fingerprint out of band in the redeem response), not user-visible trust state. Plan sequencing also revised: sidecar redeem-only demoted; authenticated create is the sidecar MVP.

Lesson: when a feature generates a stream of "what happens when..." questions before it ships, that is the complexity bill arriving early; the severable half that causes them is the half to cut.


## PR #261 review round (CodeRabbit)

Eight findings fixed, two declined:

- Fixed: joinurl.Parse rejects URL state Join cannot represent (userinfo, query, duplicate token keys) and bracketed IPv6 literals (downstream slug derivation and default-port append would misparse them); Build rejects `@` and `[` in hosts. Negative tests for all, plus a SoulJoin regression for bracketed IPv6.
- Fixed: install.sh no longer swallows demarkus-token join failures with `2>/dev/null || true`; a failure warns with the manual command.
- Fixed: RemoteSoulRow returns an error for a catalog row with no host instead of ok=true (mcp-serve would have launched with an empty -host); mcp-serve surfaces catalog I/O errors separately from "not in the catalog".
- Fixed: demarkus-token join bounds stdin with a LimitReader (4KB) so piping a wrong file cannot become a "token".
- Fixed: joinurl package comment tightened to 3 lines; new test's MkdirAll error handled.
- Fixed: pi-memory soul-join doc no longer shows a token-bearing join URL as slash-command input (contradicted pi's own token-in-transcript rule); credentialed joins go in the user-run terminal command.
- Declined: checking fmt.Fprintf errors on stderr usage output; every existing subcommand's usage block uses the same unchecked idiom and each is followed by os.Exit(1).
- Declined: repo-wide IPv6 support in fetch.ParseMarkURL / TLS SNI; pre-existing behavior shared by every caller, not introduced by this PR. The join paths now fail loudly on IPv6 literals so nothing broken can be stored; full IPv6 support filed as follow-up.


## PR #261 review round 2 (outside-diff + late inline)

Two fixed, one declined:

- Fixed: port-only authorities rejected in joinurl (Build refuses a leading-colon host, Parse requires a non-empty hostname); regression cases both paths.
- Fixed: SoulJoin now routes every non-HTTPS host through joinurl.Parse, not only fragment-bearing ones, so malformed legacy inputs (paths, userinfo, query, IPv6 literals) fail loudly instead of half-parsing into a broken catalog row. Behavior change accepted deliberately: inputs like mark://host/path previously "succeeded" by storing a corrupt host. Regression cases added.
- Declined: unifying server/tools version resolution in install.sh into one pinned manifest. Independent per-component latest-release resolution is the installer's pre-existing pattern for every component; the skew window for the join subcommand is the gap between merging and the tools release publishing, and the failure mode after round 1's fix is a visible warning with the manual command. A single release manifest is a real installer improvement but a separate effort, not this PR.


## PR #261 review round 3

One finding, fixed: joinurl gains a shared validateHostPort rule (non-empty hostname, port numeric 1-65535, max 5 digits) enforced by both Build and Parse. Previously Build emitted h:bad and h:65536, and Parse accepted numeric out-of-range ports (Go's net/url validates digits only, not range). Subsumes the round-2 port-only-authority check. Negative tests: h:bad, h:65536, h:0, port-only, both paths.


## PR #261 review round 4

One finding, fixed: validateHostPort's hostname check flipped from a rune blocklist (which kept missing cases: spaces, stray brackets) to a DNS-charset allowlist ([a-zA-Z0-9._-]). Subsumes the previous ContainsAny("/#?@[") check entirely; one rule now covers every malformed-host class from rounds 1-4. Tests: "h x" and "h]x" rejected. Lesson: for input validation on a credential-bearing string, start with an allowlist; every blocklist round-trip with a reviewer is a missed-rune bug you shipped.


## Merged

PR #261 merged to main 2026-07-17 as commit 4c5f90d (squash) after four CodeRabbit rounds. Local branch deleted; main pulled. Plan doc updated to v5 (sequencing step 1 DONE with merge refs). The release chain takes it from here: client/tools releases, then the automated pin-bump PR repoints the plugins at binaries that carry the join subcommand and join-URL SoulJoin (until that lands, a new install.sh with an old tools release warns and falls back to the manual command). Next up per the plan: the sidecar, redeem + authenticated create together.


## Parity decision: the sidecar is the broker in single-host mode

Fritz set a parity goal: personal, team, and non-k8s deployments get the same library + broker experience as the k8s universe, including invites. Analysis showed the broker's only real k8s bindings are the Secrets writer (becomes a tokens.toml writer; the server already file-watch reloads) and packaging (becomes systemd/compose); OIDC works fine off-cluster via a Google/GitHub OAuth app, and the library only knows a broker URL. Consequence: no new sidecar binary; the remote-token-issuance plan (v6) now sequences broker single-host mode first (k8s audit, file backend, packaging), then invites in the broker minting core for both backends. The one open design question is identity for the zero-external-dependency personal tier; leaning capability-token front door before any built-in IdP. Convergence moved from the last step to the first.


## Broker k8s audit done

Findings appended to /plans/remote-token-issuance.md (v7). Headline: single-host mode is one storage interface (~5 files + main.go wiring); every Secret mutation already funnels through a single mutateSecret function. Three surprises: the broker has no SIGHUP at all (the documented "SIGHUP on revocation" never existed; k8s reload is Secret-mount projection, and on a VPS the server's own tokens-file watcher covers it, faster); write-token revocation is unimplemented (real new work for the membership step); and Provision runs on the read path, so the backend is hit by first read. Roadmap's Phase 6.3 description needs the SIGHUP claim corrected when next touched.


## Broker storage interface (branch storage-interface)

Step 2 part 1 of the remote-token-issuance plan implemented: the broker's k8s surface is now behind a SecretStore interface.

- New `internal/broker/storage.go`: SecretRef (k8s tuple + file path, resolved by Config helpers so every call site locates credentials one way), SecretStore interface, k8sSecretStore (the old mutateSecret body verbatim), fileSecretStore (per-path in-process locking, atomic temp+rename preserving an existing file's mode, absent-stays-absent and no-rewrite-on-equal contracts preserved so the world server's dir-watcher sees exactly one complete replacement per real change).
- RefreshStore, worldWriteTokenStore, NewServer all take SecretStore; the audit's prediction held (one interface, ~5 files). ~30 test call sites converted mechanically to NewK8sSecretStore wrapping.
- Config: `storage: {backend: kubernetes|file, dir}` (defaults kubernetes, fully back-compat), `WorldConfig.TokensFile`; file mode requires dir + per-world tokensFile + internalAddress and drops the namespace/Secret requirements; validateStorage split out for gocyclo.
- main.go: file mode skips k8s client construction entirely; Sweeper gains Run (no leader election) for single-instance deployments.
- Tests: file-store contract suite (create/update, absent-stays-absent, no-rewrite-on-equal via mtime, mode preservation 0640, mutate-error no-write, concurrent no-lost-updates), config validation both modes, and TestProvisionFileBackend pinning the seam: Provision mints, hash lands in the world's local tokens.toml, broker-restart re-provision converges on the same token without rewriting the file.
- Verified live: broker binary boots on a plain host with `backend: file` (healthz ok, single-host sweeper, zero k8s references in logs); and the server hot-reload seam, a rename-replaced tokens.toml (the file store's write style) authorizes a publish with the new token immediately, no restart.

Remaining for step 2: non-k8s packaging (systemd/compose, install.sh --with-broker --with-library) and a full OIDC-in-the-loop e2e. Refresh tokens persist to storage.dir/refresh_tokens.json via the same interface, so VPS restarts keep sessions.


## PR #262 review round (CodeRabbit, 9 findings, all accepted)

Strong round; the file store is credential infrastructure and three findings were production-grade catches:

- **Ownership preservation**: CreateTemp+rename re-owned the tokens file to the broker user and its primary group, silently revoking the world server's group-read on the first mutation. Fixed with chownPreserving: restore uid+gid; on EPERM fall back to gid-only (an unprivileged broker can always keep a group it belongs to); error with an actionable message if neither works. Platform split via storage_unix.go/storage_other.go (syscall.Stat_t).
- **Directory fsync after rename**: file contents were fsynced but the rename's directory entry was not; a crash could acknowledge a credential mutation and boot with the old file. Added syncDir.
- **Path collision validation**: a world tokensFile aliasing storage.dir state files (or another world's file) would have two stores mutating one document; validateFilePaths rejects with filepath.Clean comparison, tested including a non-clean alias.

Also fixed: temp-file cleanup errors joined into the returned error instead of discarded; RefreshStore gained a file-backend lifecycle test (issue, restart-with-fresh-store, refresh, revoke) proving backend neutrality and restart persistence; concurrency test now surfaces every goroutine's Mutate error; no-rewrite test asserts os.SameFile in addition to mtime (mtime alone passes falsely within timestamp resolution); stale kubernetes-client comment on Server.refreshStore updated; three verbose comments trimmed to invariants.

Lesson (file store): atomic-rename file replacement has three durability/identity obligations beyond the rename itself: preserve mode AND ownership, fsync the parent directory, and treat cleanup failure as an error. Each is invisible in tests on a friendly filesystem and bites in production.