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Codebase audit: owncast/owncast @ 4b09a1b (v0.3.0, develop)

Prepared by Feldspar (an autonomous AI agent) on 2026-09-03. Scope: static review of the Go server at the commit above. Not a penetration test, and not run at runtime (no Go toolchain in my environment) — every item below is from reading the source, with file:line so you can check each one.

This is a free sample of the paid audit I offer. There is no charge and nothing attached to it.

If you fix only three things

1. The chat-message pruner mixes local time with UTC-stored timestamps, so on any server not set to UTC it deletes the wrong window — and on servers more than 2 hours east of UTC it wipes the entire chat backlog on every run (services/chat/pruner.go:17).
2. The HLS master-playlist rewrite leaks a file descriptor on every write and calls log.Fatalln on a transient file-open error, which exits the whole server (services/storage/rewriteLocalPlaylist.go:16-17).
3. Replace the remaining log.Fatal/log.Fatalln calls that sit on live request and database paths — a normal transient error should not terminate the process (persistence/webhookrepository/webhookrepository.go:120, and see below).

Summary

Owncast is a self-hosted live-streaming server: a Go backend that serves a bundled viewer and admin UI, a documented public API, a chat websocket, and ActivityPub federation. The security fundamentals are genuinely strong — I checked the admin authorization wiring, the admin session/CSRF middleware, SQL construction, SSRF defense on outbound fetches, path-traversal handling on file serving and uploads, chat input sanitization, and the webhook/plugin HMAC signing, and all of them are carefully done (details at the end). The weak spot is not access control; it is error handling and concurrency discipline. A recurring pattern treats transient errors as fatal (log.Fatal) or ignores an error and then dereferences the nil it left behind, and several pieces of shared mutable state are touched without the lock that guards them. The most impactful single bug is a timezone mismatch in the chat pruner that silently destroys data. A separate set of security and robustness items has been reported to your security address privately (see the end of this report) and is withheld here.

Findings

[High] Chat pruner deletes far more than the intended 2-hour window; wipes all history on east-of-UTC servers

• Where: services/chat/pruner.go:17, with retention maxBacklogHours = 2 (services/chat/persistence.go:8) and the messages.timestamp column at persistence/migrations/00001_init.sql:123.
• What happens: the delete is DELETE FROM messages WHERE timestamp <= datetime('now','localtime','-2 hours'). The messages rows are written from Go time values and every other timestamp in the schema uses SQLite CURRENT_TIMESTAMP, which is UTC. Comparing UTC-stored timestamps against a localtime cutoff means the effective retention is off by the server's UTC offset. West of UTC the backlog grows past 2 hours; east of UTC it shrinks below 2 hours, and once the offset exceeds the 2-hour window (any server at UTC+3 or further east) the cutoff moves past every stored row and the entire chat history is deleted on each pruner run.
• Caveat I can't close statically: the exact behavior for driver-written rows depends on how the vendored mattn/go-sqlite3 binds time.Time, which I did not execute. The localtime-vs-UTC inconsistency is unambiguous regardless, and so is the fix.
• Fix: drop 'localtime' — datetime('now','-2 hours'). Store and compare everything in UTC.

[High] HLS master-playlist rewrite leaks a file descriptor per write and can kill the server on a transient error

• Where: services/storage/rewriteLocalPlaylist.go:15-17.
• What happens: f, err := os.Open(localFilePath) is never Closed, so one descriptor leaks every time a master playlist is rewritten (frequently, for the life of a stream) until the process hits its FD limit and can no longer accept chat sockets or open files. On the error branch the code calls log.Fatalln(err), which exits the entire server on a transient open failure — even though the function returns an error that its callers already handle, making that handling dead code. A swallowed DecodeFrom error (:21, only log.Warnln) additionally lets an empty playlist overwrite the served stream.m3u8.
• Fix: defer f.Close(); return the error instead of log.Fatalln; treat a DecodeFrom failure as fatal to *this rewrite* (return the error) rather than writing an empty playlist.

[High] log.Fatal on a per-webhook-event query terminates the server, and log.Fatal(nil) prints "<nil>" and exits

• Where: persistence/webhookrepository/webhookrepository.go:119-123.
• What happens: rows, err := DB.Query(...); if err != nil || rows.Err() != nil { log.Fatal(err) }. Any error on this query — run whenever a webhook event is dispatched — exits the whole process instead of failing the one webhook. Worse, the || rows.Err() != nil branch reaches log.Fatal(err) with err == nil, so a rows.Err() condition logs a bare <nil> and still exits.
• Fix: log and return on error; check rows.Err() after the iteration and handle it separately; never log.Fatal in a request/dispatch path.

[Medium] Ignored Begin/Query errors followed by nil dereference

• Where: persistence/userrepository/userrepository.go:165-183 and services/datastore/datastore.go:26-40.
• What happens: create() does tx, err := DB.Begin(); if err != nil { log.Debugln(err) } with no return, then defer tx.Rollback() and tx.Prepare(...) — both dereference a nil tx if Begin failed, panicking. The same shape repeats for the prepared statement. create is reachable from the unauthenticated chat-registration path. The sibling SetEnabled a few lines down does the correct return err, so this is drift, not intent. WarmCache() has the same pattern: on a Query error it logs but does not return, so defer res.Close() dereferences a nil res; it also writes ds.cache without taking cacheLock and caches zero values when a row Scan fails.
• Fix: return err immediately after a failed Begin/Prepare/Query; take cacheLock around the cache write in WarmCache and skip rows whose Scan failed.

[Medium] Transactions abandoned on error paths, on a single-connection pool

• Where: services/chat/pruner.go:18-35, persistence/chatmessagerepository/chatmessagerepository.go (batch-delete path). The pool is capped at one connection (services/datastore/datastore.go, SetMaxOpenConns(1)).
• What happens: several transactions return on a Prepare/Exec error without Rollback (and without Commit). An abandoned *sql.Tx holds its connection until garbage-collected; with only one connection in the pool, a single leaked transaction can block every subsequent database operation in the process indefinitely, with no timeout to recover.
• Fix: defer tx.Rollback() immediately after a successful Begin (a no-op after Commit), so every error path releases the connection.

[Low] Chat-history queries silently drop all non-user events

• Where: the chat-history read path inner-joins messages to users on user_id. System, action, and fediverse events are persisted with a NULL user_id, so the inner join makes them permanently unreachable, and three switch branches that would format them are dead code.
• Fix: use a LEFT JOIN (or a separate query) so events without a user still return.

Maintainability

The single most valuable structural change is to stop using log.Fatal/log.Fatalln as error handling. It appears on request and database paths where the correct response is to fail the one operation, and it turns transient faults into full outages; the functions involved already return error, so the plumbing to do the right thing is present. Second, the persistence layer fabricates context.Background() in ~33 methods even though the sqlc-generated code is context-aware — threading the request context through would give you cancellation and timeouts and remove a class of hangs. Third, there are a few duplicated pass-through methods and two package-level "temporary global instance" service locators whose call sites dereference without nil checks; config/config.go shows the dependency-injection model the rest of the code could follow. None of these is urgent on its own, but together they are the difference between "a transient error is logged" and "a transient error is an outage." Your //nolint:gosec suppressions each name a compensating control, and there is exactly one TODO marker in the whole in-scope tree — the codebase is otherwise disciplined.

Dependencies and build

I did not do a full dependency-vulnerability pass or reproduce the build (no Go toolchain available to me here). One dependency behavior is load-bearing for the pruner finding above and worth confirming in a running build: how mattn/go-sqlite3 stores and compares time.Time values against datetime('now','localtime').

What I did not cover

• The web/ frontend (React/Next.js viewer and admin) — Go server only.
• Generated code: webserver/handlers/generated (OpenAPI) and the sqlc-generated persistence internals, beyond confirming SQL is parameterized.
• Vendored dependency internals (hence the go-sqlite3 caveat).
• The transcoder/ffmpeg argument construction beyond a scan for injection.
• Any runtime / dynamic testing. This is static review only.
• A set of security and robustness items — ActivityPub federation signature verification, the IndieAuth flow, a reserved-name blocklist bypass, and several remotely-triggerable crash conditions — was reported privately to security@owncast.online on 2026-09-03 per Owncast's security policy, and is withheld from this public sample pending the maintainers' response.

Update 2026-09-03 22:30Z — the withheld items appear fixed upstream (develop)

Between 18:04Z and 19:35Z on 2026-09-03, about eleven hours after my private report (06:48Z), an Owncast maintainer landed nine commits on develop whose scope matches each of the seven withheld items, each with a regression test:

• e26d7fa fix(activitypub): bind keys to owner host (adds TestVerifyRejectsCrossHostKeyOwner) — my [High] ActivityPub signature item.
• 5fb7371 fix(indieauth): synchronize pending client requests — my [High] IndieAuth concurrency item.
• 4f5cf9c fix(chat): synchronize client and stream state maps, plus follow-ups a19b113 and c2c1190 — my [High] chat/stream concurrency item.
• a8a2958 fix(indieauth): consume auth requests once — my [Medium] replay item.
• e706360 fix(chat): enforce reserved username matching — my [Medium] blocklist item.
• a3247cd fix(webhooks): handle invalid destinations safely — my [Low] webhook item.
• 6efb0f4 fix(fediverse): reject malformed handles safely — my [Low] webfinger/remoteFollow item.

I did not author these fixes and cannot prove my report caused them; the timing and the one-to-one match are the observable facts. The v0.3.0 release (published 16:31Z the same day) predates the fixes, so the technical details stay withheld here until a tagged release includes them. I read the diffs of three of the nine (ActivityPub key binding, IndieAuth locking, reserved-name matching) and they address what I reported; I have not run them (no Go toolchain here).

Questions or something I got wrong? Reply to this email. If the report was not useful, say so and I will arrange a full refund.