Defence-in-depth fixes to the OIDC login flow.
Set the state/nonce cookie Secure flag from the configured server_url
scheme rather than req.TLS, so the cookies stay Secure behind a
TLS-terminating reverse proxy where the proxy-to-Headscale hop is plain
HTTP. Deriving it from config avoids trusting a spoofable
X-Forwarded-Proto header.
Make the OIDC state single-use: consume it from the cache on the
callback and clear the state/nonce cookies once validated, so a replayed
callback cannot resolve the same session and the cookies do not linger
until expiry.
Bound OIDC discovery to the caller's context so a slow or unreachable
issuer fails startup within the timeout instead of hanging, and validate
the issuer URL and required client_id/client_secret at config load so an
unworkable setup fails fast.
The new full-tree golangci-lint check reports issues the --new-from-rev
diff lint hid: nine wsl_v5 whitespace gaps, a prealloc, and an unparam
(setCSRFCookie never errored, so drop the return and update callers).
gocyclo on the central UpdateNodeFromMapRequest and an SA1019 NetMap
deprecation in an integration helper are suppressed with reasons.
Sentinel ErrNodeKeyInUse (err113); key the visible-peer set by tailcfg.NodeID
to drop an int64->uint64 cast (gosec G115); NewRequestWithContext (noctx); wsl.
setCSRFCookie set no SameSite attribute despite a nolint comment claiming it did, so the OIDC state/nonce cookies relied on the browser default. Set Lax explicitly (Strict would drop the cookie on the cross-site IdP->callback navigation and break login), hardening browsers that do not default to Lax against OIDC login CSRF.