Tailscale sends the sentinel time.Unix(123, 0) on logout; storing it
verbatim propagates a 1970 KeyExpiry to every peer's netmap. Same
semantics (expired as of now), saner logs and debug dumps.
NodeCanHaveTag, TagExists, ViaRoutesForPeer checked pm.pol before
taking pm.mu, racing SetPolicy's write (caught by -race in
TestRaceConcurrentServerMutations). DebugString read pol, filter, and
the derived maps with no lock at all.
AddNode registers the connection before sending the initial map, so a
batched delta could land first and become the stream's first frame;
Tailscale clients then kill the poll with "initial MapResponse lacked
Node" and a retry loop under steady change traffic leaves the netmap
empty. Skip connections awaiting their initial map and retry the
change next tick — the in-flight map may predate it, so it cannot be
dropped. Retries are prepended to keep patch order.
Mirrors the flaky integration relogin tests with production batcher
tuning. The churn variant restarts map polls around login like newer
tailscaled does; pre-fix it stranded nodes online after logout 2/2.
A cancelled map request whose handler ran late could Connect after the
live session, steal the newest SessionEpoch, then exit without
disconnecting (stillConnected path); the live session's final
Disconnect was rejected as stale and the node stayed online forever
(relogin flake). Counted releases are order-independent, so overlapping
sessions cannot strand a node in either direction.
Sentinel ErrNodeKeyInUse (err113); key the visible-peer set by tailcfg.NodeID
to drop an int64->uint64 cast (gosec G115); NewRequestWithContext (noctx); wsl.
filterVisiblePeerPatches and filterVisibleNodes now share one visiblePeerIDs
helper using the live MatchersForNode/ReduceNodes set, so paths cannot drift.
TestReAuthWithDifferentMachineKey asserted that a second machine claiming an existing NodeKey succeeds, but that hijack (now rejected by f8f08cf7) poisoned the NodeKey index and DoS'd the original node — the test only checked the hijacker's node, never the original's survival. Assert the registration is rejected and the original node survives intact.
noiseServer.nodeKey was assigned on every PollNetMap and Register request but never read anywhere. The inner HTTP/2 mux multiplexes concurrent requests over one Noise session, so those per-request writes to the shared field raced (caught by -race in servertest TestConnectDisconnectRace, reachable by a client issuing concurrent map requests). Remove the dead field and its two writes.
addNextDNSMetadata dereferenced node.Hostinfo().OS() without the .Valid() guard its siblings (RequestTags, TailNode) apply, so building the DNS config for a node with nil Hostinfo (a legacy NULL host_info row) panicked whenever a NextDNS resolver was configured. Guard the OS() dereference.
applyAuthNodeUpdate rotated the node's NodeKey to the client-supplied value without the 1:1 NodeKey/MachineKey check createAndSaveNewNode (f8f08cf7) and getAndValidateNode enforce. A re-authenticating node could thus rotate its key to a victim's and poison the NodeStore NodeKey index, denying the victim service. Apply the same uniqueness check on the re-auth path.
buildFromChange's PeersChanged path passed an unfiltered changed-node slice to WithUserProfiles, while the full-map path uses the BuildPeerMap-filtered ListPeers. A node thus received the identities (login name, display name, avatar) of users owning peers its ACL forbids accessing. Filter the UserProfiles peer set via the same ReduceNodes visibility check buildTailPeers applies.
buildFromChange added PeersChangedPatch (online/offline, endpoint, key-expiry) directly, skipping the policy.ReduceNodes visibility filter that buildTailPeers applies to full peers. A node thus received the existence, presence, and addresses of peers its ACL forbids accessing. Restrict patches to the recipient's visible peer set.
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.
createAndSaveNewNode trusted the client NodeKey without checking it was already bound to a different machine, so an authenticated party could register a node carrying a victim's public NodeKey, poison the NodeStore NodeKey index, and make the victim's MapRequest resolve to the wrong node (rejected by getAndValidateNode = DoS). Enforce the 1:1 NodeKey/MachineKey binding at registration, as poll time already does.
The autogroup:self SSH-check branch dereferenced node.User().ID() guarded only by !IsTagged(); a non-tagged node with an unhydrated User (UserID set, association nil) crashed the server via the Noise SSH-check path. Gate on User().Valid() like filter.go, same shape as 171fd7a3.
Kristoffer Dalby
kloba