Johnathan Corgan
6a564e26ac
Everything the release needs except the version number, which stays at 0.5.0-dev until the tag. The changelog entry covers only the work that is new on this line. The point release's forty-six entries arrived under their own heading with the forward merge and are left alone; the twenty that remained are regrouped by topic and eight more added for changes no entry covered. Three of those eight matter to someone upgrading. Five root modules and four re-exports left the public library surface and Node::connections narrowed, none of it recorded anywhere; the entry names what to use instead and distinguishes the removed connection-phase enum from the Noise type of the same name, which is a different type that still exists. Tracing targets moved, so an existing RUST_LOG filter stops matching rather than erroring. And the handshake resend interval key no longer governs the first resend, which is now a constant, though it still governs later ones. Seven more entries cover the work that landed after the first content pass was written: the experimental native datagram API, the fipsctl probe diagnostic, per-instance transport addressing, the app-owned UDP socket seam, and the connect, disconnect and path-MTU fixes. The four bug fixes among them all reach the deployed line, so the release notes no longer claim this release carries exactly one fix for a shipped bug; it carries four. There is no security section, because after the split every security entry belongs to the point release. The release notes say so plainly rather than leaving a reader upgrading across both releases to conclude this one carries no security work. The notes are organized by audience, since the release spans OpenWrt routers, embedders, FreeBSD, and the existing platforms, and a single list serves none of them. The native datagram API is given a section of its own rather than folded into the embedding seam: it is a client-facing API rather than a way to host a node, and its one rule with no Berkeley-socket counterpart, that the v1 wire carries no half-close, needs to be somewhere a client author will read it. FreeBSD is advertised as supported on x86_64 only, stated wherever the platform appears. Android is advertised as an embedding seam and not as a supported platform: a compile-gated library surface with no artifact and no host application guide. The configuration table rename is carried through every shipped file that taught the old spelling: nine documentation files, the OpenWrt sample config and a test generator, twenty-two sites in all. Guides written this same cycle were among them, which is how the omission was found. The documentation that arrived with the native API was checked for the same omission and was already clean. The compatibility tests keep the old spelling deliberately, since they exist to test the fold. The changelog section is the fold of master's [Unreleased], not a snapshot of it. An earlier version of this commit took a copy that then drifted, so each section ended up holding a bullet the other did not and re-folding them would have picked a winner silently. Both causes were fixed on master instead — the NixOS module had never been recorded there, and the pre-release batch of fixes was new — so [Unreleased] is a strict superset and this is a copy rather than a merge. [0.5.0] carries all forty-six bullets byte for byte, [Unreleased] is empty, and [0.4.2] is untouched, checked by hashing it against master's copy. The BLE work landed after the content pass and gets one summary entry in the changelog and one section in the release notes rather than nine bullets: the ble_available gate replacing target_os = "linux", packet-boundary recovery for stream-oriented backends, peer recognition by node identity instead of a rotating link address, the L2CAP PSM moving into the backend seam and onto the advertisement, the embedder-supplied Android radio, bounded probe retry, and inbound handshakes moved off the accept loop. The two release-notes copies no longer share their link paths. Relative links resolve from one directory only, so the seven written for docs/releases/ all 404ed from the root copy. The root copy now uses paths from the repository root and the versioned copy keeps the ../ form; both sets were resolved against the tree. The same two links are broken the same way in the v0.4.0 through v0.4.2 notes, left as shipped history. The contributor tallies are re-derived against maint..HEAD rather than adjusted: twenty commits from outside the project and 171 from me, with Arjen at fifteen and fr34aky at two. An earlier count of twelve and 138 was carried from a measurement taken three days before this content was written, and the BLE branch widened the gap after it. Arjen's NixOS flake module, the UDP sin6_scope_id fix and most of the BLE rework were uncredited, as was fr34aky's L2CAP PSM seam. They want one last re-derive at tag time if anything lands before the tag. A sweep of all 99 tracked markdown files against the tree corrected fifty-three of them. Four told the reader to run a build.sh that does not exist; the only harness builder is testing/scripts/build.sh. The BLE build prerequisites were described as optional on the strength of a probe that build.rs does not perform, and bluez was named a build prerequisite when libdbus-sys asks only for libdbus-1-dev and pkg-config and bluez is the runtime daemon. Link cost is the primary sort key in next-hop ranking, not reserved for future use; Ethernet runs on macOS as well as Linux; the BLE MTU is the L2CAP CoC MTU rather than a negotiated ATT_MTU; effective Ethernet MTU is 1497; the LAN discovery subsystem is src/mdns and eight citations still named a src/discovery that never existed here. The connectivity states in three tutorials were invented, and their jq filters matched nothing including healthy peers. One command filtered on a literal fd97: address prefix, which only the first byte of fixes, so it returned empty for all but one reader in 256 and every later step using the variable failed silently. transports.tor.advertise_on_nostr was undocumented despite being validated against node.rendezvous.nostr.enabled. The transport design document gains the BLE section it never had, written from the source: the backend cascade and its compile_error tripwire, the platform gate, the PSM advertisement wire layout and the byte budget that forces a 16-bit service-data key, and the probe and admission bounds. Three source files carried the same class of staleness and are corrected with the documentation: the OpenWrt ipk usage line and Makefile error text both named a packaging/openwrt that does not exist, and chaos.sh parsed --subnet without listing it. Folded in with the content commit, having been prepared alongside it: The three GitHub Action pins that had gone stale. Every third-party action is pinned to a commit SHA, nothing reports that a pin has aged, and re-resolving all ten against their tags found dorny/test-reporter@v2, taiki-e/install-action@v2 and vmactions/freebsd-vm@v1 had moved. The three install-action@nextest references stay unpinned, since that action reads the tool to install from the ref name. check-action-pins.sh passes at 75 references and all nine workflow files parse. The lockfile refresh, which is the mutating half of the dependency sweep. Thirty-six packages move to their latest semver-compatible versions and every one is transitive; nothing declared in Cargo.toml changes version. No advisory forces any of them. It was taken before the validation battery, because a gate run against a lockfile that later moves proves nothing about what ships. The sha2 0.10 to 0.11, hkdf 0.12 to 0.13 and bech32 0.11 to 0.12 majors, three of the four deferred at v0.4.0 for change surface rather than security. All three land with no source change. sha2 and hkdf must move together, since both depend on digest 0.11, and neither changes an algorithm. That matters because the chaining-key KDF in the Noise handshake is built on Hkdf::<Sha256>, where an output change would be a wire break rather than a compile error; no known-answer vectors exist for that path, so the wire-compatibility gate is what covers it. secp256k1 0.31 is deliberately absent, since nostr's own requirement would leave two copies of the ECC library in the tree. The README support matrix, rebuilt as one feature table broken out by Linux variety. A single Linux column hid that Debian, Ubuntu, Arch and NixOS are one glibc build differing in packaging, that OpenWrt is musl and drops BLE, and that Android is not a daemon platform. Transport rows sort by how many platforms carry them. A Native API row reads its platform set from the cfg gates. The installer row becomes a package format row naming the artifact, and only the .deb is exercised per release. Four changelog and release-note gaps the BLE re-walk found: a Bluetooth LE bullet stranded inside the released 0.4.2 section, a missing Fixed entry for the scan and probe loop counting a pool-refused connection as an established link, the unnamed embedder call that installs an application-owned radio, and the fact that stopping the transport now stops scanning as well as advertising. Three release-document gaps found walking the unsurveyed commits: the UDP reuse-flag fix stated in the direction opposite to the one it was made, with the silent second-daemon bind it prevents left unsaid; the corrected native-API socket paragraph carried into both release-note copies, which still named SOCK_SEQPACKET on FreeBSD and two kernels where three are handled; and the coordinate-cache hardening, which shipped with no text anywhere despite adding four operator-visible status fields. That last entry states plainly that the checks are mitigations and not a closure, since the coordinate is still not authenticated. Also folded in, the documentation pass that followed the content commit: A stage-pipeline diagram for the probe, embedded in the fipsctl reference under the five-stage list. It draws the five stages left to right with each stage's failure reasons below it, and the bypass that skips both lookup stages when the coordinates are cached or the target is a direct peer. Its branches come from the probe state machine rather than from the report, so the path stage is drawn as the one failure that does not stop the probe. A rewrite of the README's "What FIPS does" section. It now opens with what a machine running FIPS gets, rather than with the two deployment modes, and gives the self-organizing and permissionless property its own paragraph since it holds for both modes. A regrouping of the README's feature list into the mesh, getting traffic onto it, and running a node, with a bullet added for the native datagram API, which had none despite sitting in the support matrix. The Quick start now leads with the released packages rather than a source build. It also fixes a real defect: the package enables fips.service and fips-dns.service and starts neither on a fresh install, so .fips name resolution was silently dead until the next reboot and neither page said to start the service. A rewrite of the release notes. They opened with seven subsections of upgrade caveats and reached the first feature two hundred lines in; they now open with a summary of the release and elaborate below it in the same order. Android is stated as supported through an embedded crate rather than as a standalone daemon, consistently across all three documents. The OpenWrt pair is corrected: it is 802.11s between routers with FIPS supplying encryption, authentication and routing, plus a convention of an open !FIPS SSID a client joins over WiFi, not meshing over a router's own radios. The probe's path output is described as the least-common-ancestor walk, which is the worst-case fallback route rather than the route a packet takes. Detail that did not change what a reader does was cut from the notes and kept in the changelog.
16 KiB
Security Reference
Consolidated security reference covering the nftables baseline, peer ACL file format, cryptographic primitives, rekey defaults, replay window, filesystem permissions, threat-resistance matrix, and default network exposures per transport. For the threat-model design and rationale, see ../design/fips-security.md. For the operator activation steps and drop-in recipes, see ../how-to/enable-mesh-firewall.md.
nftables Baseline
The shipped baseline is /etc/fips/fips.nft. It defines a single
nftables table inet fips with one chain hooked at input, structured
as follows:
| Step | Rule | Effect |
|---|---|---|
| 1 | iifname != "fips0" return |
Match only traffic arriving on fips0; everything else short-circuits. |
| 2 | ct state established,related accept |
Allow conntrack replies and related ICMPv6 errors. |
| 3 | icmpv6 type echo-request accept |
Allow IPv6 echo (ping6 reachability). |
| 4 | include "/etc/fips/fips.d/*.nft" |
Splice in operator drop-ins (empty matches nothing). |
| 5 | counter drop |
Default-deny everything else; counter increments on every drop. |
Outbound from fips0 is unrestricted. The baseline is a documented
dpkg conffile — operator edits to /etc/fips/fips.nft are preserved
across upgrades.
The systemd unit is fips-firewall.service (oneshot). It is not
enabled by default; activation is an explicit operator gesture
documented in
../how-to/enable-mesh-firewall.md.
Drop-In File Format
Operator extensions live under /etc/fips/fips.d/ with the .nft
suffix. Each file is included inline into the inbound chain at the
marked point and may contain any nftables rule lines valid in that
context.
Naming convention: <purpose>-from-<source>.nft keeps drop-ins easy
to scan. Examples shipped in the design discussion:
ssh-from-bastion.nft— accept TCP/22 from a single mesh-node addresshttp-from-cluster.nft— accept TCP/80 from a/64mesh-address prefixdns-public.nft— accept UDP/53 and TCP/53 from any mesh nodegit-from-trusted.nft— accept TCP/9418 from a set of mesh-node addresses
After editing, reload via
sudo systemctl reload-or-restart fips-firewall.service (or
equivalently sudo nft -f /etc/fips/fips.nft since the file is
idempotent).
Cryptographic Primitives
| Component | Choice | Where Used |
|---|---|---|
| Curve | secp256k1 | FMP IK, FSP XK, Schnorr signatures |
| Diffie-Hellman | ECDH on secp256k1 (x-only normalized) | Noise IK, Noise XK |
| AEAD | ChaCha20-Poly1305 | FMP link encryption, FSP session encryption |
| Hash | SHA-256 | NodeAddr derivation, Noise key schedule |
| Key derivation | HKDF-SHA256 | Noise key schedule |
| Signatures | secp256k1 Schnorr | TreeAnnounce, LookupResponse proof, Nostr adverts |
| Noise pattern (link) | Noise_IK_secp256k1_ChaChaPoly_SHA256, with the deviation below |
FMP link layer (IK with epoch payload) |
| Noise pattern (session) | Noise_XK_secp256k1_ChaChaPoly_SHA256, with the deviation below |
FSP session layer (XK with epoch payload) |
These choices align with the Nostr cryptographic stack (secp256k1 + ChaCha20-Poly1305 + SHA-256) and the NIP-44 encrypted messaging standard.
Deviation: Empty Associated Data in the Handshake AEAD
Both Noise patterns above deviate from the standard construction in one
respect. The handshake AEAD uses an empty associated-data field where
standard Noise EncryptAndHash uses the handshake hash h.
The choice was deliberate. Using secp256k1 rather than 25519 already put the construction outside standard Noise, so no standard-Noise peer could be confused with it, and the transcript hash bought no distinguishing value.
That argument is about domain separation, and on those grounds it holds. It
does not cover transcript binding, which is the property actually absent.
Domain separation and DH binding survive through the chaining key ck, which
mix_key chains from ck = h, seeded from the protocol name in
SymmetricState::initialize (src/noise/handshake.rs). The handshake hash
h is maintained at every step and is never fed to the AEAD, so it binds
nothing.
Rekey Defaults
Both link-layer and session-layer Noise sessions rekey under one of
two triggers, configurable under node.rekey.*:
| Parameter | Default | Description |
|---|---|---|
enabled |
true |
Master switch. |
after_secs |
120 |
Time-based rekey threshold. |
after_messages |
65536 |
Message-count rekey threshold. |
In addition to the configurable triggers, the daemon retains the old
session keys for a fixed 10-second drain window after each
cutover (compile-time constant DRAIN_WINDOW_SECS in
src/node/handlers/rekey.rs). Rekey rotates the Noise key schedule
and the session indices; old session keys are kept in
previous_session for the drain window so in-flight packets
encrypted under the old keys still decrypt.
Replay Window
Both layers use explicit per-packet counters with a sliding bitmap
window for replay protection. The bitmap is 2048 entries at both
layers — large enough to accommodate UDP reordering and packet loss
without false-positive replay rejection. Counters older than the
window are rejected. The same ReplayWindow and
decrypt_with_replay_check() implementation is used at both the FMP
and FSP layers.
Peer ACL
Mesh-level ACL files at /etc/fips/peers.allow and
/etc/fips/peers.deny give the operator allowlist/blocklist control
over which npubs may complete the FMP Noise IK link handshake.
File format:
- One entry per line. An entry is either a bech32
npub1..., an alias defined in/etc/fips/hosts, or the literalALLwildcard (case-insensitive). - Lines beginning with
#are comments. - Blank lines are ignored.
Evaluation order (first match wins, default-allow on no match):
peers.allow— if the peer matches an entry here (orALLis inpeers.allow), the handshake is admitted, regardless of anypeers.denyentry.peers.deny— if the peer matches an entry here (orALLis inpeers.deny), the handshake is refused.- Otherwise the peer is admitted.
peers.allow is not an exclusive gate on its own: an unlisted
peer falls through to step 3 and is admitted unless it appears in
peers.deny. To turn peers.allow into a strict allowlist, place
ALL in peers.deny so every unlisted peer is rejected at step 2.
The ALL wildcard makes the operator's posture explicit:
ALLinpeers.allowadmits every peer (same effect as the default-allow behavior, but documented in the file).ALLinpeers.denyblocks every peer except those listed inpeers.allow— the "allowlist-strict" posture.
In practice this collapses to a few common postures:
- Default-allow with denylist: leave
peers.allowempty; populatepeers.deny. All npubs may peer except those listed. - Allowlist-strict: populate
peers.allowand putALLinpeers.deny. Only the listed npubs may peer; everyone else is rejected at step 2.
A populated peers.allow with an empty peers.deny is not a
strict allowlist — it is equivalent to default-allow plus an
explicit "always-admit" set. The strict variant requires ALL
in peers.deny.
Aliases are resolved through /etc/fips/hosts at file-load
time. If peers.allow lists core-vm and /etc/fips/hosts
maps core-vm to a specific npub, that npub is admitted. If
core-vm is later remapped to a different npub, the ACL
re-resolves on the next mtime change. Operators should be aware
that ACL semantics follow the hosts-file aliasing, not just
the literal npubs visible in the file.
Both files are reloaded automatically when their mtime changes — no daemon restart or signal is needed. ACL evaluation runs after msg1 decryption but before any further peer-state mutation; rate-limited msg1s never reach the ACL.
Filesystem Permissions
| Path | Owner | Mode | Purpose |
|---|---|---|---|
/etc/fips/fips.key |
root:root | 0600 |
Persistent identity private key (sensitive). |
/etc/fips/fips.pub |
root:root | 0644 |
Public key (npub). |
/etc/fips/fips.yaml |
root:root | 0644 |
Daemon configuration (dpkg conffile). |
/etc/fips/fips.nft |
root:root | 0644 |
nftables baseline (dpkg conffile). |
/etc/fips/fips.d/ |
root:root | 0755 |
Operator drop-in directory. |
/etc/fips/hosts |
root:root | 0644 |
Optional hostname → npub map (dpkg conffile). |
/etc/fips/peers.allow |
root:root | 0644 |
Optional peer allowlist. |
/etc/fips/peers.deny |
root:root | 0644 |
Optional peer denylist. |
/run/fips/control.sock |
root:fips | 0770 |
Control socket (members of fips group can use fipsctl). |
/run/fips/api.sock |
root:fips | 0770 |
Native datagram API socket, when node.native_api.enabled is set (experimental; absent otherwise). |
/run/fips/ |
root:fips | 0750 |
Socket parent directory. |
Adding a user to the fips group grants fipsctl access without
requiring root. The daemon chowns the control socket and its parent
directory at bind time, and does the same for the native API socket when
that is enabled.
Native Datagram API
Experimental. Disabled by default (node.native_api.enabled, default
false), and built on Linux, FreeBSD and macOS only. It is not a stable API
surface, not a reliability layer, and not the v2 external process API. No
compatibility promise is made about it.
Any user in the fips group can impersonate the node on the mesh. The
API socket is created at mode 0770 owned by group fips, and that is the
entire authorization model. A process that can open it can:
- send datagrams under this node's identity to any peer it names, which peers authenticate as coming from this node;
- hold any port from 1024 upward and receive mesh traffic addressed to this node on it, including traffic another local program expected;
- do both without authenticating, without a capability check, and without any record beyond the daemon's own logs.
Group membership is therefore equivalent to possession of the node's
identity for the purpose of sending on the mesh. On a node with the native
API enabled, treat membership of the fips group exactly as you would treat
/etc/fips/fips.key. Grant it to the accounts that are trusted to speak as
the node and to no others, and review it before enabling the API on a shared
machine.
The file descriptor carries the grant, not the connection. A setup call
hands the client a socket descriptor and the connection it was made on is then
closed; the flow or the held port lives until that descriptor is closed. A
descriptor is an ordinary kernel object, so it survives fork, survives
exec unless the client asked for it close-on-exec when it received it, and
can be handed to another process over SCM_RIGHTS. A process holding one can
send as this node on that flow, or receive on that port, without ever opening
the API socket and without being in the fips group.
Nothing revokes a descriptor already handed out. Restarting the daemon closes
its own halves and ends every flow and listener at once, and that is the only
revocation there is.
Two consequences follow for fipsctl access. First, the fips group is
already the control-socket group, so enabling the native API silently
upgrades every existing fipsctl user from "can read node state and manage
peers" to "can send as the node". Second, an operator who wants the two
audiences separated must not enable the API on a node whose fips group has
been handed out for monitoring.
node.native_api.debug_commands (default false) is a second, independent
gate. It admits three commands (inject, stats, arrive) that exist for
the test harness: arrive makes the daemon dispatch a datagram as though a
peer had sent it, reaching any listener on this node under any peer identity
the caller names. Leave it off outside a test harness; a packaged node does
not enable it.
The socket is local only. It is not reachable over the network, and nothing about it changes the mesh's own authentication: a peer still verifies the node's signature, which is precisely why a local caller that can send through this socket is indistinguishable from the node itself.
See configuration.md for the key list and ../how-to/use-the-native-datagram-api.md for the client.
Threat-Resistance Matrix
The link layer's threat-resistance matrix is consolidated here from the FMP design document:
| Threat | Mitigation |
|---|---|
| Connection exhaustion | Token-bucket rate limit + connection count limit |
| CPU exhaustion (msg1 flood) | Rate limit before crypto operations |
| Replay attacks | Counter-based nonces with sliding window (2048 entries) |
| State confusion | Strict handshake state machine validation |
| Spoofed encrypted packets | Index lookup + AEAD verification |
| Spoofed msg2 | Index lookup + Noise ephemeral key binding |
| Address spoofing | Cryptographic authority, not address-based |
| Session correlation | Index rotation on rekey |
Inbound exposure on fips0 |
Default-deny nftables baseline (operator opt-in) |
| Sybil identities | Discretionary peering + handshake rate limiting + optional peer ACL |
| Eclipse attack | Diverse peering across independent operators and transports |
| Unauthorized peer admission | Optional peers.allow allowlist consulted before handshake |
| Local impersonation via the native datagram API | API disabled by default; when enabled, fips group membership is the only gate and must be treated as key access |
See ../design/fips-mesh-layer.md for the unauthenticated-attack-surface analysis (only handshake msg1 is reachable by unauthenticated parties), and ../design/fips-mesh-operation.md for the metadata-privacy model and the rejection of onion routing.
Default Network Exposures by Transport
| Transport | Default Inbound | Default Bind | Opt-in |
|---|---|---|---|
| UDP | None until bind_addr set |
0.0.0.0:2121 typical |
Operator sets transports.udp.bind_addr |
| TCP | None until bind_addr set |
None — outbound-only without bind | Operator sets transports.tcp.bind_addr |
| Ethernet | Listens on configured interface (raw AF_PACKET) |
EtherType 0x2121 on selected interface | Per-flag listen, announce, auto_connect, accept_connections |
| Tor | None until directory_service configured |
127.0.0.1:8443 (loopback only) |
Operator sets transports.tor.directory_service and configures HiddenServiceDir in torrc |
| BLE | Off by default | n/a | Operator enables transports.ble.* |
| Nostr discovery | Off by default | n/a (relay client, not a listener) | Operator sets node.rendezvous.nostr.enabled: true |
The mesh-layer fips0 interface is reachable from any mesh node that
can route to you, not only direct peers — your direct peers forward
traffic from any reachable mesh node onto your fips0. The
default-deny nftables baseline (operator opt-in) is the recommended
way to restrict inbound traffic on fips0. See
../how-to/enable-mesh-firewall.md.
See also
- ../design/fips-security.md — threat
model and design rationale for the
fips0baseline - ../design/fips-mesh-layer.md — FMP link encryption, replay protection, rate limiting
- ../design/fips-session-layer.md — FSP end-to-end encryption, Noise XK, replay window
- ../how-to/enable-mesh-firewall.md — operator activation and drop-in recipes
- configuration.md — full
node.rekey.*,node.rate_limit.*parameter tables - ../how-to/use-the-native-datagram-api.md — enabling the experimental native datagram API, and what group membership grants once it is on