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Johnathan Corgan
f4ac842d3a
Carries the security batch onto this line. Most of it merged as text; the forged-ack rollback had to be re-implemented, because this line runs XX where the other two run XK and the function the helper wraps does not exist here. The defect is the same shape under XX: the reader mixes the sender ephemeral into the symmetric state before the first authenticating operation, so a forged message poisons a handshake that is then kept. The saved field set is larger here, five rather than four, and the extra one matters: XX msg2 carries the responder static and stores it before the epoch decrypt that can still fail, so a failed read would otherwise leave an attacker key where the identity check reads it. The helper returns a rollback token rather than unit, because the two extra failure sites on this line need to roll back after a read that succeeded. Both of those sites now keep the entry. The negotiation-payload failure is plainly forgery-reachable, since the identity comparison has not run yet. The responder-identity mismatch is the sharper case and also keeps: it proves the sender of the datagram is not who we dialled, but the claimed source is an envelope field, so the forgery reading is available to anyone who can reach us, and dropping would hand out a one-datagram cancel of any initiation. It was a silent return and now has its own counter, kept separate from the read failure so a stale key mapping and somebody answering under their own identity cannot be summed together. This line carries six sites of the epoch-discard class, not the five the other lines have; the sixth is the negotiation payload split out of XX msg3. One fix was dropped by a clean auto-merge and restored: the change at the msg3 read failure slid onto an adjacent site that is unique to this line, leaving the original with the destructive call, no conflict and no warning. Its doc comment, counters and tests all arrived without it. Caught by sweeping the cleanly-merged files, and confirmed by reverting the line and watching the epoch-survival assertion fail. The profiler row-count guard is updated for the step this merge brings up. It has now caught a merged-in step twice. Green: fmt, build, clippy and test --lib, 1956 passed, plus the profiling recorder suite.
FIPS Design
Architectural and protocol-level explanations for FIPS — the why and the how behind the wire and the system. For wire formats and configuration keys, see reference/. For task recipes, see how-to/. For end-to-end lessons, see tutorials/.
Reading Order
Start with fips-concepts.md for the novice-friendly framing of what FIPS is and why, then move to fips-architecture.md for the protocol stack, identity model, and two-layer encryption walkthrough. From there, follow the protocol stack from bottom to top. After the stack, fips-mesh-operation.md explains how the pieces work together at runtime. Cross-cutting and supporting documents cover specific subsystems in detail.
Foundations
| Document | Description |
|---|---|
| fips-concepts.md | What FIPS is, why it exists, mental model |
| fips-architecture.md | Protocol stack, identity, two-layer encryption |
| fips-prior-work.md | Designs and protocols FIPS builds on |
Protocol Stack
| Document | Description |
|---|---|
| fips-transport-layer.md | Transport layer: datagram delivery over arbitrary media |
| fips-mesh-layer.md | FIPS Mesh Protocol (FMP): peer authentication, link encryption, forwarding |
| fips-session-layer.md | FIPS Session Protocol (FSP): end-to-end encryption, sessions |
| fips-ipv6-adapter.md | IPv6 adaptation: TUN interface, DNS, MTU enforcement |
Cross-Cutting
| Document | Description |
|---|---|
| fips-mmp.md | Metrics Measurement Protocol (link + session) |
| fips-mtu.md | Path MTU model, encapsulation overhead, PMTUD |
| fips-security.md | fips0 interface threat model and default-deny baseline |
Mesh Behavior
| Document | Description |
|---|---|
| fips-mesh-operation.md | How the mesh operates: routing, discovery, error recovery |
| fips-nostr-discovery.md | Optional Nostr-mediated peer discovery and UDP NAT hole-punch |
| port-advertisement-and-nat-traversal.md | Nostr-signaled port advertisement and UDP NAT-traversal protocol; generic, with FIPS as an example implementation |
Deeper Dives
| Document | Description |
|---|---|
| fips-spanning-tree.md | Spanning tree algorithms: root discovery, parent selection, coordinates |
| fips-bloom-filters.md | Bloom filter properties: FPR analysis, size classes, split-horizon |
| spanning-tree-dynamics.md | Spanning tree walkthroughs: convergence scenarios, worked examples |
Adjacent Components
| Document | Description |
|---|---|
| fips-gateway.md | fips-gateway service: outbound (LAN-to-mesh) DNS-proxy + virtual-IP NAT and inbound (mesh-to-LAN) port-forwarding, sharing one nftables table |