feat(mirror): verify a peer's mirror-coin bond against chain on the download path

Cargo.toml

@@ -32,7 +32,7 @@ edition = "2021"
 # the ROOT manifest (`[workspace.package].version`), so it MUST be set here for a
 # release to fire (§3.6). The library crates (dig-node-core/dig-runtime/dig-wallet)
 # keep their own independent versions — only the released binary tracks the workspace version.
-version = "0.206.0"
+version = "0.207.0"
 
 # Release hardening, matching digstore: keep integer-overflow checks ON in release.
 # The node parses untrusted serialized input and does offset/length arithmetic over

SPEC.md

@@ -8204,6 +8204,11 @@ itself (SYSTEM.md §4.1).
 >   by name BEFORE any chain read (dig-node#426). **RECLAIMS are implemented** and are supported at `fee = 0` with
 >   no fee coins, which is §25.4.4 — and are never gated on any funding read, including the
 >   committed-coin read.
+> * **§25.10's verification of OTHER peers' claims is implemented** — `dig-node-core`'s
+>   `mirror_bond` (the three verdicts and the ranking locator, installed inside `NodeContent::new`)
+>   and `dig-node-service`'s `mirror/bond_verify.rs` (the chain read, installed on the running node
+>   by `spawn_bond_verifier_install`). What is verified is a peer's claim; this node still attaches
+>   no pointer of its own, per the next bullet.
 > * **§25.6's DHT pointer is not attached.** `ProviderRecord::unverified_mirror_coin_id` lives in
 >   dig-dht 0.15, and `dig-download` 0.21.0 and `dig-peer-selector` 0.10.0 both require
 >   `dig-dht ^0.13` — semver-incompatible on a `0.x` line, so taking 0.15 here would resolve two
@@ -8555,6 +8560,58 @@ collateral, and `MirrorCoin::advertises(store, root, epoch)` passes — an exact
 declared tuple plus a recomputed hint, which is what defeats the constructible additive-morph
 collision (the epoch term is freely chosen, so hint equality alone proves nothing).
 
+### 25.6a. Acting on another peer's claim
+
+A node that LOCATES a holder verifies that holder's claimed bond and **promotes a proven one**. The
+verdict has three states, which are never collapsed into two, but the ranking has exactly TWO tiers:
+
+| verdict | established | ranking |
+|---|---|---|
+| bonded | the named coin passes every §25.6 check for this exact `(store, root, epoch)` AND declares the peer claiming it | promoted |
+| unverified | no pointer was published, the chain could not answer, this node holds no censused requirement for the epoch, or the coin does not declare the claimant | baseline, position unchanged |
+| unbonded | the chain answered and the claim is false | baseline, position unchanged |
+
+**Ranking gives credit; it MUST NOT take credit away.** A provider record is hearsay — whoever
+answers a lookup chooses every field of it, including a coin id it attributes to somebody else — so a
+disproven pointer MUST NOT rank a holder below where no pointer at all would have put it. Otherwise
+attaching a bogus coin id to an honest holder's record would be a demotion primitive available to any
+stranger at no cost. Withholding credit has no such abuse: the most a liar achieves is the ranking
+that would have existed had it said nothing.
+
+**A coin id proves the bond, never the bearer.** A coin id is a public fact, so a coin that bonds the
+content says nothing about WHO is offering it; a record may carry an honest holder's peer id, that
+holder's real coin id, and the attacker's addresses. Promotion therefore additionally requires the
+coin's own owner-written declaration of the claiming `peer_id`, and a node that cannot read such a
+declaration MUST NOT promote. A dialler is not a backstop for this: peer ids are derived from the
+presented certificate rather than pinned against the dialled identity.
+
+**One locate is bounded work.** The size of a located set is chosen by whoever answered the lookup,
+so a node MUST bound the number of bonds it reads against a chain per locate, verifying in source
+order and leaving the remainder at baseline.
+
+The verification is performed in the ORDER §25.6 states, with one refinement that is normative: the
+`advertises` binding is checked BEFORE the collateral magnitude. A node that has not censused the
+epoch cannot price a bond, and checking magnitude first would make every verdict on such a node
+`unverified` — including a holder pointing at a coin that plainly bonds a different store.
+
+**A holder is never refused, dropped, or blocklisted on a verdict.** A chain outage, an epoch
+rollover, a republished record carrying a pointer that has since gone stale, and a deliberate lie are
+indistinguishable at the moment of reading, and only one of them is an attack; a node that refuses on
+any of them converts its own partition into a rejection of honest peers. Promotion is the whole
+remedy: a holder that proves its bond is served first, and every other holder keeps exactly the
+standing its source gave it.
+
+Absence of a pointer is the ORDINARY case and MUST cost no chain read at all. `unverified` for an
+absent pointer is not a degraded answer — it is the honest state of a claim nobody looked at.
+
+A verdict is cached only for the exact `(coin id, store, root, epoch)` it answered, because one coin
+bonds one tuple; caching by coin id alone would let a genuine bond answer for content the same coin
+does not bond, which is the substitution `advertises` exists to refuse. Only DEFINITE verdicts are
+cached: `unverified` records this node's own momentary inability to look, and holding it would keep
+an outage in force after it had ended. The cache is keyed partly on attacker-chosen input, so it MUST
+be bounded, and overflow MUST evict rather than clear — clearing would let a stranger discard every
+verdict a node has earned by rotating coin ids.
+
 ### 25.7. Consent, the switch, and revocation
 
 > **PARTIALLY PENDING.** The switch itself is real — it persists in `collateral.json`, defaults on,

crates/dig-node-core/Cargo.toml

@@ -30,7 +30,7 @@ name = "dig-node-core"
 # dig-node#276/#296). Changing a public return type is BREAKING for an out-of-workspace implementor;
 # this crate is consumed in-workspace only and is pre-1.0, so it is a MINOR bump under SemVer's 0.x
 # rule -- recorded here rather than letting the number imply the locator surface held still.
-version = "0.65.0"
+version = "0.66.0"
 edition = "2021"
 license = "GPL-2.0-only"
 description = "The canonical DIG node ENGINE library (crate `dig_node_core`): the JSON-RPC dispatch (`handle_rpc`, the same contract as rpc.dig.net), local-first content serve/fetch/redirect from LOCAL .dig store modules (via digstore_host::serve_blind), chain-anchored-root resolution, chain-watch + subscriptions + generation gap-fill, the LRU cache, and the full P2P stack. Shared UNCHANGED by both host shells: the `dig-node` OS-service binary (dig-node-service) and the DIG Browser's in-process cdylib (dig-runtime). Native Rust so the compiled-module serve path works."

crates/dig-node-core/src/download.rs

@@ -746,6 +746,9 @@ pub struct NodeContent {
     /// [`SelfExcludingLocator`] (#1584), so discovery is already self-filtered — this node's own
     /// `peer_id` never appears as a holder — but is otherwise unranked.
     locator: Arc<dyn ProviderLocator>,
+    /// The mirror-coin bond verifier the discovery chain ranks by (dig-node#466), installed once by
+    /// the host binary through [`Self::set_bond_verifier`] when its chain source exists.
+    bond_verifier: crate::mirror_bond::BondVerifierSlot,
     /// The self-optimizing peer selector (#178) — the decision + learning brain between discovery and
     /// download. It ranks the download sources (bridged into dig-download's [`SourceSelector`] seam by
     /// [`SelectorAdapter`], #1442) and learns from every range outcome dig-download reports back
@@ -1250,6 +1253,13 @@ impl NodeContent {
         self_peer_id: Option<String>,
         cache_dir: &Path,
     ) -> Arc<Self> {
+        // The mirror-coin bond layer (dig-node#466) sits OUTSIDE every other locator, so both the
+        // raw discovery leg kept on the engine and the download union built from it below inherit
+        // one ranking. Its verifier arrives later (the host binary owns the chain source), and until
+        // it does the layer is a pass-through.
+        let bond_verifier = crate::mirror_bond::bond_verifier_slot();
+        let locator: Arc<dyn ProviderLocator> =
+            crate::mirror_bond::BondRankingLocator::new(locator, bond_verifier.clone());
         let downloads_dir = cache_dir.join("downloads");
         let _ = std::fs::create_dir_all(&downloads_dir);
         let state_store = Arc::new(CapturingStateStore::new(FileStateStore::new(
@@ -1334,6 +1344,7 @@ impl NodeContent {
         let ask_routing = AskRoutingState::new(self_peer_id.as_deref());
         Arc::new(NodeContent {
             locator,
+            bond_verifier,
             selector,
             downloader,
             state_store,
@@ -1536,6 +1547,20 @@ impl NodeContent {
         content
     }
 
+    /// Install the mirror-coin bond verifier the discovery chain ranks holders by (dig-node#466).
+    ///
+    /// Idempotent and one-way: the first call wins and later ones are ignored, so a node's
+    /// verification posture cannot change under a running download. Before it is called the layer is
+    /// a pass-through, which is the shipped behaviour of every embedder that has no chain source.
+    ///
+    /// Returns whether this call was the one that installed it.
+    pub fn set_bond_verifier(
+        &self,
+        verifier: Arc<dyn crate::mirror_bond::MirrorBondVerifier>,
+    ) -> bool {
+        self.bond_verifier.set(verifier).is_ok()
+    }
+
     /// The configured miss behavior (redirect by default; fetch-through when opted in).
     pub fn miss_mode(&self) -> MissMode {
         self.miss_mode
@@ -2522,7 +2547,7 @@ impl crate::Node {
     }
 
     /// The attached P2P content engine, if the peer network brought one up.
-    pub(crate) fn p2p_content(&self) -> Option<&Arc<NodeContent>> {
+    pub fn p2p_content(&self) -> Option<&Arc<NodeContent>> {
         self.p2p_content.get()
     }
 
@@ -4373,6 +4398,89 @@ pub(crate) mod tests {
             .is_err());
     }
 
+    /// **Proves (dig-node#466):** the bond ranking is live on the ENGINE's own discovery path —
+    /// `NodeContent::find_providers`, the source the redirect-on-miss handler names holders from —
+    /// and not merely inside a locator a test assembled for itself.
+    ///
+    /// **Catches:** the exact state this ticket exists to end. `BondRankingLocator` can be perfect
+    /// and still be reachable from nothing; the whole point of #466 is that a verifier with no
+    /// consumer changes nothing. This test builds the engine through its real constructor and asks
+    /// it, so a wiring that silently dropped the layer fails here even with every unit test in
+    /// `mirror_bond` green.
+    ///
+    /// The slate's input order is neither the expected answer nor its reverse, so an engine that
+    /// ignored the verdicts entirely cannot pass by coincidence.
+    #[tokio::test]
+    async fn the_engine_ranks_a_disproven_bond_last_on_its_own_discovery_path() {
+        use crate::mirror_bond::{BondVerdict, MirrorBondVerifier};
+
+        struct ByFirstByte;
+
+        #[async_trait::async_trait]
+        impl MirrorBondVerifier for ByFirstByte {
+            async fn verify(
+                &self,
+                _c: &ContentId,
+                _claiming_peer_id: &str,
+                claimed: Option<[u8; 32]>,
+            ) -> BondVerdict {
+                match claimed {
+                    None => BondVerdict::Unverified,
+                    Some(coin) if coin[0] == 0x01 => BondVerdict::Bonded,
+                    Some(_) => BondVerdict::Unbonded,
+                }
+            }
+        }
+
+        let td = tempfile::tempdir().unwrap();
+        let cid = mock_content_id();
+        let claimed = |peer: u8, coin: Option<[u8; 32]>| {
+            let record = mock_provider(peer, &cid);
+            match coin {
+                Some(id) => record.with_unverified_mirror_coin_id(id),
+                None => record,
+            }
+        };
+
+        let pc = NodeContent::new(
+            Arc::new(MockProviderLocator::fixed(vec![
+                claimed(7, None),             // claims nothing      -> Unverified
+                claimed(8, Some([0x02; 32])), // claims a coin bonding something else
+                claimed(9, Some([0x01; 32])), // claims a coin that really bonds this
+            ])),
+            Arc::new(MockRangeTransport::new(anchored_mock_content(30, 3))),
+            MissMode::Redirect,
+            None,
+            td.path(),
+        );
+        assert!(
+            pc.set_bond_verifier(Arc::new(ByFirstByte)),
+            "the engine accepts exactly one verifier"
+        );
+
+        let located = pc.find_providers(&cid).await.for_finding();
+        let peers: Vec<String> = located
+            .iter()
+            .map(|r| r.provider_peer_id[..2].to_string())
+            .collect();
+
+        assert_eq!(
+            peers,
+            vec![
+                mock_peer_hex(9)[..2].to_string(),
+                mock_peer_hex(7)[..2].to_string(),
+                mock_peer_hex(8)[..2].to_string(),
+            ],
+            "the provable holder is promoted; the other two keep their located order, because a \
+             disproven pointer withholds credit rather than demoting (dig-node#466)"
+        );
+        assert_eq!(
+            located.len(),
+            3,
+            "a disproven claim is demoted on the redirect path, never withheld from it"
+        );
+    }
+
     /// A locator whose walk cannot be performed at all — the network is down, not the content absent.
     struct UnreachableLocator;
 

crates/dig-node-core/src/lib.rs

@@ -56,6 +56,7 @@ pub mod chat;
 pub mod dht_sampling;
 pub mod download;
 pub mod inbound_demand;
+pub mod mirror_bond;
 mod module_tier_tag;
 pub mod peer;
 pub mod rate_limit;