fix(node): gate GET /ipfs/{cid} tree objects so a withheld subtree's structure can't leak (#135)

.env.example

@@ -109,15 +109,73 @@ GITLAWB_MAX_PACK_BYTES=2147483648
 
 # Max seconds a served git upload-pack / receive-pack (clone / push) may run
 # before it is aborted with a 504. Bounds a hung git that would otherwise pin a
-# worker and, on push, the repo write lock. Does NOT cover the info/refs
-# advertisement or the withheld-blob path, which remain unbounded. Default 600.
+# worker and, on push, the repo write lock. Also bounds both info/refs
+# advertisements, the withheld-blob pack build, and the push-side candidate
+# discovery (rev-list / cat-file), all reaped via process-group teardown (#174).
+# Default 600.
 GITLAWB_GIT_SERVICE_TIMEOUT_SECS=600
 
+# Max seconds the storage-ACQUISITION phase of a served git op may run before the
+# request is shed with a 503, separate from the git-run timeout above. A
+# concurrency permit is taken before this phase and GITLAWB_GIT_SERVICE_TIMEOUT_SECS
+# only starts once git spawns, so without this a stalled backend (a hung Tigris
+# HEAD/GET, or a hung pg advisory-lock iteration on push) pins the permit and drains
+# the pool until every later request 503s. On expiry the permit is released
+# (fail-closed). Kept separate because acquisition and git execution are distinct
+# cost centers. Must be positive; set very large to effectively disable. Default 30.
+GITLAWB_GIT_ACQUIRE_TIMEOUT_SECS=30
+
+# Max concurrent git READ ops (upload-pack + the upload-pack info/refs
+# advertisement) served at once, a global pool separate from the push pool below.
+# The anon receive-pack info/refs advertisement has its OWN pool (see below), not
+# this one. Over-cap sheds a clean 503 + Retry-After. Anonymous reads draw from
+# here, so pair it with GITLAWB_MAX_CONCURRENT_READS_PER_CALLER (below) so one
+# caller cannot monopolize the pool. Default 128.
+GITLAWB_MAX_CONCURRENT_GIT_OPS=128
+
+# Max concurrent git-receive-pack (push) POST operations, in a pool separate from
+# the read pool (GITLAWB_MAX_CONCURRENT_GIT_OPS) so anonymous reads cannot shed an
+# authenticated push at admission. The anon receive-pack info/refs advertisement
+# runs in a SEPARATE pool of the same size (disjoint from this one), so an
+# advertisement flood cannot shed a push either. Over-cap sheds a 503 +
+# Retry-After. Default 32.
+GITLAWB_MAX_CONCURRENT_GIT_PUSHES=32
+
+# Max concurrent read ops (upload-pack + the upload-pack info/refs advertisement)
+# a single caller may hold, so one caller cannot monopolize the read pool. Keyed
+# on the resolved SOURCE IP, never the DID: a signature does not move a caller off
+# this cap. The source-IP key is only as granular as GITLAWB_TRUSTED_PROXY below:
+# left unset, a node behind an edge/NAT keys all callers on the edge IP and this
+# collapses to one global cap. Set GITLAWB_TRUSTED_PROXY for per-client keying; a
+# high-fanout caller (CI behind one NAT) then needs the operator to raise this.
+# Default 16.
+GITLAWB_MAX_CONCURRENT_READS_PER_CALLER=16
+
 # ── Push rate limiting (git-receive-pack flood brake) ─────────────────────
 # Max receive-pack requests (info/refs advertisement + push POST) per client
 # IP per hour. 0 disables. Default 600.
 GITLAWB_PUSH_RATE_LIMIT=600
 
+# ── /ipfs/{cid} visibility-walk admission (#174) ──────────────────────────
+# GET /ipfs/{cid} runs a per-repo full-history git walk in a blocking thread to
+# decide whether the caller may read a path-scoped blob. It is publicly reachable,
+# so it is bounded to keep a permissionless caller from fanning out unbounded
+# concurrent walks and exhausting blocking-pool threads + PIDs.
+# Max concurrent /ipfs walks across all callers (a pool of its own, disjoint from
+# the served-git pools). Over-cap sheds a 503. Default 32.
+GITLAWB_MAX_CONCURRENT_IPFS_WALKS=32
+# Max concurrent /ipfs walks a single SOURCE IP may hold (keyed like the git
+# per-caller caps via GITLAWB_TRUSTED_PROXY; reject-before-insert bounded map).
+# Default 4.
+GITLAWB_IPFS_WALK_PER_SOURCE=4
+# Max legacy (NULL-provenance) repos probed per single /ipfs request, bounding the
+# scan-fallback fan-out (git cat-file per candidate repo) for an anonymous caller. A
+# truncated scan sheds a retryable 503, never a false 404. Default 256.
+GITLAWB_IPFS_MAX_REPOS_WALKED=256
+# Max /ipfs/{cid} requests per client IP per hour (route flood brake, distinct
+# from the concurrency caps above). 0 disables. Default 600.
+GITLAWB_IPFS_RATE_LIMIT=600
+
 # ── Creation rate limiting (repo/agent/issue/PR flood brake) ──────────────
 # Max creation requests (POST /api/v1/repos, /api/register, fork, issues,
 # pulls) per client IP per hour, in addition to the per-DID limit. The per-DID

README.md

@@ -343,13 +343,20 @@ Important node settings:
 | `GITLAWB_REQUIRE_SIGNED_PEER_WRITES` | Require signed peer announce/sync writes. |
 | `GITLAWB_AUTO_SYNC` | Enable automatic sync from known peers. |
 | `GITLAWB_MAX_PACK_BYTES` | Max git pack body size for smart-HTTP routes. |
-| `GITLAWB_GIT_SERVICE_TIMEOUT_SECS` | Max seconds a served git upload-pack/receive-pack may run before it is aborted (504). Default 600. Does not bound `info/refs` or the withheld-blob path. |
+| `GITLAWB_GIT_SERVICE_TIMEOUT_SECS` | Max seconds a served git upload-pack, receive-pack, or `info/refs` advertisement may run before it is aborted (504). Default 600. Also bounds the withheld-blob classification walk (on both the upload-pack serve and receive-pack replication paths) and the push-side pin-candidate discovery (`rev-list` / `cat-file`), each reaped via process-group teardown at the deadline. |
+| `GITLAWB_GIT_ACQUIRE_TIMEOUT_SECS` | Max seconds the storage-acquisition phase (Tigris HEAD/GET, push advisory-lock) of a served git op may run before the request is shed with a 503, separate from the git-run timeout. The concurrency permit is released on expiry so a stalled backend cannot pin the pool. Default 30. |
+| `GITLAWB_MAX_CONCURRENT_IPFS_WALKS` | Max concurrent `GET /ipfs/{cid}` visibility walks across all callers (own pool, disjoint from the served-git pools); over-cap sheds 503. Default 32. |
+| `GITLAWB_IPFS_WALK_PER_SOURCE` | Max concurrent `/ipfs` walks a single source IP may hold. Default 4. |
+| `GITLAWB_IPFS_MAX_REPOS_WALKED` | Max legacy (NULL-provenance) repos probed per `/ipfs/{cid}` request, bounding the scan-fallback fan-out. A truncated scan returns a retryable 503, not a false 404. Default 256. |
+| `GITLAWB_IPFS_RATE_LIMIT` | Max `/ipfs/{cid}` requests per client IP per hour (route flood brake). 0 disables. Default 600. |
 | `GITLAWB_TIGRIS_BUCKET` | Optional S3/Tigris shared repo storage bucket. |
 | `GITLAWB_PINATA_JWT` | Optional Pinata/IPFS warm-storage pinning. |
 | `GITLAWB_IRYS_URL` | Optional Irys/Arweave permanent anchoring. |
 
 Production note: change the default Postgres password before exposing a node publicly.
 
+Legacy-pin window: releases before the CID-resolver work stored the provider CID (Kubo dag-pb / Pinata) as a pinned object's resolver key. The `/ipfs/{cid}` resolver now recomputes the raw-content CID from the object bytes and refuses to serve a key that does not match, so `GET /api/v1/ipfs/pins` can still advertise an unrepaired legacy CID that 404s. Such a row is repaired opportunistically the next time a push carries the object again (its key is rewritten to the raw CID, the old value kept in `legacy_provider_cid`), but git negotiation omits objects the node already has, so most legacy rows never re-enter a push delta. A deferred one-shot startup sweep, not this opportunistic path, is what fully retires the advertise-then-404 window. Rows whose object bytes are gone stay withheld.
+
 ---
 
 ## Optional node staking

crates/gitlawb-core/src/cid.rs

@@ -64,6 +64,19 @@ impl Cid {
     }
 }
 
+/// True when `s` parses as a CIDv1 with the raw codec — the exact shape
+/// [`Cid::from_git_object_bytes`] produces and the `/ipfs` resolver looks up.
+/// A legacy provider CID (Kubo dag-pb, Pinata CIDv0) parses to a different
+/// version or codec and returns `false`, marking it an opportunistic-repair
+/// candidate. Decidable from the string alone (no object bytes), so the pin path
+/// can gate the byte-read/recompute cost on it and leave non-legacy rows at the
+/// existing DB-only skip cost. An unparseable string is non-canonical (`false`).
+pub fn is_raw_cidv1(s: &str) -> bool {
+    s.parse::<CidGeneric<64>>()
+        .map(|c| c.version() == cid::Version::V1 && c.codec() == RAW)
+        .unwrap_or(false)
+}
+
 impl fmt::Display for Cid {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.0)
@@ -177,6 +190,38 @@ mod tests {
         assert!(result.is_err());
     }
 
+    #[test]
+    fn is_raw_cidv1_classifies_codec_from_string() {
+        // The canonical resolver key: CIDv1 + raw codec → not a repair candidate.
+        let raw = Cid::from_git_object_bytes(b"blob 5\0hello");
+        assert!(
+            is_raw_cidv1(raw.as_str()),
+            "from_git_object_bytes output is CIDv1/raw"
+        );
+
+        // A CIDv0 (Pinata dag-pb legacy shape) → repair candidate.
+        assert!(
+            !is_raw_cidv1("QmYwAPJzv5CZsnA625s3Xf2nemtYgPpHdWEz79ojWnPbdG"),
+            "a CIDv0 dag-pb value is a legacy-repair candidate"
+        );
+
+        // A CIDv1 with the dag-pb codec (the Kubo above-block-size root) over the
+        // same multihash → still a repair candidate (codec, not just version).
+        let parsed = raw.as_str().parse::<CidGeneric<64>>().unwrap();
+        const DAG_PB: u64 = 0x70;
+        let dagpb = CidGeneric::<64>::new_v1(DAG_PB, *parsed.hash()).to_string();
+        assert!(
+            !is_raw_cidv1(&dagpb),
+            "a CIDv1 dag-pb value is a legacy-repair candidate"
+        );
+
+        // Garbage is non-canonical.
+        assert!(
+            !is_raw_cidv1("not-a-cid"),
+            "an unparseable string is non-canonical"
+        );
+    }
+
     #[test]
     fn sha256_hex_of_empty_input_is_well_known() {
         // SHA-256("") is a fixed constant; verifies the hasher is wired correctly.