Merge remote-tracking branch 'origin/main' into fix/issue-358-check-created-overflow

# Conflicts:
#	crates/gitlawb-core/src/http_sig.rs

crates/gitlawb-core/src/cert.rs

@@ -5,6 +5,28 @@
 //!
 //! The schema is frozen at v1. All fields are mandatory for forward compatibility.
 //! Nodes that receive a certificate with an unknown version MUST reject it.
+//!
+//! ## Replay
+//!
+//! A certificate proves *who* asserted a ref update and *what* they asserted.
+//! It does not prove the assertion is fresh. [`RefUpdateBody::seq`] and
+//! [`RefUpdateBody::nonce`] are inside the signed bytes (see
+//! [`RefUpdateBody::to_signing_bytes`]), so a verifier can trust the values,
+//! but deciding whether a nonce is being reused or a `seq` is going backwards
+//! needs state.
+//!
+//! This crate is deliberately stateless — it is embedded in both nodes and
+//! clients — so replay is **not** enforced here and cannot be. Ownership of
+//! the check sits with the verifier that accepts and persists certificates,
+//! which must:
+//!
+//! - reject a `nonce` it has already accepted for the same `(repo, ref_name)`;
+//! - reject a `seq` that does not advance past the last accepted `seq` for
+//!   that `(repo, ref_name)`.
+//!
+//! Until such a verifier exists, replay of ref-update certificates is not
+//! enforced anywhere in this workspace. This contract exists so the first one
+//! inherits the requirement instead of re-deriving it.
 
 use std::collections::HashSet;
 
@@ -41,11 +63,19 @@ pub struct RefUpdateBody {
     pub from: String,
     /// The new commit hash (SHA-256 hex).
     pub to: String,
-    /// Monotonically increasing sequence number. Prevents replay.
+    /// Monotonically increasing sequence number, scoped to `(repo, ref_name)`.
+    ///
+    /// Signed, but not enforced by this crate: core holds no state. The
+    /// verifier that persists certificates must reject a `seq` that does not
+    /// advance for the same repo and ref. See the module docs on replay.
     pub seq: u64,
     /// RFC 3339 timestamp of this update.
     pub timestamp: DateTime<Utc>,
-    /// Random nonce for deduplication.
+    /// Random nonce, unique per certificate.
+    ///
+    /// Signed, but not enforced by this crate: core holds no state. The
+    /// verifier that persists certificates must reject a nonce it has already
+    /// accepted for the same repo and ref. See the module docs on replay.
     pub nonce: String,
 }
 
@@ -140,7 +170,16 @@ impl RefUpdateCert {
     ///
     /// Counts distinct signer DIDs, not signature entries: a repeated
     /// signature from the same maintainer counts once.
+    ///
+    /// `threshold` must be at least 1. Zero is rejected instead of being
+    /// treated as "no signatures required": a caller that derives the
+    /// threshold from configuration and gets 0 would otherwise accept any
+    /// certificate, whether its signatures verify or not.
     pub fn satisfies_threshold(&self, maintainers: &[Did], threshold: usize) -> Result<bool> {
+        if threshold == 0 {
+            return Err(Error::RefCert("threshold must be at least 1".to_string()));
+        }
+
         let valid = self.verify_all()?;
         let distinct_signers: HashSet<&Did> =
             valid.iter().filter(|d| maintainers.contains(d)).collect();
@@ -378,7 +417,7 @@ mod tests {
     }
 
     #[test]
-    fn threshold_zero_is_always_satisfied() {
+    fn threshold_zero_is_rejected() {
         let kp = Keypair::generate();
         let cert = RefUpdateCert::new(
             kp.did(),
@@ -389,6 +428,120 @@ mod tests {
             &kp,
         )
         .unwrap();
-        assert!(cert.satisfies_threshold(&[], 0).unwrap());
+
+        // Zero must never read as "no signatures required", even with an empty
+        // maintainer set.
+        let err = cert.satisfies_threshold(&[], 0).unwrap_err();
+        assert!(
+            err.to_string().contains("threshold must be at least 1"),
+            "zero must be refused as an invalid threshold"
+        );
+    }
+
+    /// The threshold is checked before any signature work, so a zero is
+    /// reported as a threshold error even when the certificate's signatures
+    /// are also invalid. Otherwise a broken certificate would let a caller
+    /// mistake the failure for a legitimate verification result.
+    #[test]
+    fn threshold_zero_is_rejected_before_signature_verification() {
+        let kp = Keypair::generate();
+        let other = Keypair::generate();
+        let mut cert = RefUpdateCert::new(
+            kp.did(),
+            "refs/heads/main".to_string(),
+            dummy_hash('0'),
+            dummy_hash('a'),
+            1,
+            &kp,
+        )
+        .unwrap();
+        cert.signatures[0].sig = other.sign_b64(b"unrelated bytes");
+
+        let err = cert.satisfies_threshold(&[kp.did()], 0).unwrap_err();
+        assert!(
+            err.to_string().contains("threshold must be at least 1"),
+            "the invalid threshold must win over the invalid signature"
+        );
+    }
+
+    /// `seq` and `nonce` are the verifier's replay inputs, so they have to be
+    /// inside the signed body; tapping either one must invalidate the
+    /// certificate rather than leave it verifying with different values.
+    #[test]
+    fn replay_fields_are_covered_by_the_signature() {
+        let kp = Keypair::generate();
+        let cert = RefUpdateCert::new(
+            kp.did(),
+            "refs/heads/main".to_string(),
+            dummy_hash('0'),
+            dummy_hash('a'),
+            7,
+            &kp,
+        )
+        .unwrap();
+        cert.verify_all().expect("baseline must verify");
+
+        let mut bumped = cert.clone();
+        bumped.body.seq = 8;
+        assert!(
+            matches!(bumped.verify_all(), Err(Error::SignatureInvalid)),
+            "changing seq must invalidate the signature"
+        );
+
+        let mut renamed = cert.clone();
+        renamed.body.nonce = "different-nonce".to_string();
+        assert!(
+            matches!(renamed.verify_all(), Err(Error::SignatureInvalid)),
+            "changing nonce must invalidate the signature"
+        );
+    }
+
+    /// A signature minted by a real key must not verify when the signer is
+    /// spelled in another multibase alphabet. Otherwise the same identity
+    /// would satisfy a maintainer allowlist under several DID strings.
+    ///
+    /// Base64url is deliberate: its 47-character method-id fits under the
+    /// pre-existing length bound, so this test reaches the canonical-prefix
+    /// rule and fails on the pre-fix code instead of being refused for length.
+    #[test]
+    fn verify_all_rejects_a_non_canonical_did_spelling() {
+        let kp = Keypair::generate();
+        let mut cert = RefUpdateCert::new(
+            kp.did(),
+            "refs/heads/main".to_string(),
+            dummy_hash('0'),
+            dummy_hash('a'),
+            1,
+            &kp,
+        )
+        .unwrap();
+
+        let mut prefixed = vec![0xed, 0x01];
+        prefixed.extend_from_slice(&kp.verifying_key().to_bytes());
+        cert.signatures[0].signer = format!(
+            "did:key:{}",
+            multibase::encode(multibase::Base::Base64Url, &prefixed)
+        )
+        .parse()
+        .expect("method is still `key`");
+
+        let err = cert
+            .verify_all()
+            .expect_err("a non-canonical did:key spelling must not resolve");
+        assert!(
+            err.to_string().contains("base58btc"),
+            "rejection must come from the canonical-prefix rule, not the length guard"
+        );
+        assert!(
+            !matches!(
+                cert.satisfies_threshold(&[cert.signatures[0].signer.clone()], 1),
+                Ok(true)
+            ),
+            "the alternate spelling must not satisfy a threshold"
+        );
+
+        // The canonical spelling of the same key is unaffected.
+        cert.signatures[0].signer = kp.did();
+        assert!(cert.satisfies_threshold(&[kp.did()], 1).unwrap());
     }
 }

crates/gitlawb-core/src/did.rs

@@ -20,6 +20,19 @@ use crate::{Error, Result};
 /// Value: 0xed01 encoded as a varint.
 const ED25519_MULTICODEC: &[u8] = &[0xed, 0x01];
 
+/// The only multibase prefix a `did:key` method-specific id may carry.
+///
+/// The DID:key spec encodes Ed25519 keys as base58btc, which is multibase
+/// `z`. `multibase::decode` happily accepts every other alphabet, and each
+/// spelling of the same key bytes would produce a distinct DID string while
+/// gates, allowlists, and database rows compare DIDs as strings — one
+/// identity would read as several. Rejecting the alternatives here keeps the
+/// mapping from `did:key` to key single-valued for every caller of
+/// [`Did::to_verifying_key`] (HTTP signatures, UCAN, ref certs, peer
+/// announces). `gitlawb-attest` enforces the same rule for attestation
+/// signers.
+const DID_KEY_MULTIBASE_PREFIX: char = 'z';
+
 /// A Decentralized Identifier.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 #[serde(transparent)]
@@ -71,8 +84,14 @@ impl Did {
 
     /// Resolve the Ed25519 verifying key from a `did:key`.
     ///
-    /// Returns `Err` if the DID is not a `did:key`, the key bytes are malformed,
-    /// or the key is a small-order (weak) point.
+    /// Only the canonical base58btc (`z`) spelling is accepted. Other
+    /// multibase encodings decode to the same key but spell a different DID
+    /// string, so accepting them would let one identity appear under several
+    /// identifiers to string-comparing gates and allowlists.
+    ///
+    /// Returns `Err` if the DID is not a `did:key`, uses a non-canonical
+    /// multibase prefix, the key bytes are invalid, or the key is a
+    /// small-order (weak) point.
     pub fn to_verifying_key(&self) -> Result<VerifyingKey> {
         if !self.is_did_key() {
             return Err(Error::InvalidDid(format!(
@@ -94,9 +113,27 @@ impl Did {
             ));
         }
 
-        let (_, bytes) =
+        // Cheap prefix gate before the decode, then the base check on what
+        // multibase actually parsed. The first keeps a clearly non-canonical id
+        // off the decoder. The second is belt-and-braces — multibase maps a
+        // leading `z` only to `Base58Btc` — but it states the requirement
+        // directly instead of relying on that mapping, and `gitlawb-attest`
+        // makes the same pair of checks.
+        if !self.method_id().starts_with(DID_KEY_MULTIBASE_PREFIX) {
+            return Err(Error::InvalidDid(
+                "did:key must use base58btc (z-prefix)".to_string(),
+            ));
+        }
+
+        let (base, bytes) =
             multibase::decode(self.method_id()).map_err(|e| Error::InvalidDid(e.to_string()))?;
 
+        if base != Base::Base58Btc {
+            return Err(Error::InvalidDid(
+                "did:key must use base58btc (z-prefix)".to_string(),
+            ));
+        }
+
         if !bytes.starts_with(ED25519_MULTICODEC) {
             return Err(Error::InvalidDid(
                 "not an ed25519 multicodec key".to_string(),
@@ -389,6 +426,124 @@ mod tests {
         did.to_verifying_key().expect("a real did:key must resolve");
     }
 
+    /// `multibase::decode` accepts every alphabet, so the same Ed25519 key can
+    /// be spelled as several `did:key` strings. Only base58btc is canonical;
+    /// the rest must be refused so one identity cannot appear as several to
+    /// gates and allowlists that compare DID strings.
+    #[test]
+    fn to_verifying_key_rejects_non_base58btc_multibase() {
+        use ed25519_dalek::SigningKey;
+        let signing = SigningKey::from_bytes(&[9u8; 32]);
+        let mut prefixed = ED25519_MULTICODEC.to_vec();
+        prefixed.extend_from_slice(&signing.verifying_key().to_bytes());
+
+        let canonical = Did::from_verifying_key(&signing.verifying_key());
+        assert_eq!(
+            canonical.to_verifying_key().unwrap().to_bytes(),
+            signing.verifying_key().to_bytes(),
+            "base58btc is the accepted spelling"
+        );
+
+        // These spellings fit inside the method-id bound, so they reach the
+        // canonical-prefix check and must be refused there.
+        for base in [Base::Base64Url, Base::Base32Lower] {
+            let alternative = format!("did:key:{}", multibase::encode(base, &prefixed));
+            let did: Did = alternative.parse().expect("method is still `key`");
+            assert_ne!(
+                did.as_str(),
+                canonical.as_str(),
+                "the same key must not compare equal under another spelling"
+            );
+
+            let err = did
+                .to_verifying_key()
+                .expect_err("non-canonical multibase must be refused");
+            assert!(
+                matches!(err, Error::InvalidDid(_)),
+                "must be an InvalidDid, got {err:?}"
+            );
+            assert!(
+                err.to_string().contains("base58btc"),
+                "the error must name the canonical encoding: {err}"
+            );
+        }
+
+        // A base16 spelling of the same key is longer than the method-id
+        // bound, so it is refused by the length guard before the prefix check.
+        // Either way it must not resolve.
+        for base in [Base::Base16Lower, Base::Base16Upper] {
+            let alternative = format!("did:key:{}", multibase::encode(base, &prefixed));
+            let did: Did = alternative.parse().expect("method is still `key`");
+            assert!(
+                matches!(did.to_verifying_key(), Err(Error::InvalidDid(_))),
+                "a base16 spelling of a real key must not resolve"
+            );
+        }
+    }
+
+    /// base58flickr (`Z`) is the non-bitcoin sibling alphabet. Its spelling of
+    /// a real key fits under the length bound, so it must be refused for the
+    /// prefix, not merely for its size.
+    #[test]
+    fn to_verifying_key_rejects_a_base58flickr_spelling() {
+        use ed25519_dalek::SigningKey;
+        let signing = SigningKey::from_bytes(&[11u8; 32]);
+        let mut prefixed = ED25519_MULTICODEC.to_vec();
+        prefixed.extend_from_slice(&signing.verifying_key().to_bytes());
+
+        let did: Did = format!(
+            "did:key:{}",
+            multibase::encode(Base::Base58Flickr, &prefixed)
+        )
+        .parse()
+        .expect("method is still `key`");
+
+        let err = did
+            .to_verifying_key()
+            .expect_err("base58flickr must be refused");
+        assert!(
+            err.to_string().contains("base58btc"),
+            "the error must name the canonical encoding: {err}"
+        );
+    }
+
+    /// An empty method-specific id must be refused by the prefix rule without
+    /// panicking on a missing first character.
+    #[test]
+    fn to_verifying_key_rejects_an_empty_method_id() {
+        let did: Did = "did:key:".parse().expect("method is still `key`");
+        let err = did
+            .to_verifying_key()
+            .expect_err("an empty method id must be refused");
+        assert!(
+            err.to_string().contains("base58btc"),
+            "the error must name the canonical encoding: {err}"
+        );
+    }
+
+    /// A canonical base58btc spelling is not enough on its own: the bytes must
+    /// also carry the ed25519-pub multicodec. This pins the check that stops a
+    /// key of another type from resolving as an Ed25519 key.
+    #[test]
+    fn to_verifying_key_rejects_base58btc_with_a_wrong_multicodec() {
+        use ed25519_dalek::SigningKey;
+        let signing = SigningKey::from_bytes(&[12u8; 32]);
+        let mut buf = vec![0x12, 0x00]; // sha2-256, not ed25519-pub
+        buf.extend_from_slice(&signing.verifying_key().to_bytes());
+
+        let did: Did = format!("did:key:{}", multibase::encode(Base::Base58Btc, &buf))
+            .parse()
+            .expect("method is still `key`");
+
+        let err = did
+            .to_verifying_key()
+            .expect_err("a non-ed25519 multicodec must be refused");
+        assert!(
+            err.to_string().contains("ed25519"),
+            "the error must name the expected multicodec: {err}"
+        );
+    }
+
     /// A `did:key` can encode a small-order (weak) Ed25519 point. Such a key
     /// satisfies the verification equation for any message and, converted to
     /// Montgomery form for X25519, yields the all-zero shared secret, so an

crates/gitlawb-core/src/http_sig.rs

@@ -566,6 +566,26 @@ mod tests {
         assert!(sig.check_created().is_ok());
     }
 
+    #[test]
+    fn extreme_created_timestamps_reject_without_wrapping() {
+        let kp = Keypair::generate();
+        let did = kp.did();
+        let parse = |created: i64| {
+            let sig_input =
+                format!(r#"sig1=("@method");keyid="{did}";alg="ed25519";created={created}"#);
+            HttpSignature::parse(&sig_input, "sig1=:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA:").unwrap()
+        };
+        // i64::MIN used to panic in debug (subtraction overflow) and wrap to a
+        // passing skew in release; now - 2^63 wrapped to i64::MIN, whose abs()
+        // wrapped back to itself and read as fresh. Both must reject.
+        for created in [i64::MIN, i64::MAX, Utc::now().timestamp() - i64::MAX] {
+            assert!(
+                parse(created).check_created().is_err(),
+                "created={created} must not pass the freshness gate"
+            );
+        }
+    }
+
     #[test]
     fn parse_error_missing_sig1_prefix() {
         let err = HttpSignature::parse(

crates/gitlawb-node/src/api/mod.rs

@@ -80,15 +80,20 @@ pub(crate) fn did_matches(a: &str, b: &str) -> bool {
     !ka.contains(':') && !kb.contains(':') && ka == kb
 }
 
+/// Client-facing denial shared by every repo-owner gate copy. `require_repo_owner`
+/// renders it as `AppError::Forbidden`; a handler that emits its own
+/// `(StatusCode, Json)` envelope instead of `AppError` (e.g.
+/// `api::tasks::create_task`) must use this constant too, so two copies of one
+/// gate cannot drift in observable output.
+pub(crate) const REPO_OWNER_ONLY_MESSAGE: &str = "only the repo owner can perform this action";
+
 /// 403 unless `caller` is the repo owner. Uses [`did_matches`] so the owner check
 /// and the author check (close policy) share one normalization.
 pub(crate) fn require_repo_owner(record: &RepoRecord, caller: &str) -> Result<()> {
     if did_matches(caller, &record.owner_did) {
         Ok(())
     } else {
-        Err(AppError::Forbidden(
-            "only the repo owner can perform this action".into(),
-        ))
+        Err(AppError::Forbidden(REPO_OWNER_ONLY_MESSAGE.into()))
     }
 }
 
@@ -242,6 +247,11 @@ mod authz_guard {
             (events, "list_repo_events", "authorize_repo_read("),
             // Bucket C — signer-self: the acting DID is matched/bound to auth.0
             (tasks, "create_task", "did_matches("),
+            // #496: create_task is signer-self AND owner-when-repo-scoped — a
+            // repo_id naming a hosted repo admits tasks only from its owner.
+            // Both halves are pinned: the did_matches row guards the signer
+            // binding, this one the repo-ownership gate.
+            (tasks, "create_task", "require_repo_owner("),
             (tasks, "claim_task", "did_matches("),
             (tasks, "complete_task", "did_matches("),
             (tasks, "fail_task", "did_matches("),
@@ -341,7 +351,11 @@ mod authz_guard {
             (
                 "create_task",
                 "createTask",
-                &["require_signer(ctx)?", "did_matches("],
+                &[
+                    "require_signer(ctx)?",
+                    "did_matches(",
+                    "require_repo_owner(",
+                ],
             ),
             (
                 "claim_task",

crates/gitlawb-node/src/api/tasks.rs

@@ -30,6 +30,33 @@ fn forbidden(msg: &str) -> (StatusCode, Json<Value>) {
     )
 }
 
+/// This module's error shape with an opaque body: the real error is logged
+/// server-side and never serialized (#250), matching the envelope
+/// `AppError::Db` renders. Also mirrors its status split: pool-class failures
+/// are a retryable 503 `db_unavailable`, everything else the opaque 500
+/// `db_error`, so a transient outage is not reported as permanent.
+fn db_error(e: anyhow::Error) -> (StatusCode, Json<Value>) {
+    tracing::error!(error = %format!("{e:#}"), "task database error");
+    if let Some(sql) = e.chain().find_map(|c| c.downcast_ref::<sqlx::Error>()) {
+        if crate::error::db_unavailable(sql) {
+            return (
+                StatusCode::SERVICE_UNAVAILABLE,
+                Json(json!({
+                    "error": crate::error::DB_UNAVAILABLE_CODE,
+                    "message": crate::error::DB_UNAVAILABLE_MESSAGE,
+                })),
+            );
+        }
+    }
+    (
+        StatusCode::INTERNAL_SERVER_ERROR,
+        Json(json!({
+            "error": "db_error",
+            "message": crate::error::DB_ERROR_MESSAGE,
+        })),
+    )
+}
+
 // ── Request / response types ──────────────────────────────────────────────────
 
 #[derive(Deserialize)]
@@ -101,6 +128,37 @@ pub async fn create_task(
     if !crate::api::did_matches(&auth.0, &body.delegator_did) {
         return Err(forbidden("delegator_did must be the authenticated signer"));
     }
+    // #496: a caller-supplied repo_id must name a repo the caller owns. Without
+    // this, any signed caller can plant a task — payload and UCAN included —
+    // under a foreign repo id, where the named assignee can claim it. Resolve
+    // the id against hosted repos: a hosted, non-quarantined repo admits tasks
+    // only from its owner (403 otherwise). An id naming no hosted repo
+    // (unknown, or quarantined — which is hidden as if it did not exist, so
+    // 403ing it would confirm a real id) is stored verbatim as an opaque
+    // label: this is a write gate and does not bind an unresolved id to a
+    // repo. Task reads are caller-independent on this base (the list endpoints
+    // are not repo-scoped), before and after this change. The 403-vs-201 split
+    // between a hosted repo id and an unknown one is itself a one-bit oracle —
+    // a stranger holding a private repo's id learns it is hosted here — but
+    // denying foreign repos requires drawing exactly that line, and repo ids
+    // already surface via the task list on this base. Repo-less tasks are
+    // unaffected.
+    if let Some(repo_id) = body.repo_id.as_deref() {
+        let record = state.db.get_repo_by_id(repo_id).await.map_err(db_error)?;
+        if let Some(record) = record {
+            let quarantined = state
+                .db
+                .is_repo_quarantined(&record.id)
+                .await
+                .map_err(db_error)?;
+            if !quarantined && crate::api::require_repo_owner(&record, &auth.0).is_err() {
+                // Same denial text the GraphQL copy relays from
+                // `require_repo_owner`, so the two copies of this gate do not
+                // disagree in observable output.
+                return Err(forbidden(crate::api::REPO_OWNER_ONLY_MESSAGE));
+            }
+        }
+    }
     let now = Utc::now().to_rfc3339();
     let task = AgentTask {
         id: Uuid::new_v4().to_string(),
@@ -117,12 +175,7 @@ pub async fn create_task(
         updated_at: now,
         deadline: body.deadline,
     };
-    state.db.create_task(&task).await.map_err(|e| {
-        (
-            StatusCode::INTERNAL_SERVER_ERROR,
-            Json(json!({ "error": e.to_string() })),
-        )
-    })?;
+    state.db.create_task(&task).await.map_err(db_error)?;
     Ok((StatusCode::CREATED, Json(task_to_json(&task))))
 }
 
@@ -297,3 +350,36 @@ pub async fn fail_task(
     });
     Ok(Json(task_to_json(&task)))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// The gate's DB helper must mirror `AppError::Db`: a pool-level failure is
+    /// the retryable 503 `db_unavailable`, a query fault the opaque 500.
+    #[test]
+    fn db_error_matches_app_error_status_split() {
+        let unavailable = db_error(anyhow::Error::from(sqlx::Error::PoolTimedOut));
+        assert_eq!(unavailable.0, StatusCode::SERVICE_UNAVAILABLE);
+        assert_eq!(unavailable.1 .0["error"], crate::error::DB_UNAVAILABLE_CODE);
+        assert_eq!(
+            unavailable.1 .0["message"],
+            crate::error::DB_UNAVAILABLE_MESSAGE
+        );
+
+        let query = db_error(anyhow::Error::from(sqlx::Error::Protocol(
+            "column \"machine_id\" does not exist".into(),
+        )));
+        assert_eq!(query.0, StatusCode::INTERNAL_SERVER_ERROR);
+        assert_eq!(query.1 .0["error"], "db_error");
+        assert_eq!(query.1 .0["message"], crate::error::DB_ERROR_MESSAGE);
+        assert!(!query.1 .0.to_string().contains("machine_id"));
+    }
+
+    /// `.context()` layers must not hide the sqlx error from the status split.
+    #[test]
+    fn db_error_sees_sqlx_through_context() {
+        let wrapped = anyhow::Error::from(sqlx::Error::PoolClosed).context("repo lookup failed");
+        assert_eq!(db_error(wrapped).0, StatusCode::SERVICE_UNAVAILABLE);
+    }
+}

crates/gitlawb-node/src/error.rs

@@ -101,7 +101,7 @@ pub const DB_ERROR_MESSAGE: &str = "a database error occurred";
 
 /// Connection-level sqlx failures that mean the database is unreachable right
 /// now (retryable, 503), as opposed to server-reported query errors.
-fn db_unavailable(e: &sqlx::Error) -> bool {
+pub(crate) fn db_unavailable(e: &sqlx::Error) -> bool {
     matches!(
         e,
         sqlx::Error::PoolTimedOut

crates/gitlawb-node/src/graphql/mutation.rs

@@ -36,6 +36,33 @@ impl MutationRoot {
         }
         let delegator_did = caller.to_string();
         let db = ctx.data_unchecked::<Arc<Db>>();
+        // #496: same write gate as the REST handler — a repo_id naming a
+        // hosted, non-quarantined repo admits tasks only from its owner, so a
+        // stranger cannot file under a foreign repo id. An id naming no hosted
+        // repo (unknown, or quarantined — hidden as if it did not exist) is
+        // stored verbatim as an opaque label; the gate does not bind an
+        // unresolved id to a repo. Task reads are caller-independent on this
+        // base (the tasks resolver is not repo-scoped), before and after this
+        // change. As in tasks.rs, the success-vs-denial split between a hosted
+        // repo id and an unknown one is itself a one-bit oracle — a stranger
+        // holding a private repo's id learns it is hosted here — but denying
+        // foreign repos requires drawing exactly that line.
+        if let Some(repo_id) = input.repo_id.as_deref() {
+            let record = db
+                .get_repo_by_id(repo_id)
+                .await
+                .map_err(crate::graphql::graphql_db_err)?;
+            if let Some(record) = record {
+                let quarantined = db
+                    .is_repo_quarantined(&record.id)
+                    .await
+                    .map_err(crate::graphql::graphql_db_err)?;
+                if !quarantined {
+                    crate::api::require_repo_owner(&record, caller)
+                        .map_err(crate::graphql::graphql_app_err)?;
+                }
+            }
+        }
         let now = Utc::now().to_rfc3339();
         let task = AgentTask {
             id: Uuid::new_v4().to_string(),
@@ -186,6 +213,22 @@ mod tests {
             .join("; ")
     }
 
+    /// The `id` scalar returned by a successful `createTask` mutation.
+    fn created_id(resp: &Response) -> String {
+        assert!(resp.errors.is_empty(), "graphql errors: {:?}", resp.errors);
+        let async_graphql::Value::Object(obj) = &resp.data else {
+            panic!("data not an object: {:?}", resp.data);
+        };
+        let async_graphql::Value::Object(task) = obj.get("createTask").expect("createTask key")
+        else {
+            panic!("createTask not an object");
+        };
+        let async_graphql::Value::String(id) = task.get("id").expect("id key") else {
+            panic!("id not a string");
+        };
+        id.clone()
+    }
+
     /// N2: every GraphQL mutation requires a verified signer and binds the acting
     /// DID to it. Unsigned is rejected; a signer other than the claimed actor is
     /// rejected; the matching signer passes the auth gate.
@@ -353,4 +396,181 @@ mod tests {
             errors(&resp)
         );
     }
+
+    /// #496 (GraphQL): createTask applies the same repo-ownership gate as the
+    /// REST handler — a stranger naming a hosted repo is rejected without
+    /// persisting anything, while the owner files. The quarantined and
+    /// unknown-id arms are pinned too, including that each accepted write
+    /// stores the supplied id verbatim, so this copy of the gate cannot regress
+    /// silently.
+    #[sqlx::test]
+    async fn create_task_rejects_foreign_repo_id(pool: PgPool) {
+        let state = crate::test_support::test_state(pool).await;
+        let owner = "did:key:zGQLTASKOWNERAAAAAAAAAAAAAAAAAAAAAAAAAA";
+        let stranger = "did:key:zGQLTASKSTRANGERBBBBBBBBBBBBBBBBBBBBBB";
+        let now = chrono::Utc::now();
+        let repo = crate::db::RepoRecord {
+            id: uuid::Uuid::new_v4().to_string(),
+            name: "gql-task-gate-repo".to_string(),
+            owner_did: owner.to_string(),
+            description: None,
+            is_public: true,
+            default_branch: "main".to_string(),
+            created_at: now,
+            updated_at: now,
+            disk_path: "/tmp/gql-task-gate-repo".to_string(),
+            forked_from: None,
+            machine_id: None,
+        };
+        state.db.create_repo(&repo).await.expect("seed repo");
+        let schema = state.graphql_schema.as_ref();
+
+        let q = |actor: &str| {
+            format!(
+                r#"mutation {{ createTask(delegatorDid: "{actor}", input: {{ kind: "build", capability: "repo:write", repoId: "{}" }}) {{ id }} }}"#,
+                repo.id
+            )
+        };
+
+        // Stranger signs as themselves (so the signer binding passes) but
+        // names the victim's repo → rejected by the ownership gate, leaking
+        // nothing about the repo.
+        let resp = schema
+            .execute(Request::new(q(stranger)).data(AuthenticatedDid(stranger.into())))
+            .await;
+        let errs = errors(&resp);
+        assert!(
+            errs.contains(crate::api::REPO_OWNER_ONLY_MESSAGE),
+            "a non-owner must not file under a foreign repo id (shared denial text): {errs}"
+        );
+
+        // The denial must not persist: no task row may carry the victim's
+        // repo id afterwards.
+        let stored = state
+            .db
+            .list_tasks(None, None, 50)
+            .await
+            .expect("list tasks");
+        assert!(
+            stored
+                .iter()
+                .all(|t| t.repo_id.as_deref() != Some(repo.id.as_str())),
+            "a denied write must not leave a task under the foreign repo id"
+        );
+
+        // The owner files under their own repo id.
+        let resp = schema
+            .execute(Request::new(q(owner)).data(AuthenticatedDid(owner.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "the owner should file against their repo: {}",
+            errors(&resp)
+        );
+
+        // Unknown repo ids stay accepted as opaque labels.
+        let q_unknown = format!(
+            r#"mutation {{ createTask(delegatorDid: "{stranger}", input: {{ kind: "build", capability: "repo:write", repoId: "no-such-repo-id" }}) {{ id }} }}"#
+        );
+        let resp = schema
+            .execute(Request::new(q_unknown).data(AuthenticatedDid(stranger.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "an id naming no hosted repo stays an opaque label: {}",
+            errors(&resp)
+        );
+        // Read back the row: the unresolved id must be stored verbatim, not
+        // dropped or rewritten to a repo it never named.
+        let stored = state
+            .db
+            .get_task(&created_id(&resp))
+            .await
+            .expect("get task")
+            .expect("task must be stored");
+        assert_eq!(
+            stored.repo_id.as_deref(),
+            Some("no-such-repo-id"),
+            "an unresolved id must be stored verbatim as a label"
+        );
+
+        // A quarantined repo id is treated as unknown (accepted, never a 403
+        // that would confirm the id names a real repo). This pins the
+        // `!quarantined` arm on this copy of the gate.
+        state
+            .db
+            .set_repo_quarantine(&repo.id, true)
+            .await
+            .expect("quarantine");
+        let resp = schema
+            .execute(Request::new(q(stranger)).data(AuthenticatedDid(stranger.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "a quarantined repo id must not 403 (existence oracle): {}",
+            errors(&resp)
+        );
+        // Read back the row: the quarantined id is stored verbatim as a label
+        // too, so the accepted write is not silently dropped.
+        let stored = state
+            .db
+            .get_task(&created_id(&resp))
+            .await
+            .expect("get task")
+            .expect("task must be stored");
+        assert_eq!(
+            stored.repo_id.as_deref(),
+            Some(repo.id.as_str()),
+            "a quarantined id must be stored verbatim as a label"
+        );
+    }
+
+    /// #496 (GraphQL): a repo-lookup fault in createTask's gate must stay
+    /// opaque. Dropping a column `get_repo_by_id` selects faults that lookup;
+    /// the resolver must return the fixed DB message and leak no schema text
+    /// (#250), as `create_task_db_error_message_is_opaque` pins for the
+    /// agent_tasks fault.
+    #[sqlx::test]
+    async fn create_task_gate_repo_lookup_fault_is_opaque(pool: PgPool) {
+        let state = crate::test_support::test_state(pool.clone()).await;
+        let owner = "did:key:zGQLTASKFAULTOWNERAAAAAAAAAAAAAAAAAAAAAAAA";
+        let now = chrono::Utc::now();
+        let repo = crate::db::RepoRecord {
+            id: uuid::Uuid::new_v4().to_string(),
+            name: "gql-task-gate-fault-repo".to_string(),
+            owner_did: owner.to_string(),
+            description: None,
+            is_public: true,
+            default_branch: "main".to_string(),
+            created_at: now,
+            updated_at: now,
+            disk_path: "/tmp/gql-task-gate-fault-repo".to_string(),
+            forked_from: None,
+            machine_id: None,
+        };
+        state.db.create_repo(&repo).await.expect("seed repo");
+
+        sqlx::query("ALTER TABLE repos DROP COLUMN machine_id")
+            .execute(&pool)
+            .await
+            .expect("drop machine_id");
+
+        let q = format!(
+            r#"mutation {{ createTask(delegatorDid: "{owner}", input: {{ kind: "build", capability: "repo:write", repoId: "{}" }}) {{ id }} }}"#,
+            repo.id
+        );
+        let resp = state
+            .graphql_schema
+            .execute(Request::new(&q).data(AuthenticatedDid(owner.into())))
+            .await;
+        let errs = errors(&resp);
+        assert!(
+            errs.contains(crate::graphql::GRAPHQL_DB_ERROR_MESSAGE),
+            "gate sqlx fault must be opaque: {errs}"
+        );
+        assert!(
+            !errs.contains("machine_id") && !errs.contains("column"),
+            "schema text leaked through the gate: {errs}"
+        );
+    }
 }

crates/gitlawb-node/src/test_support.rs

@@ -1036,6 +1036,345 @@ mod tests {
         );
     }
 
+    /// #496: create_task must reject a caller-supplied repo_id that names a
+    /// hosted repo the caller does not own. A stranger naming the victim's repo
+    /// gets 403, leaking nothing about the repo and persisting nothing; the
+    /// owner files (201). Repo-less tasks stay allowed; an id naming no hosted
+    /// repo (unknown, or quarantined, hidden as if it did not exist) is stored
+    /// verbatim as an opaque label, and the 403-vs-201 split between a hosted
+    /// id and an unknown one is itself a one-bit oracle. This is a write gate:
+    /// task reads are caller-independent and not repo-scoped on this base.
+    #[sqlx::test]
+    async fn create_task_rejects_foreign_repo_id(pool: PgPool) {
+        let owner = "did:key:zTASKREPOOWNERAAAAAAAAAAAAAAAAAAAAAAAAAA";
+        let stranger = "did:key:zTASKREPOSTRANGERBBBBBBBBBBBBBBBBBBBBBB";
+        let state = test_state(pool).await;
+        let repo = seed_repo(owner, "task-gate-repo");
+        state.db.create_repo(&repo).await.expect("seed repo");
+
+        let router = || {
+            Router::new()
+                .route(
+                    "/api/v1/tasks",
+                    axum::routing::post(crate::api::tasks::create_task),
+                )
+                .with_state(state.clone())
+        };
+        let post_as = |signer: &str, body: String| {
+            router().oneshot(signed_request_as(
+                signer,
+                Method::POST,
+                "/api/v1/tasks",
+                Body::from(body),
+            ))
+        };
+        let body_with = |signer: &str, repo_id: Option<&str>| {
+            let repo_field = repo_id
+                .map(|id| format!(r#","repo_id":"{id}""#))
+                .unwrap_or_default();
+            format!(
+                r#"{{"kind":"build","capability":"repo:write","delegator_did":"{signer}"{repo_field}}}"#
+            )
+        };
+        let created_id = |bytes: &[u8]| -> String {
+            let v: serde_json::Value = serde_json::from_slice(bytes).expect("task json");
+            v["id"].as_str().expect("task id").to_string()
+        };
+
+        // Stranger filing under the victim's repo id → exact 403.
+        let resp = post_as(stranger, body_with(stranger, Some(&repo.id)))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::FORBIDDEN,
+            "a non-owner must not file tasks against a foreign repo id"
+        );
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let text = String::from_utf8_lossy(&bytes);
+        assert!(
+            text.contains(r#""error":"forbidden""#),
+            "denial must keep the forbidden envelope: {text}"
+        );
+        assert!(
+            text.contains(crate::api::REPO_OWNER_ONLY_MESSAGE),
+            "denial must carry the shared owner-denial text (same as GraphQL): {text}"
+        );
+
+        // The denial must not persist: no task row may carry the victim's
+        // repo id afterwards — a 403 that still writes is the injection.
+        let stored = state
+            .db
+            .list_tasks(None, None, 50)
+            .await
+            .expect("list tasks");
+        assert!(
+            stored
+                .iter()
+                .all(|t| t.repo_id.as_deref() != Some(repo.id.as_str())),
+            "a denied write must not leave a task under the foreign repo id"
+        );
+
+        // Owner filing under their own repo id → 201.
+        let resp = post_as(owner, body_with(owner, Some(&repo.id)))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::CREATED,
+            "the owner must be able to file tasks against their repo"
+        );
+
+        // Repo-less task → 201 (unaffected).
+        let resp = post_as(stranger, body_with(stranger, None)).await.unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::CREATED,
+            "repo-less task creation must keep working"
+        );
+
+        // Unknown repo id → 201 as an opaque label.
+        let resp = post_as(stranger, body_with(stranger, Some("no-such-repo-id")))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::CREATED,
+            "an id naming no hosted repo stays an opaque label"
+        );
+        // Read back the row: the unresolved id must be stored verbatim, not
+        // dropped or rewritten to a repo it never named.
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let task = state
+            .db
+            .get_task(&created_id(&bytes))
+            .await
+            .expect("get task")
+            .expect("task must be stored");
+        assert_eq!(
+            task.repo_id.as_deref(),
+            Some("no-such-repo-id"),
+            "an unresolved id must be stored verbatim as a label"
+        );
+
+        // Quarantined repo id → treated as unknown (201), never a 403 that
+        // would confirm the id names a real repo.
+        state
+            .db
+            .set_repo_quarantine(&repo.id, true)
+            .await
+            .expect("quarantine");
+        let resp = post_as(stranger, body_with(stranger, Some(&repo.id)))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::CREATED,
+            "a quarantined repo id must not 403 (existence oracle)"
+        );
+        // Read back the row: the quarantined id is stored verbatim as a label
+        // too, so the accepted write is not silently dropped.
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let task = state
+            .db
+            .get_task(&created_id(&bytes))
+            .await
+            .expect("get task")
+            .expect("task must be stored");
+        assert_eq!(
+            task.repo_id.as_deref(),
+            Some(repo.id.as_str()),
+            "a quarantined id must be stored verbatim as a label"
+        );
+    }
+
+    /// #496 (REST): a repo-lookup fault in the create_task gate must render the
+    /// module's opaque `db_error` envelope, not the raw sqlx text. Dropping a
+    /// column `get_repo_by_id` selects faults that first lookup; the 500 body
+    /// stays fixed and names no column (#250/#226).
+    #[sqlx::test]
+    async fn create_task_gate_repo_lookup_fault_is_opaque(pool: PgPool) {
+        let owner = "did:key:zTASKFAULTOWNERAAAAAAAAAAAAAAAAAAAAAAAAA";
+        let state = test_state(pool.clone()).await;
+        let repo = seed_repo(owner, "task-gate-fault-repo");
+        state.db.create_repo(&repo).await.expect("seed repo");
+
+        let router = || {
+            Router::new()
+                .route(
+                    "/api/v1/tasks",
+                    axum::routing::post(crate::api::tasks::create_task),
+                )
+                .with_state(state.clone())
+        };
+        let body = format!(
+            r#"{{"kind":"build","capability":"repo:write","delegator_did":"{owner}","repo_id":"{}"}}"#,
+            repo.id
+        );
+
+        // Drop a column the lookup's SELECT names so get_repo_by_id faults.
+        sqlx::query("ALTER TABLE repos DROP COLUMN machine_id")
+            .execute(&pool)
+            .await
+            .expect("drop machine_id");
+
+        let resp = router()
+            .oneshot(signed_request_as(
+                owner,
+                Method::POST,
+                "/api/v1/tasks",
+                Body::from(body),
+            ))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::INTERNAL_SERVER_ERROR,
+            "a faulted repo lookup must be a 500"
+        );
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let text = String::from_utf8_lossy(&bytes);
+        assert!(
+            text.contains(r#""error":"db_error""#),
+            "gate DB fault must keep the opaque envelope: {text}"
+        );
+        assert!(
+            text.contains(crate::error::DB_ERROR_MESSAGE),
+            "gate DB fault must carry the fixed message: {text}"
+        );
+        assert!(
+            !text.contains("machine_id") && !text.contains("column"),
+            "schema text leaked through the gate: {text}"
+        );
+    }
+
+    /// #496 (REST): the gate's second lookup (`is_repo_quarantined`) runs through
+    /// the same opaque helper. Dropping the column only it selects leaves
+    /// `get_repo_by_id` succeeding, so this pins that second call site too.
+    #[sqlx::test]
+    async fn create_task_gate_quarantine_lookup_fault_is_opaque(pool: PgPool) {
+        let owner = "did:key:zTASKFAULT2OWNERAAAAAAAAAAAAAAAAAAAAAAAA";
+        let state = test_state(pool.clone()).await;
+        let repo = seed_repo(owner, "task-gate-fault2-repo");
+        state.db.create_repo(&repo).await.expect("seed repo");
+
+        let router = || {
+            Router::new()
+                .route(
+                    "/api/v1/tasks",
+                    axum::routing::post(crate::api::tasks::create_task),
+                )
+                .with_state(state.clone())
+        };
+        let body = format!(
+            r#"{{"kind":"build","capability":"repo:write","delegator_did":"{owner}","repo_id":"{}"}}"#,
+            repo.id
+        );
+
+        // `quarantined` is not in get_repo_by_id's SELECT, so that lookup still
+        // succeeds and the fault lands on is_repo_quarantined.
+        sqlx::query("ALTER TABLE repos DROP COLUMN quarantined")
+            .execute(&pool)
+            .await
+            .expect("drop quarantined");
+
+        let resp = router()
+            .oneshot(signed_request_as(
+                owner,
+                Method::POST,
+                "/api/v1/tasks",
+                Body::from(body),
+            ))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::INTERNAL_SERVER_ERROR,
+            "a faulted quarantine lookup must be a 500"
+        );
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let text = String::from_utf8_lossy(&bytes);
+        assert!(
+            text.contains(r#""error":"db_error""#),
+            "quarantine DB fault must keep the opaque envelope: {text}"
+        );
+        assert!(
+            text.contains(crate::error::DB_ERROR_MESSAGE),
+            "quarantine DB fault must carry the fixed message: {text}"
+        );
+        assert!(
+            !text.contains("quarantined") && !text.contains("column"),
+            "schema text leaked through the gate: {text}"
+        );
+    }
+
+    /// #496 (REST): the create_task INSERT goes through the same opaque helper,
+    /// so a write fault must not serialize sqlx text either. A repo-less task
+    /// reaches the INSERT without a gate lookup; dropping a column the INSERT
+    /// names faults it.
+    #[sqlx::test]
+    async fn create_task_insert_fault_is_opaque(pool: PgPool) {
+        let signer = "did:key:zTASKINSERTFAULTAAAAAAAAAAAAAAAAAAAAAAAA";
+        let state = test_state(pool.clone()).await;
+
+        let router = || {
+            Router::new()
+                .route(
+                    "/api/v1/tasks",
+                    axum::routing::post(crate::api::tasks::create_task),
+                )
+                .with_state(state.clone())
+        };
+        let body =
+            format!(r#"{{"kind":"build","capability":"repo:write","delegator_did":"{signer}"}}"#);
+
+        sqlx::query("ALTER TABLE agent_tasks DROP COLUMN status")
+            .execute(&pool)
+            .await
+            .expect("drop status");
+
+        let resp = router()
+            .oneshot(signed_request_as(
+                signer,
+                Method::POST,
+                "/api/v1/tasks",
+                Body::from(body),
+            ))
+            .await
+            .unwrap();
+        assert_eq!(
+            resp.status(),
+            StatusCode::INTERNAL_SERVER_ERROR,
+            "a faulted INSERT must be a 500"
+        );
+        let bytes = axum::body::to_bytes(resp.into_body(), usize::MAX)
+            .await
+            .unwrap();
+        let text = String::from_utf8_lossy(&bytes);
+        assert!(
+            text.contains(r#""error":"db_error""#),
+            "INSERT fault must keep the opaque envelope: {text}"
+        );
+        assert!(
+            text.contains(crate::error::DB_ERROR_MESSAGE),
+            "INSERT fault must carry the fixed message: {text}"
+        );
+        assert!(
+            !text.contains("status") && !text.contains("column"),
+            "schema text leaked through the INSERT: {text}"
+        );
+    }
+
     /// N3: get_tree gates on the REQUESTED subtree, not the repo root. A caller
     /// denied a withheld subtree is rejected there (404) but passes the gate on a
     /// non-withheld path (so the rejection is path-scoped, not repo-wide).