Legal holds, step 1: the hold itself

inbuxa:LegalHold get/set places a hold on accounts, groups, domains,
tenants or the whole server, with an optional date range. A hold's range
and scope can only widen, a released hold is read-only, and none is ever
deleted. Placing, changing and releasing each need a reason and are
audited (LH-1, LH-3, LH-10, AU-12).

Permissions 669-672 (see, place, widen or release, export held data)
go to server administrators only; the tenant ceiling always strips them,
as it does Impersonate (LH-13). Schema: Compliance > Legal Holds.

What a hold keeps comes next, through the undelete hooks.

Also moves the lock expiry helpers below the lock module's imports.

crates/features/src/hold/mod.rs

@@ -0,0 +1,429 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Coffey Labs
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+//! Legal holds (audit-hold-lock spec, LH-1 to LH-14).
+//!
+//! A hold names a case and what it covers: accounts, groups, domains,
+//! tenants or the whole server, optionally only items dated inside a range.
+//! While any active hold covers an item, nothing may destroy it. A hold is
+//! never deleted: releasing it keeps it, read-only, for the audit trail.
+//!
+//! Kept in the fork's subspace (`store::SUBSPACE_INBUXA`). Every key starts
+//! with `H`, then one byte for the kind:
+//!
+//! - `h` + hold id (u32): the hold, as JSON.
+//!
+//! Numbers are big-endian. There are few holds, so they're read whole.
+
+use serde::{Deserialize as SerdeDeserialize, Serialize as SerdeSerialize};
+use store::{
+    Deserialize, IterateParams, SUBSPACE_INBUXA, Serialize, Store, ValueKey,
+    write::{AnyClass, BatchBuilder, ValueClass, assert::AssertValue},
+};
+use trc::AddContext;
+
+const FEATURE: u8 = b'H';
+const KIND_HOLD: u8 = b'h';
+
+/// How many times creating a hold retries when another node took its id.
+const CREATE_ATTEMPTS: usize = 5;
+
+/// What a hold covers (LH-1, LH-2). Domains and tenants are resolved live,
+/// so an account added to one later is held too.
+#[derive(Debug, Clone, Default, PartialEq, Eq, SerdeSerialize, SerdeDeserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Scope {
+    /// Every account on the server.
+    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+    pub server: bool,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub accounts: Vec<u32>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub groups: Vec<u32>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub domains: Vec<u32>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub tenants: Vec<u32>,
+}
+
+impl Scope {
+    pub fn is_empty(&self) -> bool {
+        !self.server
+            && self.accounts.is_empty()
+            && self.groups.is_empty()
+            && self.domains.is_empty()
+            && self.tenants.is_empty()
+    }
+
+    /// Whether this scope covers everything `other` does, entry by entry.
+    /// A scope may only grow (LH-3's rule for ranges, applied to scope):
+    /// taking something out would free what it held.
+    pub fn contains(&self, other: &Scope) -> bool {
+        let all = |mine: &[u32], theirs: &[u32]| theirs.iter().all(|id| mine.contains(id));
+        (self.server || !other.server)
+            && all(&self.accounts, &other.accounts)
+            && all(&self.groups, &other.groups)
+            && all(&self.domains, &other.domains)
+            && all(&self.tenants, &other.tenants)
+    }
+
+    fn normalize(&mut self) {
+        for list in [
+            &mut self.accounts,
+            &mut self.groups,
+            &mut self.domains,
+            &mut self.tenants,
+        ] {
+            list.sort_unstable();
+            list.dedup();
+        }
+    }
+}
+
+/// When and why a hold was released (LH-10).
+#[derive(Debug, Clone, PartialEq, Eq, SerdeSerialize, SerdeDeserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Release {
+    pub at: u64,
+    pub by: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub by_id: Option<u32>,
+    pub reason: String,
+}
+
+/// A legal hold (LH-1).
+#[derive(Debug, Clone, PartialEq, Eq, SerdeSerialize, SerdeDeserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Hold {
+    pub id: u32,
+    /// The case name.
+    pub name: String,
+    /// A matter or ticket number.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub reference: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    pub scope: Scope,
+    /// Seconds since the epoch. Items dated before aren't held (LH-3).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub from: Option<u64>,
+    /// Seconds since the epoch. Items dated after aren't held (LH-3).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub to: Option<u64>,
+    pub placed_at: u64,
+    pub placed_by: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub placed_by_id: Option<u32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub released: Option<Release>,
+}
+
+/// Why a change to a hold is refused.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Refusal {
+    /// A released hold is read-only (LH-1).
+    Released,
+    /// The range may only widen (LH-3).
+    Narrowed,
+    /// The scope may only grow.
+    ScopeShrunk,
+    /// A hold has to cover something.
+    EmptyScope,
+    /// `from` after `to`.
+    Backwards,
+}
+
+impl Refusal {
+    pub fn describe(self) -> &'static str {
+        match self {
+            Refusal::Released => "A released hold can't be changed; place a new one instead.",
+            Refusal::Narrowed => {
+                "A hold's date range can only be widened. To hold less, release it and place a new hold."
+            }
+            Refusal::ScopeShrunk => {
+                "Nothing can be taken out of a hold's scope. To hold less, release it and place a new hold."
+            }
+            Refusal::EmptyScope => "A hold has to cover at least one account, group, domain or tenant, or the whole server.",
+            Refusal::Backwards => "The range starts after it ends.",
+        }
+    }
+}
+
+impl Hold {
+    pub fn is_active(&self) -> bool {
+        self.released.is_none()
+    }
+
+    /// Whether an item dated `at` (seconds) falls in the hold's range. With
+    /// no range, everything does (LH-3).
+    pub fn covers_date(&self, at: u64) -> bool {
+        self.from.is_none_or(|from| at >= from) && self.to.is_none_or(|to| at <= to)
+    }
+
+    /// Checks a new hold, and tidies its scope.
+    pub fn check_new(&mut self) -> Result<(), Refusal> {
+        self.scope.normalize();
+        if self.scope.is_empty() {
+            return Err(Refusal::EmptyScope);
+        }
+        if let (Some(from), Some(to)) = (self.from, self.to)
+            && from > to
+        {
+            return Err(Refusal::Backwards);
+        }
+        Ok(())
+    }
+
+    /// Checks that `next` is an allowed change of `self`: names and notes
+    /// may change, the range may only widen, the scope may only grow, and a
+    /// released hold may not change at all.
+    pub fn check_update(&self, next: &mut Hold) -> Result<(), Refusal> {
+        if !self.is_active() {
+            return Err(Refusal::Released);
+        }
+        next.check_new()?;
+        // An open end can't be closed, and a set end can only move outward
+        let from_ok = match (self.from, next.from) {
+            (None, Some(_)) => false,
+            (Some(old), Some(new)) => new <= old,
+            (_, None) => true,
+        };
+        let to_ok = match (self.to, next.to) {
+            (None, Some(_)) => false,
+            (Some(old), Some(new)) => new >= old,
+            (_, None) => true,
+        };
+        if !from_ok || !to_ok {
+            return Err(Refusal::Narrowed);
+        }
+        if !next.scope.contains(&self.scope) {
+            return Err(Refusal::ScopeShrunk);
+        }
+        Ok(())
+    }
+}
+
+struct Json<T>(T);
+
+impl<T: SerdeSerialize> Serialize for Json<T> {
+    fn serialize(&self) -> trc::Result<Vec<u8>> {
+        serde_json::to_vec(&self.0).map_err(|err| {
+            trc::StoreEvent::UnexpectedError
+                .into_err()
+                .details("Failed to serialize legal hold")
+                .reason(err)
+        })
+    }
+}
+
+impl<T: serde::de::DeserializeOwned + Sync + Send> Deserialize for Json<T> {
+    fn deserialize(bytes: &[u8]) -> trc::Result<Self> {
+        serde_json::from_slice(bytes).map(Json).map_err(|err| {
+            trc::StoreEvent::DataCorruption
+                .into_err()
+                .details("Invalid legal hold")
+                .reason(err)
+        })
+    }
+}
+
+fn class(id: u32) -> ValueClass {
+    let mut key = Vec::with_capacity(6);
+    key.push(FEATURE);
+    key.push(KIND_HOLD);
+    key.extend_from_slice(&id.to_be_bytes());
+    ValueClass::Any(AnyClass {
+        subspace: SUBSPACE_INBUXA,
+        key,
+    })
+}
+
+fn key(id: u32) -> ValueKey<ValueClass> {
+    ValueKey::from(class(id))
+}
+
+/// One hold, released or not.
+pub async fn get(data: &Store, id: u32) -> trc::Result<Option<Hold>> {
+    Ok(data
+        .get_value::<Json<Hold>>(key(id))
+        .await
+        .caused_by(trc::location!())?
+        .map(|Json(hold)| hold))
+}
+
+/// Every hold, released ones included, oldest first.
+pub async fn all(data: &Store) -> trc::Result<Vec<Hold>> {
+    let mut holds = Vec::new();
+    data.iterate(IterateParams::new(key(0), key(u32::MAX)), |_, value| {
+        if let Ok(Json(hold)) = Json::<Hold>::deserialize(value) {
+            holds.push(hold);
+        }
+        Ok(true)
+    })
+    .await
+    .caused_by(trc::location!())?;
+    Ok(holds)
+}
+
+/// The holds still in force.
+pub async fn active(data: &Store) -> trc::Result<Vec<Hold>> {
+    Ok(all(data).await?.into_iter().filter(Hold::is_active).collect())
+}
+
+/// Writes a new hold under the next free id, which it returns. Two nodes
+/// placing holds at once can't take the same id: the key must be absent.
+pub async fn create(data: &Store, hold: &Hold) -> trc::Result<u32> {
+    let mut attempt = 0;
+    loop {
+        attempt += 1;
+        let id = all(data).await?.iter().map(|h| h.id).max().unwrap_or(0) + 1;
+        let stored = Hold {
+            id,
+            ..hold.clone()
+        };
+        let mut batch = BatchBuilder::new();
+        batch.assert_value(class(id), AssertValue::None);
+        batch.set(class(id), Json(&stored).serialize()?);
+        match data.write(batch.build_all()).await {
+            Ok(_) => return Ok(id),
+            Err(err)
+                if attempt < CREATE_ATTEMPTS
+                    && matches!(
+                        err.as_ref(),
+                        trc::EventType::Store(trc::StoreEvent::AssertValueFailed)
+                    ) => {}
+            Err(err) => return Err(err.caused_by(trc::location!())),
+        }
+    }
+}
+
+/// Replaces a hold that `check_update` allowed.
+pub async fn update(data: &Store, hold: &Hold) -> trc::Result<()> {
+    let mut batch = BatchBuilder::new();
+    batch.set(class(hold.id), Json(hold).serialize()?);
+    data.write(batch.build_all())
+        .await
+        .caused_by(trc::location!())
+        .map(|_| ())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn hold(scope: Scope, from: Option<u64>, to: Option<u64>) -> Hold {
+        Hold {
+            id: 1,
+            name: "Matter 4411".into(),
+            reference: Some("4411".into()),
+            description: None,
+            scope,
+            from,
+            to,
+            placed_at: 10,
+            placed_by: "admin".into(),
+            placed_by_id: None,
+            released: None,
+        }
+    }
+
+    fn accounts(ids: &[u32]) -> Scope {
+        Scope {
+            accounts: ids.to_vec(),
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn a_hold_needs_a_scope_and_a_forward_range() {
+        assert_eq!(hold(Scope::default(), None, None).check_new(), Err(Refusal::EmptyScope));
+        assert_eq!(hold(accounts(&[2]), Some(20), Some(10)).check_new(), Err(Refusal::Backwards));
+        let mut ok = hold(accounts(&[3, 2, 3]), None, None);
+        assert_eq!(ok.check_new(), Ok(()));
+        assert_eq!(ok.scope.accounts, vec![2, 3], "sorted, once each");
+    }
+
+    #[test]
+    fn the_range_only_widens() {
+        let current = hold(accounts(&[2]), Some(100), Some(200));
+        let widened = |from, to| {
+            let mut next = hold(accounts(&[2]), from, to);
+            current.check_update(&mut next)
+        };
+        assert_eq!(widened(Some(50), Some(300)), Ok(()));
+        assert_eq!(widened(None, None), Ok(()), "opening both ends widens");
+        assert_eq!(widened(Some(150), Some(200)), Err(Refusal::Narrowed));
+        assert_eq!(widened(Some(100), Some(150)), Err(Refusal::Narrowed));
+
+        let open = hold(accounts(&[2]), None, None);
+        let mut closed = hold(accounts(&[2]), Some(1), None);
+        assert_eq!(open.check_update(&mut closed), Err(Refusal::Narrowed), "an open end stays open");
+    }
+
+    #[test]
+    fn the_scope_only_grows() {
+        let current = hold(
+            Scope {
+                accounts: vec![2],
+                domains: vec![7],
+                ..Default::default()
+            },
+            None,
+            None,
+        );
+        let mut grown = hold(
+            Scope {
+                accounts: vec![2, 3],
+                domains: vec![7],
+                tenants: vec![1],
+                ..Default::default()
+            },
+            None,
+            None,
+        );
+        assert_eq!(current.check_update(&mut grown), Ok(()));
+        let mut shrunk = hold(accounts(&[2, 3]), None, None);
+        assert_eq!(current.check_update(&mut shrunk), Err(Refusal::ScopeShrunk));
+
+        let server = hold(Scope { server: true, ..Default::default() }, None, None);
+        let mut less = hold(accounts(&[2]), None, None);
+        assert_eq!(server.check_update(&mut less), Err(Refusal::ScopeShrunk));
+    }
+
+    #[test]
+    fn a_released_hold_is_read_only() {
+        let mut released = hold(accounts(&[2]), None, None);
+        released.released = Some(Release {
+            at: 50,
+            by: "admin".into(),
+            by_id: None,
+            reason: "Settled".into(),
+        });
+        let mut next = released.clone();
+        next.name = "Renamed".into();
+        assert_eq!(released.check_update(&mut next), Err(Refusal::Released));
+        assert!(!released.is_active());
+    }
+
+    #[test]
+    fn dates_in_range() {
+        let whole = hold(accounts(&[2]), None, None);
+        assert!(whole.covers_date(0) && whole.covers_date(u64::MAX));
+        let ranged = hold(accounts(&[2]), Some(100), Some(200));
+        assert!(ranged.covers_date(100) && ranged.covers_date(200));
+        assert!(!ranged.covers_date(99) && !ranged.covers_date(201));
+        let open_ended = hold(accounts(&[2]), Some(100), None);
+        assert!(open_ended.covers_date(u64::MAX), "no `to` also catches mail still to come");
+    }
+
+    #[test]
+    fn stored_as_json() {
+        let current = hold(accounts(&[2]), Some(100), None);
+        let json = serde_json::to_string(&current).unwrap();
+        assert_eq!(serde_json::from_str::<Hold>(&json).unwrap(), current);
+        assert!(json.contains("\"scope\":{\"accounts\":[2]}"), "{json}");
+    }
+}

crates/features/src/lib.rs

@@ -21,6 +21,7 @@
 pub mod ai;
 pub mod audit;
 pub mod branding;
+pub mod hold;
 pub mod lock;
 pub mod masked_email;
 pub mod security;

crates/features/src/lock/mod.rs

@@ -27,6 +27,11 @@ use store::{
     write::{AnyClass, BatchBuilder, ValueClass},
 };
 use trc::AddContext;
+use types::{
+    acl::{Acl, AclGrant},
+    collection::Collection,
+};
+use utils::map::bitmap::Bitmap;
 
 /// Rung when a lock is written, so this node's expiry timer re-reads the
 /// `until` dates (AL-5): a delegation ends at its time, not at a sweep.
@@ -53,11 +58,6 @@ pub fn ended_between(locks: &[Lock], after: u64, now: u64) -> impl Iterator<Item
         })
         .map(|lock| lock.account_id)
 }
-use types::{
-    acl::{Acl, AclGrant},
-    collection::Collection,
-};
-use utils::map::bitmap::Bitmap;
 
 const FEATURE: u8 = b'K';
 const KIND_LOCK: u8 = b'l';