From e6bc21b4613ef17690023c64d026e497fbc4fe3c Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@electriccoin.co>
Date: Mon, 18 Mar 2024 22:41:39 +0000
Subject: [PATCH] Add `WalletRead::is_seed_relevant_to_any_derived_accounts`

---
 zcash_client_backend/CHANGELOG.md    |  3 ++-
 zcash_client_backend/src/data_api.rs | 14 ++++++++++++
 zcash_client_sqlite/src/lib.rs       | 33 ++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/zcash_client_backend/CHANGELOG.md b/zcash_client_backend/CHANGELOG.md
index d4fc361df..1b82c0bb9 100644
--- a/zcash_client_backend/CHANGELOG.md
+++ b/zcash_client_backend/CHANGELOG.md
@@ -59,6 +59,8 @@ and this library adheres to Rust's notion of
   - Arguments to `ScannedBlock::from_parts` have changed.
   - Changes to the `WalletRead` trait:
     - Added `Account` associated type.
+    - Added `validate_seed` method.
+    - Added `is_seed_relevant_to_any_derived_accounts` method.
     - Added `get_account` method.
     - Added `get_derived_account` method.
     - `get_account_for_ufvk` now returns `Self::Account` instead of a bare
@@ -80,7 +82,6 @@ and this library adheres to Rust's notion of
     - `type OrchardShardStore`
     - `fn with_orchard_tree_mut`
     - `fn put_orchard_subtree_roots`
-  - Added method `WalletRead::validate_seed`
   - Removed `Error::AccountNotFound` variant.
   - `WalletSummary::new` now takes an additional `next_orchard_subtree_index`
     argument when the `orchard` feature flag is enabled.
diff --git a/zcash_client_backend/src/data_api.rs b/zcash_client_backend/src/data_api.rs
index 909aa6884..c27d9b137 100644
--- a/zcash_client_backend/src/data_api.rs
+++ b/zcash_client_backend/src/data_api.rs
@@ -740,6 +740,13 @@ pub trait WalletRead {
         seed: &SecretVec<u8>,
     ) -> Result<bool, Self::Error>;
 
+    /// Checks whether the given seed is relevant to any of the derived accounts (where
+    /// [`Account::source`] is [`AccountSource::Derived`]) in the wallet.
+    fn is_seed_relevant_to_any_derived_accounts(
+        &self,
+        seed: &SecretVec<u8>,
+    ) -> Result<bool, Self::Error>;
+
     /// Returns the account corresponding to a given [`UnifiedFullViewingKey`], if any.
     fn get_account_for_ufvk(
         &self,
@@ -1719,6 +1726,13 @@ pub mod testing {
             Ok(false)
         }
 
+        fn is_seed_relevant_to_any_derived_accounts(
+            &self,
+            _seed: &SecretVec<u8>,
+        ) -> Result<bool, Self::Error> {
+            Ok(false)
+        }
+
         fn get_account_for_ufvk(
             &self,
             _ufvk: &UnifiedFullViewingKey,
diff --git a/zcash_client_sqlite/src/lib.rs b/zcash_client_sqlite/src/lib.rs
index fb9ca3777..6b8fd2982 100644
--- a/zcash_client_sqlite/src/lib.rs
+++ b/zcash_client_sqlite/src/lib.rs
@@ -337,6 +337,39 @@ impl<C: Borrow<rusqlite::Connection>, P: consensus::Parameters> WalletRead for W
         }
     }
 
+    fn is_seed_relevant_to_any_derived_accounts(
+        &self,
+        seed: &SecretVec<u8>,
+    ) -> Result<bool, Self::Error> {
+        for account_id in self.get_account_ids()? {
+            let account = self.get_account(account_id)?.expect("account ID exists");
+
+            // If the account is imported, the seed _might_ be relevant, but the only
+            // way we could determine that is by brute-forcing the ZIP 32 account
+            // index space, which we're not going to do. The method name indicates to
+            // the caller that we only check derived accounts.
+            if let AccountSource::Derived {
+                seed_fingerprint,
+                account_index,
+            } = account.source()
+            {
+                if wallet::seed_matches_derived_account(
+                    &self.params,
+                    seed,
+                    &seed_fingerprint,
+                    account_index,
+                    &account.uivk(),
+                )? {
+                    // The seed is relevant to this account. No need to check any others.
+                    return Ok(true);
+                }
+            }
+        }
+
+        // The seed was not relevant to any of the accounts in the wallet.
+        Ok(false)
+    }
+
     fn get_account_for_ufvk(
         &self,
         ufvk: &UnifiedFullViewingKey,