zcash_client_backend: Add a `purpose` modifier for imported accounts.

This moves the tracking of whether or not a spending key is expected to
be available for an imported account into the `AccountSource::Imported`
variant.

zcash_client_backend/CHANGELOG.md

@@ -30,6 +30,7 @@ funds to those addresses. See [ZIP 320](https://zips.z.cash/zip-0320) for detail
   - `DecryptedTransaction::mined_height`
   - `TransactionDataRequest`
   - `TransactionStatus`
+  - `AccountType`
 - `zcash_client_backend::fees`:
   - `EphemeralBalance`
   - `ChangeValue::shielded, is_ephemeral`
@@ -88,6 +89,9 @@ funds to those addresses. See [ZIP 320](https://zips.z.cash/zip-0320) for detail
     references to slices, with a corresponding change to `SentTransaction::new`.
   - `SentTransaction` takes an additional `target_height` argument, which is used
     to record the target height used in transaction generation.
+  - `AccountSource::Imported` is now a struct variant with a `purpose` field.
+  - The `Account` trait now defines a new `purpose` method with a default
+    implementation (which need not be overridden.)
 - `zcash_client_backend::data_api::fees`
   - When the "transparent-inputs" feature is enabled, `ChangeValue` can also
     represent an ephemeral transparent output in a proposal. Accordingly, the

zcash_client_backend/src/data_api.rs

@@ -321,6 +321,17 @@ impl AccountBalance {
     }
 }
 
+/// An enumeration used to control what information is tracked by the wallet for
+/// notes received by a given account.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum AccountPurpose {
+    /// For spending accounts, the wallet will track information needed to spend
+    /// received notes.
+    Spending,
+    /// For view-only accounts, the wallet will not track spend information.
+    ViewOnly,
+}
+
 /// The kinds of accounts supported by `zcash_client_backend`.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum AccountSource {
@@ -331,7 +342,7 @@ pub enum AccountSource {
     },
 
     /// An account imported from a viewing key.
-    Imported,
+    Imported { purpose: AccountPurpose },
 }
 
 /// A set of capabilities that a client account must provide.
@@ -343,6 +354,14 @@ pub trait Account<AccountId: Copy> {
     /// if applicable.
     fn source(&self) -> AccountSource;
 
+    /// Returns whether the account is a spending account or a view-only account.
+    fn purpose(&self) -> AccountPurpose {
+        match self.source() {
+            AccountSource::Derived { .. } => AccountPurpose::Spending,
+            AccountSource::Imported { purpose } => purpose,
+        }
+    }
+
     /// Returns the UFVK that the wallet backend has stored for the account, if any.
     ///
     /// Accounts for which this returns `None` cannot be used in wallet contexts, because
@@ -364,7 +383,9 @@ impl<A: Copy> Account<A> for (A, UnifiedFullViewingKey) {
     }
 
     fn source(&self) -> AccountSource {
-        AccountSource::Imported
+        AccountSource::Imported {
+            purpose: AccountPurpose::ViewOnly,
+        }
     }
 
     fn ufvk(&self) -> Option<&UnifiedFullViewingKey> {
@@ -383,7 +404,9 @@ impl<A: Copy> Account<A> for (A, UnifiedIncomingViewingKey) {
     }
 
     fn source(&self) -> AccountSource {
-        AccountSource::Imported
+        AccountSource::Imported {
+            purpose: AccountPurpose::ViewOnly,
+        }
     }
 
     fn ufvk(&self) -> Option<&UnifiedFullViewingKey> {
@@ -1816,7 +1839,7 @@ pub trait WalletWrite: WalletRead {
         &mut self,
         unified_key: &UnifiedFullViewingKey,
         birthday: &AccountBirthday,
-        spending_key_available: bool,
+        purpose: AccountPurpose,
     ) -> Result<Self::Account, Self::Error>;
 
     /// Generates and persists the next available diversified address, given the current
@@ -2027,10 +2050,10 @@ pub mod testing {
     use super::{
         chain::{ChainState, CommitmentTreeRoot},
         scanning::ScanRange,
-        AccountBirthday, BlockMetadata, DecryptedTransaction, InputSource, NullifierQuery,
+        AccountBirthday, AccountPurpose, BlockMetadata, DecryptedTransaction, InputSource,
-        ScannedBlock, SeedRelevance, SentTransaction, SpendableNotes, TransactionDataRequest,
+        NullifierQuery, ScannedBlock, SeedRelevance, SentTransaction, SpendableNotes,
-        TransactionStatus, WalletCommitmentTrees, WalletRead, WalletSummary, WalletWrite,
+        TransactionDataRequest, TransactionStatus, WalletCommitmentTrees, WalletRead,
-        SAPLING_SHARD_HEIGHT,
+        WalletSummary, WalletWrite, SAPLING_SHARD_HEIGHT,
     };
 
     #[cfg(feature = "transparent-inputs")]
@@ -2319,7 +2342,7 @@ pub mod testing {
             &mut self,
             _unified_key: &UnifiedFullViewingKey,
             _birthday: &AccountBirthday,
-            _spending_key_available: bool,
+            _purpose: AccountPurpose,
         ) -> Result<Self::Account, Self::Error> {
             todo!()
         }

zcash_client_sqlite/src/lib.rs

@@ -50,10 +50,10 @@ use zcash_client_backend::{
         self,
         chain::{BlockSource, ChainState, CommitmentTreeRoot},
         scanning::{ScanPriority, ScanRange},
-        Account, AccountBirthday, AccountSource, BlockMetadata, DecryptedTransaction, InputSource,
+        Account, AccountBirthday, AccountPurpose, AccountSource, BlockMetadata,
-        NullifierQuery, ScannedBlock, SeedRelevance, SentTransaction, SpendableNotes,
+        DecryptedTransaction, InputSource, NullifierQuery, ScannedBlock, SeedRelevance,
-        TransactionDataRequest, WalletCommitmentTrees, WalletRead, WalletSummary, WalletWrite,
+        SentTransaction, SpendableNotes, TransactionDataRequest, WalletCommitmentTrees, WalletRead,
-        SAPLING_SHARD_HEIGHT,
+        WalletSummary, WalletWrite, SAPLING_SHARD_HEIGHT,
     },
     keys::{
         AddressGenerationError, UnifiedAddressRequest, UnifiedFullViewingKey, UnifiedSpendingKey,
@@ -630,7 +630,6 @@ impl<P: consensus::Parameters> WalletWrite for WalletDb<rusqlite::Connection, P>
                     .map_err(|_| SqliteClientError::KeyDerivationError(account_index))?;
             let ufvk = usk.to_unified_full_viewing_key();
 
-            let spending_key_available = true;
             let account = wallet::add_account(
                 wdb.conn.0,
                 &wdb.params,
@@ -640,7 +639,6 @@ impl<P: consensus::Parameters> WalletWrite for WalletDb<rusqlite::Connection, P>
                 },
                 wallet::ViewingKey::Full(Box::new(ufvk)),
                 birthday,
-                spending_key_available,
             )?;
 
             Ok((account.id(), usk))
@@ -666,7 +664,6 @@ impl<P: consensus::Parameters> WalletWrite for WalletDb<rusqlite::Connection, P>
                     .map_err(|_| SqliteClientError::KeyDerivationError(account_index))?;
             let ufvk = usk.to_unified_full_viewing_key();
 
-            let spending_key_available = true;
             let account = wallet::add_account(
                 wdb.conn.0,
                 &wdb.params,
@@ -676,7 +673,6 @@ impl<P: consensus::Parameters> WalletWrite for WalletDb<rusqlite::Connection, P>
                 },
                 wallet::ViewingKey::Full(Box::new(ufvk)),
                 birthday,
-                spending_key_available,
             )?;
 
             Ok((account, usk))
@@ -687,16 +683,15 @@ impl<P: consensus::Parameters> WalletWrite for WalletDb<rusqlite::Connection, P>
         &mut self,
         ufvk: &UnifiedFullViewingKey,
         birthday: &AccountBirthday,
-        spending_key_available: bool,
+        purpose: AccountPurpose,
     ) -> Result<Self::Account, Self::Error> {
         self.transactionally(|wdb| {
             wallet::add_account(
                 wdb.conn.0,
                 &wdb.params,
-                AccountSource::Imported,
+                AccountSource::Imported { purpose },
                 wallet::ViewingKey::Full(Box::new(ufvk.to_owned())),
                 birthday,
-                spending_key_available,
             )
         })
     }
@@ -2029,7 +2024,8 @@ extern crate assert_matches;
 mod tests {
     use secrecy::{Secret, SecretVec};
     use zcash_client_backend::data_api::{
-        chain::ChainState, Account, AccountBirthday, AccountSource, WalletRead, WalletWrite,
+        chain::ChainState, Account, AccountBirthday, AccountPurpose, AccountSource, WalletRead,
+        WalletWrite,
     };
     use zcash_keys::keys::UnifiedSpendingKey;
     use zcash_primitives::block::BlockHash;
@@ -2177,14 +2173,19 @@ mod tests {
 
         let account = st
             .wallet_mut()
-            .import_account_ufvk(&ufvk, &birthday, true)
+            .import_account_ufvk(&ufvk, &birthday, AccountPurpose::Spending)
             .unwrap();
         assert_eq!(
             ufvk.encode(&st.wallet().params),
             account.ufvk().unwrap().encode(&st.wallet().params)
         );
 
-        assert_matches!(account.source(), AccountSource::Imported);
+        assert_matches!(
+            account.source(),
+            AccountSource::Imported {
+                purpose: AccountPurpose::Spending
+            }
+        );
     }
 
     #[test]
@@ -2202,7 +2203,7 @@ mod tests {
         let ufvk = seed_based_account.ufvk().unwrap();
 
         assert_matches!(
-            st.wallet_mut().import_account_ufvk(ufvk, &birthday, true),
+            st.wallet_mut().import_account_ufvk(ufvk, &birthday, AccountPurpose::Spending),
             Err(SqliteClientError::AccountCollision(id)) if id == seed_based.0);
     }
 

zcash_client_sqlite/src/wallet.rs

@@ -68,7 +68,7 @@ use incrementalmerkletree::{Marking, Retention};
 use rusqlite::{self, named_params, params, OptionalExtension};
 use secrecy::{ExposeSecret, SecretVec};
 use shardtree::{error::ShardTreeError, store::ShardStore, ShardTree};
-use zcash_client_backend::data_api::{TransactionDataRequest, TransactionStatus};
+use zcash_client_backend::data_api::{AccountPurpose, TransactionDataRequest, TransactionStatus};
 use zip32::fingerprint::SeedFingerprint;
 
 use std::collections::{HashMap, HashSet};
@@ -146,6 +146,7 @@ fn parse_account_source(
     account_kind: u32,
     hd_seed_fingerprint: Option<[u8; 32]>,
     hd_account_index: Option<u32>,
+    spending_key_available: bool,
 ) -> Result<AccountSource, SqliteClientError> {
     match (account_kind, hd_seed_fingerprint, hd_account_index) {
         (0, Some(seed_fp), Some(account_index)) => Ok(AccountSource::Derived {
@@ -156,7 +157,13 @@ fn parse_account_source(
                 )
             })?,
         }),
-        (1, None, None) => Ok(AccountSource::Imported),
+        (1, None, None) => Ok(AccountSource::Imported {
+            purpose: if spending_key_available {
+                AccountPurpose::Spending
+            } else {
+                AccountPurpose::ViewOnly
+            },
+        }),
         (0, None, None) | (1, Some(_), Some(_)) => Err(SqliteClientError::CorruptedData(
             "Wallet DB account_kind constraint violated".to_string(),
         )),
@@ -169,7 +176,7 @@ fn parse_account_source(
 fn account_kind_code(value: AccountSource) -> u32 {
     match value {
         AccountSource::Derived { .. } => 0,
-        AccountSource::Imported => 1,
+        AccountSource::Imported { .. } => 1,
     }
 }
 
@@ -349,14 +356,13 @@ pub(crate) fn add_account<P: consensus::Parameters>(
     kind: AccountSource,
     viewing_key: ViewingKey,
     birthday: &AccountBirthday,
-    spending_key_available: bool,
 ) -> Result<Account, SqliteClientError> {
-    let (hd_seed_fingerprint, hd_account_index) = match kind {
+    let (hd_seed_fingerprint, hd_account_index, spending_key_available) = match kind {
         AccountSource::Derived {
             seed_fingerprint,
             account_index,
-        } => (Some(seed_fingerprint), Some(account_index)),
+        } => (Some(seed_fingerprint), Some(account_index), true),
-        AccountSource::Imported => (None, None),
+        AccountSource::Imported { purpose } => (None, None, purpose == AccountPurpose::Spending),
     };
 
     let orchard_item = viewing_key
@@ -676,7 +682,7 @@ pub(crate) fn get_account_for_ufvk<P: consensus::Parameters>(
     let transparent_item: Option<Vec<u8>> = None;
 
     let mut stmt = conn.prepare(
-        "SELECT id, account_kind, hd_seed_fingerprint, hd_account_index, ufvk
+        "SELECT id, account_kind, hd_seed_fingerprint, hd_account_index, ufvk, has_spend_key
         FROM accounts
         WHERE orchard_fvk_item_cache = :orchard_fvk_item_cache
            OR sapling_fvk_item_cache = :sapling_fvk_item_cache
@@ -691,12 +697,17 @@ pub(crate) fn get_account_for_ufvk<P: consensus::Parameters>(
                 ":p2pkh_fvk_item_cache": transparent_item,
             ],
             |row| {
-                let account_id = row.get::<_, u32>(0).map(AccountId)?;
+                let account_id = row.get::<_, u32>("id").map(AccountId)?;
-                let kind = parse_account_source(row.get(1)?, row.get(2)?, row.get(3)?)?;
+                let kind = parse_account_source(
+                    row.get("account_kind")?,
+                    row.get("hd_seed_fingerprint")?,
+                    row.get("hd_account_index")?,
+                    row.get("has_spend_key")?,
+                )?;
 
                 // We looked up the account by FVK components, so the UFVK column must be
                 // non-null.
-                let ufvk_str: String = row.get(4)?;
+                let ufvk_str: String = row.get("ufvk")?;
                 let viewing_key = ViewingKey::Full(Box::new(
                     UnifiedFullViewingKey::decode(params, &ufvk_str).map_err(|e| {
                         SqliteClientError::CorruptedData(format!(
@@ -1501,7 +1512,7 @@ pub(crate) fn get_account<P: Parameters>(
 ) -> Result<Option<Account>, SqliteClientError> {
     let mut sql = conn.prepare_cached(
         r#"
-        SELECT account_kind, hd_seed_fingerprint, hd_account_index, ufvk, uivk
+        SELECT account_kind, hd_seed_fingerprint, hd_account_index, ufvk, uivk, has_spend_key
         FROM accounts
         WHERE id = :account_id
         "#,
@@ -1515,6 +1526,7 @@ pub(crate) fn get_account<P: Parameters>(
                 row.get("account_kind")?,
                 row.get("hd_seed_fingerprint")?,
                 row.get("hd_account_index")?,
+                row.get("has_spend_key")?,
             )?;
 
             let ufvk_str: Option<String> = row.get("ufvk")?;

zcash_client_sqlite/src/wallet/init/migrations/full_account_ids.rs

@@ -5,7 +5,10 @@ use rusqlite::{named_params, OptionalExtension, Transaction};
 use schemer_rusqlite::RusqliteMigration;
 use secrecy::{ExposeSecret, SecretVec};
 use uuid::Uuid;
-use zcash_client_backend::{data_api::AccountSource, keys::UnifiedSpendingKey};
+use zcash_client_backend::{
+    data_api::{AccountPurpose, AccountSource},
+    keys::UnifiedSpendingKey,
+};
 use zcash_keys::keys::UnifiedFullViewingKey;
 use zcash_primitives::consensus;
 use zip32::fingerprint::SeedFingerprint;
@@ -53,7 +56,11 @@ impl<P: consensus::Parameters> RusqliteMigration for Migration<P> {
             seed_fingerprint: SeedFingerprint::from_bytes([0; 32]),
             account_index: zip32::AccountId::ZERO,
         });
-        let account_kind_imported = account_kind_code(AccountSource::Imported);
+        let account_kind_imported = account_kind_code(AccountSource::Imported {
+            // the purpose here is irrelevant; we just use it to get the correct code
+            // for the account kind
+            purpose: AccountPurpose::ViewOnly,
+        });
         transaction.execute_batch(&format!(
             r#"
             CREATE TABLE accounts_new (

zcash_client_sqlite/src/wallet/transparent/ephemeral.rs

@@ -4,7 +4,8 @@ use std::ops::Range;
 
 use rusqlite::{named_params, OptionalExtension};
 
-use zcash_client_backend::{data_api::Account, wallet::TransparentAddressMetadata};
+use zcash_client_backend::wallet::TransparentAddressMetadata;
+use zcash_keys::keys::UnifiedFullViewingKey;
 use zcash_keys::{encoding::AddressCodec, keys::AddressGenerationError};
 use zcash_primitives::{
     legacy::{
@@ -15,11 +16,8 @@ use zcash_primitives::{
 };
 use zcash_protocol::consensus;
 
-use crate::TxRef;
 use crate::{
-    error::SqliteClientError,
+    error::SqliteClientError, wallet::GAP_LIMIT, AccountId, SqlTransaction, TxRef, WalletDb,
-    wallet::{get_account, GAP_LIMIT},
-    AccountId, SqlTransaction, WalletDb,
 };
 
 // Returns `TransparentAddressMetadata` in the ephemeral scope for the
@@ -118,12 +116,29 @@ pub(crate) fn get_ephemeral_ivk<P: consensus::Parameters>(
     params: &P,
     account_id: AccountId,
 ) -> Result<EphemeralIvk, SqliteClientError> {
-    Ok(get_account(conn, params, account_id)?
+    let ufvk = conn
+        .query_row(
+            "SELECT ufvk FROM accounts WHERE id = :account_id",
+            named_params![":account_id": account_id.0],
+            |row| {
+                let ufvk_str: Option<String> = row.get("ufvk")?;
+                Ok(ufvk_str.map(|s| {
+                    UnifiedFullViewingKey::decode(params, &s[..])
+                        .map_err(SqliteClientError::BadAccountData)
+                }))
+            },
+        )
+        .optional()?
         .ok_or(SqliteClientError::AccountUnknown)?
-        .ufvk()
+        .transpose()?;
+
+    let eivk = ufvk
+        .as_ref()
         .and_then(|ufvk| ufvk.transparent())
         .ok_or(SqliteClientError::UnknownZip32Derivation)?
-        .derive_ephemeral_ivk()?)
+        .derive_ephemeral_ivk()?;
+
+    Ok(eivk)
 }
 
 /// Returns a vector of ephemeral transparent addresses associated with the given