Merge bitcoin/bitcoin#26347: wallet: ensure the wallet is unlocked when needed for rescanning

6a5b348f2e test: test rescanning encrypted wallets (ishaanam)
493b813e17 wallet: ensure that the passphrase is not deleted from memory when being used to rescan (ishaanam)
66a86ebabb wallet: keep track of when the passphrase is needed when rescanning (ishaanam)

Pull request description:

  Wallet passphrases are needed to top up the keypool of encrypted wallets
  during a rescan. The following RPCs need the passphrase when rescanning:
      - `importdescriptors`
      - `rescanblockchain`

  The following RPCs use the information about whether or not the
  passphrase is being used to ensure that full rescans are able to
  take place (meaning the following RPCs should not be able to run
  if a rescan requiring the wallet to be unlocked  is taking place):
      - `walletlock`
      - `encryptwallet`
      - `walletpassphrasechange`

  `m_relock_mutex` is also introduced so that the passphrase is not
  deleted from memory when the timeout provided in
  `walletpassphrase` is up and the wallet is still rescanning.
  Fixes #25702, #11249

  Thanks to achow101 for coming up with the idea of using a new mutex to solve this issue and for answering related questions.

ACKs for top commit:
  achow101:
    ACK 6a5b348f2e
  hernanmarino:
    ACK 6a5b348f2e
  furszy:
    Tested ACK 6a5b348f

Tree-SHA512: 0b6db692714f6f94594fa47249f5ee24f85713bfa70ac295a7e84b9ca6c07dda65df7b47781a2dc73e5b603a8725343a2f864428ae20d3e126c5b4802abc4ab5

test/functional/wallet_importdescriptors.py

@@ -667,5 +667,33 @@ class ImportDescriptorsTest(BitcoinTestFramework):
                               success=True,
                               warnings=["Unknown output type, cannot set descriptor to active."])
 
+        self.log.info("Test importing a descriptor to an encrypted wallet")
+
+        descriptor = {"desc": descsum_create("pkh(" + xpriv + "/1h/*h)"),
+                              "timestamp": "now",
+                              "active": True,
+                              "range": [0,4000],
+                              "next_index": 4000}
+
+        self.nodes[0].createwallet("temp_wallet", blank=True, descriptors=True)
+        temp_wallet = self.nodes[0].get_wallet_rpc("temp_wallet")
+        temp_wallet.importdescriptors([descriptor])
+        self.generatetoaddress(self.nodes[0], COINBASE_MATURITY + 1, temp_wallet.getnewaddress())
+        self.generatetoaddress(self.nodes[0], COINBASE_MATURITY + 1, temp_wallet.getnewaddress())
+
+        self.nodes[0].createwallet("encrypted_wallet", blank=True, descriptors=True, passphrase="passphrase")
+        encrypted_wallet = self.nodes[0].get_wallet_rpc("encrypted_wallet")
+
+        descriptor["timestamp"] = 0
+        descriptor["next_index"] = 0
+
+        batch = []
+        batch.append(encrypted_wallet.walletpassphrase.get_request("passphrase", 3))
+        batch.append(encrypted_wallet.importdescriptors.get_request([descriptor]))
+
+        encrypted_wallet.batch(batch)
+
+        assert_equal(temp_wallet.getbalance(), encrypted_wallet.getbalance())
+
 if __name__ == '__main__':
     ImportDescriptorsTest().main()

test/functional/wallet_transactiontime_rescan.py

@@ -14,6 +14,9 @@ from test_framework.util import (
     assert_raises_rpc_error,
     set_node_times,
 )
+from test_framework.wallet_util import (
+    get_generate_key,
+)
 
 
 class TransactionTimeRescanTest(BitcoinTestFramework):
@@ -23,6 +26,10 @@ class TransactionTimeRescanTest(BitcoinTestFramework):
     def set_test_params(self):
         self.setup_clean_chain = False
         self.num_nodes = 3
+        self.extra_args = [["-keypool=400"],
+                           ["-keypool=400"],
+                           []
+                          ]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
@@ -167,6 +174,38 @@ class TransactionTimeRescanTest(BitcoinTestFramework):
         assert_raises_rpc_error(-8, "Invalid stop_height", restorewo_wallet.rescanblockchain, 1, -1)
         assert_raises_rpc_error(-8, "stop_height must be greater than start_height", restorewo_wallet.rescanblockchain, 20, 10)
 
+        self.log.info("Test `rescanblockchain` fails when wallet is encrypted and locked")
+        usernode.createwallet(wallet_name="enc_wallet", passphrase="passphrase")
+        enc_wallet = usernode.get_wallet_rpc("enc_wallet")
+        assert_raises_rpc_error(-13, "Error: Please enter the wallet passphrase with walletpassphrase first.", enc_wallet.rescanblockchain)
+
+        if not self.options.descriptors:
+            self.log.info("Test rescanning an encrypted wallet")
+            hd_seed = get_generate_key().privkey
+
+            usernode.createwallet(wallet_name="temp_wallet", blank=True, descriptors=False)
+            temp_wallet = usernode.get_wallet_rpc("temp_wallet")
+            temp_wallet.sethdseed(seed=hd_seed)
+
+            for i in range(399):
+                temp_wallet.getnewaddress()
+
+            self.generatetoaddress(usernode, COINBASE_MATURITY + 1, temp_wallet.getnewaddress())
+            self.generatetoaddress(usernode, COINBASE_MATURITY + 1, temp_wallet.getnewaddress())
+
+            minernode.createwallet("encrypted_wallet", blank=True, passphrase="passphrase", descriptors=False)
+            encrypted_wallet = minernode.get_wallet_rpc("encrypted_wallet")
+
+            encrypted_wallet.walletpassphrase("passphrase", 1)
+            encrypted_wallet.sethdseed(seed=hd_seed)
+
+            batch = []
+            batch.append(encrypted_wallet.walletpassphrase.get_request("passphrase", 3))
+            batch.append(encrypted_wallet.rescanblockchain.get_request())
+
+            encrypted_wallet.batch(batch)
+
+            assert_equal(encrypted_wallet.getbalance(), temp_wallet.getbalance())
 
 if __name__ == '__main__':
     TransactionTimeRescanTest().main()