Make listsinceblock refuse unknown block hash

Change suggested by Cory Fields <cory-nospam-@coryfields.com> who noticed
listsinceblock would ignore invalid block hashes causing it to return a
completely unfiltered list of transactions.

doc/release-notes.md

@@ -76,6 +76,9 @@ will only create hierarchical deterministic (HD) wallets.
 
 Low-level RPC changes
 ----------------------
+- `listsinceblock` will now throw an error if an unknown `blockhash` argument
+  value is passed, instead of returning a list of all wallet transactions since
+  the genesis block.
 - The "currentblocksize" value in getmininginfo has been removed.
 - The deprecated RPC `getinfo` was removed. It is recommended that the more specific RPCs are used:
   * `getblockchaininfo`

src/wallet/rpcwallet.cpp

@@ -1893,12 +1893,14 @@ UniValue listsinceblock(const JSONRPCRequest& request)
     int target_confirms = 1;
     isminefilter filter = ISMINE_SPENDABLE;
 
-    if (!request.params[0].isNull()) {
+    if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
         uint256 blockId;
 
         blockId.SetHex(request.params[0].get_str());
         BlockMap::iterator it = mapBlockIndex.find(blockId);
-        if (it != mapBlockIndex.end()) {
+        if (it == mapBlockIndex.end()) {
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+        }
         paltindex = pindex = it->second;
         if (chainActive[pindex->nHeight] != pindex) {
             // the block being asked for is a part of a deactivated chain;
@@ -1907,7 +1909,6 @@ UniValue listsinceblock(const JSONRPCRequest& request)
             pindex = chainActive.FindFork(pindex);
         }
     }
-    }
 
     if (!request.params[1].isNull()) {
         target_confirms = request.params[1].get_int();

test/functional/listsinceblock.py

@@ -5,7 +5,7 @@
 """Test the listsincelast RPC."""
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import assert_equal, assert_array_result, assert_raises_rpc_error
 
 class ListSinceBlockTest (BitcoinTestFramework):
     def set_test_params(self):
@@ -16,10 +16,43 @@ class ListSinceBlockTest (BitcoinTestFramework):
         self.nodes[2].generate(101)
         self.sync_all()
 
+        self.test_no_blockhash()
+        self.test_invalid_blockhash()
         self.test_reorg()
         self.test_double_spend()
         self.test_double_send()
 
+    def test_no_blockhash(self):
+        txid = self.nodes[2].sendtoaddress(self.nodes[0].getnewaddress(), 1)
+        blockhash, = self.nodes[2].generate(1)
+        self.sync_all()
+
+        txs = self.nodes[0].listtransactions()
+        assert_array_result(txs, {"txid": txid}, {
+            "category": "receive",
+            "amount": 1,
+            "blockhash": blockhash,
+            "confirmations": 1,
+        })
+        assert_equal(
+            self.nodes[0].listsinceblock(),
+            {"lastblock": blockhash,
+             "removed": [],
+             "transactions": txs})
+        assert_equal(
+            self.nodes[0].listsinceblock(""),
+            {"lastblock": blockhash,
+             "removed": [],
+             "transactions": txs})
+
+    def test_invalid_blockhash(self):
+        assert_raises_rpc_error(-5, "Block not found", self.nodes[0].listsinceblock,
+                                "42759cde25462784395a337460bde75f58e73d3f08bd31fdc3507cbac856a2c4")
+        assert_raises_rpc_error(-5, "Block not found", self.nodes[0].listsinceblock,
+                                "0000000000000000000000000000000000000000000000000000000000000000")
+        assert_raises_rpc_error(-5, "Block not found", self.nodes[0].listsinceblock,
+                                "invalid-hex")
+
     def test_reorg(self):
         '''
         `listsinceblock` did not behave correctly when handed a block that was