From c937ba5ae5443b39fa53945348c875ca844193b1 Mon Sep 17 00:00:00 2001
From: Larry Ruane <larry@z.cash>
Date: Fri, 3 Dec 2021 11:02:59 -0700
Subject: [PATCH] getblocktemplate: add NU5 commitments to new `defaultroots`
 section

- merkleroot
- authdataroot
- chainhistoryroot
- blockcommitmentshash
---
 qa/rpc-tests/getblocktemplate.py | 32 +++++++++++++++++++++-----------
 src/rpc/mining.cpp               | 29 ++++++++++++++++++++++++-----
 2 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/qa/rpc-tests/getblocktemplate.py b/qa/rpc-tests/getblocktemplate.py
index 223132da4..e7a8633ee 100755
--- a/qa/rpc-tests/getblocktemplate.py
+++ b/qa/rpc-tests/getblocktemplate.py
@@ -4,9 +4,15 @@
 # file COPYING or https://www.opensource.org/licenses/mit-license.php .
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, connect_nodes_bi, \
-    start_nodes
-
+from test_framework.util import (
+    assert_equal,
+    BLOSSOM_BRANCH_ID,
+    CANOPY_BRANCH_ID,
+    HEARTWOOD_BRANCH_ID,
+    NU5_BRANCH_ID,
+    nuparams,
+    start_nodes,
+)
 
 class GetBlockTemplateTest(BitcoinTestFramework):
     '''
@@ -15,12 +21,16 @@ class GetBlockTemplateTest(BitcoinTestFramework):
 
     def __init__(self):
         super().__init__()
-        self.num_nodes = 2
+        self.num_nodes = 1
         self.setup_clean_chain = True
 
     def setup_network(self, split=False):
-        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir)
-        connect_nodes_bi(self.nodes,0,1)
+        args = [nuparams(BLOSSOM_BRANCH_ID, 1),
+            nuparams(HEARTWOOD_BRANCH_ID, 1),
+            nuparams(CANOPY_BRANCH_ID, 1),
+            nuparams(NU5_BRANCH_ID, 1),
+        ]
+        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir, [args] * self.num_nodes)
         self.is_network_split=False
         self.sync_all()
 
@@ -51,15 +61,15 @@ class GetBlockTemplateTest(BitcoinTestFramework):
         # Test 5: General checks
         tmpl = node.getblocktemplate()
         assert_equal(16, len(tmpl['noncerange']))
+        # should be proposing height 2, since current tip is height 1
+        assert_equal(2, tmpl['height'])
 
         # Test 6: coinbasetxn checks
-        assert('foundersreward' in tmpl['coinbasetxn'])
         assert(tmpl['coinbasetxn']['required'])
 
-        # Test 7: hashFinalSaplingRoot checks
-        assert('finalsaplingroothash' in tmpl)
-        finalsaplingroothash = '3e49b5f954aa9d3545bc6c37744661eea48d7c34e3000d82b7f0010c30f4c2fb'
-        assert_equal(finalsaplingroothash, tmpl['finalsaplingroothash'])
+        # Test 7: blockcommitmentshash checks
+        assert('blockcommitmentshash' in tmpl)
+        assert('00' * 32 != tmpl['finalsaplingroothash'])
 
 if __name__ == '__main__':
     GetBlockTemplateTest().main()
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 76b6d35f8..7ed48d59a 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -428,6 +428,11 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
             "amounts, use 'getblocksubsidy HEIGHT' passing in the height returned\n"
             "by this API.\n"
 
+            "\nThe roots returned in 'defaultroots' are only valid if the block template is\n"
+            "used unmodified. If any part of the block template marked as 'mutable' in the\n"
+            "output is mutated, these roots may need to be recomputed. For more information\n"
+            "on the derivation process, see ZIP 244.\n"
+
             "\nArguments:\n"
             "1. \"jsonrequestobject\"       (string, optional) A json object in the following spec\n"
             "     {\n"
@@ -753,15 +758,29 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
         aMutable.push_back("prevblock");
     }
 
+    auto hashAuthDataRoot = pblock->BuildAuthDataMerkleTree();
+    std::string hashBlockCommitments_hex = DeriveBlockCommitmentsHash(
+            pblocktemplate->hashChainHistoryRoot,
+            hashAuthDataRoot).GetHex();
     UniValue result(UniValue::VOBJ);
     result.pushKV("capabilities", aCaps);
     result.pushKV("version", pblock->nVersion);
     result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
-    result.pushKV("blockcommitmentshash", pblock->hashBlockCommitments.GetHex());
-    // Deprecated; remove in a future release.
-    result.pushKV("lightclientroothash", pblock->hashBlockCommitments.GetHex());
-    // Deprecated; remove in a future release.
-    result.pushKV("finalsaplingroothash", pblock->hashBlockCommitments.GetHex());
+    // The following 3 are deprecated; remove in a future release.
+    result.pushKV("blockcommitmentshash", hashBlockCommitments_hex);
+    result.pushKV("lightclientroothash", hashBlockCommitments_hex);
+    result.pushKV("finalsaplingroothash", hashBlockCommitments_hex);
+    {
+        // These are items in the result object that are valid only if the
+        // block template returned by this RPC is used unmodified. Otherwise,
+        // these values must be recomputed.
+        UniValue defaults(UniValue::VOBJ);
+        defaults.pushKV("merkleroot", pblock->BuildMerkleTree().GetHex());
+        defaults.pushKV("authdataroot", hashAuthDataRoot.GetHex());
+        defaults.pushKV("chainhistoryroot", pblocktemplate->hashChainHistoryRoot.GetHex());
+        defaults.pushKV("blockcommitmentshash", hashBlockCommitments_hex);
+        result.pushKV("defaultroots", defaults);
+    }
     result.pushKV("transactions", transactions);
     if (coinbasetxn) {
         assert(txCoinbase.isObject());