Merge #13399: rpc: Add submitheader

fa091b001605c4481fb4eca415929a98d3478549 qa: Add tests for submitheader (MarcoFalke)
36b1b63f20cc718084971d2cadd04497a9b72634 rpc: Expose ProcessNewBlockHeaders (MarcoFalke)

Pull request description:

  This exposes `ProcessNewBlockHeaders` as an rpc called `submitheader`. This can be used to check for invalid block headers and submission of valid block headers via the rpc.

Tree-SHA512: a61e850470f15465f88e450609116df0a98d5d9afadf36b2033d820933d8b6a4012f9f2b3246319c08a0e511bef517f5d808cd0f44ffca91d10895a938004f0b

4 files changed, 128 insertions, 6 deletions

diff --git a/src/core_io.h b/src/core_io.h
index ee323a22ee..d53a45c0cb 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 class CBlock;
+class CBlockHeader;
 class CScript;
 class CTransaction;
 struct CMutableTransaction;
@@ -23,6 +24,7 @@ CScript ParseScript(const std::string& s);
 std::string ScriptToAsmStr(const CScript& script, const bool fAttemptSighashDecode = false);
 bool DecodeHexTx(CMutableTransaction& tx, const std::string& hex_tx, bool try_no_witness = false, bool try_witness = true);
 bool DecodeHexBlk(CBlock&, const std::string& strHexBlk);
+bool DecodeHexBlockHeader(CBlockHeader&, const std::string& hex_header);
 uint256 ParseHashStr(const std::string&, const std::string& strName);
 std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strName);
 bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error);
diff --git a/src/core_read.cpp b/src/core_read.cpp
index a5df45aba1..b02016c014 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -145,6 +145,20 @@ bool DecodeHexTx(CMutableTransaction& tx, const std::string& hex_tx, bool try_no
     return false;
 }
 
+bool DecodeHexBlockHeader(CBlockHeader& header, const std::string& hex_header)
+{
+    if (!IsHex(hex_header)) return false;
+
+    const std::vector<unsigned char> header_data{ParseHex(hex_header)};
+    CDataStream ser_header(header_data, SER_NETWORK, PROTOCOL_VERSION);
+    try {
+        ser_header >> header;
+    } catch (const std::exception&) {
+        return false;
+    }
+    return true;
+}
+
 bool DecodeHexBlk(CBlock& block, const std::string& strHexBlk)
 {
     if (!IsHex(strHexBlk))
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index e751587dc7..623b0bd86a 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -10,7 +10,6 @@
 #include <consensus/params.h>
 #include <consensus/validation.h>
 #include <core_io.h>
-#include <validation.h>
 #include <key_io.h>
 #include <miner.h>
 #include <net.h>
@@ -23,6 +22,7 @@
 #include <txmempool.h>
 #include <util.h>
 #include <utilstrencodings.h>
+#include <validation.h>
 #include <validationinterface.h>
 #include <warnings.h>
 
@@ -763,6 +763,42 @@ static UniValue submitblock(const JSONRPCRequest& request)
     return BIP22ValidationResult(sc.state);
 }
 
+static UniValue submitheader(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 1) {
+        throw std::runtime_error(
+            "submitheader \"hexdata\"\n"
+            "\nDecode the given hexdata as a header and submit it as a candidate chain tip if valid."
+            "\nThrows when the header is invalid.\n"
+            "\nArguments\n"
+            "1. \"hexdata\"        (string, required) the hex-encoded block header data\n"
+            "\nResult:\n"
+            "None"
+            "\nExamples:\n" +
+            HelpExampleCli("submitheader", "\"aabbcc\"") +
+            HelpExampleRpc("submitheader", "\"aabbcc\""));
+    }
+
+    CBlockHeader h;
+    if (!DecodeHexBlockHeader(h, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block header decode failed");
+    }
+    {
+        LOCK(cs_main);
+        if (!LookupBlockIndex(h.hashPrevBlock)) {
+            throw JSONRPCError(RPC_VERIFY_ERROR, "Must submit previous header (" + h.hashPrevBlock.GetHex() + ") first");
+        }
+    }
+
+    CValidationState state;
+    ProcessNewBlockHeaders({h}, state, Params(), /* ppindex */ nullptr, /* first_invalid */ nullptr);
+    if (state.IsValid()) return NullUniValue;
+    if (state.IsError()) {
+        throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
+    }
+    throw JSONRPCError(RPC_VERIFY_ERROR, state.GetRejectReason());
+}
+
 static UniValue estimatefee(const JSONRPCRequest& request)
 {
     throw JSONRPCError(RPC_METHOD_DEPRECATED, "estimatefee was removed in v0.17.\n"
@@ -940,6 +976,7 @@ static const CRPCCommand commands[] =
     { "mining",             "prioritisetransaction",  &prioritisetransaction,  {"txid","dummy","fee_delta"} },
     { "mining",             "getblocktemplate",       &getblocktemplate,       {"template_request"} },
     { "mining",             "submitblock",            &submitblock,            {"hexdata","dummy"} },
+    { "mining",             "submitheader",           &submitheader,           {"hexdata"} },
 
 
     { "generating",         "generatetoaddress",      &generatetoaddress,      {"nblocks","address","maxtries"} },
diff --git a/test/functional/mining_basic.py b/test/functional/mining_basic.py
index fa20a2d2f4..15b2d7f757 100755
--- a/test/functional/mining_basic.py
+++ b/test/functional/mining_basic.py
@@ -9,16 +9,23 @@
 - submitblock"""
 
 import copy
-from binascii import b2a_hex
 from decimal import Decimal
 
 from test_framework.blocktools import create_coinbase
-from test_framework.messages import CBlock
+from test_framework.messages import (
+    CBlock,
+    CBlockHeader,
+)
+from test_framework.mininode import (
+    P2PDataStore,
+)
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+    bytes_to_hex_str as b2x,
+)
 
-def b2x(b):
-    return b2a_hex(b).decode('ascii')
 
 def assert_template(node, block, expect, rehash=True):
     if rehash:
@@ -131,5 +138,67 @@ class MiningTest(BitcoinTestFramework):
         bad_block.hashPrevBlock = 123
         assert_template(node, bad_block, 'inconclusive-not-best-prevblk')
 
+        self.log.info('submitheader tests')
+        assert_raises_rpc_error(-22, 'Block header decode failed', lambda: node.submitheader(hexdata='xx' * 80))
+        assert_raises_rpc_error(-22, 'Block header decode failed', lambda: node.submitheader(hexdata='ff' * 78))
+        assert_raises_rpc_error(-25, 'Must submit previous header', lambda: node.submitheader(hexdata='ff' * 80))
+
+        block.solve()
+
+        def chain_tip(b_hash, *, status='headers-only', branchlen=1):
+            return {'hash': b_hash, 'height': 202, 'branchlen': branchlen, 'status': status}
+
+        assert chain_tip(block.hash) not in node.getchaintips()
+        node.submitheader(hexdata=b2x(block.serialize()))
+        assert chain_tip(block.hash) in node.getchaintips()
+        node.submitheader(hexdata=b2x(CBlockHeader(block).serialize()))  # Noop
+        assert chain_tip(block.hash) in node.getchaintips()
+
+        bad_block_root = copy.deepcopy(block)
+        bad_block_root.hashMerkleRoot += 2
+        bad_block_root.solve()
+        assert chain_tip(bad_block_root.hash) not in node.getchaintips()
+        node.submitheader(hexdata=b2x(CBlockHeader(bad_block_root).serialize()))
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+        # Should still reject invalid blocks, even if we have the header:
+        assert_equal(node.submitblock(hexdata=b2x(bad_block_root.serialize())), 'invalid')
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+        # We know the header for this invalid block, so should just return early without error:
+        node.submitheader(hexdata=b2x(CBlockHeader(bad_block_root).serialize()))
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+
+        bad_block_lock = copy.deepcopy(block)
+        bad_block_lock.vtx[0].nLockTime = 2**32 - 1
+        bad_block_lock.vtx[0].rehash()
+        bad_block_lock.hashMerkleRoot = bad_block_lock.calc_merkle_root()
+        bad_block_lock.solve()
+        assert_equal(node.submitblock(hexdata=b2x(bad_block_lock.serialize())), 'invalid')
+        # Build a "good" block on top of the submitted bad block
+        bad_block2 = copy.deepcopy(block)
+        bad_block2.hashPrevBlock = bad_block_lock.sha256
+        bad_block2.solve()
+        assert_raises_rpc_error(-25, 'bad-prevblk', lambda: node.submitheader(hexdata=b2x(CBlockHeader(bad_block2).serialize())))
+
+        # Should reject invalid header right away
+        bad_block_time = copy.deepcopy(block)
+        bad_block_time.nTime = 1
+        bad_block_time.solve()
+        assert_raises_rpc_error(-25, 'time-too-old', lambda: node.submitheader(hexdata=b2x(CBlockHeader(bad_block_time).serialize())))
+
+        # Should ask for the block from a p2p node, if they announce the header as well:
+        node.add_p2p_connection(P2PDataStore())
+        node.p2p.wait_for_getheaders(timeout=5)  # Drop the first getheaders
+        node.p2p.send_blocks_and_test(blocks=[block], rpc=node)
+        # Must be active now:
+        assert chain_tip(block.hash, status='active', branchlen=0) in node.getchaintips()
+
+        # Building a few blocks should give the same results
+        node.generate(10)
+        assert_raises_rpc_error(-25, 'time-too-old', lambda: node.submitheader(hexdata=b2x(CBlockHeader(bad_block_time).serialize())))
+        assert_raises_rpc_error(-25, 'bad-prevblk', lambda: node.submitheader(hexdata=b2x(CBlockHeader(bad_block2).serialize())))
+        node.submitheader(hexdata=b2x(CBlockHeader(block).serialize()))
+        node.submitheader(hexdata=b2x(CBlockHeader(bad_block_root).serialize()))
+
+
 if __name__ == '__main__':
     MiningTest().main()