Merge #21142: fuzz: Add tx_pool fuzz target

faa9ef49d18da9223220afcc263ac91a74c291a6 fuzz: Add tx_pool fuzz targets (MarcoFalke)

Pull request description:

ACKs for top commit:
  AnthonyRonning:
    reACK faa9ef49d18da9223220afcc263ac91a74c291a6
  practicalswift:
    Tested ACK faa9ef49d18da9223220afcc263ac91a74c291a6
  glozow:
    code review ACK faa9ef49d18da9223220afcc263ac91a74c291a6, a bunch of comments but non blocking

Tree-SHA512: 8d404398faa46d8e7bf93060a2fe9afd5c0c2bd6e549ff6588d2f3dd1b912dff6c5416d5477c18edecc2e85b00db4fdf4790c3e6597a5149b0d40c9d5014d82f

1 files changed, 78 insertions, 0 deletions

diff --git a/src/test/fuzz/util.cpp b/src/test/fuzz/util.cpp
index 0a541e4186..93418ab1ff 100644
--- a/src/test/fuzz/util.cpp
+++ b/src/test/fuzz/util.cpp
@@ -3,8 +3,11 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <test/fuzz/util.h>
+#include <test/util/script.h>
+#include <util/rbf.h>
 #include <version.h>
 
+
 void FillNode(FuzzedDataProvider& fuzzed_data_provider, CNode& node, bool init_version) noexcept
 {
     const ServiceFlags remote_services = ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS);
@@ -23,3 +26,78 @@ void FillNode(FuzzedDataProvider& fuzzed_data_provider, CNode& node, bool init_v
         node.m_tx_relay->fRelayTxes = filter_txs;
     }
 }
+
+CMutableTransaction ConsumeTransaction(FuzzedDataProvider& fuzzed_data_provider, const std::optional<std::vector<uint256>>& prevout_txids, const int max_num_in, const int max_num_out) noexcept
+{
+    CMutableTransaction tx_mut;
+    const auto p2wsh_op_true = fuzzed_data_provider.ConsumeBool();
+    tx_mut.nVersion = fuzzed_data_provider.ConsumeBool() ?
+                          CTransaction::CURRENT_VERSION :
+                          fuzzed_data_provider.ConsumeIntegral<int32_t>();
+    tx_mut.nLockTime = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+    const auto num_in = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, max_num_in);
+    const auto num_out = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, max_num_out);
+    for (int i = 0; i < num_in; ++i) {
+        const auto& txid_prev = prevout_txids ?
+                                    PickValue(fuzzed_data_provider, *prevout_txids) :
+                                    ConsumeUInt256(fuzzed_data_provider);
+        const auto index_out = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, max_num_out);
+        const auto sequence = ConsumeSequence(fuzzed_data_provider);
+        const auto script_sig = p2wsh_op_true ? CScript{} : ConsumeScript(fuzzed_data_provider);
+        CScriptWitness script_wit;
+        if (p2wsh_op_true) {
+            script_wit.stack = std::vector<std::vector<uint8_t>>{WITNESS_STACK_ELEM_OP_TRUE};
+        } else {
+            script_wit = ConsumeScriptWitness(fuzzed_data_provider);
+        }
+        CTxIn in;
+        in.prevout = COutPoint{txid_prev, index_out};
+        in.nSequence = sequence;
+        in.scriptSig = script_sig;
+        in.scriptWitness = script_wit;
+
+        tx_mut.vin.push_back(in);
+    }
+    for (int i = 0; i < num_out; ++i) {
+        const auto amount = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-10, 50 * COIN + 10);
+        const auto script_pk = p2wsh_op_true ?
+                                   P2WSH_OP_TRUE :
+                                   ConsumeScript(fuzzed_data_provider, /* max_length */ 128, /* maybe_p2wsh */ true);
+        tx_mut.vout.emplace_back(amount, script_pk);
+    }
+    return tx_mut;
+}
+
+CScriptWitness ConsumeScriptWitness(FuzzedDataProvider& fuzzed_data_provider, const size_t max_stack_elem_size) noexcept
+{
+    CScriptWitness ret;
+    const auto n_elements = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, max_stack_elem_size);
+    for (size_t i = 0; i < n_elements; ++i) {
+        ret.stack.push_back(ConsumeRandomLengthByteVector(fuzzed_data_provider));
+    }
+    return ret;
+}
+
+CScript ConsumeScript(FuzzedDataProvider& fuzzed_data_provider, const size_t max_length, const bool maybe_p2wsh) noexcept
+{
+    const std::vector<uint8_t> b = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+    CScript r_script{b.begin(), b.end()};
+    if (maybe_p2wsh && fuzzed_data_provider.ConsumeBool()) {
+        uint256 script_hash;
+        CSHA256().Write(&r_script[0], r_script.size()).Finalize(script_hash.begin());
+        r_script.clear();
+        r_script << OP_0 << ToByteVector(script_hash);
+    }
+    return r_script;
+}
+
+uint32_t ConsumeSequence(FuzzedDataProvider& fuzzed_data_provider) noexcept
+{
+    return fuzzed_data_provider.ConsumeBool() ?
+               fuzzed_data_provider.PickValueInArray({
+                   CTxIn::SEQUENCE_FINAL,
+                   CTxIn::SEQUENCE_FINAL - 1,
+                   MAX_BIP125_RBF_SEQUENCE,
+               }) :
+               fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+}