simplicity: add fuzz target

src/Makefile.test.include

@@ -219,6 +219,7 @@ endif
 if ENABLE_FUZZ_BINARY
 test_fuzz_fuzz_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_fuzz_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_fuzz_CFLAGS = $(AM_CFLAGS) $(PIE_FLAGS)
 test_fuzz_fuzz_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_fuzz_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(PTHREAD_FLAGS) $(RUNTIME_LDFLAGS)
 test_fuzz_fuzz_SOURCES = \
@@ -312,6 +313,9 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/secp256k1_ecdsa_signature_parse_der_lax.cpp \
  test/fuzz/signature_checker.cpp \
  test/fuzz/signet.cpp \
+ test/fuzz/simplicity_compute_amr.c \
+ test/fuzz/simplicity.cpp \
+ test/fuzz/simplicity_tx.cpp \
  test/fuzz/socks5.cpp \
  test/fuzz/span.cpp \
  test/fuzz/spanparsing.cpp \

src/test/fuzz/simplicity.cpp

@@ -0,0 +1,226 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <cstdio>
+#include <primitives/transaction.h>
+extern "C" {
+#include <simplicity/cmr.h>
+#include <simplicity/elements/env.h>
+#include <simplicity/elements/exec.h>
+}
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <vector>
+
+static uint256 GENESIS_HASH;
+
+static CConfidentialAsset INPUT_ASSET_UNCONF{};
+static CConfidentialAsset INPUT_ASSET_CONF{};
+static CConfidentialValue INPUT_VALUE_UNCONF{};
+static CConfidentialValue INPUT_VALUE_CONF{};
+static CScript TAPROOT_SCRIPT_PUB_KEY{};
+static std::vector<unsigned char> TAPROOT_CONTROL{};
+static std::vector<unsigned char> TAPROOT_ANNEX(99, 0x50);
+//CMutableTransaction MTX_TEMPLATE{};
+
+// Defined in simplicity_compute_amr.c
+extern "C" {
+bool simplicity_computeAmr( simplicity_err* error, unsigned char* amr
+                          , const unsigned char* program, size_t program_len
+                          , const unsigned char* witness, size_t witness_len);
+}
+
+void initialize_simplicity()
+{
+    g_con_elementsmode = true;
+
+    GENESIS_HASH = uint256S("0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206");
+
+    INPUT_VALUE_UNCONF.SetToAmount(12345678);
+    INPUT_VALUE_CONF.vchCommitment = {
+        0x08,
+        0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+        0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+        0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+        0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+    };
+
+    INPUT_ASSET_UNCONF.vchCommitment = INPUT_VALUE_CONF.vchCommitment;
+    INPUT_ASSET_UNCONF.vchCommitment[0] = 0x01;
+    INPUT_ASSET_CONF.vchCommitment = INPUT_VALUE_CONF.vchCommitment;
+    INPUT_ASSET_CONF.vchCommitment[0] = 0x0a;
+
+    XOnlyPubKey intkey = XOnlyPubKey{uint256::ONE};
+    XOnlyPubKey extkey = XOnlyPubKey{uint256::ONE};
+    TAPROOT_SCRIPT_PUB_KEY = CScript{} << OP_1 << std::vector<unsigned char>(extkey.begin(), extkey.end());
+    // TODO have control block of nontrivial path length
+    TAPROOT_CONTROL.push_back(TAPROOT_LEAF_TAPSIMPLICITY | 1); // 1 is parity
+    TAPROOT_CONTROL.insert(TAPROOT_CONTROL.end(), intkey.begin(), intkey.end());
+}
+
+uint32_t read_u32(const unsigned char **buf) {
+    uint32_t ret;
+    memcpy(&ret, *buf, 4);
+    *buf += 4;
+    return le32toh(ret);
+}
+
+#define MAX_LEN (1024 * 1024)
+
+FUZZ_TARGET_INIT(simplicity, initialize_simplicity)
+{
+    const unsigned char *buf = buffer.data();
+
+    uint32_t budget;
+    uint32_t tx_data_len;
+    uint32_t prog_data_len;
+    uint32_t wit_data_len;
+
+    // 1. Sanitize and parse the buffer
+    if (buffer.size() < 8) {
+        return;
+    }
+    budget = read_u32(&buf);
+
+    tx_data_len = read_u32(&buf);
+    if (tx_data_len > MAX_LEN || buffer.size() < tx_data_len + 12) {
+        return;
+    }
+    const unsigned char *tx_data = buf;
+    buf += tx_data_len;
+
+    prog_data_len = read_u32(&buf);
+    if (prog_data_len > MAX_LEN || buffer.size() < tx_data_len + prog_data_len + 16) {
+        return;
+    }
+    const unsigned char *prog_data = buf;
+    buf += prog_data_len;
+
+    wit_data_len = read_u32(&buf);
+    if (wit_data_len > MAX_LEN || buffer.size() != tx_data_len + prog_data_len + wit_data_len + 16) {
+        return;
+    }
+    const unsigned char *wit_data = buf;
+
+    //printf("OK going\n");
+
+    // 2. Parse the transaction (the program and witness are just raw bytes)
+    CMutableTransaction mtx;
+    CDataStream txds{Span{tx_data, tx_data_len}, SER_NETWORK, INIT_PROTO_VERSION};
+    try {
+        txds >> mtx;
+        mtx.witness.vtxinwit.resize(mtx.vin.size());
+        mtx.witness.vtxoutwit.resize(mtx.vout.size());
+
+        // We use the first vin as a "random oracle" rather than reading more from
+        // the fuzzer, because we want our fuzz seeds to have as simple a structure
+        // as possible. This means we must reject 0-input transactions, which are
+        // invalid on-chain anyway.
+        if (mtx.vin.size() == 0) {
+            return;
+        }
+
+        // This is an assertion in the Simplicity interpreter. It is guaranteed
+        // to hold for anything on the network since (even if validatepegin is off)
+        // pegins are validated for well-formedness long before the script interpreter
+        // is invoked. But in this code we just call the interpreter directly without
+        // these checks.
+        for (unsigned i = 0; i < mtx.vin.size(); i++) {
+            if (mtx.vin[i].m_is_pegin && (mtx.witness.vtxinwit[i].m_pegin_witness.stack.size() < 4 || mtx.witness.vtxinwit[i].m_pegin_witness.stack[2].size() != 32)) {
+                return;
+            }
+        }
+    } catch (const std::ios_base::failure&) {
+        return;
+    }
+
+    // 2a. Pull the program and witness into vectors so they can be pushed onto the stack.
+    std::vector<unsigned char> prog_bytes;
+    std::vector<unsigned char> wit_bytes;
+    prog_bytes.assign(prog_data, prog_data + prog_data_len);
+    wit_bytes.assign(wit_data, wit_data + wit_data_len);
+
+    simplicity_err error;
+    unsigned char cmr[32];
+    unsigned char amr[32];
+    assert(simplicity_computeAmr(&error, amr, prog_data, prog_data_len, wit_data, wit_data_len));
+    assert(simplicity_computeCmr(&error, cmr, prog_data, prog_data_len));
+
+    // The remainder is just copy/pasted from the original fuzztest
+
+    // 3. Construct `nIn` and `spent_outs` array.
+    //
+    // Here we extract data from the first input's txid, since the fuzzer already
+    // produced that as a random string which has no other meaning. So to avoid
+    // complicating our seed encoding beyond "transaction then simplicity code"
+    // we just use it as a random source.
+    //
+    // We do skip the first byte since that has pegin/issuance flag in it and
+    // therefore already has semantic information.
+    size_t nIn = mtx.vin[0].prevout.hash.data()[1] % mtx.vin.size();
+    std::vector<CTxOut> spent_outs{};
+    for (unsigned int i = 0; i < mtx.vin.size(); i++) {
+        // Null asset or value would assert in the interpreter, and are impossible
+        // to hit in real transactions. Nonces are not included in the UTXO set and
+        // therefore don't matter.
+        CConfidentialValue value = i & 1 ? INPUT_VALUE_CONF : INPUT_VALUE_UNCONF;
+        CConfidentialAsset asset = i & 2 ? INPUT_ASSET_CONF : INPUT_ASSET_UNCONF;
+        CScript scriptPubKey;
+        if (i != nIn) {
+            // For scriptPubKeys we can use arbitrary scripts. We include the empty
+            // script even though in a real transaction this would be impossible,
+            // because it shouldn't break anything.
+            for (unsigned int j = 0; j < i; j++) {
+                scriptPubKey << OP_TRUE;
+            }
+        } else {
+            scriptPubKey = TAPROOT_SCRIPT_PUB_KEY;
+        }
+
+        spent_outs.push_back(CTxOut{asset, value, scriptPubKey});
+    }
+    assert(spent_outs.size() == mtx.vin.size());
+
+    // 4. Set up witness data
+    mtx.witness.vtxinwit[nIn].scriptWitness.stack.clear();
+    mtx.witness.vtxinwit[nIn].scriptWitness.stack.push_back(prog_bytes);
+    mtx.witness.vtxinwit[nIn].scriptWitness.stack.push_back(TAPROOT_CONTROL);
+    if (mtx.vin[0].prevout.hash.data()[2] & 1) {
+       mtx.witness.vtxinwit[nIn].scriptWitness.stack.push_back(TAPROOT_ANNEX);
+    }
+
+    // 5. Set up Simplicity environment and tx environment
+    rawTapEnv simplicityRawTap;
+    simplicityRawTap.controlBlock = TAPROOT_CONTROL.data();
+    simplicityRawTap.pathLen = (TAPROOT_CONTROL.size() - TAPROOT_CONTROL_BASE_SIZE) / TAPROOT_CONTROL_NODE_SIZE;
+    simplicityRawTap.scriptCMR = cmr;
+
+    PrecomputedTransactionData txdata{GENESIS_HASH};
+    std::vector<CTxOut> spent_outs_copy{spent_outs};
+    txdata.Init(mtx, std::move(spent_outs_copy));
+    assert(txdata.m_simplicity_tx_data != NULL);
+
+    // 4. Main test
+    unsigned char imr_out[32];
+    unsigned char *imr = mtx.vin[0].prevout.hash.data()[2] & 2 ? imr_out : NULL;
+
+    const transaction* tx = txdata.m_simplicity_tx_data;
+    tapEnv* taproot = simplicity_elements_mallocTapEnv(&simplicityRawTap);
+    simplicity_elements_execSimplicity(&error, imr, tx, nIn, taproot, GENESIS_HASH.data(), budget, amr, prog_bytes.data(), prog_bytes.size(), wit_bytes.data(), wit_bytes.size());
+
+    // 5. Secondary test -- try flipping a bunch of bits and check that this doesn't mess things up
+    for (size_t j = 0; j < 8 * prog_bytes.size(); j++) {
+        if (j > 32 && j % 23 != 0) continue; // skip most bits so this test doesn't overwhelm the fuzz time
+        prog_bytes.data()[j / 8] ^= (1 << (j % 8));
+        simplicity_elements_execSimplicity(&error, imr, tx, nIn, taproot, GENESIS_HASH.data(), budget, amr, prog_bytes.data(), prog_bytes.size(), wit_bytes.data(), wit_bytes.size());
+    }
+
+    // 6. Cleanup
+    free(taproot);
+}

src/test/fuzz/simplicity_compute_amr.c

@@ -0,0 +1,61 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <simplicity/cmr.h>
+#include <simplicity/dag.h>
+#include <simplicity/deserialize.h> // simplicity_decodeMallocDag
+#include <simplicity/limitations.h> // DAG_LEN_MAX
+#include <simplicity/simplicity_alloc.h> // simplicity_free
+#include <simplicity/typeInference.h> // simplicity_mallocTypeInference
+#include <simplicity/elements/env.h>
+#include <simplicity/elements/exec.h>
+
+// Copy of computeCmr used for AMR
+bool simplicity_computeAmr( simplicity_err* error, unsigned char* amr
+                          , const unsigned char* program, size_t program_len
+                          , const unsigned char* witness, size_t witness_len) {
+    simplicity_assert(NULL != error);
+    simplicity_assert(NULL != amr);
+    simplicity_assert(NULL != program || 0 == program_len);
+    simplicity_assert(NULL != witness || 0 == witness_len);
+
+    bitstream stream = initializeBitstream(program, program_len);
+    dag_node* dag = NULL;
+    combinator_counters census;
+    int_fast32_t dag_len = simplicity_decodeMallocDag(&dag, &census, &stream);
+    if (dag_len <= 0) {
+        simplicity_assert(dag_len < 0);
+        *error = (simplicity_err)dag_len;
+    } else {
+        simplicity_assert(NULL != dag);
+        simplicity_assert((uint_fast32_t)dag_len <= DAG_LEN_MAX);
+        *error = simplicity_closeBitstream(&stream);
+
+        type* type_dag = NULL;
+        if (IS_OK(*error)) {
+            *error = simplicity_mallocTypeInference(&type_dag, dag, (uint_fast32_t)dag_len, &census);
+        }
+        bitstream witness_stream;
+        if (IS_OK(*error)) {
+            witness_stream = initializeBitstream(witness, witness_len);
+            *error = simplicity_fillWitnessData(dag, type_dag, (uint_fast32_t)dag_len, &witness_stream);
+        }
+        if (IS_OK(*error)) {
+            *error = simplicity_closeBitstream(&witness_stream);
+            if (SIMPLICITY_ERR_BITSTREAM_TRAILING_BYTES == *error) *error = SIMPLICITY_ERR_WITNESS_TRAILING_BYTES;
+            if (SIMPLICITY_ERR_BITSTREAM_ILLEGAL_PADDING == *error) *error = SIMPLICITY_ERR_WITNESS_ILLEGAL_PADDING;
+        }
+        if (IS_OK(*error)) {
+            analyses *analysis = (analyses*) simplicity_malloc((size_t)dag_len * sizeof(analyses));
+            simplicity_assert(NULL != analysis);
+            simplicity_computeAnnotatedMerkleRoot(analysis, dag, type_dag, (uint_fast32_t)dag_len);
+            sha256_fromMidstate(amr, analysis[dag_len-1].annotatedMerkleRoot.s);
+            simplicity_free(analysis);
+        }
+        simplicity_free(type_dag);
+    }
+
+    simplicity_free(dag);
+    return IS_PERMANENT(*error);
+}