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Copy pathconfidential_validation.cpp
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436 lines (377 loc) · 16 KB
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#include <confidential_validation.h>
#include <issuance.h>
#include <pegins.h>
#include <script/sigcache.h>
#include <blind.h>
namespace {
static secp256k1_context *secp256k1_ctx_verify_amounts;
class CSecp256k1Init {
public:
CSecp256k1Init() {
assert(secp256k1_ctx_verify_amounts == NULL);
secp256k1_ctx_verify_amounts = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY | SECP256K1_CONTEXT_SIGN);
assert(secp256k1_ctx_verify_amounts != NULL);
}
~CSecp256k1Init() {
assert(secp256k1_ctx_verify_amounts != NULL);
secp256k1_context_destroy(secp256k1_ctx_verify_amounts);
secp256k1_ctx_verify_amounts = NULL;
}
};
static CSecp256k1Init instance_of_csecp256k1;
}
bool HasValidFee(const CTransaction& tx) {
CAmountMap totalFee;
for (unsigned int i = 0; i < tx.vout.size(); i++) {
CAmount fee = 0;
if (tx.vout[i].IsFee()) {
fee = tx.vout[i].nValue.GetAmount();
if (fee == 0 || !MoneyRange(fee))
return false;
totalFee[tx.vout[i].nAsset.GetAsset()] += fee;
if (!MoneyRange(totalFee)) {
return false;
}
}
}
return true;
}
CAmountMap GetFeeMap(const CTransaction& tx) {
CAmountMap fee;
for (const CTxOut& txout : tx.vout) {
if (txout.IsFee()) {
fee[txout.nAsset.GetAsset()] += txout.nValue.GetAmount();
}
}
return fee;
}
bool CRangeCheck::operator()() {
if (val->IsExplicit()) {
return true;
}
if (!CachingRangeProofChecker(store).VerifyRangeProof(rangeproof, val->vchCommitment, assetCommitment, scriptPubKey, secp256k1_ctx_verify_amounts)) {
error = SCRIPT_ERR_RANGEPROOF;
return false;
}
return true;
};
bool CBalanceCheck::operator()() {
if (!secp256k1_pedersen_verify_tally(secp256k1_ctx_verify_amounts, vpCommitsIn.data(), vpCommitsIn.size(), vpCommitsOut.data(), vpCommitsOut.size())) {
error = SCRIPT_ERR_PEDERSEN_TALLY;
return false;
}
return true;
}
bool CSurjectionCheck::operator()() {
return CachingSurjectionProofChecker(store).VerifySurjectionProof(proof, vTags, gen, secp256k1_ctx_verify_amounts, wtxid);
}
// Destroys the check in the case of no queue, or passes its ownership to the queue.
ScriptError QueueCheck(std::vector<CCheck*>* queue, CCheck* check) {
if (queue != NULL) {
queue->push_back(check);
return SCRIPT_ERR_OK;
}
bool success = (*check)();
ScriptError err = check->GetScriptError();
delete check;
return success ? SCRIPT_ERR_OK : err;
}
// Helper function for VerifyAmount(), not exported
static bool VerifyIssuanceAmount(secp256k1_pedersen_commitment& value_commit, secp256k1_generator& asset_gen,
const CAsset& asset, const CConfidentialValue& value, const std::vector<unsigned char>& rangeproof,
std::vector<CCheck*>* checks, const bool store_result)
{
// This is used to add in the explicit values
unsigned char explicit_blinds[32];
memset(explicit_blinds, 0, sizeof(explicit_blinds));
int ret;
ret = secp256k1_generator_generate(secp256k1_ctx_verify_amounts, &asset_gen, asset.begin());
assert(ret == 1);
// Build value commitment
if (value.IsExplicit()) {
if (!MoneyRange(value.GetAmount()) || value.GetAmount() == 0) {
return false;
}
if (!rangeproof.empty()) {
return false;
}
ret = secp256k1_pedersen_commit(secp256k1_ctx_verify_amounts, &value_commit, explicit_blinds, value.GetAmount(), &asset_gen);
// The explicit_blinds are all 0, and the amount is not 0. So secp256k1_pedersen_commit does not fail.
assert(ret == 1);
} else if (value.IsCommitment()) {
// Verify range proof
std::vector<unsigned char> vchAssetCommitment(CConfidentialAsset::nExplicitSize);
secp256k1_generator_serialize(secp256k1_ctx_verify_amounts, vchAssetCommitment.data(), &asset_gen);
if (QueueCheck(checks, new CRangeCheck(&value, rangeproof, vchAssetCommitment, CScript(), store_result)) != SCRIPT_ERR_OK) {
return false;
}
if (secp256k1_pedersen_commitment_parse(secp256k1_ctx_verify_amounts, &value_commit, value.vchCommitment.data()) != 1) {
return false;
}
} else {
return false;
}
return true;
}
bool VerifyAmounts(const std::vector<CTxOut>& inputs, const CTransaction& tx, std::vector<CCheck*>* checks, const bool store_result) {
assert(!tx.IsCoinBase());
assert(inputs.size() == tx.vin.size());
std::vector<secp256k1_pedersen_commitment> vData;
std::vector<secp256k1_pedersen_commitment *> vpCommitsIn, vpCommitsOut;
vData.reserve((tx.vin.size() + tx.vout.size() + GetNumIssuances(tx)));
secp256k1_pedersen_commitment *p = vData.data();
secp256k1_pedersen_commitment commit;
secp256k1_generator gen;
// This is used to add in the explicit values
unsigned char explicit_blinds[32] = {0};
int ret;
uint256 wtxid(tx.GetWitnessHash());
// This list is used to verify surjection proofs.
// Proofs must be constructed with the list being in
// order of input and non-null issuance pseudo-inputs, with
// input first, asset issuance second, reissuance token third.
std::vector<secp256k1_generator> target_generators;
target_generators.reserve(tx.vin.size() + GetNumIssuances(tx));
// Tally up value commitments, check balance
for (size_t i = 0; i < tx.vin.size(); ++i) {
const CConfidentialValue& val = inputs[i].nValue;
const CConfidentialAsset& asset = inputs[i].nAsset;
if (val.IsNull() || asset.IsNull())
return false;
if (asset.IsExplicit()) {
ret = secp256k1_generator_generate(secp256k1_ctx_verify_amounts, &gen, asset.GetAsset().begin());
assert(ret != 0);
}
else if (asset.IsCommitment()) {
if (secp256k1_generator_parse(secp256k1_ctx_verify_amounts, &gen, &asset.vchCommitment[0]) != 1)
return false;
}
else {
return false;
}
target_generators.push_back(gen);
if (val.IsExplicit()) {
if (!MoneyRange(val.GetAmount()))
return false;
// Fails if val.GetAmount() == 0
if (secp256k1_pedersen_commit(secp256k1_ctx_verify_amounts, &commit, explicit_blinds, val.GetAmount(), &gen) != 1)
return false;
} else if (val.IsCommitment()) {
if (secp256k1_pedersen_commitment_parse(secp256k1_ctx_verify_amounts, &commit, &val.vchCommitment[0]) != 1)
return false;
} else {
return false;
}
vData.push_back(commit);
vpCommitsIn.push_back(p);
p++;
// Each transaction input may have up to two "pseudo-inputs" to add to the LHS
// for (re)issuance and may require up to two rangeproof checks:
// blinded value of the new assets being made
// blinded value of the issuance tokens being made (only for initial issuance)
const CAssetIssuance& issuance = tx.vin[i].assetIssuance;
// No issuances to process, continue to next input
if (issuance.IsNull()) {
continue;
}
CAsset assetID;
CAsset assetTokenID;
// First construct the assets of the issuances and reissuance token
// These are calculated differently depending on if initial issuance or followup
// New issuance, compute the asset ids
if (issuance.assetBlindingNonce.IsNull()) {
uint256 entropy;
GenerateAssetEntropy(entropy, tx.vin[i].prevout, issuance.assetEntropy);
CalculateAsset(assetID, entropy);
// Null nAmount is considered explicit 0, so just check for commitment
CalculateReissuanceToken(assetTokenID, entropy, issuance.nAmount.IsCommitment());
} else {
// Re-issuance
// hashAssetIdentifier doubles as the entropy on reissuance
CalculateAsset(assetID, issuance.assetEntropy);
CalculateReissuanceToken(assetTokenID, issuance.assetEntropy, issuance.nAmount.IsCommitment());
// Must check that prevout is the blinded issuance token
// prevout's asset tag = assetTokenID + assetBlindingNonce
if (secp256k1_generator_generate_blinded(secp256k1_ctx_verify_amounts, &gen, assetTokenID.begin(), issuance.assetBlindingNonce.begin()) != 1) {
return false;
}
// Serialize the generator for direct comparison
unsigned char derived_generator[33];
secp256k1_generator_serialize(secp256k1_ctx_verify_amounts, derived_generator, &gen);
// Belt-and-suspenders: Check that asset commitment from issuance input is correct size
if (asset.vchCommitment.size() != sizeof(derived_generator)) {
return false;
}
// We have already checked the outputs' generator commitment for general validity, so directly compare serialized bytes
if (memcmp(asset.vchCommitment.data(), derived_generator, sizeof(derived_generator))) {
return false;
}
}
// Process issuance of asset
if (!issuance.nAmount.IsValid()) {
return false;
}
if (!issuance.nAmount.IsNull()) {
// Note: This check disallows issuances in transactions with *no* witness data.
// This can be relaxed in a future update as a HF by passing in an empty rangeproof
// to `VerifyIssuanceAmount` instead.
if (i >= tx.witness.vtxinwit.size()) {
return false;
}
if (!VerifyIssuanceAmount(commit, gen, assetID, issuance.nAmount, tx.witness.vtxinwit[i].vchIssuanceAmountRangeproof, checks, store_result)) {
return false;
}
target_generators.push_back(gen);
vData.push_back(commit);
vpCommitsIn.push_back(p);
p++;
}
// Process issuance of reissuance tokens
if (!issuance.nInflationKeys.IsValid()) {
return false;
}
if (!issuance.nInflationKeys.IsNull()) {
// Only initial issuance can have reissuance tokens
if (!issuance.assetBlindingNonce.IsNull()) {
return false;
}
// Note: This check disallows issuances in transactions with *no* witness data.
// This can be relaxed in a future update as a HF by passing in an empty rangeproof
// to `VerifyIssuanceAmount` instead.
if (i >= tx.witness.vtxinwit.size()) {
return false;
}
if (!VerifyIssuanceAmount(commit, gen, assetTokenID, issuance.nInflationKeys, tx.witness.vtxinwit[i].vchInflationKeysRangeproof, checks, store_result)) {
return false;
}
target_generators.push_back(gen);
vData.push_back(commit);
vpCommitsIn.push_back(p);
p++;
}
}
for (size_t i = 0; i < tx.vout.size(); ++i)
{
const CConfidentialValue& val = tx.vout[i].nValue;
const CConfidentialAsset& asset = tx.vout[i].nAsset;
if (!asset.IsValid())
return false;
if (!val.IsValid())
return false;
if (!tx.vout[i].nNonce.IsValid())
return false;
if (asset.IsExplicit()) {
ret = secp256k1_generator_generate(secp256k1_ctx_verify_amounts, &gen, asset.GetAsset().begin());
assert(ret != 0);
}
else if (asset.IsCommitment()) {
if (secp256k1_generator_parse(secp256k1_ctx_verify_amounts, &gen, &asset.vchCommitment[0]) != 1)
return false;
}
else {
return false;
}
if (val.IsExplicit()) {
if (!MoneyRange(val.GetAmount()))
return false;
if (val.GetAmount() == 0) {
if (tx.vout[i].scriptPubKey.IsUnspendable()) {
continue;
} else {
// No spendable 0-value outputs
// Reason: A spendable output of 0 reissuance tokens would allow reissuance without reissuance tokens.
return false;
}
}
ret = secp256k1_pedersen_commit(secp256k1_ctx_verify_amounts, &commit, explicit_blinds, val.GetAmount(), &gen);
// The explicit_blinds are all 0, and the amount is not 0. So secp256k1_pedersen_commit does not fail.
assert(ret == 1);
}
else if (val.IsCommitment()) {
if (secp256k1_pedersen_commitment_parse(secp256k1_ctx_verify_amounts, &commit, &val.vchCommitment[0]) != 1)
return false;
} else {
return false;
}
vData.push_back(commit);
vpCommitsOut.push_back(p);
p++;
}
// Check balance
if (QueueCheck(checks, new CBalanceCheck(vData, vpCommitsIn, vpCommitsOut)) != SCRIPT_ERR_OK) {
return false;
}
// Range proofs
for (size_t i = 0; i < tx.vout.size(); i++) {
const CConfidentialValue& val = tx.vout[i].nValue;
const CConfidentialAsset& asset = tx.vout[i].nAsset;
std::vector<unsigned char> vchAssetCommitment = asset.vchCommitment;
const CTxOutWitness* ptxoutwit = tx.witness.vtxoutwit.size() <= i? NULL: &tx.witness.vtxoutwit[i];
if (val.IsExplicit())
{
if (ptxoutwit && !ptxoutwit->vchRangeproof.empty())
return false;
continue;
}
if (asset.IsExplicit()) {
int ret = secp256k1_generator_generate(secp256k1_ctx_verify_amounts, &gen, asset.GetAsset().begin());
assert(ret != 0);
secp256k1_generator_serialize(secp256k1_ctx_verify_amounts, &vchAssetCommitment[0], &gen);
}
if (!ptxoutwit) {
return false;
}
if (QueueCheck(checks, new CRangeCheck(&val, ptxoutwit->vchRangeproof, vchAssetCommitment, tx.vout[i].scriptPubKey, store_result)) != SCRIPT_ERR_OK) {
return false;
}
}
// Surjection proofs
for (size_t i = 0; i < tx.vout.size(); i++)
{
const CConfidentialAsset& asset = tx.vout[i].nAsset;
const CTxOutWitness* ptxoutwit = tx.witness.vtxoutwit.size() <= i? NULL: &tx.witness.vtxoutwit[i];
// No need for surjection proof
if (asset.IsExplicit()) {
if (ptxoutwit && !ptxoutwit->vchSurjectionproof.empty()) {
return false;
}
continue;
}
if (!ptxoutwit)
return false;
if (secp256k1_generator_parse(secp256k1_ctx_verify_amounts, &gen, &asset.vchCommitment[0]) != 1)
return false;
secp256k1_surjectionproof proof;
if (secp256k1_surjectionproof_parse(secp256k1_ctx_verify_amounts, &proof, &ptxoutwit->vchSurjectionproof[0], ptxoutwit->vchSurjectionproof.size()) != 1)
return false;
if (QueueCheck(checks, new CSurjectionCheck(proof, target_generators, gen, wtxid, store_result)) != SCRIPT_ERR_OK) {
return false;
}
}
return true;
}
bool VerifyCoinbaseAmount(const CTransaction& tx, const CAmountMap& mapFees) {
assert(tx.IsCoinBase());
// Miner shouldn't be stuffing witness data
for (const auto& outwit : tx.witness.vtxoutwit) {
if (!outwit.IsNull()) {
return false;
}
}
CAmountMap remaining = mapFees;
for (unsigned int i = 0; i < tx.vout.size(); i++) {
const CTxOut& out = tx.vout[i];
if (!out.nValue.IsExplicit() || !out.nAsset.IsExplicit()) {
return false;
}
if (!MoneyRange(out.nValue.GetAmount())) {
return false;
}
if (g_con_elementsmode &&
out.nValue.GetAmount() == 0 && !out.scriptPubKey.IsUnspendable()) {
return false;
}
remaining[out.nAsset.GetAsset()] -= out.nValue.GetAmount();
}
return MoneyRange(remaining);
}
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