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Improve comments for VerifyAmount()

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This commit is contained in:
Tim Ruffing 2018-05-23 15:21:16 +02:00
parent 42b62ac285
commit 05602edf6f
3 changed files with 13 additions and 6 deletions
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2
src/script/script.h
View file

@ -657,6 +657,8 @@ public:
* Returns whether the script is guaranteed to fail at execution, * Returns whether the script is guaranteed to fail at execution,
* regardless of the initial stack. This allows outputs to be pruned * regardless of the initial stack. This allows outputs to be pruned
* instantly when entering the UTXO set. This includes fee outputs. * instantly when entering the UTXO set. This includes fee outputs.
*
* This is consensus-critical because it is called by VerifyAmounts().
*/ */
bool IsUnspendable() const bool IsUnspendable() const
{ {

8
src/validation.cpp
View file

@ -793,6 +793,7 @@ bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::ve
if (!MoneyRange(val.GetAmount())) if (!MoneyRange(val.GetAmount()))
return false; return false;
// Fails if val.GetAmount() == 0
if (secp256k1_pedersen_commit(secp256k1_ctx_verify_amounts, &commit, explBlinds, val.GetAmount(), &gen) != 1) if (secp256k1_pedersen_commit(secp256k1_ctx_verify_amounts, &commit, explBlinds, val.GetAmount(), &gen) != 1)
return false; return false;
} else if (val.IsCommitment()) { } else if (val.IsCommitment()) {
@ -831,8 +832,7 @@ bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::ve
// Null nAmount is considered explicit 0, so just check for commitment // Null nAmount is considered explicit 0, so just check for commitment
CalculateReissuanceToken(assetTokenID, entropy, issuance.nAmount.IsCommitment()); CalculateReissuanceToken(assetTokenID, entropy, issuance.nAmount.IsCommitment());
} else { } else {
//Re-issuance // Re-issuance
// hashAssetIdentifier doubles as the entropy on reissuance // hashAssetIdentifier doubles as the entropy on reissuance
CalculateAsset(assetID, issuance.assetEntropy); CalculateAsset(assetID, issuance.assetEntropy);
CalculateReissuanceToken(assetTokenID, issuance.assetEntropy, issuance.nAmount.IsCommitment()); CalculateReissuanceToken(assetTokenID, issuance.assetEntropy, issuance.nAmount.IsCommitment());
@ -927,6 +927,7 @@ bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::ve
continue; continue;
} else { } else {
// No spendable 0-value outputs // No spendable 0-value outputs
// Reason: A spendable output of 0 reissuance tokens would allow reissuance without reissuance tokens.
return false; return false;
} }
} }
@ -977,11 +978,12 @@ bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::ve
} }
} }
// Surjection proofs
for (size_t i = 0; i < tx.vout.size(); i++) for (size_t i = 0; i < tx.vout.size(); i++)
{ {
const CConfidentialAsset& asset = tx.vout[i].nAsset; const CConfidentialAsset& asset = tx.vout[i].nAsset;
const CTxOutWitness* ptxoutwit = tx.wit.vtxoutwit.size() <= i? NULL: &tx.wit.vtxoutwit[i]; const CTxOutWitness* ptxoutwit = tx.wit.vtxoutwit.size() <= i? NULL: &tx.wit.vtxoutwit[i];
//No need for surjective proof // No need for surjection proof
if (asset.IsExplicit()) { if (asset.IsExplicit()) {
if (ptxoutwit && !ptxoutwit->vchSurjectionproof.empty()) { if (ptxoutwit && !ptxoutwit->vchSurjectionproof.empty()) {
return false; return false;

9
src/validation.h
View file

@ -399,11 +399,14 @@ bool CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoins
/** /**
* Verify the transaction's outputs spend exactly what its inputs provide, plus some excess amount. * Verify the transaction's outputs spend exactly what its inputs provide, plus some excess amount.
* *
* This also checks rangeproofs, surjection proofs, and issuances of assets and re-issuance tokens.
* The function assumes that IsValidPeginWitness() returns true on all peg-in inputs.
*
* @param[in] view CCoinsViewCache to find necessary outputs * @param[in] view CCoinsViewCache to find necessary outputs
* @param[in] tx transaction for which we are checking totals * @param[in] tx transaction for which we are checking totals
* @param[in] pvChecks multithreaded rangeproof and commitment checker * @param[in] pvChecks multithreaded rangeproof, surjection proof and commitment checker
* @param[in] cacheStore signal if rangeproof verification should be cached * @param[in] cacheStore signal if rangeproof and surjection proof verification should be cached
* @return True if totals are identical * @return True if verification was not aborted and totals are identical
*/ */
bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::vector<CCheck*>* pvChecks = NULL, const bool cacheStore = false); bool VerifyAmounts(const CCoinsViewCache& cache, const CTransaction& tx, std::vector<CCheck*>* pvChecks = NULL, const bool cacheStore = false);