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authorPieter Wuille <pieter.wuille@gmail.com>2017-01-04 11:56:05 -0800
committerPieter Wuille <pieter.wuille@gmail.com>2017-01-04 11:56:17 -0800
commit7dac1e5e9e887f5f6ff146e812a05bd3bf281eae (patch)
tree197aff6995a6824501578bbfd5afaa7e4c4d8479 /src
parent0fc1c31a878e93d938c67db3f958e82e3c39659f (diff)
parentb50cd7a67e71051db59199a4185e7c82b669c659 (diff)
Merge #9107: Safer modify new coins
b50cd7a Fix dangerous condition in ModifyNewCoins. (Alex Morcos)
Diffstat (limited to 'src')
-rw-r--r--src/coins.cpp37
-rw-r--r--src/coins.h5
-rw-r--r--src/test/coins_tests.cpp199
-rw-r--r--src/validation.cpp2
4 files changed, 181 insertions, 62 deletions
diff --git a/src/coins.cpp b/src/coins.cpp
index 04b3a6f23d..68f32a9da4 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -117,17 +117,37 @@ CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
return CCoinsModifier(*this, ret.first, cachedCoinUsage);
}
-// ModifyNewCoins has to know whether the new outputs its creating are for a
-// coinbase or not. If they are for a coinbase, it can not mark them as fresh.
-// This is to ensure that the historical duplicate coinbases before BIP30 was
-// in effect will still be properly overwritten when spent.
+/* ModifyNewCoins allows for faster coin modification when creating the new
+ * outputs from a transaction. It assumes that BIP 30 (no duplicate txids)
+ * applies and has already been tested for (or the test is not required due to
+ * BIP 34, height in coinbase). If we can assume BIP 30 then we know that any
+ * non-coinbase transaction we are adding to the UTXO must not already exist in
+ * the utxo unless it is fully spent. Thus we can check only if it exists DIRTY
+ * at the current level of the cache, in which case it is not safe to mark it
+ * FRESH (b/c then its spentness still needs to flushed). If it's not dirty and
+ * doesn't exist or is pruned in the current cache, we know it either doesn't
+ * exist or is pruned in parent caches, which is the definition of FRESH. The
+ * exception to this is the two historical violations of BIP 30 in the chain,
+ * both of which were coinbases. We do not mark these fresh so we we can ensure
+ * that they will still be properly overwritten when spent.
+ */
CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid, bool coinbase) {
assert(!hasModifier);
std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
- ret.first->second.coins.Clear();
if (!coinbase) {
- ret.first->second.flags = CCoinsCacheEntry::FRESH;
+ // New coins must not already exist.
+ if (!ret.first->second.coins.IsPruned())
+ throw std::logic_error("ModifyNewCoins should not find pre-existing coins on a non-coinbase unless they are pruned!");
+
+ if (!(ret.first->second.flags & CCoinsCacheEntry::DIRTY)) {
+ // If the coin is known to be pruned (have no unspent outputs) in
+ // the current view and the cache entry is not dirty, we know the
+ // coin also must be pruned in the parent view as well, so it is safe
+ // to mark this fresh.
+ ret.first->second.flags |= CCoinsCacheEntry::FRESH;
+ }
}
+ ret.first->second.coins.Clear();
ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
return CCoinsModifier(*this, ret.first, 0);
}
@@ -200,6 +220,11 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
itUs->second.coins.swap(it->second.coins);
cachedCoinsUsage += itUs->second.coins.DynamicMemoryUsage();
itUs->second.flags |= CCoinsCacheEntry::DIRTY;
+ // NOTE: It is possible the child has a FRESH flag here in
+ // the event the entry we found in the parent is pruned. But
+ // we must not copy that FRESH flag to the parent as that
+ // pruned state likely still needs to be communicated to the
+ // grandparent.
}
}
}
diff --git a/src/coins.h b/src/coins.h
index b1a2c08845..902cb57f69 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -269,6 +269,11 @@ struct CCoinsCacheEntry
enum Flags {
DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
+ /* Note that FRESH is a performance optimization with which we can
+ * erase coins that are fully spent if we know we do not need to
+ * flush the changes to the parent cache. It is always safe to
+ * not mark FRESH if that condition is not guaranteed.
+ */
};
CCoinsCacheEntry() : coins(), flags(0) {}
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index 2f8857953c..70b958c296 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -5,6 +5,7 @@
#include "coins.h"
#include "script/standard.h"
#include "uint256.h"
+#include "undo.h"
#include "utilstrencodings.h"
#include "test/test_bitcoin.h"
#include "test/test_random.h"
@@ -16,6 +17,9 @@
#include <boost/test/unit_test.hpp>
+bool ApplyTxInUndo(const CTxInUndo& undo, CCoinsViewCache& view, const COutPoint& out);
+void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, CTxUndo &txundo, int nHeight);
+
namespace
{
class CCoinsViewTest : public CCoinsView
@@ -213,6 +217,22 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
BOOST_CHECK(missed_an_entry);
}
+typedef std::tuple<CTransaction,CTxUndo,CCoins> TxData;
+// Store of all necessary tx and undo data for next test
+std::map<uint256, TxData> alltxs;
+
+TxData &FindRandomFrom(const std::set<uint256> &txidset) {
+ assert(txidset.size());
+ std::set<uint256>::iterator txIt = txidset.lower_bound(GetRandHash());
+ if (txIt == txidset.end()) {
+ txIt = txidset.begin();
+ }
+ std::map<uint256, TxData>::iterator txdit = alltxs.find(*txIt);
+ assert(txdit != alltxs.end());
+ return txdit->second;
+}
+
+
// This test is similar to the previous test
// except the emphasis is on testing the functionality of UpdateCoins
// random txs are created and UpdateCoins is used to update the cache stack
@@ -229,77 +249,139 @@ BOOST_AUTO_TEST_CASE(updatecoins_simulation_test)
std::vector<CCoinsViewCacheTest*> stack; // A stack of CCoinsViewCaches on top.
stack.push_back(new CCoinsViewCacheTest(&base)); // Start with one cache.
- // Track the txids we've used and whether they have been spent or not
- std::map<uint256, CAmount> coinbaseids;
- std::set<uint256> alltxids;
+ // Track the txids we've used in various sets
+ std::set<uint256> coinbaseids;
+ std::set<uint256> disconnectedids;
std::set<uint256> duplicateids;
+ std::set<uint256> utxoset;
for (unsigned int i = 0; i < NUM_SIMULATION_ITERATIONS; i++) {
- {
+ uint32_t randiter = insecure_rand();
+
+ // 19/20 txs add a new transaction
+ if (randiter % 20 < 19) {
CMutableTransaction tx;
tx.vin.resize(1);
tx.vout.resize(1);
tx.vout[0].nValue = i; //Keep txs unique unless intended to duplicate
unsigned int height = insecure_rand();
+ CCoins oldcoins;
- // 1/10 times create a coinbase
- if (insecure_rand() % 10 == 0 || coinbaseids.size() < 10) {
- // 1/100 times create a duplicate coinbase
+ // 2/20 times create a new coinbase
+ if (randiter % 20 < 2 || coinbaseids.size() < 10) {
+ // 1/10 of those times create a duplicate coinbase
if (insecure_rand() % 10 == 0 && coinbaseids.size()) {
- std::map<uint256, CAmount>::iterator coinbaseIt = coinbaseids.lower_bound(GetRandHash());
- if (coinbaseIt == coinbaseids.end()) {
- coinbaseIt = coinbaseids.begin();
- }
- //Use same random value to have same hash and be a true duplicate
- tx.vout[0].nValue = coinbaseIt->second;
- assert(tx.GetHash() == coinbaseIt->first);
- duplicateids.insert(coinbaseIt->first);
+ TxData &txd = FindRandomFrom(coinbaseids);
+ // Reuse the exact same coinbase
+ tx = std::get<0>(txd);
+ // shouldn't be available for reconnection if its been duplicated
+ disconnectedids.erase(tx.GetHash());
+
+ duplicateids.insert(tx.GetHash());
}
else {
- coinbaseids[tx.GetHash()] = tx.vout[0].nValue;
+ coinbaseids.insert(tx.GetHash());
}
assert(CTransaction(tx).IsCoinBase());
}
- // 9/10 times create a regular tx
+
+ // 17/20 times reconnect previous or add a regular tx
else {
+
uint256 prevouthash;
- // equally likely to spend coinbase or non coinbase
- std::set<uint256>::iterator txIt = alltxids.lower_bound(GetRandHash());
- if (txIt == alltxids.end()) {
- txIt = alltxids.begin();
+ // 1/20 times reconnect a previously disconnected tx
+ if (randiter % 20 == 2 && disconnectedids.size()) {
+ TxData &txd = FindRandomFrom(disconnectedids);
+ tx = std::get<0>(txd);
+ prevouthash = tx.vin[0].prevout.hash;
+ if (!CTransaction(tx).IsCoinBase() && !utxoset.count(prevouthash)) {
+ disconnectedids.erase(tx.GetHash());
+ continue;
+ }
+
+ // If this tx is already IN the UTXO, then it must be a coinbase, and it must be a duplicate
+ if (utxoset.count(tx.GetHash())) {
+ assert(CTransaction(tx).IsCoinBase());
+ assert(duplicateids.count(tx.GetHash()));
+ }
+ disconnectedids.erase(tx.GetHash());
}
- prevouthash = *txIt;
- // Construct the tx to spend the coins of prevouthash
- tx.vin[0].prevout.hash = prevouthash;
- tx.vin[0].prevout.n = 0;
+ // 16/20 times create a regular tx
+ else {
+ TxData &txd = FindRandomFrom(utxoset);
+ prevouthash = std::get<0>(txd).GetHash();
+ // Construct the tx to spend the coins of prevouthash
+ tx.vin[0].prevout.hash = prevouthash;
+ tx.vin[0].prevout.n = 0;
+ assert(!CTransaction(tx).IsCoinBase());
+ }
+ // In this simple test coins only have two states, spent or unspent, save the unspent state to restore
+ oldcoins = result[prevouthash];
// Update the expected result of prevouthash to know these coins are spent
- CCoins& oldcoins = result[prevouthash];
- oldcoins.Clear();
+ result[prevouthash].Clear();
- // It is of particular importance here that once we spend a coinbase tx hash
- // it is no longer available to be duplicated (or spent again)
- // BIP 34 in conjunction with enforcing BIP 30 (at least until BIP 34 was active)
- // results in the fact that no coinbases were duplicated after they were already spent
- alltxids.erase(prevouthash);
- coinbaseids.erase(prevouthash);
+ utxoset.erase(prevouthash);
// The test is designed to ensure spending a duplicate coinbase will work properly
// if that ever happens and not resurrect the previously overwritten coinbase
if (duplicateids.count(prevouthash))
spent_a_duplicate_coinbase = true;
- assert(!CTransaction(tx).IsCoinBase());
}
- // Track this tx to possibly spend later
- alltxids.insert(tx.GetHash());
-
// Update the expected result to know about the new output coins
- CCoins &coins = result[tx.GetHash()];
- coins.FromTx(tx, height);
+ result[tx.GetHash()].FromTx(tx, height);
+
+ // Call UpdateCoins on the top cache
+ CTxUndo undo;
+ UpdateCoins(tx, *(stack.back()), undo, height);
- UpdateCoins(tx, *(stack.back()), height);
+ // Update the utxo set for future spends
+ utxoset.insert(tx.GetHash());
+
+ // Track this tx and undo info to use later
+ alltxs.insert(std::make_pair(tx.GetHash(),std::make_tuple(tx,undo,oldcoins)));
+ }
+
+ //1/20 times undo a previous transaction
+ else if (utxoset.size()) {
+ TxData &txd = FindRandomFrom(utxoset);
+
+ CTransaction &tx = std::get<0>(txd);
+ CTxUndo &undo = std::get<1>(txd);
+ CCoins &origcoins = std::get<2>(txd);
+
+ uint256 undohash = tx.GetHash();
+
+ // Update the expected result
+ // Remove new outputs
+ result[undohash].Clear();
+ // If not coinbase restore prevout
+ if (!tx.IsCoinBase()) {
+ result[tx.vin[0].prevout.hash] = origcoins;
+ }
+
+ // Disconnect the tx from the current UTXO
+ // See code in DisconnectBlock
+ // remove outputs
+ {
+ CCoinsModifier outs = stack.back()->ModifyCoins(undohash);
+ outs->Clear();
+ }
+ // restore inputs
+ if (!tx.IsCoinBase()) {
+ const COutPoint &out = tx.vin[0].prevout;
+ const CTxInUndo &undoin = undo.vprevout[0];
+ ApplyTxInUndo(undoin, *(stack.back()), out);
+ }
+ // Store as a candidate for reconnection
+ disconnectedids.insert(undohash);
+
+ // Update the utxoset
+ utxoset.erase(undohash);
+ if (!tx.IsCoinBase())
+ utxoset.insert(tx.vin[0].prevout.hash);
}
// Once every 1000 iterations and at the end, verify the full cache.
@@ -308,9 +390,9 @@ BOOST_AUTO_TEST_CASE(updatecoins_simulation_test)
const CCoins* coins = stack.back()->AccessCoins(it->first);
if (coins) {
BOOST_CHECK(*coins == it->second);
- } else {
+ } else {
BOOST_CHECK(it->second.IsPruned());
- }
+ }
}
}
@@ -334,7 +416,7 @@ BOOST_AUTO_TEST_CASE(updatecoins_simulation_test)
tip = stack.back();
}
stack.push_back(new CCoinsViewCacheTest(tip));
- }
+ }
}
}
@@ -420,6 +502,7 @@ BOOST_AUTO_TEST_CASE(ccoins_serialization)
const static uint256 TXID;
const static CAmount PRUNED = -1;
const static CAmount ABSENT = -2;
+const static CAmount FAIL = -3;
const static CAmount VALUE1 = 100;
const static CAmount VALUE2 = 200;
const static CAmount VALUE3 = 300;
@@ -630,11 +713,17 @@ BOOST_AUTO_TEST_CASE(ccoins_modify)
void CheckModifyNewCoinsBase(CAmount base_value, CAmount cache_value, CAmount modify_value, CAmount expected_value, char cache_flags, char expected_flags, bool coinbase)
{
SingleEntryCacheTest test(base_value, cache_value, cache_flags);
- SetCoinsValue(modify_value, *test.cache.ModifyNewCoins(TXID, coinbase));
CAmount result_value;
char result_flags;
- GetCoinsMapEntry(test.cache.map(), result_value, result_flags);
+ try {
+ SetCoinsValue(modify_value, *test.cache.ModifyNewCoins(TXID, coinbase));
+ GetCoinsMapEntry(test.cache.map(), result_value, result_flags);
+ } catch (std::logic_error& e) {
+ result_value = FAIL;
+ result_flags = NO_ENTRY;
+ }
+
BOOST_CHECK_EQUAL(result_value, expected_value);
BOOST_CHECK_EQUAL(result_flags, expected_flags);
}
@@ -669,7 +758,7 @@ BOOST_AUTO_TEST_CASE(ccoins_modify_new)
CheckModifyNewCoins(PRUNED, PRUNED, PRUNED, 0 , DIRTY , true );
CheckModifyNewCoins(PRUNED, PRUNED, ABSENT, FRESH , NO_ENTRY , false);
CheckModifyNewCoins(PRUNED, PRUNED, ABSENT, FRESH , NO_ENTRY , true );
- CheckModifyNewCoins(PRUNED, PRUNED, ABSENT, DIRTY , NO_ENTRY , false);
+ CheckModifyNewCoins(PRUNED, PRUNED, PRUNED, DIRTY , DIRTY , false);
CheckModifyNewCoins(PRUNED, PRUNED, PRUNED, DIRTY , DIRTY , true );
CheckModifyNewCoins(PRUNED, PRUNED, ABSENT, DIRTY|FRESH, NO_ENTRY , false);
CheckModifyNewCoins(PRUNED, PRUNED, ABSENT, DIRTY|FRESH, NO_ENTRY , true );
@@ -677,25 +766,25 @@ BOOST_AUTO_TEST_CASE(ccoins_modify_new)
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, 0 , DIRTY , true );
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, FRESH , DIRTY|FRESH, false);
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, FRESH , DIRTY|FRESH, true );
- CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, DIRTY , DIRTY|FRESH, false);
+ CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, DIRTY , DIRTY , false);
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, DIRTY , DIRTY , true );
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, DIRTY|FRESH, DIRTY|FRESH, false);
CheckModifyNewCoins(PRUNED, VALUE3, VALUE3, DIRTY|FRESH, DIRTY|FRESH, true );
- CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, 0 , NO_ENTRY , false);
+ CheckModifyNewCoins(VALUE2, PRUNED, FAIL , 0 , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, PRUNED, PRUNED, 0 , DIRTY , true );
- CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, FRESH , NO_ENTRY , false);
+ CheckModifyNewCoins(VALUE2, PRUNED, FAIL , FRESH , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, FRESH , NO_ENTRY , true );
- CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, DIRTY , NO_ENTRY , false);
+ CheckModifyNewCoins(VALUE2, PRUNED, FAIL , DIRTY , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, PRUNED, PRUNED, DIRTY , DIRTY , true );
- CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, DIRTY|FRESH, NO_ENTRY , false);
+ CheckModifyNewCoins(VALUE2, PRUNED, FAIL , DIRTY|FRESH, NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, PRUNED, ABSENT, DIRTY|FRESH, NO_ENTRY , true );
- CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, 0 , DIRTY|FRESH, false);
+ CheckModifyNewCoins(VALUE2, VALUE3, FAIL , 0 , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, 0 , DIRTY , true );
- CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, FRESH , DIRTY|FRESH, false);
+ CheckModifyNewCoins(VALUE2, VALUE3, FAIL , FRESH , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, FRESH , DIRTY|FRESH, true );
- CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, DIRTY , DIRTY|FRESH, false);
+ CheckModifyNewCoins(VALUE2, VALUE3, FAIL , DIRTY , NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, DIRTY , DIRTY , true );
- CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, DIRTY|FRESH, DIRTY|FRESH, false);
+ CheckModifyNewCoins(VALUE2, VALUE3, FAIL , DIRTY|FRESH, NO_ENTRY , false);
CheckModifyNewCoins(VALUE2, VALUE3, VALUE3, DIRTY|FRESH, DIRTY|FRESH, true );
}
diff --git a/src/validation.cpp b/src/validation.cpp
index bc14c1d8c6..ca1e5a713c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1499,7 +1499,7 @@ bool AbortNode(CValidationState& state, const std::string& strMessage, const std
* @param out The out point that corresponds to the tx input.
* @return True on success.
*/
-static bool ApplyTxInUndo(const CTxInUndo& undo, CCoinsViewCache& view, const COutPoint& out)
+bool ApplyTxInUndo(const CTxInUndo& undo, CCoinsViewCache& view, const COutPoint& out)
{
bool fClean = true;