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Cache signature verifications

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Create a maximum-10MB signature verification result cache.
This should almost double the number of transactions that
can be processed on a given CPU, because before this change
ECDSA signatures were verified when transactions were added
to the memory pool and then again when they appeared in
a block.
This commit is contained in:
Gavin Andresen 2012-05-16 15:57:04 -04:00
parent 4add41a2a6
commit 62922c8ab0
2 changed files with 160 additions and 1 deletions
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68
src/key.cpp
View file

@ -2,10 +2,14 @@
// Distributed under the MIT/X11 software license, see the accompanying
// file license.txt or http://www.opensource.org/licenses/mit-license.php.
#include <map>
#include <boost/tuple/tuple.hpp>
#include <openssl/ecdsa.h>
#include <openssl/obj_mac.h>
#include "key.h"
#include "util.h"
// Generate a private key from just the secret parameter
int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
@ -347,21 +351,85 @@ bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& v
return false;
}
// Valid signature cache, to avoid doing expensive ECDSA signature checking
// twice for every transaction (once when accepted into memory pool, and
// again when accepted into the block chain)
// sigdata_type is (signature hash, signature, public key):
typedef boost::tuple<uint256, std::vector<unsigned char>, std::vector<unsigned char> > sigdata_type;
static std::set< sigdata_type> setValidSigCache;
static CCriticalSection cs_sigcache;
static bool
GetValidSigCache(uint256 hash, const std::vector<unsigned char>& vchSig, const std::vector<unsigned char>& pubKey)
{
LOCK(cs_sigcache);
sigdata_type k(hash, vchSig, pubKey);
std::set<sigdata_type>::iterator mi = setValidSigCache.find(k);
if (mi != setValidSigCache.end())
return true;
return false;
}
static void
SetValidSigCache(uint256 hash, const std::vector<unsigned char>& vchSig, const std::vector<unsigned char>& pubKey)
{
// DoS prevention: limit cache size to less than 10MB
// (~200 bytes per cache entry times 50,000 entries)
// Since there are a maximum of 20,000 signature operations per block
// 50,000 is a reasonable default.
int64 nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
if (nMaxCacheSize <= 0) return;
LOCK(cs_sigcache);
while (setValidSigCache.size() > nMaxCacheSize)
{
// Evict a random entry. Random because that helps
// foil would-be DoS attackers who might try to pre-generate
// and re-use a set of valid signatures just-slightly-greater
// than our cache size.
uint256 randomHash = GetRandHash();
std::vector<unsigned char> unused;
std::set<sigdata_type>::iterator it =
setValidSigCache.lower_bound(sigdata_type(randomHash, unused, unused));
if (it == setValidSigCache.end())
it = setValidSigCache.begin();
setValidSigCache.erase(*it);
}
sigdata_type k(hash, vchSig, pubKey);
setValidSigCache.insert(k);
}
bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
{
if (GetValidSigCache(hash, vchSig, GetPubKey()))
return true;
// -1 = error, 0 = bad sig, 1 = good
if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
return false;
// good sig
SetValidSigCache(hash, vchSig, GetPubKey());
return true;
}
bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
{
if (GetValidSigCache(hash, vchSig, GetPubKey()))
return true;
CKey key;
if (!key.SetCompactSignature(hash, vchSig))
return false;
if (GetPubKey() != key.GetPubKey())
return false;
SetValidSigCache(hash, vchSig, GetPubKey());
return true;
}

93
src/test/DoS_tests.cpp
View file

@ -1,7 +1,10 @@
//
// Unit tests for denial-of-service detection/prevention code
//
#include <algorithm>
#include <boost/assign/list_of.hpp> // for 'map_list_of()'
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/test/unit_test.hpp>
#include <boost/foreach.hpp>
@ -57,7 +60,7 @@ BOOST_AUTO_TEST_CASE(DoS_banscore)
BOOST_CHECK(!CNode::IsBanned(addr1));
dummyNode1.Misbehaving(1);
BOOST_CHECK(CNode::IsBanned(addr1));
mapArgs["-banscore"] = "100";
mapArgs.erase("-banscore");
}
BOOST_AUTO_TEST_CASE(DoS_bantime)
@ -220,4 +223,92 @@ BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
BOOST_CHECK(mapOrphanTransactionsByPrev.empty());
}
BOOST_AUTO_TEST_CASE(DoS_checkSig)
{
// Test signature caching code (see key.cpp Verify() methods)
CKey key;
key.MakeNewKey(true);
CBasicKeyStore keystore;
keystore.AddKey(key);
// 100 orphan transactions:
static const int NPREV=100;
CTransaction orphans[NPREV];
for (int i = 0; i < NPREV; i++)
{
CTransaction& tx = orphans[i];
tx.vin.resize(1);
tx.vin[0].prevout.n = 0;
tx.vin[0].prevout.hash = GetRandHash();
tx.vin[0].scriptSig << OP_1;
tx.vout.resize(1);
tx.vout[0].nValue = 1*CENT;
tx.vout[0].scriptPubKey.SetBitcoinAddress(key.GetPubKey());
CDataStream ds(SER_DISK, CLIENT_VERSION);
ds << tx;
AddOrphanTx(ds);
}
// Create a transaction that depends on orphans:
CTransaction tx;
tx.vout.resize(1);
tx.vout[0].nValue = 1*CENT;
tx.vout[0].scriptPubKey.SetBitcoinAddress(key.GetPubKey());
tx.vin.resize(NPREV);
for (int j = 0; j < tx.vin.size(); j++)
{
tx.vin[j].prevout.n = 0;
tx.vin[j].prevout.hash = orphans[j].GetHash();
}
// Creating signatures primes the cache:
boost::posix_time::ptime mst1 = boost::posix_time::microsec_clock::local_time();
for (int j = 0; j < tx.vin.size(); j++)
BOOST_CHECK(SignSignature(keystore, orphans[j], tx, j));
boost::posix_time::ptime mst2 = boost::posix_time::microsec_clock::local_time();
boost::posix_time::time_duration msdiff = mst2 - mst1;
long nOneValidate = msdiff.total_milliseconds();
if (fDebug) printf("DoS_Checksig sign: %ld\n", nOneValidate);
// ... now validating repeatedly should be quick:
// 2.8GHz machine, -g build: Sign takes ~760ms,
// uncached Verify takes ~250ms, cached Verify takes ~50ms
// (for 100 single-signature inputs)
mst1 = boost::posix_time::microsec_clock::local_time();
for (int i = 0; i < 5; i++)
for (int j = 0; j < tx.vin.size(); j++)
BOOST_CHECK(VerifySignature(orphans[j], tx, j, true, SIGHASH_ALL));
mst2 = boost::posix_time::microsec_clock::local_time();
msdiff = mst2 - mst1;
long nManyValidate = msdiff.total_milliseconds();
if (fDebug) printf("DoS_Checksig five: %ld\n", nManyValidate);
BOOST_CHECK_MESSAGE(nManyValidate < nOneValidate, "Signature cache timing failed");
// Empty a signature, validation should fail:
CScript save = tx.vin[0].scriptSig;
tx.vin[0].scriptSig = CScript();
BOOST_CHECK(!VerifySignature(orphans[0], tx, 0, true, SIGHASH_ALL));
tx.vin[0].scriptSig = save;
// Swap signatures, validation should fail:
std::swap(tx.vin[0].scriptSig, tx.vin[1].scriptSig);
BOOST_CHECK(!VerifySignature(orphans[0], tx, 0, true, SIGHASH_ALL));
BOOST_CHECK(!VerifySignature(orphans[1], tx, 1, true, SIGHASH_ALL));
std::swap(tx.vin[0].scriptSig, tx.vin[1].scriptSig);
// Exercise -maxsigcachesize code:
mapArgs["-maxsigcachesize"] = "10";
// Generate a new, different signature for vin[0] to trigger cache clear:
CScript oldSig = tx.vin[0].scriptSig;
BOOST_CHECK(SignSignature(keystore, orphans[0], tx, 0));
BOOST_CHECK(tx.vin[0].scriptSig != oldSig);
for (int j = 0; j < tx.vin.size(); j++)
BOOST_CHECK(VerifySignature(orphans[j], tx, j, true, SIGHASH_ALL));
mapArgs.erase("-maxsigcachesize");
LimitOrphanTxSize(0);
}
BOOST_AUTO_TEST_SUITE_END()