Make signature cache optional

src/Makefile.am

@@ -103,6 +103,7 @@ BITCOIN_CORE_H = \
   script/compressor.h \
   script/interpreter.h \
   script/script.h \
+  script/sigcache.h \
   script/sign.h \
   script/standard.h \
   serialize.h \
@@ -218,6 +219,7 @@ libbitcoin_common_a_SOURCES = \
   script/compressor.cpp \
   script/interpreter.cpp \
   script/script.cpp \
+  script/sigcache.cpp \
   script/sign.cpp \
   script/standard.cpp \
   $(BITCOIN_CORE_H)

src/bitcoin-tx.cpp

@@ -435,7 +435,7 @@ static void MutateTxSign(CMutableTransaction& tx, const string& flagStr)
         BOOST_FOREACH(const CTransaction& txv, txVariants) {
             txin.scriptSig = CombineSignatures(prevPubKey, mergedTx, i, txin.scriptSig, txv.vin[i].scriptSig);
         }
-        if (!VerifyScript(txin.scriptSig, prevPubKey, mergedTx, i, STANDARD_SCRIPT_VERIFY_FLAGS))
+        if (!VerifyScript(txin.scriptSig, prevPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, SignatureChecker(mergedTx, i)))
             fComplete = false;
     }
 

src/main.cpp

@@ -645,7 +645,7 @@ bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
         // IsStandard() will have already returned false
         // and this method isn't called.
         vector<vector<unsigned char> > stack;
-        if (!EvalScript(stack, tx.vin[i].scriptSig, tx, i, false))
+        if (!EvalScript(stack, tx.vin[i].scriptSig, false, BaseSignatureChecker()))
             return false;
 
         if (whichType == TX_SCRIPTHASH)

src/main.h

@@ -17,6 +17,7 @@
 #include "net.h"
 #include "pow.h"
 #include "script/script.h"
+#include "script/sigcache.h"
 #include "script/standard.h"
 #include "sync.h"
 #include "txmempool.h"

src/script/interpreter.cpp

@@ -9,14 +9,10 @@
 #include "crypto/ripemd160.h"
 #include "crypto/sha1.h"
 #include "crypto/sha2.h"
-#include "random.h"
 #include "script/script.h"
 #include "uint256.h"
 #include "util.h"
 
-#include <boost/thread.hpp>
-#include <boost/tuple/tuple_comparison.hpp>
-
 using namespace std;
 
 typedef vector<unsigned char> valtype;
@@ -132,7 +128,7 @@ bool IsCanonicalSignature(const valtype &vchSig, unsigned int flags) {
     return true;
 }
 
-bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const SignatureChecker& checker)
+bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker)
 {
     CScript::const_iterator pc = script.begin();
     CScript::const_iterator pend = script.end();
@@ -921,65 +917,13 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
     return ss.GetHash();
 }
 
-// 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)
-class CSignatureCache
+bool SignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash, int flags) const
 {
-private:
-     // sigdata_type is (signature hash, signature, public key):
-    typedef boost::tuple<uint256, std::vector<unsigned char>, CPubKey> sigdata_type;
-    std::set< sigdata_type> setValid;
-    boost::shared_mutex cs_sigcache;
-
-public:
-    bool
-    Get(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
-    {
-        boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
-
-        sigdata_type k(hash, vchSig, pubKey);
-        std::set<sigdata_type>::iterator mi = setValid.find(k);
-        if (mi != setValid.end())
-            return true;
-        return false;
-    }
-
-    void Set(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& 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_t nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
-        if (nMaxCacheSize <= 0) return;
-
-        boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
-
-        while (static_cast<int64_t>(setValid.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 =
-                setValid.lower_bound(sigdata_type(randomHash, unused, unused));
-            if (it == setValid.end())
-                it = setValid.begin();
-            setValid.erase(*it);
-        }
-
-        sigdata_type k(hash, vchSig, pubKey);
-        setValid.insert(k);
-    }
-};
+    return pubkey.Verify(sighash, vchSig);
+}
 
 bool SignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn, const vector<unsigned char>& vchPubKey, const CScript& scriptCode, int flags) const
 {
-    static CSignatureCache signatureCache;
-
     CPubKey pubkey(vchPubKey);
     if (!pubkey.IsValid())
         return false;
@@ -993,19 +937,13 @@ bool SignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn, const vec
 
     uint256 sighash = SignatureHash(scriptCode, txTo, nIn, nHashType);
 
-    if (signatureCache.Get(sighash, vchSig, pubkey))
-        return true;
-
-    if (!pubkey.Verify(sighash, vchSig))
+    if (!VerifySignature(vchSig, pubkey, sighash, flags))
         return false;
 
-    if (!(flags & SCRIPT_VERIFY_NOCACHE))
-        signatureCache.Set(sighash, vchSig, pubkey);
-
     return true;
 }
 
-bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const SignatureChecker& checker)
+bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker)
 {
     vector<vector<unsigned char> > stack, stackCopy;
     if (!EvalScript(stack, scriptSig, flags, checker))

src/script/interpreter.h

@@ -10,9 +10,10 @@
 #include <stdint.h>
 #include <string>
 
+class uint256;
+class CPubKey;
 class CScript;
 class CTransaction;
-class uint256;
 
 /** Signature hash types/flags */
 enum
@@ -39,29 +40,32 @@ bool IsCanonicalSignature(const std::vector<unsigned char> &vchSig, unsigned int
 
 uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);
 
-class SignatureChecker
+class BaseSignatureChecker
+{
+public:
+    virtual bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, int nFlags) const
+    {
+        return false;
+    }
+
+    virtual ~BaseSignatureChecker() {}
+};
+
+class SignatureChecker : public BaseSignatureChecker
 {
 private:
     const CTransaction& txTo;
     unsigned int nIn;
 
+protected:
+    virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash, int flags) const;
+
 public:
     SignatureChecker(const CTransaction& txToIn, unsigned int nInIn) : txTo(txToIn), nIn(nInIn) {}
     bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, int nFlags) const;
 };
 
-bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const SignatureChecker& checker);
-bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const SignatureChecker& checker);
-
-// Wrappers using a default SignatureChecker.
-bool inline EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, unsigned int flags)
-{
-    return EvalScript(stack, script, flags, SignatureChecker(txTo, nIn));
-}
-
-bool inline VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn, unsigned int flags)
-{
-    return VerifyScript(scriptSig, scriptPubKey, flags, SignatureChecker(txTo, nIn));
-}
+bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker);
+bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker);
 
 #endif // H_BITCOIN_SCRIPT_INTERPRETER

src/script/sigcache.cpp

@@ -0,0 +1,88 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2013 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "sigcache.h"
+
+#include "key.h"
+#include "random.h"
+#include "uint256.h"
+#include "util.h"
+
+#include <boost/thread.hpp>
+#include <boost/tuple/tuple_comparison.hpp>
+
+namespace {
+
+// 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)
+class CSignatureCache
+{
+private:
+     // sigdata_type is (signature hash, signature, public key):
+    typedef boost::tuple<uint256, std::vector<unsigned char>, CPubKey> sigdata_type;
+    std::set< sigdata_type> setValid;
+    boost::shared_mutex cs_sigcache;
+
+public:
+    bool
+    Get(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
+    {
+        boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
+
+        sigdata_type k(hash, vchSig, pubKey);
+        std::set<sigdata_type>::iterator mi = setValid.find(k);
+        if (mi != setValid.end())
+            return true;
+        return false;
+    }
+
+    void Set(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& 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_t nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
+        if (nMaxCacheSize <= 0) return;
+
+        boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
+
+        while (static_cast<int64_t>(setValid.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 =
+                setValid.lower_bound(sigdata_type(randomHash, unused, unused));
+            if (it == setValid.end())
+                it = setValid.begin();
+            setValid.erase(*it);
+        }
+
+        sigdata_type k(hash, vchSig, pubKey);
+        setValid.insert(k);
+    }
+};
+
+}
+
+bool CachingSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash, int flags) const
+{
+    static CSignatureCache signatureCache;
+
+    if (signatureCache.Get(sighash, vchSig, pubkey))
+        return true;
+
+    if (!SignatureChecker::VerifySignature(vchSig, pubkey, sighash, flags))
+        return false;
+
+    if (!(flags & SCRIPT_VERIFY_NOCACHE))
+        signatureCache.Set(sighash, vchSig, pubkey);
+    return true;
+}

src/script/sigcache.h

@@ -0,0 +1,34 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2013 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef H_BITCOIN_SCRIPT_SIGCACHE
+#define H_BITCOIN_SCRIPT_SIGCACHE
+
+#include "script/interpreter.h"
+
+#include <vector>
+
+class CPubKey;
+
+class CachingSignatureChecker : public SignatureChecker
+{
+public:
+    CachingSignatureChecker(const CTransaction& txToIn, unsigned int nInIn) : SignatureChecker(txToIn, nInIn) {}
+
+    bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash, int flags) const;
+};
+
+// Wrappers using a default SignatureChecker.
+bool inline EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, unsigned int flags)
+{
+    return EvalScript(stack, script, flags, CachingSignatureChecker(txTo, nIn));
+}
+
+bool inline VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn, unsigned int flags)
+{
+    return VerifyScript(scriptSig, scriptPubKey, flags, CachingSignatureChecker(txTo, nIn));
+}
+
+#endif

src/script/sign.cpp

@@ -123,7 +123,7 @@ bool SignSignature(const CKeyStore &keystore, const CScript& fromPubKey, CMutabl
     }
 
     // Test solution
-    return VerifyScript(txin.scriptSig, fromPubKey, txTo, nIn, STANDARD_SCRIPT_VERIFY_FLAGS);
+    return VerifyScript(txin.scriptSig, fromPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, SignatureChecker(txTo, nIn));
 }
 
 bool SignSignature(const CKeyStore &keystore, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType)
@@ -252,9 +252,9 @@ CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsign
     Solver(scriptPubKey, txType, vSolutions);
 
     vector<valtype> stack1;
-    EvalScript(stack1, scriptSig1, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC);
+    EvalScript(stack1, scriptSig1, SCRIPT_VERIFY_STRICTENC, BaseSignatureChecker());
     vector<valtype> stack2;
-    EvalScript(stack2, scriptSig2, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC);
+    EvalScript(stack2, scriptSig2, SCRIPT_VERIFY_STRICTENC, BaseSignatureChecker());
 
     return CombineSignatures(scriptPubKey, txTo, nIn, txType, vSolutions, stack1, stack2);
 }