1 files changed, 122 insertions, 0 deletions
diff --git a/src/script/sigcache.cpp b/src/script/sigcache.cpp
new file mode 100644
index 000000000..c1786140d
--- /dev/null
+++ b/src/script/sigcache.cpp
@@ -0,0 +1,122 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <script/sigcache.h>
+
+#include <pubkey.h>
+#include <random.h>
+#include <uint256.h>
+#include <util/system.h>
+
+#include <cuckoocache.h>
+#include <boost/thread/shared_mutex.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:
+     //! Entries are SHA256(nonce || 'E' or 'S' || 31 zero bytes || signature hash || public key || signature):
+    CSHA256 m_salted_hasher_ecdsa;
+    CSHA256 m_salted_hasher_schnorr;
+    typedef CuckooCache::cache<uint256, SignatureCacheHasher> map_type;
+    map_type setValid;
+    boost::shared_mutex cs_sigcache;
+
+public:
+    CSignatureCache()
+    {
+        uint256 nonce = GetRandHash();
+        // We want the nonce to be 64 bytes long to force the hasher to process
+        // this chunk, which makes later hash computations more efficient. We
+        // just write our 32-byte entropy, and then pad with 'E' for ECDSA and
+        // 'S' for Schnorr (followed by 0 bytes).
+        static constexpr unsigned char PADDING_ECDSA[32] = {'E'};
+        static constexpr unsigned char PADDING_SCHNORR[32] = {'S'};
+        m_salted_hasher_ecdsa.Write(nonce.begin(), 32);
+        m_salted_hasher_ecdsa.Write(PADDING_ECDSA, 32);
+        m_salted_hasher_schnorr.Write(nonce.begin(), 32);
+        m_salted_hasher_schnorr.Write(PADDING_SCHNORR, 32);
+    }
+
+    void
+    ComputeEntryECDSA(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey) const
+    {
+        CSHA256 hasher = m_salted_hasher_ecdsa;
+        hasher.Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());
+    }
+
+    void
+    ComputeEntrySchnorr(uint256& entry, const uint256 &hash, Span<const unsigned char> sig, const XOnlyPubKey& pubkey) const
+    {
+        CSHA256 hasher = m_salted_hasher_schnorr;
+        hasher.Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(sig.data(), sig.size()).Finalize(entry.begin());
+    }
+
+    bool
+    Get(const uint256& entry, const bool erase)
+    {
+        boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
+        return setValid.contains(entry, erase);
+    }
+
+    void Set(uint256& entry)
+    {
+        boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
+        setValid.insert(entry);
+    }
+    uint32_t setup_bytes(size_t n)
+    {
+        return setValid.setup_bytes(n);
+    }
+};
+
+/* In previous versions of this code, signatureCache was a local static variable
+ * in CachingTransactionSignatureChecker::VerifySignature.  We initialize
+ * signatureCache outside of VerifySignature to avoid the atomic operation per
+ * call overhead associated with local static variables even though
+ * signatureCache could be made local to VerifySignature.
+*/
+static CSignatureCache signatureCache;
+} // namespace
+
+// To be called once in AppInitMain/BasicTestingSetup to initialize the
+// signatureCache.
+void InitSignatureCache()
+{
+    // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
+    // setup_bytes creates the minimum possible cache (2 elements).
+    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+    size_t nElems = signatureCache.setup_bytes(nMaxCacheSize);
+    LogPrintf("Using %zu MiB out of %zu/2 requested for signature cache, able to store %zu elements\n",
+            (nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
+}
+
+bool CachingTransactionSignatureChecker::VerifyECDSASignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
+{
+    uint256 entry;
+    signatureCache.ComputeEntryECDSA(entry, sighash, vchSig, pubkey);
+    if (signatureCache.Get(entry, !store))
+        return true;
+    if (!TransactionSignatureChecker::VerifyECDSASignature(vchSig, pubkey, sighash))
+        return false;
+    if (store)
+        signatureCache.Set(entry);
+    return true;
+}
+
+bool CachingTransactionSignatureChecker::VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const
+{
+    uint256 entry;
+    signatureCache.ComputeEntrySchnorr(entry, sighash, sig, pubkey);
+    if (signatureCache.Get(entry, !store)) return true;
+    if (!TransactionSignatureChecker::VerifySchnorrSignature(sig, pubkey, sighash)) return false;
+    if (store) signatureCache.Set(entry);
+    return true;
+}