src/script/sigcache.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "sigcache.h"
   7
   8 #include "memusage.h"
   9 #include "pubkey.h"
  10 #include "random.h"
  11 #include "uint256.h"
  12 #include "util.h"
  13
  14 #include "cuckoocache.h"
  15 #include <boost/thread.hpp>
  16
  17 namespace {
  18 /**
  19  * Valid signature cache, to avoid doing expensive ECDSA signature checking
  20  * twice for every transaction (once when accepted into memory pool, and
  21  * again when accepted into the block chain)
  22  */
  23 class CSignatureCache
  24 {
  25 private:
  26      //! Entries are SHA256(nonce || signature hash || public key || signature):
  27     uint256 nonce;
  28     typedef CuckooCache::cache<uint256, SignatureCacheHasher> map_type;
  29     map_type setValid;
  30     boost::shared_mutex cs_sigcache;
  31
  32 public:
  33     CSignatureCache()
  34     {
  35         GetRandBytes(nonce.begin(), 32);
  36     }
  37
  38     void
  39     ComputeEntry(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey)
  40     {
  41         CSHA256().Write(nonce.begin(), 32).Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());
  42     }
  43
  44     bool
  45     Get(const uint256& entry, const bool erase)
  46     {
  47         boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
  48         return setValid.contains(entry, erase);
  49     }
  50
  51     void Set(uint256& entry)
  52     {
  53         boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
  54         setValid.insert(entry);
  55     }
  56     uint32_t setup_bytes(size_t n)
  57     {
  58         return setValid.setup_bytes(n);
  59     }
  60 };
  61
  62 /* In previous versions of this code, signatureCache was a local static variable
  63  * in CachingTransactionSignatureChecker::VerifySignature.  We initialize
  64  * signatureCache outside of VerifySignature to avoid the atomic operation per
  65  * call overhead associated with local static variables even though
  66  * signatureCache could be made local to VerifySignature.
  67 */
  68 static CSignatureCache signatureCache;
  69 } // namespace
  70
  71 // To be called once in AppInitMain/BasicTestingSetup to initialize the
  72 // signatureCache.
  73 void InitSignatureCache()
  74 {
  75     // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
  76     // setup_bytes creates the minimum possible cache (2 elements).
  77     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);
  78     size_t nElems = signatureCache.setup_bytes(nMaxCacheSize);
  79     LogPrintf("Using %zu MiB out of %zu/2 requested for signature cache, able to store %zu elements\n",
  80             (nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
  81 }
  82
  83 bool CachingTransactionSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
  84 {
  85     uint256 entry;
  86     signatureCache.ComputeEntry(entry, sighash, vchSig, pubkey);
  87     if (signatureCache.Get(entry, !store))
  88         return true;
  89     if (!TransactionSignatureChecker::VerifySignature(vchSig, pubkey, sighash))
  90         return false;
  91     if (store)
  92         signatureCache.Set(entry);
  93     return true;
  94 }