src/script/sigcache.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2014 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 <boost/thread.hpp>
  15 #include <boost/unordered_set.hpp>
  16
  17 namespace {
  18
  19 /**
  20  * We're hashing a nonce into the entries themselves, so we don't need extra
  21  * blinding in the set hash computation.
  22  */
  23 class CSignatureCacheHasher
  24 {
  25 public:
  26     size_t operator()(const uint256& key) const {
  27         return key.GetCheapHash();
  28     }
  29 };
  30
  31 /**
  32  * Valid signature cache, to avoid doing expensive ECDSA signature checking
  33  * twice for every transaction (once when accepted into memory pool, and
  34  * again when accepted into the block chain)
  35  */
  36 class CSignatureCache
  37 {
  38 private:
  39      //! Entries are SHA256(nonce || signature hash || public key || signature):
  40     uint256 nonce;
  41     typedef boost::unordered_set<uint256, CSignatureCacheHasher> map_type;
  42     map_type setValid;
  43     boost::shared_mutex cs_sigcache;
  44
  45
  46 public:
  47     CSignatureCache()
  48     {
  49         GetRandBytes(nonce.begin(), 32);
  50     }
  51
  52     void
  53     ComputeEntry(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey)
  54     {
  55         CSHA256().Write(nonce.begin(), 32).Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());
  56     }
  57
  58     bool
  59     Get(const uint256& entry)
  60     {
  61         boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
  62         return setValid.count(entry);
  63     }
  64
  65     void Erase(const uint256& entry)
  66     {
  67         boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
  68         setValid.erase(entry);
  69     }
  70
  71     void Set(const uint256& entry)
  72     {
  73         size_t nMaxCacheSize = GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
  74         if (nMaxCacheSize <= 0) return;
  75
  76         boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
  77         while (memusage::DynamicUsage(setValid) > nMaxCacheSize)
  78         {
  79             map_type::size_type s = GetRand(setValid.bucket_count());
  80             map_type::local_iterator it = setValid.begin(s);
  81             if (it != setValid.end(s)) {
  82                 setValid.erase(*it);
  83             }
  84         }
  85
  86         setValid.insert(entry);
  87     }
  88 };
  89
  90 }
  91
  92 bool CachingTransactionSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
  93 {
  94     static CSignatureCache signatureCache;
  95
  96     uint256 entry;
  97     signatureCache.ComputeEntry(entry, sighash, vchSig, pubkey);
  98
  99     if (signatureCache.Get(entry)) {
 100         if (!store) {
 101             signatureCache.Erase(entry);
 102         }
 103         return true;
 104     }
 105
 106     if (!TransactionSignatureChecker::VerifySignature(vchSig, pubkey, sighash))
 107         return false;
 108
 109     if (store) {
 110         signatureCache.Set(entry);
 111     }
 112     return true;
 113 }