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-rw-r--r--src/policy/policy.cpp178
-rw-r--r--src/policy/policy.h17
2 files changed, 195 insertions, 0 deletions
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
new file mode 100644
index 0000000000..169fef4af4
--- /dev/null
+++ b/src/policy/policy.cpp
@@ -0,0 +1,178 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2014 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// NOTE: This file is intended to be customised by the end user, and includes only local node policy logic
+
+#include "policy/policy.h"
+
+#include "main.h"
+#include "tinyformat.h"
+#include "util.h"
+#include "utilstrencodings.h"
+
+#include <boost/foreach.hpp>
+
+ /**
+ * Check transaction inputs to mitigate two
+ * potential denial-of-service attacks:
+ *
+ * 1. scriptSigs with extra data stuffed into them,
+ * not consumed by scriptPubKey (or P2SH script)
+ * 2. P2SH scripts with a crazy number of expensive
+ * CHECKSIG/CHECKMULTISIG operations
+ *
+ * Check transaction inputs, and make sure any
+ * pay-to-script-hash transactions are evaluating IsStandard scripts
+ *
+ * Why bother? To avoid denial-of-service attacks; an attacker
+ * can submit a standard HASH... OP_EQUAL transaction,
+ * which will get accepted into blocks. The redemption
+ * script can be anything; an attacker could use a very
+ * expensive-to-check-upon-redemption script like:
+ * DUP CHECKSIG DROP ... repeated 100 times... OP_1
+ */
+
+bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType)
+{
+ std::vector<std::vector<unsigned char> > vSolutions;
+ if (!Solver(scriptPubKey, whichType, vSolutions))
+ return false;
+
+ if (whichType == TX_MULTISIG)
+ {
+ unsigned char m = vSolutions.front()[0];
+ unsigned char n = vSolutions.back()[0];
+ // Support up to x-of-3 multisig txns as standard
+ if (n < 1 || n > 3)
+ return false;
+ if (m < 1 || m > n)
+ return false;
+ }
+
+ return whichType != TX_NONSTANDARD;
+}
+
+bool IsStandardTx(const CTransaction& tx, std::string& reason)
+{
+ if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) {
+ reason = "version";
+ return false;
+ }
+
+ // Extremely large transactions with lots of inputs can cost the network
+ // almost as much to process as they cost the sender in fees, because
+ // computing signature hashes is O(ninputs*txsize). Limiting transactions
+ // to MAX_STANDARD_TX_SIZE mitigates CPU exhaustion attacks.
+ unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);
+ if (sz >= MAX_STANDARD_TX_SIZE) {
+ reason = "tx-size";
+ return false;
+ }
+
+ BOOST_FOREACH(const CTxIn& txin, tx.vin)
+ {
+ // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
+ // keys. (remember the 520 byte limit on redeemScript size) That works
+ // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)+3=1627
+ // bytes of scriptSig, which we round off to 1650 bytes for some minor
+ // future-proofing. That's also enough to spend a 20-of-20
+ // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
+ // considered standard)
+ if (txin.scriptSig.size() > 1650) {
+ reason = "scriptsig-size";
+ return false;
+ }
+ if (!txin.scriptSig.IsPushOnly()) {
+ reason = "scriptsig-not-pushonly";
+ return false;
+ }
+ }
+
+ unsigned int nDataOut = 0;
+ txnouttype whichType;
+ BOOST_FOREACH(const CTxOut& txout, tx.vout) {
+ if (!::IsStandard(txout.scriptPubKey, whichType)) {
+ reason = "scriptpubkey";
+ return false;
+ }
+
+ if (whichType == TX_NULL_DATA)
+ nDataOut++;
+ else if ((whichType == TX_MULTISIG) && (!fIsBareMultisigStd)) {
+ reason = "bare-multisig";
+ return false;
+ } else if (txout.IsDust(::minRelayTxFee)) {
+ reason = "dust";
+ return false;
+ }
+ }
+
+ // only one OP_RETURN txout is permitted
+ if (nDataOut > 1) {
+ reason = "multi-op-return";
+ return false;
+ }
+
+ return true;
+}
+
+bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
+{
+ if (tx.IsCoinBase())
+ return true; // Coinbases don't use vin normally
+
+ for (unsigned int i = 0; i < tx.vin.size(); i++)
+ {
+ const CTxOut& prev = mapInputs.GetOutputFor(tx.vin[i]);
+
+ std::vector<std::vector<unsigned char> > vSolutions;
+ txnouttype whichType;
+ // get the scriptPubKey corresponding to this input:
+ const CScript& prevScript = prev.scriptPubKey;
+ if (!Solver(prevScript, whichType, vSolutions))
+ return false;
+ int nArgsExpected = ScriptSigArgsExpected(whichType, vSolutions);
+ if (nArgsExpected < 0)
+ return false;
+
+ // Transactions with extra stuff in their scriptSigs are
+ // non-standard. Note that this EvalScript() call will
+ // be quick, because if there are any operations
+ // beside "push data" in the scriptSig
+ // IsStandardTx() will have already returned false
+ // and this method isn't called.
+ std::vector<std::vector<unsigned char> > stack;
+ if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker()))
+ return false;
+
+ if (whichType == TX_SCRIPTHASH)
+ {
+ if (stack.empty())
+ return false;
+ CScript subscript(stack.back().begin(), stack.back().end());
+ std::vector<std::vector<unsigned char> > vSolutions2;
+ txnouttype whichType2;
+ if (Solver(subscript, whichType2, vSolutions2))
+ {
+ int tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
+ if (tmpExpected < 0)
+ return false;
+ nArgsExpected += tmpExpected;
+ }
+ else
+ {
+ // Any other Script with less than 15 sigops OK:
+ unsigned int sigops = subscript.GetSigOpCount(true);
+ // ... extra data left on the stack after execution is OK, too:
+ return (sigops <= MAX_P2SH_SIGOPS);
+ }
+ }
+
+ if (stack.size() != (unsigned int)nArgsExpected)
+ return false;
+ }
+
+ return true;
+}
diff --git a/src/policy/policy.h b/src/policy/policy.h
index 48e192d559..1551aecde8 100644
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -10,6 +10,10 @@
#include "script/interpreter.h"
#include "script/standard.h"
+#include <string>
+
+class CCoinsViewCache;
+
/** Default for -blockmaxsize and -blockminsize, which control the range of sizes the mining code will create **/
static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
static const unsigned int DEFAULT_BLOCK_MIN_SIZE = 0;
@@ -38,4 +42,17 @@ static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY
/** For convenience, standard but not mandatory verify flags. */
static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
+bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType);
+ /**
+ * Check for standard transaction types
+ * @return True if all outputs (scriptPubKeys) use only standard transaction forms
+ */
+bool IsStandardTx(const CTransaction& tx, std::string& reason);
+ /**
+ * Check for standard transaction types
+ * @param[in] mapInputs Map of previous transactions that have outputs we're spending
+ * @return True if all inputs (scriptSigs) use only standard transaction forms
+ */
+bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs);
+
#endif // BITCOIN_POLICY_H