Policy: MOVEONLY: 3 functions to policy.o:

- [script/standard.o] IsStandard
- [main.o] IsStandardTx
- [main.o] AreInputsStandard

Also, don't use namespace std in policy.cpp

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