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Add SCRIPT_VERIFY_MINIMALDATA (BIP62 rules 3 and 4)

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Also use the new flag as a standard rule, and replace the IsCanonicalPush
standardness check with it (as it is more complete).
This commit is contained in:
Pieter Wuille
2014-10-08 18:48:59 -07:00
parent d752ba86c1
commit 698c6abb25
11 changed files with 101 additions and 59 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
src/script/interpreter.cpp
View File

@@ -157,6 +157,29 @@ bool static CheckPubKeyEncoding(const valtype &vchSig, unsigned int flags) {
return true;
}
bool static CheckMinimalPush(const valtype& data, opcodetype opcode) {
if (data.size() == 0) {
// Could have used OP_0.
return opcode == OP_0;
} else if (data.size() == 1 && data[0] >= 1 && data[0] <= 16) {
// Could have used OP_1 .. OP_16.
return opcode == OP_1 + (data[0] - 1);
} else if (data.size() == 1 && data[0] == 0x81) {
// Could have used OP_1NEGATE.
return opcode == OP_1NEGATE;
} else if (data.size() <= 75) {
// Could have used a direct push (opcode indicating number of bytes pushed + those bytes).
return opcode == data.size();
} else if (data.size() <= 255) {
// Could have used OP_PUSHDATA.
return opcode == OP_PUSHDATA1;
} else if (data.size() <= 65535) {
// Could have used OP_PUSHDATA2.
return opcode == OP_PUSHDATA2;
}
return true;
}
bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker)
{
CScript::const_iterator pc = script.begin();
@@ -169,6 +192,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
if (script.size() > 10000)
return false;
int nOpCount = 0;
bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0;
try
{
@@ -205,9 +229,12 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
opcode == OP_RSHIFT)
return false; // Disabled opcodes.
if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4)
if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4) {
if (fRequireMinimal && !CheckMinimalPush(vchPushValue, opcode)) {
return false;
}
stack.push_back(vchPushValue);
else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
} else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
switch (opcode)
{
//
@@ -234,6 +261,8 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
// ( -- value)
CScriptNum bn((int)opcode - (int)(OP_1 - 1));
stack.push_back(bn.getvch());
// The result of these opcodes should always be the minimal way to push the data
// they push, so no need for a CheckMinimalPush here.
}
break;
@@ -458,7 +487,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
// (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
if (stack.size() < 2)
return false;
int n = CScriptNum(stacktop(-1)).getint();
int n = CScriptNum(stacktop(-1), fRequireMinimal).getint();
popstack(stack);
if (n < 0 || n >= (int)stack.size())
return false;
@@ -557,7 +586,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
// (in -- out)
if (stack.size() < 1)
return false;
CScriptNum bn(stacktop(-1));
CScriptNum bn(stacktop(-1), fRequireMinimal);
switch (opcode)
{
case OP_1ADD: bn += bnOne; break;
@@ -590,8 +619,8 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
// (x1 x2 -- out)
if (stack.size() < 2)
return false;
CScriptNum bn1(stacktop(-2));
CScriptNum bn2(stacktop(-1));
CScriptNum bn1(stacktop(-2), fRequireMinimal);
CScriptNum bn2(stacktop(-1), fRequireMinimal);
CScriptNum bn(0);
switch (opcode)
{
@@ -635,9 +664,9 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
// (x min max -- out)
if (stack.size() < 3)
return false;
CScriptNum bn1(stacktop(-3));
CScriptNum bn2(stacktop(-2));
CScriptNum bn3(stacktop(-1));
CScriptNum bn1(stacktop(-3), fRequireMinimal);
CScriptNum bn2(stacktop(-2), fRequireMinimal);
CScriptNum bn3(stacktop(-1), fRequireMinimal);
bool fValue = (bn2 <= bn1 && bn1 < bn3);
popstack(stack);
popstack(stack);
@@ -727,7 +756,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
if ((int)stack.size() < i)
return false;
int nKeysCount = CScriptNum(stacktop(-i)).getint();
int nKeysCount = CScriptNum(stacktop(-i), fRequireMinimal).getint();
if (nKeysCount < 0 || nKeysCount > 20)
return false;
nOpCount += nKeysCount;
@@ -738,7 +767,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
if ((int)stack.size() < i)
return false;
int nSigsCount = CScriptNum(stacktop(-i)).getint();
int nSigsCount = CScriptNum(stacktop(-i), fRequireMinimal).getint();
if (nSigsCount < 0 || nSigsCount > nKeysCount)
return false;
int isig = ++i;

7
src/script/interpreter.h
View File

@@ -49,6 +49,13 @@ enum
// Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),
// Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
// pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
// any other push causes the script to fail (BIP62 rule 3).
// In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
// (softfork safe)
SCRIPT_VERIFY_MINIMALDATA = (1U << 6)
};
uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);

29
src/script/script.cpp
View File

@@ -12,7 +12,7 @@ namespace {
inline std::string ValueString(const std::vector<unsigned char>& vch)
{
if (vch.size() <= 4)
return strprintf("%d", CScriptNum(vch).getint());
return strprintf("%d", CScriptNum(vch, false).getint());
else
return HexStr(vch);
}
@@ -238,33 +238,6 @@ bool CScript::IsPushOnly() const
return true;
}
bool CScript::HasCanonicalPushes() const
{
const_iterator pc = begin();
while (pc < end())
{
opcodetype opcode;
std::vector<unsigned char> data;
if (!GetOp(pc, opcode, data))
return false;
if (opcode > OP_16)
continue;
if (opcode < OP_PUSHDATA1 && opcode > OP_0 && (data.size() == 1 && data[0] <= 16))
// Could have used an OP_n code, rather than a 1-byte push.
return false;
if (opcode == OP_PUSHDATA1 && data.size() < OP_PUSHDATA1)
// Could have used a normal n-byte push, rather than OP_PUSHDATA1.
return false;
if (opcode == OP_PUSHDATA2 && data.size() <= 0xFF)
// Could have used an OP_PUSHDATA1.
return false;
if (opcode == OP_PUSHDATA4 && data.size() <= 0xFFFF)
// Could have used an OP_PUSHDATA2.
return false;
}
return true;
}
std::string CScript::ToString() const
{
std::string str;

18
src/script/script.h
View File

@@ -192,10 +192,14 @@ public:
m_value = n;
}
explicit CScriptNum(const std::vector<unsigned char>& vch)
explicit CScriptNum(const std::vector<unsigned char>& vch, bool fRequireMinimal)
{
if (vch.size() > nMaxNumSize)
throw scriptnum_error("CScriptNum(const std::vector<unsigned char>&) : overflow");
if (vch.size() > nMaxNumSize) {
throw scriptnum_error("script number overflow");
}
if (fRequireMinimal && vch.size() > 0 && (vch.back() & 0x7f) == 0 && (vch.size() <= 1 || (vch[vch.size() - 2] & 0x80) == 0)) {
throw scriptnum_error("non-minimally encoded script number");
}
m_value = set_vch(vch);
}
@@ -319,7 +323,6 @@ private:
int64_t m_value;
};
/** Serialized script, used inside transaction inputs and outputs */
class CScript : public std::vector<unsigned char>
{
@@ -330,6 +333,10 @@ protected:
{
push_back(n + (OP_1 - 1));
}
else if (n == 0)
{
push_back(OP_0);
}
else
{
*this << CScriptNum::serialize(n);
@@ -554,9 +561,6 @@ public:
// Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical).
bool IsPushOnly() const;
// Called by IsStandardTx.
bool HasCanonicalPushes() const;
// Returns whether the script is guaranteed to fail at execution,
// regardless of the initial stack. This allows outputs to be pruned
// instantly when entering the UTXO set.

1
src/script/standard.h
View File

@@ -41,6 +41,7 @@ static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
// blocks and we must accept those blocks.
static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
SCRIPT_VERIFY_STRICTENC |
SCRIPT_VERIFY_MINIMALDATA |
SCRIPT_VERIFY_NULLDUMMY;
// For convenience, standard but not mandatory verify flags.