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Merge bitcoin#13194: Remove template matching and pseudo opcodes
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c814e2e Remove template matching and pseudo opcodes (Pieter Wuille)

Pull request description:

  The current code contains a rather complex script template matching engine, which is only used for 3 particular script types (P2PK, P2PKH, multisig). The first two of these are trivial to match for otherwise, and a specialized matcher for multisig is both more compact and more efficient than a generic one.

  The goal is being more flexible, so that for example larger standard multisigs inside SegWit outputs are easier to implement.

  As a side-effect, it also gets rid of the pseudo opcodes hack.

Tree-SHA512: 643b409c5c36821519f613a43efd399af0ec99b6131f35cd4024decfb2d483d719e0e921cd088bc9832a7ac797cb4a6b1158b8574c82f7fbebb75f1b31b359df
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@laanwj
laanwj committed May 30, 2018
2 parents 25d2df2 + c814e2e commit fd96d54
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Showing 4 changed files with 66 additions and 103 deletions.
8 changes: 4 additions & 4 deletions src/pubkey.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,10 +33,10 @@ class CPubKey
/**
* secp256k1:
*/
static const unsigned int PUBLIC_KEY_SIZE = 65;
static const unsigned int COMPRESSED_PUBLIC_KEY_SIZE = 33;
static const unsigned int SIGNATURE_SIZE = 72;
static const unsigned int COMPACT_SIGNATURE_SIZE = 65;
static constexpr unsigned int PUBLIC_KEY_SIZE = 65;
static constexpr unsigned int COMPRESSED_PUBLIC_KEY_SIZE = 33;
static constexpr unsigned int SIGNATURE_SIZE = 72;
static constexpr unsigned int COMPACT_SIGNATURE_SIZE = 65;
/**
* see www.keylength.com
* script supports up to 75 for single byte push
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5 changes: 0 additions & 5 deletions src/script/script.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -141,11 +141,6 @@ const char* GetOpName(opcodetype opcode)

case OP_INVALIDOPCODE : return "OP_INVALIDOPCODE";

// Note:
// The template matching params OP_SMALLINTEGER/etc are defined in opcodetype enum
// as kind of implementation hack, they are *NOT* real opcodes. If found in real
// Script, just let the default: case deal with them.

default:
return "OP_UNKNOWN";
}
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7 changes: 0 additions & 7 deletions src/script/script.h
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Original file line number Diff line number Diff line change
Expand Up @@ -181,13 +181,6 @@ enum opcodetype
OP_NOP9 = 0xb8,
OP_NOP10 = 0xb9,


// template matching params
OP_SMALLINTEGER = 0xfa,
OP_PUBKEYS = 0xfb,
OP_PUBKEYHASH = 0xfd,
OP_PUBKEY = 0xfe,

OP_INVALIDOPCODE = 0xff,
};

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149 changes: 62 additions & 87 deletions src/script/standard.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,22 +35,54 @@ const char* GetTxnOutputType(txnouttype t)
return nullptr;
}

bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet)
static bool MatchPayToPubkey(const CScript& script, valtype& pubkey)
{
// Templates
static std::multimap<txnouttype, CScript> mTemplates;
if (mTemplates.empty())
{
// Standard tx, sender provides pubkey, receiver adds signature
mTemplates.insert(std::make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
if (script.size() == CPubKey::PUBLIC_KEY_SIZE + 2 && script[0] == CPubKey::PUBLIC_KEY_SIZE && script.back() == OP_CHECKSIG) {
pubkey = valtype(script.begin() + 1, script.begin() + CPubKey::PUBLIC_KEY_SIZE + 1);
return CPubKey::ValidSize(pubkey);
}
if (script.size() == CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 2 && script[0] == CPubKey::COMPRESSED_PUBLIC_KEY_SIZE && script.back() == OP_CHECKSIG) {
pubkey = valtype(script.begin() + 1, script.begin() + CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 1);
return CPubKey::ValidSize(pubkey);
}
return false;
}

// Bitcoin address tx, sender provides hash of pubkey, receiver provides signature and pubkey
mTemplates.insert(std::make_pair(TX_PUBKEYHASH, CScript() << OP_DUP << OP_HASH160 << OP_PUBKEYHASH << OP_EQUALVERIFY << OP_CHECKSIG));
static bool MatchPayToPubkeyHash(const CScript& script, valtype& pubkeyhash)
{
if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160 && script[2] == 20 && script[23] == OP_EQUALVERIFY && script[24] == OP_CHECKSIG) {
pubkeyhash = valtype(script.begin () + 3, script.begin() + 23);
return true;
}
return false;
}

/** Test for "small positive integer" script opcodes - OP_1 through OP_16. */
static constexpr bool IsSmallInteger(opcodetype opcode)
{
return opcode >= OP_1 && opcode <= OP_16;
}

// Sender provides N pubkeys, receivers provides M signatures
mTemplates.insert(std::make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));
static bool MatchMultisig(const CScript& script, unsigned int& required, std::vector<valtype>& pubkeys)
{
opcodetype opcode;
valtype data;
CScript::const_iterator it = script.begin();
if (script.size() < 1 || script.back() != OP_CHECKMULTISIG) return false;

if (!script.GetOp(it, opcode, data) || !IsSmallInteger(opcode)) return false;
required = CScript::DecodeOP_N(opcode);
while (script.GetOp(it, opcode, data) && CPubKey::ValidSize(data)) {
pubkeys.emplace_back(std::move(data));
}
if (!IsSmallInteger(opcode)) return false;
unsigned int keys = CScript::DecodeOP_N(opcode);
if (pubkeys.size() != keys || keys < required) return false;
return (it + 1 == script.end());
}

bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet)
{
vSolutionsRet.clear();

// Shortcut for pay-to-script-hash, which are more constrained than the other types:
Expand Down Expand Up @@ -95,84 +127,27 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::v
return true;
}

// Scan templates
const CScript& script1 = scriptPubKey;
for (const std::pair<txnouttype, CScript>& tplate : mTemplates)
{
const CScript& script2 = tplate.second;
vSolutionsRet.clear();
std::vector<unsigned char> data;
if (MatchPayToPubkey(scriptPubKey, data)) {
typeRet = TX_PUBKEY;
vSolutionsRet.push_back(std::move(data));
return true;
}

opcodetype opcode1, opcode2;
std::vector<unsigned char> vch1, vch2;
if (MatchPayToPubkeyHash(scriptPubKey, data)) {
typeRet = TX_PUBKEYHASH;
vSolutionsRet.push_back(std::move(data));
return true;
}

// Compare
CScript::const_iterator pc1 = script1.begin();
CScript::const_iterator pc2 = script2.begin();
while (true)
{
if (pc1 == script1.end() && pc2 == script2.end())
{
// Found a match
typeRet = tplate.first;
if (typeRet == TX_MULTISIG)
{
// Additional checks for TX_MULTISIG:
unsigned char m = vSolutionsRet.front()[0];
unsigned char n = vSolutionsRet.back()[0];
if (m < 1 || n < 1 || m > n || vSolutionsRet.size()-2 != n)
return false;
}
return true;
}
if (!script1.GetOp(pc1, opcode1, vch1))
break;
if (!script2.GetOp(pc2, opcode2, vch2))
break;

// Template matching opcodes:
if (opcode2 == OP_PUBKEYS)
{
while (CPubKey::ValidSize(vch1))
{
vSolutionsRet.push_back(vch1);
if (!script1.GetOp(pc1, opcode1, vch1))
break;
}
if (!script2.GetOp(pc2, opcode2, vch2))
break;
// Normal situation is to fall through
// to other if/else statements
}

if (opcode2 == OP_PUBKEY)
{
if (!CPubKey::ValidSize(vch1))
break;
vSolutionsRet.push_back(vch1);
}
else if (opcode2 == OP_PUBKEYHASH)
{
if (vch1.size() != sizeof(uint160))
break;
vSolutionsRet.push_back(vch1);
}
else if (opcode2 == OP_SMALLINTEGER)
{ // Single-byte small integer pushed onto vSolutions
if (opcode1 == OP_0 ||
(opcode1 >= OP_1 && opcode1 <= OP_16))
{
char n = (char)CScript::DecodeOP_N(opcode1);
vSolutionsRet.push_back(valtype(1, n));
}
else
break;
}
else if (opcode1 != opcode2 || vch1 != vch2)
{
// Others must match exactly
break;
}
}
unsigned int required;
std::vector<std::vector<unsigned char>> keys;
if (MatchMultisig(scriptPubKey, required, keys)) {
typeRet = TX_MULTISIG;
vSolutionsRet.push_back({static_cast<unsigned char>(required)}); // safe as required is in range 1..16
vSolutionsRet.insert(vSolutionsRet.end(), keys.begin(), keys.end());
vSolutionsRet.push_back({static_cast<unsigned char>(keys.size())}); // safe as size is in range 1..16
return true;
}

vSolutionsRet.clear();
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