transaction: add SIGHASH_* implementations

Author: dcousens

src/transaction.js

@@ -177,6 +177,8 @@ Transaction.prototype.clone = function () {
   return newTx
 }
 
+var one = new Buffer('0000000000000000000000000000000000000000000000000000000000000001', 'hex')
+
 /**
  * Hash transaction for signing a specific input.
  *
@@ -191,33 +193,71 @@ Transaction.prototype.hashForSignature = function (inIndex, prevOutScript, hashT
   typeForce('Number', hashType)
 
   assert(inIndex >= 0, 'Invalid vin index')
-  assert(inIndex < this.ins.length, 'Invalid vin index')
+
+  // https://github.com/bitcoin/bitcoin/blob/master/src/test/sighash_tests.cpp#L29
+  if (inIndex >= this.ins.length) return one
 
   var txTmp = this.clone()
+
+  // in case concatenating two scripts ends up with two codeseparators,
+  // or an extra one at the end, this prevents all those possible incompatibilities.
   var hashScript = prevOutScript.without(opcodes.OP_CODESEPARATOR)
+  var i
 
-  // Blank out other inputs' signatures
-  txTmp.ins.forEach(function (txIn) {
-    txIn.script = Script.EMPTY
-  })
+  // blank out other inputs' signatures
+  txTmp.ins.forEach(function (input) { input.script = Script.EMPTY })
   txTmp.ins[inIndex].script = hashScript
 
-  var hashTypeModifier = hashType & 0x1f
+  // blank out some of the inputs
+  if ((hashType & 0x1f) === Transaction.SIGHASH_NONE) {
+    // wildcard payee
+    txTmp.outs = []
+
+    // let the others update at will
+    txTmp.ins.forEach(function (input, i) {
+      if (i !== inIndex) {
+        input.sequence = 0
+      }
+    })
+
+  } else if ((hashType & 0x1f) === Transaction.SIGHASH_SINGLE) {
+    var nOut = inIndex
+
+    // only lock-in the txout payee at same index as txIn
+    // https://github.com/bitcoin/bitcoin/blob/master/src/test/sighash_tests.cpp#L60
+    if (nOut >= this.outs.length) return one
+
+    txTmp.outs = txTmp.outs.slice(0, nOut + 1)
 
-  if (hashTypeModifier === Transaction.SIGHASH_NONE) {
-    assert(false, 'SIGHASH_NONE not yet supported')
-  } else if (hashTypeModifier === Transaction.SIGHASH_SINGLE) {
-    assert(false, 'SIGHASH_SINGLE not yet supported')
+    // blank all other outputs (clear scriptPubKey, value === -1)
+    var stubOut = {
+      script: Script.EMPTY,
+      valueBuffer: new Buffer('ffffffffffffffff', 'hex')
+    }
+
+    for (i = 0; i < nOut; i++) {
+      txTmp.outs[i] = stubOut
+    }
+
+    // let the others update at will
+    txTmp.ins.forEach(function (input, i) {
+      if (i !== inIndex) {
+        input.sequence = 0
+      }
+    })
   }
 
+  // blank out other inputs completely, not recommended for open transactions
   if (hashType & Transaction.SIGHASH_ANYONECANPAY) {
-    assert(false, 'SIGHASH_ANYONECANPAY not yet supported')
+    txTmp.ins[0] = txTmp.ins[inIndex]
+    txTmp.ins = txTmp.ins.slice(0, 1)
   }
 
-  var hashTypeBuffer = new Buffer(4)
-  hashTypeBuffer.writeInt32LE(hashType, 0)
+  // serialize and hash
+  var buffer = new Buffer(txTmp.byteLength() + 4)
+  buffer.writeInt32LE(hashType, buffer.length - 4)
+  txTmp.toBuffer().copy(buffer, 0)
 
-  var buffer = Buffer.concat([txTmp.toBuffer(), hashTypeBuffer])
   return crypto.hash256(buffer)
 }
 
@@ -267,7 +307,12 @@ Transaction.prototype.toBuffer = function () {
 
   writeVarInt(this.outs.length)
   this.outs.forEach(function (txOut) {
-    writeUInt64(txOut.value)
+    if (!txOut.valueBuffer) {
+      writeUInt64(txOut.value)
+    } else {
+      writeSlice(txOut.valueBuffer)
+    }
+
     writeVarInt(txOut.script.buffer.length)
     writeSlice(txOut.script.buffer)
   })