introduce strict length consumption during decode

README.md

@@ -135,7 +135,7 @@ Only the non-redundant parts of a porcelain form of the objects are required to
  * [`BitcoinBlock#encode(args)`](#BitcoinBlock_encode)
  * [`BitcoinBlock.HASH_NO_WITNESS`](#BitcoinBlock__HASH_NO_WITNESS)
  * [`BitcoinBlock.fromPorcelain(porcelain)`](#BitcoinBlock__fromPorcelain)
- * [`BitcoinBlock.decode(bytes)`](#BitcoinBlock__decode)
+ * [`BitcoinBlock.decode(bytes, strictLengthUsage)`](#BitcoinBlock__decode)
  * [`BitcoinBlock.decodeBlockHeaderOnly(bytes)`](#BitcoinBlock__decodeBlockHeaderOnly)
  * [`class BitcoinTransaction`](#BitcoinTransaction)
    * [Constructor: `BitcoinTransaction()`](#BitcoinTransaction_new)
@@ -149,7 +149,7 @@ Only the non-redundant parts of a porcelain form of the objects are required to
  * [`BitcoinTransaction#encode(args)`](#BitcoinTransaction_encode)
  * [`BitcoinTransaction.isPorcelainSegWit(porcelain)`](#BitcoinTransaction__isPorcelainSegWit)
  * [`BitcoinTransaction.fromPorcelain(porcelain)`](#BitcoinTransaction__fromPorcelain)
- * [`BitcoinTransaction.decode(bytes)`](#BitcoinTransaction__decode)
+ * [`BitcoinTransaction.decode(bytes, strictLengthUsage)`](#BitcoinTransaction__decode)
  * [`class BitcoinTransactionIn`](#BitcoinTransactionIn)
    * [Constructor: `BitcoinTransactionIn(prevout, scriptSig, sequence)`](#BitcoinTransactionIn_new)
  * [`BitcoinTransactionIn#toPorcelain()`](#BitcoinTransactionIn_toPorcelain)
@@ -437,7 +437,7 @@ structure.
 **Return value**  _(`BitcoinBlock`)_
 
 <a name="BitcoinBlock__decode"></a>
-### `BitcoinBlock.decode(bytes)`
+### `BitcoinBlock.decode(bytes, strictLengthUsage)`
 
 Decode a [`BitcoinBlock`](#BitcoinBlock) from the raw bytes of the block. Such data
 in hex form is available directly from the bitcoin cli:
@@ -449,6 +449,10 @@ to parse just the 80-byte header data.
 **Parameters:**
 
 * **`bytes`** _(`Uint8Array|Buffer`)_: the raw bytes of the block to be decoded.
+* **`strictLengthUsage`** _(`boolean`)_: ensure that all bytes were consumed during decode.
+  This is useful when ensuring that bytes have been properly decoded where there is
+  uncertainty about whether the bytes represent a Block or not. Switch to `true` to be
+  sure.
 
 **Return value**  _(`BitcoinBlock`)_
 
@@ -644,7 +648,7 @@ a correct BitcoinTransaction. This could be one of:
 **Return value**  _(`BitcoinTransaction`)_
 
 <a name="BitcoinTransaction__decode"></a>
-### `BitcoinTransaction.decode(bytes)`
+### `BitcoinTransaction.decode(bytes, strictLengthUsage)`
 
 Decode a [`BitcoinTransaction`](#BitcoinTransaction) from the raw bytes of the transaction.
 Normally raw transaction data isn't available in detached form, although the
@@ -655,6 +659,10 @@ each element of the `tx` array. It may also come from the
 **Parameters:**
 
 * **`bytes`** _(`Uint8Array|Buffer`)_: the raw bytes of the transaction to be decoded.
+* **`strictLengthUsage`** _(`boolean`)_: ensure that all bytes were consumed during decode.
+  This is useful when ensuring that bytes have been properly decoded where there is
+  uncertainty about whether the bytes represent a Transaction or not. Switch to `true`
+  to be sure.
 
 **Return value**  _(`BitcoinTransaction`)_
 

bitcoin-block.js

@@ -6,12 +6,12 @@ const BitcoinOutPoint = require('./classes/OutPoint')
 const coding = require('./coding')(require('./classes/'))
 const { toHashHex, fromHashHex, COIN, dblSha2256, merkle, merkleRoot } = require('./classes/class-utils')
 
-BitcoinBlock.decode = function decodeBlock (buf) {
-  return coding.decodeType(buf, 'CBlockHeader')
+BitcoinBlock.decode = function decodeBlock (buf, strictLengthUsage) {
+  return coding.decodeType(buf, 'CBlockHeader', strictLengthUsage)
 }
 
-BitcoinBlock.decodeHeaderOnly = function decodeBlockHeaderOnly (buf) {
-  return coding.decodeType(buf, 'CBlockHeader__Only')
+BitcoinBlock.decodeHeaderOnly = function decodeBlockHeaderOnly (buf, strictLengthUsage) {
+  return coding.decodeType(buf, 'CBlockHeader__Only', strictLengthUsage)
 }
 
 BitcoinBlock.prototype.encode = function (...args) {
@@ -22,8 +22,8 @@ BitcoinBlock.BitcoinBlockHeaderOnly.prototype.encode = function (...args) {
   return Buffer.concat([...coding.encodeType(this, args)])
 }
 
-BitcoinTransaction.decode = function decodeTransaction (buf) {
-  return coding.decodeType(buf, 'CTransaction')
+BitcoinTransaction.decode = function decodeTransaction (buf, strictLengthUsage) {
+  return coding.decodeType(buf, 'CTransaction', strictLengthUsage)
 }
 
 BitcoinTransaction.prototype.encode = function (...args) {

classes/Block.js

@@ -480,6 +480,10 @@ module.exports.BitcoinBlockHeaderOnly = BitcoinBlockHeaderOnly
  * to parse just the 80-byte header data.
  *
  * @param {Uint8Array|Buffer} bytes - the raw bytes of the block to be decoded.
+ * @param {boolean} strictLengthUsage - ensure that all bytes were consumed during decode.
+ * This is useful when ensuring that bytes have been properly decoded where there is
+ * uncertainty about whether the bytes represent a Block or not. Switch to `true` to be
+ * sure.
  * @name BitcoinBlock.decode
  * @function
  * @returns {BitcoinBlock}

classes/Transaction.js

@@ -339,6 +339,10 @@ BitcoinTransaction.HASH_NO_WITNESS = HASH_NO_WITNESS
  * {@link BitcoinTransaction#encode} method.
  *
  * @param {Uint8Array|Buffer} bytes - the raw bytes of the transaction to be decoded.
+ * @param {boolean} strictLengthUsage - ensure that all bytes were consumed during decode.
+ * This is useful when ensuring that bytes have been properly decoded where there is
+ * uncertainty about whether the bytes represent a Transaction or not. Switch to `true`
+ * to be sure.
  * @name BitcoinTransaction.decode
  * @returns {BitcoinTransaction}
  * @function

coding.js

@@ -206,7 +206,7 @@ function isArrayType (typ) {
   return arrayDesc
 }
 
-function decodeType (buf, type) {
+function decodeType (buf, type, strictLengthUsage) {
   let pos = 0
   const state = {}
 
@@ -413,6 +413,9 @@ function decodeType (buf, type) {
   }
 
   const block = decoder.readType(type)
+  if (strictLengthUsage && pos !== buf.length) {
+    throw new Error('decode did not consume all available bytes as expected')
+  }
   return block
 }
 

test/test.js

@@ -197,7 +197,7 @@ function test (hash, block, expected) {
   // verify _only_ the first 80 bytes and that we can parse basic data
   verifyHeader(block, expected)
 
-  const decoded = BitcoinBlock.decode(block) // decode full block
+  const decoded = BitcoinBlock.decode(block, true) // decode full block, strict length consumption
 
   // ---------------------------------------------------------------------------
   // test the serialized minimum form, where the `tx` array is just the txids