Add method to verify table proof

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.13.0 (Oct 5, 2018)
+
+* Add a new `verifyTable` method to verify table existence in the root tree. ([#138][pr-138])
+
 ## 0.12.5 (Oct 5, 2018)
 
 * Change package used to replace library version via Grunt. ([#137][pr-137])
@@ -145,6 +149,7 @@ matching [release 0.1][release-0.1] of the Exonum core repository.
 [release-0.7]: https://github.com/exonum/exonum/blob/master/CHANGELOG.md#07---2018-04-11
 [release-0.5]: https://github.com/exonum/exonum/blob/master/CHANGELOG.md#05---2018-01-30
 [release-0.1]: https://github.com/exonum/exonum/releases/tag/v0.1
+[pr-138]: https://github.com/exonum/exonum-client/pull/138
 [pr-137]: https://github.com/exonum/exonum-client/pull/137
 [pr-133]: https://github.com/exonum/exonum-client/pull/133
 [pr-126]: https://github.com/exonum/exonum-client/pull/126

README.md

@@ -25,7 +25,7 @@ Library compatibility with Exonum core:
 
 | JavaScript light client | Exonum core |
 |---|---|
-| 0.12.4 (latest) | 0.9.* |
+| 0.13.0 | 0.9.* |
 | 0.10.2 | 0.8.* |
 | 0.9.0 | 0.7.* |
 | 0.6.1 | 0.6.* |
@@ -56,6 +56,7 @@ Library compatibility with Exonum core:
   * [Map proof](#map-proof)
 * [Integrity checks](#integrity-checks)
   * [Verify block](#verify-block)
+  * [Verify table](#verify-table)
 * [Helpers](#helpers)
   * [Generate key pair](#generate-key-pair)
   * [Get random number](#get-random-number)
@@ -697,6 +698,23 @@ Returns `true` if verification is succeeded or `false` if it is failed.
 
 An example of [block verification](examples/block.md).
 
+### Verify table
+
+```javascript
+Exonum.verifyTable(proof, stateHash, serviceId, tableIndex)
+```
+
+Verify table existence in the root tree.
+
+Returns root hash for the table as hexadecimal `String`.
+
+| Argument | Description | Type |
+|---|---|---|
+| **proof** | The JSON presentation of the proof obtained from a full node. | `Object` |
+| **stateHash** | Hash of current blockchain state stored in each block. | `String` |
+| **serviceId** | [Service ID][docs:architecture:serialization:service-id]. | `Number` |
+| **tableIndex** | Table index. | `Number` |
+
 ## Helpers
 
 ### Generate key pair

package.json

@@ -1,6 +1,6 @@
 {
   "name": "exonum-client",
-  "version": "0.12.5",
+  "version": "0.13.0",
   "description": "Light Client for Exonum Blockchain",
   "main": "./lib/index.js",
   "engines": {

src/blockchain/index.js

@@ -2,3 +2,4 @@ export * from './merkle'
 export * from './merkle-patricia'
 export * from './block'
 export * from './transport'
+export * from './table'

src/blockchain/table.js

@@ -0,0 +1,43 @@
+import { Uint16 } from '../types/primitive'
+import { newType } from '../types/generic'
+import { Hash } from '../types/hexadecimal'
+import { MapProof } from './merkle-patricia'
+
+const TableKey = newType({
+  fields: [
+    { name: 'service_id', type: Uint16 },
+    { name: 'table_index', type: Uint16 }
+  ]
+})
+
+/**
+ * Validate path from tree root to some table
+ * @param {Object} proof
+ * @param {string} stateHash
+ * @param {number} serviceId
+ * @param {number} tableIndex
+ * @returns {string}
+ */
+export function verifyTable (proof, stateHash, serviceId, tableIndex) {
+  // calculate key of table in the root tree
+  const key = TableKey.hash({
+    service_id: serviceId,
+    table_index: tableIndex
+  })
+
+  // validate proof of table existence in root tree
+  const tableProof = new MapProof(proof, Hash, Hash)
+
+  if (tableProof.merkleRoot !== stateHash) {
+    throw new Error('Table proof is corrupted')
+  }
+
+  // get root hash of the table
+  const rootHash = tableProof.entries.get(key)
+
+  if (typeof rootHash === 'undefined') {
+    throw new Error('Table not found in the root tree')
+  }
+
+  return rootHash
+}

test/sources/blockchain.js

@@ -384,6 +384,69 @@ describe('Verify block of precommits', function () {
   })
 })
 
+describe('Verify table existence', function () {
+  const proof = {
+    entries: [
+      {
+        key: '775be457774803ff0221f0d18f407c9718a2f4c635445a691f6061bd5d651581',
+        value: '540c35c61837aa819986e137b6ae0091faa781419e8234802094ef77a2cdc293'
+      }
+    ],
+    proof: [
+      {
+        path: '0000101010101110110000001010110110011000000001100011001110110111000101011001101100100100000010011111001000011101110010101110111001111111101111101110100011111110000111011111101111110011011010100100110101110010101000101110101000100110011100100010101101100001',
+        hash: '0000000000000000000000000000000000000000000000000000000000000000'
+      },
+      {
+        path: '1101',
+        hash: '9d57d84328c5fce997b0dd0cf806c114a37ebf32bd1b966154244548206acd27'
+      },
+      {
+        path: '1110011011010101101110110100111000001000001001000000111111111111011100101101000011111100001100101111010010000011110111001010001101011101001010111011010011010000000111101000101000101011011010100001101110110001000001001011110010101000010101010010010100001010',
+        hash: '0000000000000000000000000000000000000000000000000000000000000000'
+      },
+      {
+        path: '1111101111111100100001100001100100100000100101011111010011011011000000101110101010011000101101000010001110111100111010110001001001010111111011100101000100111011010010100011110110010010001100010001011110100000001001000000001100101000000111011000100010011000',
+        hash: '15ca2aa05d8f054125ee327ac35805c5a20d9305aae10880dc56373219126a47'
+      }
+    ]
+  }
+  const serviceId = 130
+  const tableIndex = 0
+  const stateHash = 'dd09c5ec10fe7eb5d82aeabf362772440880394dfabb0a4c4cfbfdecc2d6bad7'
+  const rootHash = '540c35c61837aa819986e137b6ae0091faa781419e8234802094ef77a2cdc293'
+
+  it('should return root hash when valid proof', function () {
+    expect(Exonum.verifyTable(proof, stateHash, serviceId, tableIndex)).to.equals(rootHash)
+  })
+
+  it('should throw error when wrong service ID is passed', function () {
+    const endpoints = [null, false, 'Hello world', new Date(), {}, []]
+
+    endpoints.forEach(function (value) {
+      expect(() => Exonum.verifyTable(proof, stateHash, value, tableIndex))
+        .to.throw(Error, `Uint16 of wrong type is passed: ${value}`)
+    })
+  })
+
+  it('should throw error when wrong table index is passed', function () {
+    const endpoints = [null, false, 'Hello world', new Date(), {}, []]
+
+    endpoints.forEach(function (value) {
+      expect(() => Exonum.verifyTable(proof, stateHash, serviceId, value))
+        .to.throw(Error, `Uint16 of wrong type is passed: ${value}`)
+    })
+  })
+
+  it('should throw error when wrong proof is passed', function () {
+    const endpoints = [null, false, 42, 'Hello world', new Date(), {}, []]
+
+    endpoints.forEach(function (value) {
+      expect(() => Exonum.verifyTable(value, stateHash, serviceId, tableIndex)).to.throw(Error)
+    })
+  })
+})
+
 describe('Send transaction to the blockchain', function () {
   let sendFunds = Exonum.newMessage({
     protocol_version: 0,