VM: Strip zeros when putting contract storage in StateManager

packages/vm/lib/state/stateManager.ts

@@ -1,6 +1,6 @@
 const Set = require('core-js-pure/es/set')
 import { SecureTrie as Trie } from 'merkle-patricia-tree'
-import { BN, toBuffer, keccak256, KECCAK256_NULL } from 'ethereumjs-util'
+import { BN, toBuffer, keccak256, KECCAK256_NULL, unpadBuffer } from 'ethereumjs-util'
 import { encode, decode } from 'rlp'
 import Common from '@ethereumjs/common'
 import { genesisStateByName } from '@ethereumjs/common/dist/genesisStates'
@@ -276,13 +276,19 @@ export default class DefaultStateManager implements StateManager {
    * corresponding to `address` at the provided `key`.
    * @param address -  Address to set a storage value for
    * @param key - Key to set the value at. Must be 32 bytes long.
-   * @param value - Value to set at `key` for account corresponding to `address`
+   * @param value - Value to set at `key` for account corresponding to `address`. Cannot be more than 32 bytes. Leading zeros are stripped. If it is a empty or filled with zeros, deletes the value.
    */
   async putContractStorage(address: Buffer, key: Buffer, value: Buffer): Promise<void> {
     if (key.length !== 32) {
       throw new Error('Storage key must be 32 bytes long')
     }
 
+    if (value.length > 32) {
+      throw new Error('Storage value cannot be longer than 32 bytes')
+    }
+
+    value = unpadBuffer(value)
+
     await this._modifyContractStorage(address, async (storageTrie, done) => {
       if (value && value.length) {
         // format input
@@ -415,7 +421,7 @@ export default class DefaultStateManager implements StateManager {
   }
 
   /**
-   * Dumps the the storage values for an `account` specified by `address`.
+   * Dumps the RLP-encoded storage values for an `account` specified by `address`.
    * @param address - The address of the `account` to return storage for
    * @returns {Promise<StorageDump>} - The state of the account as an `Object` map.
    * Keys are are the storage keys, values are the storage values as strings.

packages/vm/tests/api/state/stateManager.spec.ts

@@ -1,5 +1,5 @@
 import * as tape from 'tape'
-import { BN, toBuffer, keccak256, KECCAK256_RLP } from 'ethereumjs-util'
+import { BN, toBuffer, keccak256, KECCAK256_RLP, unpadBuffer, zeros } from 'ethereumjs-util'
 import Common from '@ethereumjs/common'
 import Account from '@ethereumjs/account'
 import { DefaultStateManager } from '../../../lib/state'
@@ -409,3 +409,81 @@ tape('StateManager - Contract code', (tester) => {
     t.end()
   })
 })
+
+tape('StateManager - Contract storage', (tester) => {
+  const it = tester.test
+
+  it('should throw on storage values larger than 32 bytes', async (t) => {
+    t.plan(1)
+    const stateManager = new DefaultStateManager()
+    const address = zeros(20)
+    const key = zeros(32)
+    const value = Buffer.from('aa'.repeat(33), 'hex')
+    try {
+      await stateManager.putContractStorage(address, key, value)
+      t.fail('did not throw')
+    } catch (e) {
+      t.pass('threw on trying to set storage values larger than 32 bytes')
+    }
+    t.end()
+  })
+
+  it('should strip zeros of storage values', async (t) => {
+    const stateManager = new DefaultStateManager()
+    const address = zeros(20)
+
+    const key0 = zeros(32)
+    const value0 = Buffer.from('00' + 'aa'.repeat(30), 'hex') // put a value of 31-bytes length with a leading zero byte
+    const expect0 = unpadBuffer(value0)
+    await stateManager.putContractStorage(address, key0, value0)
+    const slot0 = await stateManager.getContractStorage(address, key0)
+    t.ok(slot0.equals(expect0), 'value of 31 bytes padded correctly')
+
+    const key1 = Buffer.concat([zeros(31), Buffer.from('01', 'hex')])
+    const value1 = Buffer.from('0000' + 'aa'.repeat(1), 'hex') // put a value of 1-byte length with two leading zero bytes
+    const expect1 = unpadBuffer(value1)
+    await stateManager.putContractStorage(address, key1, value1)
+    const slot1 = await stateManager.getContractStorage(address, key1)
+
+    t.ok(slot1.equals(expect1), 'value of 1 byte padded correctly')
+    t.end()
+  })
+
+  it('should delete storage values which only consist of zero bytes', async (t) => {
+    const address = zeros(20)
+    const key = zeros(32)
+    const startValue = Buffer.from('01', 'hex')
+
+    const zeroLengths = [0, 1, 31, 32] // checks for arbitrary-length zeros
+    t.plan(zeroLengths.length)
+
+    for (let length of zeroLengths) {
+      const stateManager = new DefaultStateManager()
+      const value = zeros(length)
+      await stateManager.putContractStorage(address, key, startValue)
+      const currentValue = await stateManager.getContractStorage(address, key)
+      if (!currentValue.equals(startValue)) {
+        // sanity check
+        t.fail('contract value not set correctly')
+      } else {
+        // delete the value
+        await stateManager.putContractStorage(address, key, value)
+        const deleted = await stateManager.getContractStorage(address, key)
+        t.ok(deleted.equals(zeros(0)), 'the storage key should be deleted')
+      }
+    }
+    t.end()
+  })
+
+  it('should not strip trailing zeros', async (t) => {
+    const address = zeros(20)
+    const key = zeros(32)
+    const value = Buffer.from('0000aabb00', 'hex')
+    const expect = Buffer.from('aabb00', 'hex')
+    const stateManager = new DefaultStateManager()
+    await stateManager.putContractStorage(address, key, value)
+    const contractValue = await stateManager.getContractStorage(address, key)
+    t.ok(contractValue.equals(expect), 'trailing zeros are not stripped')
+    t.end()
+  })
+})