Audit/oz m05 merkletrie bug 193 (#102)

* add revert for bad prefix

* sad path merkletrie tests

* bad node prefix test

packages/contracts/contracts/optimistic-ethereum/libraries/trie/Lib_MerkleTrie.sol

@@ -328,6 +328,8 @@ library Lib_MerkleTrie {
                         currentKeyIncrement = sharedNibbleLength;
                         continue;
                     }
+                } else {
+                    revert("Received a node with an unknown prefix");
                 }
             } else {
                 revert("Received an unparseable node.");

packages/contracts/test/contracts/libraries/trie/Lib_MerkleTrie.spec.ts

 import { expect } from '../../../setup'
 
 /* External Imports */
+import * as rlp from 'rlp'
 import { ethers } from '@nomiclabs/buidler'
 import { Contract } from 'ethers'
 
 /* Internal Imports */
-import { TrieTestGenerator } from '../../../helpers'
+import { toHexString, TrieTestGenerator } from '../../../helpers'
 
 const NODE_COUNTS = [1, 2, 128]
 
@@ -107,13 +108,61 @@ describe('Lib_MerkleTrie', () => {
         ) {
           it(`should correctly get the value of node #${i}`, async () => {
             const test = await generator.makeInclusionProofTest(i)
-
             expect(
               await Lib_MerkleTrie.get(test.key, test.proof, test.root)
             ).to.deep.equal([true, test.val])
           })
+          if (i > 3) {
+            it(`should revert when the proof node does not pass the root check`, async () => {
+              const test = await generator.makeInclusionProofTest(i-1)
+              const test2 = await generator.makeInclusionProofTest(i-2)
+              await expect (
+                Lib_MerkleTrie.get(test2.key, test.proof, test.root)
+              ).to.be.revertedWith("Invalid large internal hash")
+            })
+            it(`should revert when the first proof element is not the root node`, async () => {
+              const test = await generator.makeInclusionProofTest(0)
+              let decodedProof = rlp.decode(test.proof)
+              decodedProof[0].write('abcd', 8) // change the 1st element (root) of the proof
+              const badProof = rlp.encode(decodedProof as rlp.Input)
+              await expect (
+                Lib_MerkleTrie.get(test.key, badProof, test.root)
+              ).to.be.revertedWith("Invalid root hash")
+            })
+            it(`should be false when calling get on an incorrect key`, async () => {
+              const test = await generator.makeInclusionProofTest(i-1)
+              let newKey = test.key.slice(0, test.key.length - 8)
+              newKey = newKey.concat('88888888')
+              expect (
+                await Lib_MerkleTrie.get(newKey, test.proof, test.root)
+              ).to.deep.equal([false, '0x'])
+            })
+          }
         }
       })
     }
   })
-})
+
+  describe(`inside a trie with one node`, () => {
+    let generator: TrieTestGenerator
+    const nodeCount = 1
+    before(async () => {
+      generator = await TrieTestGenerator.fromRandom({
+        seed: `seed.get.${nodeCount}`,
+        nodeCount,
+        secure: false,
+      })
+    })
+
+    it(`should revert on an incorrect proof node prefix`, async () => {
+      const test = await generator.makeInclusionProofTest(0)
+      let decodedProof = rlp.decode(test.proof)
+      decodedProof[0].write('a', 3) // change the prefix
+      test.root = ethers.utils.keccak256(toHexString(decodedProof[0]));
+      const badProof = rlp.encode(decodedProof as rlp.Input)
+      await expect (
+        Lib_MerkleTrie.get(test.key, badProof, test.root)
+      ).to.be.revertedWith("Received a node with an unknown prefix")
+    })
+  })
+})
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