Merkle Proof verification failed for a valid proof.

[0xsarvesh]

https://github.com/OpenSTFoundation/mosaic-contracts/blob/c48747a91746061fba73fc7a9189019d7b62fbbe/contracts/lib/MerklePatriciaProof.sol#L20

On L63,_nibblesToTraverse function increases pathPtr with the size of the extension node key.

pathPtr += _nibblesToTraverse(RLP.toData(currentNodeList[0]), path, pathPtr);

Then on L73, updated pathPtr is passed. Here _nibblesToTraverse will return 0 because the key of the extension node will not match this time. Hence false is returned from the function and Merkle proof verification will fail.

Possible fix for the issue is to preserve pathPtr before updating on L63 and pass the preserved pathPtr on L73. Refer this commit.

Below are the parameters which were passed to the verify function.

value : 0x5fe7f977e71dba2ea1a68e21057beebb9be2ac30c6410aa38d4f3fbe41dcffd2

encodedPath : 0x40769c9cc6db1aff35e37923897950227d2a87c95ef0101b2a0233740f2ce00d

rlpParentNodes : 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

root : 0xa506e7e444fc636360bb593a808f41f126a8813ea71410d4515987eacc594380

[0xsarvesh]

Opened issues for MPP bug in the 3 repos:
1. ConsenSysMesh/rb-relay#3
2. TrueBitFoundation/eth-patricia#1
3. mrsmkl/eth-patricia#1

[schemar]

Blocked by tests as this shouldn't be closed before it is tested.