storage layout

a tool to get readable state diffs and enumerate complete contract storage

🚧 status: proof of concept 🚧

usage

• storage-layout storage <contract> print all slots and values
• storage-layout layout <txhash> print a decoded state diff

how it works

1. get storage layout of a contract, which comes as one of compiler output format. here i use a modified vyper compiler with a test contract.
2. get storage diff, here i use trace_replayTransaction in stateDiff mode. this is not strictly necessary since you can get all SSTORE from vmTrace.
3. extract preimages from a trace. we look for all SHA3 calls which hash two words and write down key and slot.
4. then we unwrap storage slots using preimages we have collected until we reach basic storage indexes we have in the layout. for exmaple, a slot value for mapping could be among preimages, we record a path we traversed to construct nested keys.
5. decode abi types using metadata from contract storage layout.

further research

how to dump the complete contract storage and print it in a readable way.

this tool can already dump the entire storage using parity_listStorageKeys, but to decode it we need to collect all preimages.

for this we can find all calls to the address using trace_filter and then vmTrace all transactions and record all preimages.

related work

• slither-read-storage can do more advanced forward storage reading
• sol2uml can draw storage layout diagrams