#38908 [BC-Insight] Missing Failed Subcalls in Erigon Tracers When Encountering `ErrInsufficientBalance` Error

Submitted on Jan 17th 2025 at 16:23:21 UTC by @a3yip6 for Attackathon | Ethereum Protocol

• Report ID: #38908

• Report Type: Blockchain/DLT

• Report severity: Insight

• Target: https://github.com/ledgerwatch/erigon

• Impacts:

  • (Specifications) A bug in specifications with no direct impact on client implementations

Description

Brief/Intro

Given any transactions with a failed subcalls due to insufficient balance, the tracer module in Erigon does not work properly. More specifically, the corresponding subcall is missing. This bug can be exploited in production.

Vulnerability Details

Expected behaviour

For a transaction with a failed subcall due to ErrInsufficientBalance, the tracer should return the full trace, including all subcalls, even if some fail. The expected output is:

{
  "txHash": "0xd0d52b784a239d1a7e765f6cd9daf0ffdee29f6c942f517b42b42388b8a7ff87",
  "result": {
    "from": "0xfdce42116f541fc8f7b0776e2b30832bd5621c85",
    "gas": "0x14e9b",
    "gasUsed": "0xf240",
    "to": "0x3dbacbf3da19ff6dedea74ed5c8722107672cb83",
    "input": "0x3bfc026c",
    "calls": [
      {
        "from": "0x3dbacbf3da19ff6dedea74ed5c8722107672cb83",
        "gas": "0xcc05",
        "gasUsed": "0x56f0",
        "to": "0xb7e811662fa10ac068aee115ac2e682821630535",
        "input": "0x",
        "value": "0xde0b6b3a7640000",
        "type": "CALL"
      },
      {
        "from": "0x3dbacbf3da19ff6dedea74ed5c8722107672cb83",
        "gas": "0x5b64",
        "gasUsed": "0x0",
        "to": "0xb7e811662fa10ac068aee115ac2e682821630535",
        "input": "0x",
        "error": "insufficient balance for transfer",
        "value": "0xde0b6b3a7640000",
        "type": "CALL"
      }
    ],
    "value": "0xde0b6b3a7640000",
    "type": "CALL"
  }
}

This behavior matches the output from geth and reth.

Actual behaviour

In erigon, the tracer does not include the second subcall, resulting in the following truncated output:

{
  "txHash": "0xd0d52b784a239d1a7e765f6cd9daf0ffdee29f6c942f517b42b42388b8a7ff87",
  "result": {
    "from": "0xfdce42116f541fc8f7b0776e2b30832bd5621c85",
    "gas": "0x14e9b",
    "gasUsed": "0xf240",
    "to": "0x3dbacbf3da19ff6dedea74ed5c8722107672cb83",
    "input": "0x3bfc026c",
    "calls": [
      {
        "from": "0x3dbacbf3da19ff6dedea74ed5c8722107672cb83",
        "gas": "0xcc05",
        "gasUsed": "0x56f0",
        "to": "0xb7e811662fa10ac068aee115ac2e682821630535",
        "input": "0x",
        "value": "0xde0b6b3a7640000",
        "type": "CALL"
      }
    ],
    "value": "0xde0b6b3a7640000",
    "type": "CALL"
  }
}

The second subcall with the ErrInsufficientBalance error is missing, which differs from the behavior of geth and reth.

Impact Details

Some platform (e.g., Etherscan) might use Erigon's tracer to calculate some front-end data. A buggy implementation would result in incorrect UI data.

References

I believe the bug is in here: https://github.com/erigontech/erigon/blob/ab8c054a7179072bb12fa30c94dbb28f008c28d3/core/vm/evm.go#L181-L202

Proof of Concept

Proof of Concept

Option 1: Testnet with Custom Nodes

1. Set up a testnet using geth and erigon as nodes. Use kurtosis for automation.
2. Deploy the PoC contracts to the testnet.

3. Send a transaction that includes a failed subcall due to ErrInsufficientBalance. One can directly use the PoC.zip and run:

forge script ./script/DeployAndInteract.s.sol:DeployAndInteract --rpc-url $TESTNET_RPC_URL --broadcast

1. Inspect the transaction trace via the RPC of geth and erigon:

• debug_traceTransaction on both nodes.

• Compare the outputs to observe the discrepancy in the erigon trace.

Option 2: Mainnet Analysis

1. Identify a mainnet transaction with a failed subcall caused by ErrInsufficientBalance.

2. Trace the transaction using the debug_traceTransaction RPC method:

• Use geth RPC.

• Use erigon RPC.

1. Compare the outputs from both nodes.