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Reproduced Exploit

uint256 amount truncates to uint160 — AuditVault synthetic reduction

This bug report discusses an issue found in the rotocol's handling of token amounts. The contracts use unsafe type casting from uint256 to uint160, which can lead to silent overflow or underflow conditions. This can potentially allow users to create orders with mismatched amounts, leading to fund l…

Nov 2024•Other•input-validation•4 min read

Chain

Other

Category

input-validation

Date

Nov 2024

Source

AuditVault

PoC & write-upPoC for your local evm-hack-analyzerAuditVault PoCs

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Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 44371-h-1-unsafe-type-casting-in-token-amount-handling-sherlock-ok. Standalone Foundry PoC and full write-up: 44371-h-1-unsafe-type-casting-in-token-amount-handling-sherlock-ok_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/input-validation/wrong-type · vuln/arithmetic/underflow

Reproduction: self-contained Foundry PoC with an offline synthetic contract. Full trace: output.txt.

AuditVault finding: 44371 · H-1: Unsafe Type Casting in Token Amount Handling

Key info#

ImpactHIGH — uint256 amount truncates to uint160
Protocol[[Oku'S New Order Types Contract Contest]]
FindingAuditVault #44371
Reporthttps://github.com/sherlock-audit/2024-11-oku-judging
SourceAuditVault finding
Compiler^0.8.24 (synthetic reduction)
LossReduced invariant reproduced; no live funds moved
Attacker EOAConfigured synthetic caller
Attack contractExploit
Attack txLocal Foundry Exploit.attack() call
Chain · block · dateEthereum model · block 1 · synthetic
Vulnerable contractLocal synthetic vulnerable contract in test/
Bug classSee vulnerability-class tags above

TL;DR#

This bug report discusses an issue found in the rotocol's handling of token amounts. The contracts use unsafe type casting from uint256 to uint160, which can lead to silent overflow or underflow conditions. This can potentially allow users to create orders with mismatched amounts, leading to fund loss or manipulation of the system. The root cause of this issue is that Solidity 0.8.x does not protect against data loss during type casting. The contracts perform direct casting without validation in several critical functions. An example of this is the StopLimit::modifyOrder() function, which takes uint256 amountIn as input and casts it to uint160 inside the handlePermit function. This can result in the amount becoming very small and the user being able to drain the contract by modifying their order. The user must have enough tokens and be able to interact with the contract's order cre

Background#

The upstream report is a Solidity finding. This page keeps the vulnerable statement and demonstrates its security consequence in a small, deterministic EVM model; no live RPC or external dependencies are required.

The vulnerable code#

SOLIDITY
// The exact vulnerable pattern is retained in test/44371-h-1-unsafe-type-casting-in-token-amount-handling-sherlock-ok.sol.
// @> see the marked statement in the synthetic reduction

Root cause#

The caller-controlled input or stale state is trusted before the required uniqueness, bounds, authorization, accounting, or reentrancy invariant is enforced. The marked line in the synthetic contract intentionally preserves that ordering so the assertion is executable.

Preconditions#

  • The vulnerable contract is deployed with the state described by the report.
  • The attacker can reach the affected entry point (or submit the report's crafted input).

Attack walkthrough#

  1. Exploit.run() initializes the minimal state from the report.
  2. The marked vulnerable operation executes without its required check.
  3. The contract records the resulting invariant violation and emits a Proof event.
  4. The test asserts the harm; the passing trace is recorded at output.txt:4.

Diagrams#

flowchart TD A[Attacker supplies crafted input] --> B[Vulnerable operation] B --> C{Missing invariant check} C --> D[Security impact demonstrated]
sequenceDiagram participant A as Attacker participant V as Vulnerable contract participant S as State A->>V: invoke affected entry point V->>S: apply unchecked update S-->>A: harm is observable

Remediation#

Apply the invariant before mutating state: accrue interest before adding principal; reject duplicate signers; use checked casts and bounded lengths; validate token/target/DAO identities; use nonReentrant; enforce slippage and fee equality; and validate the canonical authority or ownership relationship described by the report.

How to reproduce#

BASH
cd evm-hack-registry/44371-h-1-unsafe-type-casting-in-token-amount-handling-sherlock-ok_exp
forge test -vvvvv

The test is offline and uses only the shared forge-std library. The corresponding Playground bundle is generated from scripts/poc-configs/44371-h-1-unsafe-type-casting-in-token-amount-handling-sherlock-ok.mjs.

Sources#

Reference: https://github.com/sherlock-audit/2024-11-oku-judging

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

  • Web3Sec X hacked database: search.
  • Rekt leaderboard: search.
  • Solodit incident search: search.

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