Token Integration Analyzer

Purpose

Systematically analyzes the codebase for token-related security concerns using Trail of Bits' token integration checklist:

• Token Implementations: Analyze if your token follows ERC20/ERC721 standards or has non-standard behavior

• Token Integrations: Analyze how your protocol handles arbitrary tokens, including weird/non-standard tokens

• On-chain Analysis: Query deployed contracts for scarcity, distribution, and configuration

• Security Assessment: Identify risks from 20+ known weird token patterns

Framework: Building Secure Contracts - Token Integration Checklist + Weird ERC20 Database

How This Works

Phase 1: Context Discovery

Determines analysis context:

• Token implementation: Are you building a token contract?

• Token integration: Does your protocol interact with external tokens?

• Platform: Ethereum, other EVM chains, or different platform?

• Token types: ERC20, ERC721, or both?

Phase 2: Slither Analysis (if Solidity)

For Solidity projects, I'll help run:

• slither-check-erc

• ERC conformity checks

• slither --print human-summary

• Complexity and upgrade analysis

• slither --print contract-summary

• Function analysis

• slither-prop

• Property generation for testing

Phase 3: Code Analysis

Analyzes:

• Contract composition and complexity

• Owner privileges and centralization risks

• ERC20/ERC721 conformity

• Known weird token patterns

• Integration safety patterns

Phase 4: On-chain Analysis (if deployed)

If you provide a contract address, I'll query:

• Token scarcity and distribution

• Total supply and holder concentration

• Exchange listings

• On-chain configuration

Phase 5: Risk Assessment

Provides:

• Identified vulnerabilities

• Non-standard behaviors

• Integration risks

• Prioritized recommendations

Assessment Categories

I check 10 comprehensive categories covering all aspects of token security. For detailed criteria, patterns, and checklists, see ASSESSMENT_CATEGORIES.md.

Quick Reference:

• General Considerations - Security reviews, team transparency, security contacts

• Contract Composition - Complexity analysis, SafeMath usage, function count, entry points

• Owner Privileges - Upgradeability, minting, pausability, blacklisting, team accountability

• ERC20 Conformity - Return values, metadata, decimals, race conditions, Slither checks

• ERC20 Extension Risks - External calls/hooks, transfer fees, rebasing/yield-bearing tokens

• Token Scarcity Analysis - Supply distribution, holder concentration, exchange distribution, flash loan/mint risks

• Weird ERC20 Patterns (24 patterns including):

• Reentrant calls (ERC777 hooks)

• Missing return values (USDT, BNB, OMG)

• Fee on transfer (STA, PAXG)

• Balance modifications outside transfers (Ampleforth, Compound)

• Upgradable tokens (USDC, USDT)

• Flash mintable (DAI)

• Blocklists (USDC, USDT)

• Pausable tokens (BNB, ZIL)

• Approval race protections (USDT, KNC)

• Revert on approval/transfer to zero address

• Revert on zero value approvals/transfers

• Multiple token addresses

• Low decimals (USDC: 6, Gemini: 2)

• High decimals (YAM-V2: 24)

• transferFrom with src == msg.sender

• Non-string metadata (MKR)

• No revert on failure (ZRX, EURS)

• Revert on large approvals (UNI, COMP)

• Code injection via token name

• Unusual permit function (DAI, RAI, GLM)

• Transfer less than amount (cUSDCv3)

• ERC-20 native currency representation (Celo, Polygon, zkSync)

• And more...

• Token Integration Safety - Safe transfer patterns, balance verification, allowlists, wrappers, defensive patterns

• ERC721 Conformity - Transfer to 0x0, safeTransferFrom, metadata, ownerOf, approval clearing, token ID immutability

• ERC721 Common Risks - onERC721Received reentrancy, safe minting, burning approval clearing

Example Output

When analysis is complete, you'll receive a comprehensive report structured as follows:

=== TOKEN INTEGRATION ANALYSIS REPORT ===

Project: MultiToken DEX Token Analyzed: Custom Reward Token + Integration Safety Platform: Solidity 0.8.20 Analysis Date: March 15, 2024

EXECUTIVE SUMMARY

Token Type: ERC20 Implementation + Protocol Integrating External Tokens Overall Risk Level: MEDIUM Critical Issues: 2 High Issues: 3 Medium Issues: 4

Top Concerns: ⚠ Fee-on-transfer tokens not handled correctly ⚠ No validation for missing return values (USDT compatibility) ⚠ Owner can mint unlimited tokens without cap

Recommendation: Address critical/high issues before mainnet launch.

1. GENERAL CONSIDERATIONS

✓ Contract audited by CertiK (June 2023) ✓ Team contactable via security@project.com ✗ No security mailing list for critical announcements

Risk: Users won't be notified of critical issues Action: Set up security@project.com mailing list

2. CONTRACT COMPOSITION

Complexity Analysis

Slither human-summary Results:

• 456 lines of code
• Cyclomatic complexity: Average 6, Max 14 (transferWithFee())
• 12 functions, 8 state variables
• Inheritance depth: 3 (moderate)

✓ Contract complexity is reasonable ⚠ transferWithFee() complexity high (14) - consider splitting

SafeMath Usage

✓ Using Solidity 0.8.20 (built-in overflow protection) ✓ No unchecked blocks found ✓ All arithmetic operations protected

Non-Token Functions

Functions Beyond ERC20:

• setFeeCollector() - Admin function ✓
• setTransferFee() - Admin function ✓
• withdrawFees() - Admin function ✓
• pause()/unpause() - Emergency functions ✓

⚠ 4 non-token functions (acceptable but adds complexity)

Address Entry Points

✓ Single contract address ✓ No proxy with multiple entry points ✓ No token migration creating address confusion

Status: PASS

3. OWNER PRIVILEGES

Upgradeability

⚠ Contract uses TransparentUpgradeableProxy Risk: Owner can change contract logic at any time

Current Implementation:

• ProxyAdmin: 0x1234... (2/3 multisig) ✓
• Timelock: None ✗

Recommendation: Add 48-hour timelock to all upgrades

Minting Capabilities

❌ CRITICAL: Unlimited minting File: contracts/RewardToken.sol:89

function mint(address to, uint256 amount) external onlyOwner {
    _mint(to, amount);  // No cap!
}

Risk: Owner can inflate supply arbitrarily
Fix: Add maximum supply cap or rate-limited minting

Pausability

✓ Pausable pattern implemented (OpenZeppelin)
✓ Only owner can pause
⚠ Paused state affects all transfers (including existing holders)

Risk: Owner can trap all user funds
Mitigation: Use multi-sig for pause function (already implemented ✓)

Blacklisting

✗ No blacklist functionality
Assessment: Good - no centralized censorship risk

Team Transparency

✓ Team members public (team.md)
✓ Company registered in Switzerland
✓ Accountable and contactable

Status: ACCEPTABLE

4. ERC20 CONFORMITY

Slither-check-erc Results

Command: slither-check-erc . RewardToken --erc erc20

✓ transfer returns bool
✓ transferFrom returns bool
✓ name, decimals, symbol present
✓ decimals returns uint8 (value: 18)
✓ Race condition mitigated (increaseAllowance/decreaseAllowance)

Status: FULLY COMPLIANT

slither-prop Test Results

Command: slither-prop . --contract RewardToken

Generated 12 properties, all passed:
✓ Transfer doesn't change total supply
✓ Allowance correctly updates
✓ Balance updates match transfer amounts
✓ No balance manipulation possible
[... 8 more properties ...]

Echidna fuzzing: 50,000 runs, no violations ✓

Status: EXCELLENT

5. WEIRD TOKEN PATTERN ANALYSIS

Integration Safety Check

Your Protocol Integrates 5 External Tokens:

- USDT (0xdac17f9...)

- USDC (0xa0b86991...)

- DAI (0x6b175474...)

- WETH (0xc02aaa39...)

- UNI (0x1f9840a8...)

Critical Issues Found

❌ Pattern 7.2: Missing Return Values
Found in: USDT integration
File: contracts/Vault.sol:156

IERC20(usdt).transferFrom(msg.sender, address(this), amount);
// No return value check! USDT doesn't return bool

Risk: Silent failures on USDT transfers
Exploit: User appears to deposit, but no tokens moved
Fix: Use OpenZeppelin SafeERC20 wrapper

❌ Pattern 7.3: Fee on Transfer
Risk for: Any token with transfer fees
File: contracts/Vault.sol:170

uint256 balanceBefore = IERC20(token).balanceOf(address(this));
token.transferFrom(msg.sender, address(this), amount);
shares = amount * exchangeRate;  // WRONG! Should use actual received amount

Risk: Accounting mismatch if token takes fees
Exploit: User credited more shares than tokens deposited
Fix: Calculate shares from balanceAfter - balanceBefore

Known Non-Standard Token Handling

✓ USDC: Properly handled (SafeERC20, 6 decimals accounted for)
⚠ DAI: permit() function not used (opportunity for gas savings)
✗ USDT: Missing return value not handled (CRITICAL)
✓ WETH: Standard wrapper, properly handled
⚠ UNI: Large approval handling not checked (reverts >= 2^96)

[... Additional sections for remaining analysis categories ...]

For complete report template and deliverables format, see [REPORT_TEMPLATES.md](resources/REPORT_TEMPLATES.md).

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## Rationalizations (Do Not Skip)

| Rationalization | Why It's Wrong | Required Action |
|-----------------|----------------|-----------------|
| "Token looks standard, ERC20 checks pass" | 20+ weird token patterns exist beyond ERC20 compliance | Check ALL weird token patterns from database (missing return, revert on zero, hooks, etc.) |
| "Slither shows no issues, integration is safe" | Slither detects some patterns, misses integration logic | Complete manual analysis of all 5 token integration criteria |
| "No fee-on-transfer detected, skip that check" | Fee-on-transfer can be owner-controlled or conditional | Test all transfer scenarios, check for conditional fee logic |
| "Balance checks exist, handling is safe" | Balance checks alone don't protect against all weird tokens | Verify safe transfer wrappers, revert handling, approval patterns |
| "Token is deployed by reputable team, assume standard" | Reputation doesn't guarantee standard behavior | Analyze actual code and on-chain behavior, don't trust assumptions |
| "Integration uses OpenZeppelin, must be safe" | OpenZeppelin libraries don't protect against weird external tokens | Verify defensive patterns around all external token calls |
| "Can't run Slither, skipping automated analysis" | Slither provides critical ERC conformance checks | Manually verify all slither-check-erc criteria or document why blocked |
| "This pattern seems fine" | Intuition misses subtle token integration bugs | Systematically check all 20+ weird token patterns with code evidence |

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## Deliverables

When analysis is complete, I'll provide:

1. **Compliance Checklist** - Checkboxes for all assessment categories
2. **Weird Token Pattern Analysis** - Presence/absence of all 24 patterns with risk levels and evidence
3. **On-chain Analysis Report** (if applicable) - Holder distribution, exchange listings, configuration
4. **Integration Safety Assessment** (if applicable) - Safe transfer usage, defensive patterns, weird token handling
5. **Prioritized Recommendations** - CRITICAL/HIGH/MEDIUM/LOW issues with specific fixes

Complete deliverable templates available in [REPORT_TEMPLATES.md](resources/REPORT_TEMPLATES.md).

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## Ready to Begin

**What I'll need**:
- Your codebase
- Context: Token implementation or integration?
- Token type: ERC20, ERC721, or both?
- Contract address (if deployed and want on-chain analysis)
- RPC endpoint (if querying on-chain)

Let's analyze your token implementation or integration for security risks!