Imported from SamuelChien/mega-skills-collection (token-integration-analyzer/SKILL.md). Install upstream with npx skills add SamuelChien/mega-skills-collection --skill token-integration-analyzer. Copyright stays with the author.

Token Integration Analyzer

Purpose

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

1. Token Implementations: Analyze if your token follows ERC20/ERC721 standards or has non-standard behavior
2. Token Integrations: Analyze how your protocol handles arbitrary tokens, including weird/non-standard tokens
3. On-chain Analysis: Query deployed contracts for scarcity, distribution, and configuration
4. 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:

1. General Considerations - Security reviews, team transparency, security contacts
2. Contract Composition - Complexity analysis, SafeMath usage, function count, entry points
3. Owner Privileges - Upgradeability, minting, pausability, blacklisting, team accountability
4. ERC20 Conformity - Return values, metadata, decimals, race conditions, Slither checks
5. ERC20 Extension Risks - External calls/hooks, transfer fees, rebasing/yield-bearing tokens
6. Token Scarcity Analysis - Supply distribution, holder concentration, exchange distribution, flash loan/mint risks
7. 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...
8. Token Integration Safety - Safe transfer patterns, balance verification, allowlists, wrappers, defensive patterns
9. ERC721 Conformity - Transfer to 0x0, safeTransferFrom, metadata, ownerOf, approval clearing, token ID immutability
10. 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
```solidity
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:

1. USDT (0xdac17f9...)
2. USDC (0xa0b86991...)
3. DAI (0x6b175474...)
4. WETH (0xc02aaa39...)
5. 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).

---

## 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 |

---

## 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).

---

## 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!