feat: Add ERC-20/721/1155 standard compliance checker rule set

[Nanle-code]

Overview

Incorrect implementation of ERC token standards is a major source of integration bugs and security vulnerabilities in the ecosystem. Missing return values, wrong event signatures, incorrect interface implementation, and missing reentrancy guards on ERC-777 hooks have caused significant losses. ChainProof should have a dedicated rule set for validating ERC standard compliance.

Standards to Cover

ERC-20 Compliance (CP-ERC20)

• Missing return value on transfer/transferFrom — ERC-20 spec requires a bool return; some tokens omit it, breaking integrators
• Missing Transfer and Approval events — integrators and indexers rely on these
• Non-standard decimals — decimals() should return uint8, not uint256
• approve race condition — flagging direct approve without a increaseAllowance / decreaseAllowance pattern

ERC-721 Compliance (CP-ERC721)

• Missing safeTransferFrom reentrancy guard — ERC-721 calls onERC721Received on the recipient which creates a reentrancy vector
• Missing supportsInterface implementation — required by ERC-165
• Unrestricted minting — _mint callable without access control

ERC-1155 Compliance (CP-ERC1155)

• Missing TransferSingle/TransferBatch events
• Missing onERC1155Received reentrancy consideration

Detection Strategy

1. Detect which ERC standard a contract implements via interface detection (function signature heuristic)
2. Once standard is detected, apply the corresponding compliance rule set
3. Flag deviations as findings with severity scaled to exploit impact

// packages/core/src/rules/erc-compliance.ts
export function detectERCStandard(ast: ASTNode): 'ERC20' | 'ERC721' | 'ERC1155' | null
export function checkERC20Compliance(ast: ASTNode, source: string): Finding[]
export function checkERC721Compliance(ast: ASTNode, source: string): Finding[]
export function checkERC1155Compliance(ast: ASTNode, source: string): Finding[]

Acceptance Criteria

• ERC standard auto-detection via function signature heuristics
• ERC-20: missing return value, missing events, decimals type check
• ERC-721: safeTransferFrom reentrancy, supportsInterface, unrestricted mint
• ERC-1155: missing transfer events
• Example non-compliant contracts in examples/contracts/erc/
• Compliance rule IDs prefixed CP-ERC20-*, CP-ERC721-*, CP-ERC1155-*

References

• EIP-20
• EIP-721
• EIP-1155