Attack Surface: Integer Overflow and Underflow
- Description: Arithmetic operations result in values exceeding the maximum or falling below the minimum representable value for the data type, leading to unexpected behavior.
- How Sway Contributes: If Sway's compiler or runtime environment doesn't enforce strict overflow/underflow checks by default, or if developers can bypass them, vulnerabilities can arise. Early stage compiler might have undiscovered bugs in handling integer arithmetic. Language design choices around default arithmetic behavior and available safe math primitives directly impact this.
- Example: In a token contract, an attacker manipulates a transfer to cause an integer overflow when calculating a user's balance, leading to a massive, unintended increase in their tokens.
- Impact: Financial loss, token inflation, incorrect contract state, denial of service.
- Risk Severity: High
- Mitigation Strategies:
- Utilize safe math libraries or built-in overflow/underflow protection mechanisms provided by Sway (if available).
- Perform thorough testing of arithmetic operations, especially edge cases and boundary conditions.
- Employ static analysis tools (if available for Sway) to detect potential overflow/underflow vulnerabilities.
- Stay updated with Sway compiler and language updates that may introduce or improve overflow/underflow protection.
Attack Surface: Unsafe External Contract Interactions
- Description: Interacting with external, potentially malicious, contracts can introduce vulnerabilities if return values or state changes from these external contracts are not handled securely.
- How Sway Contributes: Sway contracts designed to interact with other Sway contracts or external systems (if bridges or similar mechanisms are used) must be robust against malicious or unexpected responses from these external entities. Sway's mechanisms for handling external calls, data validation, and error propagation are critical language-level features that directly influence this attack surface.
- Example: A Sway DeFi contract interacts with an external token contract. The token contract is malicious and returns a manipulated balance or an error code that the DeFi contract doesn't handle correctly. This could lead to incorrect calculations, unauthorized fund transfers, or contract compromise.
- Impact: Financial loss, data corruption, contract compromise, supply chain attacks.
- Risk Severity: High
- Mitigation Strategies:
- Thoroughly audit and vet external contracts before interacting with them.
- Implement robust input validation and error handling for responses from external calls within Sway contract logic.
- Use known and reputable contracts and libraries whenever possible.
- Define and enforce clear interfaces for interacting with external contracts (if supported by Sway language features).
- Consider using circuit breakers or fallback mechanisms within Sway contracts to limit the impact of malicious external contract behavior.
Attack Surface: Sway Compiler Bugs
- Description: Vulnerabilities introduced by bugs in the Sway compiler itself, leading to incorrect code generation, optimization flaws, or security loopholes in compiled contracts.
- How Sway Contributes: As a relatively new language and compiler, Sway is inherently more susceptible to compiler bugs compared to mature languages. These bugs are a direct consequence of the Sway compiler's implementation and can directly undermine the security of compiled Sway contracts, regardless of the source code's intended security.
- Example: A compiler bug might incorrectly optimize away a crucial security check in a Sway contract, introduce a vulnerability during code generation that allows for unexpected behavior, or mishandle certain language features leading to exploitable code.
- Impact: Wide range of impacts depending on the nature of the bug, potentially leading to critical vulnerabilities, contract compromise, financial loss, and unpredictable contract behavior.
- Risk Severity: High to Critical (Severity depends on the specific bug and its exploitability)
- Mitigation Strategies:
- Use stable and well-tested versions of the Sway compiler.
- Report any suspected compiler bugs to the Sway development team and community.
- Thoroughly test compiled Sway contracts, even if the source code appears secure, as compiler bugs can introduce unexpected behavior.
- Security audits should include consideration of potential compiler-introduced vulnerabilities, possibly by reviewing generated bytecode or intermediate representations (if feasible).
- Stay updated with Sway compiler releases and security advisories.