threat-modeling.md

Threat Model Analysis for fuellabs/sway

Threat: Integer Overflow/Underflow

• Description: An attacker crafts inputs to cause integer variables in the Sway contract to overflow or underflow. This leads to incorrect calculations, bypassing access controls, or corrupting state, potentially allowing theft of funds or contract malfunction.
  • Impact: Financial loss (theft of funds, incorrect token balances), critical contract malfunction, potential for complete system compromise.
  • Sway Component Affected: Arithmetic operations within Sway functions, state variables storing numerical values, type casting operations.
  • Risk Severity: High
  • Mitigation Strategies:
    • Utilize safe math libraries or built-in functions in Sway that provide overflow/underflow checks.
    • Implement explicit checks for potential overflow/underflow before and after arithmetic operations, especially with external inputs.
    • Carefully choose data types for numerical variables, considering potential ranges.
    • Thoroughly test with boundary values and edge cases to identify vulnerabilities.

Threat: Logic Errors in State Management

• Description: An attacker exploits flaws in the contract's state management logic. This allows manipulation of state variables in unintended ways, bypassing state-based access controls, or causing critical contract state corruption, leading to unpredictable and potentially catastrophic failures.
  • Impact: Data corruption, unauthorized access to critical functionalities, significant financial loss, complete contract malfunction, potential for irreversible damage to the application.
  • Sway Component Affected: State variables, functions modifying state, conditional logic based on state, core contract logic and state machine.
  • Risk Severity: High
  • Mitigation Strategies:
    • Design state transitions with extreme care, using explicit state machines and clear patterns.
    • Implement rigorous validation for all state transitions and data updates.
    • Utilize access control modifiers (pub, priv) effectively to restrict state variable access.
    • Develop comprehensive unit and integration tests covering all state transitions and edge cases.
    • Employ formal verification or advanced static analysis to detect subtle logic flaws in state management.

Threat: Reentrancy (Logic Flaws related to Concurrent Execution)

• Description: An attacker exploits logic flaws allowing unexpected contract re-entry or concurrent state modifications, even in a UTXO model. This can lead to double-spending, incorrect balance updates, or critical state corruption due to race conditions or unexpected call sequences.
  • Impact: Major financial loss (double-spending, massive theft of funds), critical data corruption, complete contract failure, potential for cascading failures in dependent systems.
  • Sway Component Affected: Functions interacting with external contracts or triggering internal calls, state variables modified during execution, concurrent operation handling logic.
  • Risk Severity: High
  • Mitigation Strategies:
    • Design contract logic to be inherently resilient to re-entry and concurrent operations.
    • Implement strict checks to prevent unintended re-entry or concurrent modifications of critical state.
    • Utilize mutexes or locking mechanisms if available in Sway/FuelVM to protect critical code sections from concurrency issues.
    • Extensively test contract behavior under simulated concurrent transaction scenarios.

Threat: Access Control Vulnerabilities

• Description: An attacker bypasses or circumvents access control mechanisms in the Sway contract. This grants unauthorized execution of privileged functions or modification of restricted data, potentially leading to complete contract takeover or catastrophic data breaches.
  • Impact: Complete unauthorized access to sensitive functionalities, massive data breaches, significant financial loss, complete contract takeover and control by attacker.
  • Sway Component Affected: Access control modifiers (pub, priv), conditional statements implementing access checks, functions intended for specific roles or users, authentication/authorization logic.
  • Risk Severity: High
  • Mitigation Strategies:
    • Design and implement robust access control mechanisms using role-based access control or similar secure patterns.
    • Utilize access modifiers (pub, priv) correctly and consistently to enforce intended access restrictions.
    • Implement strong authentication and authorization checks within all functions requiring access control.
    • Thoroughly audit and penetration test access control logic to ensure complete protection against unauthorized access.
    • Consider using established and well-vetted access control libraries or patterns within the Sway ecosystem.

Threat: Oracle Manipulation (If Contract Relies on Critical External Data)

• Description: If the Sway contract relies on external data from oracles for critical functions, an attacker compromises or manipulates these oracles to feed false data. This leads to the contract making critically flawed decisions or performing actions based on malicious information, causing severe financial or operational damage.
  • Impact: Catastrophic financial loss, critical contract malfunction leading to system-wide failure, manipulation of core contract functionalities and outcomes, potential for irreversible damage to the application and its users.
  • Sway Component Affected: Functions interacting with oracles for critical data, core contract logic dependent on oracle data, data validation mechanisms for oracle inputs (if insufficient).
  • Risk Severity: High (if oracle data is critical)
  • Mitigation Strategies:
    • Utilize highly reputable, decentralized, and security-audited oracles with strong security measures.
    • Implement robust and multi-layered data validation and sanity checks on all oracle inputs within the Sway contract.
    • Employ multiple independent oracles and aggregate their data to minimize reliance on single points of failure and manipulation (oracle aggregation and consensus).
    • Utilize cryptographic techniques to verify the integrity and authenticity of oracle data (e.g., oracle signing and verification within the contract).
    • Design contract logic to be resilient to potential oracle failures or data inconsistencies, with fallback mechanisms and circuit breakers.

Threat: Compiler Bugs Leading to Critical Bytecode Vulnerabilities

• Description: A critical bug in the Sway compiler results in the generation of vulnerable bytecode from correct Sway source code. This introduces subtle, deep-seated vulnerabilities exploitable by attackers, bypassing source code level security reviews and potentially affecting all contracts compiled with the flawed compiler version.
  • Impact: Introduction of widespread, hard-to-detect critical vulnerabilities, potential for mass exploitation across multiple deployed contracts, systemic risk to the Sway ecosystem, significant financial and reputational damage.
  • Sway Component Affected: Sway compiler, bytecode generation process, all contracts compiled with the vulnerable compiler version.
  • Risk Severity: High
  • Mitigation Strategies:
    • Use thoroughly tested and security-audited stable versions of the Sway compiler.
    • Stay vigilant for compiler bug reports and security advisories from the Sway team and community.
    • Implement rigorous bytecode analysis and testing, including fuzzing and symbolic execution, to detect compiler-introduced vulnerabilities.
    • Consider formal verification techniques to mathematically prove the correctness of compiled bytecode against the source code (as tools become available).
    • Actively participate in community testing, bug reporting, and security auditing of the Sway compiler.

Threat: Supply Chain Attacks on Sway Toolchain Dependencies

• Description: Attackers compromise dependencies used by the Sway compiler or development tools, injecting malicious code. This leads to the introduction of backdoors or vulnerabilities into compiled Sway contracts or the development environment itself, potentially compromising all projects built with the infected toolchain.
  • Impact: Widespread compromise of development environments, injection of critical vulnerabilities into deployed contracts, potential for large-scale attacks affecting numerous projects and users, severe damage to trust and security of the Sway ecosystem.
  • Sway Component Affected: Sway compiler dependencies, package managers (forc), development tools, build process, potentially all contracts built using the compromised toolchain.
  • Risk Severity: High
  • Mitigation Strategies:
    • Implement robust software supply chain security practices: meticulously vet all dependencies, use only trusted package repositories, and rigorously verify package integrity using checksums and signatures.
    • Utilize dependency scanning tools to proactively identify known vulnerabilities in dependencies.
    • Isolate development environments to contain the impact of potential supply chain compromises.
    • Maintain regular updates of dependencies to patch known vulnerabilities promptly.
    • Employ dependency pinning or lock files to ensure consistent and verifiable dependency versions across builds.

Threat: Critical Vulnerabilities in Sway Standard Library

• Description: Critical flaws are discovered in the Sway standard library, affecting core functionalities used by many contracts. Exploitation of these vulnerabilities can lead to widespread security breaches in contracts relying on the flawed library components, potentially impacting a large portion of the Sway ecosystem.
  • Impact: Introduction of widespread critical vulnerabilities across many Sway contracts, potential for mass exploitation and systemic failures, significant financial and reputational damage to the Sway ecosystem and dependent applications.
  • Sway Component Affected: Sway standard library modules and functions, all contracts utilizing the vulnerable library components.
  • Risk Severity: High
  • Mitigation Strategies:
    • Maintain constant vigilance for security advisories and bug reports related to the Sway standard library.
    • Utilize stable, well-tested, and security-audited versions of the Sway standard library.
    • Conduct thorough security reviews and audits of standard library functions used in contracts, especially those handling security-sensitive operations.
    • Actively contribute to community auditing, vulnerability disclosure, and bug reporting for the Sway standard library.
    • Consider developing and using alternative or custom implementations for critical functionalities if significant security concerns arise regarding standard library components.

Threat: Data Leaks of Highly Sensitive Information through Logs and Events

• Description: Sway contracts unintentionally expose highly sensitive data (e.g., private keys, personal identifiable information) through logs or events. Attackers actively monitor blockchain logs and events to extract this critical information, leading to severe privacy breaches and potential identity theft or financial exploitation.
  • Impact: Catastrophic privacy breaches, exposure of highly sensitive user data leading to identity theft, financial exploitation, and severe reputational damage, potential legal and regulatory repercussions.
  • Sway Component Affected: log statements in Sway code, event definitions, data emitted in events, any code paths that might inadvertently log or emit sensitive data.
  • Risk Severity: High (if highly sensitive data is at risk)
  • Mitigation Strategies:
    • Conduct meticulous reviews of all log statements and event definitions in Sway contracts, specifically focusing on data being logged or emitted.
    • Absolutely avoid logging or emitting highly sensitive data in logs or events.
    • Utilize encrypted or irreversibly hashed representations of sensitive data if there is a legitimate need to log or emit information related to it, ensuring the original sensitive data remains protected.
    • Provide comprehensive security training to developers emphasizing the critical privacy implications of blockchain logs and events and secure logging practices.

Threat: Insecure Storage of Highly Sensitive Data within Contracts

• Description: Highly sensitive data (e.g., private keys, passwords, confidential user information) is stored insecurely within the Sway contract's state, making it vulnerable to unauthorized access or exploitation. Even though blockchain data is immutable, insecure storage practices can lead to critical data breaches if contract logic or vulnerabilities expose this data.
  • Impact: Catastrophic data breaches exposing highly sensitive user information, potential for mass identity theft, significant financial losses, severe reputational damage, and potential legal and regulatory penalties.
  • Sway Component Affected: State variables storing sensitive data, data storage logic within Sway functions, any code paths that might access or expose insecurely stored sensitive data.
  • Risk Severity: High (if highly sensitive data is at risk)
  • Mitigation Strategies:
    • Completely avoid storing highly sensitive data directly on-chain if at all possible.
    • If absolutely necessary to store sensitive data on-chain, employ strong encryption techniques and robust key management practices to protect it.
    • Implement strict access control mechanisms to severely restrict access to state variables containing sensitive data, minimizing potential exposure points.
    • Adhere to rigorous secure coding practices for all data storage operations within smart contracts, prioritizing data minimization and privacy-preserving techniques.
    • Thoroughly evaluate and consider utilizing off-chain storage solutions for highly sensitive data whenever feasible and appropriate to minimize on-chain privacy risks.