Attack Surface: Malicious SWF File Parsing
Description: Vulnerabilities arising from parsing and interpreting the complex structure of SWF files. This is Ruffle's primary responsibility.
How Ruffle Contributes: Ruffle's core function is to parse and interpret SWF files. The SWF format is complex, with numerous potential areas for errors in parsing logic.
Example: * A crafted SWF file contains a malformed DefineShape tag with an invalid number of shape records, leading to a buffer overflow when Ruffle attempts to read the shape data. * An SWF contains deeply nested compressed data that, when decompressed, exceeds allocated memory limits, causing a denial-of-service. * An SWF uses an obscure, undocumented feature of the SWF format that Ruffle doesn't handle correctly, leading to memory corruption.
Impact: * Remote Code Execution (RCE) - Potentially allowing the attacker to execute arbitrary code within the context of the browser (via WebAssembly). * Denial of Service (DoS) - Crashing the browser tab or the entire browser. * Information Disclosure - Potentially leaking memory contents.
Risk Severity: Critical
Mitigation Strategies:
* Extensive Fuzzing: Use fuzzing tools (e.g., AFL++, libFuzzer) specifically designed for binary formats to test the SWF parser with a wide range of malformed inputs. Prioritize fuzzing areas that handle complex data structures (shapes, fonts, compressed data, bytecode).
* Memory Safety (Rust): Leverage Rust's memory safety features. Minimize the use of unsafe code and thoroughly review any unsafe blocks. Use memory-safe alternatives whenever possible.
* Input Validation: Implement strict input validation at every stage of parsing. Check the size and validity of all data fields before processing them. Reject files that violate the SWF specification.
* Resource Limits: Impose strict limits on memory allocation, recursion depth, and processing time to prevent DoS attacks.
* Code Audits: Conduct regular, in-depth security audits of the SWF parsing code, focusing on areas that handle complex data structures and external data. Engage external security experts for these audits.
Attack Surface: ActionScript Virtual Machine (AVM) Exploitation
Description: Vulnerabilities in the implementation of the ActionScript virtual machine (AVM1 and AVM2). This is entirely within Ruffle's codebase.
How Ruffle Contributes: Ruffle emulates both AVM1 and AVM2. These are complex virtual machines with their own instruction sets, object models, and security models.
Example: * A malicious SWF uses a specific ActionScript opcode in an unexpected way, triggering a type confusion vulnerability in Ruffle's AVM implementation, leading to memory corruption. * An SWF exploits a flaw in Ruffle's implementation of a built-in ActionScript function to manipulate memory outside of its allocated region. * An SWF uses a combination of ActionScript instructions to create an infinite loop, causing a denial-of-service. * An SWF attempts to access restricted internal Ruffle data structures through carefully crafted ActionScript.
Impact: * Remote Code Execution (RCE) - Potentially, through memory corruption within the WebAssembly environment. * Denial of Service (DoS) - Crashing the browser tab. * Information Disclosure - Potentially accessing Ruffle's internal memory.
Risk Severity: Critical
Mitigation Strategies: * Fuzzing (ActionScript Bytecode): Fuzz the AVM implementation by generating random or mutated ActionScript bytecode and observing Ruffle's behavior. Focus on edge cases and interactions between different opcodes. * Sandbox Enforcement (Internal): Even within the WebAssembly environment, maintain a strong internal sandbox. Carefully control access to Ruffle's internal data structures and functions from ActionScript. * API Hardening: Implement robust checks and validation for all internal functions and data structures that are accessible (even indirectly) from ActionScript. * Security Audits (AVM): Conduct regular security audits of the AVM implementation, focusing on opcode handling, memory management, and internal sandboxing. * Test Suite: Create a comprehensive test suite that covers a wide range of ActionScript features and edge cases, including known security vulnerabilities in Flash Player and specifically targeting Ruffle's implementation. * Resource Limits: Implement limits on ActionScript execution time, memory usage, and recursion depth to prevent DoS attacks.
Attack Surface: Vulnerable Dependencies (Directly Used by Ruffle)
Description: Vulnerabilities in third-party Rust crates that are directly used by Ruffle's core logic (parsing, AVM, rendering). This excludes dependencies used only for build processes or testing.
How Ruffle Contributes: Ruffle's functionality depends on the security of the crates it uses for tasks like image decoding, XML parsing, etc.
Example: * Ruffle uses a crate for image decoding that has a known vulnerability, allowing a malicious SWF with a crafted image to trigger a buffer overflow within Ruffle's WebAssembly memory. * A dependency used for parsing XML data within SWFs has a vulnerability that allows for XML External Entity (XXE) attacks, potentially leading to information disclosure from Ruffle's memory.
Impact: * Varies depending on the vulnerability in the dependency. Could range from DoS to RCE (within Ruffle's WebAssembly context).
Risk Severity: High (depending on the specific vulnerability and how the dependency is used)
Mitigation Strategies:
* Dependency Auditing: Use tools like cargo audit or Dependabot to automatically and continuously check for known vulnerabilities in dependencies.
* Regular Updates: Keep dependencies up-to-date to ensure you have the latest security patches. Automate this process.
* Dependency Minimization: Minimize the number of direct dependencies to reduce the attack surface. Carefully evaluate the necessity of each dependency.
* Vulnerability Scanning: Use vulnerability scanners that can analyze Rust code and its dependencies, specifically looking for vulnerabilities that could be triggered by malicious SWF input.
* Careful Selection: Choose dependencies carefully, preferring well-maintained and security-conscious projects with a track record of prompt vulnerability response.