attack-surface.md

Attack Surface Analysis for protocolbuffers/protobuf

Attack Surface: 1. Buffer Overflow during Deserialization

• Description: Maliciously crafted protobuf messages with oversized fields or nested structures can cause buffer overflows in the protobuf parsing logic, leading to memory corruption.
• Protobuf Contribution: Protobuf's binary format and parsing process, if not implemented with robust bounds checking in the library, can be vulnerable to overflows when handling unexpected or excessively large input data.
• Example: An attacker sends a protobuf message where a string field is declared to be a small size in the schema, but the actual encoded message contains a string far exceeding that size. The parsing library attempts to write this oversized string into a fixed-size buffer, causing an overflow.
• Impact: Memory corruption, application crashes, potentially arbitrary code execution if the attacker can control the overflowed data.
• Risk Severity: Critical to High
• Mitigation Strategies:
  • Use the latest Protobuf library versions with known buffer overflow fixes.
  • Implement input size limits on incoming protobuf messages and fields before parsing.
  • Utilize memory-safe programming languages and practices when handling protobuf data.
  • Conduct fuzzing and security testing specifically targeting protobuf parsing with malformed and oversized messages.

Attack Surface: 2. Integer Overflow/Underflow in Size Calculations

• Description: Integer overflows or underflows during protobuf parsing, especially when handling size fields, can lead to incorrect memory allocation, buffer overflows, or other unexpected behavior.
• Protobuf Contribution: Protobuf's encoding relies on length-prefixing fields and messages. Manipulated length fields in a malicious message can trigger integer overflows/underflows during size calculations within the parsing library.
• Example: An attacker crafts a protobuf message with a size field set to a value close to the maximum integer limit. During parsing, calculations involving this size field overflow, leading to an undersized buffer allocation. Subsequent data writing into this buffer then causes a buffer overflow.
• Impact: Memory corruption, incorrect data handling, application crashes, potentially exploitable conditions.
• Risk Severity: High
• Mitigation Strategies:
  • Use up-to-date protobuf libraries with robust integer handling and overflow checks.
  • Validate size fields in incoming protobuf messages to ensure they are within reasonable and expected ranges before parsing.
  • If implementing custom protobuf handling logic, use safe integer arithmetic functions that detect and prevent overflows/underflows.
  • Conduct code reviews of protobuf parsing and handling logic to identify potential integer overflow vulnerabilities.

Attack Surface: 3. Denial of Service (DoS) via Resource Exhaustion (Parsing Complexity)

• Description: Parsing excessively complex or deeply nested protobuf messages can consume significant CPU and memory resources, leading to denial of service.
• Protobuf Contribution: Protobuf's flexibility in defining complex message structures, including nesting and repeated fields, can be abused to create messages that are computationally expensive for the parsing library to process.
• Example: An attacker sends a protobuf message with extremely deep nesting levels or a very large number of repeated fields. Parsing this message consumes excessive CPU time and memory, potentially causing the application to become unresponsive or crash due to resource exhaustion.
• Impact: Application slowdown, service unavailability, potential crashes, resource exhaustion.
• Risk Severity: High
• Mitigation Strategies:
  • Enforce strict limits on the maximum size of incoming protobuf messages.
  • Implement timeouts for protobuf parsing operations to prevent excessively long parsing times.
  • Implement resource quotas (CPU, memory) for processes handling protobuf messages.
  • Establish guidelines to limit the complexity of protobuf schemas, avoiding excessive nesting and very large numbers of repeated fields where possible.
  • Implement rate limiting on incoming protobuf message processing.

Attack Surface: 4. Schema Poisoning/Manipulation (Dynamic Schema Loading)

• Description: If an application dynamically loads protobuf schemas from untrusted sources, a malicious actor could inject or manipulate the schema, leading to incorrect parsing and potential vulnerabilities.
• Protobuf Contribution: Protobuf relies on schemas for message definition. Dynamic schema loading, while sometimes necessary, introduces a risk if the schema source is not trusted and properly secured, as the parsing process is directly dependent on the schema.
• Example: An application fetches protobuf schemas from a remote server. An attacker compromises this server and replaces legitimate schemas with malicious ones. When the application loads the poisoned schemas, it may parse messages incorrectly, potentially bypassing security checks or leading to exploitable conditions.
• Impact: Data corruption, bypassing security checks, potential for arbitrary code execution if combined with crafted messages.
• Risk Severity: High to Critical
• Mitigation Strategies:
  • Load protobuf schemas only from trusted and authenticated sources.
  • Implement mechanisms to verify the integrity of loaded schemas (e.g., using digital signatures or checksums).
  • Prefer static schema definitions embedded within the application rather than dynamic loading from external sources, if feasible.
  • Secure schema storage and transport if dynamic loading is necessary.

Attack Surface: 5. Implementation-Specific Vulnerabilities in Protobuf Libraries

• Description: Bugs and vulnerabilities may exist in specific language implementations of protobuf libraries.
• Protobuf Contribution: Protobuf libraries are complex software responsible for parsing and handling potentially untrusted data according to the protobuf specification. Vulnerabilities in these libraries directly impact the security of applications using protobuf.
• Example: A specific version of the C++ protobuf library has a known heap buffer overflow vulnerability in its parsing routine for certain message types. An attacker exploits this vulnerability by sending a specially crafted message that triggers the overflow in an application using this vulnerable library.
• Impact: Memory corruption, crashes, arbitrary code execution, DoS, depending on the vulnerability.
• Risk Severity: Varies from High to Critical depending on the specific vulnerability.
• Mitigation Strategies:
  • Regularly update Protobuf libraries to the latest versions to patch known vulnerabilities.
  • Use vulnerability scanning tools to identify known vulnerabilities in the protobuf libraries used.
  • Monitor security advisories and vulnerability databases related to protobuf libraries.
  • Choose reputable and actively maintained protobuf libraries from official sources.

Attack Surface: 6. Outdated Protobuf Library Versions

• Description: Using outdated versions of protobuf libraries exposes the application to known, publicly disclosed vulnerabilities.
• Protobuf Contribution: Outdated libraries lack security patches and fixes present in newer versions, making them vulnerable to exploits targeting known weaknesses in the protobuf parsing and handling logic.
• Example: An application uses an old version of the Python protobuf library that has a publicly known vulnerability allowing for denial of service attacks. An attacker exploits this vulnerability to crash the application.
• Impact: Memory corruption, crashes, arbitrary code execution, DoS, depending on the vulnerability.
• Risk Severity: Varies from High to Critical depending on the specific vulnerability.
• Mitigation Strategies:
  • Regularly update Protobuf libraries as part of a consistent dependency management process.
  • Use dependency management tools to track and update protobuf library versions.
  • Automate dependency updates and testing to ensure timely patching of vulnerabilities.