attack-surface.md

Attack Surface Analysis for mozilla/mozjpeg

Attack Surface: Malformed JPEG Input Handling

Description: Vulnerabilities arising from mozjpeg's parsing of non-standard or maliciously crafted JPEG files. Errors in parsing logic can lead to crashes, denial of service, or memory corruption.

• How mozjpeg Contributes: mozjpeg is responsible for decoding and processing JPEG files. Its parsing logic for headers, segments, and markers is a potential attack surface if not robust against malformed input.
• Example: A crafted JPEG with an excessively long header segment could cause mozjpeg to read beyond buffer boundaries when parsing the header, leading to a buffer overflow.
• Impact: Denial of Service (DoS), Memory Corruption, potentially Remote Code Execution (RCE) if memory corruption is exploitable.
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Regularly update mozjpeg to the latest version. Security patches often address parsing vulnerabilities discovered in previous versions.
  • Error Handling: Implement proper error handling in the application using mozjpeg. Catch exceptions or error codes returned by mozjpeg and gracefully handle invalid JPEG inputs instead of crashing.
  • Sandboxing/Isolation: If possible, process JPEGs using mozjpeg within a sandboxed environment or isolated process to limit the impact of a potential exploit.

Attack Surface: Integer Overflows in Image Dimensions and Sizes

Description: Integer overflows can occur when mozjpeg calculates memory allocation sizes or loop bounds based on image dimensions or file sizes from the JPEG header. This can lead to undersized buffers and subsequent buffer overflows.

• How mozjpeg Contributes: mozjpeg uses image dimensions and file sizes from the JPEG header for memory management. If these values are not properly validated and sanitized within mozjpeg's code, overflows can occur.
• Example: A JPEG with extremely large dimensions specified in the header could cause an integer overflow when mozjpeg calculates the buffer size needed for pixel data, leading to a heap buffer overflow when processing the image.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Ensure mozjpeg is updated to the latest version, as integer overflow vulnerabilities are often addressed in security patches.
  • Resource Limits: Implement resource limits on the application processing JPEGs. For example, limit the maximum allowed image dimensions or file size to prevent excessively large values from being processed.

Attack Surface: Exif and Metadata Parsing Vulnerabilities

Description: Vulnerabilities in how mozjpeg parses and processes Exif, IPTC, and XMP metadata embedded within JPEG files. These sections can be complex and may contain vulnerabilities if not handled securely.

• How mozjpeg Contributes: mozjpeg includes functionality to parse and potentially process metadata sections within JPEGs. Vulnerabilities in these parsing routines within mozjpeg are the attack surface.
• Example: A JPEG with a maliciously crafted Exif section containing an overly long string could trigger a buffer overflow in mozjpeg's Exif parsing code.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: High
• Mitigation Strategies:
  • Library Updates: Keep mozjpeg updated to benefit from security fixes in metadata parsing.
  • Metadata Stripping (Optional): If metadata is not essential for the application's functionality, consider stripping metadata from JPEGs before processing them with mozjpeg. Libraries exist for metadata removal. This reduces the attack surface related to metadata parsing.
  • Sandboxing/Isolation: Process JPEGs in a sandboxed environment to limit the impact of potential metadata parsing exploits.

Attack Surface: Huffman Decoding Vulnerabilities

Description: Vulnerabilities in the Huffman decoding implementation within `mozjpeg. Incorrect handling of invalid or malicious Huffman tables in the JPEG stream can lead to errors.

• How mozjpeg Contributes: Huffman decoding is a core part of JPEG decompression performed by mozjpeg. Flaws in mozjpeg's Huffman decoding logic are the source of this attack surface.
• Example: A JPEG with crafted Huffman tables designed to cause out-of-bounds reads or writes during decoding within mozjpeg's Huffman decoder.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Regularly update mozjpeg to get fixes for Huffman decoding vulnerabilities.
  • Error Handling: Implement robust error handling in the application to catch errors during mozjpeg's decoding process and prevent crashes.

Attack Surface: Buffer Overflows (Stack and Heap)

Description: Buffer overflows occur when mozjpeg writes data beyond the allocated boundaries of buffers during image processing operations like DCT/IDCT, color conversion, or other image manipulations.

• How mozjpeg Contributes: mozjpeg's C/C++ implementation involves manual memory management and buffer operations. Errors in buffer size calculations or missing bounds checks within mozjpeg can lead to overflows.
• Example: A JPEG that triggers a buffer overflow during the IDCT process within mozjpeg because of incorrect buffer size calculations for intermediate DCT coefficients.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Prioritize keeping mozjpeg updated to the latest version, as buffer overflows are common targets for security patches.
  • Memory Safety Tools (Development): During development and testing, use memory safety tools (like AddressSanitizer, MemorySanitizer) to detect buffer overflows and other memory errors in mozjpeg's code and the application using it.
  • Code Review (Development): Conduct thorough code reviews of the application's integration with mozjpeg and potentially review relevant parts of mozjpeg's code (if feasible and resources allow) to identify potential buffer overflow vulnerabilities.
  • Sandboxing/Isolation: Process JPEGs in a sandboxed environment to contain the impact of potential buffer overflow exploits.

Attack Surface: Heap Overflows

Description: Heap overflows occur when mozjpeg writes beyond the allocated memory region on the heap. This can be caused by incorrect memory allocation sizes or other memory management errors within mozjpeg.

• How mozjpeg Contributes: mozjpeg uses dynamic memory allocation (heap) extensively. Errors in heap memory management within mozjpeg are the source of heap overflow vulnerabilities.
• Example: A JPEG that causes mozjpeg to allocate an undersized buffer on the heap for pixel data, leading to a heap overflow when writing decompressed pixel data into this buffer.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Keep mozjpeg updated to benefit from security patches addressing heap overflow vulnerabilities.
  • Memory Safety Tools (Development): Use memory safety tools (AddressSanitizer, MemorySanitizer) during development and testing to detect heap overflows.
  • Code Review (Development): Review code related to heap memory allocation and deallocation in mozjpeg and the application using it to identify potential issues.
  • Sandboxing/Isolation: Process JPEGs in a sandboxed environment to limit the impact of heap overflow exploits.

Attack Surface: Use-After-Free Vulnerabilities

Description: Use-after-free vulnerabilities occur when memory is freed and then accessed again. In mozjpeg, this could happen if memory used for image data or internal structures is prematurely freed.

• How mozjpeg Contributes: mozjpeg's manual memory management in C/C++ can lead to use-after-free errors if memory is not managed correctly.
• Example: A JPEG that triggers a sequence of operations in mozjpeg where memory allocated for a component of the decoding process is freed prematurely, and then a later operation attempts to access this freed memory.
• Impact: Memory Corruption, potentially Remote Code Execution (RCE), Denial of Service (DoS).
• Risk Severity: Critical
• Mitigation Strategies:
  • Library Updates: Ensure mozjpeg is updated to the latest version, as use-after-free vulnerabilities are often addressed in security patches.
  • Memory Safety Tools (Development): Use memory safety tools (like AddressSanitizer, LeakSanitizer) during development and testing to detect use-after-free errors.
  • Code Review (Development): Conduct careful code reviews of memory management logic in mozjpeg and the application's interaction with it.
  • Sandboxing/Isolation: Process JPEGs in a sandboxed environment to limit the impact of use-after-free exploits.