attack-surface.md

Attack Surface Analysis for nothings/stb

Attack Surface: Buffer Overflow

• Description: Writing data beyond the allocated memory buffer.
  • stb Contribution: stb's C implementation and manual memory management can lead to buffer overflows due to insufficient bounds checking during operations like image decoding or font parsing.
  • Example: Processing a maliciously crafted PNG image with a header declaring an extremely large width, causing stb_image to allocate a buffer based on this width. If bounds checks are inadequate during pixel data processing, stb_image might write beyond the allocated buffer.
  • Impact: Memory corruption, program crash, potential for arbitrary code execution if the overflow overwrites critical data or code pointers.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Input Validation: Rigorously validate image dimensions, font sizes, and other input parameters before using stb functions. Enforce reasonable limits.
    • Resource Limits: Limit the maximum size of images and fonts processed by the application to prevent excessively large inputs that could trigger overflows.
    • Memory Safety Tools: Employ memory safety tools like AddressSanitizer or MemorySanitizer during development and testing to detect buffer overflows.
    • Code Review: Conduct thorough code reviews of the application's integration with stb, paying close attention to memory handling and potential overflow points.
    • Compiler Security Features: Enable compiler-level security features such as stack canaries and Address Space Layout Randomization (ASLR) to mitigate exploitability of buffer overflows.

Attack Surface: Integer Overflow

• Description: Arithmetic operations resulting in a value exceeding the maximum representable value for the data type, leading to unexpected wrapping or truncation.
  • stb Contribution: stb performs calculations involving image dimensions, font sizes, and other parameters. Integer overflows in these calculations can result in undersized buffer allocations, subsequently leading to buffer overflows.
  • Example: An attacker provides an image file with width and height values that, when multiplied, cause an integer overflow. stb_image might allocate a buffer based on the overflowed (smaller) result. During image decoding, it will then write beyond this undersized buffer.
  • Impact: Undersized buffer allocation leading to buffer overflows, memory corruption, program crash, potential for code execution.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation: Validate image dimensions, font sizes, and other input parameters to ensure they are within safe ranges and will not cause integer overflows during calculations.
    • Safe Integer Arithmetic: Utilize safe integer arithmetic functions or libraries that check for overflows before performing operations, or implement manual overflow checks in the application code.
    • Resource Limits: Limit the maximum dimensions and sizes of input data to prevent excessively large values that could contribute to overflows.
    • Code Review: Carefully review code that performs calculations with input parameters, especially those related to buffer sizes, to identify potential integer overflow vulnerabilities.

Attack Surface: Heap Corruption (Use-After-Free, Double-Free)

• Description: Errors in dynamic memory management leading to corruption of the heap. Use-after-free occurs when memory is accessed after it has been freed, and double-free occurs when memory is freed multiple times.
  • stb Contribution: Memory management errors within stb's internal operations, such as incorrect freeing of allocated memory or accessing memory after it has been freed, can corrupt the heap.
  • Example: A bug in stb_truetype's font parsing logic could cause it to free a memory buffer containing glyph data prematurely, and then later attempt to access that freed memory location when rendering text.
  • Impact: Memory corruption, program crash, potential for arbitrary code execution if heap metadata is corrupted in an exploitable way.
  • Risk Severity: High
  • Mitigation Strategies:
    • Memory Safety Tools: Utilize memory safety tools (e.g., AddressSanitizer, MemorySanitizer) during development and testing to detect use-after-free and double-free vulnerabilities.
    • Code Review: Conduct thorough code reviews of stb integration, focusing on memory allocation and deallocation patterns, particularly in error handling paths and complex parsing routines.
    • Regular Updates: Keep stb updated to the latest version to benefit from bug fixes, including those related to memory management.
    • Sandboxing: If processing untrusted input, consider running stb within a sandboxed environment to limit the impact of heap corruption vulnerabilities.

Attack Surface: Denial of Service (DoS) via Resource Exhaustion

• Description: Malicious input designed to consume excessive resources (CPU, memory, disk I/O) causing the application to become unresponsive or crash.
  • stb Contribution: Processing specially crafted images or fonts with complex or highly compressed data can lead to excessive CPU usage or memory allocation within stb, resulting in a DoS.
  • Example: A crafted TIFF image with a deeply nested and highly compressed structure could cause stb_image to consume excessive CPU time and memory attempting to decompress and parse the image, leading to application unresponsiveness.
  • Impact: Application unresponsiveness, service disruption, potential server downtime.
  • Risk Severity: High
  • Mitigation Strategies:
    • Resource Limits: Implement strict timeouts for image and font processing operations. Limit the maximum file size, image dimensions, and font complexity that the application will process.
    • Input Validation: Perform robust validation on input files to reject obviously malformed, excessively large, or overly complex files before passing them to stb.
    • Rate Limiting: Implement rate limiting on requests that involve processing images or fonts to prevent attackers from overwhelming the system with malicious requests.
    • Process Isolation: Run stb processing in a separate process with resource limits enforced by the operating system to contain resource exhaustion and prevent it from impacting the main application.