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Threat Model Analysis for redis/hiredis

Threat: Threat: Buffer Over-read in Response Parsing

  • Description: A vulnerability in hiredis's response parsing logic (e.g., when handling bulk strings or arrays) causes it to read beyond the allocated buffer when processing a response from a Redis server. This is a direct vulnerability in hiredis's code, triggered by a malformed or unexpectedly large response. This is not about the application failing to check response sizes; it's about hiredis itself having a bug that causes it to read out of bounds.
  • Impact:
    • Information disclosure (leakage of memory contents). This could expose other data handled by hiredis, or potentially even data from other parts of the application's memory.
    • Application crashes.
  • Affected Hiredis Component: The parsing functions within hiredis that handle different Redis reply types, particularly those dealing with bulk strings and arrays (within redisReaderGetReply and related functions). Specific vulnerable functions would depend on the exact nature of the bug (which would need to be identified through code review, fuzzing, or a published CVE).
  • Risk Severity: High
  • Mitigation Strategies:
    • Primary Mitigation: Update hiredis: Keep hiredis up-to-date to the latest version. This is the most crucial step, as it incorporates security patches. Monitor the hiredis release notes and security advisories for any reported vulnerabilities.
    • Fuzz Testing: Perform rigorous fuzz testing of hiredis's response parsing logic, specifically targeting bulk strings, arrays, and other complex reply types. Use a fuzzer that can generate malformed and oversized inputs.
    • Static Analysis: Use static analysis tools (e.g., Coverity, clang-analyzer) to scan the hiredis source code for potential buffer over-reads.
    • Memory Safety Tools: Compile and run hiredis (and the application using it) with memory safety tools like AddressSanitizer (ASan) or Valgrind's Memcheck during development and testing. These tools can detect memory errors at runtime.

Threat: Threat: Denial of Service via Malformed Response (Hiredis Crash)

  • Description: A crafted, malformed response from a compromised or malicious Redis server (or a man-in-the-middle attacker) triggers a bug in hiredis's parsing logic. This bug directly causes hiredis to crash, leading to a denial-of-service condition for the application using hiredis. This is distinct from the application misusing hiredis; the vulnerability is within hiredis's parsing code. The malformed response could exploit integer overflows, buffer overflows, or other logic errors within the parsing functions.
  • Impact: Application crash or unresponsiveness, leading to denial of service. The application using hiredis becomes unavailable.
  • Affected Hiredis Component: The parsing functions within hiredis that handle different Redis reply types (e.g., redisReaderGetReply, and the functions it calls internally). The specific vulnerable function would depend on the exact nature of the bug.
  • Risk Severity: High
  • Mitigation Strategies:
    • Primary Mitigation: Update hiredis: Keep hiredis meticulously up-to-date. This is the most effective way to address known vulnerabilities.
    • Fuzz Testing: Extensive fuzz testing of hiredis's response parsing is crucial. Focus on generating a wide variety of malformed responses, including those with invalid lengths, incorrect types, and unexpected characters.
    • Static Analysis: Use static analysis tools to identify potential vulnerabilities in the parsing code, such as integer overflows, buffer overflows, and uninitialized memory reads.
    • TLS Encryption: Use TLS to encrypt the communication between the application and the Redis server. This prevents man-in-the-middle attacks that could inject malformed responses. While TLS doesn't directly fix a hiredis bug, it makes exploitation harder.
    • Redis Server Security: Ensure the Redis server is secured to prevent compromise.

Threat: Threat: Integer Overflow in Parsing (Leading to Crash/Vulnerability)

  • Description: hiredis receives a very large integer value from Redis (e.g., as part of a reply, or a bulk string length). The internal parsing logic within hiredis doesn't handle potential integer overflows correctly. While less likely to be directly exploitable than a buffer overflow, a severe integer overflow could lead to a crash or, in rare cases, a more complex vulnerability. This is a vulnerability within hiredis' parsing code.
  • Impact:
    • Application crashes.
    • Potential for security vulnerabilities (though less likely and harder to exploit than buffer overflows). The overflow could lead to incorrect memory allocation or other logic errors.
  • Affected Hiredis Component: The integer parsing functions within hiredis (e.g., functions that convert string representations of integers to numeric types). These are often internal functions called by redisReaderGetReply. The specific functions would depend on the exact vulnerability.
  • Risk Severity: High (primarily due to the potential for crashes, even if direct exploitation is less likely)
  • Mitigation Strategies:
    • Primary Mitigation: Update hiredis: Keep hiredis up-to-date with the latest releases.
    • Code Review and Static Analysis: Review the hiredis source code (particularly the parsing functions) for potential integer overflow vulnerabilities. Use static analysis tools designed to detect integer overflows.
    • Fuzz Testing: Fuzz test hiredis with very large integer values (both positive and negative) to try to trigger overflows. Focus on edge cases and boundary conditions.