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Attack Tree Analysis for google/re2

Objective: Compromise Application Using RE2 (Focus on High-Risk Vectors)

Attack Tree Visualization

Compromise Application Using RE2 [ROOT GOAL - CRITICAL NODE]
├───(OR)─ Exploit Resource Exhaustion in RE2 Processing [HIGH RISK PATH]
│   ├───(AND)─ Cause CPU Exhaustion [HIGH RISK PATH]
│   │   ├───(OR)─ Send Extremely Long Input Strings [HIGH RISK PATH]
│   │   │   └─── Action: Craft and send very large strings as input to regex matching functions. [CRITICAL NODE - Resource Exhaustion]
│   ├───(AND)─ Cause Memory Exhaustion [HIGH RISK PATH]
│   │   ├───(OR)─ Send Extremely Long Input Strings [HIGH RISK PATH]
│   │   │   └─── Action: Same as above for CPU exhaustion. [CRITICAL NODE - Resource Exhaustion]
├───(OR)─ Exploit Application Integration Flaws with RE2 [HIGH RISK PATH]
│   ├───(AND)─ Regex Injection [HIGH RISK PATH]
│   │   ├───(OR)─ Unsanitized User Input in Regex Pattern [HIGH RISK PATH]
│   │   │   └─── Action: Inject malicious regex syntax into user-provided input that is directly used to construct the regex pattern for RE2. [CRITICAL NODE - Regex Injection]
│   └───(AND)─ Input Injection Exploiting Regex Logic [HIGH RISK PATH]
│       ├───(OR)─ Bypass Input Validation via Regex Evasion [HIGH RISK PATH]
│       │   └─── Action: Craft input strings that bypass application-level input validation regexes by exploiting subtle regex logic or edge cases in the validation patterns. [CRITICAL NODE - Validation Bypass]

Attack Tree Path: Resource Exhaustion via Long Input Strings

Description: Attacker sends extremely long strings as input to regex matching functions within the application that uses RE2. While RE2 is linear time, processing very large inputs still consumes significant CPU and memory resources, potentially leading to Denial of Service (DoS) or application slowdown.

  • Likelihood: High
  • Impact: Medium (Denial of Service, Application Slowdown)
  • Effort: Low
  • Skill Level: Low
  • Detection Difficulty: Easy (High CPU/Memory usage, slow response times)
  • Mitigation:
    • Implement strict input length limits for all user-provided inputs processed by RE2.
    • Consider asynchronous processing or timeouts for regex operations, especially on potentially large inputs.
    • Monitor application resource usage (CPU, memory) and set up alerts for unusual spikes.

Attack Tree Path: Regex Injection via Unsanitized User Input

Description: Attacker injects malicious regex syntax into user-provided input that is directly used to construct the regex pattern for RE2 within the application. This allows the attacker to control the regex pattern, potentially leading to resource exhaustion, logic errors, security bypasses, or even triggering underlying RE2 vulnerabilities.

  • Likelihood: High
  • Impact: High (Resource Exhaustion, Security Bypass, potentially RCE if combined with other vulnerabilities)
  • Effort: Low
  • Skill Level: Low
  • Detection Difficulty: Easy to Medium (Input validation failures, unusual regex patterns in logs, resource spikes)
  • Mitigation:
    • CRITICAL MITIGATION: Never directly use unsanitized user input to construct regex patterns.
    • Use parameterized regex patterns where possible, defining patterns in code or configuration.
    • If user input must influence the regex, sanitize it by removing or escaping regex metacharacters before constructing the pattern.
    • Implement robust input validation to reject inputs containing suspicious regex syntax.

Attack Tree Path: Validation Bypass via Regex Evasion

Description: Attacker crafts input strings specifically designed to bypass application-level input validation regexes. This is achieved by exploiting subtle logic errors, edge cases, or weaknesses in the validation regex patterns themselves. Successful bypass allows the attacker to submit malicious or unexpected input that the validation was intended to prevent, potentially leading to further exploitation of application logic or vulnerabilities.

  • Likelihood: Medium
  • Impact: Medium to High (Bypass of intended security controls, potential for further exploitation depending on what validation protects)
  • Effort: Medium
  • Skill Level: Medium
  • Detection Difficulty: Medium (Input validation failures might be logged, but successful bypass might be silent)
  • Mitigation:
    • Design simple and robust validation regexes that are easy to understand and test. Avoid overly complex patterns.
    • Thoroughly test validation regex patterns with a wide range of inputs, including edge cases, boundary conditions, and known bypass techniques.
    • Consider using alternative validation methods in addition to or instead of regexes, especially for critical security checks.
    • Regularly review and update validation regexes to address newly discovered bypass techniques.