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Attack Tree Analysis for swisspol/gcdwebserver

Objective: Gain Unauthorized Access/Disrupt Service via GCDWebServer Vulnerabilities

Attack Tree Visualization

                                  Attacker's Goal:
                                  Gain Unauthorized Access/Disrupt Service
                                  via GCDWebServer Vulnerabilities
                                  /                               \
                                 /                                 \
            -------------------------------------         -------------------------------------
            |  Exploit Logic Flaws in Handlers  |         |   Exploit Implementation Flaws   |
            -------------------------------------         -------------------------------------
            /       |        |                                      |
           /        |        |                                      |
  ----------  ---------- ----------                            ----------
  |  Path  |  |  Auth  | |  Input |                            |  Mem.  |
  |  Trav. |  | Bypass | |  Valid.|                            |  Corrup.|
  ----------  ---------- ----------                            ----------
     |             |          |                                      |
     |             |          |                                      |

[HIGH RISK] [HIGH RISK] [HIGH RISK] {CRITICAL}

Attack Tree Path: Path Traversal (in Handler) [HIGH RISK]

  • Description: Exploits occur when a handler uses unsanitized user input (like a filename from a URL) to access files. Attackers can craft requests (e.g., /files/../../etc/passwd) to read or potentially write to arbitrary files on the server. GCDWebServer doesn't inherently prevent this; the handler's logic is responsible.
  • Likelihood: Medium to High
  • Impact: High to Very High
  • Effort: Low to Medium
  • Skill Level: Novice to Intermediate
  • Detection Difficulty: Medium
  • Mitigation:
    • Rigorously sanitize all user-supplied input used in file paths.
    • Use functions that explicitly prevent path traversal (resolve relative paths, check against whitelists).
    • Never directly concatenate user input into file paths.
    • Conduct thorough code reviews.
    • Example (Vulnerable): Handler uses filename from URL directly in [NSData dataWithContentsOfFile:].
    • Example (Mitigated): Handler uses a whitelist of filenames or resolves to an absolute, sandboxed path.

Attack Tree Path: Authentication Bypass (in Handler) [HIGH RISK]

  • Description: Flaws in the authentication logic within a handler allow attackers to bypass protection. GCDWebServer provides basic authentication, but custom implementations are common and prone to errors.
  • Likelihood: Medium
  • Impact: High to Very High
  • Effort: Medium to High
  • Skill Level: Intermediate to Advanced
  • Detection Difficulty: Medium to Hard
  • Mitigation:
    • Review authentication logic in every protected handler.
    • Perform authentication checks before sensitive operations.
    • Consider using established authentication libraries (e.g., JWT).
    • Test with invalid/malformed authentication tokens.
    • Example (Vulnerable): Handler checks for a cookie but doesn't validate its signature/expiration.
    • Example (Mitigated): Handler uses a well-vetted library and validates tokens thoroughly.

Attack Tree Path: Input Validation Issues (in Handler) [HIGH RISK]

  • Description: A broad category encompassing vulnerabilities where handlers don't properly sanitize data used in various operations (database queries, command execution, etc.). GCDWebServer delivers the potentially malicious input; the handler's responsibility is to validate it.
  • Likelihood: High
  • Impact: Variable (Low to Very High - e.g., SQL injection is Very High)
  • Effort: Low to High
  • Skill Level: Novice to Advanced
  • Detection Difficulty: Variable (Medium to Hard)
  • Mitigation:
    • Implement strict input validation in all handlers.
    • Use whitelists where possible.
    • Validate data types, lengths, and formats.
    • Consider using a validation library.
    • Perform fuzz testing.
    • Example (Vulnerable): Handler inserts user-provided string directly into a SQL query.
    • Example (Mitigated): Handler uses parameterized queries or an ORM.

Attack Tree Path: Memory Corruption (in GCDWebServer itself) {CRITICAL}

  • Description: Buffer overflows, use-after-free errors, or other memory corruption vulnerabilities within the GCDWebServer code could allow an attacker to execute arbitrary code. This is a critical vulnerability due to its potential impact.
  • Likelihood: Low
  • Impact: Very High
  • Effort: High to Very High
  • Skill Level: Advanced to Expert
  • Detection Difficulty: Hard to Very Hard
  • Mitigation:
    • Regularly update to the latest version of GCDWebServer.
    • Monitor security advisories related to the library.
    • Use memory safety tools (e.g., AddressSanitizer) during development/testing.
    • Employ static analysis tools.
    • Example: Buffer overflow in handling a large HTTP header.