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Attack Tree Analysis for activemerchant/active_merchant

Objective: To fraudulently obtain goods/services or steal funds by exploiting vulnerabilities within the active_merchant integration.

Attack Tree Visualization

                                      Fraudulently Obtain Goods/Services or Steal Funds
                                                    (via Active Merchant)
                                                        ^
                                                        |
          -------------------------------------------------------------------------------------------------
          |                                               |                                               |
  1. Exploit Gateway-Specific Logic Flaws        2.  Manipulate Active Merchant's Abstraction Layer   3. Leverage Configuration Errors
          |                                               |                                               |
  -------------------------                   -------------------------------------------------       ------------------------
  |                       |                   |                 |                                 |                 |
1a. Bypass CVV/AVS     1b. Replay Attacks   2a. Inject       2b. Bypass                           3a. Use Default   3b. Expose
  [HIGH RISK]           [HIGH RISK]           Malicious     Gateway-Specific                      Credentials     Sensitive Data
                                              Parameters    Checks                                [HIGH RISK]     [HIGH RISK]
                                              {CRITICAL}     [HIGH RISK]                           {CRITICAL}      {CRITICAL}
                                              [HIGH RISK]

Attack Tree Path: 1. Exploit Gateway-Specific Logic Flaws

  • 1a. Bypass CVV/AVS [HIGH RISK]:

    • Description: The attacker attempts to submit transactions without valid Card Verification Value (CVV) or Address Verification System (AVS) data. This can occur if active_merchant or the application doesn't correctly handle the specific gateway's CVV/AVS response codes, or if the gateway allows optional or non-standard CVV/AVS checks.
    • Likelihood: Medium
    • Impact: High (allows fraudulent transactions)
    • Effort: Low
    • Skill Level: Intermediate
    • Detection Difficulty: Medium
    • Mitigation:
      • Implement server-side validation of CVV/AVS results, independent of active_merchant.
      • Thoroughly test the gateway integration's handling of various CVV/AVS response codes.
      • Consider using the gateway's specific API for more robust validation.

  • 1b. Replay Attacks [HIGH RISK]:

    • Description: The attacker captures a legitimate, successful transaction and attempts to resubmit it to the payment gateway. This is possible if active_merchant or the application fails to properly handle nonces, timestamps, or other anti-replay mechanisms provided by the gateway.
    • Likelihood: Low
    • Impact: High (allows duplicate fraudulent transactions)
    • Effort: Medium
    • Skill Level: Intermediate
    • Detection Difficulty: Hard
    • Mitigation:
      • Ensure the application uses and validates unique transaction identifiers (nonces) provided by the gateway.
      • Implement strict timestamp validation, rejecting transactions that are too old.
      • Consult the gateway's documentation for its recommended anti-replay measures.

Attack Tree Path: 2. Manipulate Active Merchant's Abstraction Layer

  • 2a. Inject Malicious Parameters {CRITICAL} [HIGH RISK]:

    • Description: The attacker attempts to inject unexpected or malicious data into the parameters passed to active_merchant. This aims to alter the transaction details (e.g., amount, currency) before they reach the gateway. This is a fundamental vulnerability stemming from insufficient input validation.
    • Likelihood: Medium
    • Impact: High (can lead to unauthorized transactions, altered amounts, etc.)
    • Effort: Low
    • Skill Level: Intermediate
    • Detection Difficulty: Medium
    • Mitigation:
      • Never trust user-supplied input.
      • Implement robust server-side validation and sanitization of all data before passing it to active_merchant.
      • Use strong parameterization and whitelisting.

  • 2b. Bypass Gateway-Specific Checks [HIGH RISK]:

    • Description: The attacker attempts to bypass security checks (e.g., amount limits, currency restrictions) that might be implemented within active_merchant. This relies on the application not implementing its own, independent server-side validation.
    • Likelihood: Medium
    • Impact: High (can lead to unauthorized transactions)
    • Effort: Medium
    • Skill Level: Intermediate
    • Detection Difficulty: Medium
    • Mitigation:
      • Implement robust server-side validation of all critical transaction parameters, independent of active_merchant.
      • Avoid relying solely on active_merchant's built-in validation.

Attack Tree Path: 3. Leverage Configuration Errors

  • 3a. Use Default Credentials [HIGH RISK] {CRITICAL}:

    • Description: The attacker gains access to the payment gateway by using default or easily guessable credentials. This is a catastrophic configuration error.
    • Likelihood: Low
    • Impact: Very High (complete compromise of the payment processing system)
    • Effort: Very Low
    • Skill Level: Novice
    • Detection Difficulty: Very Easy
    • Mitigation:
      • Never use default credentials.
      • Use strong, unique passwords and API keys.
      • Store credentials securely (environment variables, secrets manager, etc.).

  • 3b. Expose Sensitive Data [HIGH RISK] {CRITICAL}:

    • Description: The attacker obtains API keys, merchant IDs, or other sensitive information that is accidentally exposed in logs, error messages, client-side code, or source code repositories.
    • Likelihood: Medium
    • Impact: Very High (allows attackers to impersonate the merchant)
    • Effort: Low
    • Skill Level: Intermediate
    • Detection Difficulty: Medium
    • Mitigation:
      • Carefully review all logging and error handling to ensure sensitive data is never exposed.
      • Use a logging library that supports redaction.
      • Avoid including sensitive data in client-side code.
      • Regularly scan code repositories for accidental credential exposure.