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Threat Model Analysis for mikel/mail

Threat: Email Header Injection

  • Description: An attacker manipulates user input fields to inject malicious headers into emails sent by the application. This is done by inserting special characters and additional headers, allowing the attacker to add recipients, spoof senders, inject content, and bypass security controls.
  • Impact:
    • Sending emails to unintended recipients, causing privacy breaches and spamming.
    • Spoofing sender identity, enabling phishing attacks and damaging reputation.
    • Injecting malicious content, delivering phishing links or malware.
    • Circumventing security controls like SPF/DKIM, improving malicious email deliverability.
  • Affected Mail Component: mail gem's header construction and sending functions, specifically when handling user-provided data in headers.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Sanitization: Strictly validate and sanitize all user-provided data before using it in email headers. Remove or escape newline characters and header-injection related characters.
    • Parameterized Email Sending: Utilize mail gem's parameterized email construction features to avoid direct header manipulation.
    • Header Encoding: Use mail gem's built-in header encoding functions to properly encode header values, preventing interpretation of special characters as header delimiters.
    • Avoid Direct Header Manipulation: Minimize or eliminate direct manipulation of raw email headers in application code.

Threat: Attachment Handling Vulnerabilities

  • Description: Attackers exploit vulnerabilities in how the application handles file attachments sent via email. This includes uploading malicious file types (executables, scripts), injecting malicious filenames, or bypassing file size limits.
  • Impact:
    • Malware distribution through email attachments, spreading viruses and ransomware.
    • Exploiting recipient systems via malicious filenames that trigger vulnerabilities in email clients or operating systems.
    • Denial of Service by overloading email systems with large attachments.
  • Affected Mail Component: Application's attachment handling logic, file upload mechanisms, and interaction with mail gem's attachment features.
  • Risk Severity: High
  • Mitigation Strategies:
    • File Type Whitelisting: Implement strict file type validation and only allow whitelisted file types for attachments.
    • Filename Sanitization: Sanitize filenames to remove or escape potentially harmful characters and prevent filename injection attacks.
    • File Size Limits: Enforce reasonable file size limits for attachments to prevent denial of service.
    • Virus Scanning: Integrate virus scanning of uploaded attachments before sending emails to detect and prevent malware distribution.

Threat: Hardcoded Credentials

  • Description: Email server credentials (username, password, API keys) are directly embedded in the application's source code, configuration files, or insecure environment variables.
  • Impact:
    • Credential Exposure if the codebase or configuration is compromised, allowing unauthorized access.
    • Unauthorized Email Sending by attackers using exposed credentials, leading to spam, phishing, and reputational damage.
  • Affected Mail Component: Application's configuration and credential management, affecting all mail gem functionalities relying on these credentials.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Environment Variables (Securely Managed): Store credentials in environment variables managed by secure systems (e.g., HashiCorp Vault, AWS Secrets Manager).
    • Secure Configuration Management: Utilize dedicated secure configuration management systems to store and manage credentials.
    • Credential Rotation: Implement regular credential rotation to limit the window of opportunity if credentials are compromised.
    • Principle of Least Privilege: Grant only necessary permissions to access email sending credentials.

Threat: Insecure Configuration

  • Description: Misconfiguration of the mail gem or the underlying email sending mechanism leads to vulnerabilities. This includes using insecure protocols (plain SMTP), incorrect TLS/SSL configuration, or permissive SMTP server settings.
  • Impact:
    • Data breaches due to exposure of email content and credentials during transmission without encryption.
    • Man-in-the-middle attacks where attackers can intercept and modify email communication.
    • Open relay exploitation, allowing attackers to use the server for spamming and malicious activities, leading to blacklisting.
  • Affected Mail Component: mail gem's configuration settings, underlying SMTP client, and email server configuration.
  • Risk Severity: High
  • Mitigation Strategies:
    • Use Secure Protocols: Always use SMTP with TLS/SSL (STARTTLS or SMTPS) for encrypted email transmission.
    • Proper TLS/SSL Configuration: Configure TLS/SSL correctly, ensuring certificate verification and using strong cipher suites.
    • Secure SMTP Server Configuration: Ensure the SMTP server is securely configured, disabling open relaying and implementing proper authentication.
    • Regular Configuration Review: Regularly review and update mail gem and email server configurations to maintain security best practices.

Threat: Vulnerable Dependencies

  • Description: The mail gem or its dependencies contain known security vulnerabilities that can be exploited by attackers.
  • Impact:
    • Various attacks depending on the vulnerability, potentially including remote code execution, denial of service, or information disclosure.
    • Application compromise if vulnerabilities in mail gem or its dependencies are exploited.
  • Affected Mail Component: mail gem library and its dependencies.
  • Risk Severity: High to Critical (depending on the specific vulnerability)
  • Mitigation Strategies:
    • Dependency Updates: Regularly update the mail gem and all its dependencies to the latest versions to patch known vulnerabilities.
    • Dependency Scanning: Use dependency scanning tools (e.g., Bundler Audit, Dependabot) to automatically identify and report known vulnerabilities.
    • Security Monitoring: Monitor security advisories for the mail gem and its ecosystem to stay informed about new vulnerabilities.