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Project Design Document: PSR-3 Logger Interface

BUSINESS POSTURE

  • Priorities:

    • Provide a standardized logging interface for PHP libraries and frameworks.
    • Promote interoperability between different logging implementations.
    • Enable developers to easily switch between different loggers without modifying their code.
    • Facilitate consistent logging practices across the PHP ecosystem.

  • Goals:

    • Define a common interface for logging messages.
    • Specify log levels and their intended usage.
    • Allow for contextual data to be included with log messages.
    • Ensure the interface is simple, flexible, and easy to implement.

  • Business Risks:

    • Inconsistent logging practices across different libraries and frameworks, making it difficult to aggregate and analyze logs.
    • Tight coupling between application code and specific logging implementations, hindering flexibility and maintainability.
    • Lack of a standardized way to handle contextual data in log messages, leading to incomplete or inconsistent log information.
    • Adoption failure: If the standard is not widely adopted, the benefits of interoperability will not be realized.

SECURITY POSTURE

  • Existing Security Controls:

    • security control: The PSR-3 standard itself does not directly implement security controls. It is an interface definition. Security is the responsibility of the implementing libraries. (Described in the PSR-3 specification).
    • security control: Implementations should avoid logging sensitive data directly. (Implicit in good logging practices, but not explicitly enforced by the interface).
    • security control: Implementations should consider the security of the underlying transport and storage mechanisms used for logging. (Responsibility of the implementation).

  • Accepted Risks:

    • accepted risk: The PSR-3 interface does not mandate specific security mechanisms, relying on implementations to handle security appropriately.
    • accepted risk: The interface does not specify how to handle sensitive data, leaving this to the discretion of developers and implementers.

  • Recommended Security Controls:

    • security control: Implementations SHOULD provide mechanisms for sanitizing or redacting sensitive data from log messages (e.g., using placeholders or filtering).
    • security control: Implementations SHOULD offer options for secure transport and storage of log data (e.g., encryption, access control).
    • security control: Implementations SHOULD follow secure coding practices to prevent vulnerabilities such as injection attacks.
    • security control: Implementations SHOULD clearly document their security considerations and recommendations.

  • Security Requirements:

    • Authentication: Not directly applicable to the logging interface itself. Authentication is relevant to the systems that consume or manage the logs.
    • Authorization: Not directly applicable to the logging interface. Authorization is relevant to accessing and managing log data.
    • Input Validation: Implementations MUST ensure that contextual data passed to the logger does not introduce vulnerabilities (e.g., injection attacks). Context data should be treated as untrusted input.
    • Cryptography: Implementations SHOULD provide options for encrypting log data at rest and in transit, especially when dealing with sensitive information.

DESIGN

C4 CONTEXT

graph LR
    A["User/Application"] --> B("PSR-3 Logger Interface");
    B --> C("Logger Implementation (e.g., Monolog, Log4php)");
    C --> D("Log Storage (e.g., File, Database, Cloud Service)");
    C --> E("Log Monitoring/Analysis Tools");
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  • Elements:

      1. Name: User/Application
      • Type: External System/User
      • Description: The application or user code that utilizes the PSR-3 logging interface.
      • Responsibilities: Calls the methods of the PSR-3 logger interface to log messages.
      • Security controls: Should avoid passing sensitive data directly to the logger.
      1. Name: PSR-3 Logger Interface
      • Type: Interface
      • Description: The standardized logging interface defined by PSR-3.
      • Responsibilities: Defines the methods for logging messages at different levels and with contextual data.
      • Security controls: None directly implemented; relies on implementations.
      1. Name: Logger Implementation (e.g., Monolog, Log4php)
      • Type: Library/Component
      • Description: A concrete implementation of the PSR-3 logger interface.
      • Responsibilities: Handles the actual logging of messages to the configured storage.
      • Security controls: Should implement secure coding practices, data sanitization, and secure transport/storage options.
      1. Name: Log Storage (e.g., File, Database, Cloud Service)
      • Type: Data Store
      • Description: The storage mechanism used to persist log data.
      • Responsibilities: Stores log data securely and provides access for analysis.
      • Security controls: Access control, encryption at rest, data retention policies.
      1. Name: Log Monitoring/Analysis Tools
      • Type: External System
      • Description: Tools used to monitor, analyze, and visualize log data.
      • Responsibilities: Provides insights into application behavior and potential issues.
      • Security controls: Authentication, authorization, secure communication with log storage.

C4 CONTAINER

graph LR
    A["User/Application"] --> B("PSR-3 Logger Interface");
    B --> C("Logger Implementation");
    C --> D("Handlers (e.g., StreamHandler, SyslogHandler)");
    C --> E("Formatters (e.g., LineFormatter, JsonFormatter)");
    D --> F("Log Storage");
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  • Elements:

      1. Name: User/Application
      • Type: External System/User
      • Description: The application or user code that utilizes the PSR-3 logging interface.
      • Responsibilities: Calls the methods of the PSR-3 logger interface to log messages.
      • Security controls: Should avoid passing sensitive data directly to the logger.
      1. Name: PSR-3 Logger Interface
      • Type: Interface
      • Description: The standardized logging interface defined by PSR-3.
      • Responsibilities: Defines the methods for logging messages at different levels and with contextual data.
      • Security controls: None directly implemented; relies on implementations.
      1. Name: Logger Implementation
      • Type: Library/Component
      • Description: A concrete implementation of the PSR-3 logger interface (e.g., Monolog).
      • Responsibilities: Manages handlers and formatters, processes log records.
      • Security controls: Should implement secure coding practices.
      1. Name: Handlers (e.g., StreamHandler, SyslogHandler)
      • Type: Component
      • Description: Components responsible for writing log records to specific destinations.
      • Responsibilities: Writes log records to files, databases, network services, etc.
      • Security controls: Should handle sensitive data appropriately, use secure transport protocols.
      1. Name: Formatters (e.g., LineFormatter, JsonFormatter)
      • Type: Component
      • Description: Components responsible for formatting log records into specific formats.
      • Responsibilities: Formats log records as strings, JSON, XML, etc.
      • Security controls: Should sanitize data to prevent injection vulnerabilities.
      1. Name: Log Storage
      • Type: Data Store
      • Description: The storage mechanism used to persist log data.
      • Responsibilities: Stores log data securely and provides access for analysis.
      • Security controls: Access control, encryption at rest, data retention policies.

DEPLOYMENT

  • Possible Deployment Solutions:

      1. Composer Dependency: The PSR-3 interface and its implementations are typically included as project dependencies via Composer, the PHP package manager.
      1. Framework Integration: Many PHP frameworks provide built-in logging facilities that are PSR-3 compliant or offer easy integration with PSR-3 loggers.
      1. Standalone Library: The PSR-3 interface can be used as a standalone library in projects that do not use a framework.

  • Chosen Solution (Composer Dependency):

graph LR
    A["Development Environment"] --> B("Composer");
    B --> C("Packagist (PHP Package Repository)");
    C --> D("Project Codebase");
    D --> E("Production Server");
    E --> F("Log Storage");
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  • Elements:

      1. Name: Development Environment
      • Type: Environment
      • Description: The developer's local machine or development server.
      • Responsibilities: Writing and testing code.
      • Security controls: Standard development environment security practices.
      1. Name: Composer
      • Type: Tool
      • Description: The PHP package manager.
      • Responsibilities: Manages project dependencies, including the PSR-3 interface and logger implementations.
      • Security controls: Dependency verification, signature checking (if available).
      1. Name: Packagist (PHP Package Repository)
      • Type: External Service
      • Description: The central repository for PHP packages.
      • Responsibilities: Hosts and distributes PHP packages.
      • Security controls: Security measures to protect the repository and its packages.
      1. Name: Project Codebase
      • Type: Code
      • Description: The application code that uses the PSR-3 logger.
      • Responsibilities: Contains the application logic and logging calls.
      • Security controls: Secure coding practices, avoiding logging of sensitive data.
      1. Name: Production Server
      • Type: Environment
      • Description: The server where the application is deployed.
      • Responsibilities: Runs the application and handles user requests.
      • Security controls: Server hardening, firewall, intrusion detection/prevention systems.
      1. Name: Log Storage
      • Type: Data Store
      • Description: The storage mechanism used to persist log data (e.g., file system, database, cloud service).
      • Responsibilities: Stores log data securely.
      • Security controls: Access control, encryption at rest, data retention policies.

BUILD

  • The PSR-3 interface itself is a specification and does not have a build process. However, implementations of the interface (e.g., Monolog, Log4php) will have their own build processes. Since PSR-3 is an interface, the build process is more relevant to concrete implementations of that interface. We'll describe a generalized build process for a typical PSR-3 compliant logging library.
graph LR
    A["Developer"] --> B("Code Repository (e.g., GitHub)");
    B --> C("CI/CD System (e.g., GitHub Actions, Jenkins)");
    C --> D("Static Analysis Tools (e.g., PHPStan, Psalm)");
    C --> E("Unit Tests");
    C --> F("Code Style Checker (e.g., PHP_CodeSniffer)");
    C --> G("Package Build (Composer)");
    G --> H("Artifact Repository (e.g., Packagist)");
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  • Elements Description:

      1. Name: Developer
      • Type: Actor
      • Description: The person writing and committing code.
      • Responsibilities: Writes code, runs tests locally, commits changes.
      • Security controls: Secure coding practices, code review.
      1. Name: Code Repository (e.g., GitHub)
      • Type: System
      • Description: Version control system storing the library's source code.
      • Responsibilities: Stores code, tracks changes, facilitates collaboration.
      • Security controls: Access control, branch protection rules.
      1. Name: CI/CD System (e.g., GitHub Actions, Jenkins)
      • Type: System
      • Description: Automated system for building, testing, and deploying the library.
      • Responsibilities: Runs tests, builds packages, deploys releases.
      • Security controls: Secure configuration, access control, secrets management.
      1. Name: Static Analysis Tools (e.g., PHPStan, Psalm)
      • Type: Tool
      • Description: Tools that analyze code for potential errors and vulnerabilities without executing it.
      • Responsibilities: Identifies potential bugs, security issues, and code quality problems.
      • Security controls: Detects common coding errors that could lead to vulnerabilities.
      1. Name: Unit Tests
      • Type: Test Suite
      • Description: Automated tests that verify the functionality of individual components.
      • Responsibilities: Ensures that code behaves as expected.
      • Security controls: Can help prevent regressions and ensure security-related code functions correctly.
      1. Name: Code Style Checker (e.g., PHP_CodeSniffer)
      • Type: Tool
      • Description: Tool that enforces coding style standards.
      • Responsibilities: Ensures consistent code style, improving readability and maintainability.
      • Security controls: Indirectly improves security by making code easier to understand and review.
      1. Name: Package Build (Composer)
      • Type: Process
      • Description: The process of creating a distributable package using Composer.
      • Responsibilities: Creates a package that can be installed via Composer.
      • Security controls: Dependency verification, signature checking (if available).
      1. Name: Artifact Repository (e.g., Packagist)
      • Type: System
      • Description: Repository where the built package is stored and made available for download.
      • Responsibilities: Hosts and distributes the library package.
      • Security controls: Security measures to protect the repository and its packages.

RISK ASSESSMENT

  • Critical Business Processes:

    • Maintaining application stability and availability.
    • Troubleshooting and debugging application issues.
    • Monitoring application performance and behavior.
    • Auditing user actions and system events.
    • Compliance with regulatory requirements (if applicable).

  • Data Sensitivity and Protection:

    • Data: Log messages, including contextual data.
    • Sensitivity: Varies depending on the application and the data being logged. Can range from low (debug messages) to high (sensitive user data, if logged inappropriately).
    • Protection:
      • Avoid logging sensitive data directly.
      • Use placeholders or redaction for sensitive information.
      • Implement secure transport and storage for log data (encryption, access control).
      • Regularly review and audit log data.
      • Implement appropriate data retention policies.

QUESTIONS & ASSUMPTIONS

  • Questions:

    • What specific logging implementations are being considered? (This will affect the detailed security controls and recommendations.)
    • What are the specific regulatory or compliance requirements related to logging?
    • What is the expected volume of log data? (This will impact storage and performance considerations.)
    • What are the existing security policies and procedures for the organization?
    • What level of access control is required for log data?

  • Assumptions:

    • BUSINESS POSTURE: The organization values interoperability and maintainability of its logging infrastructure.
    • SECURITY POSTURE: The organization has a basic understanding of security best practices and is willing to implement reasonable security controls.
    • DESIGN: The PSR-3 interface will be used in conjunction with a concrete logging implementation (e.g., Monolog). The log data will be stored in a secure manner, with appropriate access controls. The build process will include static analysis and unit testing.