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attack-surface.md

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Attack Surface Analysis for spf13/viper

Attack Surface: Malicious Configuration File Injection

  • Description: Attackers inject malicious content into configuration files loaded by Viper, potentially leading to code execution or other security breaches due to vulnerabilities in configuration parsing.
  • Viper Contribution: Viper's core functionality is parsing various configuration file formats (YAML, JSON, TOML, INI). Vulnerabilities in the underlying parsing libraries used by Viper, especially for formats like YAML with deserialization risks, directly contribute to this attack surface. Viper's design of accepting and processing these files makes it the vector for this attack.
  • Example: An application loads a YAML configuration file from a user-controlled location. An attacker crafts a YAML file containing malicious YAML directives. When Viper parses this file using a vulnerable YAML parser, it triggers Remote Code Execution (RCE) on the server.
  • Impact: Remote Code Execution (RCE), data corruption, denial of service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Secure Configuration File Sources: Load configuration files only from trusted and controlled sources. Avoid loading files from user uploads or untrusted external locations.
    • Input Validation and Schema Validation: Validate the structure and content of configuration files against a strict schema before Viper parses them. This can catch malicious or unexpected structures.
    • Use Safe Parsers and Libraries: Ensure Viper and its dependencies, especially YAML parsing libraries, are up-to-date and patched against known vulnerabilities. Consider using safer, less complex data formats if possible, or libraries with stronger security records.
    • Sandboxing/Isolation: Run the application in a sandboxed environment to limit the impact if code execution occurs due to a malicious configuration file.

Attack Surface: Environment Variable Injection/Override (in Security-Sensitive Contexts)

  • Description: Attackers manipulate environment variables to inject or override application configurations, specifically targeting security-sensitive settings managed by Viper, leading to compromised security.
  • Viper Contribution: Viper's feature of binding configuration keys to environment variables directly enables this attack surface. If Viper is configured to read security-critical settings from environment variables, and the environment is not strictly controlled, attackers can leverage Viper's design to inject malicious values.
  • Example: An application uses Viper to read database credentials from the environment variable DATABASE_PASSWORD. An attacker gains control over the environment where the application runs (e.g., in a container). They set DATABASE_PASSWORD to a malicious value. Viper reads this overridden value, and the application connects to a database controlled by the attacker.
  • Impact: Unauthorized access to resources (e.g., databases), data breach, privilege escalation.
  • Risk Severity: High
  • Mitigation Strategies:
    • Principle of Least Privilege for Environment Variables: Avoid storing highly sensitive information directly in environment variables if at all possible. Use dedicated secrets management solutions (like HashiCorp Vault, AWS Secrets Manager, etc.) instead of relying on environment variables for secrets.
    • Environment Variable Validation (if unavoidable): If using environment variables for sensitive settings is unavoidable, strictly validate and sanitize their values after Viper reads them, before using them in security-critical operations.
    • Secure Environment Control: Restrict access to the environment where the application runs to prevent unauthorized modification of environment variables. Implement strong access controls and monitoring of the environment.
    • Configuration Precedence Management: Carefully manage Viper's configuration precedence. If environment variables are used, ensure they are not unintentionally given higher precedence than more secure configuration sources in production environments.

Attack Surface: Compromised Remote Configuration Source

  • Description: If Viper is configured to fetch configuration from a remote source (e.g., etcd, Consul), a compromise of this remote source allows attackers to inject malicious configurations directly into the application through Viper.
  • Viper Contribution: Viper's built-in support for remote configuration sources (like etcd, Consul) makes it the direct conduit for malicious configurations if these remote sources are compromised. Viper's design is to trust and apply the configuration it retrieves from these sources.
  • Example: An application uses Viper to fetch configurations from a Consul cluster. An attacker compromises the Consul cluster and modifies configuration values related to authentication or authorization. When Viper fetches configuration from Consul, it receives and applies the malicious configuration, effectively injecting the attack directly into the application's runtime behavior.
  • Impact: Unauthorized access, data breach, application takeover, denial of service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Secure Remote Source: Harden the remote configuration source (etcd, Consul, etc.) itself. Implement strong authentication, authorization, access control, and regular security audits of the remote configuration system.
    • Secure Communication (HTTPS/TLS): Always use HTTPS/TLS to encrypt communication between Viper and the remote configuration source to prevent Man-in-the-Middle attacks during configuration retrieval.
    • Mutual Authentication: Implement mutual TLS or other strong authentication mechanisms to verify the identity of both Viper and the remote configuration source, ensuring only authorized clients can retrieve configuration.
    • Configuration Versioning and Auditing: Implement versioning and auditing for configurations stored in the remote source. Track changes and detect unauthorized modifications to the configuration data before Viper retrieves it.
    • Regular Integrity Checks: Implement mechanisms to periodically verify the integrity and authenticity of the configuration data retrieved from the remote source by Viper.