attack-surface.md

Attack Surface Analysis for matrix-org/synapse

Attack Surface: Client-Server API Authentication Bypass

• Description: Attackers exploit vulnerabilities within Synapse's Client-Server API authentication mechanisms to gain unauthorized access to user accounts. This bypasses intended login procedures and grants access without valid credentials.
• Synapse Contribution: Synapse's implementation of various authentication methods (password, SSO, etc.) within its Client-Server API is the direct source of this attack surface. Flaws in the logic or code of these methods can be exploited.
• Example: A vulnerability in Synapse's password authentication flow allows an attacker to craft a malicious request that bypasses password verification, granting them access to any user account.
• Impact: Unauthorized access to user accounts, complete account takeover, data breaches including private messages and room data, privacy violations, and the ability to perform actions as the compromised user within the Matrix environment.
• Risk Severity: Critical
• Mitigation Strategies:
  • Developers:
    • Implement robust and rigorously tested authentication mechanisms for the Client-Server API, adhering to security best practices.
    • Conduct regular security audits and penetration testing specifically targeting authentication flows within Synapse's API.
    • Enforce strong password policies and mandate multi-factor authentication (MFA) for all users to add layers of security beyond password-only authentication.
    • Maintain Synapse and all its dependencies up-to-date, promptly applying security patches that address known authentication vulnerabilities.

Attack Surface: Federation Protocol Vulnerabilities

• Description: Attackers exploit weaknesses inherent in the Matrix federation protocol or specifically within Synapse's implementation of this protocol to disrupt or compromise federated communication and data integrity.
• Synapse Contribution: As a primary implementation of the Matrix federation protocol, Synapse's code responsible for handling federated events, state resolution, signature verification, and other federation mechanisms is the direct source of this attack surface. Vulnerabilities in these areas can be exploited.
• Example: A malicious federated server sends specially crafted events designed to exploit a vulnerability in Synapse's event validation logic. This could lead to server crashes, data corruption within federated rooms, or denial of service affecting federated communication.
• Impact: Server crashes and instability, corruption of data across federated rooms potentially affecting multiple servers, denial of service to federated communication making rooms inaccessible or unusable, potential for wider network instability if vulnerabilities are widespread, and manipulation of information within federated rooms.
• Risk Severity: High
• Mitigation Strategies:
  • Developers:
    • Ensure strict adherence to the Matrix specification and established best practices for secure federation implementation during Synapse development.
    • Perform thorough and continuous testing and security audits specifically focusing on federation-related code paths, especially event processing and state resolution logic within Synapse.
    • Implement robust input validation and sanitization for all incoming federated events to prevent exploitation of parsing or processing vulnerabilities.
    • Keep Synapse consistently updated to benefit from ongoing security improvements and bug fixes related to the federation protocol and its implementation.

Attack Surface: Admin API Authentication Bypass

• Description: Attackers successfully bypass authentication to Synapse's highly privileged Admin API, gaining complete and unauthorized control over the homeserver and its functionalities.
• Synapse Contribution: Synapse's design includes a powerful Admin API for server management. The security of this API's authentication and authorization mechanisms is entirely managed by Synapse. Weaknesses here directly lead to this attack surface.
• Example: Synapse is deployed with default administrator credentials that are not changed, or a vulnerability in the Admin API authentication allows bypassing login, enabling an attacker to access and utilize all administrative functions.
• Impact: Full server compromise, complete data breaches including all user data and server configuration, manipulation of server configuration leading to further security issues or denial of service, arbitrary code execution on the server allowing for persistent compromise, and total control over the Synapse instance and its hosted Matrix environment.
• Risk Severity: Critical
• Mitigation Strategies:
  • Developers:
    • Implement strong and secure authentication methods specifically for the Admin API, such as robust API keys, OAuth 2.0, or certificate-based authentication.
    • Enforce strict authorization controls within the Admin API to meticulously limit access to different endpoints and administrative actions based on clearly defined roles and permissions.
    • Conduct regular and rigorous security audits and penetration testing specifically targeting the Admin API to identify and remediate any potential vulnerabilities.
    • Ensure Synapse does not ship with default credentials and enforce strong password policies for all administrative users.

Attack Surface: Third-Party Module Critical Vulnerabilities

• Description: Critical security vulnerabilities are present within third-party Synapse modules, which, when exploited, can lead to significant compromise of the Synapse homeserver.
• Synapse Contribution: Synapse's modular architecture, while offering extensibility, inherently introduces an attack surface through third-party modules. Synapse's module loading and execution mechanisms enable these modules to interact with the core system, and vulnerabilities within them can directly impact Synapse's security.
• Example: A poorly developed third-party module, designed to add custom functionality to Synapse, contains a remote code execution vulnerability. By exploiting this vulnerability in the module, an attacker gains arbitrary code execution on the Synapse server itself.
• Impact: Impact is highly variable depending on the module and the nature of the vulnerability. It can range from information disclosure and data manipulation to full server compromise, arbitrary code execution, and denial of service, effectively inheriting the potential impacts of other attack surfaces.
• Risk Severity: High to Critical (depending on the criticality of the module and the severity of the vulnerability)
• Mitigation Strategies:
  • Developers (Module Developers):
    • Adhere to secure coding practices throughout the development lifecycle of Synapse modules, prioritizing security considerations.
    • Thoroughly test and conduct security audits of modules to proactively identify and remediate vulnerabilities before release.
    • Provide comprehensive documentation and clear security guidelines for users deploying and utilizing the module.
    • Maintain modules actively, promptly releasing security updates and patches to address reported vulnerabilities.
  • Users/Administrators (Module Users):
    • Exercise extreme caution and rigorously evaluate the security posture of any third-party modules before installing them on a Synapse homeserver.
    • Prioritize installing modules only from trusted and reputable sources with a proven track record of security awareness.
    • Keep all installed modules updated to their latest versions and apply security patches immediately upon release.
    • Implement monitoring and logging to detect any suspicious activity originating from or related to installed modules.

Attack Surface: Insecure Synapse Default Configurations

• Description: Synapse is deployed using insecure default configuration settings that are provided out-of-the-box, making the homeserver vulnerable to various attacks from the initial setup.
• Synapse Contribution: Synapse's default configuration choices directly determine the initial security posture of a deployment. If these defaults are not carefully considered from a security perspective, they can create significant vulnerabilities.
• Example: Synapse's default configuration might include disabled TLS/SSL encryption, weak default database credentials, or overly permissive access controls. Deploying with these defaults exposes the server to man-in-the-middle attacks, database compromise, or unauthorized access.
• Impact: Increased ease of exploiting other vulnerabilities due to a weakened security baseline, heightened risk of unauthorized access to sensitive data and server functionalities, potential for data breaches, and a significantly compromised overall security posture from the outset.
• Risk Severity: High
• Mitigation Strategies:
  • Developers (Synapse Developers):
    • Minimize the inclusion of insecure settings within Synapse's default configuration, prioritizing security over ease of initial setup.
    • Provide prominent warnings and comprehensive guidance within documentation and setup processes regarding the security implications of default settings and the necessity for immediate hardening.
    • Offer secure configuration templates and detailed best practice documentation that administrators can readily utilize to secure their Synapse deployments.
    • Consider implementing automated security checks and hardening guides directly within the Synapse setup process to proactively encourage secure configurations.
  • Users/Administrators:
    • Thoroughly review and customize Synapse's configuration immediately after installation, strictly adhering to security best practices and hardening guides.
    • Change all default credentials without exception and disable any unnecessary features or services that are enabled by default.
    • Mandatory enable and correctly configure TLS/SSL encryption to protect communication in transit.
    • Establish a schedule for regular security reviews and updates to the Synapse configuration to maintain a strong and secure posture over time.