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Mitigation Strategies Analysis for matrix-org/synapse

Mitigation Strategy: Federation Domain Whitelisting/Blacklisting

  • Mitigation Strategy: Federation Domain Whitelisting/Blacklisting

    • Description:

      1. Identify Trusted Servers: Identify known, trusted Matrix homeservers.
      2. Configure federation_domain_whitelist: In homeserver.yaml, add trusted server domains to the federation_domain_whitelist list. Each domain on a new line.
      3. Configure federation_domain_blacklist (Optional): Add domains of known malicious servers to federation_domain_blacklist in homeserver.yaml.
      4. Restart Synapse: Restart Synapse for changes to take effect.
      5. Monitor and Refine: Regularly monitor server logs and federation traffic. Adjust lists as needed.

    • Threats Mitigated:

      • Malicious Federated Servers (Severity: High): Reduces interaction with known malicious servers.
      • Compromised Federated Servers (Severity: High): Limits damage from a compromised server.
      • Federation-Based DoS Attacks (Severity: Medium): Reduces the attack surface.

    • Impact:

      • Malicious Federated Servers: Significant reduction (80-90%).
      • Compromised Federated Servers: Reduces risk (60-70%).
      • Federation-Based DoS Attacks: Moderate reduction (30-40%).

    • Currently Implemented: (Hypothetical) Partially. Basic federation_domain_whitelist exists, but isn't regularly updated. No federation_domain_blacklist. Config in /etc/synapse/homeserver.yaml.

    • Missing Implementation: (Hypothetical)

      • No formal review/update process for the whitelist.
      • No blacklist.
      • Insufficient federation traffic monitoring.

Mitigation Strategy: Federation Rate Limiting

  • Mitigation Strategy: Federation Rate Limiting

    • Description:

      1. Understand Parameters: Familiarize yourself with Synapse's federation rate limiting parameters in homeserver.yaml: federation_rc_window_size, federation_rc_sleep_limit, federation_rc_sleep_delay, federation_rc_reject_limit, federation_rc_concurrent.
      2. Baseline Traffic: Monitor normal federation traffic to establish a baseline.
      3. Configure Parameters: Adjust parameters in homeserver.yaml based on baseline and desired protection. Start conservatively.
      4. Restart Synapse: Restart Synapse.
      5. Monitor and Tune: Continuously monitor effectiveness and adjust.

    • Threats Mitigated:

      • Federation-Based DoS Attacks (Severity: High): Directly mitigates by limiting request rates.
      • Resource Exhaustion (Severity: Medium): Prevents a server from consuming excessive resources.
      • Spam from Federated Servers (Severity: Medium): Can help reduce spam volume.

    • Impact:

      • Federation-Based DoS Attacks: Significant reduction (70-80%).
      • Resource Exhaustion: High impact (80-90%).
      • Spam from Federated Servers: Moderate impact (40-50%).

    • Currently Implemented: (Hypothetical) Partially. Default values are in place, but not tuned. Config in /etc/synapse/homeserver.yaml.

    • Missing Implementation: (Hypothetical)

      • No baseline traffic analysis.
      • Insufficient monitoring of effectiveness.

Mitigation Strategy: Room Moderation and Permissions (Synapse-Native)

  • Mitigation Strategy: Room Moderation and Permissions (Synapse-Native)

    • Description:

      1. Default Room Permissions: Configure sensible default room permissions in homeserver.yaml. Restrict who can send messages in new rooms, for example.
      2. Room-Specific Permissions (via Synapse Admin API or Clients): Use Synapse Admin API or clients supporting room permission management to:
        • Set m.room.power_levels: Define power levels for user roles.
        • Set m.room.join_rules: Control how users join (invite-only, public).
        • Set events_default: Default power level to send messages.
        • Set invite: Power level to invite users.
      3. Use Synapse Admin API for Moderation: Utilize the Synapse Admin API for tasks like:
        • Kicking/banning users.
        • Deleting messages.
        • Shutting down rooms.
        • Querying room state.

    • Threats Mitigated:

      • Spam and Abuse in Rooms (Severity: High): Empowers moderators.
      • Illegal Content in Rooms (Severity: High): Reduces distribution.
      • Room Hijacking (Severity: Medium): Permissions prevent unauthorized control.
      • Unmanageable Large Rooms (Severity: Medium): Moderation helps control.

    • Impact:

      • Spam and Abuse in Rooms: High impact (70-80%) with active moderation.
      • Illegal Content in Rooms: High impact (70-80%).
      • Room Hijacking: Moderate impact (50-60%).
      • Unmanageable Large Rooms: Moderate impact (40-50%).

    • Currently Implemented: (Hypothetical) Partially. Basic permissions are in place, some moderators active.

    • Missing Implementation: (Hypothetical)

      • Inconsistent application of room permissions.
      • Full utilization of the Synapse Admin API for moderation is not standardized.

Mitigation Strategy: Media Repository Restrictions (Synapse-Native)

  • Mitigation Strategy: Media Repository Restrictions (Synapse-Native)

    • Description:

      1. Set max_upload_size: In homeserver.yaml, configure max_upload_size to limit upload sizes.
      2. Configure allowed_mimetypes and blocked_mimetypes: Use these in homeserver.yaml to control allowed/blocked file types. Restrict executables.
      3. Restart Synapse: Restart for changes to take effect.

    • Threats Mitigated:

      • Malicious File Uploads (Severity: High): Reduces malware uploads.
      • Media Repository DoS Attacks (Severity: Medium): Size limits help.
      • Storage Exhaustion (Severity: Medium): Size limits prevent excessive storage use.

    • Impact:

      • Malicious File Uploads: Moderate impact (50-60%, higher with external scanning).
      • Media Repository DoS Attacks: Moderate impact (40-50%).
      • Storage Exhaustion: High impact (90-100%).

    • Currently Implemented: (Hypothetical) Partially. max_upload_size is set, but MIME types are not restricted.

    • Missing Implementation: (Hypothetical)

      • MIME type restrictions are not enforced.

Mitigation Strategy: Secure Application Service (AS) Management (Synapse-Native)

  • Mitigation Strategy: Secure Application Service (AS) Management (Synapse-Native)

    • Description:

      1. Strict Registration: Require approval for AS registrations.
      2. Strong Authentication: Use unique tokens and TLS for AS connections (configured in AS registration file).
      3. Namespace Restrictions: Define user ID and room alias namespaces each AS controls (in AS registration file). Prevents impersonation.
      4. Monitor AS Activity: Use Synapse's logs and metrics to watch for suspicious AS behavior.

    • Threats Mitigated:

      • Malicious Application Services (Severity: High): Reduces risk.
      • Compromised Application Services (Severity: High): Limits damage.
      • Impersonation Attacks (Severity: Medium): Namespace restrictions prevent.

    • Impact:

      • Malicious Application Services: High impact (80-90%).
      • Compromised Application Services: High impact (70-80%).
      • Impersonation Attacks: High impact (90-100%).

    • Currently Implemented: (Hypothetical) Partially. Registration requires approval, but the process isn't rigorous. Namespace restrictions exist, but aren't always enforced.

    • Missing Implementation: (Hypothetical)

      • No formal, documented AS approval process.
      • Inconsistent namespace restriction enforcement.
      • Insufficient AS activity monitoring.

Mitigation Strategy: Push Notification Content Control (Synapse-Native)

  • Mitigation Strategy: Push Notification Content Control (Synapse-Native)

    • Description:

      1. Configure push.pusher_implementation: In homeserver.yaml, review the settings under the push section, specifically push.pusher_implementation.
      2. Set template: Within the push configuration, use the template setting to control the level of detail in push notifications. Choose low_detail or no_content to minimize sensitive information. Example: 
        push:
  pusher_implementation: "simple"
  template: "low_detail"
      3. Restart Synapse: Restart for changes to take effect.

    • Threats Mitigated:

      • Sensitive Information Leakage via Push (Severity: Medium): Reduces the amount of sensitive data exposed in push notifications.

    • Impact:

      • Sensitive Information Leakage via Push: High impact (70-80% reduction) when using low_detail or no_content.

    • Currently Implemented: (Hypothetical) Partially implemented. The default simple pusher is used, but the template setting is not explicitly configured for low detail.

    • Missing Implementation: (Hypothetical)

      • Explicit configuration of the template setting to low_detail or no_content is missing.