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Mitigation Strategies Analysis for elastic/logstash

Mitigation Strategy: Enforce TLS and Client Authentication for Beats Input (Logstash Configuration)

  • Description:

    1. Logstash Configuration: Within the Logstash configuration file (e.g., beats.conf in /etc/logstash/conf.d/), configure the beats input plugin as follows:
      • ssl => true: Enable SSL/TLS encryption.
      • ssl_certificate => "/path/to/logstash_server.crt": Specify the path to the Logstash server's certificate file.
      • ssl_key => "/path/to/logstash_server.key": Specify the path to the Logstash server's private key file.
      • ssl_certificate_authorities => ["/path/to/ca.crt"]: Specify the path to the Certificate Authority (CA) certificate file used to sign the client certificates.
      • ssl_verify_mode => "force_peer": Require client certificate authentication. This is crucial. Do not use peer or none.
    2. Restart Logstash: After making these changes, restart the Logstash service to apply the new configuration.
    3. Verify in Logs: Check the Logstash logs for any SSL-related errors during startup or when Beats agents connect.

  • Threats Mitigated:

    • Unauthorized Data Injection (Severity: High): Ensures only authorized Beats agents with valid, CA-signed certificates can send data.
    • Man-in-the-Middle (MitM) Attacks (Severity: High): TLS encryption prevents interception and modification of data.
    • Data Eavesdropping (Severity: High): TLS encryption prevents unauthorized reading of data.

  • Impact:

    • Unauthorized Data Injection: Risk reduced significantly (90-95%).
    • Man-in-the-Middle (MitM) Attacks: Risk eliminated (100%).
    • Data Eavesdropping: Risk eliminated (100%).

  • Currently Implemented:

    • Fully implemented with all required settings in the beats input configuration.

  • Missing Implementation:

    • None.

Mitigation Strategy: Plugin Vetting and Regular Updates (Logstash Plugin Management)

  • Description:

    1. Prioritize Official Plugins: Use the logstash-plugin list command to review installed plugins. Prioritize those from Elastic.
    2. Community Plugin Review (Before Installation): Before installing a community plugin using logstash-plugin install <plugin_name>, thoroughly review its source code (available on GitHub or other repositories) for security vulnerabilities. Look for:
      • Insecure deserialization.
      • Command injection.
      • Regular expression denial of service (ReDoS) vulnerabilities.
      • Insecure use of external libraries.
    3. Regular Updates: Use the logstash-plugin update command regularly (ideally automated with a script) to update all installed plugins to their latest versions. This command updates all plugins unless a specific plugin is specified.
    4. Check for updates: Use command logstash-plugin list --verbose | grep -i update to check if there are any updates available.

  • Threats Mitigated:

    • Vulnerabilities in Logstash Plugins (Severity: High): Reduces the risk of exploiting known and unknown vulnerabilities.
    • Code Execution (Severity: Critical): Mitigates the risk of arbitrary code execution.
    • Denial of Service (DoS) (Severity: High): Reduces DoS risks from plugin vulnerabilities.

  • Impact:

    • Vulnerabilities in Logstash Plugins: Risk reduced significantly (70-80%).
    • Code Execution: Risk reduced significantly (60-70%).
    • Denial of Service (DoS): Risk reduced moderately (50-60%).

  • Currently Implemented:

    • A script runs weekly to execute logstash-plugin update.

  • Missing Implementation:

    • Formal code review process for community plugins before installation is missing.

Mitigation Strategy: Regular Expression Security (ReDoS Prevention within Filters)

  • Description:

    1. Audit Existing Filters: Examine all Logstash filter configurations (e.g., grok.conf, mutate.conf) that use regular expressions. Identify any potentially vulnerable patterns.
    2. grok Timeout: Within the grok filter configuration, always set the timeout_millis option to a reasonable value (e.g., 1000 milliseconds). This prevents a single malicious input from consuming excessive CPU time due to a poorly designed regex. Example: 
      grok {
  match => { "message" => "%{MY_PATTERN}" }
  timeout_millis => 1000
}
    3. Simplify and Test: Rewrite any complex or potentially vulnerable regular expressions to be simpler and less prone to backtracking. Test thoroughly with various inputs, including edge cases.
    4. Consider dissect: If a regular expression is too complex to secure, consider using the dissect filter instead, which is generally more performant and less vulnerable to ReDoS.

  • Threats Mitigated:

    • Regular Expression Denial of Service (ReDoS) (Severity: High): Prevents DoS attacks caused by crafted input strings.

  • Impact:

    • Regular Expression Denial of Service (ReDoS): Risk reduced significantly (80-90%).

  • Currently Implemented:

    • timeout_millis is set for all grok filters.

  • Missing Implementation:

    • A comprehensive audit of all regular expressions for ReDoS vulnerabilities has not been performed.

Mitigation Strategy: Secure Logstash Configuration Files (Environment Variables)

  • Description:

    1. Identify Secrets: Review all Logstash configuration files and identify any sensitive information, such as passwords, API keys, or other credentials.
    2. Replace with Environment Variables: Replace the hardcoded secrets with environment variable references using the ${VAR_NAME} syntax within the Logstash configuration files. For example, replace password => "mysecretpassword" with password => "${LOGSTASH_PASSWORD}".
    3. Set Environment Variables: Set the corresponding environment variables before starting Logstash. This can be done in the systemd service file (using Environment=), in a shell script that starts Logstash, or through other system-level mechanisms. Do not store the secrets in the Logstash configuration files themselves.
    4. Restart Logstash: Restart Logstash to apply the changes.

  • Threats Mitigated:

    • Credential Exposure (Severity: Critical): Prevents attackers from obtaining credentials if they gain access to the configuration files.

  • Impact:

    • Credential Exposure: Risk reduced significantly.

  • Currently Implemented:

    • Partially implemented; some secrets are still hardcoded.

  • Missing Implementation:

    • A complete migration of all secrets to environment variables is needed.

Mitigation Strategy: Enforce TLS for Output Connections (Logstash Configuration)

  • Description:

    1. Review Output Configurations: Examine all Logstash output configurations (e.g., elasticsearch.conf, kafka.conf).
    2. Enable TLS: For each output plugin that supports TLS, enable it by setting the appropriate options (usually ssl or tls) to true. Consult the specific plugin documentation for the exact syntax. For example, for Elasticsearch: 
      output {
  elasticsearch {
    hosts => ["https://my-es-cluster:9200"]
    ssl => true
    cacert => "/path/to/ca.crt"
    # ... other settings ...
  }
}
    3. Provide Certificates: Specify the paths to the necessary certificate files (CA certificate, client certificate, client key) as required by the output plugin.
    4. Restart Logstash: Restart Logstash to apply the changes.

  • Threats Mitigated:

    • Man-in-the-Middle (MitM) Attacks (Severity: High): Prevents interception and modification of data sent to outputs.
    • Data Eavesdropping (Severity: High): Prevents unauthorized reading of data sent to outputs.

  • Impact:

    • Man-in-the-Middle (MitM) Attacks: Risk eliminated (100%).
    • Data Eavesdropping: Risk eliminated (100%).

  • Currently Implemented:

    • TLS is enabled for the Elasticsearch output.

  • Missing Implementation:

    • TLS needs to be enabled for all other output plugins that support it.

Mitigation Strategy: Configure and Use Persistent Queues (Logstash Queuing)

  • Description:

    1. Choose a Queue Type: In your Logstash configuration, configure a persistent queue. The persisted queue type is recommended for production environments. The file queue type is also an option. Avoid the memory queue type for production if data loss is unacceptable.
    2. Configure Queue Settings: Within the Logstash configuration file (typically in the main logstash.yml or a separate configuration file), set the following: 
      queue.type: persisted  # Or 'file'
queue.max_bytes: 4gb   # Adjust as needed based on available disk space and expected volume
path.queue: "/path/to/queue/data" # Specify a directory for queue data (persisted queue only)
queue.checkpoint.writes: 1024 # Adjust as needed
      • queue.type: Specifies the queue type (persisted, file, or memory).
      • queue.max_bytes: Limits the maximum size of the queue. This is crucial to prevent disk space exhaustion.
      • path.queue: (For persisted queue) Specifies the directory where the queue data will be stored. Ensure this directory has sufficient disk space and is accessible by the Logstash user.
      • queue.checkpoint.writes: Defines how often to force a checkpoint.
    3. Restart Logstash: Restart Logstash to apply the new queue configuration.
    4. Monitor Queue: Use monitoring tools to track the queue size and ensure it's not growing unbounded.

  • Threats Mitigated:

    • Data Loss During Outages (Severity: High): Persistent queues prevent data loss if Logstash restarts or crashes.
    • Denial of Service (DoS) (Severity: Medium): Provides some buffering against sudden spikes in input data, although it's not a primary DoS mitigation.

  • Impact:

    • Data Loss During Outages: Risk reduced significantly (80-90%).
    • Denial of Service (DoS): Risk reduced slightly (20-30%).

  • Currently Implemented:

    • The persisted queue is configured with a max_bytes limit.

  • Missing Implementation:

    • None.