sec-design-deep-analysis.md

Okay, I understand the task. I will perform a deep security analysis of SRS based on the provided Security Design Review document, focusing on the instructions given.

Here's the deep analysis:

Deep Security Analysis of SRS (Simple Realtime Server)

1. Objective, Scope, and Methodology

Objective:

The primary objective of this deep security analysis is to thoroughly evaluate the security posture of the Simple Realtime Server (SRS) as described in the provided Security Design Review document. This analysis aims to identify potential security vulnerabilities within SRS's key components, architecture, and data flow, ultimately providing actionable and SRS-specific mitigation strategies to enhance the security of live streaming applications built using SRS. The analysis will focus on understanding the inherent security risks associated with each component and recommend practical steps to minimize these risks.

Scope:

This analysis is scoped to the SRS server itself, based on the architecture, components, and functionalities outlined in the provided "Project Design Document: SRS (Simple Realtime Server) for Threat Modeling - Improved". The analysis will cover the following key components and layers of SRS:

• Network Interface Layer: RTMP Handler, WebRTC Handler, HTTP Handler.
• Core Logic Layer: Session Manager, Stream Router, Config Manager, Scheduler.
• Application Service Layer: Transcoder (FFmpeg), Recorder, Forwarder Logic, HTTP API Handler, HLS Muxer, HTTP-FLV Muxer.
• Data Storage Layer: Configuration Files, Recorded Files (Disk).
• External Interfaces: Publishers, Viewers, Management Clients, External Servers (Forwarding), STUN/TURN Servers, External Transcoding Engines (FFmpeg).

The analysis is based on the understanding of SRS derived from the provided design review document and publicly available information about SRS (primarily the GitHub repository and documentation linked in the review). It does not include a live penetration test or source code audit, but rather a security design review based threat analysis.

Methodology:

The methodology employed for this deep analysis involves the following steps:

1. Document Review: Thorough review of the provided "Project Design Document: SRS (Simple Realtime Server) for Threat Modeling - Improved" to understand the SRS architecture, components, data flow, and initial security considerations.
2. Component-Based Analysis: Breaking down SRS into its key components as defined in the design review. For each component, we will:
   • Analyze its functionality and purpose within the SRS ecosystem.
   • Identify potential security implications and vulnerabilities based on its design and interactions with other components and external entities.
   • Leverage the security considerations already outlined in the design review as a starting point.
3. Data Flow Analysis: Analyzing the data flow scenarios (RTMP Publish & HLS Playback, WebRTC Publish & WebRTC Playback, Management API Request) described in the design review to identify potential security risks at each stage of data processing and transmission.
4. Threat Modeling Principles: Applying threat modeling principles, implicitly aligned with STRIDE categories (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege), to systematically identify potential threats and vulnerabilities for each component and data flow.
5. SRS-Specific Mitigation Strategy Development: Developing actionable and tailored mitigation strategies specifically applicable to SRS, considering its architecture, functionalities, and the identified threats. These strategies will be practical and implementable by the development team.
6. Documentation and Reporting: Documenting the findings, identified threats, and recommended mitigation strategies in a clear and structured manner, as presented in this analysis.

This methodology ensures a structured and comprehensive approach to analyzing the security of SRS based on the provided design review, leading to actionable and relevant security recommendations.

2. Security Implications of Key Components

Based on the Security Design Review, here's a breakdown of the security implications for each key component:

4.1. Network Interface Layer Components:

• RTMP Handler (NI1):

  • Security Implications:
    • RTMP Protocol Weaknesses: Inherent protocol vulnerabilities, lack of mandatory encryption, command injection risks.
    • Buffer Overflows: Potential in AMF parsing and large message handling.
    • Authentication Bypass: Weaknesses in authentication mechanisms leading to unauthorized publishing.
    • Denial of Service (DoS): Susceptibility to DoS attacks via connection floods or malformed packets.

• WebRTC Handler (NI2):

  • Security Implications:
    • WebRTC Complexity: Large attack surface due to protocol complexity.
    • SDP Vulnerabilities: Injection attacks and misconfiguration via SDP parsing flaws.
    • ICE/STUN/TURN Security: Dependency on external services introduces vulnerabilities if compromised or misconfigured.
    • DTLS/SRTP Implementation Flaws: Vulnerabilities in DTLS/SRTP libraries used by SRS.
    • Man-in-the-Middle (MITM): Potential downgrade attacks or misconfigurations weakening DTLS/SRTP encryption.

• HTTP Handler (NI3):

  • Security Implications:
    • Standard Web Server Vulnerabilities: Path traversal, HTTP header injection, XSS (if dynamic content/API responses are not sanitized).
    • API Security: Vulnerable HTTP API endpoints due to weak authentication/authorization.
    • DoS Attacks: Susceptibility to DoS attacks via excessive requests or slowloris attacks.
    • HLS/FLV Specific Issues: Vulnerabilities in HLS manifest generation or FLV streaming.

4.2. Core Logic Layer Components:

• Session Manager (CL1):

  • Security Implications:
    • Authentication & Authorization Flaws: Weak or missing authentication and authorization mechanisms.
    • Session Management Weaknesses: Session fixation, hijacking, insecure storage, lack of timeouts.
    • Privilege Escalation: Vulnerabilities allowing unauthorized privilege gain.
    • Resource Exhaustion: DoS via excessive session creation.

• Stream Router (CL2):

  • Security Implications:
    • Stream Hijacking: Routing logic flaws leading to stream redirection or interception.
    • Unauthorized Stream Access: Lack of access control in routing leading to unauthorized viewing/publishing.
    • Injection Attacks (Stream Name): Potential injection attacks via unvalidated stream names.

• Config Manager (CL3):

  • Security Implications:
    • Configuration File Vulnerabilities: Insecure defaults, misconfigurations, parsing vulnerabilities.
    • Sensitive Data Exposure: Plain text storage of secrets in configuration files.
    • Unauthorized Configuration Changes: Lack of access control to configuration files or API configuration endpoints.

• Scheduler (CL4):

  • Security Implications:
    • Unintended Scheduled Tasks: Injection or modification of scheduled tasks for malicious purposes.
    • Resource Exhaustion (Scheduled Tasks): DoS via poorly designed scheduled tasks.

4.3. Application Service Layer Components:

• Transcoder (AS1) (FFmpeg):

  • Security Implications:
    • FFmpeg Vulnerabilities: Known or zero-day vulnerabilities in FFmpeg.
    • Command Injection: Command injection via unsanitized stream metadata or configuration parameters passed to FFmpeg.
    • Resource Exhaustion (Transcoding Load): DoS via excessive transcoding requests.

• Recorder (AS2):

  • Security Implications:
    • Storage Location Security: Insecure storage locations for recordings leading to unauthorized access.
    • Access Control to Recordings: Lack of access control to recorded files.
    • Denial of Service (Disk Filling): DoS via excessive recording sessions filling disk space.

• Forwarder Logic (AS3):

  • Security Implications:
    • Insecure Forwarding Destinations: Forwarding streams to untrusted or compromised servers.
    • Man-in-the-Middle (MITM) Attacks (Forwarding): Interception of streams if forwarding is not over secure channels.
    • Amplification Attacks: Misuse of forwarding for amplification attacks.

• HTTP API Handler (AS4):

  • Security Implications:
    • API Authentication & Authorization: Weak or missing authentication/authorization for API endpoints.
    • Input Validation (API Requests): Injection attacks via lack of input validation in API requests (e.g., SQL injection, command injection).
    • API Rate Limiting: API abuse and DoS due to lack of rate limiting.
    • Information Disclosure (API Responses): Sensitive information disclosure in API responses.

• HLS Muxer (AS5):

  • Security Implications:
    • HLS Manifest Manipulation: Manipulation of HLS manifests for malicious purposes (content injection, redirection).
    • Access Control to HLS Content: Lack of access control to HLS manifests and segments.

• HTTP-FLV Muxer (AS6):

  • Security Implications:
    • FLV Streaming Vulnerabilities: Vulnerabilities related to insecure FLV streaming implementation.
    • Access Control to FLV Streams: Lack of access control to HTTP-FLV streams.

4.4. Data Storage Layer Components:

• Configuration Files (DS1):

  • Security Implications:
    • File System Permissions: Insecure file system permissions on configuration files.
    • Plain Text Secrets: Storage of sensitive secrets in plain text.
    • Backup and Recovery: Lack of secure backup and recovery mechanisms.

• Recorded Files (Disk) (DS2):

  • Security Implications:
    • File System Permissions: Insecure file system permissions on recorded files.
    • Data Retention Policies: Lack of proper data retention policies leading to data breaches or compliance issues.
    • Encryption at Rest: Lack of encryption for recorded files at rest.

3. Architecture, Components, and Data Flow Inference

The architecture, components, and data flow described in the Security Design Review are inferred from the SRS codebase and available documentation. As an open-source project, SRS's architecture is publicly visible through its GitHub repository (https://github.com/ossrs/srs). The design review accurately reflects the modular and layered approach of SRS.

The inference process likely involved:

• Code Analysis: Examining the SRS source code to understand the different modules, their functionalities, and interactions. This would reveal the separation into layers like Network Interface, Core Logic, and Application Services.
• Documentation Review: Analyzing the official SRS documentation, including guides, tutorials, and API references, to understand the intended architecture and usage patterns.
• Community Knowledge: Leveraging community discussions, forums, and issue trackers to gain insights into the system's design and behavior.

The provided Mermaid diagram and component descriptions in the design review are a good representation of the inferred architecture and data flow, providing a solid foundation for security analysis. The layered architecture helps in identifying security boundaries and focusing security efforts on specific components and interfaces.

4. SRS-Specific Security Recommendations and 5. Actionable Mitigation Strategies

Here are SRS-specific security recommendations and actionable mitigation strategies tailored to the identified threats, categorized by component and vulnerability type:

A. Network Interface Layer:

• RTMP Handler (NI1):

  • Threat: RTMP Protocol Weaknesses, Command Injection, Buffer Overflows, DoS.
  • Recommendation 1 (RTMP Encryption): Actionable Mitigation: Disable RTMP and prioritize RTMPS (RTMP over TLS) where possible. If RTMP is necessary for legacy encoders, ensure it's used in a controlled environment and consider network-level security controls.
  • Recommendation 2 (Input Validation): Actionable Mitigation: Implement robust input validation and sanitization for all RTMP messages, especially AMF data. Review and harden the AMF parsing logic in SRS to prevent buffer overflows and command injection.
  • Recommendation 3 (DoS Protection): Actionable Mitigation: Implement connection limits and rate limiting for RTMP connections. Configure SRS to limit the number of concurrent RTMP connections and the rate of incoming RTMP messages to prevent DoS attacks.

• WebRTC Handler (NI2):

  • Threat: WebRTC Complexity, SDP Vulnerabilities, ICE/STUN/TURN Security, DTLS/SRTP Flaws, MITM.
  • Recommendation 1 (Regular Updates): Actionable Mitigation: Keep the underlying WebRTC libraries used by SRS (if any are directly managed) and SRS itself updated to the latest versions. This ensures patching of known vulnerabilities in the WebRTC stack and SRS.
  • Recommendation 2 (SDP Sanitization): Actionable Mitigation: Implement strict SDP parsing and validation to prevent SDP injection attacks. Review the SDP handling logic in SRS and ensure proper sanitization of SDP parameters.
  • Recommendation 3 (Secure STUN/TURN): Actionable Mitigation: Use trusted and securely configured STUN/TURN servers. Ensure communication with STUN/TURN servers is over secure channels and regularly audit the security of these external dependencies.
  • Recommendation 4 (DTLS/SRTP Audit): Actionable Mitigation: Conduct a security audit of the DTLS/SRTP implementation within SRS. If SRS directly handles DTLS/SRTP, review the code for potential implementation flaws. If it relies on libraries, ensure those libraries are up-to-date and reputable.

• HTTP Handler (NI3):

  • Threat: Web Server Vulnerabilities, API Security, DoS, HLS/FLV Issues.
  • Recommendation 1 (HTTPS Enforcement): Actionable Mitigation: Enforce HTTPS for all HTTP-based services, including the API, HLS, and HTTP-FLV. Configure SRS to only accept HTTPS connections and disable HTTP where possible.
  • Recommendation 2 (API Authentication & Authorization): Actionable Mitigation: Implement strong authentication and authorization for the HTTP API. Use token-based authentication (e.g., API keys, JWT) and role-based access control to restrict API access to authorized users and actions.
  • Recommendation 3 (Input Sanitization & Output Encoding): Actionable Mitigation: Implement robust input sanitization for all HTTP request parameters and proper output encoding for API responses and dynamic content. This prevents injection attacks (like XSS) and ensures data integrity.
  • Recommendation 4 (Rate Limiting & DoS Protection): Actionable Mitigation: Implement rate limiting for HTTP requests, especially for API endpoints and resource-intensive services like HLS segment serving. Configure SRS with rate limiting mechanisms to prevent DoS attacks and API abuse.
  • Recommendation 5 (HLS Manifest Security): Actionable Mitigation: Ensure secure generation of HLS manifests, preventing manipulation and unauthorized access. Implement checks to prevent manifest tampering and consider access control mechanisms for HLS content if needed.

B. Core Logic Layer:

• Session Manager (CL1):

  • Threat: Authentication/Authorization Flaws, Session Management Weaknesses, Privilege Escalation, Resource Exhaustion.
  • Recommendation 1 (Strong Authentication): Actionable Mitigation: Implement robust authentication mechanisms for publishers, viewers (where applicable), and API clients. Use strong password policies (if applicable), multi-factor authentication for administrative access, and consider token-based authentication.
  • Recommendation 2 (Secure Session Management): Actionable Mitigation: Implement secure session management practices. Use cryptographically secure session IDs, enforce session timeouts, and store session data securely. Protect against session fixation and hijacking attacks.
  • Recommendation 3 (Principle of Least Privilege): Actionable Mitigation: Implement granular authorization and the principle of least privilege. Ensure users and components only have the necessary permissions to perform their functions.
  • Recommendation 4 (Session Limits): Actionable Mitigation: Configure session limits to prevent resource exhaustion attacks. Limit the maximum number of concurrent sessions (publishers, viewers, API clients) to prevent DoS.

• Stream Router (CL2):

  • Threat: Stream Hijacking, Unauthorized Stream Access, Injection Attacks (Stream Name).
  • Recommendation 1 (Access Control for Streams): Actionable Mitigation: Implement access control mechanisms for streams. Define permissions for publishing and viewing streams, and enforce these permissions in the stream routing logic.
  • Recommendation 2 (Stream Name Validation): Actionable Mitigation: Implement strict validation and sanitization of stream names. Prevent injection attacks via stream names by validating and sanitizing stream name inputs.
  • Recommendation 3 (Secure Routing Logic Audit): Actionable Mitigation: Conduct a security audit of the stream routing logic to identify and fix potential vulnerabilities that could lead to stream hijacking or unauthorized access.

• Config Manager (CL3):

  • Threat: Configuration File Vulnerabilities, Sensitive Data Exposure, Unauthorized Configuration Changes.
  • Recommendation 1 (Secure File Permissions): Actionable Mitigation: Set restrictive file system permissions on configuration files. Ensure only the SRS server process and authorized administrators have read/write access to configuration files.
  • Recommendation 2 (Secret Management): Actionable Mitigation: Avoid storing sensitive secrets (passwords, API keys) in plain text in configuration files. Use environment variables, secure configuration management tools (like HashiCorp Vault), or encrypted configuration files to manage secrets securely.
  • Recommendation 3 (Configuration Change Auditing): Actionable Mitigation: Implement auditing for configuration changes. Log all modifications to configuration files and API endpoints that modify configuration to track changes and detect unauthorized modifications.

• Scheduler (CL4):

  • Threat: Unintended Scheduled Tasks, Resource Exhaustion (Scheduled Tasks).
  • Recommendation 1 (Secure Task Definition): Actionable Mitigation: Restrict the ability to define or modify scheduled tasks to authorized administrators only. Implement strong authorization for any API or configuration mechanism that manages scheduled tasks.
  • Recommendation 2 (Resource Limits for Tasks): Actionable Mitigation: Implement resource limits for scheduled tasks to prevent resource exhaustion. Monitor the resource consumption of scheduled tasks and set limits to prevent DoS.
  • Recommendation 3 (Task Validation): Actionable Mitigation: Validate the configuration and parameters of scheduled tasks to prevent malicious or unintended actions.

C. Application Service Layer:

• Transcoder (AS1) (FFmpeg):

  • Threat: FFmpeg Vulnerabilities, Command Injection, Resource Exhaustion.
  • Recommendation 1 (FFmpeg Security Updates): Actionable Mitigation: Keep FFmpeg updated to the latest stable version to patch known vulnerabilities. Regularly monitor FFmpeg security advisories and apply updates promptly.
  • Recommendation 2 (Command Sanitization): Actionable Mitigation: Implement rigorous sanitization of all inputs passed to FFmpeg commands, including stream metadata and configuration parameters. Use parameterized commands or safe command construction methods to prevent command injection.
  • Recommendation 3 (Resource Limits for Transcoding): Actionable Mitigation: Implement resource limits for transcoding processes. Limit the number of concurrent transcoding sessions and monitor resource usage to prevent DoS due to excessive transcoding load. Consider using resource control mechanisms (e.g., cgroups) to limit FFmpeg process resources.

• Recorder (AS2):

  • Threat: Storage Location Security, Access Control to Recordings, DoS (Disk Filling).
  • Recommendation 1 (Secure Storage Location): Actionable Mitigation: Store recorded files in a secure location with appropriate file system permissions. Restrict access to the recording directory to authorized users and processes only.
  • Recommendation 2 (Access Control to Recordings): Actionable Mitigation: Implement access control mechanisms for recorded files. If recordings contain sensitive content, implement authentication and authorization to access recorded files.
  • Recommendation 3 (Disk Quotas & Monitoring): Actionable Mitigation: Implement disk quotas and monitoring for recording storage. Set limits on disk space used for recordings and monitor disk usage to prevent disk filling DoS attacks. Implement data retention policies to manage storage space.

• Forwarder Logic (AS3):

  • Threat: Insecure Forwarding Destinations, MITM (Forwarding), Amplification Attacks.
  • Recommendation 1 (Secure Forwarding Channels): Actionable Mitigation: Use secure protocols (e.g., RTMPS, SRT with encryption) for stream forwarding. Encrypt stream forwarding channels to prevent MITM attacks and protect stream confidentiality.
  • Recommendation 2 (Destination Validation): Actionable Mitigation: Validate and control forwarding destinations. Implement a whitelist of allowed forwarding destinations and prevent forwarding to untrusted or arbitrary servers.
  • Recommendation 3 (Rate Limiting & Control): Actionable Mitigation: Implement rate limiting and control mechanisms for stream forwarding to prevent misuse for amplification attacks. Limit the rate and volume of forwarded streams.

• HTTP API Handler (AS4):

  • Threat: API Authentication/Authorization, Input Validation, API Rate Limiting, Information Disclosure.
  • Recommendation 1 (API Security Best Practices): Actionable Mitigation: Implement API security best practices. This includes strong authentication and authorization (as mentioned earlier), input validation, output encoding, rate limiting, and secure error handling.
  • Recommendation 2 (Input Validation & Sanitization): Actionable Mitigation: Implement comprehensive input validation and sanitization for all API request parameters. Prevent injection attacks (SQL injection, command injection, etc.) by validating and sanitizing API inputs.
  • Recommendation 3 (Rate Limiting & DoS Protection): Actionable Mitigation: Implement API rate limiting to prevent API abuse and DoS attacks. Limit the number of API requests from a single IP address or user within a given time frame.
  • Recommendation 4 (Secure Error Handling & Information Disclosure Prevention): Actionable Mitigation: Implement secure error handling and prevent information disclosure in API responses. Avoid exposing sensitive information in error messages or API responses.

• HLS Muxer (AS5) & HTTP-FLV Muxer (AS6):

  • Threat: HLS Manifest Manipulation, Access Control to HLS/FLV Content, FLV Streaming Vulnerabilities.
  • Recommendation 1 (Manifest Integrity): Actionable Mitigation (HLS): Ensure the integrity of HLS manifests. Implement mechanisms to prevent manipulation of HLS manifests, such as digital signatures or checksums (if feasible and supported by SRS).
  • Recommendation 2 (Access Control): Actionable Mitigation (HLS/FLV): Implement access control mechanisms for HLS manifests, HLS segments, and HTTP-FLV streams if content access needs to be restricted. This could involve token-based access or other authentication methods.
  • Recommendation 3 (Secure Implementation Audit): Actionable Mitigation (HLS/FLV): Conduct a security audit of the HLS and HTTP-FLV muxing and streaming implementation in SRS. Review the code for potential vulnerabilities related to manifest generation, segment handling, and streaming logic.

D. Data Storage Layer:

• Configuration Files (DS1):

  • Threat: File System Permissions, Plain Text Secrets, Backup and Recovery.
  • Recommendation 1 (Secure File Permissions): Actionable Mitigation: Reinforce secure file system permissions on configuration files (already mentioned in Core Logic Layer - Config Manager).
  • Recommendation 2 (Secret Management): Actionable Mitigation: Implement secure secret management practices (already mentioned in Core Logic Layer - Config Manager).
  • Recommendation 3 (Secure Backup & Recovery): Actionable Mitigation: Implement secure backup and recovery mechanisms for configuration files. Encrypt configuration file backups and store them in a secure location.

• Recorded Files (Disk) (DS2):

  • Threat: File System Permissions, Data Retention Policies, Encryption at Rest.
  • Recommendation 1 (Secure File Permissions): Actionable Mitigation: Reinforce secure file system permissions on recorded files (already mentioned in Application Service Layer - Recorder).
  • Recommendation 2 (Data Retention Policies): Actionable Mitigation: Implement and enforce data retention policies for recorded content. Define policies for how long recordings are stored and implement automated deletion or archival mechanisms to comply with retention policies and regulations.
  • Recommendation 3 (Encryption at Rest): Actionable Mitigation: Implement encryption at rest for recorded files, especially if they contain sensitive content. Use disk encryption or file-level encryption to protect recorded data if storage is compromised.

General Recommendations Applicable Across SRS:

• Security Audits and Penetration Testing: Regularly conduct security audits and penetration testing of SRS to identify and address vulnerabilities proactively.
• Security Logging and Monitoring: Implement comprehensive security logging and monitoring to detect and respond to security incidents. Log relevant security events, API access, authentication attempts, and errors.
• Incident Response Plan: Develop and maintain an incident response plan to handle security incidents effectively.
• Security Training for Developers: Provide security training to the development team to promote secure coding practices and awareness of common vulnerabilities.
• Follow Security Best Practices: Adhere to general security best practices for server hardening, network security, and application security.

7. Conclusion

This deep security analysis of SRS, based on the provided design review, has identified various potential security vulnerabilities across its architecture and components. The provided SRS-specific recommendations and actionable mitigation strategies offer a roadmap for the development team to enhance the security posture of SRS and build more secure live streaming applications.

It is crucial to prioritize the implementation of these mitigation strategies, especially those related to authentication, authorization, input validation, secure communication (HTTPS, RTMPS, secure forwarding), and secret management. Regular security audits, penetration testing, and continuous monitoring are essential to maintain a strong security posture for SRS and protect live streaming services from evolving threats. This analysis should be considered a starting point for ongoing security efforts and should be revisited and updated as SRS evolves and new security insights emerge.