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Attack Tree Analysis for lizardbyte/sunshine

Objective: Compromise Host/Client via Sunshine

Attack Tree Visualization

Goal: Compromise Host/Client via Sunshine

├── 1. Remote Code Execution (RCE) on Host │ ├── 1.1. Exploit Input Validation Flaws in Sunshine │ │ ├── 1.1.1. Command Injection in Application Configuration [CRITICAL] │ │ │ └── 1.1.1.1. Craft malicious input in application settings (e.g., "do" command, "prep" command, "detach" command) that executes arbitrary commands when parsed by Sunshine. [HIGH RISK] │ │ └── 1.1.3. Path Traversal in File Access [CRITICAL] │ │ │ └── 1.1.3.1. If Sunshine allows specifying file paths (e.g., for configuration files or application-specific data), use "../" sequences to access files outside the intended directory. [HIGH RISK] │ ├── 1.2. Exploit Vulnerabilities in Underlying Libraries (e.g., FFmpeg, SDL) │ │ ├── 1.2.1. Known CVEs in FFmpeg [CRITICAL] │ │ │ └── 1.2.1.1. Craft a malicious video stream that triggers a known vulnerability in FFmpeg's decoding process, leading to RCE. [HIGH RISK] │ └── 1.3. Exploit Weaknesses in Authentication/Authorization │ ├── 1.3.1. Bypass Authentication [CRITICAL] │ │ └── 1.3.1.1. If authentication is optional or poorly implemented, connect directly to the Sunshine server without credentials. [HIGH RISK] │ ├── 2. Remote Code Execution (RCE) on Client │ ├── 2.1. Malicious Host Compromises Client [CRITICAL] │ │ ├── 2.1.1. Host Sends Malicious Input Events │ │ │ └── 2.1.1.1. A compromised host sends crafted keyboard/mouse events to the client that trigger unintended actions, potentially leading to RCE (e.g., opening a malicious URL, executing a script). [HIGH RISK] │ ├── 3. Information Disclosure │ ├── 3.1. Capture Screen Contents │ │ └── 3.1.1. Unauthorized Access to Stream [CRITICAL] │ │ └── 3.1.1.1. Connect to the Sunshine server without proper authentication and view the host's screen. [HIGH RISK] │ └── 3.4. Network Eavesdropping │ └── 3.4.1. Unencrypted Traffic [CRITICAL] │ └── 3.4.1.1. If the connection between the host and client is not properly encrypted, capture the network traffic and extract sensitive data. [HIGH RISK] │ └── 5. Man-in-the-Middle (MitM) └── 5.2.2 Weak TLS Configuration [CRITICAL] └── 5.2.2.1 Exploit weak ciphers or protocols to decrypt or modify the traffic. [HIGH RISK]

Attack Tree Path: 1.1.1.1. Command Injection in Application Configuration

  • Description: The attacker crafts malicious input within the application's configuration settings. These settings (like "do," "prep," or "detach" commands) are designed to execute system commands. If Sunshine doesn't properly sanitize this input, the attacker can inject their own commands, which will then be executed by the Sunshine server with the server's privileges.
  • Likelihood: Medium (Depends on the presence and effectiveness of input sanitization)
  • Impact: Very High (Complete control over the host system)
  • Effort: Low (Simple to craft malicious input if vulnerable)
  • Skill Level: Intermediate (Requires understanding of command injection and the target system)
  • Detection Difficulty: Medium (May be logged, but the attacker might try to obfuscate the commands)
  • Mitigation:
    • Strict Input Validation: Use a whitelist of allowed characters and commands. Reject any input that doesn't strictly conform to the expected format.
    • Avoid Shell Execution: If possible, avoid using shell commands entirely. If necessary, use parameterized commands or APIs that prevent command injection.
    • Principle of Least Privilege: Run Sunshine with the lowest possible privileges necessary.

Attack Tree Path: 1.1.3.1. Path Traversal in File Access

  • Description: If Sunshine allows users to specify file paths (for configuration, application data, etc.), an attacker can use ".." (parent directory) sequences to navigate outside the intended directory. This allows them to read or potentially write to arbitrary files on the system.
  • Likelihood: Medium (Depends on how file paths are handled)
  • Impact: High (Read/write access to arbitrary files, potentially including sensitive configuration files or system files)
  • Effort: Low (Simple to craft path traversal payloads)
  • Skill Level: Intermediate (Requires understanding of file system structures)
  • Detection Difficulty: Medium (File access logs might reveal unusual activity)
  • Mitigation:
    • Sanitize File Paths: Remove or encode any ".." sequences. Validate that the resulting path is within the intended directory.
    • Chroot Jail (or Similar): Confine Sunshine's file access to a specific directory, preventing it from accessing files outside that directory.
    • Principle of Least Privilege: Run Sunshine with limited file system access.

Attack Tree Path: 1.2.1.1. Known CVEs in FFmpeg

  • Description: FFmpeg is a widely used multimedia library. If Sunshine uses an outdated or vulnerable version of FFmpeg, an attacker can craft a malicious video stream that exploits a known vulnerability (identified by a CVE number). This can lead to remote code execution on the host.
  • Likelihood: Medium (Depends on the FFmpeg version and whether patches have been applied)
  • Impact: Very High (Complete control over the host system)
  • Effort: Medium (Exploits for known CVEs are often publicly available)
  • Skill Level: Intermediate to Advanced (Requires understanding of exploit development or using existing exploits)
  • Detection Difficulty: Medium (Intrusion Detection Systems (IDS) might detect known exploit signatures)
  • Mitigation:
    • Keep FFmpeg Updated: Regularly update FFmpeg to the latest stable version.
    • Vulnerability Scanning: Use a vulnerability scanner to identify outdated or vulnerable components.
    • Sandboxing: Run the FFmpeg decoding process in a sandboxed environment to limit the impact of a successful exploit.

Attack Tree Path: 1.3.1.1. Bypass Authentication

  • Description: If Sunshine's authentication mechanism is optional, disabled, or poorly implemented (e.g., using weak default credentials, vulnerable to brute-force attacks), an attacker can connect directly to the server without providing valid credentials.
  • Likelihood: Low to Medium (Depends on the default configuration and whether the administrator has changed default settings)
  • Impact: Very High (Full access to Sunshine's features and the host's screen/input)
  • Effort: Very Low (Trivial if authentication is disabled or weak)
  • Skill Level: Novice (No specialized skills required)
  • Detection Difficulty: Easy (Failed login attempts might be logged, but successful unauthenticated connections might not be)
  • Mitigation:
    • Enforce Strong Authentication: Make authentication mandatory and non-bypassable.
    • Strong Passwords: Use strong, randomly generated passwords. Avoid default credentials.
    • Secure Password Storage: Use secure password hashing algorithms (e.g., bcrypt, Argon2).
    • Account Lockout: Implement account lockout policies to prevent brute-force attacks.

Attack Tree Path: 2.1.1.1. Host Sends Malicious Input Events

  • Description: If the host system is already compromised (e.g., through one of the RCE vulnerabilities on the host), the attacker can use Sunshine to send malicious keyboard and mouse events to the client. This could trick the client into opening a malicious URL, executing a script, or performing other actions that lead to client compromise.
  • Likelihood: Medium (Requires the host to be compromised first)
  • Impact: High (Compromise of the client system)
  • Effort: Medium (Requires crafting malicious input events)
  • Skill Level: Intermediate (Requires understanding of client-side vulnerabilities and input handling)
  • Detection Difficulty: Medium (Unusual or unexpected input events might be noticeable to the user)
  • Mitigation:
    • Client-Side Input Validation: The client application should validate input events received from the host and reject any that are suspicious or unexpected.
    • Trusted Host Model: The client could be configured to only accept input from explicitly trusted hosts.
    • User Awareness: Educate users to be cautious of unexpected input events.

Attack Tree Path: 3.1.1.1. Unauthorized Access to Stream

  • Description: This is a direct consequence of bypassing authentication (1.3.1.1). If an attacker can connect to the Sunshine server without credentials, they can view the host's screen.
  • Likelihood: Low (If authentication is enforced)
  • Impact: High (Exposure of sensitive visual information displayed on the host's screen)
  • Effort: Very Low (Trivial if authentication is bypassed)
  • Skill Level: Novice (No specialized skills required)
  • Detection Difficulty: Easy (If authentication is logged, unauthorized connections will be apparent)
  • Mitigation: (Same as 1.3.1.1 - Enforce strong authentication)

Attack Tree Path: 3.4.1.1. Unencrypted Traffic

  • Description: If the communication between the Sunshine host and client is not encrypted (e.g., TLS is not enabled or is improperly configured), an attacker on the same network can passively eavesdrop on the traffic and capture sensitive data, including screen contents, keyboard input, and clipboard data.
  • Likelihood: Low (If TLS is enforced by default)
  • Impact: High (Exposure of all transmitted data)
  • Effort: Low (Passive network sniffing is relatively easy)
  • Skill Level: Intermediate (Requires understanding of network protocols and sniffing tools)
  • Detection Difficulty: Easy (Unencrypted traffic is easily identifiable)
  • Mitigation:
    • Enforce TLS Encryption: Make TLS encryption mandatory for all communication.
    • Strong Ciphers and Protocols: Use only strong, modern ciphers and protocols. Disable weak or outdated options.
    • Certificate Validation: The client should properly validate the server's TLS certificate.

Attack Tree Path: 5.2.2.1 Exploit Weak TLS Configuration

  • Description: Even if TLS is enabled, if it's configured with weak ciphers or protocols (e.g., SSLv3, RC4), an attacker might be able to decrypt or modify the traffic, effectively performing a Man-in-the-Middle (MitM) attack.
  • Likelihood: Low (If strong TLS configuration is enforced)
  • Impact: High (Exposure and potential modification of encrypted data)
  • Effort: Medium to High (Requires exploiting specific weaknesses in the TLS configuration)
  • Skill Level: Advanced (Requires deep understanding of TLS and cryptography)
  • Detection Difficulty: Medium (Requires analyzing the TLS handshake and traffic for weaknesses)
  • Mitigation:
    • Strong TLS Configuration: Use only strong ciphers and protocols (e.g., TLS 1.3, AES-256-GCM). Disable weak or outdated options.
    • Certificate Pinning: The client can pin the server's certificate to prevent MitM attacks using fraudulent certificates.
    • Regular Security Audits: Regularly review the TLS configuration to ensure it remains secure.