Skip to content

Latest commit

 

History

History
57 lines (50 loc) · 4.77 KB

attack-surface.md

File metadata and controls

57 lines (50 loc) · 4.77 KB

Attack Surface Analysis for asciinema/asciinema-player

Attack Surface: 1. Malicious Asciicast Data (XSS via Control Sequences)

  • Description: Attackers craft malicious asciicast files containing specially crafted ANSI escape codes or other control sequences that, when parsed and rendered by the player, inject and execute arbitrary JavaScript code in the context of the user's browser.
  • How asciinema-player Contributes: The player is directly responsible for parsing and rendering the asciicast data, including interpreting control sequences. Its vulnerability to this attack depends entirely on the robustness of its input sanitization and output encoding.
  • Example:
    • An attacker creates an asciicast file containing the following sequence (simplified): \x1b[31m<script>alert('XSS');</script>\x1b[0m. If the player doesn't properly escape the < and > characters, the browser will execute the JavaScript. Real-world attacks would be more obfuscated.
  • Impact:
    • Data Theft: Stealing cookies, session tokens, or sensitive data.
    • Session Hijacking: Taking over the user's session.
    • Website Defacement: Modifying page content.
    • Phishing: Displaying fake login forms.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict Whitelisting of Control Sequences: Maintain a whitelist of only essential ANSI escape codes. Reject any sequence not on the whitelist. This is the most crucial mitigation.
    • Robust Contextual Output Encoding: Escape all special characters (<, >, &, ", ') within the terminal output before inserting it into the DOM. Use appropriate escaping methods based on context.
    • Content Security Policy (CSP): Implement a strict CSP to restrict script sources. This is a defense-in-depth measure. Use script-src, style-src, and default-src.
    • Avoid innerHTML: Use safer DOM methods like textContent, createElement.
    • Fuzz Testing: Test the player with malformed and unexpected input, including random control sequences.

Attack Surface: 2. Resource Exhaustion (Denial of Service)

  • Description: Attackers craft asciicast files designed to consume excessive resources (CPU, memory) on the client-side (browser), leading to a denial-of-service.
  • How asciinema-player Contributes: The player's rendering engine and its handling of large or rapidly updating asciicast data directly determine its susceptibility.
  • Example:
    • Massive Output: An asciicast file with millions of lines of text.
    • Rapid Updates: An asciicast with a very high frame rate.
    • Nested Control Sequences: Deeply nested control sequences causing excessive parser stack usage.
  • Impact:
    • Browser Freeze/Crash: The user's browser becomes unresponsive.
    • System Slowdown: The user's system may become slow.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Size Limits: Enforce limits on the asciicast file size.
    • Output Limits: Limit the number of lines/characters rendered. Use virtual scrolling.
    • Frame Rate Limiting: Limit the maximum frame rate.
    • Timeouts: Implement timeouts for parsing and rendering.
    • Memory Monitoring: Monitor memory usage and take action if it exceeds a threshold.
    • Progressive Loading: Load and process data in chunks.

Attack Surface: 3. Server-Side Request Forgery (SSRF) - If applicable

  • Description: Only relevant if the player fetches asciicast data from user-provided URLs. Attackers provide a URL that causes the player to make requests to internal systems.
  • How asciinema-player Contributes: If the player allows arbitrary URLs to be loaded, it's a potential SSRF vector.
  • Example:
    • An attacker provides a URL like http://localhost:8080/admin or http://169.254.169.254/latest/meta-data/.
  • Impact:
    • Access to Internal Services: Access internal APIs, databases.
    • Information Disclosure: Leak sensitive internal network information.
  • Risk Severity: High (if applicable)
  • Mitigation Strategies:
    • Strict URL Whitelisting: Only allow loading from trusted domains. Do not allow arbitrary user-provided URLs.
    • Input Validation: If user-provided URLs are unavoidable, rigorously validate them.
    • Network Segmentation: Segment the server hosting the application from internal networks.
    • Disable Local File Access: Ensure that player cannot access local files.