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Threat Model Analysis for asciinema/asciinema-player

Threat: Malicious Escape Sequence Execution within the Player

  • Description: A vulnerability in the player's escape sequence parsing or handling logic allows a crafted asciicast to execute unintended actions within the player's virtual terminal emulation. This is distinct from XSS in the hosting application; it's about exploiting the player's internal logic. This could lead to unexpected behavior within the rendered terminal, potentially setting the stage for further exploits.
    • Impact:
      • Critical: If the vulnerability allows escaping the virtual terminal and affecting the browser context (e.g., through a browser bug triggered by the player), this could lead to Remote Code Execution (RCE). This is a low-probability but high-impact scenario.
      • High: Disruption of the player's internal state, leading to incorrect rendering, crashes, or denial of service. This could also be a stepping stone to other vulnerabilities.
    • Affected Component:
      • src/terminal.js (Virtual terminal emulation and escape sequence handling).
      • Any component responsible for parsing and interpreting escape sequences (potentially within terminal.js or related modules).
    • Risk Severity: Critical (if RCE is possible), High (for disruption of player state).
    • Mitigation Strategies:
      • Robust Escape Sequence Handling: Implement a secure and well-defined escape sequence parser that strictly adheres to known standards and rejects any invalid or ambiguous sequences.
      • Formal Grammar: Consider using a formal grammar (e.g., a parser generator) to define the allowed escape sequences, reducing the risk of parsing errors.
      • Fuzz Testing: Extensively fuzz test the escape sequence parsing logic with a wide variety of valid and invalid inputs.
      • Code Review: Thoroughly review the code responsible for handling escape sequences, looking for potential vulnerabilities such as buffer overflows, integer overflows, or logic errors.
      • Sandboxing (Browser Level): While this threat is within the player, browser-level sandboxing (iframe) still provides a crucial layer of defense against potential escalation to RCE.

Threat: ReDoS via Malformed Escape Sequences (within Player)

  • Description: An attacker crafts an asciicast with specially designed escape sequences that trigger catastrophic backtracking in regular expressions used internally by the player for parsing or rendering (e.g., within the terminal.js component). This is a direct attack on the player's code.
    • Impact:
      • High: Denial of Service (DoS) by causing the player to consume excessive CPU, leading to browser unresponsiveness. This directly impacts the player's functionality.
    • Affected Component:
      • Any component using regular expressions for parsing or rendering, particularly within src/terminal.js or related modules that handle escape sequences.
    • Risk Severity: High.
    • Mitigation Strategies:
      • Regular Expression Auditing: Thoroughly audit all regular expressions used within the player for ReDoS vulnerabilities. Use automated tools to assist with this.
      • Regular Expression Simplification: Simplify regular expressions where possible to reduce the risk of backtracking.
      • Timeout Mechanisms: Implement timeouts for regular expression operations within the player to prevent them from running indefinitely.
      • Alternative Parsing: Consider using alternative parsing techniques (e.g., parser combinators) that are less susceptible to ReDoS.

Threat: Denial of Service via Excessive Memory Consumption (within Player)

  • Description: A vulnerability in the player's memory management allows a crafted asciicast (even if seemingly valid) to cause the player to allocate excessive amounts of memory, leading to browser crashes or unresponsiveness. This is a direct attack on the player's resource handling.
    • Impact:
      • High: Denial of Service (DoS).
    • Affected Component:
      • src/player.js (Main player logic).
      • src/asciicast.js (Asciicast data parsing).
      • src/terminal.js (Virtual terminal emulation).
    • Risk Severity: High.
    • Mitigation Strategies:
      • Memory Management Review: Thoroughly review the player's code for potential memory leaks or inefficient memory allocation patterns.
      • Resource Limits (Within Player): If possible, implement internal limits on the amount of memory the player can allocate. This is challenging in JavaScript but can be explored.
      • Progressive Rendering: Implement progressive rendering to avoid loading the entire asciicast into memory at once, if the player's architecture allows.
      • Garbage Collection Awareness: Write code that is mindful of JavaScript's garbage collection, avoiding patterns that might hinder garbage collection.

Threat: Bypassing Sanitization via Obfuscation (within Player's parsing logic)

  • Description: An attacker crafts an asciicast that uses unusual or obfuscated escape sequences or control characters to bypass the player's internal parsing logic, even if the hosting application has its own sanitization. This targets vulnerabilities in how the player itself interprets the asciicast data.
    • Impact:
      • Critical: If the bypassed content allows escaping the virtual terminal and affecting the browser, it could lead to RCE (low probability, high impact).
      • High: Disruption of the player's internal state, leading to incorrect rendering, crashes, or DoS.
    • Affected Component:
      • src/asciicast.js (Asciicast data parsing and processing).
      • Any component handling escape sequence parsing within the player.
    • Risk Severity: Critical/High
    • Mitigation Strategies:
      • Whitelist-Based Parsing: Within the player's parsing logic, use a strict whitelist of allowed escape sequences and control characters. Reject anything not explicitly allowed.
      • Formal Grammar (Parser): Use a formal grammar and a robust parser (e.g., generated by a parser generator) to define and enforce the allowed asciicast format.
      • Fuzz Testing: Extensively fuzz test the player's parsing logic with a wide range of unusual and unexpected inputs, including obfuscated sequences.
      • Multiple Parsing Stages: If feasible, consider multiple stages of parsing and validation within the player.