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attack-surface.md

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Attack Surface Analysis for fizzed/font-mfizz

Attack Surface: Font File Parsing Vulnerabilities (High to Critical)

  • Description: Exploitation of vulnerabilities within browser or operating system font parsing libraries when processing font files provided by font-mfizz. A maliciously crafted font file can trigger these vulnerabilities.
  • Font-mfizz Contribution: font-mfizz provides font files (TTF, WOFF, etc.) that are processed by the user's browser. If these files are maliciously crafted or if standard font files trigger existing browser parsing bugs, using font-mfizz exposes the application to this risk.
  • Example: An attacker replaces a legitimate font-mfizz font file on the server with a specially crafted malicious font. When a user's browser loads a page using font-mfizz, it downloads and parses this malicious font. This triggers a critical buffer overflow vulnerability in the browser's font rendering engine, allowing the attacker to execute arbitrary code on the user's machine.
  • Impact:
    • Remote Code Execution (RCE) - Critical: Successful exploitation can allow an attacker to gain complete control over the user's system.
    • Denial of Service (DoS) - High: A malformed font file could crash the browser or rendering engine, causing a denial of service for the user.
  • Risk Severity: Critical (for RCE scenarios) to High (for DoS scenarios).
  • Mitigation Strategies:
    • Mandatory Browser and OS Updates: Users must be strongly encouraged to keep their browsers and operating systems updated. Vendors regularly patch font parsing vulnerabilities, and updates are crucial for protection. Developers should inform users about this necessity.
    • Content Security Policy (CSP) - Strict font-src Directive: Implement a strict CSP with a tightly controlled font-src directive. Only allow font loading from trusted, explicitly defined origins (ideally your own domain or a reputable CDN you control). Avoid unsafe-inline or overly permissive font-src directives.
    • Subresource Integrity (SRI) - For CDN Usage: If font-mfizz font files are served from a CDN, always use Subresource Integrity (SRI) tags in your HTML. This ensures that the browser verifies the integrity of the downloaded font files against a cryptographic hash, preventing the loading of tampered files from a compromised CDN or during a Man-in-the-Middle attack.
    • Regularly Review and Update Font-mfizz (Less Direct but Good Practice): While less likely to contain vulnerabilities within the font files themselves from the font-mfizz project, keeping the library updated is a general security best practice. It ensures you are using the intended files and potentially benefits from any community security awareness.

Attack Surface: Insecure Delivery Leading to Malicious Font Injection (High)

  • Description: Insecure delivery mechanisms for font-mfizz font files (e.g., over unencrypted HTTP) allow attackers to intercept and replace legitimate font files with malicious ones. This then leverages Font File Parsing Vulnerabilities.
  • Font-mfizz Contribution: font-mfizz font files need to be delivered to the user's browser. Insecure delivery directly enables the injection of malicious font files in place of the intended font-mfizz icons.
  • Example: Font files are served over HTTP. An attacker performs a Man-in-the-Middle (MitM) attack on the network. They intercept the font file download and inject a malicious font file. The user's browser, expecting a legitimate font-mfizz font, downloads and processes the attacker's malicious font, potentially triggering a parsing vulnerability and leading to Remote Code Execution.
  • Impact:
    • Remote Code Execution (RCE) - Critical (via chained Font Parsing Vulnerability): If the injected malicious font exploits a parsing vulnerability, it can lead to RCE.
    • Denial of Service (DoS) - High: An injected malformed font can cause browser crashes and DoS.
  • Risk Severity: High (due to the potential for chaining with parsing vulnerabilities to achieve RCE, and the feasibility of MitM attacks in certain network contexts).
  • Mitigation Strategies:
    • Enforce HTTPS for All Font Delivery: Mandatory serving of font-mfizz font files over HTTPS is critical. This encrypts the communication channel and prevents Man-in-the-Middle attacks that could be used to inject malicious fonts. There is no acceptable reason to serve font files over unencrypted HTTP in a production environment.
    • Secure Server and CDN Infrastructure: Harden and regularly audit the security of servers and CDNs hosting font-mfizz files. Prevent unauthorized access and ensure file integrity to avoid attackers replacing legitimate files with malicious ones at the source.
    • File Integrity Monitoring (Server-Side): Implement server-side file integrity monitoring for the font-mfizz font files. This can detect unauthorized modifications to the files on the server, alerting administrators to potential compromises.
    • Principle of Least Privilege (Server Access): Restrict write access to the directories containing font-mfizz files on the server to only necessary processes and users. This minimizes the risk of accidental or malicious modification of the font files.