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attack-surface.md

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Attack Surface Analysis for dart-lang/http

Attack Surface: URL Injection

  • Description: Attackers can manipulate the URL used in HTTP requests by injecting malicious code or parameters. This leads to the http package making requests to unintended or malicious locations.
  • How http contributes: The http package's functions like http.get(Uri.parse(userInput)) directly process URLs provided as strings or Uri objects. If these URLs are constructed from unsanitized user input, the http package will execute requests to attacker-controlled URLs.
  • Example: An application uses http.get(Uri.parse(userInput)) where userInput is taken directly from a user. An attacker provides https://example.com/api?param=value&redirect=//malicious.site. The http package will attempt to fetch content from https://example.com/api?param=value&redirect=//malicious.site, potentially leading to redirection to malicious.site depending on server-side behavior.
  • Impact: Redirection to phishing sites, exfiltration of sensitive data to attacker-controlled servers, bypassing intended access controls, potential server-side vulnerability exploitation if the manipulated URL is processed by the backend.
  • Risk Severity: High
  • Mitigation Strategies:
    • Strict Input Validation: Thoroughly validate and sanitize all user-provided input before constructing URLs that are passed to http methods.
    • Secure URL Construction: Use secure URL parsing and construction methods. Avoid string concatenation of user input directly into URLs. Utilize Uri class methods for safe URL manipulation and parameter encoding.
    • Parameterization: Favor parameterized queries over embedding user input directly into URL paths.
    • Content Security Policy (CSP) for Web Contexts: Implement CSP headers in web applications to limit the impact of potential redirection vulnerabilities initiated via http requests.

Attack Surface: Header Injection

  • Description: Attackers can inject malicious headers into HTTP requests by manipulating header values provided to the http package. This can lead to server-side misbehavior or exploitation of intermediary systems.
  • How http contributes: The http package allows setting custom headers via the headers parameter in request methods (e.g., http.get(url, headers: {'X-Custom-Header': userInput})). If userInput is not sanitized, attackers can inject arbitrary headers.
  • Example: An application uses http.post(url, headers: {'User-Agent': userInput}) where userInput is directly from user input. An attacker provides Evil-Header: Malicious-Value\r\nUser-Agent: My-Legit-Agent. The http package will send these headers. The server or intermediary systems might interpret Evil-Header: Malicious-Value as a separate header due to the newline injection (\r\n), leading to unintended behavior.
  • Impact: Server-side misbehavior, bypassing security controls, potential exploitation of vulnerabilities in proxies or servers that process headers, information disclosure through manipulated headers.
  • Risk Severity: High
  • Mitigation Strategies:
    • Header Value Sanitization: Sanitize and validate user input intended for HTTP header values before passing them to the headers parameter in http methods. Remove or encode characters that could be interpreted as header separators or control characters (e.g., newline characters, colon).
    • Avoid User-Controlled Headers (Where Possible): Minimize the use of user-controlled headers. If custom headers are necessary, use a whitelist approach for allowed header names and strictly validate values.
    • Secure Server-Side Header Handling: Ensure backend systems are robust against header injection attacks and properly handle potentially unexpected or malicious headers sent by the http client.

Attack Surface: Unvalidated Redirects

  • Description: If an application relies on the http package's default redirect following behavior without validating the redirect target, attackers can force the application to follow redirects to malicious sites.
  • How http contributes: The http package, by default, automatically follows HTTP redirects. If an application uses http to fetch resources and doesn't explicitly control or validate redirects, it can be vulnerable.
  • Example: An application uses http.get(userInputUrl) to fetch content. An attacker provides a userInputUrl that initially points to a legitimate site but redirects (via HTTP 301/302) to a phishing site. The http package, by default, will follow this redirect and the application might unknowingly process content from or redirect the user to the malicious site.
  • Impact: Phishing attacks, malware distribution, exposure to malicious content, potential for further attacks if the application processes content from the malicious redirect target without validation.
  • Risk Severity: High
  • Mitigation Strategies:
    • Redirect Validation: When using http to fetch resources, especially from user-provided or untrusted sources, validate the target URL of redirects before allowing the http package to follow them. Check against a whitelist of allowed domains or implement other validation logic.
    • Disable Automatic Redirects and Handle Manually: Configure the http client to not automatically follow redirects (using Client options if available, or by inspecting response codes). Implement manual redirect handling with explicit validation of the Location header before making a new request.
    • Inform Users (If Necessary): If redirection is required and validation is complex, consider informing users about potential redirects and the target domain before proceeding, especially in user-facing applications.