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attack-surface.md

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Attack Surface Analysis for gocolly/colly

Attack Surface: Server-Side Request Forgery (SSRF)

  • Description: An attacker can exploit the application to make requests to unintended locations, including internal resources or other external services, by manipulating the URLs that colly is instructed to scrape. This occurs when user-controlled input influences the target URLs for colly requests.
  • Colly Contribution: colly's core functionality is to make HTTP requests to URLs. If the application design allows user input to dictate these URLs without proper validation, colly becomes the mechanism through which SSRF attacks are executed.
  • Example: An application takes a user-provided website URL and uses colly to scrape it. An attacker inputs http://localhost:8080/admin/delete_user?id=1. colly, instructed by the application, makes a request to this internal URL, potentially triggering administrative actions on an internal service.
  • Impact: Critical. SSRF can lead to unauthorized access to internal resources, data breaches, denial of service of internal services, privilege escalation, and potentially remote code execution on internal systems.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict URL Validation and Sanitization: Thoroughly validate and sanitize all user inputs that are used to construct or influence the URLs scraped by colly. Implement strict allowlists of permitted domains or URL patterns.
    • URL Parsing and Component Validation: Utilize URL parsing libraries to dissect URLs and validate individual components like hostname, scheme, and port. Reject or sanitize URLs that point to internal networks, private IP ranges, or disallowed schemes (e.g., file://, gopher://).
    • Network Segmentation: Deploy the application using colly in a network segment isolated from internal networks and sensitive resources. Implement firewalls and network policies to restrict outbound traffic from the scraping application.
    • Principle of Least Privilege: Run the application with the minimum necessary permissions to limit the potential damage from an SSRF exploit.

Attack Surface: URL Manipulation and Injection (High Risk Scenarios)

  • Description: Attackers can manipulate or inject malicious URLs into the application's URL handling logic that is used to feed URLs to colly. This can cause colly to scrape unintended and potentially malicious websites or resources.
  • Colly Contribution: colly directly processes and scrapes content from the URLs it is given. If the application's URL generation or handling logic is flawed and allows for manipulation, attackers can control colly's scraping targets.
  • Example: An application constructs URLs for colly by combining a base URL with user-provided path segments. If user input is not properly sanitized, an attacker could inject path traversal sequences (e.g., ../../../malicious.com) or replace the intended path entirely, forcing colly to scrape a malicious domain instead of the intended target.
  • Impact: High. Scraping sensitive data from unexpected sources, redirection of users to phishing sites if scraped content is displayed, triggering actions on malicious websites on behalf of the application, and potential exposure of application functionality to malicious sites.
  • Risk Severity: High (when leading to scraping of sensitive data or interaction with malicious sites with potential for further exploitation).
  • Mitigation Strategies:
    • Secure URL Construction Practices: Employ URL parsing and building libraries to construct URLs safely, avoiding string concatenation which is prone to injection vulnerabilities.
    • Robust Input Validation and Sanitization: Rigorous validation and sanitization of all user inputs that contribute to URL construction.
    • URL Whitelisting and Allowlisting: Maintain a strict whitelist of allowed target domains or URL patterns. Only permit colly to scrape URLs that strictly conform to this whitelist.
    • Regular Expression Based URL Validation: Utilize regular expressions to enforce strict URL format validation and prevent the injection of unexpected characters or malicious patterns within URLs.

Attack Surface: Denial of Service via Large Responses

  • Description: A malicious website, when targeted by colly, can serve extremely large HTTP responses specifically designed to exhaust the resources of the scraping application (memory, CPU, network bandwidth), leading to a Denial of Service (DoS).
  • Colly Contribution: colly is designed to fetch and process HTTP responses. Without proper safeguards, colly can be overwhelmed by excessively large responses, consuming resources and potentially crashing the application or impacting other services on the same infrastructure.
  • Example: A malicious website, when scraped by colly, responds with a multi-gigabyte data stream. If the application lacks response size limits, colly might attempt to download and process the entire response in memory, leading to memory exhaustion and application crash, or network bandwidth saturation causing DoS.
  • Impact: High. Denial of Service (DoS) for the scraping application, potentially impacting application availability and other services sharing the same infrastructure.
  • Risk Severity: High (DoS can significantly disrupt application functionality and availability).
  • Mitigation Strategies:
    • Implement Response Size Limits in colly: Configure colly to enforce strict limits on the maximum size of HTTP responses it will download and process. This prevents the application from being overwhelmed by excessively large responses.
    • Set Request Timeouts: Configure appropriate timeouts for HTTP requests made by colly. This prevents indefinite waiting for responses and resource blocking if a target server becomes unresponsive or intentionally delays responses.
    • Resource Monitoring and Alerting: Implement monitoring of application resource usage (CPU, memory, network) to detect and alert on potential DoS attacks or resource exhaustion scenarios.
    • Rate Limiting and Concurrency Control: Implement rate limiting on scraping requests to control the frequency of requests to target websites. Configure colly's concurrency settings to limit the number of simultaneous requests and prevent overwhelming the application or target websites.