Attack Surface: Unintentional Denial of Service (DoS) Against Target Website (via Colly's Request Mechanism)
Colly, due to its configuration, sends an excessive number of requests to a target website, overwhelming its server and causing a denial-of-service. This is a direct consequence of Colly's core functionality.
* How Colly Contributes: Colly's ability to make automated, high-frequency requests, especially with Async = true and without proper rate limiting (LimitRule), is the direct cause of this risk. Colly is the attack vector.
* Example: A Colly scraper configured with Async = true and no LimitRule, rapidly fetching thousands of pages from a small website.
* Impact: Target website unavailability; potential legal action; reputational damage.
* Risk Severity: High
* Mitigation Strategies:
* Rate Limiting (colly.LimitRule): Mandatory. Implement strict rate limiting using colly.LimitRule. This is the primary defense. Choose appropriate delays based on the target website's capacity.
* Asynchronous Requests with Control (colly.Async): Use colly.Async only in conjunction with colly.LimitRule. Never use Async without rate limiting.
* Respect robots.txt (via Colly): Use colly.DisallowedDomains or a custom robots.txt parser integrated with Colly to avoid crawling disallowed areas.
* Dynamic Rate Adjustment (based on Colly's responses): Monitor HTTP response codes received by Colly (e.g., 429, 503) and dynamically adjust the scraping rate (e.g., using a callback on OnError).
* Exponential Backoff (within Colly's request handling): Implement an exponential backoff strategy within Colly's request handling, increasing the delay after failed or rate-limited requests.
Attack Surface: Malicious Content Parsing (Exploiting Colly's Parsers)
A malicious website crafts its HTML, CSS, or JavaScript to exploit vulnerabilities within Colly's parsing logic or its underlying dependencies. This is a direct attack on Colly's parsing capabilities.
* How Colly Contributes: Colly's core function is to parse web content. This parsing process, performed by Colly and its dependencies, is the direct target of this attack.
* Example: A website includes a specially crafted HTML tag designed to trigger a buffer overflow in Colly's HTML parser (or the underlying Go html package).
* Impact: Application crash; denial-of-service; potential remote code execution (RCE) within your application (if a vulnerability in Colly or its dependencies is exploited).
* Risk Severity: Critical
* Mitigation Strategies:
* Resource Limits (colly.MaxBodySize): Set a reasonable colly.MaxBodySize to limit the amount of data Colly processes, mitigating some buffer overflow risks.
* Timeouts (colly.SetRequestTimeout): Use colly.SetRequestTimeout to prevent Colly from hanging on malicious responses.
* Dependency Management (for Colly): Keep Colly and its dependencies (especially Go itself) up-to-date. This is crucial for patching vulnerabilities in the parsing libraries.
* Fuzz Testing (of Colly): Directly fuzz test Colly's parsing functions (and the underlying libraries it uses) with malformed inputs to identify vulnerabilities.
* Disable Javascript Execution: If Javascript execution is not required, do not enable it.
Attack Surface: Server-Side Request Forgery (SSRF) (via Colly's URL Handling)
If the URLs that Colly accesses are influenced by user input, an attacker can use Colly to make requests to internal systems or other unintended targets. Colly becomes the tool for the SSRF.
* How Colly Contributes: Colly's fundamental purpose is to make requests to the URLs it's given. If those URLs are attacker-controlled, Colly directly facilitates the SSRF attack.
* Example: An application allows users to input a URL for Colly to scrape. An attacker provides an internal IP address (e.g., http://192.168.1.1/admin) or a cloud metadata endpoint.
* Impact: Exposure of internal systems; potential for lateral movement; access to sensitive cloud resources.
* Risk Severity: Critical
* Mitigation Strategies:
* Strict Input Validation (before passing to Colly): Never allow users to directly control the full URL passed to Colly.
* Whitelisting (for Colly's targets): Use a predefined, whitelisted set of allowed domains/paths for Colly. User input should only be used to select from this whitelist, never to construct the URL directly.
* Network Segmentation (for Colly's runtime): Run the Colly application in a network environment with severely limited access to internal resources. Use firewalls to restrict outbound connections from the Colly process.
* DNS Resolution Control (for Colly): Consider using a custom DNS resolver (that Colly uses) which only resolves to the whitelisted domains.