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Attack Surface Analysis for square/picasso

Attack Surface: Loading Images over HTTP (Unencrypted Connections)

  • Description: Images are fetched from servers using the insecure HTTP protocol. This allows attackers to intercept and manipulate image traffic.
  • Picasso Contribution: Picasso is configured to load images from URLs provided by the application. If the application provides HTTP URLs, Picasso will load images over unencrypted connections.
  • Example: An application loads user avatars using Picasso from HTTP URLs. An attacker on a shared Wi-Fi network intercepts the HTTP traffic and replaces a user's avatar with a malicious image containing phishing content or offensive material.
  • Impact: Phishing attacks, malware distribution (by replacing images with malicious content), information disclosure if images contain sensitive data, reputational damage to the application.
  • Risk Severity: High
  • Mitigation Strategies:
    • Enforce HTTPS for Image URLs: Ensure that the application only provides HTTPS URLs to Picasso for image loading. This should be enforced at the application level when constructing or handling image URLs.
    • Server-Side Redirection to HTTPS: Configure image servers to automatically redirect HTTP requests to HTTPS, ensuring all image delivery is encrypted.
    • Content Security Policy (CSP) - if applicable in WebView context: If images are loaded within WebViews, implement CSP to restrict image sources to HTTPS only.

Attack Surface: URL Injection/Redirection via User-Controlled Input

  • Description: If the application allows users to directly influence or provide image URLs that are then loaded by Picasso without proper validation, attackers can inject malicious URLs.
  • Picasso Contribution: Picasso directly loads and processes URLs provided to it by the application. If the application passes unsanitized user input as part of the image URL to Picasso, it becomes vulnerable to URL injection.
  • Example: An application allows users to customize their profile by entering a URL for their profile banner. An attacker enters a URL pointing to a malicious website or a phishing page. When other users view the attacker's profile, Picasso attempts to load the "banner" from the attacker-controlled URL, potentially redirecting users to the malicious site.
  • Impact: Open redirection to external malicious websites, phishing attacks, potential for serving misleading or harmful content instead of intended images, reputational damage.
  • Risk Severity: High
  • Mitigation Strategies:
    • Strict Input Validation and Sanitization: Thoroughly validate and sanitize all user input that is used to construct image URLs before passing them to Picasso. Use allowlists for URL schemes (e.g., only https://) and domains if feasible.
    • URL Parsing and Validation Libraries: Utilize robust URL parsing libraries to validate URLs and ensure they conform to expected formats and security policies.
    • Indirect URL Handling: Avoid directly using user-provided strings as URLs. Instead, use identifiers or keys that are mapped to pre-defined, validated image URLs on the server-side.
    • Content Security Policy (CSP) - if applicable in WebView context: If images are loaded within WebViews, CSP can help mitigate the impact of open redirection by restricting allowed destination URLs.