Skip to content

Latest commit

 

History

History
85 lines (54 loc) · 9.86 KB

mitigations.md

File metadata and controls

85 lines (54 loc) · 9.86 KB

Mitigation Strategies Analysis for square/picasso

Mitigation Strategy: Implement Certificate Pinning (via Picasso's OkHttpClient)

  • Description:

    1. Configure Custom OkHttpClient: Create a custom OkHttpClient instance. This is necessary because Picasso uses OkHttp for network requests, and certificate pinning is configured within OkHttp.
    2. Implement Certificate Pinning in OkHttpClient: Use CertificatePinner.Builder() to configure certificate pinning within your custom OkHttpClient. Add pins for your image server domains and their corresponding certificate hashes or public key hashes.
    3. Provide Custom OkHttpClient to Picasso Builder: When initializing Picasso, use Picasso.Builder(context).client(customOkHttpClient).build() to instruct Picasso to use your custom OkHttpClient with certificate pinning.
    4. Handle Pinning Failures: Implement error handling within your application to manage situations where certificate pinning fails. Decide on an appropriate fallback or error display mechanism.

  • List of Threats Mitigated:

    • Advanced Man-in-the-Middle (MITM) Attacks (High Severity): Certificate pinning, when configured through Picasso's underlying HTTP client, provides a strong defense against sophisticated MITM attacks, even if Certificate Authorities are compromised.

  • Impact: Significantly strengthens protection against MITM attacks specifically for image loading within Picasso, going beyond standard HTTPS validation.

  • Currently Implemented: To be determined. Check if a custom OkHttpClient is configured for Picasso using Picasso.Builder.client() and if certificate pinning is implemented within that OkHttpClient.

  • Missing Implementation: Likely missing if a custom OkHttpClient is not being provided to Picasso's Builder and certificate pinning is not explicitly configured within a custom OkHttpClient. Implementation requires modifying Picasso initialization code.

Mitigation Strategy: Control Cache Size (via Picasso Builder)

  • Description:

    1. Configure Memory Cache Size using Picasso Builder: When initializing Picasso, use Picasso.Builder.memoryCache(Cache cache). You can provide a custom LruCache implementation with a defined size limit. This directly controls Picasso's in-memory cache.
    2. Configure Disk Cache Size using Picasso Builder: Similarly, use Picasso.Builder.diskCache(DiskCache cache) to set a custom disk cache. You can use DiskLruCache or Picasso's default disk cache and configure its maxSize. This controls Picasso's disk-based cache.
    3. Determine Appropriate Cache Sizes: Analyze your application's memory and storage usage to determine suitable cache size limits. Consider device capabilities and the volume of images loaded.

  • List of Threats Mitigated:

    • Cache-Based Denial of Service (DoS) (Medium Severity): By controlling cache sizes within Picasso, you limit the potential for an attacker to fill the cache with malicious or excessively large images, preventing resource exhaustion.

  • Impact: Reduces the risk of cache-based DoS attacks specifically targeting Picasso's caching mechanism. Improves resource management related to Picasso's image caching.

  • Currently Implemented: To be determined. Check Picasso initialization code for usage of Picasso.Builder.memoryCache() and Picasso.Builder.diskCache() with custom size configurations. If not present, default Picasso caching is used without explicit size limits.

  • Missing Implementation: Potentially missing custom cache size configuration in Picasso initialization. Implementation requires modifying Picasso initialization using Picasso.Builder to set memoryCache and diskCache with size limits.

Mitigation Strategy: Cache Invalidation Strategies (using Picasso API)

  • Description:

    1. Use Picasso.invalidate(String url) for Specific Image Invalidation: When you know a specific image URL has been updated or might be compromised, use Picasso.get().invalidate(imageUrl) to remove that specific image from Picasso's cache.
    2. Use Picasso.cache.clear() for Broad Cache Clearing: In situations where a more general cache invalidation is needed (e.g., during logout, after significant data changes), use Picasso.get().cache.clear() to clear the entire Picasso cache. Use this method sparingly as it can impact performance temporarily.
    3. Integrate Invalidation with Data Update Logic: Incorporate Picasso.invalidate() calls into your application's data update mechanisms. When you refresh data that includes image URLs, invalidate the corresponding images in Picasso's cache to ensure users see the latest versions.

  • List of Threats Mitigated:

    • Serving Stale or Outdated Images (Low Severity - Functionality/User Experience): Picasso's invalidation API ensures that your application doesn't persistently display outdated images from its cache after updates.
    • Serving Potentially Compromised Cached Images (Medium Severity): Invalidation helps to remove potentially malicious images from Picasso's cache if the original image source is compromised and replaced.

  • Impact: Reduces the risk of serving stale or potentially compromised images specifically from Picasso's cache. Improves data freshness and responsiveness to image updates.

  • Currently Implemented: To be determined. Check codebase for usage of Picasso.invalidate() and Picasso.cache.clear() in relevant data update or event handling logic.

  • Missing Implementation: Potentially missing usage of Picasso's invalidation API in data update flows or scenarios where cache invalidation is needed. Implementation requires adding Picasso.invalidate() or Picasso.cache.clear() calls in appropriate parts of the application logic.

Mitigation Strategy: Sanitize Input for Custom Transformations (Used with Picasso)

  • Description:

    1. Review Custom Transformation Implementations: Examine all custom Transformation classes used with Picasso's transform() method.
    2. Identify External Input in Transformations: Within each custom transformation, determine if it processes any external input data (e.g., constructor parameters, data passed during transformation execution).
    3. Implement Sanitization and Validation within Transformations: Inside your custom Transformation code, sanitize and validate any external input data before using it in image processing logic. Use whitelisting, input validation, and appropriate encoding techniques as needed.

  • List of Threats Mitigated:

    • Injection Vulnerabilities in Custom Transformations (Low to Medium Severity - Depends on Transformation Logic): By sanitizing input within custom Picasso transformations, you prevent potential injection vulnerabilities that could arise from processing untrusted data in transformation logic.
    • Unexpected Behavior or Errors (Low to Medium Severity): Input sanitization in transformations helps prevent unexpected behavior or errors caused by malformed or malicious input data processed by your custom image transformations within Picasso.

  • Impact: Reduces the risk of vulnerabilities and errors specifically within custom image transformations used with Picasso, improving the robustness of image processing.

  • Currently Implemented: To be determined. Depends on whether custom Transformation classes are used and if input sanitization is implemented within their code.

  • Missing Implementation: Potentially missing input sanitization within custom Transformation implementations. Implementation requires modifying the code of each custom Transformation class to include input sanitization logic.

Mitigation Strategy: Resource Management for Transformations (Used with Picasso)

  • Description:

    1. Optimize Custom Transformation Logic: Review the code of your custom Transformation classes for performance bottlenecks and areas for optimization. Use efficient algorithms and data structures to minimize resource consumption.
    2. Avoid Overly Complex Transformations: Limit the complexity of image transformations, especially for large images or on resource-constrained devices. Break down complex transformations into simpler steps if possible.
    3. Background Thread Execution (Verification): While Picasso handles background execution by default, double-check that your custom Transformation implementations are also designed to execute efficiently on background threads and avoid blocking the main thread.

  • List of Threats Mitigated:

    • Client-Side Denial of Service (DoS) via Resource Exhaustion (Medium Severity): By optimizing resource usage in transformations used with Picasso, you reduce the risk of client-side DoS due to excessive resource consumption during image processing.

  • Impact: Reduces the risk of client-side DoS specifically related to resource-intensive image transformations performed by Picasso. Improves application performance and responsiveness, especially during image loading and processing.

  • Currently Implemented: Partially implemented by Picasso's default background thread execution. However, optimization of custom transformation logic might be missing.

  • Missing Implementation: Potentially missing optimization of custom transformation code for resource efficiency. Implementation requires reviewing and optimizing the code within custom Transformation classes to minimize resource usage.