Kindle Web DRM Breaking Randomized SVG Glyph Obfuscation wit...

[carlospolop]

🤖 Automated Content Update

This PR was automatically generated by the HackTricks News Bot based on a technical blog post.

📝 Source Information

• Blog URL: https://blog.pixelmelt.dev/kindle-web-drm/
• Blog Title: Kindle Web DRM: Breaking Randomized SVG Glyph Obfuscation with Raster Hashing + SSIM
• Suggested Section: Basic Forensic Methodology -> Specific Software/File-Type Tricks -> SVG/Font Glyph Analysis & Web DRM Deobfuscation (raster hashing + SSIM)

🎯 Content Summary

Goal: Reverse‑engineer Kindle Cloud Reader’s web DRM/obfuscation to extract complete book text and layout for personal backup.

Acquisition flow (Kindle Cloud Reader):
• Target endpoint: https://read.amazon.com/renderer/render
• Required auth/materials: (1) session cookies from a normal Amazon login, (2) a rendering token obtained via the startReading API call, and (3) an ADP session token (additional auth).
• Response: a TAR archive pe...

🔧 Technical Details

Token‑gated extraction from a web reader: When a web reader gates content behind ephemeral tokens, replicate the browser’s session cookies and obtain all runtime tokens (e.g., a rendering token from a startReading call and any extra session/ADP tokens). Use the same headers to fetch small paginated archives (here, 5 pages/TAR) that contain both placement data and glyph/vector assets.

Defeating per‑request glyph randomization: If text is delivered as request‑scoped glyph IDs, ignore numeric IDs and fingerprint the shapes. Rasterize each SVG glyph to an image, compute a perceptual hash, and treat that hash as a stable cross‑request glyph identifier to collapse many randomized “alphabets” into one.

Bypassing SVG anti‑scraping path tricks: Micro relative moves (e.g., m3,1, m1,6, m-4,-7) can confuse vector parsers. Render filled paths with a robust SVG engine instead of doing coordinate/path differencing...

🤖 Agent Actions

I analyzed the repository structure and existing content and found no coverage of SVG glyph obfuscation or web DRM deobfuscation techniques. This topic fits best under Basic Forensic Methodology → Specific Software/File Type Tricks, alongside other file-type and software analysis techniques (PDF, Office, ZIP, etc.). I created a new page with a complete, reproducible methodology and code for defeating per-request randomized SVG glyph obfuscation using raster hashing and SSIM, and linked it from the section’s README.

What I updated:

• Added a new page:
  • src/generic-methodologies-and-resources/basic-forensic-methodology/specific-software-file-type-tricks/svg-font-glyph-analysis-and-web-drm-deobfuscation.md
  • Contents include:
    • Acquisition flow (Kindle Cloud Reader example) and TAR contents layout
    • Why naïve approaches fail (path comparison, OCR)
    • Working pipeline:
      • Robust SVG rasterization with CairoSVG
      • Perceptual hashing to collapse randomized glyph IDs
      • Reference atlas generation per font variant including ligatures
      • SSIM-based visual similarity matching
      • Layout reconstruction heuristics (paragraphs, alignment, links)
      • Anti-scraping path mitigation (micro relative moves)
      • Performance/caching tips and generalization to other viewers
    • Minimal curl sketch to fetch batches
    • An end-to-end Python example wrapped in an expandable block (rasterization, hashing, atlas building, SSIM matching, decoding)
    • References (Pixelmelt blog URL and the libraries used)
• Updated index to link the new page:
  • Modified src/generic-methodologies-and-resources/basic-forensic-methodology/specific-software-file-type-tricks/README.md to include:
    • {{#ref}} svg-font-glyph-analysis-and-web-drm-deobfuscation.md {{#endref}}

No duplicate content existed; this is new, highly technical, and aligned with HackTricks’ style and structure, including proper banners, code blocks, and a References section.

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📚 Repository Maintenance

• MD files processed: 902
• MD files fixed: 1

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[carlospolop]

🔗 Additional Context

Original Blog Post: https://blog.pixelmelt.dev/kindle-web-drm/

Content Categories: Based on the analysis, this content was categorized under "Basic Forensic Methodology -> Specific Software/File-Type Tricks -> SVG/Font Glyph Analysis & Web DRM Deobfuscation (raster hashing + SSIM)".

Repository Maintenance:

• MD Files Formatting: 902 files processed (1 files fixed)

Review Notes:

• This content was automatically processed and may require human review for accuracy
• Check that the placement within the repository structure is appropriate
• Verify that all technical details are correct and up-to-date
• All .md files have been checked for proper formatting (headers, includes, etc.)

Bot Version: HackTricks News Bot v1.0