# Thunderbird Email Security & OpenPGP Architecture

Subsystem: Snigdha Privacy Suite
Application: Mozilla Thunderbird 159.0
Distribution: Snigdha OS Decentralized

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# 1. Overview & Operational Role

Thunderbird serves as the desktop email communication client, integrated with built-in OpenPGP (RNP) encryption, remote content defenses, and NetGuard network torification.

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# 2. Hardened Default Preferences

Thunderbird is configured via /usr/lib/thunderbird/defaults/pref/snigdha-privacy.js:

• Remote Content Blocking: mailnews.message_display.disable_remote_image = true (blocks tracking pixels and web beacons).
• Inline Attachments Disabled: mail.inline_attachments = false (prevents auto-rendering of potentially malicious attachments).
• Telemetry Frozen: datareporting.healthreport.uploadEnabled = false and toolkit.telemetry.enabled = false.
• Automatic Updates Blocked: app.update.enabled = false (preserves immutable live system integrity; updates occur via signed releases).

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# 3. Cryptographic Separation: Thunderbird vs GnuPG

Thunderbird does not use GnuPG directly; it implements its own internal OpenPGP engine using the RNP cryptographic library.

# Boundary Invariants:

1. Independent Key Stores:
   • Thunderbird keys reside in ~/.thunderbird/<profile>/openpgp.sqlite.
   • GnuPG keys reside in ~/.gnupg/.
2. Key Import/Export: Moving keys between Thunderbird and GnuPG requires explicit user export/import (Tools -> OpenPGP Key Manager).
3. AppArmor Confinement: Thunderbird's AppArmor profile explicitly denies access to ~/.gnupg/private-keys-v1.d/**. A compromised email parser cannot access system GnuPG private keys.

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# 4. Email Metadata Realities (What OpenPGP Does NOT Hide)

OpenPGP encrypts email message bodies and attachments. It does NOT encrypt or conceal:

• Sender Email Address (From:)
• Recipient Email Address (To:)
• Carbon Copy (Cc:)
• Date and Time of Transmission (Date:)
• Subject Header (Subject:) in standard configurations
• Originating and Intermediate Mail Server IP Headers
• Message Size and Timing Correlation

Critical Principle: Routing email through Tor hides your IP from your mail provider, but your mail provider and the recipient's mail provider still record account identities and communicative relationships.

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# 5. Profile Volatility & Optional Persistence

• Default Volatility: ~/.thunderbird/ resides in RAM tmpfs. All accounts, downloaded messages, and drafts vanish on reboot.
• Optional thunderbird-profile Persistence Feature:
  • Disabled by default.
  • Requires unlocking Snigdha Persistence with LUKS2 passphrase.
  • Bind-mounts ~/.thunderbird/ to /run/snigdha/persistence/features/thunderbird-profile/ (Mode 0700).
  • Explicit warning: Enabling persistence preserves communication history and private keys on disk.