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Security

Reporting Vulnerabilities

If you discover a security vulnerability, please report it privately via GitHub's security advisory feature or by contacting the maintainers directly. Do not open a public issue.

Threat Model

The extension handles sensitive cryptographic key material. The security design assumes:

  • The user's device is not compromised
  • The browser itself is trusted
  • Web pages are untrusted and may be hostile

Key Storage

Private keys are encrypted at rest using AES-256-GCM:

  • Password-derived key via PBKDF2 with SHA-256, 210,000 iterations, and a random 32-byte salt
  • Random 12-byte IV per encryption
  • Stored in browser.storage.local as base64-encoded salt + IV + ciphertext

Keys are only decrypted in memory when the vault is explicitly unlocked.

Auto-Lock

The vault auto-locks after a configurable period of inactivity (default: 15 minutes). On lock, all decrypted key material and the derived crypto key are set to null. On Chrome, service worker termination also clears memory.

Private Key Zeroing

Every code path that accesses raw private key bytes follows a strict pattern:

const privkey = vault.getPrivkey();
try {
    // use privkey
} finally {
    privkey.fill(0);
}

The Uint8Array is zeroed immediately after use, minimizing the window of exposure.

Message Isolation

Three execution contexts with strict boundaries:

Context World Access
inject.js MAIN (page) Can only postMessage to content script
content.js ISOLATED Validates method names against allowlists before forwarding
background.js Service worker Handles all business logic, gated by sender verification

Web pages cannot directly call background methods. All requests pass through the content script's method allowlist.

Privileged Method Gating

Sensitive operations (vault, permissions, account management, sync, database operations) are restricted to internal extension pages:

const isInternal = sender.id === browser.runtime.id && !sender.tab;

The !sender.tab check ensures the message originates from an extension page (popup, onboarding, prompt) and not from a content script running in a web page tab.

Rate Limiting

Two layers of rate limiting protect against abuse:

Layer Location Limit
Content script content.js 1,000 req/sec (all methods)
Background background.js 10 req/sec per method (sliding window)

vault_unlock is included in the background rate limiter to prevent brute-force password guessing.

Per-Account Isolation

Each account gets its own IndexedDB instance (nostr-wot-{accountId}), preventing cross-account data leakage in the social graph.

NIP-07 Signing Permissions

Signing requests trigger a user-facing prompt window. Users can:

  • Allow or deny individual requests
  • Grant persistent permissions per domain, per method, or per event kind
  • Revoke permissions at any time from the popup

Permission lookup follows a specificity cascade: kind-specific > method-level > domain wildcard > default (ask).

Dependencies

The extension has zero external runtime dependencies. All cryptographic primitives (secp256k1, Schnorr, NIP-04, NIP-44, BIP-32, BIP-39) are implemented in pure JavaScript using the Web Crypto API where available.