Security Review

Security review for ShareGo

Review checklist

When reviewing any code change in ShareGo, check:

Crypto

• Only libsodium is used for crypto — no platform APIs, no custom implementations
• Ephemeral keys generated fresh per session (generateKeyPair())
• Keys are never persisted to disk, local storage, or databases
• zeroMemory() called on all key material when session ends
• Fresh random nonce per DATA message (24 bytes via randombytes_buf)
• AEAD used for all encryption (xchacha20poly1305_ietf)

Protocol

• Protocol version checked on every deserialized message
• Sequence numbers validated (no duplicate or out-of-order)
• Session ID validated on every incoming message
• Unknown message types are rejected, not ignored
• No sensitive data in QR payload or pairing codes

Session

• 2-user limit enforced (second connection rejected)
• Receiver approval required before session becomes active
• Bootstrap expiry checked before accepting connections
• Session TTL enforced
• cleanup() called on every exit path (close, reject, error, disconnect)

Transport

• No internet fallback or cloud relay
• No data sent before handshake completes
• Transport errors trigger session cleanup
• Only Uint8Array crosses the transport boundary (no strings)

General

• No console.log of secrets, keys, or sensitive data
• Constant-time comparison for any secret comparison
• Error messages do not leak secret material
• Changes documented in THREAT_MODEL.md if they affect the security surface

Config & i18n

• Timing values (TTLs, timeouts) come from core/src/config.ts, not hardcoded
• User-facing text comes from core/src/i18n/en.ts, not hardcoded in app shells
• No sensitive data appears in translation strings or config constants

Platform parity

• Changes applied to both desktop and mobile (if applicable)
• Platform adapters don't contain any crypto or protocol logic
• Both platforms use the same SessionController from core

How to run a review

1. Read the diff carefully — focus on core/ changes first
2. Walk through each checklist item above
3. For crypto changes: verify against docs/THREAT_MODEL.md crypto table
4. For protocol changes: verify against docs/PROTOCOL.md message specs
5. For transport changes: verify the ILocalTransport interface contract
6. Flag any item that fails with a clear explanation of the risk

Reference

• Full threat model: docs/THREAT_MODEL.md
• Crypto primitives: core/src/crypto/crypto.ts
• Protocol spec: docs/PROTOCOL.md
• Rejected alternatives: docs/REJECTED.md
• Config constants: core/src/config.ts
• Translation strings: core/src/i18n/en.ts
• Session controller: core/src/session/session-controller.ts

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