SSHdroid Phase 2 (Functional Wiring)

Android SSH client prototype with local-first persistence, SSH transport, host-key verification, key management, jump-chain model, and runtime session management.

Current Scope

• Implements Phase 2 MUST-first scope.
• Defers SFTP browser and port forwarding (visible as disabled/deferred in UI).
• Uses local device storage only (no cloud sync/telemetry).

Tech Stack

• UI: Jetpack Compose + Material 3
• Persistence: Room (hosts, chains, keys metadata, known_hosts, history)
• Preferences: DataStore
• SSH transport: SSHJ
• Key storage: app-private encrypted blobs + Android Keystore-backed app key
• Background runtime: Foreground service with persistent notification while sessions are active

Build

./gradlew :app:assembleDebug

Test

./gradlew :app:testDebugUnitTest

Functional Flows

1. Add one or more hosts in Hosts.
2. Add optional jump chain in Hosts > Jump Chains and assign it to a target host.
3. Create a key in Keys and assign it to host auth.
4. Open Connection Preview and connect.
5. Use Terminal for interactive shell input and the run-command dialog for non-interactive execution.
6. View active sessions/history in Sessions.

Test Host Setup (OpenSSH)

On a Linux/macOS host with OpenSSH server:

1. Ensure sshd is running and reachable from device/emulator.
2. Create a test account and key auth:

ssh-keygen -t ed25519 -f ~/.ssh/sshdroid_test
cat ~/.ssh/sshdroid_test.pub >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

3. Add host in app with username/hostname/port and import or generate key as needed.

Jump Chains

• Chains are ordered host hops assigned to target hosts.
• The app validates each hop and records hop-indexed failures.
• Failure details are redacted before UI/log exposure.

Biometric Key Protection

• Keys can be marked biometric-protected.
• Protected keys require biometric-approved usage path before connect/export operations.
• Unlock policy options: always prompt or cache windows (5/15/60 min metadata policy).

Host Key Verification

Per-host known_hosts policy:

• ASK (TOFU): prompt on first sight.
• STRICT: reject unknown keys.
• ACCEPT_NEW: accept first key automatically.

Changed host keys always trigger a high-friction decision prompt and default reject behavior if no decision is made.

Session History

Local-only history includes:

• host + chain summary
• start/end/duration
• outcome and failed hop (if any)

History intentionally excludes command output and keystrokes.

Diagnostics and Redaction

• Diagnostic logging is explicit and time-limited (30 minutes).
• Sensitive tokens are redacted (user@host, IP addresses, SHA256 fingerprints).

Log/Data Locations

• Room DB: app internal database (sshdroid.db)
• Key blobs: app internal files under files/ssh_keys/
• UI settings: DataStore preferences (ui_settings)

Deferred Items

• SFTP browser: deferred, disabled placeholder in UI.
• Port forwarding (-L, -D): deferred.
• Full OpenSSH config import/export and backup/restore bundle: deferred.