# iOS Agent — API Compatibility Reference

**Status**: API CONTRACT
**Mirror**: Android Agent (`apps/android-agent/`)

## Overview

The iOS agent communicates with the server via two HTTP endpoints:

1. **Provisioning**: `POST /api/v1/provision` — Initial key exchange
2. **Heartbeat**: `POST /api/v1/heartbeat` — Periodic status + config sync

## 1. Provisioning

### Request

```
POST /api/v1/provision
Content-Type: application/json
```

```json
{
  "token": "string (required)",
  "hwid": "string (required)"
}
```

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `token` | string | Yes | Registration token (single-use) |
| `hwid` | string | Yes | Hardware ID (iOS identifierForVendor) |

### Response (Success)

```
HTTP/1.1 200 OK
Content-Type: application/json
```

```json
{
  "encrypted_config": "base64-encoded-bytes"
}
```

| Field | Type | Description |
|-------|------|-------------|
| `encrypted_config` | string | AES-256-GCM encrypted ConfigPayload |

### Response (Error)

```json
{
  "error": "string"
}
```

| Status | Error | Description |
|--------|-------|-------------|
| 400 | `"invalid token format"` | Token is not valid UUID |
| 400 | `"token already used"` | Token was already consumed |
| 400 | `"invalid hardware id"` | HWID is empty or invalid |
| 403 | `"token expired"` | Token has expired (24h TTL) |
| 500 | `"provisioning failed"` | Server internal error |

### Decrypted ConfigPayload

After decrypting `encrypted_config`, the agent receives:

```json
{
  "device_id": "string (UUID)",
  "private_key": "string (hex, 64 chars)",
  "preshared_key": "string (hex, 64 chars)",
  "internal_ip": "string (e.g. 10.172.21.2)",
  "server_pub": "string (hex, 64 chars)",
  "endpoint": "string (e.g. italy-twenty.gl.at.ply.gg:59750)",
  "dns": "string (e.g. 1.1.1.1)",
  "allowed_ips": "string (e.g. 0.0.0.0/0)",
  "server_wg_ip": "string (e.g. 10.172.21.1)"
}
```

| Field | Type | Description |
|-------|------|-------------|
| `device_id` | string | Device UUID (use in heartbeat) |
| `private_key` | string | WireGuard private key (hex) |
| `preshared_key` | string | Pre-shared key (hex) |
| `internal_ip` | string | Device IP address |
| `server_pub` | string | Server WireGuard public key (hex) |
| `endpoint` | string | Server WireGuard endpoint |
| `dns` | string | DNS server IP |
| `allowed_ips` | string | Allowed IPs (e.g. "0.0.0.0/0" for full tunnel) |
| `server_wg_ip` | string | Server WireGuard IP |

## 2. Heartbeat

### Request

```
POST /api/v1/heartbeat
Content-Type: application/json
```

```json
{
  "device_id": "string (required)",
  "status": "string (optional)",
  "state": "string (optional)",
  "tunnel_up": "boolean (optional)",
  "last_handshake": "string (optional, ISO 8601)"
}
```

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `device_id` | string | Yes | Device UUID |
| `status` | string | No | "connected", "recovering", "stopped" |
| `state` | string | No | Free-form state description |
| `tunnel_up` | boolean | No | WireGuard tunnel status |
| `last_handshake` | string | No | ISO 8601 timestamp of last handshake |

### Response (Success)

```
HTTP/1.1 200 OK
Content-Type: application/json
```

```json
{
  "device_id": "string",
  "status": "ok",
  "internal_ip": "string",
  "private_key": "string (hex)",
  "preshared_key": "string (hex)",
  "server_pub": "string (hex)",
  "endpoint": "string",
  "server_wg_ip": "string",
  "dns": "string",
  "allowed_ips": "string",
  "forwards_hash": "string"
}
```

| Field | Type | Description |
|-------|------|-------------|
| `device_id` | string | Device UUID |
| `status` | string | "ok" or error |
| `internal_ip` | string | Device IP (may change) |
| `private_key` | string | WireGuard private key (may rotate) |
| `preshared_key` | string | Pre-shared key (may rotate) |
| `server_pub` | string | Server public key |
| `endpoint` | string | Server endpoint |
| `server_wg_ip` | string | Server WireGuard IP |
| `dns` | string | DNS server |
| `allowed_ips` | string | Allowed IPs |
| `forwards_hash` | string | Hash of port forwards (for change detection) |

### Response (Error)

```json
{
  "error": "string"
}
```

| Status | Error | Description |
|--------|-------|-------------|
| 400 | `"invalid device id"` | Device ID is not valid UUID |
| 403 | `"device is suspended"` | Device is suspended by admin |
| 500 | `"heartbeat failed"` | Server internal error |

## 3. Crypto Protocol

### Key Derivation

```
key = SHA256(hwid + salt)
```

- `hwid`: Hardware ID (iOS `identifierForVendor`)
- `salt`: Server's `SERVER_SALT` environment variable
- Output: 32-byte AES key

### Encryption (Server Side)

```
plaintext = ConfigPayload JSON
nonce = random 12 bytes
ciphertext = AES-256-GCM-Encrypt(key, nonce, plaintext)
encrypted_config = nonce + ciphertext
```

### Decryption (Agent Side)

```swift
let combined = Data(base64Encoded: encryptedConfig)!
let nonce = combined.prefix(12)
let ciphertext = combined.dropFirst(12)

let sealedBox = try AES.GCM.SealedBox(nonce: nonce, ciphertext: ciphertext)
let plaintext = try AES.GCM.open(sealedBox, using: key)
let json = try JSONSerialization.jsonObject(with: plaintext)
```

### Implementation Notes

- Use `CryptoKit` for AES-256-GCM
- Use `CryptoKit` for SHA-256 key derivation
- Nonce size: 12 bytes (fixed for GCM)
- Tag size: 16 bytes (default for GCM)

## 4. Config Change Detection

### Heartbeat Hash Comparison

The server returns `forwards_hash` in heartbeat response. Agent should:

1. Store last received `forwards_hash` in UserDefaults
2. Compare with current hash
3. If different, trigger config reload

```swift
let lastHash = UserDefaults.standard.string(forKey: "config_hash") ?? ""

if lastHash != response.forwardsHash {
    // Config changed, rebuild tunnel
    tunnelManager.rebuildTunnel(with: newConfig)
    UserDefaults.standard.set(response.forwardsHash, forKey: "config_hash")
}
```

## 5. Hardware ID

### iOS identifierForVendor

```swift
import UIKit

let hwid = UIDevice.current.identifierForVendor?.uuidString ?? "unknown"
```

### Alternative: Custom Serial

```swift
func getHardwareId() -> String {
    // Use Keychain to persist custom HWID
    if let savedHwid = KeychainManager.get(key: "hwid") {
        return savedHwid
    }
    
    let newHwid = UUID().uuidString
    KeychainManager.set(key: "hwid", value: newHwid)
    return newHwid
}
```

## 6. Versioning

### Current Version

- API Version: v1 (implicit, no version in URL)
- Agent Version: 1.0.0

### Compatibility Policy

- **Breaking Changes**: Major version bump (v2)
- **New Fields**: Added without version bump (agent ignores unknown fields)
- **Deprecation**: 6-month notice before removal

### Agent Behavior

- Agent ignores unknown fields in server response
- Agent sends only required fields in request
- Agent handles missing optional fields gracefully

## 7. Examples

### Provisioning Flow

```swift
// 1. Get hardware ID
let hwid = UIDevice.current.identifierForVendor?.uuidString ?? "unknown"

// 2. Send provisioning request
let body = ["token": token, "hwid": hwid]
let request = URLRequest(url: URL(string: "\(serverUrl)/api/v1/provision")!)

// 3. Parse encrypted config
let encrypted = try JSONDecoder().decode([String: String].self, from: data)["encrypted_config"]!

// 4. Decrypt config
let config = try CryptoManager.decryptConfig(encrypted: encrypted, hwid: hwid, salt: salt)

// 5. Store in Keychain
KeychainStorage.save(config)

// 6. Apply to WireGuard
try await tunnelManager.startTunnel(config: config)
```

### Heartbeat Flow

```swift
// 1. Get tunnel status
let tunnelUp = tunnelManager.isTunnelUp()
let lastHandshake = tunnelManager.getLastHandshake()

// 2. Send heartbeat
let body: [String: Any] = [
    "device_id": config.deviceId,
    "tunnel_up": tunnelUp,
    "last_handshake": lastHandshake?.iso8601String ?? "1970-01-01T00:00:00Z"
]

// 3. Check for config changes
let response = try JSONDecoder().decode(HeartbeatResponse.self, from: data)

if config.configHash != response.forwardsHash {
    // Config changed, reload
    let newConfig = try parseConfig(from: response)
    tunnelManager.rebuildTunnel(with: newConfig)
    KeychainStorage.save(newConfig)
}
```

## 8. Error Handling

### HTTP Retries

```swift
func sendRequest(url: URL, body: Data, maxRetries: Int = 3) async throws -> Data {
    for attempt in 1...maxRetries {
        do {
            let (data, response) = try await URLSession.shared.data(for: request)
            if let httpResponse = response as? HTTPURLResponse,
               httpResponse.statusCode == 200 {
                return data
            }
        } catch {
            if attempt == maxRetries {
                throw error
            }
            try await Task.sleep(nanoseconds: UInt64(attempt * 1_000_000_000))
        }
    }
    throw AgentError.heartbeatFailed("Max retries exceeded")
}
```

### Timeout Settings

- Connect timeout: 10 seconds
- Read timeout: 30 seconds
- Write timeout: 10 seconds

## 9. Security Notes

- All communication over HTTPS (TLS 1.2+)
- Registration token is single-use (consumed on first provisioning)
- Device can re-provision by obtaining new token
- Keys never logged or transmitted in plaintext
- WireGuard keys stored in iOS Keychain (hardware-backed)