# Secret - Hierarchical Secret Manager

Secret is a modern, secure command-line secret manager that implements a hierarchical key architecture for storing and managing sensitive data. It supports multiple vaults, various unlock mechanisms, and provides secure storage using the Age encryption library.

## Core Architecture

### Three-Layer Key Hierarchy

Secret implements a sophisticated three-layer key architecture:

1. **Long-term Keys**: Derived from BIP39 mnemonic phrases, these provide the foundation for all encryption
2. **Unlockers**: Short-term keys that encrypt the long-term keys, supporting multiple authentication methods
3. **Version-specific Keys**: Per-version keys that encrypt individual secret values

### Version Management

Each secret maintains a history of versions, with each version having:
- Its own encryption key pair
- Encrypted metadata including creation time and validity period
- Immutable value storage
- Atomic version switching via symlink updates

### Vault System

Vaults provide logical separation of secrets, each with its own long-term key and unlocker set. This allows for complete isolation between different contexts (work, personal, projects).

## Installation

Build from source:
```bash
git clone <repository>
cd secret
make build
```

## Quick Start

1. **Initialize the secret manager**:
   ```bash
   secret init
   ```
   This creates the default vault and prompts for a BIP39 mnemonic phrase.

2. **Generate a mnemonic** (if needed):
   ```bash
   secret generate mnemonic
   ```

3. **Add a secret**:
   ```bash
   echo "my-password" | secret add myservice/password
   ```

4. **Retrieve a secret**:
   ```bash
   secret get myservice/password
   ```

## Commands Reference

### Initialization

#### `secret init`
Initializes the secret manager with a default vault. Prompts for a BIP39 mnemonic phrase and creates the initial directory structure.

**Environment Variables:**
- `SB_SECRET_MNEMONIC`: Pre-set mnemonic phrase
- `SB_UNLOCK_PASSPHRASE`: Pre-set unlock passphrase

### Vault Management

#### `secret vault list [--json]`
Lists all available vaults.

#### `secret vault create <name>`
Creates a new vault with the specified name.

#### `secret vault select <name>`
Switches to the specified vault for subsequent operations.

### Secret Management

#### `secret add <secret-name> [--force]`
Adds a secret to the current vault. Reads the secret value from stdin.
- `--force, -f`: Overwrite existing secret

**Secret Name Format:** `[a-z0-9\.\-\_\/]+`
- Forward slashes (`/`) are converted to percent signs (`%`) for storage
- Examples: `database/password`, `api.key`, `ssh_private_key`

#### `secret get <secret-name> [--version <version>]`
Retrieves and outputs a secret value to stdout.
- `--version, -v`: Get a specific version (default: current)

#### `secret list [filter] [--json]` / `secret ls`
Lists all secrets in the current vault. Optional filter for substring matching.

### Version Management

#### `secret version list <secret-name>`
Lists all versions of a secret showing creation time, status, and validity period.

#### `secret version promote <secret-name> <version>`
Promotes a specific version to current by updating the symlink. Does not modify any timestamps, allowing for rollback scenarios.

### Key Generation

#### `secret generate mnemonic`
Generates a cryptographically secure BIP39 mnemonic phrase.

#### `secret generate secret <name> [--length=16] [--type=base58] [--force]`
Generates and stores a random secret.
- `--length, -l`: Length of generated secret (default: 16)
- `--type, -t`: Type of secret (`base58`, `alnum`)
- `--force, -f`: Overwrite existing secret

### Unlocker Management

#### `secret unlockers list [--json]`
Lists all unlockers in the current vault with their metadata.

#### `secret unlockers add <type> [options]`
Creates a new unlocker of the specified type:

**Types:**
- `passphrase`: Traditional passphrase-protected unlocker
- `pgp`: Uses an existing GPG key for encryption/decryption

**Options:**
- `--keyid <id>`: GPG key ID (required for PGP type)

#### `secret unlockers rm <unlocker-id>`
Removes an unlocker.

#### `secret unlocker select <unlocker-id>`
Selects an unlocker as the current default for operations.

### Import Operations

#### `secret import <secret-name> --source <filename>`
Imports a secret from a file and stores it in the current vault under the given name.

#### `secret vault import [vault-name]`
Imports a mnemonic phrase into the specified vault (defaults to "default").

### Encryption Operations

#### `secret encrypt <secret-name> [--input=file] [--output=file]`
Encrypts data using an Age key stored as a secret. If the secret doesn't exist, generates a new Age key.

#### `secret decrypt <secret-name> [--input=file] [--output=file]`
Decrypts data using an Age key stored as a secret.

## Storage Architecture

### Directory Structure

```
~/.local/share/secret/
├── vaults.d/
│   ├── default/
│   │   ├── unlockers.d/
│   │   │   ├── passphrase/              # Passphrase unlocker
│   │   │   └── pgp/                     # PGP unlocker
│   │   ├── secrets.d/
│   │   │   ├── api%key/                 # Secret: api/key
│   │   │   │   ├── versions/
│   │   │   │   │   ├── 20231215.001/   # Version directory
│   │   │   │   │   │   ├── pub.age     # Version public key
│   │   │   │   │   │   ├── priv.age    # Version private key (encrypted)
│   │   │   │   │   │   ├── value.age   # Encrypted value
│   │   │   │   │   │   └── metadata.age # Encrypted metadata
│   │   │   │   │   └── 20231216.001/   # Another version
│   │   │   │   └── current -> versions/20231216.001
│   │   │   └── database%password/       # Secret: database/password
│   │   │       ├── versions/
│   │   │       └── current -> versions/20231215.001
│   │   ├── vault-metadata.json          # Vault metadata
│   │   ├── pub.age                      # Long-term public key
│   │   └── current-unlocker -> ../unlockers.d/passphrase
│   └── work/
│       ├── unlockers.d/
│       ├── secrets.d/
│       ├── vault-metadata.json
│       ├── pub.age
│       └── current-unlocker
└── currentvault -> vaults.d/default
```

### Key Management and Encryption Flow

#### Long-term Keys
- **Source**: Derived from BIP39 mnemonic phrases using hierarchical deterministic (HD) key derivation
- **Purpose**: Master keys for each vault, used to encrypt secret-specific keys
- **Storage**: Public key stored as `pub.age`, private key encrypted by unlockers

#### Unlockers
Unlockers provide different authentication methods to access the long-term keys:

1. **Passphrase Unlockers**:
   - Encrypted with user-provided passphrase
   - Stored as encrypted Age keys
   - Cross-platform compatible

2. **PGP Unlockers**:
   - Uses existing GPG key infrastructure
   - Leverages existing key management workflows
   - Strong authentication through GPG

Each vault maintains its own set of unlockers and one long-term key. The long-term key is encrypted to each unlocker, allowing any authorized unlocker to access vault secrets.

#### Secret-specific Keys
- Each secret has its own encryption key pair
- Private key encrypted to the vault's long-term key
- Provides forward secrecy and granular access control

### Environment Variables

- `SB_SECRET_STATE_DIR`: Custom state directory location
- `SB_SECRET_MNEMONIC`: Pre-set mnemonic phrase (avoids interactive prompt)
- `SB_UNLOCK_PASSPHRASE`: Pre-set unlock passphrase (avoids interactive prompt)
- `SB_GPG_KEY_ID`: GPG key ID for PGP unlockers

## Security Features

### Encryption
- Uses the [Age encryption library](https://age-encryption.org/) with X25519 keys
- All private keys are encrypted at rest
- No plaintext secrets stored on disk

### Access Control
- Multiple authentication methods supported
- Hierarchical key architecture provides defense in depth
- Vault isolation prevents cross-contamination

### Forward Secrecy
- Per-version encryption keys limit exposure if compromised
- Each version is independently encrypted
- Long-term keys protected by multiple unlocker layers
- Historical versions remain encrypted with their original keys

### Hardware Integration
- Hardware token support via PGP/GPG integration

## Examples

### Basic Workflow
```bash
# Initialize with a new mnemonic
secret generate mnemonic  # Copy the output
secret init              # Paste the mnemonic when prompted

# Add some secrets
echo "supersecret123" | secret add database/prod/password
echo "api-key-xyz" | secret add services/api/key
echo "ssh-private-key-content" | secret add ssh/servers/web01

# List and retrieve secrets
secret list
secret get database/prod/password
secret get services/api/key
```

### Multi-vault Setup
```bash
# Create separate vaults for different contexts
secret vault create work
secret vault create personal

# Work with work vault
secret vault select work
echo "work-db-pass" | secret add database/password
secret unlockers add passphrase  # Add passphrase authentication

# Switch to personal vault
secret vault select personal
echo "personal-email-pass" | secret add email/password

# List all vaults
secret vault list
```

### Advanced Authentication
```bash
# Add multiple unlock methods
secret unlockers add passphrase              # Password-based
secret unlockers add pgp --keyid ABCD1234    # GPG key

# List unlockers
secret unlockers list

# Select a specific unlocker
secret unlocker select <unlocker-id>
```

### Encryption/Decryption with Age Keys
```bash
# Generate an Age key and store it as a secret
secret generate secret encryption/mykey

# Encrypt a file using the stored key
secret encrypt encryption/mykey --input document.txt --output document.txt.age

# Decrypt the file
secret decrypt encryption/mykey --input document.txt.age --output document.txt
```

## Technical Details

### Cryptographic Primitives
- **Key Derivation**: BIP32/BIP39 hierarchical deterministic key derivation
- **Encryption**: Age (X25519 + ChaCha20-Poly1305)
- **Key Exchange**: X25519 elliptic curve Diffie-Hellman
- **Authentication**: Poly1305 MAC
- **Hashing**: Double SHA-256 for public key identification

### File Formats
- **Age Files**: Standard Age encryption format (.age extension)
- **Metadata**: JSON format with timestamps and type information
- **Vault Metadata**: JSON containing vault name, creation time, derivation index, and public key hash

### Vault Management
- **Derivation Index**: Each vault uses a unique derivation index from the mnemonic
- **Public Key Hash**: Double SHA-256 hash of the index-0 public key identifies vaults from the same mnemonic
- **Automatic Key Derivation**: When creating vaults with a mnemonic, keys are automatically derived

### Cross-Platform Support
- **macOS**: Full support including Keychain integration
- **Linux**: Full support (excluding Keychain features)
- **Windows**: Basic support (filesystem operations only)

## Security Considerations

### Threat Model
- Protects against unauthorized access to secret values
- Provides defense against compromise of individual components
- Supports hardware-backed authentication where available

### Best Practices
1. Use strong, unique passphrases for unlockers
2. Enable hardware authentication (Keychain, hardware tokens) when available
3. Regularly audit unlockers and remove unused ones
4. Keep mnemonic phrases securely backed up offline
5. Use separate vaults for different security contexts

### Limitations
- Requires access to unlockers for secret retrieval
- Mnemonic phrases must be securely stored and backed up
- Hardware features limited to supported platforms

## Development

### Building
```bash
make build    # Build binary
make test     # Run tests
make lint     # Run linter
```

### Testing
The project includes comprehensive tests:
```bash
make test     # Run all tests
go test ./... # Unit tests
go test -tags=integration -v ./internal/cli  # Integration tests
```

## Features

- **Multiple Authentication Methods**: Supports passphrase-based and PGP-based unlockers
- **Vault Isolation**: Complete separation between different vaults
- **Per-Secret Encryption**: Each secret has its own encryption key
- **BIP39 Mnemonic Support**: Keyless operation using mnemonic phrases
- **Cross-Platform**: Works on macOS, Linux, and other Unix-like systems

