Authentication Patterns

---
name: authentication-patterns
description: Provides auth patterns for API keys, OAuth, and token management. Use when implementing or reviewing service authentication and credential handling.
alwaysApply: false
category: infrastructure
tags:
- authentication
- api-keys
- oauth
- tokens
- security
dependencies:
- error-patterns
provides:
  infrastructure:
  - authentication
  - credential-management
  - auth-verification
  patterns:
  - api-key-auth
  - oauth-flow
  - token-refresh
usage_patterns:
- service-authentication
- credential-verification
- token-management
complexity: beginner
model_hint: fast
estimated_tokens: 400
progressive_loading: true
modules:
- modules/auth-methods.md
- modules/verification-patterns.md
- modules/interactive-auth.md
---

# Authentication Patterns

## Overview

Common authentication patterns for integrating with external services. Provides consistent approaches to credential management, verification, and error handling.

## When To Use

- Integrating with external APIs
- Need credential verification
- Managing multiple auth methods
- Handling auth failures gracefully

## When NOT To Use

- Project doesn't use the leyline infrastructure patterns
- Simple scripts without service architecture needs

## Authentication Methods

| Method | Best For | Environment Variable |
|--------|----------|---------------------|
| API Key | Simple integrations | `{SERVICE}_API_KEY` |
| OAuth | User-authenticated | Browser-based flow |
| Token | Session-based | `{SERVICE}_TOKEN` |
| None | Public APIs | N/A |

## Quick Start

### Verify Authentication
```python
from leyline.auth import verify_auth, AuthMethod

# API Key verification
status = verify_auth(
    service="gemini", method=AuthMethod.API_KEY, env_var="GEMINI_API_KEY"
)

if not status.authenticated:
    print(f"Auth failed: {status.message}")
    print(f"Action: {status.suggested_action}")
```
**Verification:** Run the command with `--help` flag to verify availability.

### Smoke Test
```python
def verify_with_smoke_test(service: str) -> bool:
    """Verify auth with simple request."""
    result = execute_simple_request(service, "ping")
    return result.success
```
**Verification:** Run `pytest -v` to verify tests pass.

## Standard Flow

### Step 1: Check Environment
```python
def check_credentials(service: str, env_var: str) -> bool:
    value = os.getenv(env_var)
    if not value:
        print(f"Missing {env_var}")
        return False
    return True
```
**Verification:** Run the command with `--help` flag to verify availability.

### Step 2: Verify with Service
```python
def verify_with_service(service: str) -> AuthStatus:
    result = subprocess.run([service, "auth", "status"], capture_output=True)
    return AuthStatus(
        authenticated=(result.returncode == 0), message=result.stdout.decode()
    )
```
**Verification:** Run the command with `--help` flag to verify availability.

### Step 3: Handle Failures
```python
def handle_auth_failure(service: str, method: AuthMethod) -> str:
    actions = {
        AuthMethod.API_KEY: f"Set {service.upper()}_API_KEY environment variable",
        AuthMethod.OAUTH: f"Run '{service} auth login' for browser auth",
        AuthMethod.TOKEN: f"Refresh token with '{service} token refresh'",
    }
    return actions[method]
```
**Verification:** Run the command with `--help` flag to verify availability.

## Integration Pattern

```yaml
# In your skill's frontmatter
dependencies: [leyline:authentication-patterns]
```
**Verification:** Run the command with `--help` flag to verify availability.

## Interactive Authentication (Shell)

For workflows requiring interactive authentication with token caching and session management:

```bash
# Source the interactive auth script
source plugins/leyline/scripts/interactive_auth.sh

# Ensure authentication before proceeding
ensure_auth github || exit 1
ensure_auth gitlab || exit 1
ensure_auth aws || exit 1

# Continue with authenticated operations
gh pr view 123
glab issue list
aws s3 ls
```

**Features:**
- ✅ Interactive OAuth flows for GitHub, GitLab, AWS, and more
- ✅ Token caching (5-minute TTL)
- ✅ Session persistence (24-hour TTL)
- ✅ CI/CD compatible (auto-detects non-interactive environments)
- ✅ Multi-service support

See `modules/interactive-auth.md` for complete documentation.

## Detailed Resources

- **Auth Methods**: See `modules/auth-methods.md` for method details
- **Verification**: See `modules/verification-patterns.md` for testing patterns
- **Interactive**: See `modules/interactive-auth.md` for shell-based auth flows

## Exit Criteria

- Credentials verified or clear failure message
- Suggested action for auth failures
- Smoke test confirms working auth