I'll help you design your FedRAMP 20x Authorization Data Sharing API.

# Authorization Data Sharing API Design Guide (FRR-ADS)

## Overview

**PRODUCTION-FIRST ASSUMPTION:** All API designs, security controls, and configurations assume **PRODUCTION deployment** with full FedRAMP 20x compliance requirements unless explicitly stated otherwise. Non-production APIs should still implement security controls appropriate for their data classification.

FedRAMP 20x requires CSPs to share authorization data via API rather than document uploads. This API must provide machine-readable access to your security posture.

**Important: Format Requirements**
- **Required:** Machine-readable formats (JSON, XML, or other structured data)
- **Optional:** OSCAL is a NIST standard that can be used as one implementation approach
- FRR-ADS requirements specify "machine-readable" only - OSCAL is NOT mentioned in FedRAMP 20x
- Choose custom JSON/XML or OSCAL based on your implementation needs

## Required Endpoints

### 1. System Information
```
GET /api/v1/system
GET /api/v1/authorization-boundary
GET /api/v1/system-characteristics
```

**Response Format Example (Using OSCAL - One Option):**
```json
{
  "system-security-plan": {
    "uuid": "12345678-1234-1234-1234-123456789abc",
    "metadata": {
      "title": "My Cloud Service SSP",
      "last-modified": "2025-11-26T10:00:00Z",
      "version": "1.2.0",
      "oscal-version": "1.1.2"
    },
    "system-characteristics": {
      "system-ids": [...],
      "system-name": "My Cloud Service",
      "description": "...",
      "security-sensitivity-level": "moderate",
      "authorization-boundary": {
        "description": "...",
        "diagrams": [...],
        "remarks": "..."
      }
    },
    "system-implementation": {
      "users": [...],
      "components": [...],
      "leveraged-authorizations": [...]
    }
  }
}
```

### 2. Vulnerability Data
```
GET /api/v1/vulnerabilities
GET /api/v1/vulnerabilities?status=open
GET /api/v1/vulnerabilities?severity=high
GET /api/v1/vulnerabilities/{vuln-id}
```

**Response Format:**
```json
{
  "vulnerabilities": [
    {
      "id": "vuln-2025-001",
      "cve_id": "CVE-2025-12345",
      "severity": "HIGH",
      "cvss_score": 8.5,
      "discovered_date": "2025-11-20",
      "status": "remediation_in_progress",
      "remediation_deadline": "2025-11-27",
      "affected_components": ["web-server-prod-01"],
      "description": "...",
      "remediation_plan": "..."
    }
  ],
  "metadata": {
    "total_count": 45,
    "open_count": 12,
    "last_scan": "2025-11-26T08:00:00Z"
  }
}
```

### 3. Key Security Indicators
```
GET /api/v1/ksi
GET /api/v1/ksi/{category}
GET /api/v1/ksi/{ksi-id}
GET /api/v1/ksi/metrics?start_date=2025-10-01&end_date=2025-12-31
```

**Response Format:**
```json
{
  "ksi_metrics": [
    {
      "id": "KSI-IAM-01",
      "name": "Phishing-Resistant MFA",
      "status": "compliant",
      "metric_value": "100%",
      "measurement_date": "2025-11-26",
      "details": {
        "total_users": 150,
        "users_with_mfa": 150,
        "mfa_type": "FIDO2"
      },
      "evidence": {
        "type": "automated_report",
        "location": "https://evidencestorage.blob.core.windows.net/reports/iam-mfa-report-2025-11.pdf"
      }
    }
  ]
}
```

### 4. Incidents
```
GET /api/v1/incidents
GET /api/v1/incidents?start_date=2025-10-01
GET /api/v1/incidents/{incident-id}
```

**Response Format:**
```json
{
  "incidents": [
    {
      "id": "INC-2025-003",
      "type": "security_event",
      "severity": "medium",
      "detected_date": "2025-11-15T14:30:00Z",
      "resolved_date": "2025-11-15T18:45:00Z",
      "affected_agencies": [],
      "description": "Suspicious login attempts detected",
      "response_actions": "Account locked, investigation completed",
      "status": "closed"
    }
  ]
}
```

### 5. Changes
```
GET /api/v1/changes
GET /api/v1/changes?type=significant
GET /api/v1/changes/{change-id}
```

**Response Format:**
```json
{
  "changes": [
    {
      "id": "CHG-2025-042",
      "type": "transformative",
      "date": "2025-11-20",
      "description": "Added new microservice for analytics",
      "impact_assessment": "New component added to boundary",
      "notification_sent": true,
      "notification_date": "2025-11-20",
      "approvals": [...]
    }
  ]
}
```

### 6. POA&M
```
GET /api/v1/poam
GET /api/v1/poam?status=open
GET /api/v1/poam/{poam-id}
```

**Response Format (OSCAL POA&M):**
```json
{
  "plan-of-action-and-milestones": {
    "uuid": "...",
    "metadata": {...},
    "poam-items": [
      {
        "uuid": "...",
        "title": "Implement automated log forwarding",
        "description": "...",
        "risk-statement": "...",
        "remediation-tracking": {
          "tracking-entry": [
            {
              "date-time-stamp": "2025-11-26T10:00:00Z",
              "title": "Initial identification",
              "description": "..."
            }
          ]
        }
      }
    ]
  }
}
```

## Authentication & Authorization

### Option 1: OAuth 2.0 (Recommended for Multiple Consumers)

**Flow:**
```
1. Agency registers as OAuth client with FedRAMP
2. FedRAMP provides client_id and client_secret
3. Agency requests token:
   POST /oauth/token
   {
     "grant_type": "client_credentials",
     "client_id": "agency-xyz",
     "client_secret": "..."
   }
4. Use token in requests:
   GET /api/v1/system
   Authorization: Bearer {token}
```

**Implementation:**
```python
# Using FastAPI + OAuth2
from fastapi import FastAPI, Depends, HTTPException
from fastapi.security import OAuth2PasswordBearer

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

@app.get("/api/v1/system")
async def get_system(token: str = Depends(oauth2_scheme)):
    # Validate token
    client = validate_token(token)
    if not client:
        raise HTTPException(status_code=401)
    
    # Return system data
    return get_system_data()
```

### Option 2: Mutual TLS (mTLS) (Recommended for High Security)

**Configuration:**
```
1. FedRAMP/Agency provides client certificate
2. Configure API to require client certificates
3. Validate certificate on each request
```

**Nginx Configuration:**
```nginx
server {
    listen 443 ssl;
    server_name api.myservice.com;
    
    ssl_certificate /etc/nginx/ssl/server.crt;
    ssl_certificate_key /etc/nginx/ssl/server.key;
    
    # Require client certificate
    ssl_client_certificate /etc/nginx/ssl/ca.crt;
    ssl_verify_client on;
    
    location /api/ {
        proxy_pass http://backend;
        proxy_set_header X-SSL-Client-Cert $ssl_client_cert;
    }
}
```

## Access Control

**Principle: Least Privilege**

Different consumers should have different access levels:

```json
{
  "client_id": "fedramp-pmo",
  "permissions": [
    "read:system",
    "read:vulnerabilities", 
    "read:ksi",
    "read:incidents",
    "read:changes",
    "read:poam"
  ]
},
{
  "client_id": "agency-xyz",
  "permissions": [
    "read:system",
    "read:vulnerabilities",
    "read:incidents:agency-xyz",  // Only their incidents
    "read:ksi"
  ]
}
```

## API Versioning

**Use URL versioning:**
```
/api/v1/system  (current)
/api/v2/system  (future)
```

**Include version in responses:**
```json
{
  "api_version": "1.0.0",
  "data": {...}
}
```

## Rate Limiting

**Recommended limits:**
```
- Per client: 1000 requests/hour
- Per endpoint: 100 requests/minute
- Burst: Allow 10 requests/second
```

**Headers:**
```
X-RateLimit-Limit: 1000
X-RateLimit-Remaining: 850
X-RateLimit-Reset: 1701014400
```

## Error Handling

**Standard error format:**
```json
{
  "error": {
    "code": "unauthorized",
    "message": "Invalid or expired token",
    "details": "Token expired at 2025-11-26T10:00:00Z",
    "timestamp": "2025-11-26T12:30:00Z",
    "request_id": "req-abc-123"
  }
}
```

## Monitoring & Logging

**Log all API access:**
```json
{
  "timestamp": "2025-11-26T10:00:00Z",
  "client_id": "fedramp-pmo",
  "endpoint": "/api/v1/vulnerabilities",
  "method": "GET",
  "status_code": 200,
  "response_time_ms": 145,
  "user_agent": "FedRAMP-Client/1.0"
}
```

**Alert on:**
- Repeated authentication failures
- Unusual access patterns
- High error rates
- Slow response times

## Testing

**Provide test credentials:**
```
Test API endpoint: https://api-test.myservice.com
Client ID: test-client
Client Secret: (provided securely)
```

**Sample queries:**
```bash
# Test authentication
curl -X POST https://api-test.myservice.com/oauth/token \
  -d "grant_type=client_credentials&client_id=test-client&client_secret=..."

# Test system endpoint
curl https://api-test.myservice.com/api/v1/system \
  -H "Authorization: Bearer {token}"

# Test vulnerabilities
curl https://api-test.myservice.com/api/v1/vulnerabilities?status=open \
  -H "Authorization: Bearer {token}"
```

## Documentation

**Provide OpenAPI/Swagger spec:**
```yaml
openapi: 3.0.0
info:
  title: Authorization Data Sharing API
  version: 1.0.0
  description: FedRAMP 20x compliant API for sharing authorization data

servers:
  - url: https://api.myservice.com
    description: Production API

paths:
  /api/v1/system:
    get:
      summary: Get system information
      security:
        - oauth2: [read:system]
      responses:
        '200':
          description: System information in OSCAL format
```

## Implementation Checklist

- [ ] Choose authentication method (OAuth 2.0 or mTLS)
- [ ] Implement all required endpoints
- [ ] Use machine-readable formats (JSON/XML) - custom or OSCAL based on your needs
- [ ] Add proper error handling
- [ ] Implement rate limiting
- [ ] Add comprehensive logging
- [ ] Write API documentation (OpenAPI)
- [ ] Create test credentials
- [ ] Test with FedRAMP/agency
- [ ] Monitor API usage and performance

Use get_implementation_examples('FRR-ADS-01') for more detailed implementation guidance.