actor

Actor Profile Endpoint

This Lambda function handles requests for ActivityPub actor profiles, supporting both human-readable HTML and machine-readable ActivityStreams JSON formats through content negotiation.

Endpoint

GET /users/{username}

Features

• Content Negotiation: Returns JSON for ActivityPub clients and HTML for browsers
• Public Key Serving: Includes public keys for HTTP signature verification
• Storage Integration: Connects to DynamoDB to fetch actor data
• Error Handling: Proper error responses with appropriate status codes

Content Types

ActivityStreams JSON

When the Accept header contains:

• application/activity+json
• application/ld+json
• application/json

Returns an ActivityPub actor object:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "id": "https://example.com/users/alice",
  "type": "Person",
  "preferredUsername": "alice",
  "name": "Alice Smith",
  "summary": "A test user",
  "inbox": "https://example.com/users/alice/inbox",
  "outbox": "https://example.com/users/alice/outbox",
  "followers": "https://example.com/users/alice/followers",
  "following": "https://example.com/users/alice/following",
  "publicKey": {
    "id": "https://example.com/users/alice#main-key",
    "owner": "https://example.com/users/alice",
    "publicKeyPem": "-----BEGIN PUBLIC KEY-----\n..."
  }
}

HTML

When the Accept header contains text/html or is missing, returns a human-readable profile page with:

• Profile information
• Avatar (if available)
• Bio/summary
• Links to followers/following
• ActivityPub discovery metadata

Environment Variables

Required:

• DOMAIN - The domain name of the instance
• TABLE_NAME - DynamoDB table name
• JWT_SECRET - Secret for JWT token generation

Optional:

• LOG_LEVEL - Logging level (debug, info, warn, error)
• AWS_REGION - AWS region for DynamoDB

Testing

Run unit tests:

JWT_SECRET=test DOMAIN=example.com TABLE_NAME=test go test -v

The tests use a mock storage implementation to avoid requiring actual DynamoDB access.

Manual Testing

Test JSON response:

curl -H "Accept: application/activity+json" https://example.com/users/alice

Test HTML response:

curl https://example.com/users/alice

Integration with WebFinger

The WebFinger endpoint (/.well-known/webfinger) returns links to this actor endpoint, enabling discovery through the standard WebFinger flow:

1. Remote server queries: /.well-known/webfinger?resource=acct:alice@example.com
2. WebFinger returns actor URL: https://example.com/users/alice
3. Remote server fetches actor profile with Accept: application/activity+json
4. Actor profile includes public key for HTTP signature verification

Error Responses

• 400 Bad Request: Missing username parameter
• 404 Not Found: Actor doesn't exist
• 500 Internal Server Error: Database or other internal errors

All error responses follow the common error format:

{
  "error": "Not Found",
  "message": "actor not found: alice",
  "code": "ACTOR_NOT_FOUND"
}

Deployment

This function is designed to be deployed as an AWS Lambda function behind API Gateway. The AWS CDK infrastructure (infra/cdk) will:

1. Create the Lambda function
2. Configure API Gateway routes
3. Set up appropriate IAM roles
4. Configure environment variables

Future Enhancements

• Support for actor attachments (profile fields)
• Custom CSS themes
• Profile metadata (pronouns, website, etc.)
• Integration with media storage for avatars
• Caching headers optimization