OAuth 2.0

An authorization grant is a credential representing the resource owner's authorization for the client to access their protected resources. OAuth 2.0 defines several grant types for different use cases:

• Authorization Code: For server-side web apps. The most secure and common flow.
• Client Credentials: For machine-to-machine (M2M) communication where a specific user context is not required.
• Resource Owner Password Credentials: For highly trusted applications (e.g., a service's own mobile app). Deprecated for third-party use.
• Implicit Grant: Previously for browser-based apps. Now superseded by the Authorization Code flow with PKCE.

An access token is a string issued by the authorization server to the client application. It represents delegated authorization and is presented to the resource server (e.g., a vector database API) to access protected resources.

Scopes define the granularity of permissions. A token is issued for specific scopes (e.g., vectors:read, collections:write), limiting what the client can do. The token is typically a JWT (JSON Web Token) containing metadata like the client ID, user ID, issued-at time, and expiration.

The OAuth 2.0 framework is defined by four distinct roles:

• Resource Owner: The entity (often an end-user) who owns the data and can grant access to it.
• Client: The application (e.g., a data pipeline tool) requesting access to the resource owner's data.
• Authorization Server: The server that authenticates the resource owner and issues access tokens to the client after obtaining consent. It hosts the /authorize and /token endpoints.
• Resource Server: The server hosting the protected resources (e.g., the vector database API). It accepts and validates access tokens to serve requests.

This is the recommended flow for most applications, including single-page apps (SPAs) and native mobile apps. It involves a front-channel redirect and a secure back-channel exchange:

1. Authorization Request: Client redirects the user to the authorization server with client_id, redirect_uri, scope, and a code_challenge (PKCE).
2. User Consent: User authenticates and grants the requested permissions.
3. Authorization Code: Server redirects back to the client with a short-lived code.
4. Token Exchange: Client sends the code and code_verifier to the server's /token endpoint (back-channel) to receive an access token and often a refresh token. PKCE (Proof Key for Code Exchange) prevents authorization code interception attacks.

Used for service-to-service authentication where no end-user is involved. This is common for backend services, daemons, or microservices accessing a vector database API on their own behalf.

Process:

1. The client application authenticates directly with the authorization server using its client_id and client_secret.
2. It requests an access token for a predefined scope.
3. The authorization server validates the credentials and issues an access token. The issued token represents the application itself, not a user. This flow is ideal for automated data ingestion pipelines or internal admin tools interacting with a vector database.

A refresh token is a long-lived credential used to obtain new access tokens without requiring the user to re-authenticate. It is issued alongside the access token in the Authorization Code flow.

Token Management Best Practices:

• Short-Lived Access Tokens: Minimize risk if compromised (e.g., 1-hour expiry).
• Secure Storage: Clients must securely store client_secret and refresh tokens (never in browser code).
• Token Revocation: Authorization servers provide a /revoke endpoint to invalidate tokens if a client is compromised.
• Token Introspection: Resource servers can call the authorization server's /introspect endpoint to validate an access token's active state and scopes.

A simple, static credential (a long alphanumeric string) used to authenticate and authorize an application to a vector database's API. Unlike OAuth 2.0's dynamic tokens, an API key typically provides blanket access and does not expire, making it less granular but simpler for server-to-server communication where user context is not required.

• Static Authentication: The key is passed in an HTTP header (e.g., Authorization: Bearer <API_KEY>).
• Use Case: Ideal for internal services, scripts, or administrative access where the client is trusted and user delegation is not needed.
• Security Consideration: Keys must be kept secret, as compromise grants full associated permissions. Rotation is a manual process.

A core OAuth 2.0 concept representing a specific permission or access right. Scopes limit what an access token can do. During authorization, the client requests a set of scopes; the resource owner (user) approves them, and the resulting access token is only valid for those operations.

• Granular Authorization: Examples for a vector database API could include vectors:read, collections:write, or admin:all.
• Token Validation: The resource server (e.g., the vector database) must check that the token's scopes permit the requested API operation.
• Best Practice: Request the least privileged scopes necessary for the application's function.

A strong authentication protocol where both the client and the server authenticate each other using X.509 digital certificates before establishing a TLS-encrypted connection. It provides a higher assurance level than bearer tokens alone and is often used in conjunction with OAuth 2.0 for client authentication or securing machine-to-machine communication.

• Certificate-Based: The client presents a certificate signed by a trusted Certificate Authority (CA) to prove its identity.
• Use with OAuth 2.0: The OAuth 2.0 Client Credentials flow can use mTLS for client authentication, making stolen client secrets useless without the corresponding private key.
• Vector Database Context: Can secure the connection between a client SDK and the database's API gateway, ensuring the client is a known, trusted service.

A long-lived credential used by a client to obtain a new access token after the previous one expires, without requiring the resource owner to re-authenticate. Refresh tokens are issued alongside access tokens in certain OAuth 2.0 grants (like Authorization Code) and are stored securely by the client.

• Lifetime Management: Enables access tokens to be short-lived (enhancing security) while maintaining user session continuity.
• Security Critical: Refresh tokens are highly sensitive; if compromised, an attacker can obtain new access tokens. They must be stored securely and can be revoked by the authorization server.
• Flow: The client calls the token endpoint with the grant_type=refresh_token to exchange a valid refresh token for a new access token.