> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# models
# `fastmcp.server.auth.oauth_proxy.models`
OAuth Proxy Models and Constants.
This module contains all Pydantic models and constants used by the OAuth proxy.
## Classes
### `OAuthTransaction`
OAuth transaction state for consent flow.
Stored server-side to track active authorization flows with client context.
Includes CSRF tokens for consent protection per MCP security best practices.
### `ClientCode`
Client authorization code with PKCE and upstream tokens.
Stored server-side after upstream IdP callback. Contains the upstream
tokens bound to the client's PKCE challenge for secure token exchange.
### `UpstreamTokenSet`
Stored upstream OAuth tokens from identity provider.
These tokens are obtained from the upstream provider (Google, GitHub, etc.)
and stored in plaintext within this model. Encryption is handled transparently
at the storage layer via FernetEncryptionWrapper. Tokens are never exposed to MCP clients.
### `JTIMapping`
Maps FastMCP token JTI to upstream token ID.
This allows stateless JWT validation while still being able to look up
the corresponding upstream token when tools need to access upstream APIs.
### `RefreshTokenMetadata`
Metadata for a refresh token, stored keyed by token hash.
We store only metadata (not the token itself) for security - if storage
is compromised, attackers get hashes they can't reverse into usable tokens.
### `ProxyDCRClient`
Client for DCR proxy with configurable redirect URI validation.
This special client class is critical for the OAuth proxy to work correctly
with Dynamic Client Registration (DCR). Here's why it exists:
## Problem:
When MCP clients use OAuth, they dynamically register with random localhost
ports (e.g., [http://localhost:55454/callback](http://localhost:55454/callback)). The OAuth proxy needs to:
1. Accept these dynamic redirect URIs from clients based on configured patterns
2. Use its own fixed redirect URI with the upstream provider (Google, GitHub, etc.)
3. Forward the authorization code back to the client's dynamic URI
## Solution:
This class validates redirect URIs against configurable patterns,
while the proxy internally uses its own fixed redirect URI with the upstream
provider. This allows the flow to work even when clients reconnect with
different ports or when tokens are cached.
Without proper validation, clients could get "Redirect URI not registered" errors
when trying to authenticate with cached tokens, or security vulnerabilities could
arise from accepting arbitrary redirect URIs.
**Methods:**
#### `validate_redirect_uri`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
validate_redirect_uri(self, redirect_uri: AnyUrl | None) -> AnyUrl
```
Validate redirect URI against proxy patterns and optionally CIMD redirect\_uris.
For CIMD clients: validates against BOTH the CIMD document's redirect\_uris
AND the proxy's allowed patterns (if configured). Both must pass.
For DCR clients: validates against proxy patterns first, falling back to
base validation (registered redirect\_uris) if patterns don't match.