70 lines
2.4 KiB
Go
70 lines
2.4 KiB
Go
// Copyright 2026 The Go MCP SDK Authors. All rights reserved.
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// Use of this source code is governed by an MIT-style
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// license that can be found in the LICENSE file.
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// This file contains shared utilities for OAuth handlers.
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package auth
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import (
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"context"
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"net/http"
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"net/url"
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"strings"
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"github.com/modelcontextprotocol/go-sdk/oauthex"
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)
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// GetAuthServerMetadata fetches authorization server metadata for the given issuer URL.
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// It tries standard well-known endpoints (OAuth 2.0 and OIDC) and returns the first successful result.
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//
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// Returns (nil, nil) when no metadata endpoints respond (404s), allowing callers to implement
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// fallback logic. Returns an error for any non-client error (network failures, invalid JSON, etc.).
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func GetAuthServerMetadata(ctx context.Context, issuerURL string, httpClient *http.Client) (*oauthex.AuthServerMeta, error) {
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for _, metadataURL := range authorizationServerMetadataURLs(issuerURL) {
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asm, err := oauthex.GetAuthServerMeta(ctx, metadataURL, issuerURL, httpClient)
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if err != nil {
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return nil, err
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}
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if asm != nil {
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return asm, nil
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}
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}
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return nil, nil
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}
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// authorizationServerMetadataURLs returns a list of URLs to try when looking for
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// authorization server metadata as mandated by the MCP specification:
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// https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization#authorization-server-metadata-discovery.
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func authorizationServerMetadataURLs(issuerURL string) []string {
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var urls []string
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baseURL, err := url.Parse(issuerURL)
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if err != nil {
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return nil
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}
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if baseURL.Path == "" {
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// "OAuth 2.0 Authorization Server Metadata".
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baseURL.Path = "/.well-known/oauth-authorization-server"
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urls = append(urls, baseURL.String())
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// "OpenID Connect Discovery 1.0".
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baseURL.Path = "/.well-known/openid-configuration"
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urls = append(urls, baseURL.String())
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return urls
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}
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originalPath := baseURL.Path
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// "OAuth 2.0 Authorization Server Metadata with path insertion".
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baseURL.Path = "/.well-known/oauth-authorization-server/" + strings.TrimLeft(originalPath, "/")
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urls = append(urls, baseURL.String())
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// "OpenID Connect Discovery 1.0 with path insertion".
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baseURL.Path = "/.well-known/openid-configuration/" + strings.TrimLeft(originalPath, "/")
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urls = append(urls, baseURL.String())
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// "OpenID Connect Discovery 1.0 with path appending".
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baseURL.Path = "/" + strings.Trim(originalPath, "/") + "/.well-known/openid-configuration"
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urls = append(urls, baseURL.String())
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return urls
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}
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