| 1 | package plugin |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "context" |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "io" |
| 9 | "maps" |
| 10 | "net/http" |
| 11 | "net/url" |
| 12 | "strings" |
| 13 | "time" |
| 14 | |
| 15 | mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp" |
| 16 | ) |
| 17 | |
| 18 | const mcpSubscriptionsListenMethod = "subscriptions/listen" |
| 19 | |
| 20 | // asyncStreamableHTTPSubscriptions keeps the optional SEP-2575 notification |
| 21 | // stream from becoming part of the mandatory startup critical path. Some MCP |
| 22 | // HTTP bridges buffer a streaming Web Response before writing HTTP response |
| 23 | // headers, so the SDK's synchronous transport write would otherwise block |
| 24 | // Client.Connect even though server/discover already completed successfully. |
| 25 | // |
| 26 | // The underlying call still uses the SDK-owned connection and context. A |
| 27 | // compliant server therefore keeps delivering notifications normally, while a |
| 28 | // buffering server is cancelled with the session without blocking tools/list. |
| 29 | func asyncStreamableHTTPSubscriptions(next mcpsdk.MethodHandler) mcpsdk.MethodHandler { |
| 30 | return func(ctx context.Context, method string, req mcpsdk.Request) (mcpsdk.Result, error) { |
| 31 | if method != mcpSubscriptionsListenMethod { |
| 32 | return next(ctx, method, req) |
| 33 | } |
| 34 | if err := ctx.Err(); err != nil { |
| 35 | return nil, err |
| 36 | } |
| 37 | go func() { |
| 38 | _, _ = next(ctx, method, req) |
| 39 | }() |
| 40 | return &mcpsdk.SubscriptionsListenResult{}, nil |
| 41 | } |
| 42 | } |
| 43 | |
| 44 | func newHTTPTransport(s Spec) (*sdkSessionTransport, error) { |
| 45 | if strings.TrimSpace(s.Type) == "" { |
| 46 | s.Type = "http" |
| 47 | } |
| 48 | // Transient OAuth/probe connections declare no optional capabilities. |
| 49 | return newSDKSessionTransport(context.Background(), s, HostProfileCore) |
| 50 | } |
| 51 | |
| 52 | func validateMCPURL(name, transport, raw string) error { |
| 53 | if strings.TrimSpace(raw) == "" { |
| 54 | return fmt.Errorf("%s plugin %q: url is required", transport, name) |
| 55 | } |
| 56 | u, err := url.Parse(raw) |
| 57 | if err != nil || u == nil || u.Scheme == "" || u.Host == "" { |
| 58 | return fmt.Errorf("%s plugin %q: invalid url", transport, name) |
| 59 | } |
| 60 | switch strings.ToLower(u.Scheme) { |
| 61 | case "http", "https": |
| 62 | return nil |
| 63 | default: |
| 64 | return fmt.Errorf("%s plugin %q: url must use http or https", transport, name) |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | func newMCPHTTPClient(lifetime context.Context, s Spec) (*http.Client, error) { |
| 69 | origin, err := url.Parse(strings.TrimSpace(s.URL)) |
| 70 | if err != nil || origin == nil || origin.Host == "" { |
| 71 | return nil, fmt.Errorf("invalid MCP endpoint") |
| 72 | } |
| 73 | headers := make(map[string]string, len(s.Headers)) |
| 74 | maps.Copy(headers, s.Headers) |
| 75 | base := http.DefaultTransport.(*http.Transport).Clone() |
| 76 | client := &http.Client{ |
| 77 | Transport: &sameOriginMCPRoundTripper{ |
| 78 | origin: origin, |
| 79 | headers: headers, |
| 80 | base: base, |
| 81 | lifetime: lifetime, |
| 82 | }, |
| 83 | } |
| 84 | client.CheckRedirect = func(req *http.Request, _ []*http.Request) error { |
| 85 | if sameHTTPOrigin(origin, req.URL) { |
| 86 | return nil |
| 87 | } |
| 88 | return http.ErrUseLastResponse |
| 89 | } |
| 90 | return client, nil |
| 91 | } |
| 92 | |
| 93 | type sameOriginMCPRoundTripper struct { |
| 94 | origin *url.URL |
| 95 | headers map[string]string |
| 96 | base http.RoundTripper |
| 97 | lifetime context.Context |
| 98 | } |
| 99 | |
| 100 | func (rt *sameOriginMCPRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) { |
| 101 | if req == nil || !sameHTTPOrigin(rt.origin, req.URL) { |
| 102 | return nil, errors.New("MCP request changed origin; configured headers were not sent") |
| 103 | } |
| 104 | requestCtx := req.Context() |
| 105 | cancelRequest := func() {} |
| 106 | stopLifetime := func() bool { return true } |
| 107 | // Keep protocol cleanup independent from the session lifetime: Close first |
| 108 | // cancels active GET/POST requests, then the SDK sends this bounded DELETE. |
| 109 | if req.Method != http.MethodDelete { |
| 110 | var cancel context.CancelFunc |
| 111 | requestCtx, cancel = context.WithCancel(req.Context()) |
| 112 | cancelRequest = cancel |
| 113 | if rt.lifetime != nil { |
| 114 | stopLifetime = context.AfterFunc(rt.lifetime, cancelRequest) |
| 115 | } |
| 116 | } |
| 117 | cancelLifetimeRequest := func() { |
| 118 | stopLifetime() |
| 119 | cancelRequest() |
| 120 | } |
| 121 | request := req.Clone(requestCtx) |
| 122 | request.Header = req.Header.Clone() |
| 123 | for key, value := range rt.headers { |
| 124 | request.Header.Set(key, value) |
| 125 | } |
| 126 | |
| 127 | base := rt.base |
| 128 | if base == nil { |
| 129 | base = http.DefaultTransport |
| 130 | } |
| 131 | if request.Method != http.MethodDelete { |
| 132 | response, err := base.RoundTrip(request) |
| 133 | return responseWithCancel(response, err, cancelLifetimeRequest) |
| 134 | } |
| 135 | |
| 136 | deleteCtx, cancelDelete := context.WithTimeout(request.Context(), 2*time.Second) |
| 137 | request = request.Clone(deleteCtx) |
| 138 | response, err := base.RoundTrip(request) |
| 139 | return responseWithCancel(response, err, func() { |
| 140 | cancelDelete() |
| 141 | cancelLifetimeRequest() |
| 142 | }) |
| 143 | } |
| 144 | |
| 145 | func responseWithCancel(response *http.Response, err error, cancel func()) (*http.Response, error) { |
| 146 | if err != nil { |
| 147 | cancel() |
| 148 | return nil, err |
| 149 | } |
| 150 | if response.Body == nil { |
| 151 | cancel() |
| 152 | return response, nil |
| 153 | } |
| 154 | response.Body = &cancelOnCloseBody{ReadCloser: response.Body, cancel: cancel} |
| 155 | return response, nil |
| 156 | } |
| 157 | |
| 158 | func (rt *sameOriginMCPRoundTripper) CloseIdleConnections() { |
| 159 | if closer, ok := rt.base.(interface{ CloseIdleConnections() }); ok { |
| 160 | closer.CloseIdleConnections() |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | type cancelOnCloseBody struct { |
| 165 | io.ReadCloser |
| 166 | cancel func() |
| 167 | } |
| 168 | |
| 169 | func (b *cancelOnCloseBody) Close() error { |
| 170 | err := b.ReadCloser.Close() |
| 171 | b.cancel() |
| 172 | return err |
| 173 | } |
| 174 | |
| 175 | func sameHTTPOrigin(a, b *url.URL) bool { |
| 176 | if a == nil || b == nil || !strings.EqualFold(a.Scheme, b.Scheme) || !strings.EqualFold(a.Hostname(), b.Hostname()) { |
| 177 | return false |
| 178 | } |
| 179 | effectivePort := func(u *url.URL) string { |
| 180 | if port := u.Port(); port != "" { |
| 181 | return port |
| 182 | } |
| 183 | switch strings.ToLower(u.Scheme) { |
| 184 | case "http": |
| 185 | return "80" |
| 186 | case "https": |
| 187 | return "443" |
| 188 | default: |
| 189 | return "" |
| 190 | } |
| 191 | } |
| 192 | return effectivePort(a) == effectivePort(b) |
| 193 | } |
| 194 | |
| 195 | func (t *sdkSessionTransport) newEndpoint(ctx context.Context) (sdkEndpoint, error) { |
| 196 | if t.endpointFactory != nil { |
| 197 | return t.endpointFactory(ctx) |
| 198 | } |
| 199 | switch canonicalMCPRuntimeTransport(t.spec.Type) { |
| 200 | case "stdio": |
| 201 | process, err := newStdioTransport(ctx, t.spec) |
| 202 | if err != nil { |
| 203 | return sdkEndpoint{}, err |
| 204 | } |
| 205 | return sdkEndpoint{ |
| 206 | transport: &mcpsdk.IOTransport{Reader: process.stdout, Writer: process.stdin}, |
| 207 | close: process.close, |
| 208 | startupStderr: process.startupStderr, |
| 209 | }, nil |
| 210 | case "streamable-http": |
| 211 | client, err := newMCPHTTPClient(ctx, t.spec) |
| 212 | if err != nil { |
| 213 | return sdkEndpoint{}, err |
| 214 | } |
| 215 | return sdkEndpoint{ |
| 216 | transport: &mcpsdk.StreamableClientTransport{ |
| 217 | Endpoint: t.spec.URL, |
| 218 | HTTPClient: client, |
| 219 | MaxRetries: 5, |
| 220 | OAuthHandler: t.oauth, |
| 221 | }, |
| 222 | close: client.CloseIdleConnections, |
| 223 | }, nil |
| 224 | case "sse": |
| 225 | client, err := newMCPHTTPClient(ctx, t.spec) |
| 226 | if err != nil { |
| 227 | return sdkEndpoint{}, err |
| 228 | } |
| 229 | return sdkEndpoint{ |
| 230 | transport: &mcpsdk.SSEClientTransport{Endpoint: t.spec.URL, HTTPClient: client}, |
| 231 | close: client.CloseIdleConnections, |
| 232 | }, nil |
| 233 | default: |
| 234 | return sdkEndpoint{}, fmt.Errorf("unknown MCP transport %q", t.spec.Type) |
| 235 | } |
| 236 | } |
| 237 | |
| 238 | // do is retained as a narrow HTTP security test hook. MCP protocol traffic goes |
| 239 | // through the SDK transport above. |
| 240 | func (t *sdkSessionTransport) do(ctx context.Context, body []byte) (*http.Response, error) { |
| 241 | client, err := newMCPHTTPClient(ctx, t.spec) |
| 242 | if err != nil { |
| 243 | return nil, err |
| 244 | } |
| 245 | req, err := http.NewRequestWithContext(ctx, http.MethodPost, t.spec.URL, bytes.NewReader(body)) |
| 246 | if err != nil { |
| 247 | return nil, err |
| 248 | } |
| 249 | req.Header.Set("Content-Type", "application/json") |
| 250 | req.Header.Set("Accept", "application/json, text/event-stream") |
| 251 | return client.Do(req) |
| 252 | } |
| 253 |