Validate Content-Type by parsed media type instead of substring match (v1.x) (#2444)

test/server/contentTypeValidation.test.ts

@@ -0,0 +1,115 @@
+/**
+ * Content-Type validation at the Streamable HTTP entry — the parsed media
+ * type decides, never a substring search of the raw header.
+ *
+ * The shape pinned here: `Content-Type: text/plain; a=application/json`
+ * contains the substring `application/json`, but its media type is
+ * `text/plain` — the transport must answer it (and any other non-JSON media
+ * type) with 415 before the body is dispatched, while values whose media type
+ * is `application/json` keep working regardless of parameters or case.
+ */
+import { z } from 'zod';
+import { McpServer } from '../../src/server/mcp.js';
+import { WebStandardStreamableHTTPServerTransport } from '../../src/server/webStandardStreamableHttp.js';
+import { CallToolResult } from '../../src/types.js';
+
+const executed: string[] = [];
+
+function factory(): McpServer {
+    const mcpServer = new McpServer({ name: 'ct-fixture', version: '1.0.0' });
+    mcpServer.tool('run', 'records each dispatch', { cmd: z.string() }, async ({ cmd }): Promise<CallToolResult> => {
+        executed.push(cmd);
+        return { content: [{ type: 'text', text: `ran: ${cmd}` }] };
+    });
+    return mcpServer;
+}
+
+const TOOL_CALL = {
+    jsonrpc: '2.0',
+    id: 1,
+    method: 'tools/call',
+    params: { name: 'run', arguments: { cmd: 'hello' } }
+};
+
+function postRequest(body: unknown, headers: Record<string, string>): Request {
+    return new Request('http://127.0.0.1/mcp', {
+        method: 'POST',
+        headers: {
+            Accept: 'application/json, text/event-stream',
+            ...headers
+        },
+        body: JSON.stringify(body)
+    });
+}
+
+async function sendToTransport(request: Request): Promise<Response> {
+    const server = factory();
+    const transport = new WebStandardStreamableHTTPServerTransport({
+        sessionIdGenerator: undefined,
+        enableJsonResponse: true
+    });
+    await server.connect(transport);
+    const response = await transport.handleRequest(request);
+    await server.close();
+    return response;
+}
+
+async function postToTransport(headers: Record<string, string>): Promise<Response> {
+    return sendToTransport(postRequest(TOOL_CALL, headers));
+}
+
+beforeEach(() => {
+    executed.length = 0;
+});
+
+describe('WebStandardStreamableHTTPServerTransport Content-Type validation', () => {
+    it('serves an application/json POST (control)', async () => {
+        const response = await postToTransport({ 'Content-Type': 'application/json' });
+        expect(response.status).toBe(200);
+        expect(executed).toEqual(['hello']);
+    });
+
+    it('accepts application/json with parameters', async () => {
+        const response = await postToTransport({ 'Content-Type': 'application/json; charset=utf-8' });
+        expect(response.status).toBe(200);
+        expect(executed).toEqual(['hello']);
+    });
+
+    it('rejects text/plain with 415', async () => {
+        const response = await postToTransport({ 'Content-Type': 'text/plain' });
+        expect(response.status).toBe(415);
+        expect(executed).toEqual([]);
+    });
+
+    it('rejects a non-JSON media type whose parameters contain `application/json` and does not dispatch', async () => {
+        const response = await postToTransport({ 'Content-Type': 'text/plain; a=application/json' });
+        expect(response.status).toBe(415);
+        const body = (await response.json()) as { error: { code: number; message: string } };
+        expect(body.error.code).toBe(-32000);
+        expect(body.error.message).toContain('Content-Type must be application/json');
+        expect(executed).toEqual([]);
+    });
+
+    it('rejects a POST with no Content-Type header with 415', async () => {
+        // A string body makes Request auto-attach `text/plain;charset=UTF-8`;
+        // delete it so this actually exercises the absent-header branch.
+        const request = postRequest(TOOL_CALL, {});
+        request.headers.delete('content-type');
+        expect(request.headers.get('content-type')).toBeNull();
+        const response = await sendToTransport(request);
+        expect(response.status).toBe(415);
+        expect(executed).toEqual([]);
+    });
+
+    it('accepts an unambiguous media type with a malformed parameter section (trailing semicolon)', async () => {
+        const response = await postToTransport({ 'Content-Type': 'application/json;' });
+        expect(response.status).toBe(200);
+        expect(executed).toEqual(['hello']);
+    });
+
+    it('rejects joined duplicate Content-Type headers', async () => {
+        const response = await postToTransport({ 'Content-Type': 'application/json, application/json' });
+        expect(response.status).toBe(415);
+        expect(executed).toEqual([]);
+    });
+});

test/shared/mediaType.test.ts

@@ -0,0 +1,66 @@
+import { isJsonContentType, mediaTypeEssence } from '../../src/shared/mediaType.js';
+
+describe('mediaTypeEssence', () => {
+    it('parses well-formed headers', () => {
+        expect(mediaTypeEssence('application/json')).toBe('application/json');
+        expect(mediaTypeEssence('text/event-stream; charset=utf-8')).toBe('text/event-stream');
+        expect(mediaTypeEssence('Application/JSON; charset=utf-8')).toBe('application/json');
+    });
+
+    it('falls back to the pre-parameter segment for malformed parameter sections', () => {
+        expect(mediaTypeEssence('application/json;')).toBe('application/json');
+        expect(mediaTypeEssence('application/json; charset=')).toBe('application/json');
+        expect(mediaTypeEssence('text/plain;')).toBe('text/plain');
+    });
+
+    it('returns undefined for missing or empty headers', () => {
+        expect(mediaTypeEssence(null)).toBeUndefined();
+        expect(mediaTypeEssence(undefined)).toBeUndefined();
+        expect(mediaTypeEssence('')).toBeUndefined();
+        expect(mediaTypeEssence('   ')).toBeUndefined();
+        expect(mediaTypeEssence(';charset=utf-8')).toBeUndefined();
+    });
+
+    it('yields no essence for joined duplicate headers, with or without parameters', () => {
+        // Headers.get() joins repeated headers with ', '. Without parameters
+        // the comma lands in the first segment; with parameters it hides in
+        // the tail — both must behave the same.
+        expect(mediaTypeEssence('application/json, application/json')).toBe('application/json, application/json');
+        expect(mediaTypeEssence('application/json; charset=utf-8, text/plain')).toBeUndefined();
+        expect(mediaTypeEssence('application/json; charset=utf-8, application/json')).toBeUndefined();
+    });
+});
+
+describe('isJsonContentType', () => {
+    it('accepts application/json with or without parameters', () => {
+        expect(isJsonContentType('application/json')).toBe(true);
+        expect(isJsonContentType('application/json; charset=utf-8')).toBe(true);
+        expect(isJsonContentType('Application/JSON')).toBe(true);
+        expect(isJsonContentType('  application/json ; charset=utf-8')).toBe(true);
+    });
+
+    it('accepts unambiguous media types with malformed parameter sections', () => {
+        expect(isJsonContentType('application/json;')).toBe(true);
+        expect(isJsonContentType('application/json; charset=')).toBe(true);
+        expect(isJsonContentType('application/json; charset=utf-8; charset=x')).toBe(true);
+    });
+
+    it('never matches on substrings: parameters and sibling types are not application/json', () => {
+        expect(isJsonContentType('text/plain; a=application/json')).toBe(false);
+        expect(isJsonContentType('text/plain;')).toBe(false);
+        expect(isJsonContentType('text/plain, application/json')).toBe(false);
+        expect(isJsonContentType('application/json, application/json')).toBe(false);
+        expect(isJsonContentType('application/json; charset=utf-8, text/plain')).toBe(false);
+        expect(isJsonContentType('text/plain; charset=utf-8, application/json')).toBe(false);
+        expect(isJsonContentType('application/json-patch+json')).toBe(false);
+        expect(isJsonContentType('application/jsonp')).toBe(false);
+    });
+
+    it('rejects missing, empty, and non-JSON types', () => {
+        expect(isJsonContentType(null)).toBe(false);
+        expect(isJsonContentType(undefined)).toBe(false);
+        expect(isJsonContentType('')).toBe(false);
+        expect(isJsonContentType('text/plain')).toBe(false);
+        expect(isJsonContentType('multipart/form-data')).toBe(false);
+    });
+});