🛡️ Sentinel: [CRITICAL] Fix internal error leakage via JSON-RPC responses

src/mcp/mcp-server-apps.test.ts

@@ -12,14 +12,6 @@ let apiBaseUrl: string;
 const tempDirs: string[] = [];
 const originalAllowPrivateNetwork = process.env.MCP4_SSRF_ALLOW_PRIVATE_NETWORK;
 
-async function writeTempFile(name: string, content: string): Promise<string> {
-  const dir = await fs.mkdtemp(path.join(os.tmpdir(), 'mcp-server-apps-'));
-  tempDirs.push(dir);
-  const filePath = path.join(dir, name);
-  await fs.writeFile(filePath, content, 'utf8');
-  return filePath;
-}
-
 beforeAll(async () => {
   process.env.MCP4_SSRF_ALLOW_PRIVATE_NETWORK = 'true';
   apiServer = createServer((req, res) => {
@@ -275,14 +267,14 @@ describe('MCPServer apps resources', () => {
       },
     });
 
-    expect(invalidReadResponse.error).toEqual({
+    expect(invalidReadResponse.error).toMatchObject({
       code: -32602,
-      message: 'resources/read requires string parameter "uri"',
     });
-    expect(invalidCompletionResponse.error).toEqual({
+    expect(invalidReadResponse.error.message).toMatch(/^Validation error: resources\/read requires string parameter "uri" \(correlation ID: .+\)$/);
+    expect(invalidCompletionResponse.error).toMatchObject({
       code: -32602,
-      message: 'completion/complete requires a resource ref',
     });
+    expect(invalidCompletionResponse.error.message).toMatch(/^Validation error: completion\/complete requires a resource ref \(correlation ID: .+\)$/);
   });
 
   it('propagates session context to fetch-backed resource and completion lookups', async () => {

src/mcp/mcp-server.ts

@@ -798,8 +798,8 @@ export class MCPServer {
         // Generate correlation ID only on error (lazy)
         const correlationId = generateCorrelationId();
         this.logger.error('ListTools handler error', err as Error, { correlationId });
-        // Always return generic error to clients
-        throw new Error(`Internal error (correlation ID: ${correlationId})`);
+        // Return formatted error
+        throw new Error(this.formatErrorForClient(err, correlationId));
       }
     });
 
@@ -811,7 +811,7 @@ export class MCPServer {
       } catch (err) {
         const correlationId = generateCorrelationId();
         this.logger.error('ListPrompts handler error', err as Error, { correlationId });
-        throw new Error(`Internal error (correlation ID: ${correlationId})`);
+        throw new Error(this.formatErrorForClient(err, correlationId));
       }
     });
 
@@ -832,7 +832,7 @@ export class MCPServer {
           correlationId,
           promptName: request.params.name,
         });
-        throw new Error(`Internal error (correlation ID: ${correlationId})`);
+        throw new Error(this.formatErrorForClient(err, correlationId));
       }
     });
 
@@ -1851,6 +1851,8 @@ export class MCPServer {
           result: promptResult,
         };
       } catch (error) {
+        const correlationId = generateCorrelationId();
+        this.logger.error('prompts/get handler error', error as Error, { correlationId });
         let code = -32603;
         if (error instanceof ValidationError) {
           code = -32602;
@@ -1863,7 +1865,7 @@ export class MCPServer {
           id: req.id,
           error: {
             code,
-            message: (error as Error).message,
+            message: this.formatErrorForClient(error, correlationId),
           },
         };
       }
@@ -1901,12 +1903,14 @@ export class MCPServer {
           result: await this.readResource(params.uri, sessionId, profileId),
         };
       } catch (error) {
+        const correlationId = generateCorrelationId();
+        this.logger.error('resources/read handler error', error as Error, { correlationId });
         return {
           jsonrpc: '2.0',
           id: req.id,
           error: {
             code: error instanceof ValidationError ? -32602 : -32601,
-            message: (error as Error).message,
+            message: this.formatErrorForClient(error, correlationId),
           },
         };
       }
@@ -1920,12 +1924,14 @@ export class MCPServer {
           result: await this.completeResourceArgument(req as CompleteRequest, sessionId, profileId),
         };
       } catch (error) {
+        const correlationId = generateCorrelationId();
+        this.logger.error('completion/complete handler error', error as Error, { correlationId });
         return {
           jsonrpc: '2.0',
           id: req.id,
           error: {
             code: error instanceof ValidationError ? -32602 : -32601,
-            message: (error as Error).message,
+            message: this.formatErrorForClient(error, correlationId),
           },
         };
       }