feat(core): Add tunnel server helper

Author: timfish

packages/core/src/index.ts

@@ -108,6 +108,7 @@ export { getMetricSummaryJsonForSpan } from './metrics/metric-summary';
 export { addTracingHeadersToFetchRequest, instrumentFetchRequest } from './fetch';
 export { trpcMiddleware } from './trpc';
 export { captureFeedback } from './feedback';
+export { handleTunnelEnvelope } from './tunnel';
 
 // eslint-disable-next-line deprecation/deprecation
 export { getCurrentHubShim, getCurrentHub } from './getCurrentHubShim';

packages/core/src/tunnel.ts

@@ -0,0 +1,76 @@
+import type { Client, Transport } from '@sentry/types';
+import { createEnvelope, dsnFromString, parseEnvelope } from '@sentry/utils';
+import { getEnvelopeEndpointWithUrlEncodedAuth } from './api';
+import { getClient } from './currentScopes';
+
+interface HandleTunnelOptions {
+  /**
+   * A list of DSNs that are allowed to be passed through the server.
+   *
+   * Defaults to only server DSN.
+   */
+  dsnAllowList?: string[];
+  /**
+   * The client instance to use
+   *
+   * Defaults to the global instance.
+   */
+  client?: Client;
+}
+
+let CACHED_TRANSPORTS: Map<string, Transport> | undefined;
+
+/**
+ * Handles envelopes sent from the browser client via the tunnel option.
+ */
+export async function handleTunnelEnvelope(
+  envelopeBytes: Uint8Array,
+  options: HandleTunnelOptions = {},
+): Promise<void> {
+  const client = (options && options.client) || getClient();
+
+  if (!client) {
+    throw new Error('No server client');
+  }
+
+  const [headers, items] = parseEnvelope(envelopeBytes);
+
+  if (!headers.dsn) {
+    throw new Error('DSN missing from envelope headers');
+  }
+
+  // If the DSN in the envelope headers matches the server DSN, we can send it directly.
+  const clientOptions = client.getOptions();
+  if (headers.dsn === clientOptions.dsn) {
+    await client.sendEnvelope(createEnvelope(headers, items));
+    return;
+  }
+
+  if (!options.dsnAllowList || !options.dsnAllowList.includes(headers.dsn)) {
+    throw new Error('DSN does not match server DSN or allow list');
+  }
+
+  if (!CACHED_TRANSPORTS) {
+    CACHED_TRANSPORTS = new Map();
+  }
+
+  let transport = CACHED_TRANSPORTS.get(headers.dsn);
+
+  if (!transport) {
+    const dsn = dsnFromString(headers.dsn);
+    if (!dsn) {
+      throw new Error('Invalid DSN in envelope headers');
+    }
+    const url = getEnvelopeEndpointWithUrlEncodedAuth(dsn);
+
+    const createTransport = clientOptions.transport;
+    transport = createTransport({
+      ...clientOptions.transportOptions,
+      recordDroppedEvent: client.recordDroppedEvent.bind(client),
+      url,
+    });
+    CACHED_TRANSPORTS.set(headers.dsn, transport);
+  }
+
+  await transport.send(createEnvelope(headers, items));
+}