Make HTTP requests with the proper User-Agent

CHANGES.md

@@ -8,6 +8,10 @@ Version 1.3.0
 
 To be released.
 
+ -  Fedify now makes HTTP requests with the proper `User-Agent` header.
+
+     -  Added `getUserAgent()` function.
+
 
 Version 1.2.2
 -------------

src/nodeinfo/client.ts

@@ -1,5 +1,6 @@
 import { getLogger } from "@logtape/logtape";
 import { parse, type SemVer } from "@std/semver";
+import { getUserAgent } from "../runtime/docloader.ts";
 import type { ResourceDescriptor } from "../webfinger/jrd.ts";
 import type {
   InboundService,
@@ -83,7 +84,12 @@ export async function getNodeInfo(
     let nodeInfoUrl: URL | string = url;
     if (!options.direct) {
       const wellKnownUrl = new URL("/.well-known/nodeinfo", url);
-      const wellKnownResponse = await fetch(wellKnownUrl);
+      const wellKnownResponse = await fetch(wellKnownUrl, {
+        headers: {
+          Accept: "application/json",
+          "User-Agent": getUserAgent(),
+        },
+      });
       if (!wellKnownResponse.ok) {
         logger.error("Failed to fetch {url}: {status} {statusText}", {
           url: wellKnownUrl.href,
@@ -110,7 +116,12 @@ export async function getNodeInfo(
       }
       nodeInfoUrl = link.href;
     }
-    const response = await fetch(nodeInfoUrl);
+    const response = await fetch(nodeInfoUrl, {
+      headers: {
+        Accept: "application/json",
+        "User-Agent": getUserAgent(),
+      },
+    });
     if (!response.ok) {
       logger.error(
         "Failed to fetch NodeInfo document from {url}: {status} {statusText}",

src/runtime/docloader.test.ts

@@ -1,5 +1,7 @@
 import { assertEquals, assertRejects, assertThrows } from "@std/assert";
 import * as mf from "mock_fetch";
+import process from "node:process";
+import metadata from "../deno.json" with { type: "json" };
 import { MemoryKvStore } from "../federation/kv.ts";
 import { verifyRequest } from "../sig/http.ts";
 import { mockDocumentLoader } from "../testing/docloader.ts";
@@ -10,6 +12,7 @@ import {
   fetchDocumentLoader,
   FetchError,
   getAuthenticatedDocumentLoader,
+  getUserAgent,
   kvCache,
 } from "./docloader.ts";
 import { UrlError } from "./url.ts";
@@ -480,3 +483,62 @@ test("kvCache()", async (t) => {
     );
   });
 });
+
+test("getUserAgent()", () => {
+  if ("Deno" in globalThis) {
+    assertEquals(
+      getUserAgent(),
+      `Fedify/${metadata.version} (Deno/${Deno.version.deno})`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0"),
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Deno/${Deno.version.deno})`,
+    );
+    assertEquals(
+      getUserAgent(null, "https://example.com/"),
+      `Fedify/${metadata.version} (Deno/${Deno.version.deno}; +https://example.com/)`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0", new URL("https://example.com/")),
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Deno/${Deno.version.deno}; +https://example.com/)`,
+    );
+  } else if ("Bun" in globalThis) {
+    assertEquals(
+      getUserAgent(),
+      // @ts-ignore: `Bun` is a global variable in Bun
+      `Fedify/${metadata.version} (Bun/${Bun.version})`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0"),
+      // @ts-ignore: `Bun` is a global variable in Bun
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Bun/${Bun.version})`,
+    );
+    assertEquals(
+      getUserAgent(null, "https://example.com/"),
+      // @ts-ignore: `Bun` is a global variable in Bun
+      `Fedify/${metadata.version} (Bun/${Bun.version}; +https://example.com/)`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0", new URL("https://example.com/")),
+      // @ts-ignore: `Bun` is a global variable in Bun
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Bun/${Bun.version}; +https://example.com/)`,
+    );
+  } else {
+    assertEquals(
+      getUserAgent(),
+      `Fedify/${metadata.version} (Node.js/${process.version})`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0"),
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Node.js/${process.version})`,
+    );
+    assertEquals(
+      getUserAgent(null, "https://example.com/"),
+      `Fedify/${metadata.version} (Node.js/${process.version}; +https://example.com/)`,
+    );
+    assertEquals(
+      getUserAgent("MyApp/1.0.0", new URL("https://example.com/")),
+      `MyApp/1.0.0 (Fedify/${metadata.version}; Node.js/${process.version}; +https://example.com/)`,
+    );
+  }
+});

src/runtime/docloader.ts

@@ -1,5 +1,6 @@
 import { HTTPHeaderLink } from "@hugoalh/http-header-link";
 import { getLogger } from "@logtape/logtape";
+import metadata from "../deno.json" with { type: "json" };
 import type { KvKey, KvStore } from "../federation/kv.ts";
 import { signRequest } from "../sig/http.ts";
 import { validateCryptoKey } from "../sig/key.ts";
@@ -75,6 +76,7 @@ function createRequest(url: string): Request {
   return new Request(url, {
     headers: {
       Accept: "application/activity+json, application/ld+json",
+      "User-Agent": getUserAgent(),
     },
     redirect: "manual",
   });
@@ -394,3 +396,32 @@ export function kvCache(
     return cache;
   };
 }
+
+/**
+ * Gets the user agent string for the given application and URL.
+ * @param app An optional application name and version, e.g., `"Hollo/1.0.0"`.
+ * @param url An optional URL to append to the user agent string.
+ *            Usually the URL of the ActivityPub instance.
+ * @returns The user agent string.
+ * @since 1.3.0
+ */
+export function getUserAgent(
+  app?: string | null,
+  url?: string | URL | null,
+): string {
+  const fedify = `Fedify/${metadata.version}`;
+  const runtime = "Deno" in globalThis
+    ? `Deno/${Deno.version.deno}`
+    : "Bun" in globalThis
+    // @ts-ignore: `Bun` is a global variable in Bun
+    ? `Bun/${Bun.version}`
+    : "process" in globalThis
+    // deno-lint-ignore no-process-globals
+    ? `Node.js/${process.version}`
+    : null;
+  const userAgent = app == null ? [fedify] : [app, fedify];
+  if (runtime != null) userAgent.push(runtime);
+  if (url != null) userAgent.push(`+${url.toString()}`);
+  const first = userAgent.shift();
+  return `${first} (${userAgent.join("; ")})`;
+}

src/webfinger/lookup.ts

@@ -1,4 +1,5 @@
 import { getLogger } from "@logtape/logtape";
+import { getUserAgent } from "../runtime/docloader.ts";
 import type { ResourceDescriptor } from "./jrd.ts";
 
 const logger = getLogger(["fedify", "webfinger", "lookup"]);
@@ -34,7 +35,10 @@ export async function lookupWebFinger(
     let response: Response;
     try {
       response = await fetch(url, {
-        headers: { Accept: "application/jrd+json" },
+        headers: {
+          Accept: "application/jrd+json",
+          "User-Agent": getUserAgent(),
+        },
         redirect: "manual",
       });
     } catch (error) {