Add source field to user-agent header (#2230)

Author: xavdid

src/main/java/com/stripe/net/HttpClient.java

@@ -7,6 +7,7 @@
 import java.io.InputStream;
 import java.net.ConnectException;
 import java.net.SocketTimeoutException;
+import java.security.MessageDigest;
 import java.time.Duration;
 import java.util.HashMap;
 import java.util.Map;
@@ -26,6 +27,53 @@ public abstract class HttpClient {
   /** A value indicating whether the client should sleep between automatic request retries. */
   boolean networkRetriesSleep = true;
 
+  static String UNAME_HASH = computeUnameHash();
+
+  private static String computeUnameHash() {
+    String uname = "";
+    try {
+      uname =
+          (System.getProperty("os.name", "")
+                  + " "
+                  + System.getProperty("os.version", "")
+                  + " "
+                  + System.getProperty("os.arch", "")
+                  + " "
+                  + System.getProperty("java.version", "")
+                  + " "
+                  + System.getProperty("java.vendor", "")
+                  + " "
+                  + System.getProperty("java.vm.name", "")
+                  + " "
+                  + getHostname())
+              .trim();
+    } catch (Exception e) {
+      // fall through with empty string
+    }
+    if (uname.isEmpty()) {
+      return "";
+    }
+    try {
+      MessageDigest md = MessageDigest.getInstance("MD5");
+      byte[] hashBytes = md.digest(uname.getBytes(java.nio.charset.StandardCharsets.UTF_8));
+      StringBuilder sb = new StringBuilder();
+      for (byte b : hashBytes) {
+        sb.append(String.format("%02x", b));
+      }
+      return sb.toString();
+    } catch (Exception e) {
+      return "";
+    }
+  }
+
+  private static String getHostname() {
+    try {
+      return java.net.InetAddress.getLocalHost().getHostName();
+    } catch (Exception e) {
+      return "";
+    }
+  }
+
   /** Initializes a new instance of the {@link HttpClient} class. */
   protected HttpClient() {}
 
@@ -228,6 +276,10 @@ static String buildXStripeClientUserAgentString(String aiAgent) {
       propertyMap.put("ai_agent", aiAgent);
     }
 
+    if (!UNAME_HASH.isEmpty()) {
+      propertyMap.put("source", UNAME_HASH);
+    }
+
     return ApiResource.INTERNAL_GSON.toJson(propertyMap);
   }
 

src/test/java/com/stripe/net/HttpClientTest.java

@@ -1,6 +1,7 @@
 package com.stripe.net;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -295,4 +296,31 @@ public void testBuildXStripeClientUserAgentStringNoPlatformWithoutTelemetry() {
       Stripe.enableTelemetry = originalTelemetry;
     }
   }
+
+  @Test
+  public void testBuildXStripeClientUserAgentStringIncludesSource() {
+    String json = HttpClient.buildXStripeClientUserAgentString("");
+    com.google.gson.JsonObject parsed =
+        com.google.gson.JsonParser.parseString(json).getAsJsonObject();
+    // "source" should be present and be a 32-character lowercase MD5 hex digest
+    assertTrue(parsed.has("source"), "Expected 'source' field in X-Stripe-Client-User-Agent");
+    String source = parsed.get("source").getAsString();
+    assertTrue(
+        source.matches("[0-9a-f]{32}"),
+        "Expected 'source' to be a 32-character lowercase hex string, got: " + source);
+  }
+
+  @Test
+  public void testBuildXStripeClientUserAgentStringOmitsSourceWhenEmpty() throws Exception {
+    String savedHash = HttpClient.UNAME_HASH;
+    try {
+      HttpClient.UNAME_HASH = "";
+      String userAgentString = HttpClient.buildXStripeClientUserAgentString("");
+      com.google.gson.JsonObject userAgent =
+          com.google.gson.JsonParser.parseString(userAgentString).getAsJsonObject();
+      assertFalse(userAgent.has("source"));
+    } finally {
+      HttpClient.UNAME_HASH = savedHash;
+    }
+  }
 }