From 00a3e562dcda323d7226f1ea9df146f37bf01bb3 Mon Sep 17 00:00:00 2001
From: Ehren Kret <ehren@signal.org>
Date: Fri, 20 Nov 2020 14:41:48 -0600
Subject: [PATCH] Force use of UCS-2 instead of GSM-7 for SMS to China (#297)

---
 .../textsecuregcm/sms/TwilioSmsSender.java    | 21 +++++++++++++------
 .../tests/sms/TwilioSmsSenderTest.java        | 14 +++++++++++++
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/sms/TwilioSmsSender.java b/service/src/main/java/org/whispersystems/textsecuregcm/sms/TwilioSmsSender.java
index 9d37c0e76..75c632091 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/sms/TwilioSmsSender.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/sms/TwilioSmsSender.java
@@ -22,6 +22,7 @@ import org.whispersystems.textsecuregcm.util.ExecutorUtils;
 import org.whispersystems.textsecuregcm.util.SystemMapper;
 import org.whispersystems.textsecuregcm.util.Util;
 
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.io.IOException;
 import java.net.URI;
@@ -113,7 +114,7 @@ public class TwilioSmsSender {
     Map<String, String> requestParameters = new HashMap<>();
     requestParameters.put("To", destination);
     boolean usedSenderId = setOriginationRequestParameter(destination, requestParameters, enableSenderId);
-    requestParameters.put("Body", String.format(Locale.US, getBodyFormatString(clientType.orElse(null)), verificationCode));
+    requestParameters.put("Body", String.format(Locale.US, getBodyFormatString(destination, clientType.orElse(null)), verificationCode));
 
     HttpRequest request = HttpRequest.newBuilder()
                                      .uri(smsUri)
@@ -129,15 +130,23 @@ public class TwilioSmsSender {
                      .thenCompose(twilioResponse -> retrySendSmsVerificationIfApplicable(usedSenderId, twilioResponse, destination, clientType, verificationCode));
   }
 
-  private String getBodyFormatString(@Nullable String clientType) {
+  private String getBodyFormatString(@Nonnull String destination, @Nullable String clientType) {
+    final String result;
     if ("ios".equals(clientType)) {
-      return iosVerificationText;
+      result = iosVerificationText;
     } else if ("android-ng".equals(clientType)) {
-      return androidNgVerificationText;
+      result = androidNgVerificationText;
     } else if ("android-2020-01".equals(clientType)) {
-      return android202001VerificationText;
+      result = android202001VerificationText;
     } else {
-      return genericVerificationText;
+      result = genericVerificationText;
+    }
+    if (destination.startsWith("+86")) {  // is China
+      return result + "\u2008";
+      // Twilio recommends adding this character to the end of strings delivered to China because some carriers in
+      // China are blocking GSM-7 encoding and this will force Twilio to send using UCS-2 instead.
+    } else {
+      return result;
     }
   }
 
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/tests/sms/TwilioSmsSenderTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/tests/sms/TwilioSmsSenderTest.java
index 258f7859a..d551e436b 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/tests/sms/TwilioSmsSenderTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/tests/sms/TwilioSmsSenderTest.java
@@ -338,4 +338,18 @@ public class TwilioSmsSenderTest {
             .withHeader("Content-Type", equalTo("application/x-www-form-urlencoded"))
             .withRequestBody(equalTo("MessagingServiceSid=test_messaging_services_id&To=%2B14153333333&Body=%3C%23%3E+Verify+on+AndroidNg%3A+123-456%0A%0Acharacters")));
   }
+
+  @Test
+  public void testSendSmsChina() {
+    setupSuccessStubForSms();
+    TwilioConfiguration configuration = createTwilioConfiguration();
+    TwilioSmsSender sender  = new TwilioSmsSender("http://localhost:" + wireMockRule.port(), configuration);
+    boolean success = sender.deliverSmsVerification("+861065529988", Optional.of("android-ng"), "123-456").join();
+
+    assertThat(success).isTrue();
+
+    verify(1, postRequestedFor(urlEqualTo("/2010-04-01/Accounts/" + ACCOUNT_ID + "/Messages.json"))
+            .withHeader("Content-Type", equalTo("application/x-www-form-urlencoded"))
+            .withRequestBody(equalTo("MessagingServiceSid=test_messaging_services_id&To=%2B861065529988&Body=%3C%23%3E+Verify+on+AndroidNg%3A+123-456%0A%0Acharacters%E2%80%88")));
+  }
 }