Add a captcha short-code expander

service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerConfiguration.java

@@ -50,6 +50,7 @@ import org.whispersystems.textsecuregcm.configuration.ReportMessageConfiguration
 import org.whispersystems.textsecuregcm.configuration.SecureBackupServiceConfiguration;
 import org.whispersystems.textsecuregcm.configuration.SecureStorageServiceConfiguration;
 import org.whispersystems.textsecuregcm.configuration.SecureValueRecovery2Configuration;
+import org.whispersystems.textsecuregcm.configuration.ShortCodeExpanderConfiguration;
 import org.whispersystems.textsecuregcm.configuration.SpamFilterConfiguration;
 import org.whispersystems.textsecuregcm.configuration.StripeConfiguration;
 import org.whispersystems.textsecuregcm.configuration.SubscriptionConfiguration;
@@ -202,6 +203,11 @@ public class WhisperServerConfiguration extends Configuration {
   @JsonProperty
   private HCaptchaConfiguration hCaptcha;
 
+  @Valid
+  @NotNull
+  @JsonProperty
+  private ShortCodeExpanderConfiguration shortCode;
+
   @Valid
   @NotNull
   @JsonProperty
@@ -334,6 +340,10 @@ public class WhisperServerConfiguration extends Configuration {
     return hCaptcha;
   }
 
+  public ShortCodeExpanderConfiguration getShortCodeRetrieverConfiguration() {
+    return shortCode;
+  }
+
   public WebSocketConfiguration getWebSocketConfiguration() {
     return webSocket;
   }

service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java

@@ -83,6 +83,7 @@ import org.whispersystems.textsecuregcm.captcha.CaptchaChecker;
 import org.whispersystems.textsecuregcm.captcha.HCaptchaClient;
 import org.whispersystems.textsecuregcm.captcha.RecaptchaClient;
 import org.whispersystems.textsecuregcm.captcha.RegistrationCaptchaManager;
+import org.whispersystems.textsecuregcm.captcha.ShortCodeExpander;
 import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicConfiguration;
 import org.whispersystems.textsecuregcm.configuration.secrets.SecretStore;
 import org.whispersystems.textsecuregcm.configuration.secrets.SecretsModule;
@@ -581,7 +582,10 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
         .connectTimeout(Duration.ofSeconds(10)).build();
     HCaptchaClient hCaptchaClient = new HCaptchaClient(config.getHCaptchaConfiguration().apiKey().value(), hcaptchaHttpClient,
         dynamicConfigurationManager);
-    CaptchaChecker captchaChecker = new CaptchaChecker(List.of(recaptchaClient, hCaptchaClient));
+    HttpClient shortCodeRetrieverHttpClient = HttpClient.newBuilder().version(HttpClient.Version.HTTP_2)
+        .connectTimeout(Duration.ofSeconds(10)).build();
+    ShortCodeExpander shortCodeRetriever = new ShortCodeExpander(shortCodeRetrieverHttpClient, config.getShortCodeRetrieverConfiguration().baseUrl());
+    CaptchaChecker captchaChecker = new CaptchaChecker(shortCodeRetriever, List.of(recaptchaClient, hCaptchaClient));
 
     PushChallengeManager pushChallengeManager = new PushChallengeManager(pushNotificationManager,
         pushChallengeDynamoDb);

service/src/main/java/org/whispersystems/textsecuregcm/captcha/CaptchaChecker.java

@@ -29,9 +29,15 @@ public class CaptchaChecker {
   @VisibleForTesting
   static final String SEPARATOR = ".";
 
+  private static final String SHORT_SUFFIX = "-short";
+
+  private final ShortCodeExpander shortCodeExpander;
   private final Map<String, CaptchaClient> captchaClientMap;
 
-  public CaptchaChecker(final List<CaptchaClient> captchaClients) {
+  public CaptchaChecker(
+      final ShortCodeExpander shortCodeRetriever,
+      final List<CaptchaClient> captchaClients) {
+    this.shortCodeExpander = shortCodeRetriever;
     this.captchaClientMap = captchaClients.stream()
         .collect(Collectors.toMap(CaptchaClient::scheme, Function.identity()));
   }
@@ -63,9 +69,17 @@ public class CaptchaChecker {
     final String prefix = parts[0];
     final String siteKey = parts[1].toLowerCase(Locale.ROOT).strip();
     final String action = parts[2];
-    final String token = parts[3];
+    String token = parts[3];
 
-    final CaptchaClient client = this.captchaClientMap.get(prefix);
+    String provider = prefix;
+    if (prefix.endsWith(SHORT_SUFFIX)) {
+      // This is a "short" solution that points to the actual solution. We need to fetch the
+      // full solution before proceeding
+      provider = prefix.substring(0, prefix.length() - SHORT_SUFFIX.length());
+      token = shortCodeExpander.retrieve(token).orElseThrow(() -> new BadRequestException("invalid shortcode"));
+    }
+
+    final CaptchaClient client = this.captchaClientMap.get(provider);
     if (client == null) {
       throw new BadRequestException("invalid captcha scheme");
     }
@@ -92,7 +106,7 @@ public class CaptchaChecker {
     Metrics.counter(ASSESSMENTS_COUNTER_NAME,
             "action", action,
             "score", result.getScoreString(),
-            "provider", prefix)
+            "provider", provider)
         .increment();
     return result;
   }

service/src/main/java/org/whispersystems/textsecuregcm/captcha/ShortCodeExpander.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.captcha;
+
+import io.micrometer.core.instrument.Metrics;
+import org.apache.http.HttpStatus;
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.util.Optional;
+
+import static org.whispersystems.textsecuregcm.metrics.MetricsUtil.name;
+
+public class ShortCodeExpander {
+  private static final String EXPAND_COUNTER_NAME = name(ShortCodeExpander.class, "expand");
+
+  private final HttpClient client;
+  private final URI shortenerHost;
+
+  public ShortCodeExpander(final HttpClient client, final String shortenerHost) {
+    this.client = client;
+    this.shortenerHost = URI.create(shortenerHost);
+  }
+
+  public Optional<String> retrieve(final String shortCode) throws IOException {
+    final URI uri = shortenerHost.resolve("/" + shortCode);
+    final HttpRequest request = HttpRequest.newBuilder().uri(uri).GET().build();
+
+    try {
+      final HttpResponse<String> response = this.client.send(request, HttpResponse.BodyHandlers.ofString());
+      Metrics.counter(EXPAND_COUNTER_NAME, "responseCode", Integer.toString(response.statusCode())).increment();
+      return switch (response.statusCode()) {
+        case HttpStatus.SC_OK -> Optional.of(response.body());
+        case HttpStatus.SC_NOT_FOUND -> Optional.empty();
+        default -> throw new IOException("Failed to look up shortcode");
+      };
+    } catch (InterruptedException e) {
+      throw new IOException(e);
+    }
+  }
+
+
+
+}

service/src/main/java/org/whispersystems/textsecuregcm/configuration/ShortCodeExpanderConfiguration.java

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.configuration;
+
+public record ShortCodeExpanderConfiguration(String baseUrl) {
+}