feat: default authentication support for external hosts

google-cloud-spanner/clirr-ignored-differences.xml

@@ -822,4 +822,10 @@
     <method>java.lang.Object runTransaction(com.google.cloud.spanner.connection.Connection$TransactionCallable)</method>
   </difference>
 
+  <!-- Added external host option -->
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/SpannerOptions$SpannerEnvironment</className>
+    <method>com.google.auth.oauth2.GoogleCredentials getDefaultExternalHostCredentials()</method>
+  </difference>
 </differences>

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

@@ -34,6 +34,8 @@
 import com.google.api.gax.tracing.ApiTracerFactory;
 import com.google.api.gax.tracing.BaseApiTracerFactory;
 import com.google.api.gax.tracing.OpencensusTracerFactory;
+import com.google.auth.oauth2.AccessToken;
+import com.google.auth.oauth2.GoogleCredentials;
 import com.google.cloud.NoCredentials;
 import com.google.cloud.ServiceDefaults;
 import com.google.cloud.ServiceOptions;
@@ -56,6 +58,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
@@ -79,8 +82,11 @@
 import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Paths;
 import java.time.Duration;
 import java.util.ArrayList;
+import java.util.Base64;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -92,6 +98,7 @@
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.regex.Pattern;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;
@@ -110,6 +117,11 @@ public class SpannerOptions extends ServiceOptions<Spanner, SpannerOptions> {
 
   private static final String API_SHORT_NAME = "Spanner";
   private static final String DEFAULT_HOST = "https://spanner.googleapis.com";
+  private static final String CLOUD_SPANNER_HOST_FORMAT = ".*\\.googleapis\\.com.*";
+
+  @VisibleForTesting
+  static final Pattern CLOUD_SPANNER_HOST_PATTERN = Pattern.compile(CLOUD_SPANNER_HOST_FORMAT);
+
   private static final ImmutableSet<String> SCOPES =
       ImmutableSet.of(
           "https://www.googleapis.com/auth/spanner.admin",
@@ -843,8 +855,15 @@ default boolean isEnableEndToEndTracing() {
     default String getMonitoringHost() {
       return null;
     }
+
+    default GoogleCredentials getDefaultExternalHostCredentials() {
+      return null;
+    }
   }
 
+  static final String DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS =
+      "SPANNER_EXTERNAL_HOST_AUTH_TOKEN";
+
   /**
    * Default implementation of {@link SpannerEnvironment}. Reads all configuration from environment
    * variables.
@@ -900,6 +919,11 @@ public boolean isEnableEndToEndTracing() {
     public String getMonitoringHost() {
       return System.getenv(SPANNER_MONITORING_HOST);
     }
+
+    @Override
+    public GoogleCredentials getDefaultExternalHostCredentials() {
+      return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS));
+    }
   }
 
   /** Builder for {@link SpannerOptions} instances. */
@@ -967,6 +991,7 @@ public static class Builder
     private boolean enableBuiltInMetrics = SpannerOptions.environment.isEnableBuiltInMetrics();
     private String monitoringHost = SpannerOptions.environment.getMonitoringHost();
     private SslContext mTLSContext = null;
+    private boolean isExternalHost = false;
 
     private static String createCustomClientLibToken(String token) {
       return token + " " + ServiceOptions.getGoogApiClientLibName();
@@ -1459,6 +1484,9 @@ public Builder setDecodeMode(DecodeMode decodeMode) {
     @Override
     public Builder setHost(String host) {
       super.setHost(host);
+      if (!CLOUD_SPANNER_HOST_PATTERN.matcher(host).matches()) {
+        this.isExternalHost = true;
+      }
       // Setting a host should override any SPANNER_EMULATOR_HOST setting.
       setEmulatorHost(null);
       return this;
@@ -1629,6 +1657,8 @@ public SpannerOptions build() {
         this.setChannelConfigurator(ManagedChannelBuilder::usePlaintext);
         // As we are using plain text, we should never send any credentials.
         this.setCredentials(NoCredentials.getInstance());
+      } else if (isExternalHost && credentials == null) {
+        credentials = environment.getDefaultExternalHostCredentials();
       }
       if (this.numChannels == null) {
         this.numChannels =
@@ -1669,6 +1699,24 @@ public static void useDefaultEnvironment() {
     SpannerOptions.environment = SpannerEnvironmentImpl.INSTANCE;
   }
 
+  @InternalApi
+  public static GoogleCredentials getDefaultExternalHostCredentialsFromSysEnv() {
+    return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS));
+  }
+
+  private static @Nullable GoogleCredentials getOAuthTokenFromFile(@Nullable String file) {
+    if (!Strings.isNullOrEmpty(file)) {
+      String token;
+      try {
+        token = Base64.getEncoder().encodeToString(Files.readAllBytes(Paths.get(file)));
+      } catch (IOException e) {
+        throw SpannerExceptionFactory.newSpannerException(e);
+      }
+      return GoogleCredentials.create(new AccessToken(token, null));
+    }
+    return null;
+  }
+
   /**
    * Enables OpenTelemetry traces. Enabling OpenTelemetry traces will disable OpenCensus traces. By
    * default, OpenCensus traces are enabled.

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionOptions.java

@@ -921,6 +921,8 @@ private ConnectionOptions(Builder builder) {
             getInitialConnectionPropertyValue(AUTO_CONFIG_EMULATOR),
             usePlainText,
             System.getenv());
+    GoogleCredentials defaultExternalHostCredentials =
+        SpannerOptions.getDefaultExternalHostCredentialsFromSysEnv();
     // Using credentials on a plain text connection is not allowed, so if the user has not specified
     // any credentials and is using a plain text connection, we should not try to get the
     // credentials from the environment, but default to NoCredentials.
@@ -935,6 +937,8 @@ && getInitialConnectionPropertyValue(OAUTH_TOKEN) == null
       this.credentials =
           new GoogleCredentials(
               new AccessToken(getInitialConnectionPropertyValue(OAUTH_TOKEN), null));
+    } else if (isExternalHost && defaultExternalHostCredentials != null) {
+      this.credentials = defaultExternalHostCredentials;
     } else if (getInitialConnectionPropertyValue(CREDENTIALS_PROVIDER) != null) {
       try {
         this.credentials = getInitialConnectionPropertyValue(CREDENTIALS_PROVIDER).getCredentials();

google-cloud-spanner/src/test/java/com/google/cloud/spanner/SpannerOptionsTest.java

@@ -16,6 +16,7 @@
 
 package com.google.cloud.spanner;
 
+import static com.google.cloud.spanner.SpannerOptions.CLOUD_SPANNER_HOST_PATTERN;
 import static com.google.common.truth.Truth.assertThat;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -1164,4 +1165,12 @@ public void checkGlobalOpenTelemetryWhenNotInjected() {
             .build();
     assertEquals(GlobalOpenTelemetry.get(), options.getOpenTelemetry());
   }
+
+  @Test
+  public void testCloudSpannerHostPattern() {
+    assertTrue(CLOUD_SPANNER_HOST_PATTERN.matcher("https://spanner.googleapis.com").matches());
+    assertTrue(
+        CLOUD_SPANNER_HOST_PATTERN.matcher("https://product-area.googleapis.com:443").matches());
+    assertFalse(CLOUD_SPANNER_HOST_PATTERN.matcher("https://some-company.com:443").matches());
+  }
 }