feat(mtls): Introduce DefaultMtlsProviderFactory and SecureConnectProvider

oauth2_http/java/com/google/auth/mtls/CertificateSourceUnavailableException.java

@@ -1,18 +1,17 @@
 /*
- * Copyright 2025, Google Inc. All rights reserved.
+ * Copyright 2025 Google LLC
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
- *    * Redistributions of source code must retain the above copyright
+ *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
- *    * Redistributions in binary form must reproduce the above
+ *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
- *
- *    * Neither the name of Google Inc. nor the names of its
+ *     * Neither the name of Google LLC nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *

oauth2_http/java/com/google/auth/mtls/ContextAwareMetadataJson.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.auth.mtls;
+
+import com.google.api.client.json.GenericJson;
+import com.google.api.client.util.Key;
+import com.google.common.collect.ImmutableList;
+import java.util.List;
+
+/** Data class representing context_aware_metadata.json file. */
+public class ContextAwareMetadataJson extends GenericJson {
+  /** Cert provider command */
+  @Key("cert_provider_command")
+  private List<String> commands;
+
+  /** Returns the cert provider command. */
+  public final ImmutableList<String> getCommands() {
+    return ImmutableList.copyOf(commands);
+  }
+}

oauth2_http/java/com/google/auth/mtls/DefaultMtlsProviderFactory.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.auth.mtls;
+
+import java.io.IOException;
+
+public class DefaultMtlsProviderFactory {
+
+  /**
+   * Creates an instance of {@link MtlsProvider}. It first attempts to create an {@link
+   * com.google.auth.mtls.X509Provider}. If the certificate source is unavailable, it falls back to
+   * creating a {@link SecureConnectProvider}. If the secure connect provider also fails, it throws
+   * the original {@link com.google.auth.mtls.CertificateSourceUnavailableException}.
+   *
+   * @return an instance of {@link MtlsProvider}.
+   * @throws com.google.auth.mtls.CertificateSourceUnavailableException if neither provider can be
+   *     created.
+   * @throws IOException if an I/O error occurs during provider creation.
+   */
+  public static MtlsProvider create() throws IOException {
+    MtlsProvider mtlsProvider;
+    try {
+      mtlsProvider = new X509Provider();
+      mtlsProvider.getKeyStore();
+      return mtlsProvider;
+    } catch (CertificateSourceUnavailableException e) {
+      try {
+        mtlsProvider = new SecureConnectProvider();
+        mtlsProvider.getKeyStore();
+        return mtlsProvider;
+      } catch (CertificateSourceUnavailableException ex) {
+        throw new CertificateSourceUnavailableException(
+            "No MtlsSource is available on this device.");
+      }
+    }
+  }
+}

oauth2_http/java/com/google/auth/mtls/MtlsProvider.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.auth.mtls;
+
+import java.io.IOException;
+import java.security.KeyStore;
+
+/**
+ * MtlsProvider is used by the Gax library for configuring mutual TLS in the HTTP and GRPC transport
+ * layer. The source of the client certificate is up to the implementation.
+ *
+ * <p>Note: This interface will replace the identically named "MtlsProvider" implementation in the
+ * Gax library. The Gax library version of MtlsProvider will be marked as deprecated.
+ */
+public interface MtlsProvider {
+  /** Returns the mutual TLS key store. */
+  KeyStore getKeyStore() throws IOException;
+}

oauth2_http/java/com/google/auth/mtls/SecureConnectProvider.java

@@ -0,0 +1,161 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.auth.mtls;
+
+import com.google.api.client.json.JsonParser;
+import com.google.api.client.json.gson.GsonFactory;
+import com.google.api.client.util.SecurityUtils;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.GeneralSecurityException;
+import java.security.KeyStore;
+import java.util.List;
+
+/**
+ * This class implements {@link MtlsProvider} for the Google Auth library transport layer via {@link
+ * ContextAwareMetadataJson}. This is only meant to be used internally by Google Cloud libraries,
+ * and the public facing methods may be changed without notice, and have no guarantee of backwards
+ * compatability.
+ *
+ * <p>Note: This implementation is derived from the existing "MtlsProvider" found in the Gax
+ * library, with two notable differences: 1) All logic associated with parsing environment variables
+ * related to "mTLS usage" are omitted - a separate helper class will be introduced in the Gax
+ * library to serve this purpose. 2) getKeyStore throws {@link
+ * com.google.auth.mtls.CertificateSourceUnavailableException} instead of returning "null" if this
+ * cert source is not available on the device.
+ *
+ * <p>Additionally, this implementation will replace the existing "MtlsProvider" in the Gax library.
+ * The Gax library version of MtlsProvider will be marked as deprecated.
+ */
+public class SecureConnectProvider implements MtlsProvider {
+  interface ProcessProvider {
+    public Process createProcess(InputStream metadata) throws IOException;
+  }
+
+  static class DefaultProcessProvider implements ProcessProvider {
+    @Override
+    public Process createProcess(InputStream metadata) throws IOException {
+      if (metadata == null) {
+        return null;
+      }
+      List<String> command = extractCertificateProviderCommand(metadata);
+      return new ProcessBuilder(command).start();
+    }
+  }
+
+  private static final String DEFAULT_CONTEXT_AWARE_METADATA_PATH =
+      System.getProperty("user.home") + "/.secureConnect/context_aware_metadata.json";
+
+  private String metadataPath;
+  private ProcessProvider processProvider;
+
+  @VisibleForTesting
+  SecureConnectProvider(ProcessProvider processProvider, String metadataPath) {
+    this.processProvider = processProvider;
+    this.metadataPath = metadataPath;
+  }
+
+  public SecureConnectProvider() {
+    this(new DefaultProcessProvider(), DEFAULT_CONTEXT_AWARE_METADATA_PATH);
+  }
+
+  /** The mutual TLS key store created with the default client certificate on device. */
+  @Override
+  public KeyStore getKeyStore() throws IOException {
+    try (InputStream stream = new FileInputStream(metadataPath)) {
+      return getKeyStore(stream, processProvider);
+    } catch (InterruptedException e) {
+      throw new IOException("Interrupted executing certificate provider command", e);
+    } catch (GeneralSecurityException e) {
+      throw new CertificateSourceUnavailableException(
+          "SecureConnect encountered GeneralSecurityException:", e);
+    } catch (FileNotFoundException exception) {
+      // If the metadata file doesn't exist, then there is no key store, so we will throw sentinel
+      // error
+      throw new CertificateSourceUnavailableException("SecureConnect metadata does not exist.");
+    }
+  }
+
+  @VisibleForTesting
+  static KeyStore getKeyStore(InputStream metadata, ProcessProvider processProvider)
+      throws IOException, InterruptedException, GeneralSecurityException {
+    Process process = processProvider.createProcess(metadata);
+
+    // Run the command and timeout after 1000 milliseconds.
+    int exitCode = runCertificateProviderCommand(process, 1000);
+    if (exitCode != 0) {
+      throw new IOException("Cert provider command failed with exit code: " + exitCode);
+    }
+
+    // Create mTLS key store with the input certificates from shell command.
+    return SecurityUtils.createMtlsKeyStore(process.getInputStream());
+  }
+
+  @VisibleForTesting
+  static ImmutableList<String> extractCertificateProviderCommand(InputStream contextAwareMetadata)
+      throws IOException {
+    JsonParser parser = new GsonFactory().createJsonParser(contextAwareMetadata);
+    ContextAwareMetadataJson json = parser.parse(ContextAwareMetadataJson.class);
+    return json.getCommands();
+  }
+
+  @VisibleForTesting
+  static int runCertificateProviderCommand(Process commandProcess, long timeoutMilliseconds)
+      throws IOException, InterruptedException {
+    long startTime = System.currentTimeMillis();
+    long remainTime = timeoutMilliseconds;
+
+    // In the while loop, keep checking if the process is terminated every 100 milliseconds
+    // until timeout is reached or process is terminated. In getKeyStore we set timeout to
+    // 1000 milliseconds, so 100 millisecond is a good number for the sleep.
+    while (remainTime > 0) {
+      Thread.sleep(Math.min(remainTime + 1, 100));
+      remainTime -= System.currentTimeMillis() - startTime;
+
+      try {
+        return commandProcess.exitValue();
+      } catch (IllegalThreadStateException ignored) {
+        // exitValue throws IllegalThreadStateException if process has not yet terminated.
+        // Once the process is terminated, exitValue no longer throws exception. Therefore
+        // in the while loop, we use exitValue to check if process is terminated. See
+        // https://docs.oracle.com/javase/7/docs/api/java/lang/Process.html#exitValue()
+        // for more details.
+      }
+    }
+
+    commandProcess.destroy();
+    throw new IOException("cert provider command timed out");
+  }
+}

oauth2_http/java/com/google/auth/mtls/WorkloadCertificateConfiguration.java

@@ -1,18 +1,17 @@
 /*
- * Copyright 2025, Google Inc. All rights reserved.
+ * Copyright 2025 Google LLC
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
- *    * Redistributions of source code must retain the above copyright
+ *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
- *    * Redistributions in binary form must reproduce the above
+ *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
- *
- *    * Neither the name of Google Inc. nor the names of its
+ *     * Neither the name of Google LLC nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *