feat: add JwtCredentials with custom claims (#290)

* Implement JwtCredentials class. Switch cache to index by claims

* DI clock and lifeSpanSeconds

* Adding Serializable and adding test

* Lock for JwtCredentials

* Add tests for verifying access tokens and withClaims

* Add tests for withClaims for ServiceAccountJwtAccessCredentials

* Fix dependency issues

* Add CLOCK_SKEW (5 minutes) for shouldRefresh()

* Adding some javadocs

* withClaims -> jwtWithClaims and create JwtProvider interface

* Fix javadoc

* Address some PR review nits

* expiry -> expiryInSeconds

* Disallow null values in JwtCredentials.Builder

* Update license header for the added files

* Address PR review comments

* Remove extra whitespace

* Fix lint

* Refactor JwtCredentials.Claims -> JwtClaims

* fix formatting

* javadocs 'New claims' -> 'new claims'

oauth2_http/java/com/google/auth/oauth2/JwtClaims.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2019, 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.oauth2;
+
+import com.google.auto.value.AutoValue;
+import java.io.Serializable;
+import javax.annotation.Nullable;
+
+/**
+ * Value class representing the set of fields used as the payload of a JWT token.
+ *
+ * <p>To create and customize claims, use the builder:
+ *
+ * <pre><code>
+ * Claims claims = Claims.newBuilder()
+ *     .setAudience("https://example.com/some-audience")
+ *     .setIssuer("some-issuer@example.com")
+ *     .setSubject("some-subject@example.com")
+ *     .build();
+ * </code></pre>
+ */
+@AutoValue
+public abstract class JwtClaims implements Serializable {
+  private static final long serialVersionUID = 4974444151019426702L;
+
+  @Nullable
+  abstract String getAudience();
+
+  @Nullable
+  abstract String getIssuer();
+
+  @Nullable
+  abstract String getSubject();
+
+  static Builder newBuilder() {
+    return new AutoValue_JwtClaims.Builder();
+  }
+
+  /**
+   * Returns a new Claims instance with overridden fields.
+   *
+   * <p>Any non-null field will overwrite the value from the original claims instance.
+   *
+   * @param other claims to override
+   * @return new claims
+   */
+  public JwtClaims merge(JwtClaims other) {
+    return newBuilder()
+        .setAudience(other.getAudience() == null ? getAudience() : other.getAudience())
+        .setIssuer(other.getIssuer() == null ? getIssuer() : other.getIssuer())
+        .setSubject(other.getSubject() == null ? getSubject() : other.getSubject())
+        .build();
+  }
+
+  /**
+   * Returns whether or not this set of claims is complete.
+   *
+   * <p>Audience, issuer, and subject are required to be set in order to use the claim set for a JWT
+   * token. An incomplete Claims instance is useful for overriding claims when using {@link
+   * ServiceAccountJwtAccessCredentials#jwtWithClaims(JwtClaims)} or {@link
+   * JwtCredentials#jwtWithClaims(JwtClaims)}.
+   *
+   * @return
+   */
+  public boolean isComplete() {
+    return getAudience() != null && getIssuer() != null && getSubject() != null;
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    abstract Builder setAudience(String audience);
+
+    abstract Builder setIssuer(String issuer);
+
+    abstract Builder setSubject(String subject);
+
+    abstract JwtClaims build();
+  }
+}

oauth2_http/java/com/google/auth/oauth2/JwtCredentials.java

@@ -0,0 +1,259 @@
+/*
+ * Copyright 2019, 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.oauth2;
+
+import com.google.api.client.json.webtoken.JsonWebSignature;
+import com.google.api.client.json.webtoken.JsonWebToken;
+import com.google.api.client.util.Clock;
+import com.google.auth.Credentials;
+import com.google.auth.http.AuthHttpConstants;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+import java.io.IOException;
+import java.net.URI;
+import java.security.GeneralSecurityException;
+import java.security.PrivateKey;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Credentials class for calling Google APIs using a JWT with custom claims.
+ *
+ * <p>Uses a JSON Web Token (JWT) directly in the request metadata to provide authorization.
+ *
+ * <pre><code>
+ * JwtClaims claims = JwtClaims.newBuilder()
+ *     .setAudience("https://example.com/some-audience")
+ *     .setIssuer("some-issuer@example.com")
+ *     .setSubject("some-subject@example.com")
+ *     .build();
+ * Credentials = JwtCredentials.newBuilder()
+ *     .setPrivateKey(privateKey)
+ *     .setPrivateKeyId("private-key-id")
+ *     .setJwtClaims(claims)
+ *     .build();
+ * </code></pre>
+ */
+public class JwtCredentials extends Credentials implements JwtProvider {
+  private static final String JWT_ACCESS_PREFIX = OAuth2Utils.BEARER_PREFIX;
+  private static final String JWT_INCOMPLETE_ERROR_MESSAGE =
+      "JWT claims must contain audience, " + "issuer, and subject.";
+  private static final long CLOCK_SKEW = TimeUnit.MINUTES.toSeconds(5);
+
+  // byte[] is serializable, so the lock variable can be final
+  private final Object lock = new byte[0];
+  private final PrivateKey privateKey;
+  private final String privateKeyId;
+  private final JwtClaims jwtClaims;
+  private final Long lifeSpanSeconds;
+  @VisibleForTesting transient Clock clock;
+
+  private transient String jwt;
+  // The date (represented as seconds since the epoch) that the generated JWT expires
+  private transient Long expiryInSeconds;
+
+  private JwtCredentials(Builder builder) {
+    this.privateKey = Preconditions.checkNotNull(builder.getPrivateKey());
+    this.privateKeyId = Preconditions.checkNotNull(builder.getPrivateKeyId());
+    this.jwtClaims = Preconditions.checkNotNull(builder.getJwtClaims());
+    Preconditions.checkState(jwtClaims.isComplete(), JWT_INCOMPLETE_ERROR_MESSAGE);
+    this.lifeSpanSeconds = Preconditions.checkNotNull(builder.getLifeSpanSeconds());
+    this.clock = Preconditions.checkNotNull(builder.getClock());
+  }
+
+  public static Builder newBuilder() {
+    return new Builder();
+  }
+
+  /** Refresh the token by discarding the cached token and metadata and rebuilding a new one. */
+  @Override
+  public void refresh() throws IOException {
+    JsonWebSignature.Header header = new JsonWebSignature.Header();
+    header.setAlgorithm("RS256");
+    header.setType("JWT");
+    header.setKeyId(privateKeyId);
+
+    JsonWebToken.Payload payload = new JsonWebToken.Payload();
+    payload.setAudience(jwtClaims.getAudience());
+    payload.setIssuer(jwtClaims.getIssuer());
+    payload.setSubject(jwtClaims.getSubject());
+
+    long currentTime = clock.currentTimeMillis();
+    payload.setIssuedAtTimeSeconds(currentTime / 1000);
+    payload.setExpirationTimeSeconds(currentTime / 1000 + lifeSpanSeconds);
+
+    synchronized (lock) {
+      this.expiryInSeconds = payload.getExpirationTimeSeconds();
+
+      try {
+        this.jwt =
+            JsonWebSignature.signUsingRsaSha256(
+                privateKey, OAuth2Utils.JSON_FACTORY, header, payload);
+      } catch (GeneralSecurityException e) {
+        throw new IOException(
+            "Error signing service account JWT access header with private key.", e);
+      }
+    }
+  }
+
+  private boolean shouldRefresh() {
+    return expiryInSeconds == null
+        || getClock().currentTimeMillis() / 1000 > expiryInSeconds - CLOCK_SKEW;
+  }
+
+  /**
+   * Returns a copy of these credentials with modified claims.
+   *
+   * @param newClaims new claims. Any unspecified claim fields default to the the current values.
+   * @return new credentials
+   */
+  @Override
+  public JwtCredentials jwtWithClaims(JwtClaims newClaims) {
+    return JwtCredentials.newBuilder()
+        .setPrivateKey(privateKey)
+        .setPrivateKeyId(privateKeyId)
+        .setJwtClaims(jwtClaims.merge(newClaims))
+        .build();
+  }
+
+  @Override
+  public String getAuthenticationType() {
+    return "JWT";
+  }
+
+  @Override
+  public Map<String, List<String>> getRequestMetadata(URI uri) throws IOException {
+    synchronized (lock) {
+      if (shouldRefresh()) {
+        refresh();
+      }
+      List<String> newAuthorizationHeaders = Collections.singletonList(JWT_ACCESS_PREFIX + jwt);
+      return Collections.singletonMap(AuthHttpConstants.AUTHORIZATION, newAuthorizationHeaders);
+    }
+  }
+
+  @Override
+  public boolean hasRequestMetadata() {
+    return true;
+  }
+
+  @Override
+  public boolean hasRequestMetadataOnly() {
+    return true;
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (!(obj instanceof JwtCredentials)) {
+      return false;
+    }
+    JwtCredentials other = (JwtCredentials) obj;
+    return Objects.equals(this.privateKey, other.privateKey)
+        && Objects.equals(this.privateKeyId, other.privateKeyId)
+        && Objects.equals(this.jwtClaims, other.jwtClaims)
+        && Objects.equals(this.lifeSpanSeconds, other.lifeSpanSeconds);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(this.privateKey, this.privateKeyId, this.jwtClaims, this.lifeSpanSeconds);
+  }
+
+  Clock getClock() {
+    if (clock == null) {
+      clock = Clock.SYSTEM;
+    }
+    return clock;
+  }
+
+  public static class Builder {
+    private PrivateKey privateKey;
+    private String privateKeyId;
+    private JwtClaims jwtClaims;
+    private Clock clock = Clock.SYSTEM;
+    private Long lifeSpanSeconds = TimeUnit.HOURS.toSeconds(1);
+
+    protected Builder() {}
+
+    public Builder setPrivateKey(PrivateKey privateKey) {
+      this.privateKey = Preconditions.checkNotNull(privateKey);
+      return this;
+    }
+
+    public PrivateKey getPrivateKey() {
+      return privateKey;
+    }
+
+    public Builder setPrivateKeyId(String privateKeyId) {
+      this.privateKeyId = Preconditions.checkNotNull(privateKeyId);
+      return this;
+    }
+
+    public String getPrivateKeyId() {
+      return privateKeyId;
+    }
+
+    public Builder setJwtClaims(JwtClaims claims) {
+      this.jwtClaims = Preconditions.checkNotNull(claims);
+      return this;
+    }
+
+    public JwtClaims getJwtClaims() {
+      return jwtClaims;
+    }
+
+    public Builder setLifeSpanSeconds(Long lifeSpanSeconds) {
+      this.lifeSpanSeconds = Preconditions.checkNotNull(lifeSpanSeconds);
+      return this;
+    }
+
+    public Long getLifeSpanSeconds() {
+      return lifeSpanSeconds;
+    }
+
+    Builder setClock(Clock clock) {
+      this.clock = Preconditions.checkNotNull(clock);
+      return this;
+    }
+
+    Clock getClock() {
+      return clock;
+    }
+
+    public JwtCredentials build() {
+      return new JwtCredentials(this);
+    }
+  }
+}