Use tuf to init signer and verifier

sigstore-java/src/main/java/dev/sigstore/KeylessSigner2.java

@@ -0,0 +1,378 @@
+/*
+ * Copyright 2022 The Sigstore Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package dev.sigstore;
+
+import com.google.api.client.util.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.hash.Hashing;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
+import com.google.errorprone.annotations.CheckReturnValue;
+import com.google.errorprone.annotations.concurrent.GuardedBy;
+import dev.sigstore.encryption.certificates.Certificates;
+import dev.sigstore.encryption.signers.Signer;
+import dev.sigstore.encryption.signers.Signers;
+import dev.sigstore.fulcio.client.CertificateRequest;
+import dev.sigstore.fulcio.client.FulcioClient2;
+import dev.sigstore.fulcio.client.FulcioVerificationException;
+import dev.sigstore.fulcio.client.FulcioVerifier2;
+import dev.sigstore.fulcio.client.SigningCertificate;
+import dev.sigstore.fulcio.client.UnsupportedAlgorithmException;
+import dev.sigstore.oidc.client.OidcClients;
+import dev.sigstore.oidc.client.OidcException;
+import dev.sigstore.oidc.client.OidcToken;
+import dev.sigstore.rekor.client.HashedRekordRequest;
+import dev.sigstore.rekor.client.RekorClient2;
+import dev.sigstore.rekor.client.RekorParseException;
+import dev.sigstore.rekor.client.RekorVerificationException;
+import dev.sigstore.rekor.client.RekorVerifier2;
+import dev.sigstore.tuf.SigstoreTufClient;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SignatureException;
+import java.security.cert.CertificateException;
+import java.security.spec.InvalidKeySpecException;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * A full sigstore keyless signing flow.
+ *
+ * <p>Note: the implementation is thread-safe assuming the clients (Fulcio, OIDC, Rekor) are
+ * thread-safe
+ */
+public class KeylessSigner2 implements AutoCloseable {
+  /**
+   * The instance of the {@link KeylessSigner2} will try to reuse a previously acquired certificate
+   * if the expiration time on the certificate is more than {@code minSigningCertificateLifetime}
+   * time away. Otherwise, it will make a new request (OIDC, Fulcio) to obtain a new updated
+   * certificate to use for signing. This is a default value for the remaining lifetime of the
+   * signing certificate that is considered good enough.
+   */
+  public static final Duration DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME = Duration.ofMinutes(5);
+
+  private final FulcioClient2 fulcioClient;
+  private final FulcioVerifier2 fulcioVerifier;
+  private final RekorClient2 rekorClient;
+  private final RekorVerifier2 rekorVerifier;
+  private final OidcClients oidcClients;
+  private final Signer signer;
+  private final Duration minSigningCertificateLifetime;
+
+  /** The code signing certificate from Fulcio. */
+  @GuardedBy("lock")
+  private @Nullable SigningCertificate signingCert;
+
+  /**
+   * Representation {@link #signingCert} in PEM bytes format. This is used to avoid serializing the
+   * certificate for each use.
+   */
+  @GuardedBy("lock")
+  private byte @Nullable [] signingCertPemBytes;
+
+  private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+
+  private KeylessSigner2(
+      FulcioClient2 fulcioClient,
+      FulcioVerifier2 fulcioVerifier,
+      RekorClient2 rekorClient,
+      RekorVerifier2 rekorVerifier,
+      OidcClients oidcClients,
+      Signer signer,
+      Duration minSigningCertificateLifetime) {
+    this.fulcioClient = fulcioClient;
+    this.fulcioVerifier = fulcioVerifier;
+    this.rekorClient = rekorClient;
+    this.rekorVerifier = rekorVerifier;
+    this.oidcClients = oidcClients;
+    this.signer = signer;
+    this.minSigningCertificateLifetime = minSigningCertificateLifetime;
+  }
+
+  @Override
+  public void close() {
+    lock.writeLock().lock();
+    try {
+      signingCert = null;
+      signingCertPemBytes = null;
+    } finally {
+      lock.writeLock().unlock();
+    }
+  }
+
+  @CheckReturnValue
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public static class Builder {
+    private SigstoreTufClient sigstoreTufClient;
+    private OidcClients oidcClients;
+    private Signer signer;
+    private Duration minSigningCertificateLifetime = DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME;
+
+    @CanIgnoreReturnValue
+    public Builder sigstoreTufClient(SigstoreTufClient sigstoreTufClient) {
+      this.sigstoreTufClient = sigstoreTufClient;
+      return this;
+    }
+
+    @CanIgnoreReturnValue
+    public Builder oidcClients(OidcClients oidcClients) {
+      this.oidcClients = oidcClients;
+      return this;
+    }
+
+    @CanIgnoreReturnValue
+    public Builder signer(Signer signer) {
+      this.signer = signer;
+      return this;
+    }
+
+    /**
+     * The instance of the {@link KeylessSigner2} will try to reuse a previously acquired
+     * certificate if the expiration time on the certificate is more than {@code
+     * minSigningCertificateLifetime} time away. Otherwise, it will make a new request (OIDC,
+     * Fulcio) to obtain a new updated certificate to use for signing. Default {@code
+     * minSigningCertificateLifetime} is {@link #DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME}".
+     *
+     * @param minSigningCertificateLifetime the minimum lifetime of the signing certificate before
+     *     renewal
+     * @return this builder
+     * @see <a href="https://docs.sigstore.dev/fulcio/overview/">Fulcio certificate validity</a>
+     */
+    @CanIgnoreReturnValue
+    public Builder minSigningCertificateLifetime(Duration minSigningCertificateLifetime) {
+      this.minSigningCertificateLifetime = minSigningCertificateLifetime;
+      return this;
+    }
+
+    @CheckReturnValue
+    public KeylessSigner2 build()
+        throws CertificateException, IOException, NoSuchAlgorithmException, InvalidKeySpecException,
+            InvalidKeyException, InvalidAlgorithmParameterException {
+      Preconditions.checkNotNull(sigstoreTufClient, "sigstoreTufClient");
+      sigstoreTufClient.update();
+      var trustedRoot = sigstoreTufClient.getSigstoreTrustedRoot();
+      var fulcioClient = FulcioClient2.builder().setCertificateAuthority(trustedRoot).build();
+      var fulcioVerifier = FulcioVerifier2.newFulcioVerifier(trustedRoot);
+      var rekorClient = RekorClient2.builder().setTransparencyLog(trustedRoot).build();
+      var rekorVerifier = RekorVerifier2.newRekorVerifier(trustedRoot);
+      return new KeylessSigner2(
+          fulcioClient,
+          fulcioVerifier,
+          rekorClient,
+          rekorVerifier,
+          oidcClients,
+          signer,
+          minSigningCertificateLifetime);
+    }
+
+    /**
+     * Initialize a builder with the sigstore public good instance tuf root and oidc targets with
+     * ecdsa signing.
+     */
+    @CanIgnoreReturnValue
+    public Builder sigstorePublicDefaults() throws IOException, NoSuchAlgorithmException {
+      sigstoreTufClient = SigstoreTufClient.builder().usePublicGoodInstance().build();
+      oidcClients(OidcClients.DEFAULTS);
+      signer(Signers.newEcdsaSigner());
+      minSigningCertificateLifetime(DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME);
+      return this;
+    }
+
+    /**
+     * Initialize a builder with the sigstore staging instance tuf root and oidc targets with ecdsa
+     * signing.
+     */
+    @CanIgnoreReturnValue
+    public Builder sigstoreStagingDefaults() throws IOException, NoSuchAlgorithmException {
+      sigstoreTufClient = SigstoreTufClient.builder().useStagingInstance().build();
+      oidcClients(OidcClients.STAGING_DEFAULTS);
+      signer(Signers.newEcdsaSigner());
+      minSigningCertificateLifetime(DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME);
+      return this;
+    }
+  }
+
+  /**
+   * Sign one or more artifact digests using the keyless signing workflow. The oidc/fulcio dance to
+   * obtain a signing certificate will only occur once. The same ephemeral private key will be used
+   * to sign all artifacts. This method will renew certificates as they expire.
+   *
+   * @param artifactDigests sha256 digests of the artifacts to sign.
+   * @return a list of keyless singing results.
+   */
+  @CheckReturnValue
+  public List<KeylessSignature> sign(List<byte[]> artifactDigests)
+      throws OidcException, NoSuchAlgorithmException, SignatureException, InvalidKeyException,
+          UnsupportedAlgorithmException, CertificateException, IOException,
+          FulcioVerificationException, RekorVerificationException, InterruptedException,
+          RekorParseException, InvalidKeySpecException {
+
+    if (artifactDigests.size() == 0) {
+      throw new IllegalArgumentException("Require one or more digests");
+    }
+
+    var result = ImmutableList.<KeylessSignature>builder();
+
+    for (var artifactDigest : artifactDigests) {
+      var signature = signer.signDigest(artifactDigest);
+
+      // Technically speaking, it is unlikely the certificate will expire between signing artifacts
+      // However, files might be large, and it might take time to talk to Rekor
+      // so we check the certificate expiration here.
+      renewSigningCertificate();
+      SigningCertificate signingCert;
+      byte[] signingCertPemBytes;
+      lock.readLock().lock();
+      try {
+        signingCert = this.signingCert;
+        signingCertPemBytes = this.signingCertPemBytes;
+        if (signingCert == null) {
+          throw new IllegalStateException("Signing certificate is null");
+        }
+      } finally {
+        lock.readLock().unlock();
+      }
+
+      var rekorRequest =
+          HashedRekordRequest.newHashedRekordRequest(
+              artifactDigest, signingCertPemBytes, signature);
+      var rekorResponse = rekorClient.putEntry(rekorRequest);
+      rekorVerifier.verifyEntry(rekorResponse.getEntry());
+
+      result.add(
+          ImmutableKeylessSignature.builder()
+              .digest(artifactDigest)
+              .certPath(signingCert.getCertPath())
+              .signature(signature)
+              .entry(rekorResponse.getEntry())
+              .build());
+    }
+    return result.build();
+  }
+
+  private void renewSigningCertificate()
+      throws InterruptedException, CertificateException, IOException, UnsupportedAlgorithmException,
+          NoSuchAlgorithmException, InvalidKeyException, SignatureException,
+          FulcioVerificationException, OidcException {
+    // Check if the certificate is still valid
+    lock.readLock().lock();
+    try {
+      if (signingCert != null) {
+        @SuppressWarnings("JavaUtilDate")
+        long lifetimeLeft =
+            signingCert.getLeafCertificate().getNotAfter().getTime() - System.currentTimeMillis();
+        if (lifetimeLeft > minSigningCertificateLifetime.toMillis()) {
+          // The current certificate is fine, reuse it
+          return;
+        }
+      }
+    } finally {
+      lock.readLock().unlock();
+    }
+
+    // Renew Fulcio certificate
+    lock.writeLock().lock();
+    try {
+      signingCert = null;
+      signingCertPemBytes = null;
+      OidcToken tokenInfo = oidcClients.getIDToken();
+      SigningCertificate signingCert =
+          fulcioClient.signingCertificate(
+              CertificateRequest.newCertificateRequest(
+                  signer.getPublicKey(),
+                  tokenInfo.getIdToken(),
+                  signer.sign(
+                      tokenInfo.getSubjectAlternativeName().getBytes(StandardCharsets.UTF_8))));
+      fulcioVerifier.verifyCertChain(signingCert);
+      // TODO: this signing workflow mandates SCTs, but fulcio itself doesn't, figure out a way to
+      // allow that to be known
+      fulcioVerifier.verifySct(signingCert);
+      this.signingCert = signingCert;
+      signingCertPemBytes = Certificates.toPemBytes(signingCert.getLeafCertificate());
+    } finally {
+      lock.writeLock().unlock();
+    }
+  }
+
+  /**
+   * Convenience wrapper around {@link #sign(List)} to sign a single digest
+   *
+   * @param artifactDigest sha256 digest of the artifact to sign.
+   * @return a keyless singing results.
+   */
+  @CheckReturnValue
+  public KeylessSignature sign(byte[] artifactDigest)
+      throws FulcioVerificationException, RekorVerificationException, UnsupportedAlgorithmException,
+          CertificateException, NoSuchAlgorithmException, SignatureException, IOException,
+          OidcException, InvalidKeyException, InterruptedException, RekorParseException,
+          InvalidKeySpecException {
+    return sign(List.of(artifactDigest)).get(0);
+  }
+
+  /**
+   * Convenience wrapper around {@link #sign(List)} to accept files instead of digests
+   *
+   * @param artifacts list of the artifacts to sign.
+   * @return a map of artifacts and their keyless singing results.
+   */
+  @CheckReturnValue
+  public Map<Path, KeylessSignature> signFiles(List<Path> artifacts)
+      throws FulcioVerificationException, RekorVerificationException, UnsupportedAlgorithmException,
+          CertificateException, NoSuchAlgorithmException, SignatureException, IOException,
+          OidcException, InvalidKeyException, InterruptedException, RekorParseException,
+          InvalidKeySpecException {
+    if (artifacts.size() == 0) {
+      throw new IllegalArgumentException("Require one or more paths");
+    }
+    var digests = new ArrayList<byte[]>(artifacts.size());
+    for (var artifact : artifacts) {
+      var artifactByteSource = com.google.common.io.Files.asByteSource(artifact.toFile());
+      digests.add(artifactByteSource.hash(Hashing.sha256()).asBytes());
+    }
+    var signingResult = sign(digests);
+    var result = ImmutableMap.<Path, KeylessSignature>builder();
+    for (int i = 0; i < artifacts.size(); i++) {
+      result.put(artifacts.get(i), signingResult.get(i));
+    }
+    return result.build();
+  }
+
+  /**
+   * Convenience wrapper around {@link #sign(List)} to accept a file instead of digests
+   *
+   * @param artifact the artifacts to sign.
+   * @return a keyless singing results.
+   */
+  @CheckReturnValue
+  public KeylessSignature signFile(Path artifact)
+      throws FulcioVerificationException, RekorVerificationException, UnsupportedAlgorithmException,
+          CertificateException, NoSuchAlgorithmException, SignatureException, IOException,
+          OidcException, InvalidKeyException, InterruptedException, RekorParseException,
+          InvalidKeySpecException {
+    return signFiles(List.of(artifact)).get(artifact);
+  }
+}