Merge pull request #847 from sigstore/add_key_parsers_to_tuf_package

Add tuf specific key/signature handlers

fuzzing/src/main/java/fuzzing/TufVerifierFuzzer.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2023 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 fuzzing;
+
+import com.code_intelligence.jazzer.api.FuzzedDataProvider;
+import dev.sigstore.tuf.encryption.Verifiers;
+import dev.sigstore.tuf.model.ImmutableKey;
+import dev.sigstore.tuf.model.Key;
+import java.io.IOException;
+import java.security.InvalidKeyException;
+import java.util.Map;
+
+public class TufVerifierFuzzer {
+  public static void fuzzerTestOneInput(FuzzedDataProvider data) {
+    try {
+      String keyType = data.consumeString(10);
+      String scheme = data.consumeString(20);
+      String keyData = data.consumeRemainingAsString();
+
+      Key key =
+          ImmutableKey.builder()
+              .keyType(keyType)
+              .keyVal(Map.of("public", keyData))
+              .scheme(scheme)
+              .build();
+
+      Verifiers.newVerifier(key);
+    } catch (IOException | InvalidKeyException e) {
+      // known exceptions
+    }
+  }
+}

sigstore-java/src/main/java/dev/sigstore/tuf/encryption/EcdsaVerifier.java

@@ -0,0 +1,41 @@
+/*
+ * 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.tuf.encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+
+/** ECDSA verifier, instantiated in {@link Verifiers}. */
+class EcdsaVerifier implements Verifier {
+
+  private final PublicKey publicKey;
+
+  EcdsaVerifier(PublicKey publicKey) {
+    this.publicKey = publicKey;
+  }
+
+  @Override
+  public boolean verify(byte[] artifact, byte[] signature)
+      throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
+    var verifier = Signature.getInstance("SHA256withECDSA");
+    verifier.initVerify(publicKey);
+    verifier.update(artifact);
+    return verifier.verify(signature);
+  }
+}

sigstore-java/src/main/java/dev/sigstore/tuf/encryption/Ed25519Verifier.java

@@ -0,0 +1,42 @@
+/*
+ * 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.tuf.encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+
+/** Ed25519 verifier, instantiated by {@link Verifiers}. */
+class Ed25519Verifier implements Verifier {
+
+  private final PublicKey publicKey;
+
+  Ed25519Verifier(PublicKey publicKey) {
+    this.publicKey = publicKey;
+  }
+
+  /** EdDSA verifiers hash implicitly for ed25519 keys. */
+  @Override
+  public boolean verify(byte[] artifact, byte[] signature)
+      throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
+    var verifier = Signature.getInstance("Ed25519");
+    verifier.initVerify(publicKey);
+    verifier.update(artifact);
+    return verifier.verify(signature);
+  }
+}

sigstore-java/src/main/java/dev/sigstore/tuf/encryption/RsaPssVerifier.java

@@ -0,0 +1,41 @@
+/*
+ * 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.tuf.encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+
+/** RSA verifier using PSS and MGF1, instantiated by {@link Verifiers}. */
+class RsaPssVerifier implements Verifier {
+
+  private final PublicKey publicKey;
+
+  RsaPssVerifier(PublicKey publicKey) {
+    this.publicKey = publicKey;
+  }
+
+  @Override
+  public boolean verify(byte[] artifact, byte[] signature)
+      throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
+    var verifier = Signature.getInstance("SHA256withRSAandMGF1");
+    verifier.initVerify(publicKey);
+    verifier.update(artifact);
+    return verifier.verify(signature);
+  }
+}

sigstore-java/src/main/java/dev/sigstore/tuf/encryption/Verifier.java

@@ -0,0 +1,35 @@
+/*
+ * 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.tuf.encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SignatureException;
+
+/** A verifier interface specifying verification for a raw artifact (no hashing). */
+public interface Verifier {
+
+  /**
+   * Verify an artifact. Implementations may hash the artifact with sha256 before verifying unless
+   * they have an implicit hashing algorithm.
+   *
+   * @param artifact the artifact that was signed
+   * @param signature the signature associated with the artifact
+   * @return true if the signature is valid, false otherwise
+   */
+  boolean verify(byte[] artifact, byte[] signature)
+      throws NoSuchAlgorithmException, InvalidKeyException, SignatureException;
+}

sigstore-java/src/main/java/dev/sigstore/tuf/encryption/Verifiers.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright 2024 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.tuf.encryption;
+
+import dev.sigstore.tuf.model.Key;
+import java.io.IOException;
+import java.io.StringReader;
+import java.security.InvalidKeyException;
+import java.security.PublicKey;
+import java.security.Security;
+import org.bouncycastle.asn1.edec.EdECObjectIdentifiers;
+import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
+import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
+import org.bouncycastle.crypto.params.ECKeyParameters;
+import org.bouncycastle.crypto.params.RSAKeyParameters;
+import org.bouncycastle.crypto.util.PublicKeyFactory;
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
+import org.bouncycastle.openssl.PEMParser;
+import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
+import org.bouncycastle.util.encoders.DecoderException;
+import org.bouncycastle.util.encoders.Hex;
+
+public class Verifiers {
+
+  static {
+    Security.addProvider(new BouncyCastleProvider());
+  }
+
+  @FunctionalInterface
+  public interface Supplier {
+    Verifier newVerifier(Key key) throws IOException, InvalidKeyException;
+  }
+
+  public static Verifier newVerifier(Key key) throws IOException, InvalidKeyException {
+
+    PublicKey publicKey = parsePublicKey(key);
+    if (key.getKeyType().equals("rsa") && key.getScheme().equals("rsassa-pss-sha256")) {
+      return new RsaPssVerifier(publicKey);
+    }
+    if (isEcdsaKey(key) && key.getScheme().equals("ecdsa-sha2-nistp256")) {
+      return new EcdsaVerifier(publicKey);
+    }
+    if (key.getKeyType().equals("ed25519") && key.getScheme().equals("ed25519")) {
+      return new Ed25519Verifier(publicKey);
+    }
+    throw new InvalidKeyException(
+        "Unsupported tuf key type and scheme combination: "
+            + key.getKeyType()
+            + "/"
+            + key.getScheme());
+  }
+
+  private static PublicKey parsePublicKey(Key key) throws IOException, InvalidKeyException {
+    var keyType = key.getKeyType();
+    if (keyType.equals("rsa") || isEcdsaKey(key)) {
+      try (PEMParser pemParser = new PEMParser(new StringReader(key.getKeyVal().get("public")))) {
+        var keyObj = pemParser.readObject(); // throws DecoderException
+        if (keyObj == null) {
+          throw new InvalidKeyException(
+              "tuf " + key.getKeyType() + " keys must be a single PEM encoded section");
+        }
+        if (keyObj instanceof SubjectPublicKeyInfo) {
+          var keyInfo = PublicKeyFactory.createKey((SubjectPublicKeyInfo) keyObj);
+          if ((keyType.equals("rsa") && keyInfo instanceof RSAKeyParameters)
+              || (isEcdsaKey(key) && keyInfo instanceof ECKeyParameters)) {
+            JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
+            return converter.getPublicKey((SubjectPublicKeyInfo) keyObj);
+          }
+        }
+        throw new InvalidKeyException(
+            "Could not parse PEM section into " + keyType + " public key");
+      } catch (DecoderException e) {
+        throw new InvalidKeyException("Could not parse PEM section in " + keyType + " public key");
+      }
+    }
+    // tuf allows raw keys only for ed25519 (non PEM):
+    // https://github.com/theupdateframework/specification/blob/c51875f445d8a57efca9dadfbd5dbdece06d87e6/tuf-spec.md#key-objects--file-formats-keys
+    else if (keyType.equals("ed25519")) {
+      byte[] keyContents;
+      try {
+        keyContents = Hex.decode(key.getKeyVal().get("public"));
+      } catch (DecoderException e) {
+        throw new InvalidKeyException("Could not parse hex encoded ed25519 public key");
+      }
+      var params =
+          new SubjectPublicKeyInfo(
+              new AlgorithmIdentifier(EdECObjectIdentifiers.id_Ed25519), keyContents);
+      JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
+      return converter.getPublicKey(params);
+    } else {
+      throw new InvalidKeyException("Unsupported tuf key type" + key.getKeyType());
+    }
+  }
+
+  // this is a hack to handle keytypes of ecdsa-sha2-nistp256
+  // context: https://github.com/awslabs/tough/issues/754
+  private static boolean isEcdsaKey(Key key) {
+    return key.getKeyType().equals("ecdsa-sha2-nistp256") || key.getKeyType().equals("ecdsa");
+  }
+}

sigstore-java/src/test/java/dev/sigstore/tuf/encryption/EcdsaVerifierTest.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2024 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.tuf.encryption;
+
+import java.nio.charset.StandardCharsets;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.Security;
+import java.security.Signature;
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class EcdsaVerifierTest {
+
+  private static final byte[] CONTENT = "abcdef".getBytes(StandardCharsets.UTF_8);
+
+  @Test
+  public void testVerify_ECDSA() throws Exception {
+    Security.addProvider(new BouncyCastleProvider());
+
+    var keyPair = genKeyPair();
+    var signature = genSignature(keyPair);
+    var verifier = new EcdsaVerifier(keyPair.getPublic());
+    Assertions.assertTrue(verifier.verify(CONTENT, signature));
+  }
+
+  private KeyPair genKeyPair() throws Exception {
+    KeyPairGenerator keyGen = KeyPairGenerator.getInstance("ECDSA");
+    keyGen.initialize(256);
+    return keyGen.generateKeyPair();
+  }
+
+  private byte[] genSignature(KeyPair keyPair) throws Exception {
+    Signature signature = Signature.getInstance("SHA256withECDSA");
+    signature.initSign(keyPair.getPrivate());
+    signature.update(CONTENT);
+    return signature.sign();
+  }
+}