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Add support for creating and verifying DSSE attestations #1084

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167 changes: 167 additions & 0 deletions sigstore-java/src/main/java/dev/sigstore/KeylessSigner.java
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Expand Up @@ -22,11 +22,15 @@
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.CheckReturnValue;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import com.google.gson.JsonSyntaxException;
import com.google.protobuf.ByteString;
import dev.sigstore.bundle.Bundle;
import dev.sigstore.bundle.Bundle.MessageSignature;
import dev.sigstore.bundle.ImmutableBundle;
import dev.sigstore.bundle.ImmutableDsseEnvelope;
import dev.sigstore.bundle.ImmutableSignature;
import dev.sigstore.bundle.ImmutableTimestamp;
import dev.sigstore.dsse.InTotoPayload;
import dev.sigstore.encryption.certificates.Certificates;
import dev.sigstore.encryption.signers.Signer;
import dev.sigstore.encryption.signers.Signers;
Expand All @@ -42,6 +46,7 @@
import dev.sigstore.oidc.client.OidcTokenMatcher;
import dev.sigstore.proto.ProtoMutators;
import dev.sigstore.proto.common.v1.X509Certificate;
import dev.sigstore.proto.rekor.v2.DSSERequestV002;
import dev.sigstore.proto.rekor.v2.HashedRekordRequestV002;
import dev.sigstore.proto.rekor.v2.Signature;
import dev.sigstore.proto.rekor.v2.Verifier;
Expand All @@ -65,6 +70,7 @@
import dev.sigstore.trustroot.Service;
import dev.sigstore.trustroot.SigstoreConfigurationException;
import dev.sigstore.tuf.SigstoreTufClient;
import io.intoto.EnvelopeOuterClass;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
Expand Down Expand Up @@ -102,6 +108,8 @@ public class KeylessSigner implements AutoCloseable {
*/
public static final Duration DEFAULT_MIN_SIGNING_CERTIFICATE_LIFETIME = Duration.ofMinutes(5);

public static final String DEFAULT_INTOTO_PAYLOAD_TYPE = "https://in-toto.io/Statement/v1";

private final FulcioClient fulcioClient;
private final FulcioVerifier fulcioVerifier;
private final RekorClient rekorClient;
Expand Down Expand Up @@ -671,4 +679,163 @@ public Map<Path, Bundle> signFiles(List<Path> artifacts) throws KeylessSignerExc
public Bundle signFile(Path artifact) throws KeylessSignerException {
return signFiles(List.of(artifact)).get(artifact);
}

public Bundle attest(String payload) throws KeylessSignerException {
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@loosebazooka loosebazooka Nov 4, 2025

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Attest seems to be pretty similar to sign, can we refactor out some of the common parts?

It looks like it might a little complicated, but I'd likk to see what it could look like?

if (rekorV2Client != null) { // Using Rekor v2 and a TSA
Preconditions.checkNotNull(
timestampClient, "Timestamp client must be configured for Rekor v2");
Preconditions.checkNotNull(
timestampVerifier, "Timestamp verifier must be configured for Rekor v2");
} else {
throw new IllegalStateException("No rekor v2 client was configured.");
}

if (payload == null || payload.isEmpty()) {
throw new IllegalArgumentException("Payload must be non-empty");
}

InTotoPayload inTotoPayload;
try {
inTotoPayload = InTotoPayload.from(payload);
} catch (JsonSyntaxException jse) {
throw new IllegalArgumentException("Payload is not a valid in-toto statement");
}

if (!inTotoPayload.getType().equals(DEFAULT_INTOTO_PAYLOAD_TYPE)) {
throw new IllegalArgumentException(
"Payload must be of type \""
+ DEFAULT_INTOTO_PAYLOAD_TYPE
+ "\" but was \""
+ inTotoPayload.getType()
+ "\"");
}

if (inTotoPayload.getSubject() == null || inTotoPayload.getSubject().isEmpty()) {
throw new IllegalArgumentException("Payload must contain at least one subject");
}

for (var subject : inTotoPayload.getSubject()) {
if (subject.getName() != null && !subject.getName().isEmpty()) {
continue;
}
throw new IllegalArgumentException("Payload must contain at least one non-empty subject");
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@loosebazooka loosebazooka Oct 29, 2025

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Maybe, this error message could be more descriptive?

Payload must contain valid subjects?

}

// 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.
try {
renewSigningCertificate();
} catch (FulcioVerificationException
| UnsupportedAlgorithmException
| OidcException
| IOException
| InterruptedException
| InvalidKeyException
| NoSuchAlgorithmException
| SignatureException
| CertificateException ex) {
throw new KeylessSignerException("Failed to obtain signing certificate", ex);
}

CertPath signingCert;
byte[] encodedCert;
lock.readLock().lock();
try {
signingCert = this.signingCert;
encodedCert = this.encodedCert;
if (signingCert == null) {
throw new IllegalStateException("Signing certificate is null");
}
} finally {
lock.readLock().unlock();
}

var bundleBuilder = ImmutableBundle.builder().certPath(signingCert);

var dsse =
ImmutableDsseEnvelope.builder()
.payload(payload.getBytes(StandardCharsets.UTF_8))
.payloadType("application/vnd.in-toto+json")
.build();

var pae = dsse.getPAE();

Bundle.DsseEnvelope dsseSigned;
try {
var sig = signer.sign(pae);
dsseSigned =
ImmutableDsseEnvelope.builder()
.from(dsse)
.addSignatures(ImmutableSignature.builder().sig(sig).build())
.build();
} catch (NoSuchAlgorithmException | SignatureException | InvalidKeyException ex) {
throw new KeylessSignerException("Failed to sign artifact", ex);
}

var verifier =
Verifier.newBuilder()
.setX509Certificate(
X509Certificate.newBuilder().setRawBytes(ByteString.copyFrom(encodedCert)).build())
.setKeyDetails(ProtoMutators.toPublicKeyDetails(signingAlgorithm))
.build();

var dsseRequest =
DSSERequestV002.newBuilder()
.setEnvelope(
EnvelopeOuterClass.Envelope.newBuilder()
.setPayload(ByteString.copyFrom(dsseSigned.getPayload()))
.setPayloadType(dsseSigned.getPayloadType())
.addSignatures(
EnvelopeOuterClass.Signature.newBuilder()
.setSig(ByteString.copyFrom(dsseSigned.getSignature())))
.build())
.addVerifiers(verifier)
.build();

var signatureDigest = Hashing.sha256().hashBytes(dsseSigned.getSignature()).asBytes();

var tsReq =
ImmutableTimestampRequest.builder()
.hashAlgorithm(dev.sigstore.timestamp.client.HashAlgorithm.SHA256)
.hash(signatureDigest)
.build();

TimestampResponse tsResp;
try {
tsResp = timestampClient.timestamp(tsReq);
} catch (TimestampException ex) {
throw new KeylessSignerException("Failed to generate timestamp", ex);
}

try {
timestampVerifier.verify(tsResp, dsseSigned.getSignature());
} catch (TimestampVerificationException ex) {
throw new KeylessSignerException("Returned timestamp was invalid", ex);
}

Bundle.Timestamp timestamp =
ImmutableTimestamp.builder().rfc3161Timestamp(tsResp.getEncoded()).build();

bundleBuilder.addTimestamps(timestamp);

RekorEntry entry;
try {
entry = rekorV2Client.putEntry(dsseRequest);
} catch (IOException | RekorParseException ex) {
throw new KeylessSignerException("Failed to put entry in rekor", ex);
}

try {
rekorVerifier.verifyEntry(entry);
} catch (RekorVerificationException ex) {
throw new KeylessSignerException("Failed to validate rekor entry after signing", ex);
}

bundleBuilder.dsseEnvelope(dsseSigned);

bundleBuilder.addEntries(entry);

return bundleBuilder.build();
}
}
17 changes: 17 additions & 0 deletions sigstore-java/src/main/java/dev/sigstore/bundle/Bundle.java
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Expand Up @@ -25,6 +25,7 @@
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.cert.CertPath;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import org.immutables.gson.Gson;
Expand Down Expand Up @@ -149,6 +150,7 @@ public interface DsseEnvelope {
* content.
*/
@Gson.Ignore
@Value.Auxiliary
@Derived
default byte[] getPAE() {
return ("DSSEv1 "
Expand All @@ -162,6 +164,21 @@ default byte[] getPAE() {
.getBytes(StandardCharsets.UTF_8);
}

@Override
int hashCode();

@Override
boolean equals(Object obj);

@Value.Check
default void check() {
// This is a workaround for immutables not using Arrays.equals for derived byte[]
// see: https://github.com/immutables/immutables/issues/1610
if (!Arrays.equals(getPAE(), getPAE())) {
throw new IllegalStateException("Should be unreachable");
}
}
Comment on lines +167 to +180
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@loosebazooka loosebazooka Oct 29, 2025

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is any of this extra stuff necessary, seems like @Auxilary would be enough?


@Lazy
@Gson.Ignore
default String getPayloadAsString() {
Expand Down
60 changes: 42 additions & 18 deletions sigstore-java/src/main/java/dev/sigstore/bundle/BundleWriter.java
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Expand Up @@ -33,6 +33,7 @@
import dev.sigstore.proto.rekor.v1.KindVersion;
import dev.sigstore.proto.rekor.v1.TransparencyLogEntry;
import dev.sigstore.rekor.client.RekorEntry;
import io.intoto.EnvelopeOuterClass.Envelope;
import java.security.cert.CertificateEncodingException;
import java.util.Base64;
import java.util.List;
Expand Down Expand Up @@ -78,28 +79,51 @@ static String writeBundle(Bundle signingResult) {
* @return Sigstore Bundle in protobuf builder format
*/
static dev.sigstore.proto.bundle.v1.Bundle.Builder createBundleBuilder(Bundle bundle) {
if (bundle.getMessageSignature().isEmpty()) {
throw new IllegalStateException("can only serialize bundles with message signatures");
if (bundle.getMessageSignature().isEmpty() && bundle.getDsseEnvelope().isEmpty()) {
throw new IllegalStateException("Either message signature or DSSE envelope must be present");
}
var messageSignature = bundle.getMessageSignature().get();
if (messageSignature.getMessageDigest().isEmpty()) {
if (bundle.getMessageSignature().isPresent() && bundle.getDsseEnvelope().isPresent()) {
throw new IllegalStateException(
"Only one of message signature or DSSE envelope must be present");
}
if (bundle.getMessageSignature().isPresent()
&& bundle.getMessageSignature().get().getMessageDigest().isEmpty()) {
throw new IllegalStateException(
"keyless signature must have artifact digest when serializing to bundle");
}
return dev.sigstore.proto.bundle.v1.Bundle.newBuilder()
.setMediaType(bundle.getMediaType())
.setVerificationMaterial(buildVerificationMaterial(bundle))
.setMessageSignature(
MessageSignature.newBuilder()
.setMessageDigest(
HashOutput.newBuilder()
.setAlgorithm(
ProtoMutators.toProtoHashAlgorithm(
messageSignature.getMessageDigest().get().getHashAlgorithm()))
.setDigest(
ByteString.copyFrom(
messageSignature.getMessageDigest().get().getDigest())))
.setSignature(ByteString.copyFrom(messageSignature.getSignature())));
dev.sigstore.proto.bundle.v1.Bundle.Builder builder =
dev.sigstore.proto.bundle.v1.Bundle.newBuilder()
.setMediaType(bundle.getMediaType())
.setVerificationMaterial(buildVerificationMaterial(bundle));
if (bundle.getMessageSignature().isPresent()) {
var messageSignature = bundle.getMessageSignature().get();
builder.setMessageSignature(
MessageSignature.newBuilder()
.setMessageDigest(
HashOutput.newBuilder()
.setAlgorithm(
ProtoMutators.toProtoHashAlgorithm(
messageSignature.getMessageDigest().get().getHashAlgorithm()))
.setDigest(
ByteString.copyFrom(
messageSignature.getMessageDigest().get().getDigest())))
.setSignature(ByteString.copyFrom(messageSignature.getSignature())));
}
if (bundle.getDsseEnvelope().isPresent()) {
var dsseEnvelope = bundle.getDsseEnvelope().get();
var envelopeBuilder =
Envelope.newBuilder()
.setPayload(ByteString.copyFrom(dsseEnvelope.getPayload()))
.setPayloadType(dsseEnvelope.getPayloadType());
for (var sig : dsseEnvelope.getSignatures()) {
envelopeBuilder.addSignatures(
io.intoto.EnvelopeOuterClass.Signature.newBuilder()
.setSig(ByteString.copyFrom(sig.getSig()))
.build());
}
builder.setDsseEnvelope(envelopeBuilder.build());
}
return builder;
}

private static VerificationMaterial.Builder buildVerificationMaterial(Bundle bundle) {
Expand Down
6 changes: 5 additions & 1 deletion sigstore-java/src/main/java/dev/sigstore/dsse/InTotoPayload.java
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Expand Up @@ -51,7 +51,11 @@ interface Subject {
Map<String, String> getDigest();
}

static InTotoPayload from(String payload) {
return GSON.get().fromJson(payload, InTotoPayload.class);
}

static InTotoPayload from(DsseEnvelope dsseEnvelope) {
return GSON.get().fromJson(dsseEnvelope.getPayloadAsString(), InTotoPayload.class);
return from(dsseEnvelope.getPayloadAsString());
}
}
9 changes: 9 additions & 0 deletions sigstore-java/src/main/java/dev/sigstore/rekor/v2/client/RekorV2Client.java
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Expand Up @@ -15,6 +15,7 @@
*/
package dev.sigstore.rekor.v2.client;

import dev.sigstore.proto.rekor.v2.DSSERequestV002;
import dev.sigstore.proto.rekor.v2.HashedRekordRequestV002;
import dev.sigstore.rekor.client.RekorEntry;
import dev.sigstore.rekor.client.RekorParseException;
Expand All @@ -30,4 +31,12 @@ public interface RekorV2Client {
*/
RekorEntry putEntry(HashedRekordRequestV002 hashedRekordRequest)
throws IOException, RekorParseException;

/**
* Put a new dsse entry on the Rekor log.
*
* @param dsseRequest the request to send to rekor
* @return a {@link RekorEntry} with information about the log entry
*/
RekorEntry putEntry(DSSERequestV002 dsseRequest) throws IOException, RekorParseException;
}
19 changes: 13 additions & 6 deletions sigstore-java/src/main/java/dev/sigstore/rekor/v2/client/RekorV2ClientHttp.java
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Expand Up @@ -25,6 +25,7 @@
import dev.sigstore.http.HttpParams;
import dev.sigstore.http.ImmutableHttpParams;
import dev.sigstore.proto.rekor.v2.CreateEntryRequest;
import dev.sigstore.proto.rekor.v2.DSSERequestV002;
import dev.sigstore.proto.rekor.v2.HashedRekordRequestV002;
import dev.sigstore.rekor.client.RekorEntry;
import dev.sigstore.rekor.client.RekorParseException;
Expand Down Expand Up @@ -77,20 +78,26 @@ public RekorV2ClientHttp build() {
@Override
public RekorEntry putEntry(HashedRekordRequestV002 hashedRekordRequest)
throws IOException, RekorParseException {
return putEntry(
CreateEntryRequest.newBuilder().setHashedRekordRequestV002(hashedRekordRequest).build());
}

@Override
public RekorEntry putEntry(DSSERequestV002 dsseRequest) throws IOException, RekorParseException {
return putEntry(CreateEntryRequest.newBuilder().setDsseRequestV002(dsseRequest).build());
}

private RekorEntry putEntry(CreateEntryRequest request) throws IOException, RekorParseException {
URI rekorPutEndpoint = uri.resolve(REKOR_ENTRIES_PATH);

String jsonPayload =
JsonFormat.printer()
.print(
CreateEntryRequest.newBuilder()
.setHashedRekordRequestV002(hashedRekordRequest)
.build());
String jsonPayload = JsonFormat.printer().print(request);

HttpRequest req =
HttpClients.newRequestFactory(httpParams)
.buildPostRequest(
new GenericUrl(rekorPutEndpoint),
ByteArrayContent.fromString("application/json", jsonPayload));

req.getHeaders().set("Accept", "application/json");
req.getHeaders().set("Content-Type", "application/json");

Expand Down
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