From 6a11e39d76cb6cc1a992f078be57c5e7b08f6ab6 Mon Sep 17 00:00:00 2001
From: Paul Schaub <vanitasvitae@fsfe.org>
Date: Sun, 1 Aug 2021 15:53:51 +0200
Subject: [PATCH] Add issuer-fingerprint to message signatures

---
 .../encryption_signing/SigningOptions.java         | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SigningOptions.java b/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SigningOptions.java
index 8f19ad4b..ec82cba0 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SigningOptions.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/encryption_signing/SigningOptions.java
@@ -29,6 +29,7 @@ import org.bouncycastle.openpgp.PGPSecretKey;
 import org.bouncycastle.openpgp.PGPSecretKeyRing;
 import org.bouncycastle.openpgp.PGPSecretKeyRingCollection;
 import org.bouncycastle.openpgp.PGPSignatureGenerator;
+import org.bouncycastle.openpgp.PGPSignatureSubpacketGenerator;
 import org.bouncycastle.openpgp.operator.PGPContentSignerBuilder;
 import org.pgpainless.PGPainless;
 import org.pgpainless.algorithm.DocumentSignatureType;
@@ -266,7 +267,7 @@ public final class SigningOptions {
                                   boolean detached)
             throws PGPException {
         SubkeyIdentifier signingKeyIdentifier = new SubkeyIdentifier(secretKey, signingSubkey.getKeyID());
-        PGPSignatureGenerator generator = createSignatureGenerator(signingSubkey, hashAlgorithm, signatureType);
+        PGPSignatureGenerator generator = createSignatureGenerator(secretKey.getSecretKey(signingSubkey.getKeyID()), signingSubkey, hashAlgorithm, signatureType);
         SigningMethod signingMethod = detached ? SigningMethod.detachedSignature(generator) : SigningMethod.inlineSignature(generator);
         signingMethods.put(signingKeyIdentifier, signingMethod);
     }
@@ -302,7 +303,8 @@ public final class SigningOptions {
         return algorithm;
     }
 
-    private PGPSignatureGenerator createSignatureGenerator(PGPPrivateKey privateKey,
+    private PGPSignatureGenerator createSignatureGenerator(PGPSecretKey secretKey,
+                                                           PGPPrivateKey privateKey,
                                                            HashAlgorithm hashAlgorithm,
                                                            DocumentSignatureType signatureType)
             throws PGPException {
@@ -310,11 +312,19 @@ public final class SigningOptions {
         PGPContentSignerBuilder signerBuilder = ImplementationFactory.getInstance()
                 .getPGPContentSignerBuilder(publicKeyAlgorithm, hashAlgorithm.getAlgorithmId());
         PGPSignatureGenerator signatureGenerator = new PGPSignatureGenerator(signerBuilder);
+        signatureGenerator.setUnhashedSubpackets(unhashedSubpackets(secretKey).generate());
         signatureGenerator.init(signatureType.getSignatureType().getCode(), privateKey);
 
         return signatureGenerator;
     }
 
+    private PGPSignatureSubpacketGenerator unhashedSubpackets(PGPSecretKey key) {
+        PGPSignatureSubpacketGenerator generator = new PGPSignatureSubpacketGenerator();
+        generator.setIssuerKeyID(false, key.getKeyID());
+        generator.setIssuerFingerprint(false, key);
+        return generator;
+    }
+
     /**
      * Return a map of key-ids and signing methods.
      * For internal use.