Fix method hierarchy of addBindingSignature()

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/OpenPgpKeyGenerator.kt

@@ -12,7 +12,6 @@ import org.bouncycastle.extensions.plusCertification
 import org.bouncycastle.openpgp.PGPKeyPair
 import org.bouncycastle.openpgp.PGPSecretKey
 import org.bouncycastle.openpgp.PGPSecretKeyRing
-import org.bouncycastle.openpgp.PGPSignature
 import org.bouncycastle.openpgp.PGPUserAttributeSubpacketVector
 import org.bouncycastle.openpgp.PGPUserAttributeSubpacketVectorGenerator
 import org.bouncycastle.util.io.Streams
@@ -926,11 +925,22 @@ internal constructor(
      * @param bindingTime creation time of the binding signature
      * @return modified subkey pair
      */
-    abstract fun addBindingSignature(
+    fun addBindingSignature(
         subpacketsCallback: SelfSignatureSubpackets.Callback = SelfSignatureSubpackets.nop(),
         hashAlgorithm: HashAlgorithm =
             builder.policy.certificationSignatureHashAlgorithmPolicy.defaultHashAlgorithm,
         bindingTime: Date = subkey.publicKey.creationTime
+    ): PGPKeyPair {
+        builder.sanitizeHashAlgorithm(hashAlgorithm)
+        builder.sanitizeBindingTime(bindingTime, subkey)
+
+        return doAddBindingSignature(subpacketsCallback, hashAlgorithm, bindingTime)
+    }
+
+    abstract fun doAddBindingSignature(
+        subpacketsCallback: SelfSignatureSubpackets.Callback,
+        hashAlgorithm: HashAlgorithm,
+        bindingTime: Date
     ): PGPKeyPair
 }
 
@@ -945,46 +955,15 @@ class ApplyToSubkeyV4
 internal constructor(primaryKey: PGPKeyPair, subkey: PGPKeyPair, builder: DefineSubkeys<*>) :
     ApplyToSubkey(primaryKey, subkey, builder) {
 
-    override fun addBindingSignature(
+    override fun doAddBindingSignature(
         subpacketsCallback: SelfSignatureSubpackets.Callback,
         hashAlgorithm: HashAlgorithm,
         bindingTime: Date
     ): PGPKeyPair {
-        builder.sanitizeHashAlgorithm(hashAlgorithm)
+        val sigBuilder = SubkeyBindingSignatureBuilder(primaryKey, hashAlgorithm)
-        builder.sanitizeBindingTime(bindingTime, subkey)
+        sigBuilder.applyCallback(
-
-        val sig =
-            buildBindingSignature(
-                primaryKey, subkey, hashAlgorithm, bindingTime, subpacketsCallback)
-
-        subkey = subkey.plusCertification(sig)
-        return subkey
-    }
-
-    /**
-     * Generate a version 4 binding signature that binds the [subkey] to the [primaryKey].
-     *
-     * @param primaryKey primary key pair
-     * @param subkey subkey pair
-     * @param hashAlgorithm hash algorithm to be used during signature calculation
-     * @param bindingTime creation time of the subkey
-     * @param subpacketsCallback callback to modify the subpackets of the binding signature
-     * @return subkey binding signature
-     */
-    private fun buildBindingSignature(
-        primaryKey: PGPKeyPair,
-        subkey: PGPKeyPair,
-        hashAlgorithm: HashAlgorithm,
-        bindingTime: Date,
-        subpacketsCallback: SelfSignatureSubpackets.Callback
-    ): PGPSignature {
-        return SubkeyBindingSignatureBuilder(primaryKey, hashAlgorithm)
-            .applyCallback(
             subpacketsCallback
-                    .then(
+                .then(SelfSignatureSubpackets.applyHashed { setSignatureCreationTime(bindingTime) })
-                        SelfSignatureSubpackets.applyHashed {
-                            setSignatureCreationTime(bindingTime)
-                        })
                 .then(
                     SelfSignatureSubpackets.applyHashed {
                         if (isSigningCapable(getKeyFlags())) {
@@ -993,7 +972,10 @@ internal constructor(primaryKey: PGPKeyPair, subkey: PGPKeyPair, builder: Define
                                     .build(primaryKey))
                         }
                     }))
-            .build(subkey)
+        val sig = sigBuilder.build(subkey)
+
+        subkey = subkey.plusCertification(sig)
+        return subkey
     }
 
     /**