Separate Signature verification methods out of SignatureValidator into SignatureVerifier

pgpainless-core/src/main/java/org/pgpainless/key/KeyRingValidator.java

@@ -33,7 +33,7 @@ import org.pgpainless.exception.SignatureValidationException;
 import org.pgpainless.implementation.ImplementationFactory;
 import org.pgpainless.policy.Policy;
 import org.pgpainless.signature.SignatureCreationDateComparator;
-import org.pgpainless.signature.SignatureValidator;
+import org.pgpainless.signature.SignatureVerifier;
 import org.pgpainless.util.CollectionUtils;
 
 public final class KeyRingValidator {
@@ -77,7 +77,7 @@ public final class KeyRingValidator {
         Collections.sort(directKeyCertifications, new SignatureCreationDateComparator(SignatureCreationDateComparator.Order.NEW_TO_OLD));
         for (PGPSignature signature : directKeyCertifications) {
             try {
-                if (SignatureValidator.verifyDirectKeySignature(signature, blank, policy, validationDate)) {
+                if (SignatureVerifier.verifyDirectKeySignature(signature, blank, policy, validationDate)) {
                     blank = PGPPublicKey.addCertification(blank, signature);
                 }
             } catch (SignatureValidationException e) {
@@ -90,7 +90,7 @@ public final class KeyRingValidator {
         Collections.sort(directKeyRevocations, new SignatureCreationDateComparator(SignatureCreationDateComparator.Order.NEW_TO_OLD));
         for (PGPSignature signature : directKeyRevocations) {
             try {
-                if (SignatureValidator.verifyKeyRevocationSignature(signature, primaryKey, policy, validationDate)) {
+                if (SignatureVerifier.verifyKeyRevocationSignature(signature, primaryKey, policy, validationDate)) {
                     blank = PGPPublicKey.addCertification(blank, signature);
                 }
             } catch (SignatureValidationException e) {
@@ -107,11 +107,11 @@ public final class KeyRingValidator {
             for (PGPSignature signature : signatures) {
                 try {
                     if (SignatureType.valueOf(signature.getSignatureType()) == SignatureType.CERTIFICATION_REVOCATION) {
-                        if (SignatureValidator.verifyUserIdRevocation(userId, signature, primaryKey, policy, validationDate)) {
+                        if (SignatureVerifier.verifyUserIdRevocation(userId, signature, primaryKey, policy, validationDate)) {
                             blank = PGPPublicKey.addCertification(blank, userId, signature);
                         }
                     } else {
-                        if (SignatureValidator.verifyUserIdCertification(userId, signature, primaryKey, policy, validationDate)) {
+                        if (SignatureVerifier.verifyUserIdCertification(userId, signature, primaryKey, policy, validationDate)) {
                             blank = PGPPublicKey.addCertification(blank, userId, signature);
                         }
                     }
@@ -129,11 +129,11 @@ public final class KeyRingValidator {
                 PGPSignature signature = userAttributeSignatureIterator.next();
                 try {
                     if (SignatureType.valueOf(signature.getSignatureType()) == SignatureType.CERTIFICATION_REVOCATION) {
-                        if (SignatureValidator.verifyUserAttributesRevocation(userAttribute, signature, primaryKey, policy, validationDate)) {
+                        if (SignatureVerifier.verifyUserAttributesRevocation(userAttribute, signature, primaryKey, policy, validationDate)) {
                             blank = PGPPublicKey.addCertification(blank, userAttribute, signature);
                         }
                     } else {
-                        if (SignatureValidator.verifyUserAttributesCertification(userAttribute, signature, primaryKey, policy, validationDate)) {
+                        if (SignatureVerifier.verifyUserAttributesCertification(userAttribute, signature, primaryKey, policy, validationDate)) {
                             blank = PGPPublicKey.addCertification(blank, userAttribute, signature);
                         }
                     }

pgpainless-core/src/main/java/org/pgpainless/signature/CertificateValidator.java

@@ -15,7 +15,7 @@
  */
 package org.pgpainless.signature;
 
-import static org.pgpainless.signature.SignatureValidator.verifyOnePassSignature;
+import static org.pgpainless.signature.SignatureVerifier.verifyOnePassSignature;
 
 import java.io.InputStream;
 import java.util.ArrayList;
@@ -40,9 +40,7 @@ import org.pgpainless.policy.Policy;
 import org.pgpainless.signature.subpackets.SignatureSubpacketsUtil;
 
 /**
- * This class implements validity checks on OpenPGP signatures.
+ * A collection of static methods that validate signing certificates (public keys) and verify signature correctness.
- * Its responsibilities are checking if a signing key was eligible to create a certain signature
- * and if the signature is valid at the time of validation.
  */
 public final class CertificateValidator {
 
@@ -85,7 +83,7 @@ public final class CertificateValidator {
         while (primaryKeyRevocationIterator.hasNext()) {
             PGPSignature revocation = primaryKeyRevocationIterator.next();
             try {
-                if (SignatureValidator.verifyKeyRevocationSignature(revocation, primaryKey, policy, signature.getCreationTime())) {
+                if (SignatureVerifier.verifyKeyRevocationSignature(revocation, primaryKey, policy, signature.getCreationTime())) {
                     directKeySignatures.add(revocation);
                 }
             } catch (SignatureValidationException e) {
@@ -99,7 +97,7 @@ public final class CertificateValidator {
         while (keySignatures.hasNext()) {
             PGPSignature keySignature = keySignatures.next();
             try {
-                if (SignatureValidator.verifyDirectKeySignature(keySignature, primaryKey, policy, signature.getCreationTime())) {
+                if (SignatureVerifier.verifyDirectKeySignature(keySignature, primaryKey, policy, signature.getCreationTime())) {
                     directKeySignatures.add(keySignature);
                 }
             } catch (SignatureValidationException e) {
@@ -125,7 +123,7 @@ public final class CertificateValidator {
             while (userIdSigs.hasNext()) {
                 PGPSignature userIdSig = userIdSigs.next();
                 try {
-                    if (SignatureValidator.verifySignatureOverUserId(userId, userIdSig, primaryKey, policy, signature.getCreationTime())) {
+                    if (SignatureVerifier.verifySignatureOverUserId(userId, userIdSig, primaryKey, policy, signature.getCreationTime())) {
                         signaturesOnUserId.add(userIdSig);
                     }
                 } catch (SignatureValidationException e) {
@@ -175,7 +173,7 @@ public final class CertificateValidator {
             while (bindingRevocations.hasNext()) {
                 PGPSignature revocation = bindingRevocations.next();
                 try {
-                    if (SignatureValidator.verifySubkeyBindingRevocation(revocation, primaryKey, signingSubkey, policy, signature.getCreationTime())) {
+                    if (SignatureVerifier.verifySubkeyBindingRevocation(revocation, primaryKey, signingSubkey, policy, signature.getCreationTime())) {
                         subkeySigs.add(revocation);
                     }
                 } catch (SignatureValidationException e) {
@@ -188,7 +186,7 @@ public final class CertificateValidator {
             while (bindingSigs.hasNext()) {
                 PGPSignature bindingSig = bindingSigs.next();
                 try {
-                    if (SignatureValidator.verifySubkeyBindingSignature(bindingSig, primaryKey, signingSubkey, policy, signature.getCreationTime())) {
+                    if (SignatureVerifier.verifySubkeyBindingSignature(bindingSig, primaryKey, signingSubkey, policy, signature.getCreationTime())) {
                         subkeySigs.add(bindingSig);
                     }
                 } catch (SignatureValidationException e) {
@@ -244,7 +242,7 @@ public final class CertificateValidator {
             throws SignatureValidationException {
         validateCertificate(signature, signingKeyRing, policy);
         long keyId = SignatureUtils.determineIssuerKeyId(signature);
-        return SignatureValidator.verifyUninitializedSignature(signature, signedData, signingKeyRing.getPublicKey(keyId), policy, validationDate);
+        return SignatureVerifier.verifyUninitializedSignature(signature, signedData, signingKeyRing.getPublicKey(keyId), policy, validationDate);
     }
 
     /**
@@ -262,10 +260,19 @@ public final class CertificateValidator {
         validateCertificate(signature, verificationKeys, policy);
         long keyId = SignatureUtils.determineIssuerKeyId(signature);
         PGPPublicKey signingKey = verificationKeys.getPublicKey(keyId);
-        SignatureValidator.verifyInitializedSignature(signature, signingKey, policy, signature.getCreationTime());
+        SignatureVerifier.verifyInitializedSignature(signature, signingKey, policy, signature.getCreationTime());
         return true;
     }
 
+    /**
+     * Validate the signing key certificate and the given {@link OnePassSignature}.
+     *
+     * @param signature OpenPGP signature from the signed message
+     * @param onePassSignature corresponding one-pass-signature
+     * @param policy policy
+     * @return true if the certificate is valid and the signature is correct, false otherwise.
+     * @throws SignatureValidationException in case of a validation error
+     */
     public static boolean validateCertificateAndVerifyOnePassSignature(PGPSignature signature, OnePassSignature onePassSignature, Policy policy)
             throws SignatureValidationException {
         validateCertificate(signature, onePassSignature.getVerificationKeys(), policy);

pgpainless-core/src/main/java/org/pgpainless/signature/SignaturePicker.java

@@ -63,7 +63,7 @@ public final class SignaturePicker {
 
         for (PGPSignature signature : signatures) {
             try {
-                SignatureValidator.verifyKeyRevocationSignature(signature, primaryKey, policy, validationDate);
+                SignatureVerifier.verifyKeyRevocationSignature(signature, primaryKey, policy, validationDate);
             } catch (SignatureValidationException e) {
                 // Signature is not valid
                 continue;
@@ -102,7 +102,7 @@ public final class SignaturePicker {
         PGPSignature mostRecentDirectKeySigBySigningKey = null;
         for (PGPSignature signature : directKeySignatures) {
             try {
-                SignatureValidator.verifyDirectKeySignature(signature, signingKey, signedKey, policy, validationDate);
+                SignatureVerifier.verifyDirectKeySignature(signature, signingKey, signedKey, policy, validationDate);
             } catch (SignatureValidationException e) {
                 // Direct key sig is not valid
                 continue;
@@ -180,7 +180,7 @@ public final class SignaturePicker {
         PGPSignature latestUserIdRevocation = null;
         for (PGPSignature signature : signatures) {
             try {
-                SignatureValidator.verifyUserIdRevocation(userId, signature, primaryKey, policy, validationDate);
+                SignatureVerifier.verifyUserIdRevocation(userId, signature, primaryKey, policy, validationDate);
             } catch (SignatureValidationException e) {
                 // User-id revocation is not valid
                 continue;
@@ -211,7 +211,7 @@ public final class SignaturePicker {
         PGPSignature mostRecentUserIdCertification = null;
         for (PGPSignature signature : signatures) {
             try {
-                SignatureValidator.verifyUserIdCertification(userId, signature, primaryKey, policy, validationDate);
+                SignatureVerifier.verifyUserIdCertification(userId, signature, primaryKey, policy, validationDate);
             } catch (SignatureValidationException e) {
                 // User-id certification is not valid
                 continue;
@@ -243,7 +243,7 @@ public final class SignaturePicker {
         PGPSignature latestUserIdCert = null;
         for (PGPSignature signature : signatures) {
             try {
-                SignatureValidator.verifyWasPossiblyMadeByKey(primaryKey, signature);
+                SignatureValidator.wasPossiblyMadeByKey(primaryKey).verify(signature);
                 SignatureValidator.signatureIsCertification().verify(signature);
                 SignatureValidator.signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
                 SignatureValidator.signatureIsAlreadyEffective(validationDate).verify(signature);
@@ -284,7 +284,7 @@ public final class SignaturePicker {
 
         for (PGPSignature signature : signatures) {
             try {
-                SignatureValidator.verifySubkeyBindingRevocation(signature, primaryKey, subkey, policy, validationDate);
+                SignatureVerifier.verifySubkeyBindingRevocation(signature, primaryKey, subkey, policy, validationDate);
             } catch (SignatureValidationException e) {
                 // subkey binding revocation is not valid
                 continue;
@@ -316,7 +316,7 @@ public final class SignaturePicker {
 
         for (PGPSignature signature : subkeyBindingSigs) {
             try {
-                SignatureValidator.verifySubkeyBindingSignature(signature, primaryKey, subkey, policy, validationDate);
+                SignatureVerifier.verifySubkeyBindingSignature(signature, primaryKey, subkey, policy, validationDate);
             } catch (SignatureValidationException validationException) {
                 // Subkey binding sig is not valid
                 continue;

pgpainless-core/src/main/java/org/pgpainless/signature/SignatureValidator.java

@@ -15,8 +15,6 @@
  */
 package org.pgpainless.signature;
 
-import java.io.IOException;
-import java.io.InputStream;
 import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 import java.util.Date;
@@ -48,456 +46,48 @@ import org.pgpainless.util.BCUtil;
 import org.pgpainless.util.DateUtil;
 import org.pgpainless.util.NotationRegistry;
 
+/**
+ * A collection of validators that perform validation steps over signatures.
+ */
 public abstract class SignatureValidator {
 
     public abstract void verify(PGPSignature signature) throws SignatureValidationException;
 
-    /**
-     * Initialize a signature and verify it afterwards by updating it with the signed data.
-     *
-     * @param signature OpenPGP signature
-     * @param signedData input stream containing the signed data
-     * @param signingKey the key that created the signature
-     * @param policy policy
-     * @param validationDate reference date of signature verification
-     * @return true if the signature is successfully verified
-     *
-     * @throws SignatureValidationException if the signature verification fails for some reason
-     */
-    public static boolean verifyUninitializedSignature(PGPSignature signature, InputStream signedData, PGPPublicKey signingKey, Policy policy, Date validationDate) throws SignatureValidationException {
-        initializeSignatureAndUpdateWithSignedData(signature, signedData, signingKey);
-        return verifyInitializedSignature(signature, signingKey, policy, validationDate);
-    }
-
-    /**
-     * Initialize a signature and then update it with the signed data from the given {@link InputStream}.
-     *
-     * @param signature OpenPGP signature
-     * @param signedData input stream containing signed data
-     * @param signingKey key that created the signature
-     *
-     * @throws SignatureValidationException in case the signature cannot be verified for some reason
-     */
-    public static void initializeSignatureAndUpdateWithSignedData(PGPSignature signature, InputStream signedData, PGPPublicKey signingKey)
-            throws SignatureValidationException {
-        try {
-            signature.init(ImplementationFactory.getInstance().getPGPContentVerifierBuilderProvider(), signingKey);
-            int read;
-            byte[] buf = new byte[8192];
-            while ((read = signedData.read(buf)) != -1) {
-                signature.update(buf, 0, read);
-            }
-        } catch (PGPException e) {
-            throw new SignatureValidationException("Cannot init signature.", e);
-        } catch (IOException e) {
-            throw new SignatureValidationException("Cannot update signature.", e);
-        }
-    }
-
-    /**
-     * Verify an initialized signature.
-     * An initialized signature was already updated with the signed data.
-     *
-     * @param signature OpenPGP signature
-     * @param signingKey key that created the signature
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if signature is verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyInitializedSignature(PGPSignature signature, PGPPublicKey signingKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        verifyWasPossiblyMadeByKey(signingKey, signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-
-        try {
-            if (!signature.verify()) {
-                throw new SignatureValidationException("Signature is not correct.");
-            }
-            return true;
-        } catch (PGPException e) {
-            throw new SignatureValidationException("Could not verify signature correctness.", e);
-        }
-    }
-
-    public static boolean verifyOnePassSignature(PGPSignature signature, PGPPublicKey signingKey, OnePassSignature onePassSignature, Policy policy)
-            throws SignatureValidationException {
-        try {
-            verifyWasPossiblyMadeByKey(signingKey, signature);
-            signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-            signatureIsEffective().verify(signature);
-        } catch (SignatureValidationException e) {
-            throw new SignatureValidationException("Signature is not valid: " + e.getMessage(), e);
-        }
-
-        try {
-            if (!onePassSignature.verify(signature)) {
-                throw new SignatureValidationException("Bad signature of key " + Long.toHexString(signingKey.getKeyID()));
-            }
-        } catch (PGPException e) {
-            throw new SignatureValidationException("Could not verify correctness of One-Pass-Signature: " + e.getMessage(), e);
-        }
-
-        return true;
-    }
-
-    /**
-     * Verify a signature (certification or revocation) over a user-id.
-     *
-     * @param userId user-id
-     * @param signature self-signature
-     * @param primaryKey primary key that created the signature
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the signature is successfully verified
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifySignatureOverUserId(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifySignatureOverUserId(userId, signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a signature (certification or revocation) over a user-id.
-     *
-     * @param userId user-id
-     * @param signature certification signature
-     * @param signingKey key that created the certification
-     * @param keyWithUserId key carrying the user-id
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if signature verification is successful
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifySignatureOverUserId(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        SignatureType type = SignatureType.valueOf(signature.getSignatureType());
-        switch (type) {
-            case GENERIC_CERTIFICATION:
-            case NO_CERTIFICATION:
-            case CASUAL_CERTIFICATION:
-            case POSITIVE_CERTIFICATION:
-                return verifyUserIdCertification(userId, signature, signingKey, keyWithUserId, policy, validationDate);
-            case CERTIFICATION_REVOCATION:
-                return verifyUserIdRevocation(userId, signature, signingKey, keyWithUserId, policy, validationDate);
-            default:
-                throw new SignatureValidationException("Signature is not a valid user-id certification/revocation signature: " + type);
-        }
-    }
-
     /**
      * Check, whether there is the possibility that the given signature was created by the given key.
-     * This method throws a {@link SignatureValidationException} if we can say with certainty that the signature
+     * {@link #verify(PGPSignature)} throws a {@link SignatureValidationException} if we can say with certainty that the signature
      * was not created by the given key (e.g. if the sig carries another issuer, issuer fingerprint packet).
      *
      * If there is no information found in the signature about who created it (no issuer, no fingerprint),
-     * return true since it is plausible that the given key created the sig.
+     * {@link #verify(PGPSignature)} will simply return since it is plausible that the given key created the sig.
      *
      * @param signingKey signing key
-     * @param signature signature
+     * @return validator that throws a {@link SignatureValidationException} if the signature was not possibly made by the given key.
-     * @return true only if the signing key either created the signature or the signature doesn't carry signer information
-     * @throws SignatureValidationException if the sig was not created by the key
      */
-    public static boolean verifyWasPossiblyMadeByKey(PGPPublicKey signingKey, PGPSignature signature) throws SignatureValidationException {
+    public static SignatureValidator wasPossiblyMadeByKey(PGPPublicKey signingKey) {
-        OpenPgpV4Fingerprint signingKeyFingerprint = new OpenPgpV4Fingerprint(signingKey);
+        return new SignatureValidator() {
+            @Override
+            public void verify(PGPSignature signature) throws SignatureValidationException {
+                OpenPgpV4Fingerprint signingKeyFingerprint = new OpenPgpV4Fingerprint(signingKey);
 
-        Long issuer = SignatureSubpacketsUtil.getIssuerKeyIdAsLong(signature);
+                Long issuer = SignatureSubpacketsUtil.getIssuerKeyIdAsLong(signature);
-        if (issuer != null) {
+                if (issuer != null) {
-            if (issuer != signingKey.getKeyID()) {
+                    if (issuer != signingKey.getKeyID()) {
-                throw new SignatureValidationException("Signature was not created by " + signingKeyFingerprint + " (signature issuer: " + Long.toHexString(issuer) + ")");
+                        throw new SignatureValidationException("Signature was not created by " + signingKeyFingerprint + " (signature issuer: " + Long.toHexString(issuer) + ")");
-            } else {
+                    }
-                return true;
+                }
+
+                OpenPgpV4Fingerprint fingerprint = SignatureSubpacketsUtil.getIssuerFingerprintAsOpenPgpV4Fingerprint(signature);
+                if (fingerprint != null) {
+                    if (!fingerprint.equals(signingKeyFingerprint)) {
+                        throw new SignatureValidationException("Signature was not created by " + signingKeyFingerprint + " (signature fingerprint: " + fingerprint + ")");
+                    }
+                }
+
+                // No issuer information found, so we cannot rule out that we did not create the sig
             }
-        }
+        };
 
-        OpenPgpV4Fingerprint fingerprint = SignatureSubpacketsUtil.getIssuerFingerprintAsOpenPgpV4Fingerprint(signature);
-        if (fingerprint != null) {
-            if (!fingerprint.equals(signingKeyFingerprint)) {
-                throw new SignatureValidationException("Signature was not created by " + signingKeyFingerprint + " (signature fingerprint: " + fingerprint + ")");
-            } else {
-                return true;
-            }
-        }
-
-        // No issuer information found, so we cannot rule out that we did not create the sig
-        return true;
-    }
-
-    /**
-     * Verify a certification self-signature over a user-id.
-     *
-     * @param userId user-id
-     * @param signature certification signature
-     * @param primaryKey primary key
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the self-signature is verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserIdCertification(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifyUserIdCertification(userId, signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a user-id certification.
-     *
-     * @param userId user-id
-     * @param signature certification signature
-     * @param signingKey key that created the certification
-     * @param keyWithUserId primary key that carries the user-id
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if signature verification is successful
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserIdCertification(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        signatureIsCertification().verify(signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverUserId(userId, keyWithUserId, signingKey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a user-id revocation self-signature.
-     *
-     * @param userId user-id
-     * @param signature user-id revocation signature
-     * @param primaryKey primary key
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the user-id revocation signature is successfully verified
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserIdRevocation(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifyUserIdRevocation(userId, signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a user-id revocation signature.
-     *
-     * @param userId user-id
-     * @param signature revocation signature
-     * @param signingKey key that created the revocation signature
-     * @param keyWithUserId primary key carrying the user-id
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the user-id revocation signature is successfully verified
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserIdRevocation(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        signatureIsOfType(SignatureType.CERTIFICATION_REVOCATION).verify(signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverUserId(userId, keyWithUserId, signingKey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a certification self-signature over a user-attributes packet.
-     *
-     * @param userAttributes user attributes
-     * @param signature certification self-signature
-     * @param primaryKey primary key that carries the user-attributes
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserAttributesCertification(PGPUserAttributeSubpacketVector userAttributes,
-                                                            PGPSignature signature, PGPPublicKey primaryKey,
-                                                            Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifyUserAttributesCertification(userAttributes, signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a certification signature over a user-attributes packet.
-     *
-     * @param userAttributes user attributes
-     * @param signature certification signature
-     * @param signingKey key that created the user-attributes certification
-     * @param keyWithUserAttributes key that carries the user-attributes certification
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserAttributesCertification(PGPUserAttributeSubpacketVector userAttributes,
-                                                            PGPSignature signature, PGPPublicKey signingKey,
-                                                            PGPPublicKey keyWithUserAttributes, Policy policy,
-                                                            Date validationDate)
-            throws SignatureValidationException {
-        signatureIsCertification().verify(signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverUserAttributes(userAttributes, keyWithUserAttributes, signingKey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a user-attributes revocation self-signature.
-     *
-     * @param userAttributes user-attributes
-     * @param signature user-attributes revocation signature
-     * @param primaryKey primary key that carries the user-attributes
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the revocation signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserAttributesRevocation(PGPUserAttributeSubpacketVector userAttributes,
-                                                         PGPSignature signature, PGPPublicKey primaryKey,
-                                                         Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifyUserAttributesRevocation(userAttributes, signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a user-attributes revocation signature.
-     *
-     * @param userAttributes user-attributes
-     * @param signature revocation signature
-     * @param signingKey revocation key
-     * @param keyWithUserAttributes key that carries the user-attributes
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the revocation signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyUserAttributesRevocation(PGPUserAttributeSubpacketVector userAttributes,
-                                                         PGPSignature signature, PGPPublicKey signingKey,
-                                                         PGPPublicKey keyWithUserAttributes, Policy policy,
-                                                         Date validationDate)
-            throws SignatureValidationException {
-        signatureIsOfType(SignatureType.CERTIFICATION_REVOCATION).verify(signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverUserAttributes(userAttributes, keyWithUserAttributes, signingKey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a subkey binding signature.
-     *
-     * @param signature binding signature
-     * @param primaryKey primary key
-     * @param subkey subkey
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the binding signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifySubkeyBindingSignature(PGPSignature signature, PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        signatureIsOfType(SignatureType.SUBKEY_BINDING).verify(signature);
-        signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        hasValidPrimaryKeyBindingSignatureIfRequired(primaryKey, subkey, policy, validationDate).verify(signature);
-        correctSubkeyBindingSignature(primaryKey, subkey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a subkey revocation signature.
-     *
-     * @param signature subkey revocation signature
-     * @param primaryKey primary key
-     * @param subkey subkey
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the subkey revocation signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifySubkeyBindingRevocation(PGPSignature signature, PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate) throws SignatureValidationException {
-        signatureIsOfType(SignatureType.SUBKEY_REVOCATION).verify(signature);
-        signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverKey(primaryKey, subkey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a direct-key self-signature.
-     *
-     * @param signature signature
-     * @param primaryKey primary key
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if the signature can be verified successfully
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyDirectKeySignature(PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        return verifyDirectKeySignature(signature, primaryKey, primaryKey, policy, validationDate);
-    }
-
-    /**
-     * Verify a direct-key signature.
-     *
-     * @param signature signature
-     * @param signingKey signing key
-     * @param signedKey signed key
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if signature verification is successful
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyDirectKeySignature(PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey signedKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        signatureIsOfType(SignatureType.DIRECT_KEY).verify(signature);
-        signatureStructureIsAcceptable(signingKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverKey(signingKey, signedKey).verify(signature);
-
-        return true;
-    }
-
-    /**
-     * Verify a key revocation signature.
-     *
-     * @param signature signature
-     * @param primaryKey primary key
-     * @param policy policy
-     * @param validationDate reference date for signature verification
-     * @return true if signature verification is successful
-     *
-     * @throws SignatureValidationException if signature verification fails for some reason
-     */
-    public static boolean verifyKeyRevocationSignature(PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
-            throws SignatureValidationException {
-        signatureIsOfType(SignatureType.KEY_REVOCATION).verify(signature);
-        signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
-        signatureIsEffective(validationDate).verify(signature);
-        correctSignatureOverKey(primaryKey, primaryKey).verify(signature);
-
-        return true;
     }
 
     /**
@@ -510,7 +100,7 @@ public abstract class SignatureValidator {
      * @param validationDate reference date for signature verification
      * @return validator
      */
-    private static SignatureValidator hasValidPrimaryKeyBindingSignatureIfRequired(PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate) {
+    public static SignatureValidator hasValidPrimaryKeyBindingSignatureIfRequired(PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate) {
         return new SignatureValidator() {
             @Override
             public void verify(PGPSignature signature) throws SignatureValidationException {

pgpainless-core/src/main/java/org/pgpainless/signature/SignatureVerifier.java

@@ -0,0 +1,451 @@
+/*
+ * Copyright 2021 Paul Schaub.
+ *
+ * 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 org.pgpainless.signature;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Date;
+
+import org.bouncycastle.openpgp.PGPException;
+import org.bouncycastle.openpgp.PGPPublicKey;
+import org.bouncycastle.openpgp.PGPSignature;
+import org.bouncycastle.openpgp.PGPUserAttributeSubpacketVector;
+import org.pgpainless.algorithm.SignatureType;
+import org.pgpainless.exception.SignatureValidationException;
+import org.pgpainless.implementation.ImplementationFactory;
+import org.pgpainless.policy.Policy;
+
+/**
+ * Collection of static methods for signature verification.
+ * Signature verification entails validation of certain criteria (see {@link SignatureValidator}, as well as
+ * cryptographic verification of signature correctness.
+ */
+public final class SignatureVerifier {
+
+    private SignatureVerifier() {
+
+    }
+
+    /**
+     * Verify a signature (certification or revocation) over a user-id.
+     *
+     * @param userId user-id
+     * @param signature certification signature
+     * @param signingKey key that created the certification
+     * @param keyWithUserId key carrying the user-id
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if signature verification is successful
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifySignatureOverUserId(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureType type = SignatureType.valueOf(signature.getSignatureType());
+        switch (type) {
+            case GENERIC_CERTIFICATION:
+            case NO_CERTIFICATION:
+            case CASUAL_CERTIFICATION:
+            case POSITIVE_CERTIFICATION:
+                return verifyUserIdCertification(userId, signature, signingKey, keyWithUserId, policy, validationDate);
+            case CERTIFICATION_REVOCATION:
+                return verifyUserIdRevocation(userId, signature, signingKey, keyWithUserId, policy, validationDate);
+            default:
+                throw new SignatureValidationException("Signature is not a valid user-id certification/revocation signature: " + type);
+        }
+    }
+
+    /**
+     * Verify a certification self-signature over a user-id.
+     *
+     * @param userId user-id
+     * @param signature certification signature
+     * @param primaryKey primary key
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the self-signature is verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserIdCertification(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifyUserIdCertification(userId, signature, primaryKey, primaryKey, policy, validationDate);
+    }
+
+    /**
+     * Verify a user-id certification.
+     *
+     * @param userId user-id
+     * @param signature certification signature
+     * @param signingKey key that created the certification
+     * @param keyWithUserId primary key that carries the user-id
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if signature verification is successful
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserIdCertification(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsCertification().verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverUserId(userId, keyWithUserId, signingKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a user-id revocation self-signature.
+     *
+     * @param userId user-id
+     * @param signature user-id revocation signature
+     * @param primaryKey primary key
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the user-id revocation signature is successfully verified
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserIdRevocation(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifyUserIdRevocation(userId, signature, primaryKey, primaryKey, policy, validationDate);
+    }
+
+    /**
+     * Verify a user-id revocation signature.
+     *
+     * @param userId user-id
+     * @param signature revocation signature
+     * @param signingKey key that created the revocation signature
+     * @param keyWithUserId primary key carrying the user-id
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the user-id revocation signature is successfully verified
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserIdRevocation(String userId, PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey keyWithUserId, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.CERTIFICATION_REVOCATION).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverUserId(userId, keyWithUserId, signingKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a certification self-signature over a user-attributes packet.
+     *
+     * @param userAttributes user attributes
+     * @param signature certification self-signature
+     * @param primaryKey primary key that carries the user-attributes
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserAttributesCertification(PGPUserAttributeSubpacketVector userAttributes,
+                                                            PGPSignature signature, PGPPublicKey primaryKey,
+                                                            Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifyUserAttributesCertification(userAttributes, signature, primaryKey, primaryKey, policy, validationDate);
+    }
+
+    /**
+     * Verify a certification signature over a user-attributes packet.
+     *
+     * @param userAttributes user attributes
+     * @param signature certification signature
+     * @param signingKey key that created the user-attributes certification
+     * @param keyWithUserAttributes key that carries the user-attributes certification
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserAttributesCertification(PGPUserAttributeSubpacketVector userAttributes,
+                                                            PGPSignature signature, PGPPublicKey signingKey,
+                                                            PGPPublicKey keyWithUserAttributes, Policy policy,
+                                                            Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsCertification().verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverUserAttributes(userAttributes, keyWithUserAttributes, signingKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a user-attributes revocation self-signature.
+     *
+     * @param userAttributes user-attributes
+     * @param signature user-attributes revocation signature
+     * @param primaryKey primary key that carries the user-attributes
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the revocation signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserAttributesRevocation(PGPUserAttributeSubpacketVector userAttributes,
+                                                         PGPSignature signature, PGPPublicKey primaryKey,
+                                                         Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifyUserAttributesRevocation(userAttributes, signature, primaryKey, primaryKey, policy, validationDate);
+    }
+
+    /**
+     * Verify a user-attributes revocation signature.
+     *
+     * @param userAttributes user-attributes
+     * @param signature revocation signature
+     * @param signingKey revocation key
+     * @param keyWithUserAttributes key that carries the user-attributes
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the revocation signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyUserAttributesRevocation(PGPUserAttributeSubpacketVector userAttributes,
+                                                         PGPSignature signature, PGPPublicKey signingKey,
+                                                         PGPPublicKey keyWithUserAttributes, Policy policy,
+                                                         Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.CERTIFICATION_REVOCATION).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverUserAttributes(userAttributes, keyWithUserAttributes, signingKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a subkey binding signature.
+     *
+     * @param signature binding signature
+     * @param primaryKey primary key
+     * @param subkey subkey
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the binding signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifySubkeyBindingSignature(PGPSignature signature, PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.SUBKEY_BINDING).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.hasValidPrimaryKeyBindingSignatureIfRequired(primaryKey, subkey, policy, validationDate).verify(signature);
+        SignatureValidator.correctSubkeyBindingSignature(primaryKey, subkey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a subkey revocation signature.
+     *
+     * @param signature subkey revocation signature
+     * @param primaryKey primary key
+     * @param subkey subkey
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the subkey revocation signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifySubkeyBindingRevocation(PGPSignature signature, PGPPublicKey primaryKey, PGPPublicKey subkey, Policy policy, Date validationDate) throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.SUBKEY_REVOCATION).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverKey(primaryKey, subkey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a direct-key self-signature.
+     *
+     * @param signature signature
+     * @param primaryKey primary key
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the signature can be verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyDirectKeySignature(PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifyDirectKeySignature(signature, primaryKey, primaryKey, policy, validationDate);
+    }
+
+    /**
+     * Verify a direct-key signature.
+     *
+     * @param signature signature
+     * @param signingKey signing key
+     * @param signedKey signed key
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if signature verification is successful
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyDirectKeySignature(PGPSignature signature, PGPPublicKey signingKey, PGPPublicKey signedKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.DIRECT_KEY).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverKey(signingKey, signedKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Verify a key revocation signature.
+     *
+     * @param signature signature
+     * @param primaryKey primary key
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if signature verification is successful
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyKeyRevocationSignature(PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.signatureIsOfType(SignatureType.KEY_REVOCATION).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(primaryKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+        SignatureValidator.correctSignatureOverKey(primaryKey, primaryKey).verify(signature);
+
+        return true;
+    }
+
+    /**
+     * Initialize a signature and verify it afterwards by updating it with the signed data.
+     *
+     * @param signature OpenPGP signature
+     * @param signedData input stream containing the signed data
+     * @param signingKey the key that created the signature
+     * @param policy policy
+     * @param validationDate reference date of signature verification
+     * @return true if the signature is successfully verified
+     *
+     * @throws SignatureValidationException if the signature verification fails for some reason
+     */
+    public static boolean verifyUninitializedSignature(PGPSignature signature, InputStream signedData, PGPPublicKey signingKey, Policy policy, Date validationDate) throws SignatureValidationException {
+        initializeSignatureAndUpdateWithSignedData(signature, signedData, signingKey);
+        return verifyInitializedSignature(signature, signingKey, policy, validationDate);
+    }
+
+    /**
+     * Initialize a signature and then update it with the signed data from the given {@link InputStream}.
+     *
+     * @param signature OpenPGP signature
+     * @param signedData input stream containing signed data
+     * @param signingKey key that created the signature
+     *
+     * @throws SignatureValidationException in case the signature cannot be verified for some reason
+     */
+    public static void initializeSignatureAndUpdateWithSignedData(PGPSignature signature, InputStream signedData, PGPPublicKey signingKey)
+            throws SignatureValidationException {
+        try {
+            signature.init(ImplementationFactory.getInstance().getPGPContentVerifierBuilderProvider(), signingKey);
+            int read;
+            byte[] buf = new byte[8192];
+            while ((read = signedData.read(buf)) != -1) {
+                signature.update(buf, 0, read);
+            }
+        } catch (PGPException e) {
+            throw new SignatureValidationException("Cannot init signature.", e);
+        } catch (IOException e) {
+            throw new SignatureValidationException("Cannot update signature.", e);
+        }
+    }
+
+    /**
+     * Verify an initialized signature.
+     * An initialized signature was already updated with the signed data.
+     *
+     * @param signature OpenPGP signature
+     * @param signingKey key that created the signature
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if signature is verified successfully
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifyInitializedSignature(PGPSignature signature, PGPPublicKey signingKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        SignatureValidator.wasPossiblyMadeByKey(signingKey).verify(signature);
+        SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+        SignatureValidator.signatureIsEffective(validationDate).verify(signature);
+
+        try {
+            if (!signature.verify()) {
+                throw new SignatureValidationException("Signature is not correct.");
+            }
+            return true;
+        } catch (PGPException e) {
+            throw new SignatureValidationException("Could not verify signature correctness.", e);
+        }
+    }
+
+    public static boolean verifyOnePassSignature(PGPSignature signature, PGPPublicKey signingKey, OnePassSignature onePassSignature, Policy policy)
+            throws SignatureValidationException {
+        try {
+            SignatureValidator.wasPossiblyMadeByKey(signingKey).verify(signature);
+            SignatureValidator.signatureStructureIsAcceptable(signingKey, policy).verify(signature);
+            SignatureValidator.signatureIsEffective().verify(signature);
+        } catch (SignatureValidationException e) {
+            throw new SignatureValidationException("Signature is not valid: " + e.getMessage(), e);
+        }
+
+        try {
+            if (!onePassSignature.verify(signature)) {
+                throw new SignatureValidationException("Bad signature of key " + Long.toHexString(signingKey.getKeyID()));
+            }
+        } catch (PGPException e) {
+            throw new SignatureValidationException("Could not verify correctness of One-Pass-Signature: " + e.getMessage(), e);
+        }
+
+        return true;
+    }
+
+    /**
+     * Verify a signature (certification or revocation) over a user-id.
+     *
+     * @param userId user-id
+     * @param signature self-signature
+     * @param primaryKey primary key that created the signature
+     * @param policy policy
+     * @param validationDate reference date for signature verification
+     * @return true if the signature is successfully verified
+     *
+     * @throws SignatureValidationException if signature verification fails for some reason
+     */
+    public static boolean verifySignatureOverUserId(String userId, PGPSignature signature, PGPPublicKey primaryKey, Policy policy, Date validationDate)
+            throws SignatureValidationException {
+        return verifySignatureOverUserId(userId, signature, primaryKey, primaryKey, policy, validationDate);
+    }
+}

pgpainless-core/src/test/java/org/pgpainless/signature/SignatureWasPossiblyMadeByKeyTest.java

@@ -16,7 +16,6 @@
 package org.pgpainless.signature;
 
 import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.IOException;
@@ -30,7 +29,7 @@ import org.pgpainless.PGPainless;
 import org.pgpainless.exception.SignatureValidationException;
 import org.pgpainless.key.OpenPgpV4Fingerprint;
 
-public class SignatureWasPossibleyMadeByKeyTest {
+public class SignatureWasPossiblyMadeByKeyTest {
 
     public static PGPPublicKeyRing CERT;
     public static PGPPublicKey SIGKEY;
@@ -103,7 +102,7 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "cqP71SMuOwD+JNuWQCd4e1WaTWNXrB1xerzmuWFc\n" +
                 "=4ZFC\n" +
                 "-----END PGP SIGNATURE-----";
-        assertTrue(SignatureValidator.verifyWasPossiblyMadeByKey(SIGKEY, get(sigWithIssuer)));
+        assertWasPossiblyMadeByKey(SIGKEY, get(sigWithIssuer));
     }
 
     @Test
@@ -123,7 +122,7 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "Q0Quxar3DOTtNNQVrXeoeIlVGue0pNCwg6abDj5N\n" +
                 "=IcX1\n" +
                 "-----END PGP SIGNATURE-----\n";
-        assertTrue(SignatureValidator.verifyWasPossiblyMadeByKey(SIGKEY, get(sigWithHashedIssuer)));
+        assertWasPossiblyMadeByKey(SIGKEY, get(sigWithHashedIssuer));
     }
 
     @Test
@@ -144,7 +143,7 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "-----END PGP SIGNATURE-----";
 
 
-        assertTrue(SignatureValidator.verifyWasPossiblyMadeByKey(SIGKEY, get(sigWithNoIssuerNoFingerprint)));
+        assertWasPossiblyMadeByKey(SIGKEY, get(sigWithNoIssuerNoFingerprint));
     }
 
     @Test
@@ -165,11 +164,11 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "=LBou\n" +
                 "-----END PGP SIGNATURE-----\n";
 
-        assertTrue(SignatureValidator.verifyWasPossiblyMadeByKey(SIGKEY, get(sigWithNoIssuerUnhashedFingerprint)));
+        assertWasPossiblyMadeByKey(SIGKEY, get(sigWithNoIssuerUnhashedFingerprint));
     }
 
     @Test
-    public void issuerMismatch() {
+    public void issuerMismatch() throws PGPException, IOException {
         String sig = "-----BEGIN PGP SIGNATURE-----\n" +
                 "\n" +
                 "wsE7BAABCABlBYJgyf21RxQAAAAAAB4AIHNhbHRAbm90YXRpb25zLnNlcXVvaWEt\n" +
@@ -185,11 +184,11 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "cqP71SMuOwD+JNuWQCd4e1WaTWNXrB1xerzmuWFc\n" +
                 "=4ZFC\n" +
                 "-----END PGP SIGNATURE-----";
-        assertThrows(SignatureValidationException.class, () -> SignatureValidator.verifyWasPossiblyMadeByKey(NOSIGKEY, get(sig)));
+        assertWasNotPossiblyMadeByKey(NOSIGKEY, get(sig));
     }
 
     @Test
-    public void noIssuer_fingerprintMismatch() {
+    public void noIssuer_fingerprintMismatch() throws PGPException, IOException {
         String sigWithNoIssuerAndWrongFingerprint = "-----BEGIN PGP SIGNATURE-----\n" +
                 "\n" +
                 "wsExBAABCABlBYJgyf21RxQAAAAAAB4AIHNhbHRAbm90YXRpb25zLnNlcXVvaWEt\n" +
@@ -206,10 +205,19 @@ public class SignatureWasPossibleyMadeByKeyTest {
                 "=A/zE\n" +
                 "-----END PGP SIGNATURE-----\n";
 
-        assertThrows(SignatureValidationException.class, () -> SignatureValidator.verifyWasPossiblyMadeByKey(NOSIGKEY, get(sigWithNoIssuerAndWrongFingerprint)));
+        assertWasNotPossiblyMadeByKey(NOSIGKEY, get(sigWithNoIssuerAndWrongFingerprint));
     }
 
     private PGPSignature get(String encoded) throws PGPException, IOException {
         return SignatureUtils.readSignatures(encoded).get(0);
     }
+
+    private void assertWasPossiblyMadeByKey(PGPPublicKey signatureKey, PGPSignature signature) throws SignatureValidationException {
+        SignatureValidator.wasPossiblyMadeByKey(signatureKey).verify(signature);
+    }
+
+    private void assertWasNotPossiblyMadeByKey(PGPPublicKey signatureKey, PGPSignature signature) {
+        assertThrows(SignatureValidationException.class, () -> assertWasPossiblyMadeByKey(signatureKey, signature));
+    }
+
 }