Restore legacy signature algorithms for signing

CHANGELOG.md

@@ -3,7 +3,34 @@
 All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
-## [3.1-?] - TBD
+## [3.2] - TBD
+
+### Changes
+
+- Added legacy signing algorithms (`SHA256_WITH_RSA_ENCRYPTION`, `SHA384_WITH_RSA_ENCRYPTION`, `SHA512_WITH_RSA_ENCRYPTION`) for RSASSA-PKCS#1 v1.5.
+  - Compatible with DigiDoc4j library which does not support RSASSA-PSS.
+  - Use `SigningSignatureAlgorithm` enum and `withSignatureAlgorithm()` on signature session builders.
+  - Use `SigningSignatureAlgorithm.getHashAlgorithmForLegacy()` when creating `SignableData` for legacy algorithms.
+  - Legacy algorithms do not use `signatureAlgorithmParameters` in requests or responses.
+- Split `SignatureAlgorithm` into `AuthenticationSignatureAlgorithm` (authentication) and `SigningSignatureAlgorithm` (signing).
+  - Only allowed `AuthenticationSignatureAlgorithm` is `RSASSA_PSS`; default `SigningSignatureAlgorithm` is `RSASSA_PSS`.
+- Added `SignatureFactory` interface for creating `java.security.Signature` instance for verifying signature and added its implementations:
+  - `RsaSsaPssSignatureFactory`
+  - `RsaSsaPkcs1SignatureFactory`
+- Changed `SignatureValueValidator.validate` last parameter from `RsaSsaPssParameters` to `SignatureFactory`:
+- The following classes are moved from `ee.sk.smartid` to `ee.sk.smartid.signature`:
+  - `AuthenticationSignatureAlgorithm`
+  - `DigestInput`
+  - `MaskGenAlgorithm`
+  - `RsaSsaPssParameters`
+  - `SignableData`
+  - `SignableHash`
+  - `SignatureValueValidator`
+  - `SignatureValueValidatorImpl`
+  - `SigningSignatureAlgorithm`
+  - `TrailerField`
+
+## [3.1] - 2025-10-15
 
 ### Structural changes
 

MIGRATION_GUIDE.md

@@ -4,6 +4,43 @@ Library v3.1 supports only Smart-ID v3 API.
 All the previous v2 related code has been removed and all the code necessary for Smart-ID API v3 is under package smartid. 
 Some classes could also be used in v3 and for those classes the package did not change.
 
+# Migrating from library v3.1 to v3.2
+
+For signing flows are restored legacy RSASSA-PKCS#1 v1.5 algorithms (`SHA256_WITH_RSA_ENCRYPTION`, `SHA384_WITH_RSA_ENCRYPTION`, `SHA512_WITH_RSA_ENCRYPTION`) which are compatible with DigiDoc4j's signing support.
+For that reason:
+- `SignatureAlgorithm` class is split into `AuthenticationSignatureAlgorithm` and `SigningSignatureAlgorithm`.
+- `SignatureValueValidator.validate` last parameter changed from `RsaSsaPssParameters` to `SignatureFactory`
+
+Changes needed in authentication flows:
+- change `SignatureAlgorithm` to `AuthenticationSignatureAlgorithm`
+- change `SignatureValueValidator.validate` last parameter from `RsaSsaPssParameters` to `new RsaSsaPssSignatureFactory(RsaSsaPssParameters)`
+
+Changes needed in signing flows:
+- change `SignatureAlgorithm` to `SigningSignatureAlgorithm`
+- suggestion for `SignatureValueValidator.validate` last parameter changes:
+  - when using only signature algorithm RSASSA_PSS then use `new RsaSsaPssSignatureFactory(RsaSsaPssParameters)`
+  - when using only legacy signature algorithms (`SHA256_WITH_RSA_ENCRYPTION`, `SHA384_WITH_RSA_ENCRYPTION`, `SHA512_WITH_RSA_ENCRYPTION`) then use `new RsaSsaPkcs1SignatureFactory(SigningSignatureAlgorithm)`
+  - when both RSASSA_PSS and legacy RSA algorithms are used then possible solution is:
+    ```java
+    SignatureFactory signatureFactory = signatureResponse.getSignatureAlgorithm().isLegacyRsa()
+            ? new RsaSsaPkcs1SignatureFactory(signatureResponse.getSignatureAlgorithm())
+            : new RsaSsaPssSignatureFactory(signatureResponse.getRsaSsaPssParameters());
+    ```
+
+The following classes are moved from `ee.sk.smartid` to `ee.sk.smartid.signature` so when used then imports need to be adjusted:
+- `AuthenticationSignatureAlgorithm`
+- `DigestInput`
+- `MaskGenAlgorithm`
+- `RsaSsaPssParameters`
+- `SignableData`
+- `SignableHash`
+- `SignatureValueValidator`
+- `SignatureValueValidatorImpl`
+- `SigningSignatureAlgorithm`
+- `TrailerField`
+
+For legacy RSA with DigiDoc4j there is new chapter in README.md: [Legacy algorithms for signing with DigiDoc4j](./README.md#legacy-algorithms-for-signing-with-digidoc4j)
+
 # Migrating from Smart-ID v2 to Smart-ID v3 API
 
 ## Migrating authentication

pom.xml

@@ -7,7 +7,7 @@
     <groupId>ee.sk.smartid</groupId>
     <artifactId>smart-id-java-client</artifactId>
     <packaging>jar</packaging>
-    <version>3.0-SNAPSHOT</version>
+    <version>3.2-SNAPSHOT</version>
 
     <name>Smart-ID Java client</name>
     <description>Smart-ID Java client is a Java library that can be used for easy integration of the Smart-ID solution to information systems or e-services</description>

src/main/java/ee/sk/smartid/AuthenticationResponse.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -31,6 +31,7 @@
 import java.util.Base64;
 
 import ee.sk.smartid.exception.UnprocessableSmartIdResponseException;
+import ee.sk.smartid.signature.RsaSsaPssParameters;
 
 /**
  * The authentication response after a successful authentication session status response was received.

src/main/java/ee/sk/smartid/AuthenticationResponseMapperImpl.java

@@ -39,6 +39,10 @@
 import ee.sk.smartid.rest.dao.SessionResult;
 import ee.sk.smartid.rest.dao.SessionSignature;
 import ee.sk.smartid.rest.dao.SessionStatus;
+import ee.sk.smartid.signature.AuthenticationSignatureAlgorithm;
+import ee.sk.smartid.signature.MaskGenAlgorithm;
+import ee.sk.smartid.signature.RsaSsaPssParameters;
+import ee.sk.smartid.signature.TrailerField;
 import ee.sk.smartid.util.StringUtil;
 
 /**
@@ -177,7 +181,7 @@ private static void validateSignature(SessionSignature sessionSignature) {
         if (StringUtil.isEmpty(sessionSignature.getSignatureAlgorithm())) {
             throw new UnprocessableSmartIdResponseException("Authentication session status field 'signature.signatureAlgorithm' is empty");
         }
-        if (!SignatureAlgorithm.isSupported(sessionSignature.getSignatureAlgorithm())) {
+        if (!AuthenticationSignatureAlgorithm.isSupported(sessionSignature.getSignatureAlgorithm())) {
             logger.error("Authentication session status field 'signature.signatureAlgorithm' has invalid value: {}", sessionSignature.getSignatureAlgorithm());
             throw new UnprocessableSmartIdResponseException("Authentication session status field 'signature.signatureAlgorithm' has unsupported value");
         }

src/main/java/ee/sk/smartid/DeviceLinkAuthenticationResponseValidator.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -37,6 +37,9 @@
 import ee.sk.smartid.exception.useraccount.CertificateLevelMismatchException;
 import ee.sk.smartid.rest.dao.DeviceLinkAuthenticationSessionRequest;
 import ee.sk.smartid.rest.dao.SessionStatus;
+import ee.sk.smartid.signature.RsaSsaPssSignatureFactory;
+import ee.sk.smartid.signature.SignatureValueValidator;
+import ee.sk.smartid.signature.SignatureValueValidatorImpl;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.StringUtil;
 
@@ -159,7 +162,7 @@ private void validateSignature(AuthenticationResponse authenticationResponse,
         signatureValueValidator.validate(authenticationResponse.getSignatureValue(),
                 payload,
                 authenticationResponse.getCertificate(),
-                authenticationResponse.getRsaSsaPssSignatureParameters());
+                new RsaSsaPssSignatureFactory(authenticationResponse.getRsaSsaPssSignatureParameters()));
     }
 
     private byte[] constructPayload(AuthenticationResponse authenticationResponse,

src/main/java/ee/sk/smartid/DeviceLinkAuthenticationSessionRequestBuilder.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -42,6 +42,7 @@
 import ee.sk.smartid.rest.dao.RequestProperties;
 import ee.sk.smartid.rest.dao.SemanticsIdentifier;
 import ee.sk.smartid.rest.dao.SignatureAlgorithmParameters;
+import ee.sk.smartid.signature.AuthenticationSignatureAlgorithm;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.SetUtil;
 import ee.sk.smartid.util.StringUtil;
@@ -59,7 +60,7 @@ public class DeviceLinkAuthenticationSessionRequestBuilder {
     private String relyingPartyName;
     private AuthenticationCertificateLevel certificateLevel = AuthenticationCertificateLevel.QUALIFIED;
     private String rpChallenge;
-    private SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.RSASSA_PSS;
+    private AuthenticationSignatureAlgorithm signatureAlgorithm = AuthenticationSignatureAlgorithm.RSASSA_PSS;
     private HashAlgorithm hashAlgorithm = HashAlgorithm.SHA3_512;
     private List<DeviceLinkInteraction> interactions;
     private Boolean shareMdClientIpAddress;
@@ -136,7 +137,7 @@ public DeviceLinkAuthenticationSessionRequestBuilder withRpChallenge(String rpCh
      * @param signatureAlgorithm the signature algorithm
      * @return this builder
      */
-    public DeviceLinkAuthenticationSessionRequestBuilder withSignatureAlgorithm(SignatureAlgorithm signatureAlgorithm) {
+    public DeviceLinkAuthenticationSessionRequestBuilder withSignatureAlgorithm(AuthenticationSignatureAlgorithm signatureAlgorithm) {
         this.signatureAlgorithm = signatureAlgorithm;
         return this;
     }

src/main/java/ee/sk/smartid/DeviceLinkSignatureSessionRequestBuilder.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -41,6 +41,10 @@
 import ee.sk.smartid.rest.dao.SemanticsIdentifier;
 import ee.sk.smartid.rest.dao.SignatureAlgorithmParameters;
 import ee.sk.smartid.rest.dao.DeviceLinkSignatureSessionRequest;
+import ee.sk.smartid.signature.DigestInput;
+import ee.sk.smartid.signature.SignableData;
+import ee.sk.smartid.signature.SignableHash;
+import ee.sk.smartid.signature.SigningSignatureAlgorithm;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.SetUtil;
 import ee.sk.smartid.util.StringUtil;
@@ -63,7 +67,7 @@ public class DeviceLinkSignatureSessionRequestBuilder {
     private Set<String> capabilities;
     private List<DeviceLinkInteraction> interactions;
     private Boolean shareMdClientIpAddress;
-    private SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.RSASSA_PSS;
+    private SigningSignatureAlgorithm signatureAlgorithm = SigningSignatureAlgorithm.RSASSA_PSS;
     private String initialCallbackUrl;
     private DigestInput digestInput;
 
@@ -183,7 +187,7 @@ public DeviceLinkSignatureSessionRequestBuilder withShareMdClientIpAddress(boole
      * @param signatureAlgorithm the signature algorithm
      * @return this builder
      */
-    public DeviceLinkSignatureSessionRequestBuilder withSignatureAlgorithm(SignatureAlgorithm signatureAlgorithm) {
+    public DeviceLinkSignatureSessionRequestBuilder withSignatureAlgorithm(SigningSignatureAlgorithm signatureAlgorithm) {
         this.signatureAlgorithm = signatureAlgorithm;
         return this;
     }
@@ -287,9 +291,12 @@ private DeviceLinkSessionResponse initSignatureSession(DeviceLinkSignatureSessio
     }
 
     private DeviceLinkSignatureSessionRequest createSignatureSessionRequest() {
+        SignatureAlgorithmParameters algorithmParams = signatureAlgorithm.isLegacyRsa()
+                ? null
+                : new SignatureAlgorithmParameters(digestInput.hashAlgorithm().getAlgorithmName());
         var signatureProtocolParameters = new RawDigestSignatureProtocolParameters(digestInput.getDigestInBase64(),
                 signatureAlgorithm.getAlgorithmName(),
-                new SignatureAlgorithmParameters(digestInput.hashAlgorithm().getAlgorithmName()));
+                algorithmParams);
         return new DeviceLinkSignatureSessionRequest(relyingPartyUUID,
                 relyingPartyName,
                 certificateLevel != null ? certificateLevel.name() : null,

src/main/java/ee/sk/smartid/LinkedNotificationSignatureSessionRequestBuilder.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -39,6 +39,10 @@
 import ee.sk.smartid.rest.dao.RawDigestSignatureProtocolParameters;
 import ee.sk.smartid.rest.dao.RequestProperties;
 import ee.sk.smartid.rest.dao.SignatureAlgorithmParameters;
+import ee.sk.smartid.signature.DigestInput;
+import ee.sk.smartid.signature.SignableData;
+import ee.sk.smartid.signature.SignableHash;
+import ee.sk.smartid.signature.SigningSignatureAlgorithm;
 import ee.sk.smartid.util.SetUtil;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.StringUtil;
@@ -54,7 +58,7 @@ public class LinkedNotificationSignatureSessionRequestBuilder {
     private String relyingPartyName;
     private String documentNumber;
     private DigestInput digestInput;
-    private SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.RSASSA_PSS;
+    private SigningSignatureAlgorithm signatureAlgorithm = SigningSignatureAlgorithm.RSASSA_PSS;
     private String linkedSessionID;
     private List<DeviceLinkInteraction> interactions;
     private CertificateLevel certificateLevel;
@@ -151,7 +155,7 @@ public LinkedNotificationSignatureSessionRequestBuilder withSignableHash(Signabl
      * @param signatureAlgorithm The signature algorithm
      * @return this builder
      */
-    public LinkedNotificationSignatureSessionRequestBuilder withSignatureAlgorithm(SignatureAlgorithm signatureAlgorithm) {
+    public LinkedNotificationSignatureSessionRequestBuilder withSignatureAlgorithm(SigningSignatureAlgorithm signatureAlgorithm) {
         this.signatureAlgorithm = signatureAlgorithm;
         return this;
     }
@@ -257,9 +261,12 @@ private void validateRequestParameters() {
     }
 
     private LinkedSignatureSessionRequest createSessionRequest() {
+        SignatureAlgorithmParameters algorithmParams = signatureAlgorithm.isLegacyRsa()
+                ? null
+                : new SignatureAlgorithmParameters(digestInput.hashAlgorithm().getAlgorithmName());
         var rawDigestParams = new RawDigestSignatureProtocolParameters(digestInput.getDigestInBase64(),
                 signatureAlgorithm.getAlgorithmName(),
-                new SignatureAlgorithmParameters(digestInput.hashAlgorithm().getAlgorithmName()));
+                algorithmParams);
         return new LinkedSignatureSessionRequest(relyingPartyUUID,
                 relyingPartyName,
                 certificateLevel != null ? certificateLevel.name() : null,

src/main/java/ee/sk/smartid/NotificationAuthenticationResponseValidator.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2025 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -36,6 +36,9 @@
 import ee.sk.smartid.exception.useraccount.CertificateLevelMismatchException;
 import ee.sk.smartid.rest.dao.NotificationAuthenticationSessionRequest;
 import ee.sk.smartid.rest.dao.SessionStatus;
+import ee.sk.smartid.signature.RsaSsaPssSignatureFactory;
+import ee.sk.smartid.signature.SignatureValueValidator;
+import ee.sk.smartid.signature.SignatureValueValidatorImpl;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.StringUtil;
 
@@ -152,7 +155,7 @@ private void validateSignature(AuthenticationResponse authenticationResponse,
         signatureValueValidator.validate(authenticationResponse.getSignatureValue(),
                 payload,
                 authenticationResponse.getCertificate(),
-                authenticationResponse.getRsaSsaPssSignatureParameters());
+                new RsaSsaPssSignatureFactory(authenticationResponse.getRsaSsaPssSignatureParameters()));
     }
 
     private byte[] constructPayload(AuthenticationResponse authenticationResponse,

src/main/java/ee/sk/smartid/NotificationAuthenticationSessionRequestBuilder.java

@@ -4,7 +4,7 @@
  * #%L
  * Smart ID sample Java client
  * %%
- * Copyright (C) 2018 - 2024 SK ID Solutions AS
+ * Copyright (C) 2018 - 2026 SK ID Solutions AS
  * %%
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -42,6 +42,7 @@
 import ee.sk.smartid.rest.dao.RequestProperties;
 import ee.sk.smartid.rest.dao.SemanticsIdentifier;
 import ee.sk.smartid.rest.dao.SignatureAlgorithmParameters;
+import ee.sk.smartid.signature.AuthenticationSignatureAlgorithm;
 import ee.sk.smartid.util.InteractionUtil;
 import ee.sk.smartid.util.SetUtil;
 import ee.sk.smartid.util.StringUtil;
@@ -57,7 +58,7 @@ public class NotificationAuthenticationSessionRequestBuilder {
     private String relyingPartyName;
     private AuthenticationCertificateLevel certificateLevel;
     private String rpChallenge;
-    private SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.RSASSA_PSS;
+    private AuthenticationSignatureAlgorithm signatureAlgorithm = AuthenticationSignatureAlgorithm.RSASSA_PSS;
     private HashAlgorithm hashAlgorithm = HashAlgorithm.SHA3_512;
     private List<NotificationInteraction> interactions;
     private Boolean shareMdClientIpAddress;
@@ -130,7 +131,7 @@ public NotificationAuthenticationSessionRequestBuilder withRpChallenge(String rp
      * @param signatureAlgorithm the signature algorithm
      * @return this builder
      */
-    public NotificationAuthenticationSessionRequestBuilder withSignatureAlgorithm(SignatureAlgorithm signatureAlgorithm) {
+    public NotificationAuthenticationSessionRequestBuilder withSignatureAlgorithm(AuthenticationSignatureAlgorithm signatureAlgorithm) {
         this.signatureAlgorithm = signatureAlgorithm;
         return this;
     }