Introduce SigningResult class to allow for additional signing information to be returned

pgpainless-sop/src/main/java/org/pgpainless/sop/SignImpl.java

@@ -28,6 +28,7 @@ import org.pgpainless.key.protection.SecretKeyRingProtector;
 import org.pgpainless.util.ArmoredOutputStreamFactory;
 import sop.MicAlg;
 import sop.ReadyWithResult;
+import sop.SigningResult;
 import sop.enums.SignAs;
 import sop.exception.SOPGPException;
 import sop.operation.Sign;
@@ -69,7 +70,7 @@ public class SignImpl implements Sign {
     }
 
     @Override
-    public ReadyWithResult<MicAlg> data(InputStream data) throws IOException {
+    public ReadyWithResult<SigningResult> data(InputStream data) throws IOException {
         ByteArrayOutputStream buffer = new ByteArrayOutputStream();
         try {
             EncryptionStream signingStream = PGPainless.encryptAndOrSign()
@@ -77,9 +78,9 @@ public class SignImpl implements Sign {
                     .withOptions(ProducerOptions.sign(signingOptions)
                             .setAsciiArmor(armor));
 
-            return new ReadyWithResult<MicAlg>() {
+            return new ReadyWithResult<SigningResult>() {
                 @Override
-                public MicAlg writeTo(OutputStream outputStream) throws IOException {
+                public SigningResult writeTo(OutputStream outputStream) throws IOException {
 
                     if (signingStream.isClosed()) {
                         throw new IllegalStateException("EncryptionStream is already closed.");
@@ -106,7 +107,9 @@ public class SignImpl implements Sign {
                     out.close();
                     outputStream.close(); // armor out does not close underlying stream
 
-                    return micAlgFromSignatures(signatures);
+                    return SigningResult.builder()
+                            .setMicAlg(micAlgFromSignatures(signatures))
+                            .build();
                 }
             };
 

sop-java-picocli/src/main/java/sop/cli/picocli/commands/SignCmd.java

@@ -15,6 +15,7 @@ import java.util.List;
 import picocli.CommandLine;
 import sop.MicAlg;
 import sop.ReadyWithResult;
+import sop.SigningResult;
 import sop.cli.picocli.Print;
 import sop.cli.picocli.SopCLI;
 import sop.enums.SignAs;
@@ -93,9 +94,10 @@ public class SignCmd implements Runnable {
         }
 
         try {
-            ReadyWithResult<MicAlg> ready = sign.data(System.in);
-            MicAlg micAlg = ready.writeTo(System.out);
+            ReadyWithResult<SigningResult> ready = sign.data(System.in);
+            SigningResult result = ready.writeTo(System.out);
 
+            MicAlg micAlg = result.getMicAlg();
             if (micAlgOut != null) {
                 // Write micalg out
                 micAlgOut.createNewFile();

sop-java-picocli/src/test/java/sop/cli/picocli/commands/SignCmdTest.java

@@ -19,9 +19,9 @@ import java.io.OutputStream;
 import com.ginsberg.junit.exit.ExpectSystemExitWithStatus;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import sop.MicAlg;
 import sop.ReadyWithResult;
 import sop.SOP;
+import sop.SigningResult;
 import sop.cli.picocli.SopCLI;
 import sop.exception.SOPGPException;
 import sop.operation.Sign;
@@ -34,10 +34,10 @@ public class SignCmdTest {
     @BeforeEach
     public void mockComponents() throws IOException, SOPGPException.ExpectedText {
         sign = mock(Sign.class);
-        when(sign.data((InputStream) any())).thenReturn(new ReadyWithResult<MicAlg>() {
+        when(sign.data((InputStream) any())).thenReturn(new ReadyWithResult<SigningResult>() {
             @Override
-            public MicAlg writeTo(OutputStream outputStream) {
-                return MicAlg.fromHashAlgorithmId(10);
+            public SigningResult writeTo(OutputStream outputStream) {
+                return SigningResult.builder().build();
             }
         });
 
@@ -110,9 +110,9 @@ public class SignCmdTest {
     @Test
     @ExpectSystemExitWithStatus(1)
     public void data_ioExceptionCausesExit1() throws IOException, SOPGPException.ExpectedText {
-        when(sign.data((InputStream) any())).thenReturn(new ReadyWithResult<MicAlg>() {
+        when(sign.data((InputStream) any())).thenReturn(new ReadyWithResult<SigningResult>() {
             @Override
-            public MicAlg writeTo(OutputStream outputStream) throws IOException {
+            public SigningResult writeTo(OutputStream outputStream) throws IOException {
                 throw new IOException();
             }
         });

sop-java/src/main/java/sop/SigningResult.java

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop;
+
+/**
+ * This class contains various information about a signed message.
+ */
+public final class SigningResult {
+
+    private final MicAlg micAlg;
+
+    private SigningResult(MicAlg micAlg) {
+        this.micAlg = micAlg;
+    }
+
+    /**
+     * Return a string identifying the digest mechanism used to create the signed message.
+     * This is useful for setting the micalg= parameter for the multipart/signed
+     * content type of a PGP/MIME object as described in section 5 of [RFC3156].
+     *
+     * If more than one signature was generated and different digest mechanisms were used,
+     * the value of the micalg object is an empty string.
+     *
+     * @return micalg
+     */
+    public MicAlg getMicAlg() {
+        return micAlg;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static class Builder {
+
+        private MicAlg micAlg;
+
+        public Builder setMicAlg(MicAlg micAlg) {
+            this.micAlg = micAlg;
+            return this;
+        }
+
+        public SigningResult build() {
+            SigningResult signingResult = new SigningResult(micAlg);
+            return signingResult;
+        }
+    }
+}

sop-java/src/main/java/sop/operation/Sign.java

@@ -8,8 +8,8 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
-import sop.MicAlg;
 import sop.ReadyWithResult;
+import sop.SigningResult;
 import sop.enums.SignAs;
 import sop.exception.SOPGPException;
 
@@ -55,7 +55,7 @@ public interface Sign {
      * @param data input stream containing data
      * @return ready
      */
-    ReadyWithResult<MicAlg> data(InputStream data) throws IOException, SOPGPException.ExpectedText;
+    ReadyWithResult<SigningResult> data(InputStream data) throws IOException, SOPGPException.ExpectedText;
 
     /**
      * Signs data.
@@ -63,7 +63,7 @@ public interface Sign {
      * @param data byte array containing data
      * @return ready
      */
-    default ReadyWithResult<MicAlg> data(byte[] data) throws IOException, SOPGPException.ExpectedText {
+    default ReadyWithResult<SigningResult> data(byte[] data) throws IOException, SOPGPException.ExpectedText {
         return data(new ByteArrayInputStream(data));
     }
 }