Calculate MIC like sending

phase2-lib/src/main/java/com/helger/phase2/crypto/BCCryptoHelper.java

@@ -697,6 +697,7 @@ public MimeBodyPart verify (@NonNull final MimeBodyPart aPart,
                               final boolean bUseCertificateInBodyPart,
                               final boolean bForceVerifySigned,
                               @Nullable final Consumer <X509Certificate> aEffectiveCertificateConsumer,
+                              @Nullable final Consumer <MimeBodyPart> aMICSourceConsumer,
                               @NonNull final AS2ResourceHelper aResHelper) throws GeneralSecurityException,
                                                                            IOException,
                                                                            MessagingException,
@@ -754,6 +755,13 @@ public MimeBodyPart verify (@NonNull final MimeBodyPart aPart,
         throw new SignatureException ("Verification failed for SignerInfo " + aSignerInfo);
     }
 
-    return aSignedParser.getContent ();
+    final MimeBodyPart aSignedContent = aSignedParser.getContent ();
+
+    // Invoke callback with the signed content for MIC calculation
+    // This mirrors the sender's callback pattern where MIC is calculated on pre-signature content
+    if (aMICSourceConsumer != null)
+      aMICSourceConsumer.accept (aSignedContent);
+
+    return aSignedContent;
   }
 }

phase2-lib/src/main/java/com/helger/phase2/crypto/ICryptoHelper.java

@@ -224,5 +224,6 @@ MimeBodyPart verify (@NonNull MimeBodyPart aPart,
                        boolean bUseCertificateInBodyPart,
                        boolean bForceVerifySigned,
                        @Nullable Consumer <X509Certificate> aEffectiveCertificateConsumer,
+                       @Nullable Consumer <MimeBodyPart> aMICSourceConsumer,
                        @NonNull AS2ResourceHelper aResHelper) throws Exception;
 }

phase2-lib/src/main/java/com/helger/phase2/message/AbstractMessage.java

@@ -60,6 +60,7 @@ public abstract class AbstractMessage extends AbstractBaseMessage implements IMe
   private static final Logger LOGGER = LoggerFactory.getLogger (AbstractMessage.class);
 
   private MimeBodyPart m_aData;
+  private MimeBodyPart m_aMICSource;
   private IMessageMDN m_aMDN;
   private TempSharedFileInputStream m_aTempSharedFileInputStream;
 
@@ -152,6 +153,17 @@ public final void setData (@Nullable final MimeBodyPart aData)
     }
   }
 
+  @Nullable
+  public final MimeBodyPart getMICSource ()
+  {
+    return m_aMICSource;
+  }
+
+  public final void setMICSource (@Nullable final MimeBodyPart aMICSource)
+  {
+    m_aMICSource = aMICSource;
+  }
+
   @Nullable
   public final IMessageMDN getMDN ()
   {

phase2-lib/src/main/java/com/helger/phase2/message/IMessage.java

@@ -107,6 +107,11 @@ default void setSubject (@Nullable final String sSubject)
 
   void setData (@NonNull MimeBodyPart aData);
 
+  @Nullable
+  MimeBodyPart getMICSource ();
+
+  void setMICSource (@Nullable MimeBodyPart aMICSource);
+
   @Nullable
   IMessageMDN getMDN ();
 

phase2-lib/src/main/java/com/helger/phase2/processor/receiver/net/AS2ReceiverHandler.java

@@ -33,6 +33,7 @@
 package com.helger.phase2.processor.receiver.net;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.Socket;
 import java.security.PrivateKey;
 import java.security.cert.X509Certificate;
@@ -302,18 +303,24 @@ protected void verify (@NonNull final IMessage aMsg, @NonNull final AS2ResourceH
           }
 
           final Wrapper <X509Certificate> aCertHolder = new Wrapper <> ();
+          final Wrapper <MimeBodyPart> aMICSourceHolder = new Wrapper <> ();
           final MimeBodyPart aVerifiedData = aCryptoHelper.verify (aMsg.getData (),
                                                                    aSenderCert,
                                                                    bUseCertificateInBodyPart,
                                                                    bForceVerify,
                                                                    aCertHolder::set,
+                                                                   aMICSourceHolder::set,
                                                                    aResHelper);
           final Consumer <X509Certificate> aExternalConsumer = getVerificationCertificateConsumer ();
           if (aExternalConsumer != null)
             aExternalConsumer.accept (aCertHolder.get ());
 
           aMsg.setData (aVerifiedData);
 
+          // Store the MIC source for later calculation (mirrors sender's callback pattern)
+          if (aMICSourceHolder.isSet ())
+            aMsg.setMICSource (aMICSourceHolder.get ());
+
           // Remember that message was signed and verified
           aMsg.attrs ().putIn (AS2Message.ATTRIBUTE_RECEIVED_SIGNED, true);
 
@@ -531,11 +538,27 @@ public void handleIncomingMessage (@NonNull final String sClientInfo,
           // Put received data in a MIME body part
           final String sReceivedContentType = AS2HttpHelper.getCleanContentType (aMsg.getHeader (CHttpHeader.CONTENT_TYPE));
 
+          // Read raw bytes from DataSource to preserve original content for MIC calculation
+          final byte [] aRawBytes;
+          try (final InputStream aIS = aMsgData.getInputStream ())
+          {
+            aRawBytes = StreamHelper.getAllBytes (aIS);
+          }
+
+          // Create MimeBodyPart with raw bytes using ByteArrayDataSource
+          // This ensures MIC calculation uses exact bytes as received, without JavaMail modifications
+          final ByteArrayDataSource aByteArrayDS = new ByteArrayDataSource (aRawBytes, sReceivedContentType, null);
           final MimeBodyPart aReceivedPart = new MimeBodyPart ();
-          aReceivedPart.setDataHandler (new DataHandler (aMsgData));
+          aReceivedPart.setDataHandler (new DataHandler (aByteArrayDS));
 
           // Header must be set AFTER the DataHandler!
           aReceivedPart.setHeader (CHttpHeader.CONTENT_TYPE, sReceivedContentType);
+
+          // Copy Content-Disposition from HTTP headers if present (important for MIC calculation on unsigned messages)
+          final String sContentDisposition = aMsg.getHeader (CHttpHeader.CONTENT_DISPOSITION);
+          if (sContentDisposition != null)
+            aReceivedPart.setHeader (CHttpHeader.CONTENT_DISPOSITION, sContentDisposition);
+
           aMsg.setData (aReceivedPart);
         }
         catch (final Exception ex)
@@ -565,17 +588,6 @@ public void handleIncomingMessage (@NonNull final String sClientInfo,
                                               () -> AbstractActiveNetModule.DISP_PARTNERSHIP_NOT_FOUND);
         }
 
-        // Calculate MIC before decrypt and decompress (see #140)
-        try
-        {
-          aIncomingMIC = AS2Helper.createMICOnReception (aMsg);
-        }
-        catch (final Exception ex)
-        {
-          // Ignore error
-          throw WrappedAS2Exception.wrap (ex);
-        }
-
         // Per RFC5402 compression is always before encryption but can be before
         // or after signing of message but only in one place
         final ICryptoHelper aCryptoHelper = AS2Helper.getCryptoHelper ();
@@ -596,6 +608,26 @@ public void handleIncomingMessage (@NonNull final String sClientInfo,
         // Verify may fail, if our certificate is expired
         verify (aMsg, aResHelper);
 
+        // For unsigned messages, set MIC source to current data (after decrypt/decompress)
+        // For signed messages, this was already set by the verify() callback
+        if (aMsg.getMICSource () == null)
+        {
+          aMsg.setMICSource (aMsg.getData ());
+        }
+
+        // Calculate MIC AFTER decryption and signature verification (RFC 4130)
+        // The MIC must be calculated on the same data that the sender calculated it on,
+        // which is the decrypted signed content, not the encrypted envelope
+        try
+        {
+          aIncomingMIC = AS2Helper.createMICOnReception (aMsg);
+        }
+        catch (final Exception ex)
+        {
+          // Ignore error
+          throw WrappedAS2Exception.wrap (ex);
+        }
+
         if (aCryptoHelper.isCompressed (aMsg.getContentType ()))
         {
           // Per RFC5402 compression is always before encryption but can be

phase2-lib/src/main/java/com/helger/phase2/util/AS2Helper.java

@@ -268,7 +268,23 @@ public static MIC createMICOnReception (@NonNull final AS2Message aMsg) throws E
                                          aPartnership.getEncryptAlgorithm () != null ||
                                          aPartnership.getCompressionType () != null;
 
-    return getCryptoHelper ().calculateMIC (aMsg.getData (), eSigningAlgorithm, bIncludeHeadersInMIC);
+    // Use the MIC source captured during signature verification (via callback)
+    // This mirrors the sender's callback pattern where MIC is calculated on pre-signature content
+    MimeBodyPart aPartToHash = aMsg.getMICSource ();
+    if (aPartToHash == null)
+    {
+      // Fallback for unsigned messages - use the message data directly
+      aPartToHash = aMsg.getData ();
+      LOGGER.info ("createMICOnReception: No MIC source captured (unsigned message), using message data directly");
+    }
+    else
+    {
+      LOGGER.info ("createMICOnReception: Using captured MIC source from signature verification");
+    }
+
+    LOGGER.info ("createMICOnReception: signingAlgorithm=" + aPartnership.getSigningAlgorithm () + ", contentType=" + aPartToHash.getContentType ());
+
+    return getCryptoHelper ().calculateMIC (aPartToHash, eSigningAlgorithm, bIncludeHeadersInMIC);
   }
 
   /**
@@ -444,6 +460,7 @@ public static void parseMDN (@NonNull final IMessage aMsg,
                                           bUseCertificateInBodyPart,
                                           bForceVerify,
                                           aCertHolder::set,
+                                          null,
                                           aResHelper);
         if (aEffectiveCertificateConsumer != null)
           aEffectiveCertificateConsumer.accept (aCertHolder.get ());

phase2-lib/src/test/java/com/helger/phase2/crypto/BCCryptoHelperTest.java

@@ -146,7 +146,7 @@ public void testSignWithAllAlgorithms () throws Exception
 
           // Verify as well
           LOGGER.info ("  Now verifying result of signing algo " + eAlgo);
-          aCryptoHelper.verify (aSigned, (X509Certificate) PKE.getCertificate (), bIncludeCert, true, null, aResHelper);
+          aCryptoHelper.verify (aSigned, (X509Certificate) PKE.getCertificate (), bIncludeCert, true, null, null, aResHelper);
         }
     }
   }