message: detect top-level smime parts + test

Fixes #2745

lib/message/mu-message.cc

@@ -484,6 +484,28 @@ handle_encrypted(const MimeMultipartEncrypted& part, Message::Private& info)
 		handle_object(part, res->first, info);
 }
 
+static void
+maybe_handle_pkcs7(const MimeObject& obj, Message::Private& info)
+{
+	if (obj.is_mime_application_pkcs7_mime()) {
+		MimeApplicationPkcs7Mime smime(obj);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wswitch-enum"
+		// CompressedData, CertsOnly, Unknown
+		switch (smime.smime_type()) {
+		case Mu::MimeApplicationPkcs7Mime::SecureMimeType::SignedData:
+			info.flags |= Flags::Signed;
+			break;
+		case Mu::MimeApplicationPkcs7Mime::SecureMimeType::EnvelopedData:
+			info.flags |= Flags::Encrypted;
+			break;
+		default:
+			break;
+		}
+#pragma GCC diagnostic pop
+	}
+}
+
 
 static void
 handle_object(const MimeObject& parent,
@@ -508,23 +530,8 @@ handle_object(const MimeObject& parent,
 		/* FIXME: An encrypted part might be signed at the same time.
 		 *        In that case the signed flag is lost. */
 		info.flags |= Flags::Encrypted;
-	} else if (obj.is_mime_application_pkcs7_mime()) {
-		MimeApplicationPkcs7Mime smime(obj);
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wswitch-enum"
-		// CompressedData, CertsOnly, Unknown
-		switch (smime.smime_type()) {
-		case Mu::MimeApplicationPkcs7Mime::SecureMimeType::SignedData:
-			info.flags |= Flags::Signed;
-			break;
-		case Mu::MimeApplicationPkcs7Mime::SecureMimeType::EnvelopedData:
-			info.flags |= Flags::Encrypted;
-			break;
-		default:
-			break;
-		}
-#pragma GCC diagnostic pop
-	}
+	} else
+		maybe_handle_pkcs7(obj, info);
 }
 
 /**
@@ -548,6 +555,10 @@ process_message(const MimeMessage& mime_msg, const std::string& path,
 			info.flags |= Flags::Unread;
 	}
 
+	// handle top-level
+	if (const auto mpart = mime_msg.mime_part(); mpart)
+		maybe_handle_pkcs7(*mpart, info);
+
 	// parts
 	mime_msg.for_each([&](auto&& parent, auto&& child_obj) {
 		handle_object(parent, child_obj, info);

lib/message/mu-mime-object.hh

@@ -171,9 +171,6 @@ private:
 };
 
 
-
-
-
 
 /**
  * Thin wrapper around a GMimeContentType
@@ -200,6 +197,15 @@ struct MimeContentType: public Object {
 		return g_mime_content_type_is_type(self(), type.c_str(),
 						   subtype.c_str());
 	}
+
+	Option<std::string> parameter(const std::string& name) const noexcept {
+		const char *param{g_mime_content_type_get_parameter(self(), name.c_str())};
+		if (!param || !param[0])
+			return Nothing;
+		else
+			return Some(std::string{param});
+	}
+
 private:
 	GMimeContentType* self() const {
 		return reinterpret_cast<GMimeContentType*>(object());
@@ -929,6 +935,19 @@ public:
 			throw std::runtime_error("not a mime-message");
 	}
 
+	/**
+	 * Get the top-level MIME-part or Nothing if there is none
+	 *
+	 * @return MIME-part of nothing
+	 */
+	Option<MimeObject> mime_part() const noexcept {
+		auto obj = g_mime_message_get_mime_part(self());
+		if (!obj)
+			return Nothing;
+		else
+			return MimeObject{obj};
+	}
+
 	/**
 	 * Make a MimeMessage from a file
 	 *