Properly handle validation of empty attachments

dist/services/SigningService/SigningService.js

@@ -52,11 +52,14 @@ class SigningService {
             const pseudoPlainPartsMessageHash = yield this.preparePartsForSigning([
                 pseudoPlainPart,
             ]);
-            const attachmentsPartsMessageHash = yield this.preparePartsForSigning(hashedAttachments.map((attachment) => attachment.content));
+            let attachmentsPartsSignature = "";
+            if (hashedAttachments.length) {
+                const attachmentsPartsMessageHash = yield this.preparePartsForSigning(hashedAttachments.map((attachment) => attachment.content));
+                attachmentsPartsSignature = yield this.helpers.signRSAExternal(attachmentsPartsMessageHash);
+            }
             const htmlPartsSignature = yield this.helpers.signRSAExternal(htmlPartsMessageHash);
             const plainPartsSignature = yield this.helpers.signRSAExternal(plainPartsMessageHash);
             const pseudoPlainPartsSignature = yield this.helpers.signRSAExternal(pseudoPlainPartsMessageHash);
-            const attachmentsPartsSignature = yield this.helpers.signRSAExternal(attachmentsPartsMessageHash);
             const rabinFingerprints = {
                 htmlPartRabinFingerprint: rka_1.default.getRabinFingerprint(normalizedHTML),
                 plainPartRabinFingerprint: rka_1.default.getRabinFingerprint(normalizedPlain),
@@ -106,11 +109,18 @@ class SigningService {
             const pseudoPlainPartsMessageHash = yield this.preparePartsForSigning([
                 originalPseudoPlain,
             ]);
-            const attachmentsPartsMessageHash = yield this.preparePartsForSigning(hashedAttachments.map((attachment) => attachment.content));
+            let attachmentsPartsValid = true;
+            if (hashedAttachments.length) {
+                const attachmentsPartsMessageHash = yield this.preparePartsForSigning(hashedAttachments.map((attachment) => attachment.content));
+                attachmentsPartsValid = yield this.helpers.cryptoService.verifyRSASignature(publicKeyPEM, Buffer.from(attachmentsPartsMessageHash), Buffer.from(partsSignatures.attachmentsPartsSignature, "base64"));
+            }
+            else if (!hashedAttachments.length &&
+                partsSignatures.attachmentsPartsSignature) {
+                attachmentsPartsValid = false;
+            }
             const htmlPartsValid = yield this.helpers.cryptoService.verifyRSASignature(publicKeyPEM, Buffer.from(htmlPartsMessageHash), Buffer.from(partsSignatures.htmlPartsSignature, "base64"));
             const plainPartsValid = yield this.helpers.cryptoService.verifyRSASignature(publicKeyPEM, Buffer.from(plainPartsMessageHash), Buffer.from(partsSignatures.plainPartsSignature, "base64"));
             const pseudoPlainPartsValid = yield this.helpers.cryptoService.verifyRSASignature(publicKeyPEM, Buffer.from(pseudoPlainPartsMessageHash), Buffer.from(partsSignatures.pseudoPlainPartsSignature, "base64"));
-            const attachmentsPartsValid = yield this.helpers.cryptoService.verifyRSASignature(publicKeyPEM, Buffer.from(attachmentsPartsMessageHash), Buffer.from(partsSignatures.attachmentsPartsSignature, "base64"));
             const severityStateIndex = severityLevels_1.findSeverityStateIndex(htmlPartsValid, plainPartsValid, pseudoPlainPartsValid, attachmentsPartsValid);
             return {
                 htmlPartsSignatureValid: htmlPartsValid,

src/services/SigningService/SigningService.ts

@@ -69,9 +69,17 @@ class SigningService {
     const pseudoPlainPartsMessageHash = await this.preparePartsForSigning([
       pseudoPlainPart,
     ]);
-    const attachmentsPartsMessageHash = await this.preparePartsForSigning(
-      hashedAttachments.map((attachment) => attachment.content)
-    );
+
+    let attachmentsPartsSignature = "";
+    if (hashedAttachments.length) {
+      const attachmentsPartsMessageHash = await this.preparePartsForSigning(
+        hashedAttachments.map((attachment) => attachment.content)
+      );
+
+      attachmentsPartsSignature = await this.helpers.signRSAExternal(
+        attachmentsPartsMessageHash
+      );
+    }
 
     const htmlPartsSignature = await this.helpers.signRSAExternal(
       htmlPartsMessageHash
@@ -82,9 +90,6 @@ class SigningService {
     const pseudoPlainPartsSignature = await this.helpers.signRSAExternal(
       pseudoPlainPartsMessageHash
     );
-    const attachmentsPartsSignature = await this.helpers.signRSAExternal(
-      attachmentsPartsMessageHash
-    );
 
     const rabinFingerprints: PartsRabinFingerprints = {
       htmlPartRabinFingerprint: RKAUtility.getRabinFingerprint(normalizedHTML),
@@ -163,9 +168,24 @@ class SigningService {
     const pseudoPlainPartsMessageHash = await this.preparePartsForSigning([
       originalPseudoPlain,
     ]);
-    const attachmentsPartsMessageHash = await this.preparePartsForSigning(
-      hashedAttachments.map((attachment) => attachment.content)
-    );
+
+    let attachmentsPartsValid = true;
+    if (hashedAttachments.length) {
+      const attachmentsPartsMessageHash = await this.preparePartsForSigning(
+        hashedAttachments.map((attachment) => attachment.content)
+      );
+
+      attachmentsPartsValid = await this.helpers.cryptoService.verifyRSASignature(
+        publicKeyPEM,
+        Buffer.from(attachmentsPartsMessageHash),
+        Buffer.from(partsSignatures.attachmentsPartsSignature, "base64")
+      );
+    } else if (
+      !hashedAttachments.length &&
+      partsSignatures.attachmentsPartsSignature
+    ) {
+      attachmentsPartsValid = false;
+    }
 
     const htmlPartsValid = await this.helpers.cryptoService.verifyRSASignature(
       publicKeyPEM,
@@ -185,12 +205,6 @@ class SigningService {
       Buffer.from(partsSignatures.pseudoPlainPartsSignature, "base64")
     );
 
-    const attachmentsPartsValid = await this.helpers.cryptoService.verifyRSASignature(
-      publicKeyPEM,
-      Buffer.from(attachmentsPartsMessageHash),
-      Buffer.from(partsSignatures.attachmentsPartsSignature, "base64")
-    );
-
     const severityStateIndex = findSeverityStateIndex(
       htmlPartsValid,
       plainPartsValid,