fix(pdf): make encrypt/decrypt/permissions fail honestly instead of silent no-op

src/main.js

@@ -4760,6 +4760,12 @@ ipcMain.on('process-pdf-operation', async (event, data) => {
     });
   }
 });
+// Reports pdf-lib's encryption capability (Task 27) so the renderer can
+// disable the password-protection controls instead of letting the user
+// fill the form only to see the operation fail.
+ipcMain.handle('get-pdf-capabilities', async () => ({
+  passwordProtection: await PDFOperations.pdfEncryptionSupported,
+}));
 ipcMain.on('get-pdf-page-count', async (event, filePath) => {
   try {
     const count = await PDFOperations.getPageCount(filePath);

src/main/PDFBatchOperations.js

@@ -22,10 +22,10 @@
  *     cannot supply (merge takes many inputs in one op; reorder needs each
  *     file's full page order; fillForm's field values differ per file).
  *   - formFields — a read-only query returning data, not a transform.
- *   - encrypt / decrypt / permissions — pdf-lib 1.17.1 (bundled) silently
- *     ignores encryption options in save() and cannot decrypt on load, so a
- *     batch run would either write unprotected files while reporting success
- *     or deterministically fail every file.
+ *   - encrypt / decrypt / permissions — pdf-lib 1.17.1 (bundled) lacks
+ *     encryption support, so since Task 27 these ops fail honestly with an
+ *     "unavailable" result instead of silently writing unprotected files;
+ *     a batch run would deterministically fail every file.
  *
  * @module PDFBatchOperations
  */

src/main/PDFOperations.js

@@ -2,6 +2,30 @@ const fs = require('fs');
 const path = require('path');
 const { PDFDocument, rgb, degrees, StandardFonts } = require('pdf-lib');
 
+// pdf-lib 1.17.1 cannot encrypt: SaveOptions has no userPassword/ownerPassword/
+// permissions fields, so save() silently ignores them and writes an unprotected
+// file, and PDFDocument.load() cannot open password-protected input (verified
+// empirically in Task 22's review). Rather than trusting a pinned version
+// string, probe the installed library once at module load: save a tiny
+// in-memory document with a userPassword and check the raw bytes for an
+// /Encrypt dictionary (which an unencrypted document never contains). A library
+// that supports encryption passes the probe and the password ops re-enable
+// automatically. Probe errors fail closed (treated as unsupported).
+const pdfEncryptionSupported = (async () => {
+  try {
+    const probeDoc = await PDFDocument.create();
+    const probeBytes = await probeDoc.save({ userPassword: 'encryption-capability-probe' });
+    return Buffer.from(probeBytes).includes('/Encrypt');
+  } catch {
+    return false;
+  }
+})();
+
+// Returned by the password ops when the probe reports no encryption support
+// (Task 27): fail honestly instead of silently writing an unprotected file.
+const PDF_ENCRYPTION_UNAVAILABLE_MESSAGE =
+  'Password protection is not available in this build (pdf-lib lacks encryption support).';
+
 function parsePageRanges(rangeString, totalPages) {
   const pages = [];
   const ranges = rangeString.split(',').map((r) => r.trim());
@@ -301,6 +325,9 @@ async function pdfWatermark(data) {
 }
 
 async function pdfEncrypt(data) {
+  if (!(await pdfEncryptionSupported)) {
+    return { success: false, message: PDF_ENCRYPTION_UNAVAILABLE_MESSAGE };
+  }
   try {
     const pdfBytes = fs.readFileSync(data.inputPath);
     const pdf = await PDFDocument.load(pdfBytes);
@@ -335,6 +362,9 @@ async function pdfEncrypt(data) {
 }
 
 async function pdfDecrypt(data) {
+  if (!(await pdfEncryptionSupported)) {
+    return { success: false, message: PDF_ENCRYPTION_UNAVAILABLE_MESSAGE };
+  }
   try {
     const pdfBytes = fs.readFileSync(data.inputPath);
     const pdf = await PDFDocument.load(pdfBytes, { password: data.password });
@@ -352,6 +382,9 @@ async function pdfDecrypt(data) {
 }
 
 async function pdfSetPermissions(data) {
+  if (!(await pdfEncryptionSupported)) {
+    return { success: false, message: PDF_ENCRYPTION_UNAVAILABLE_MESSAGE };
+  }
   try {
     const pdfBytes = fs.readFileSync(data.inputPath);
     const loadOptions = data.currentPassword ? { password: data.currentPassword } : {};
@@ -701,6 +734,8 @@ async function getPageCount(filePath) {
 module.exports = {
   parsePageRanges,
   hexToRgb,
+  pdfEncryptionSupported,
+  PDF_ENCRYPTION_UNAVAILABLE_MESSAGE,
   pdfMerge,
   pdfSplit,
   pdfCompress,

src/preload.js

@@ -86,6 +86,7 @@ const ALLOWED_SEND_CHANNELS = [
   // PDF operations
   'process-pdf-operation',
   'get-pdf-page-count',
+  'get-pdf-capabilities',
   'select-pdf-folder',
   'batch-pdf-operation',
 

src/renderer.js

@@ -3922,8 +3922,41 @@ function updateMergeFilesList() {
   });
 }
 
+// Task 27: pdf-lib 1.17.1 cannot encrypt, so encrypt/decrypt/permissions fail
+// honestly in the main process. Ask main once whether password protection is
+// available and, when it is not, disable the three sections' controls with an
+// explanatory hint instead of letting the user fill the form only to see the
+// operation fail. If the capability query itself fails, leave the controls
+// enabled — main still fails the operation honestly on submit.
+async function applyPDFPasswordProtectionAvailability() {
+  let capabilities;
+  try {
+    capabilities = await ipcRenderer.invoke('get-pdf-capabilities');
+  } catch {
+    return;
+  }
+  if (!capabilities || capabilities.passwordProtection !== false) return;
+
+  const sectionIds = ['pdf-encrypt-section', 'pdf-decrypt-section', 'pdf-permissions-section'];
+  for (const sectionId of sectionIds) {
+    const section = document.getElementById(sectionId);
+    if (!section) continue;
+    section.querySelectorAll('input, select, button').forEach((control) => {
+      control.disabled = true;
+    });
+    const hint = document.createElement('p');
+    hint.className = 'warning-message pdf-unavailable-hint';
+    hint.textContent =
+      'Password protection is not available in this build (pdf-lib lacks encryption support).';
+    section.prepend(hint);
+  }
+}
+
 // PDF Editor Event Listeners
 document.addEventListener('DOMContentLoaded', () => {
+  // Disable password-protection controls when pdf-lib lacks encryption support
+  applyPDFPasswordProtectionAvailability();
+
   // Close PDF Editor Dialog
   const pdfEditorClose = document.getElementById('pdf-editor-dialog-close');
   if (pdfEditorClose) {
@@ -4694,7 +4727,7 @@ ipcRenderer.on('pdf-operation-complete', (event, { success, error, message }) =>
       }
     }, 800);
   } else {
-    showPDFStatus(`Error: ${error || 'PDF operation failed'}`, 'warning');
+    showPDFStatus(`Error: ${error || message || 'PDF operation failed'}`, 'warning');
   }
 });