Implement a permissions API

src/core/obj.js

@@ -15,9 +15,9 @@
 
 import {
   bytesToString, createPromiseCapability, createValidAbsoluteUrl, FormatError,
-  info, InvalidPDFException, isBool, isString, MissingDataException, shadow,
-  stringToPDFString, stringToUTF8String, toRomanNumerals, unreachable, warn,
-  XRefParseException
+  info, InvalidPDFException, isBool, isNum, isString, MissingDataException,
+  PermissionFlag, shadow, stringToPDFString, stringToUTF8String,
+  toRomanNumerals, unreachable, warn, XRefParseException
 } from '../shared/util';
 import {
   Dict, isCmd, isDict, isName, isRef, isRefsEqual, isStream, Ref, RefSet,
@@ -177,6 +177,48 @@ class Catalog {
     return (root.items.length > 0 ? root.items : null);
   }
 
+  get permissions() {
+    let permissions = null;
+    try {
+      permissions = this._readPermissions();
+    } catch (ex) {
+      if (ex instanceof MissingDataException) {
+        throw ex;
+      }
+      warn('Unable to read permissions.');
+    }
+    return shadow(this, 'permissions', permissions);
+  }
+
+  /**
+   * @private
+   */
+  _readPermissions() {
+    const encrypt = this.xref.trailer.get('Encrypt');
+    if (!isDict(encrypt)) {
+      return null;
+    }
+
+    let flags = encrypt.get('P');
+    if (!isNum(flags)) {
+      return null;
+    }
+
+    // PDF integer objects are represented internally in signed 2's complement
+    // form. Therefore, convert the signed decimal integer to a signed 2's
+    // complement binary integer so we can use regular bitwise operations on it.
+    flags += 2 ** 32;
+
+    const permissions = [];
+    for (const key in PermissionFlag) {
+      const value = PermissionFlag[key];
+      if (flags & value) {
+        permissions.push(value);
+      }
+    }
+    return permissions;
+  }
+
   get numPages() {
     const obj = this.toplevelPagesDict.get('Count');
     if (!Number.isInteger(obj)) {

src/core/worker.js

@@ -703,6 +703,10 @@ var WorkerMessageHandler = {
       }
     );
 
+    handler.on('GetPermissions', function(data) {
+      return pdfManager.ensureCatalog('permissions');
+    });
+
     handler.on('GetMetadata',
       function wphSetupGetMetadata(data) {
         return Promise.all([pdfManager.ensureDoc('documentInfo'),

src/display/api.js

@@ -691,6 +691,15 @@ class PDFDocumentProxy {
     return this._transport.getOutline();
   }
 
+  /**
+   * @return {Promise} A promise that is resolved with an {Array} that contains
+   *   the permission flags for the PDF document, or `null` when
+   *   no permissions are present in the PDF file.
+   */
+  getPermissions() {
+    return this._transport.getPermissions();
+  }
+
   /**
    * @return {Promise} A promise that is resolved with an {Object} that has
    *   `info` and `metadata` properties. `info` is an {Object} filled with
@@ -2141,6 +2150,10 @@ class WorkerTransport {
     return this.messageHandler.sendWithPromise('GetOutline', null);
   }
 
+  getPermissions() {
+    return this.messageHandler.sendWithPromise('GetPermissions', null);
+  }
+
   getMetadata() {
     return this.messageHandler.sendWithPromise('GetMetadata', null).
         then((results) => {

src/shared/util.js

@@ -25,6 +25,18 @@ const NativeImageDecoding = {
   DISPLAY: 'display',
 };
 
+// Permission flags from Table 22, Section 7.6.3.2 of the PDF specification.
+const PermissionFlag = {
+  PRINT: 0x04,
+  MODIFY_CONTENTS: 0x08,
+  COPY: 0x10,
+  MODIFY_ANNOTATIONS: 0x20,
+  FILL_INTERACTIVE_FORMS: 0x100,
+  COPY_FOR_ACCESSIBILITY: 0x200,
+  ASSEMBLE: 0x400,
+  PRINT_HIGH_QUALITY: 0x800,
+};
+
 var TextRenderingMode = {
   FILL: 0,
   STROKE: 1,
@@ -1014,6 +1026,7 @@ export {
   NativeImageDecoding,
   PasswordException,
   PasswordResponses,
+  PermissionFlag,
   StreamType,
   TextRenderingMode,
   UnexpectedResponseException,