Improve AcroForm/XFA form type detection

src/core/annotation.js

@@ -51,7 +51,7 @@ class AnnotationFactory {
    *   instance.
    */
   static create(xref, ref, pdfManager, idFactory) {
-    return pdfManager.ensureDoc("acroForm").then(acroForm => {
+    return pdfManager.ensureCatalog("acroForm").then(acroForm => {
       return pdfManager.ensure(this, "_create", [
         xref,
         ref,

src/core/document.js

@@ -552,6 +552,7 @@ class PDFDocument {
     this.stream = stream;
     this.xref = new XRef(stream, pdfManager);
     this._pagePromises = [];
+    this._version = null;
 
     const idCounters = {
       font: 0,
@@ -572,42 +573,15 @@ class PDFDocument {
   }
 
   parse(recoveryMode) {
-    this.setup(recoveryMode);
-
-    const version = this.catalog.catDict.get("Version");
-    if (isName(version)) {
-      this.pdfFormatVersion = version.name;
-    }
-
-    // Check if AcroForms are present in the document.
-    try {
-      this.acroForm = this.catalog.catDict.get("AcroForm");
-      if (this.acroForm) {
-        this.xfa = this.acroForm.get("XFA");
-        const fields = this.acroForm.get("Fields");
-        if ((!Array.isArray(fields) || fields.length === 0) && !this.xfa) {
-          this.acroForm = null; // No fields and no XFA, so it's not a form.
-        }
-      }
-    } catch (ex) {
-      if (ex instanceof MissingDataException) {
-        throw ex;
-      }
-      info("Cannot fetch AcroForm entry; assuming no AcroForms are present");
-      this.acroForm = null;
-    }
+    this.xref.parse(recoveryMode);
+    this.catalog = new Catalog(this.pdfManager, this.xref);
 
-    // Check if a Collection dictionary is present in the document.
-    try {
-      const collection = this.catalog.catDict.get("Collection");
-      if (isDict(collection) && collection.size > 0) {
-        this.collection = collection;
-      }
-    } catch (ex) {
-      if (ex instanceof MissingDataException) {
-        throw ex;
-      }
-      info("Cannot fetch Collection dictionary.");
+    // The `checkHeader` method is called before this method and parses the
+    // version from the header. The specification states in section 7.5.2
+    // that the version from the catalog, if present, should overwrite the
+    // version from the header.
+    if (this.catalog.version) {
+      this._version = this.catalog.version;
     }
   }
 
@@ -693,27 +667,85 @@ class PDFDocument {
       }
       version += String.fromCharCode(ch);
     }
-    if (!this.pdfFormatVersion) {
+    if (!this._version) {
       // Remove the "%PDF-" prefix.
-      this.pdfFormatVersion = version.substring(5);
+      this._version = version.substring(5);
     }
   }
 
   parseStartXRef() {
     this.xref.setStartXRef(this.startXRef);
   }
 
-  setup(recoveryMode) {
-    this.xref.parse(recoveryMode);
-    this.catalog = new Catalog(this.pdfManager, this.xref);
-  }
-
   get numPages() {
     const linearization = this.linearization;
     const num = linearization ? linearization.numPages : this.catalog.numPages;
     return shadow(this, "numPages", num);
   }
 
+  /**
+   * @private
+   */
+  _hasOnlyDocumentSignatures(fields, recursionDepth = 0) {
+    const RECURSION_LIMIT = 10;
+    return fields.every(field => {
+      field = this.xref.fetchIfRef(field);
+      if (field.has("Kids")) {
+        if (++recursionDepth > RECURSION_LIMIT) {
+          warn("_hasOnlyDocumentSignatures: maximum recursion depth reached");
+          return false;
+        }
+        return this._hasOnlyDocumentSignatures(
+          field.get("Kids"),
+          recursionDepth
+        );
+      }
+      const isSignature = isName(field.get("FT"), "Sig");
+      const rectangle = field.get("Rect");
+      const isInvisible =
+        Array.isArray(rectangle) && rectangle.every(value => value === 0);
+      return isSignature && isInvisible;
+    });
+  }
+
+  get formInfo() {
+    const formInfo = { hasAcroForm: false, hasXfa: false };
+    const acroForm = this.catalog.acroForm;
+    if (!acroForm) {
+      return shadow(this, "formInfo", formInfo);
+    }
+
+    try {
+      // The document contains XFA data if the `XFA` entry is a non-empty
+      // array or stream.
+      const xfa = acroForm.get("XFA");
+      const hasXfa =
+        (Array.isArray(xfa) && xfa.length > 0) ||
+        (isStream(xfa) && !xfa.isEmpty);
+      formInfo.hasXfa = hasXfa;
+
+      // The document contains AcroForm data if the `Fields` entry is a
+      // non-empty array and it doesn't consist of only document signatures.
+      // This second check is required for files that don't actually contain
+      // AcroForm data (only XFA data), but that use the `Fields` entry to
+      // store (invisible) document signatures. This can be detected using
+      // the first bit of the `SigFlags` integer (see Table 219 in the
+      // specification).
+      const fields = acroForm.get("Fields");
+      const hasFields = Array.isArray(fields) && fields.length > 0;
+      const sigFlags = acroForm.get("SigFlags");
+      const hasOnlyDocumentSignatures =
+        !!(sigFlags & 0x1) && this._hasOnlyDocumentSignatures(fields);
+      formInfo.hasAcroForm = hasFields && !hasOnlyDocumentSignatures;
+    } catch (ex) {
+      if (ex instanceof MissingDataException) {
+        throw ex;
+      }
+      info("Cannot fetch form information.");
+    }
+    return shadow(this, "formInfo", formInfo);
+  }
+
   get documentInfo() {
     const DocumentInfoValidators = {
       Title: isString,
@@ -727,7 +759,7 @@ class PDFDocument {
       Trapped: isName,
     };
 
-    let version = this.pdfFormatVersion;
+    let version = this._version;
     if (
       typeof version !== "string" ||
       !PDF_HEADER_VERSION_REGEXP.test(version)
@@ -739,9 +771,9 @@ class PDFDocument {
     const docInfo = {
       PDFFormatVersion: version,
       IsLinearized: !!this.linearization,
-      IsAcroFormPresent: !!this.acroForm,
-      IsXFAPresent: !!this.xfa,
-      IsCollectionPresent: !!this.collection,
+      IsAcroFormPresent: this.formInfo.hasAcroForm,
+      IsXFAPresent: this.formInfo.hasXfa,
+      IsCollectionPresent: !!this.catalog.collection,
     };
 
     let infoDict;

src/core/obj.js

@@ -65,8 +65,8 @@ class Catalog {
     this.pdfManager = pdfManager;
     this.xref = xref;
 
-    this.catDict = xref.getCatalogObj();
-    if (!isDict(this.catDict)) {
+    this._catDict = xref.getCatalogObj();
+    if (!isDict(this._catDict)) {
       throw new FormatError("Catalog object is not a dictionary.");
     }
 
@@ -76,8 +76,48 @@ class Catalog {
     this.pageKidsCountCache = new RefSetCache();
   }
 
+  get version() {
+    const version = this._catDict.get("Version");
+    if (!isName(version)) {
+      return shadow(this, "version", null);
+    }
+    return shadow(this, "version", version.name);
+  }
+
+  get collection() {
+    let collection = null;
+    try {
+      const obj = this._catDict.get("Collection");
+      if (isDict(obj) && obj.size > 0) {
+        collection = obj;
+      }
+    } catch (ex) {
+      if (ex instanceof MissingDataException) {
+        throw ex;
+      }
+      info("Cannot fetch Collection entry; assuming no collection is present.");
+    }
+    return shadow(this, "collection", collection);
+  }
+
+  get acroForm() {
+    let acroForm = null;
+    try {
+      const obj = this._catDict.get("AcroForm");
+      if (isDict(obj) && obj.size > 0) {
+        acroForm = obj;
+      }
+    } catch (ex) {
+      if (ex instanceof MissingDataException) {
+        throw ex;
+      }
+      info("Cannot fetch AcroForm entry; assuming no forms are present.");
+    }
+    return shadow(this, "acroForm", acroForm);
+  }
+
   get metadata() {
-    const streamRef = this.catDict.getRaw("Metadata");
+    const streamRef = this._catDict.getRaw("Metadata");
     if (!isRef(streamRef)) {
       return shadow(this, "metadata", null);
     }
@@ -112,7 +152,7 @@ class Catalog {
   }
 
   get toplevelPagesDict() {
-    const pagesObj = this.catDict.get("Pages");
+    const pagesObj = this._catDict.get("Pages");
     if (!isDict(pagesObj)) {
       throw new FormatError("Invalid top-level pages dictionary.");
     }
@@ -136,7 +176,7 @@ class Catalog {
    * @private
    */
   _readDocumentOutline() {
-    let obj = this.catDict.get("Outlines");
+    let obj = this._catDict.get("Outlines");
     if (!isDict(obj)) {
       return null;
     }
@@ -257,7 +297,7 @@ class Catalog {
   get optionalContentConfig() {
     let config = null;
     try {
-      const properties = this.catDict.get("OCProperties");
+      const properties = this._catDict.get("OCProperties");
       if (!properties) {
         return shadow(this, "optionalContentConfig", null);
       }
@@ -370,12 +410,12 @@ class Catalog {
    * @private
    */
   _readDests() {
-    const obj = this.catDict.get("Names");
+    const obj = this._catDict.get("Names");
     if (obj && obj.has("Dests")) {
       return new NameTree(obj.getRaw("Dests"), this.xref);
-    } else if (this.catDict.has("Dests")) {
+    } else if (this._catDict.has("Dests")) {
       // Simple destination dictionary.
-      return this.catDict.get("Dests");
+      return this._catDict.get("Dests");
     }
     return undefined;
   }
@@ -397,7 +437,7 @@ class Catalog {
    * @private
    */
   _readPageLabels() {
-    const obj = this.catDict.getRaw("PageLabels");
+    const obj = this._catDict.getRaw("PageLabels");
     if (!obj) {
       return null;
     }
@@ -497,7 +537,7 @@ class Catalog {
   }
 
   get pageLayout() {
-    const obj = this.catDict.get("PageLayout");
+    const obj = this._catDict.get("PageLayout");
     // Purposely use a non-standard default value, rather than 'SinglePage', to
     // allow differentiating between `undefined` and /SinglePage since that does
     // affect the Scroll mode (continuous/non-continuous) used in Adobe Reader.
@@ -518,7 +558,7 @@ class Catalog {
   }
 
   get pageMode() {
-    const obj = this.catDict.get("PageMode");
+    const obj = this._catDict.get("PageMode");
     let pageMode = "UseNone"; // Default value.
 
     if (isName(obj)) {
@@ -556,7 +596,7 @@ class Catalog {
       NumCopies: Number.isInteger,
     };
 
-    const obj = this.catDict.get("ViewerPreferences");
+    const obj = this._catDict.get("ViewerPreferences");
     let prefs = null;
 
     if (isDict(obj)) {
@@ -681,7 +721,7 @@ class Catalog {
    * NOTE: "JavaScript" actions are, for now, handled by `get javaScript` below.
    */
   get openAction() {
-    const obj = this.catDict.get("OpenAction");
+    const obj = this._catDict.get("OpenAction");
     let openAction = null;
 
     if (isDict(obj)) {
@@ -714,7 +754,7 @@ class Catalog {
   }
 
   get attachments() {
-    const obj = this.catDict.get("Names");
+    const obj = this._catDict.get("Names");
     let attachments = null;
 
     if (obj && obj.has("EmbeddedFiles")) {
@@ -732,7 +772,7 @@ class Catalog {
   }
 
   get javaScript() {
-    const obj = this.catDict.get("Names");
+    const obj = this._catDict.get("Names");
 
     let javaScript = null;
     function appendIfJavaScriptDict(jsDict) {
@@ -768,7 +808,7 @@ class Catalog {
     }
 
     // Append OpenAction "JavaScript" actions to the JavaScript array.
-    const openAction = this.catDict.get("OpenAction");
+    const openAction = this._catDict.get("OpenAction");
     if (isDict(openAction) && isName(openAction.get("S"), "JavaScript")) {
       appendIfJavaScriptDict(openAction);
     }
@@ -813,7 +853,7 @@ class Catalog {
 
   getPageDict(pageIndex) {
     const capability = createPromiseCapability();
-    const nodesToVisit = [this.catDict.getRaw("Pages")];
+    const nodesToVisit = [this._catDict.getRaw("Pages")];
     const visitedNodes = new RefSet();
     const xref = this.xref,
       pageKidsCountCache = this.pageKidsCountCache;

test/unit/annotation_spec.js

@@ -41,7 +41,9 @@ describe("annotation", function () {
     constructor(params) {
       this.docBaseUrl = params.docBaseUrl || null;
       this.pdfDocument = {
-        acroForm: new Dict(),
+        catalog: {
+          acroForm: new Dict(),
+        },
       };
     }
 
@@ -56,8 +58,8 @@ describe("annotation", function () {
       });
     }
 
-    ensureDoc(prop, args) {
-      return this.ensure(this.pdfDocument, prop, args);
+    ensureCatalog(prop, args) {
+      return this.ensure(this.pdfDocument.catalog, prop, args);
     }
   }