Add QPDFAcroFormDocumentHelper::disableDigitalSignatures

2 files changed, 27 insertions, 0 deletions

diff --git a/include/qpdf/QPDFAcroFormDocumentHelper.hh b/include/qpdf/QPDFAcroFormDocumentHelper.hh
index 8be4d069..f9ad0091 100644
--- a/include/qpdf/QPDFAcroFormDocumentHelper.hh
+++ b/include/qpdf/QPDFAcroFormDocumentHelper.hh
@@ -163,6 +163,11 @@ class QPDFAcroFormDocumentHelper: public QPDFDocumentHelper
     QPDF_DLL
     void generateAppearancesIfNeeded();
 
+    // Disable Digital Signature Fields. Remove all digital signature fields from the document,
+    // leaving any annotation showing the content of the field intact.
+    QPDF_DLL
+    void disableDigitalSignatures();
+
     // Note: this method works on all annotations, not just ones with associated fields. For each
     // annotation in old_annots, apply the given transformation matrix to create a new annotation.
     // New annotations are appended to new_annots. If the annotation is associated with a form
diff --git a/libqpdf/QPDFAcroFormDocumentHelper.cc b/libqpdf/QPDFAcroFormDocumentHelper.cc
index f2daa0c7..5fdd20ba 100644
--- a/libqpdf/QPDFAcroFormDocumentHelper.cc
+++ b/libqpdf/QPDFAcroFormDocumentHelper.cc
@@ -416,6 +416,28 @@ QPDFAcroFormDocumentHelper::generateAppearancesIfNeeded()
 }
 
 void
+QPDFAcroFormDocumentHelper::disableDigitalSignatures()
+{
+    std::set<QPDFObjGen> to_remove;
+    auto fields = getFormFields();
+    for (auto& f: fields) {
+        auto ft = f.getFieldType();
+        if (ft == "/Sig") {
+            auto oh = f.getObjectHandle();
+            to_remove.insert(oh.getObjGen());
+            // Make this no longer a form field. If it's also an annotation, the annotation will
+            // survive. If it's only a field and is no longer referenced, it will disappear.
+            oh.removeKey("/FT");
+            // Remove fields that are specific to signature fields.
+            oh.removeKey("/V");
+            oh.removeKey("/SV");
+            oh.removeKey("/Lock");
+        }
+    }
+    removeFormFields(to_remove);
+}
+
+void
 QPDFAcroFormDocumentHelper::adjustInheritedFields(
     QPDFObjectHandle obj,
     bool override_da,