qt: Fix crash in files with malformed signatures

For signatures we need the formwidget, so even if they don't have the
Subtype Widget create one when asked for signatures in the document

Fixes KDE bug #433909

4 files changed, 16 insertions, 2 deletions

diff --git a/poppler/Form.cc b/poppler/Form.cc
index 9937eefd..4d42aedf 100644
--- a/poppler/Form.cc
+++ b/poppler/Form.cc
@@ -1975,6 +1975,18 @@ void FormFieldSignature::setCertificateInfo(std::unique_ptr<X509CertificateInfo>
     certificate_info.swap(certInfo);
 }
 
+FormWidget *FormFieldSignature::getCreateWidget()
+{
+    ::FormWidget *fw = getWidget(0);
+    if (!fw) {
+        error(errSyntaxError, 0, "FormFieldSignature: was asked for widget and didn't had one, creating it");
+        _createWidget(&obj, ref);
+        fw = getWidget(0);
+        fw->createWidgetAnnotation();
+    }
+    return fw;
+}
+
 void FormFieldSignature::parseInfo()
 {
     if (!obj.isDict())
diff --git a/poppler/Form.h b/poppler/Form.h
index dcf89760..247fc141 100644
--- a/poppler/Form.h
+++ b/poppler/Form.h
@@ -617,6 +617,8 @@ public:
 
     void setCertificateInfo(std::unique_ptr<X509CertificateInfo> &);
 
+    FormWidget *getCreateWidget();
+
 private:
     void parseInfo();
     void hashSignedDataBlock(SignatureHandler *handler, Goffset block_len);
diff --git a/qt5/src/poppler-document.cc b/qt5/src/poppler-document.cc
index 0a2a6ce4..c7d38be2 100644
--- a/qt5/src/poppler-document.cc
+++ b/qt5/src/poppler-document.cc
@@ -825,7 +825,7 @@ QVector<FormFieldSignature *> Document::signatures() const
     const std::vector<::FormFieldSignature *> pSignatures = m_doc->doc->getSignatureFields();
 
     for (::FormFieldSignature *pSignature : pSignatures) {
-        ::FormWidget *fw = pSignature->getWidget(0);
+        ::FormWidget *fw = pSignature->getCreateWidget();
         ::Page *p = m_doc->doc->getPage(fw->getWidgetAnnotation()->getPageNum());
         result.append(new FormFieldSignature(m_doc, p, static_cast<FormWidgetSignature *>(fw)));
     }
diff --git a/qt6/src/poppler-document.cc b/qt6/src/poppler-document.cc
index 1a13d46d..150cca0a 100644
--- a/qt6/src/poppler-document.cc
+++ b/qt6/src/poppler-document.cc
@@ -807,7 +807,7 @@ QVector<FormFieldSignature *> Document::signatures() const
     const std::vector<::FormFieldSignature *> pSignatures = m_doc->doc->getSignatureFields();
 
     for (::FormFieldSignature *pSignature : pSignatures) {
-        ::FormWidget *fw = pSignature->getWidget(0);
+        ::FormWidget *fw = pSignature->getCreateWidget();
         ::Page *p = m_doc->doc->getPage(fw->getWidgetAnnotation()->getPageNum());
         result.append(new FormFieldSignature(m_doc, p, static_cast<FormWidgetSignature *>(fw)));
     }