Add signature file for VBA projects (2nd try) (#415)

Add support for signed VBA projects.

#415

docs/src/working_with_macros.dox

@@ -55,6 +55,10 @@ Python xlsxwriter module:
     Utility to extract a vbaProject.bin binary from an
     Excel 2007+ xlsm macro file ...
 
+If the VBA project is signed, `vba_extract.py` also extracts the 
+`vbaProjectSignature.bin` file from the xlsm file. For adding a VBA project 
+signature see @ww_macros_signature.
+
 
 @section ww_macros_adding Adding the VBA macros to a libxlsxwriter file
 
@@ -143,6 +147,27 @@ clarity:
 @note This step is particularly important for macros created with non-English
 versions of Excel.
 
+
+@section ww_macros_signature Adding signed VBA macros to a libxlsxwriter file
+
+VBA macros can be signed in Excel to allow for blocking execution of unsigned 
+macros in certain environments, for example.
+
+The `vba_extract.py utility` can be used to extract the `vbaProject.bin` and
+`vbaProjectSignature.bin` files from an existing xlsm file with signed macros.
+
+To add these files to the libxlsxwriter workbook use the
+`workbook_add_signed_vba_project()` function:
+
+@code
+    workbook_add_signed_vba_project(workbook,
+                                    "./vbaProject.bin", "./vbaProjectSignature.bin");
+@endcode
+
+@note The names don't have to be `vbaProject.bin` and `vbaProjectSignature.bin`.
+Any suitable paths/names for existing VBA project or signature files will do.
+
+
 @section ww_macros_debugging What to do if it doesn't work
 
 The libxlsxwriter test suite contains several tests to ensure that this feature

include/xlsxwriter/workbook.h

@@ -341,6 +341,7 @@ typedef struct lxw_workbook {
     lxw_hash_table *used_dxf_formats;
 
     char *vba_project;
+    char *vba_project_signature;
     char *vba_codename;
 
     lxw_format *default_url_format;
@@ -966,7 +967,7 @@ lxw_error workbook_validate_sheet_name(lxw_workbook *workbook,
  *     workbook_add_vba_project(workbook, "vbaProject.bin");
  * @endcode
  *
- * Only one `vbaProject.bin file` can be added per workbook. The name doesn't
+ * Only one `vbaProject.bin` file can be added per workbook. The name doesn't
  * have to be `vbaProject.bin`. Any suitable path/name for an existing VBA bin
  * file will do.
  *
@@ -985,6 +986,35 @@ lxw_error workbook_validate_sheet_name(lxw_workbook *workbook,
 lxw_error workbook_add_vba_project(lxw_workbook *workbook,
                                    const char *filename);
 
+/**
+ * @brief Add a vbaProject binary and a vbaProjectSignature binary to the Excel
+ * workbook.
+ *
+ * @param workbook    Pointer to a lxw_workbook instance.
+ * @param vba_project The path/filename of the vbaProject.bin file.
+ * @param signature   The path/filename of the vbaProjectSignature.bin file.
+ *
+ * The `%workbook_add_signed_vba_project()` function can be used to add digitally
+ * signed macros or functions to a workbook. The function adds a binary VBA project
+ * file and a binary VBA project signature file that have been extracted from an
+ * existing Excel xlsm file with digitally signed macros:
+ *
+ * @code
+ *     workbook_add_signed_vba_project(workbook, "vbaProject.bin", "vbaProjectSignature.bin");
+ * @endcode
+ *
+ * Only one `vbaProject.bin` file can be added per workbook. The name doesn't
+ * have to be `vbaProject.bin`. Any suitable path/name for an existing VBA bin
+ * file will do. The same applies for `vbaProjectSignature.bin`.
+ *
+ * See also @ref working_with_macros
+ *
+ * @return A #lxw_error.
+ */
+lxw_error workbook_add_signed_vba_project(lxw_workbook *workbook,
+                                          const char *vba_project,
+                                          const char *signature);
+
 /**
  * @brief Set the VBA name for the workbook.
  *

src/packager.c

@@ -31,7 +31,7 @@
  *     | | |____ theme1.xml
  *     | |
  *     | |_____rels
- *     | |____ workbook.xml.rels
+ *     |   |____ workbook.xml.rels
  *     |
  *     |_____rels
  *       |____ .rels
@@ -81,7 +81,7 @@ STATIC lxw_error _write_vml_drawing_rels_file(lxw_packager *self,
 #ifdef _WIN32
 
 /* Silence Windows warning with duplicate symbol for SLIST_ENTRY in local
- * queue.h and widows.h. */
+ * queue.h and windows.h. */
 #undef SLIST_ENTRY
 
 #include <windows.h>
@@ -450,6 +450,35 @@ _add_vba_project(lxw_packager *self)
     return LXW_NO_ERROR;
 }
 
+/*
+ * Write the xl/vbaProjectSignature.bin file.
+ */
+STATIC lxw_error
+_add_vba_project_signature(lxw_packager *self)
+{
+    lxw_workbook *workbook = self->workbook;
+    lxw_error err;
+    FILE *image_stream;
+
+    if (!workbook->vba_project_signature)
+        return LXW_NO_ERROR;
+
+    /* Check that the image file exists and can be opened. */
+    image_stream = lxw_fopen(workbook->vba_project_signature, "rb");
+    if (!image_stream) {
+        LXW_WARN_FORMAT1("Error adding vbaProjectSignature.bin to xlsx file: "
+                         "file doesn't exist or can't be opened: %s.",
+                         workbook->vba_project_signature);
+        return LXW_ERROR_CREATING_TMPFILE;
+    }
+
+    err = _add_file_to_zip(self, image_stream, "xl/vbaProjectSignature.bin");
+    fclose(image_stream);
+    RETURN_ON_ERROR(err);
+
+    return LXW_NO_ERROR;
+}
+
 /*
  * Write the chart files.
  */
@@ -1244,6 +1273,10 @@ _write_content_types_file(lxw_packager *self)
         lxw_ct_add_override(content_types, "/xl/workbook.xml",
                             LXW_APP_DOCUMENT "spreadsheetml.sheet.main+xml");
 
+    if (workbook->vba_project_signature)
+        lxw_ct_add_override(content_types, "/xl/vbaProjectSignature.bin",
+                            "application/vnd.ms-office.vbaProjectSignature");
+
     STAILQ_FOREACH(sheet, workbook->sheets, list_pointers) {
         if (sheet->is_chartsheet) {
             lxw_snprintf(filename, LXW_FILENAME_LENGTH,
@@ -1637,6 +1670,50 @@ _write_vml_drawing_rels_file(lxw_packager *self, lxw_worksheet *worksheet,
     return err;
 }
 
+/*
+ * Write the vbaProject .rels xml file.
+ */
+STATIC lxw_error
+_write_vba_project_rels_file(lxw_packager *self)
+{
+    lxw_relationships *rels;
+    lxw_workbook *workbook = self->workbook;
+    lxw_error err = LXW_NO_ERROR;
+    char *buffer = NULL;
+    size_t buffer_size = 0;
+
+    if (!workbook->vba_project_signature)
+        return LXW_NO_ERROR;
+
+    rels = lxw_relationships_new();
+    if (!rels) {
+        err = LXW_ERROR_MEMORY_MALLOC_FAILED;
+        goto mem_error;
+    }
+
+    rels->file = lxw_get_filehandle(&buffer, &buffer_size, self->tmpdir);
+    if (!rels->file) {
+        err = LXW_ERROR_CREATING_TMPFILE;
+        goto mem_error;
+    }
+
+    lxw_add_ms_package_relationship(rels, "/vbaProjectSignature",
+                                    "vbaProjectSignature.bin");
+
+    lxw_relationships_assemble_xml_file(rels);
+
+    err = _add_to_zip(self, rels->file, &buffer, &buffer_size,
+                      "xl/_rels/vbaProject.bin.rels");
+
+    fclose(rels->file);
+    free(buffer);
+
+mem_error:
+    lxw_free_relationships(rels);
+
+    return err;
+}
+
 /*
  * Write the _rels/.rels xml file.
  */
@@ -1863,6 +1940,12 @@ lxw_create_package(lxw_packager *self)
     error = _add_vba_project(self);
     RETURN_AND_ZIPCLOSE_ON_ERROR(error);
 
+    error = _add_vba_project_signature(self);
+    RETURN_AND_ZIPCLOSE_ON_ERROR(error);
+
+    error = _write_vba_project_rels_file(self);
+    RETURN_AND_ZIPCLOSE_ON_ERROR(error);
+
     error = _write_core_file(self);
     RETURN_AND_ZIPCLOSE_ON_ERROR(error);
 

src/workbook.c

@@ -264,6 +264,7 @@ lxw_workbook_free(lxw_workbook *workbook)
     free(workbook->options.tmpdir);
     free(workbook->ordered_charts);
     free(workbook->vba_project);
+    free(workbook->vba_project_signature);
     free(workbook->vba_codename);
     free(workbook);
 }
@@ -2638,15 +2639,15 @@ workbook_add_vba_project(lxw_workbook *self, const char *filename)
 
     if (!filename) {
         LXW_WARN("workbook_add_vba_project(): "
-                 "filename must be specified.");
+                 "project filename must be specified.");
         return LXW_ERROR_NULL_PARAMETER_IGNORED;
     }
 
     /* Check that the vbaProject file exists and can be opened. */
     filehandle = lxw_fopen(filename, "rb");
     if (!filehandle) {
         LXW_WARN_FORMAT1("workbook_add_vba_project(): "
-                         "file doesn't exist or can't be opened: %s.",
+                         "project file doesn't exist or can't be opened: %s.",
                          filename);
         return LXW_ERROR_PARAMETER_VALIDATION;
     }
@@ -2657,6 +2658,41 @@ workbook_add_vba_project(lxw_workbook *self, const char *filename)
     return LXW_NO_ERROR;
 }
 
+/*
+ * Add a vbaProject binary and a vbaProjectSignature binary to the Excel workbook.
+ */
+lxw_error
+workbook_add_signed_vba_project(lxw_workbook *self,
+                                const char *vba_project,
+                                const char *signature)
+{
+    FILE *filehandle;
+
+    lxw_error error = workbook_add_vba_project(self, vba_project);
+    if (error != LXW_NO_ERROR)
+        return error;
+
+    if (!signature) {
+        LXW_WARN("workbook_add_signed_vba_project(): "
+                 "signature filename must be specified.");
+        return LXW_ERROR_NULL_PARAMETER_IGNORED;
+    }
+
+    /* Check that the vbaProjectSignature file exists and can be opened. */
+    filehandle = lxw_fopen(signature, "rb");
+    if (!filehandle) {
+        LXW_WARN_FORMAT1("workbook_add_signed_vba_project(): "
+                         "signature file doesn't exist or can't be opened: %s.",
+                         signature);
+        return LXW_ERROR_PARAMETER_VALIDATION;
+    }
+    fclose(filehandle);
+
+    self->vba_project_signature = lxw_strdup(signature);
+
+    return LXW_NO_ERROR;
+}
+
 /*
  * Set the VBA name for the workbook.
  */

test/functional/src/test_macro04.c

@@ -0,0 +1,30 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2022, John McNamara, [email protected]
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_macro04.xlsm");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, "Foo");
+
+    workbook_add_signed_vba_project(workbook,
+                                    "images/vbaProject05.bin",
+                                    "images/vbaProject05Signature.bin");
+
+    worksheet_set_column(worksheet, COLS("A:A"), 30, NULL);
+    worksheet_write_string(worksheet, 2, 0, "Press the button to say hello.", NULL);
+
+    lxw_button_options options = { .caption = "Press Me", .macro = "say_hello",
+                                  .width = 80, .height = 30 };
+
+    worksheet_insert_button(worksheet, 2, 1, &options);
+
+    return workbook_close(workbook);
+}

test/functional/test_vba.py

@@ -21,3 +21,6 @@ def test_macro02(self):
 
     def test_macro03(self):
         self.run_exe_test('test_macro03', 'macro03.xlsm')
+
+    def test_macro04(self):
+        self.run_exe_test('test_macro04', 'macro04.xlsm')