Support disabling external file access

3 files changed, 35 insertions, 8 deletions

diff --git a/mammoth/__init__.py b/mammoth/__init__.py
index 27cc580..e8d3a83 100644
--- a/mammoth/__init__.py
+++ b/mammoth/__init__.py
@@ -16,15 +16,28 @@ def convert_to_markdown(*args, **kwargs):
     return convert(*args, output_format="markdown", **kwargs)
 
 
-def convert(fileobj, transform_document=None, id_prefix=None, include_embedded_style_map=_undefined, **kwargs):
+def convert(
+    fileobj,
+    transform_document=None,
+    id_prefix=None,
+    include_embedded_style_map=_undefined,
+    external_file_access=_undefined,
+    **kwargs
+):
     if include_embedded_style_map is _undefined:
         include_embedded_style_map = True
+
     if transform_document is None:
         transform_document = lambda x: x
+
     if include_embedded_style_map:
         kwargs["embedded_style_map"] = read_style_map(fileobj)
+
+    if external_file_access is _undefined:
+        external_file_access = True
+
     return options.read_options(kwargs).bind(lambda convert_options:
-        docx.read(fileobj).map(transform_document).bind(lambda document:
+        docx.read(fileobj, external_file_access=external_file_access).map(transform_document).bind(lambda document:
             conversion.convert_document_element_to_html(
                 document,
                 id_prefix=id_prefix,
@@ -32,7 +45,7 @@ def convert(fileobj, transform_document=None, id_prefix=None, include_embedded_s
             )
         )
     )
-    
+
 
 def extract_raw_text(fileobj):
     return docx.read(fileobj).map(extract_raw_text_from_element)
diff --git a/mammoth/docx/__init__.py b/mammoth/docx/__init__.py
index 3848736..a0576cf 100644
--- a/mammoth/docx/__init__.py
+++ b/mammoth/docx/__init__.py
@@ -19,13 +19,14 @@ from ..zips import open_zip
 _empty_result = results.success([])
 
 
-def read(fileobj):
+def read(fileobj, external_file_access=False):
     zip_file = open_zip(fileobj, "r")
     part_paths = _find_part_paths(zip_file)
     read_part_with_body = _part_with_body_reader(
         getattr(fileobj, "name", None),
         zip_file,
         part_paths=part_paths,
+        external_file_access=external_file_access,
     )
 
     return results.combine([
@@ -134,7 +135,7 @@ def _read_document(zip_file, read_part_with_body, notes, comments, part_paths):
     )
 
 
-def _part_with_body_reader(document_path, zip_file, part_paths):
+def _part_with_body_reader(document_path, zip_file, part_paths, external_file_access):
     content_types = _try_read_entry_or_default(
         zip_file,
         "[Content_Types].xml",
@@ -156,7 +157,10 @@ def _part_with_body_reader(document_path, zip_file, part_paths):
         default=Numbering.EMPTY,
     )
 
-    files = Files(None if document_path is None else os.path.dirname(document_path))
+    files = Files(
+        None if document_path is None else os.path.dirname(document_path),
+        external_file_access=external_file_access,
+    )
 
     def read_part(name, reader, default=_undefined):
         relationships = _read_relationships(zip_file, _find_relationships_path_for(name))
diff --git a/mammoth/docx/files.py b/mammoth/docx/files.py
index 61cf8d5..e26a43f 100644
--- a/mammoth/docx/files.py
+++ b/mammoth/docx/files.py
@@ -11,10 +11,16 @@ except ImportError:
 
 
 class Files(object):
-    def __init__(self, base):
+    def __init__(self, base, external_file_access):
         self._base = base
-    
+        self._external_file_access = external_file_access
+
     def open(self, uri):
+        if not self._external_file_access:
+            raise ExternalFileAccessIsDisabledError(
+                "could not open external image '{0}', external file access is disabled".format(uri)
+            )
+
         try:
             if _is_absolute(uri):
                 return contextlib.closing(urlopen(uri))
@@ -34,3 +40,7 @@ def _is_absolute(url):
 
 class InvalidFileReferenceError(ValueError):
     pass
+
+
+class ExternalFileAccessIsDisabledError(InvalidFileReferenceError):
+    pass