191 lines
7.3 KiB
Python
191 lines
7.3 KiB
Python
import os
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import pathlib
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from django.core.exceptions import SuspiciousFileOperation
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from django.core.files import File
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from django.core.files.utils import validate_file_name
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from django.utils.crypto import get_random_string
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from django.utils.text import get_valid_filename
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class Storage:
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"""
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A base storage class, providing some default behaviors that all other
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storage systems can inherit or override, as necessary.
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"""
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# The following methods represent a public interface to private methods.
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# These shouldn't be overridden by subclasses unless absolutely necessary.
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def open(self, name, mode="rb"):
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"""Retrieve the specified file from storage."""
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return self._open(name, mode)
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def save(self, name, content, max_length=None):
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"""
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Save new content to the file specified by name. The content should be
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a proper File object or any Python file-like object, ready to be read
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from the beginning.
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"""
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# Get the proper name for the file, as it will actually be saved.
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if name is None:
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name = content.name
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if not hasattr(content, "chunks"):
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content = File(content, name)
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name = self.get_available_name(name, max_length=max_length)
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name = self._save(name, content)
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# Ensure that the name returned from the storage system is still valid.
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validate_file_name(name, allow_relative_path=True)
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return name
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# These methods are part of the public API, with default implementations.
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def get_valid_name(self, name):
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"""
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Return a filename, based on the provided filename, that's suitable for
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use in the target storage system.
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"""
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return get_valid_filename(name)
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def get_alternative_name(self, file_root, file_ext):
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"""
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Return an alternative filename, by adding an underscore and a random 7
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character alphanumeric string (before the file extension, if one
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exists) to the filename.
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"""
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return "%s_%s%s" % (file_root, get_random_string(7), file_ext)
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def get_available_name(self, name, max_length=None):
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"""
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Return a filename that's free on the target storage system and
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available for new content to be written to.
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"""
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name = str(name).replace("\\", "/")
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dir_name, file_name = os.path.split(name)
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if ".." in pathlib.PurePath(dir_name).parts:
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raise SuspiciousFileOperation(
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"Detected path traversal attempt in '%s'" % dir_name
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)
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validate_file_name(file_name)
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file_root, file_ext = os.path.splitext(file_name)
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# If the filename already exists, generate an alternative filename
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# until it doesn't exist.
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# Truncate original name if required, so the new filename does not
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# exceed the max_length.
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while self.exists(name) or (max_length and len(name) > max_length):
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# file_ext includes the dot.
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name = os.path.join(
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dir_name, self.get_alternative_name(file_root, file_ext)
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)
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if max_length is None:
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continue
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# Truncate file_root if max_length exceeded.
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truncation = len(name) - max_length
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if truncation > 0:
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file_root = file_root[:-truncation]
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# Entire file_root was truncated in attempt to find an
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# available filename.
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if not file_root:
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raise SuspiciousFileOperation(
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'Storage can not find an available filename for "%s". '
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"Please make sure that the corresponding file field "
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'allows sufficient "max_length".' % name
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)
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name = os.path.join(
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dir_name, self.get_alternative_name(file_root, file_ext)
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)
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return name
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def generate_filename(self, filename):
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"""
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Validate the filename by calling get_valid_name() and return a filename
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to be passed to the save() method.
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"""
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filename = str(filename).replace("\\", "/")
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# `filename` may include a path as returned by FileField.upload_to.
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dirname, filename = os.path.split(filename)
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if ".." in pathlib.PurePath(dirname).parts:
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raise SuspiciousFileOperation(
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"Detected path traversal attempt in '%s'" % dirname
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)
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return os.path.normpath(os.path.join(dirname, self.get_valid_name(filename)))
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def path(self, name):
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"""
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Return a local filesystem path where the file can be retrieved using
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Python's built-in open() function. Storage systems that can't be
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accessed using open() should *not* implement this method.
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"""
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raise NotImplementedError("This backend doesn't support absolute paths.")
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# The following methods form the public API for storage systems, but with
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# no default implementations. Subclasses must implement *all* of these.
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def delete(self, name):
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"""
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Delete the specified file from the storage system.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide a delete() method"
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)
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def exists(self, name):
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"""
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Return True if a file referenced by the given name already exists in the
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storage system, or False if the name is available for a new file.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide an exists() method"
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)
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def listdir(self, path):
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"""
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List the contents of the specified path. Return a 2-tuple of lists:
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the first item being directories, the second item being files.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide a listdir() method"
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)
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def size(self, name):
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"""
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Return the total size, in bytes, of the file specified by name.
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"""
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raise NotImplementedError("subclasses of Storage must provide a size() method")
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def url(self, name):
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"""
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Return an absolute URL where the file's contents can be accessed
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directly by a web browser.
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"""
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raise NotImplementedError("subclasses of Storage must provide a url() method")
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def get_accessed_time(self, name):
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"""
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Return the last accessed time (as a datetime) of the file specified by
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name. The datetime will be timezone-aware if USE_TZ=True.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide a get_accessed_time() method"
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)
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def get_created_time(self, name):
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"""
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Return the creation time (as a datetime) of the file specified by name.
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The datetime will be timezone-aware if USE_TZ=True.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide a get_created_time() method"
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)
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def get_modified_time(self, name):
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"""
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Return the last modified time (as a datetime) of the file specified by
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name. The datetime will be timezone-aware if USE_TZ=True.
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"""
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raise NotImplementedError(
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"subclasses of Storage must provide a get_modified_time() method"
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)
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