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GH-73991: Disallow copying directory into itself via `pathlib.Path.co…
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…py()` (#122924)
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@barneygale
barneygale authored Aug 23, 2024
1 parent bf1b5d3 commit d7ae4dc
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Showing 2 changed files with 140 additions and 14 deletions.
43 changes: 37 additions & 6 deletions Lib/pathlib/_abc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
import functools
import operator
import posixpath
from errno import EINVAL
from glob import _GlobberBase, _no_recurse_symlinks
from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
from pathlib._os import copyfileobj
Expand Down Expand Up @@ -564,14 +565,38 @@ def samefile(self, other_path):
return (st.st_ino == other_st.st_ino and
st.st_dev == other_st.st_dev)

def _samefile_safe(self, other_path):
def _ensure_different_file(self, other_path):
"""
Like samefile(), but returns False rather than raising OSError.
Raise OSError(EINVAL) if both paths refer to the same file.
"""
try:
return self.samefile(other_path)
if not self.samefile(other_path):
return
except (OSError, ValueError):
return False
return
err = OSError(EINVAL, "Source and target are the same file")
err.filename = str(self)
err.filename2 = str(other_path)
raise err

def _ensure_distinct_path(self, other_path):
"""
Raise OSError(EINVAL) if the other path is within this path.
"""
# Note: there is no straightforward, foolproof algorithm to determine
# if one directory is within another (a particularly perverse example
# would be a single network share mounted in one location via NFS, and
# in another location via CIFS), so we simply checks whether the
# other path is lexically equal to, or within, this path.
if self == other_path:
err = OSError(EINVAL, "Source and target are the same path")
elif self in other_path.parents:
err = OSError(EINVAL, "Source path is a parent of target path")
else:
return
err.filename = str(self)
err.filename2 = str(other_path)
raise err

def open(self, mode='r', buffering=-1, encoding=None,
errors=None, newline=None):
Expand Down Expand Up @@ -826,8 +851,7 @@ def _copy_file(self, target):
"""
Copy the contents of this file to the given target.
"""
if self._samefile_safe(target):
raise OSError(f"{self!r} and {target!r} are the same file")
self._ensure_different_file(target)
with self.open('rb') as source_f:
try:
with target.open('wb') as target_f:
Expand All @@ -847,6 +871,13 @@ def copy(self, target, *, follow_symlinks=True, dirs_exist_ok=False,
"""
if not isinstance(target, PathBase):
target = self.with_segments(target)
try:
self._ensure_distinct_path(target)
except OSError as err:
if on_error is None:
raise
on_error(err)
return
stack = [(self, target)]
while stack:
src, dst = stack.pop()
Expand Down
111 changes: 103 additions & 8 deletions Lib/test/test_pathlib/test_pathlib_abc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1501,19 +1501,20 @@ def iterdir(self):
raise FileNotFoundError(errno.ENOENT, "File not found", path)

def mkdir(self, mode=0o777, parents=False, exist_ok=False):
path = str(self.resolve())
if path in self._directories:
path = str(self.parent.resolve() / self.name)
parent = str(self.parent.resolve())
if path in self._directories or path in self._symlinks:
if exist_ok:
return
else:
raise FileExistsError(errno.EEXIST, "File exists", path)
try:
if self.name:
self._directories[str(self.parent)].add(self.name)
self._directories[parent].add(self.name)
self._directories[path] = set()
except KeyError:
if not parents:
raise FileNotFoundError(errno.ENOENT, "File not found", str(self.parent)) from None
raise FileNotFoundError(errno.ENOENT, "File not found", parent) from None
self.parent.mkdir(parents=True, exist_ok=True)
self.mkdir(mode, parents=False, exist_ok=exist_ok)

Expand Down Expand Up @@ -1758,6 +1759,32 @@ def test_copy_symlink_follow_symlinks_false(self):
self.assertTrue(target.is_symlink())
self.assertEqual(source.readlink(), target.readlink())

@needs_symlinks
def test_copy_symlink_to_itself(self):
base = self.cls(self.base)
source = base / 'linkA'
self.assertRaises(OSError, source.copy, source)

@needs_symlinks
def test_copy_symlink_to_existing_symlink(self):
base = self.cls(self.base)
source = base / 'copySource'
target = base / 'copyTarget'
source.symlink_to(base / 'fileA')
target.symlink_to(base / 'dirC')
self.assertRaises(OSError, source.copy, target)
self.assertRaises(OSError, source.copy, target, follow_symlinks=False)

@needs_symlinks
def test_copy_symlink_to_existing_directory_symlink(self):
base = self.cls(self.base)
source = base / 'copySource'
target = base / 'copyTarget'
source.symlink_to(base / 'fileA')
target.symlink_to(base / 'dirC')
self.assertRaises(OSError, source.copy, target)
self.assertRaises(OSError, source.copy, target, follow_symlinks=False)

@needs_symlinks
def test_copy_directory_symlink_follow_symlinks_false(self):
base = self.cls(self.base)
Expand All @@ -1769,6 +1796,42 @@ def test_copy_directory_symlink_follow_symlinks_false(self):
self.assertTrue(target.is_symlink())
self.assertEqual(source.readlink(), target.readlink())

@needs_symlinks
def test_copy_directory_symlink_to_itself(self):
base = self.cls(self.base)
source = base / 'linkB'
self.assertRaises(OSError, source.copy, source)
self.assertRaises(OSError, source.copy, source, follow_symlinks=False)

@needs_symlinks
def test_copy_directory_symlink_into_itself(self):
base = self.cls(self.base)
source = base / 'linkB'
target = base / 'linkB' / 'copyB'
self.assertRaises(OSError, source.copy, target)
self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
self.assertFalse(target.exists())

@needs_symlinks
def test_copy_directory_symlink_to_existing_symlink(self):
base = self.cls(self.base)
source = base / 'copySource'
target = base / 'copyTarget'
source.symlink_to(base / 'dirC')
target.symlink_to(base / 'fileA')
self.assertRaises(FileExistsError, source.copy, target)
self.assertRaises(FileExistsError, source.copy, target, follow_symlinks=False)

@needs_symlinks
def test_copy_directory_symlink_to_existing_directory_symlink(self):
base = self.cls(self.base)
source = base / 'copySource'
target = base / 'copyTarget'
source.symlink_to(base / 'dirC' / 'dirD')
target.symlink_to(base / 'dirC')
self.assertRaises(FileExistsError, source.copy, target)
self.assertRaises(FileExistsError, source.copy, target, follow_symlinks=False)

def test_copy_file_to_existing_file(self):
base = self.cls(self.base)
source = base / 'fileA'
Expand All @@ -1782,8 +1845,7 @@ def test_copy_file_to_existing_directory(self):
base = self.cls(self.base)
source = base / 'fileA'
target = base / 'dirA'
with self.assertRaises(OSError):
source.copy(target)
self.assertRaises(OSError, source.copy, target)

@needs_symlinks
def test_copy_file_to_existing_symlink(self):
Expand Down Expand Up @@ -1823,6 +1885,13 @@ def test_copy_file_empty(self):
self.assertTrue(target.exists())
self.assertEqual(target.read_bytes(), b'')

def test_copy_file_to_itself(self):
base = self.cls(self.base)
source = base / 'empty'
source.write_bytes(b'')
self.assertRaises(OSError, source.copy, source)
self.assertRaises(OSError, source.copy, source, follow_symlinks=False)

def test_copy_dir_simple(self):
base = self.cls(self.base)
source = base / 'dirC'
Expand Down Expand Up @@ -1909,6 +1978,28 @@ def test_copy_dir_to_existing_directory_dirs_exist_ok(self):
self.assertTrue(target.joinpath('fileC').read_text(),
"this is file C\n")

def test_copy_dir_to_itself(self):
base = self.cls(self.base)
source = base / 'dirC'
self.assertRaises(OSError, source.copy, source)
self.assertRaises(OSError, source.copy, source, follow_symlinks=False)

def test_copy_dir_to_itself_on_error(self):
base = self.cls(self.base)
source = base / 'dirC'
errors = []
source.copy(source, on_error=errors.append)
self.assertEqual(len(errors), 1)
self.assertIsInstance(errors[0], OSError)

def test_copy_dir_into_itself(self):
base = self.cls(self.base)
source = base / 'dirC'
target = base / 'dirC' / 'dirD' / 'copyC'
self.assertRaises(OSError, source.copy, target)
self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
self.assertFalse(target.exists())

def test_copy_missing_on_error(self):
base = self.cls(self.base)
source = base / 'foo'
Expand Down Expand Up @@ -2876,8 +2967,12 @@ def readlink(self):
raise FileNotFoundError(errno.ENOENT, "File not found", path)

def symlink_to(self, target, target_is_directory=False):
self._directories[str(self.parent)].add(self.name)
self._symlinks[str(self)] = str(target)
path = str(self.parent.resolve() / self.name)
parent = str(self.parent.resolve())
if path in self._symlinks:
raise FileExistsError(errno.EEXIST, "File exists", path)
self._directories[parent].add(self.name)
self._symlinks[path] = str(target)


class DummyPathWithSymlinksTest(DummyPathTest):
Expand Down

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