Path traversal issue security fix (#8568)

The path traversal issue in the previously submitted vulnerability
report has been fixed and has been verified and fixed locally.

GHSA-x6ww-pf9m-m73m

### Description

Added a security function to fix a security issue caused by directly
using extractall in zip_file.extractall(output_dir).
This has been verified locally and does not affect previous
functionality.
<img width="1605" height="371" alt="image"
src="https://github.com/user-attachments/assets/2c854a6b-5786-48e4-909e-17015aeceb81"
/>
<img width="1661" height="300" alt="image"
src="https://github.com/user-attachments/assets/3e9dda1a-f961-43dd-92e2-03780973adb1"
/>
Figure 1: Malicious zip file loaded, Figure 2: Normal zip file loaded


### Types of changes
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [ ] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [ ] Quick tests passed locally by running `./runtests.sh --quick
--unittests --disttests`.
- [ ] In-line docstrings updated.
- [ ] Documentation updated, tested `make html` command in the `docs/`
folder.

---------

Signed-off-by: h3rrr <81402797+h3rrr@users.noreply.github.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: YunLiu <55491388+KumoLiu@users.noreply.github.com>
Co-authored-by: Eric Kerfoot <17726042+ericspod@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 5 people

monai/apps/utils.py

@@ -122,6 +122,38 @@ def update_to(self, b: int = 1, bsize: int = 1, tsize: int | None = None) -> Non
         raise e
 
 
+def safe_extract_member(member, extract_to):
+    """Securely verify compressed package member paths to prevent path traversal attacks"""
+    # Get member path (handle different compression formats)
+    if hasattr(member, "filename"):
+        member_path = member.filename  # zipfile
+    elif hasattr(member, "name"):
+        member_path = member.name  # tarfile
+    else:
+        member_path = str(member)
+
+    if hasattr(member, "issym") and member.issym():
+        raise ValueError(f"Symbolic link detected in archive: {member_path}")
+    if hasattr(member, "islnk") and member.islnk():
+        raise ValueError(f"Hard link detected in archive: {member_path}")
+
+    member_path = os.path.normpath(member_path)
+
+    if os.path.isabs(member_path) or ".." in member_path.split(os.sep):
+        raise ValueError(f"Unsafe path detected in archive: {member_path}")
+
+    full_path = os.path.join(extract_to, member_path)
+    full_path = os.path.normpath(full_path)
+
+    extract_root = os.path.realpath(extract_to)
+    target_real = os.path.realpath(full_path)
+    # Ensure the resolved path stays within the extraction root
+    if os.path.commonpath([extract_root, target_real]) != extract_root:
+        raise ValueError(f"Unsafe path: path traversal {member_path}")
+
+    return full_path
+
+
 def check_hash(filepath: PathLike, val: str | None = None, hash_type: str = "md5") -> bool:
     """
     Verify hash signature of specified file.
@@ -242,6 +274,32 @@ def download_url(
         )
 
 
+def _extract_zip(filepath, output_dir):
+    with zipfile.ZipFile(filepath, "r") as zip_file:
+        for member in zip_file.infolist():
+            safe_path = safe_extract_member(member, output_dir)
+            if member.is_dir():
+                continue
+            os.makedirs(os.path.dirname(safe_path), exist_ok=True)
+            with zip_file.open(member) as source:
+                with open(safe_path, "wb") as target:
+                    shutil.copyfileobj(source, target)
+
+
+def _extract_tar(filepath, output_dir):
+    with tarfile.open(filepath, "r") as tar_file:
+        for member in tar_file.getmembers():
+            safe_path = safe_extract_member(member, output_dir)
+            if not member.isfile():
+                continue
+            os.makedirs(os.path.dirname(safe_path), exist_ok=True)
+            source = tar_file.extractfile(member)
+            if source is not None:
+                with source:
+                    with open(safe_path, "wb") as target:
+                        shutil.copyfileobj(source, target)
+
+
 def extractall(
     filepath: PathLike,
     output_dir: PathLike = ".",
@@ -287,14 +345,10 @@ def extractall(
     logger.info(f"Writing into directory: {output_dir}.")
     _file_type = file_type.lower().strip()
     if filepath.name.endswith("zip") or _file_type == "zip":
-        zip_file = zipfile.ZipFile(filepath)
-        zip_file.extractall(output_dir)
-        zip_file.close()
+        _extract_zip(filepath, output_dir)
         return
     if filepath.name.endswith("tar") or filepath.name.endswith("tar.gz") or "tar" in _file_type:
-        tar_file = tarfile.open(filepath)
-        tar_file.extractall(output_dir)
-        tar_file.close()
+        _extract_tar(filepath, output_dir)
         return
     raise NotImplementedError(
         f'Unsupported file type, available options are: ["zip", "tar.gz", "tar"]. name={filepath} type={file_type}.'

tests/apps/test_download_and_extract.py

@@ -11,8 +11,10 @@
 
 from __future__ import annotations
 
+import tarfile
 import tempfile
 import unittest
+import zipfile
 from pathlib import Path
 from urllib.error import ContentTooShortError, HTTPError
 
@@ -66,5 +68,186 @@ def test_default(self, key, file_type):
                 )
 
 
+class TestPathTraversalProtection(unittest.TestCase):
+    """Test cases for path traversal attack protection in extractall function."""
+
+    def test_valid_zip_extraction(self):
+        """Test that valid zip files extract successfully without raising exceptions."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create a valid zip file
+            zip_path = Path(tmp_dir) / "valid_test.zip"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create zip with normal file structure
+            with zipfile.ZipFile(zip_path, "w") as zf:
+                zf.writestr("normal_file.txt", "This is a normal file")
+                zf.writestr("subdir/nested_file.txt", "This is a nested file")
+                zf.writestr("another_file.json", '{"key": "value"}')
+
+            # This should not raise any exception
+            try:
+                extractall(str(zip_path), str(extract_dir))
+
+                # Verify files were extracted correctly
+                self.assertTrue((extract_dir / "normal_file.txt").exists())
+                self.assertTrue((extract_dir / "subdir" / "nested_file.txt").exists())
+                self.assertTrue((extract_dir / "another_file.json").exists())
+
+                # Verify content
+                with open(extract_dir / "normal_file.txt") as f:
+                    self.assertEqual(f.read(), "This is a normal file")
+
+            except Exception as e:
+                self.fail(f"Valid zip extraction should not raise exception: {e}")
+
+    def test_malicious_zip_path_traversal(self):
+        """Test that malicious zip files with path traversal attempts raise ValueError."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create malicious zip file with path traversal
+            zip_path = Path(tmp_dir) / "malicious_test.zip"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create zip with malicious paths
+            with zipfile.ZipFile(zip_path, "w") as zf:
+                # Try to write outside extraction directory
+                zf.writestr("../../../etc/malicious.txt", "malicious content")
+                zf.writestr("normal_file.txt", "normal content")
+
+            # This should raise ValueError due to path traversal detection
+            with self.assertRaises(ValueError) as context:
+                extractall(str(zip_path), str(extract_dir))
+
+            self.assertIn("unsafe path", str(context.exception).lower())
+
+    def test_valid_tar_extraction(self):
+        """Test that valid tar files extract successfully without raising exceptions."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create a valid tar file
+            tar_path = Path(tmp_dir) / "valid_test.tar.gz"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create tar with normal file structure
+            with tarfile.open(tar_path, "w:gz") as tf:
+                # Create temporary files to add to tar
+                temp_file1 = Path(tmp_dir) / "temp1.txt"
+                temp_file1.write_text("This is a normal file")
+                tf.add(temp_file1, arcname="normal_file.txt")
+
+                temp_file2 = Path(tmp_dir) / "temp2.txt"
+                temp_file2.write_text("This is a nested file")
+                tf.add(temp_file2, arcname="subdir/nested_file.txt")
+
+            # This should not raise any exception
+            try:
+                extractall(str(tar_path), str(extract_dir))
+
+                # Verify files were extracted correctly
+                self.assertTrue((extract_dir / "normal_file.txt").exists())
+                self.assertTrue((extract_dir / "subdir" / "nested_file.txt").exists())
+
+                # Verify content
+                with open(extract_dir / "normal_file.txt") as f:
+                    self.assertEqual(f.read(), "This is a normal file")
+
+            except Exception as e:
+                self.fail(f"Valid tar extraction should not raise exception: {e}")
+
+    def test_malicious_tar_path_traversal(self):
+        """Test that malicious tar files with path traversal attempts raise ValueError."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create malicious tar file with path traversal
+            tar_path = Path(tmp_dir) / "malicious_test.tar.gz"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create tar with malicious paths
+            with tarfile.open(tar_path, "w:gz") as tf:
+                # Create a temporary file
+                temp_file = Path(tmp_dir) / "temp.txt"
+                temp_file.write_text("malicious content")
+
+                # Add with malicious path (trying to write outside extraction directory)
+                tf.add(temp_file, arcname="../../../etc/malicious.txt")
+
+            # This should raise ValueError due to path traversal detection
+            with self.assertRaises(ValueError) as context:
+                extractall(str(tar_path), str(extract_dir))
+
+            self.assertIn("unsafe path", str(context.exception).lower())
+
+    def test_absolute_path_protection(self):
+        """Test protection against absolute paths in archives."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create zip with absolute path
+            zip_path = Path(tmp_dir) / "absolute_path_test.zip"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            with zipfile.ZipFile(zip_path, "w") as zf:
+                # Try to use absolute path
+                zf.writestr("/etc/passwd_bad", "malicious content")
+
+            # This should raise ValueError due to absolute path detection
+            with self.assertRaises(ValueError) as context:
+                extractall(str(zip_path), str(extract_dir))
+
+            self.assertIn("unsafe path", str(context.exception).lower())
+
+    def test_malicious_symlink_protection(self):
+        """Test protection against malicious symlinks in tar archives."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create malicious tar file with symlink
+            tar_path = Path(tmp_dir) / "malicious_symlink_test.tar.gz"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create tar with malicious symlink
+            with tarfile.open(tar_path, "w:gz") as tf:
+                temp_file = Path(tmp_dir) / "normal.txt"
+                temp_file.write_text("normal content")
+                tf.add(temp_file, arcname="normal.txt")
+
+                symlink_info = tarfile.TarInfo(name="malicious_symlink.txt")
+                symlink_info.type = tarfile.SYMTYPE
+                symlink_info.linkname = "../../../etc/passwd_bad"
+                symlink_info.size = 0
+                tf.addfile(symlink_info)
+
+            with self.assertRaises(ValueError) as context:
+                extractall(str(tar_path), str(extract_dir))
+
+            error_msg = str(context.exception).lower()
+            self.assertTrue("unsafe path" in error_msg or "symlink" in error_msg)
+
+    def test_malicious_hardlink_protection(self):
+        """Test protection against malicious hard links in tar archives."""
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create malicious tar file with hard link
+            tar_path = Path(tmp_dir) / "malicious_hardlink_test.tar.gz"
+            extract_dir = Path(tmp_dir) / "extract"
+            extract_dir.mkdir()
+
+            # Create tar with malicious hard link
+            with tarfile.open(tar_path, "w:gz") as tf:
+                temp_file = Path(tmp_dir) / "normal.txt"
+                temp_file.write_text("normal content")
+                tf.add(temp_file, arcname="normal.txt")
+
+                hardlink_info = tarfile.TarInfo(name="malicious_hardlink.txt")
+                hardlink_info.type = tarfile.LNKTYPE
+                hardlink_info.linkname = "/etc/passwd_bad"
+                hardlink_info.size = 0
+                tf.addfile(hardlink_info)
+
+            with self.assertRaises(ValueError) as context:
+                extractall(str(tar_path), str(extract_dir))
+
+            error_msg = str(context.exception).lower()
+            self.assertTrue("unsafe path" in error_msg or "hardlink" in error_msg)
+
+
 if __name__ == "__main__":
     unittest.main()