Add symlink support to ZipFilesystem

dissect/target/filesystems/zip.py

@@ -4,16 +4,21 @@
 import stat
 import zipfile
 from datetime import datetime, timezone
-from typing import BinaryIO, Optional
+from typing import BinaryIO, Iterator
 
 from dissect.util.stream import BufferedStream
 
-from dissect.target.exceptions import FileNotFoundError
+from dissect.target.exceptions import (
+    FileNotFoundError,
+    FilesystemError,
+    IsADirectoryError,
+    NotADirectoryError,
+    NotASymlinkError,
+)
 from dissect.target.filesystem import (
     Filesystem,
     FilesystemEntry,
     VirtualDirectory,
-    VirtualFile,
     VirtualFilesystem,
 )
 from dissect.target.helpers import fsutil
@@ -33,7 +38,7 @@
     def __init__(
         self,
         fh: BinaryIO,
-        base: Optional[str] = None,
+        base: str | None = None,
         *args,
         **kwargs,
     ):
@@ -52,12 +57,7 @@
                 continue
 
             rel_name = fsutil.normpath(mname[len(self.base) :], alt_separator=self.alt_separator)
-
-            # NOTE: Normally we would check here if the member is a symlink or not
-
-            entry_cls = ZipFilesystemDirectoryEntry if member.is_dir() else ZipFilesystemEntry
-            file_entry = entry_cls(self, rel_name, member)
-            self._fs.map_file_entry(rel_name, file_entry)
+            self._fs.map_file_entry(rel_name, ZipFilesystemEntry(self, rel_name, member))
 
     @staticmethod
     def _detect(fh: BinaryIO) -> bool:
@@ -69,60 +69,95 @@
         return self._fs.get(path, relentry=relentry)
 
 
-class ZipFilesystemEntry(VirtualFile):
+# Note: We subclass from VirtualDirectory because VirtualFilesystem is currently only compatible with VirtualDirectory
+# Subclass from VirtualDirectory so we get that compatibility for free, and override the rest to do our own thing
+class ZipFilesystemEntry(VirtualDirectory):
+    fs: ZipFilesystem
+    entry: zipfile.ZipInfo
+
+    def __init__(self, fs: ZipFilesystem, path: str, entry: zipfile.ZipInfo):
+        super().__init__(fs, path)
+        self.entry = entry
+
     def open(self) -> BinaryIO:
-        """Returns file handle (file-like object)."""
+        if self.is_dir():
+            raise IsADirectoryError(self.path)
+
+        if self.is_symlink():
+            return self._resolve().open()
+
         try:
             return BufferedStream(self.fs.zip.open(self.entry), size=self.entry.file_size)
         except Exception:
-            raise FileNotFoundError()
+            raise FileNotFoundError(self.path)
 
-    def readlink(self) -> str:
-        """Read the link if this entry is a symlink. Returns a string."""
-        raise NotImplementedError()
+    def iterdir(self) -> Iterator[str]:
+        if not self.is_dir():
+            raise NotADirectoryError(self.path)
 
-    def readlink_ext(self) -> FilesystemEntry:
-        """Read the link if this entry is a symlink. Returns a filesystem entry."""
-        raise NotImplementedError()
+        entry = self._resolve()
+        if isinstance(entry, ZipFilesystemEntry):
+            yield from super(ZipFilesystemEntry, entry).iterdir()
+        else:
+            yield from entry.iterdir()
 
-    def stat(self, follow_symlinks: bool = True) -> fsutil.stat_result:
-        """Return the stat information of this entry."""
-        return self.lstat()
+    def scandir(self) -> Iterator[FilesystemEntry]:
+        if not self.is_dir():
+            raise NotADirectoryError(self.path)
 
-    def lstat(self) -> fsutil.stat_result:
-        """Return the stat information of the given path, without resolving links."""
-        # ['mode', 'addr', 'dev', 'nlink', 'uid', 'gid', 'size', 'atime', 'mtime', 'ctime']
-        return fsutil.stat_result(
-            [
-                stat.S_IFREG | 0o777,
-                self.entry.header_offset,
-                id(self.fs),
-                1,
-                0,
-                0,
-                self.entry.file_size,
-                0,
-                datetime(*self.entry.date_time, tzinfo=timezone.utc).timestamp(),
-                0,
-            ]
-        )
+        entry = self._resolve()
+        if isinstance(entry, ZipFilesystemEntry):
+            yield from super(ZipFilesystemEntry, entry).scandir()
+        else:
+            yield from entry.scandir()
 
+    def is_dir(self, follow_symlinks: bool = True) -> bool:
+        try:
+            entry = self._resolve(follow_symlinks=follow_symlinks)
+        except FilesystemError:
+            return False
 
-class ZipFilesystemDirectoryEntry(VirtualDirectory):
-    def __init__(self, fs: ZipFilesystem, path: str, entry: zipfile.ZipInfo):
-        super().__init__(fs, path)
-        self.entry = entry
+        if isinstance(entry, ZipFilesystemEntry):
+            return entry.entry.is_dir()
+        return isinstance(entry, VirtualDirectory)
+
+    def is_file(self, follow_symlinks: bool = True) -> bool:
+        try:
+            entry = self._resolve(follow_symlinks=follow_symlinks)
+        except FilesystemError:
+            return False
+
+        if isinstance(entry, ZipFilesystemEntry):
+            return not entry.entry.is_dir()
+        return False
+
+    def is_symlink(self) -> bool:
+        return stat.S_ISLNK(self.entry.external_attr >> 16)
+
+    def readlink(self) -> str:
+        if not self.is_symlink():
+            raise NotASymlinkError()
+        return self.fs.zip.open(self.entry).read().decode()
+
+    def readlink_ext(self) -> FilesystemEntry:
+        return FilesystemEntry.readlink_ext(self)
 
     def stat(self, follow_symlinks: bool = True) -> fsutil.stat_result:
-        """Return the stat information of this entry."""
-        return self.lstat()
+        return self._resolve(follow_symlinks=follow_symlinks).lstat()
 
     def lstat(self) -> fsutil.stat_result:
         """Return the stat information of the given path, without resolving links."""
         # ['mode', 'addr', 'dev', 'nlink', 'uid', 'gid', 'size', 'atime', 'mtime', 'ctime']
+        mode = self.entry.external_attr >> 16
+
+        if self.entry.is_dir() and not stat.S_ISDIR(mode):
+            mode = stat.S_IFDIR | mode
+        elif not self.entry.is_dir() and not stat.S_ISREG(mode):
+            mode = stat.S_IFREG | mode
+
         return fsutil.stat_result(
             [
-                stat.S_IFDIR | 0o777,
+                mode,
                 self.entry.header_offset,
                 id(self.fs),
                 1,

tests/filesystems/test_zip.py

@@ -3,10 +3,15 @@
 
 import pytest
 
+from dissect.target.exceptions import (
+    IsADirectoryError,
+    NotADirectoryError,
+    NotASymlinkError,
+)
 from dissect.target.filesystems.zip import ZipFilesystem, ZipFilesystemEntry
 
 
-def _mkdir(zf, name):
+def _mkdir(zf: zipfile.ZipFile, name: str) -> None:
     # There's no easy way to make a directory with Python zipfile, so copy what zipfile.py does
     zinfo = zipfile.ZipInfo(name)
     zinfo.compress_size = 0
@@ -32,7 +37,7 @@ def _mkdir(zf, name):
         zf.start_dir = zf.fp.tell()
 
 
-def _create_zip(prefix="", zip_dir=True):
+def _create_zip(prefix: str = "", zip_dir: bool = True) -> io.BytesIO:
     buf = io.BytesIO()
     zf = zipfile.ZipFile(buf, "w")
 
@@ -51,34 +56,42 @@ def _create_zip(prefix="", zip_dir=True):
     for i in range(100):
         zf.writestr(f"{prefix}dir/{i}", f"contents {i}")
 
+    symlink = zipfile.ZipInfo(f"{prefix}symlink_dir")
+    symlink.external_attr = 0o120777 << 16
+    zf.writestr(symlink, "dir/")
+
+    symlink = zipfile.ZipInfo(f"{prefix}symlink_file")
+    symlink.external_attr = 0o120777 << 16
+    zf.writestr(symlink, "file_1")
+
     zf.close()
     buf.seek(0)
     return buf
 
 
 @pytest.fixture
-def zip_simple():
-    yield _create_zip()
+def zip_simple() -> io.BytesIO:
+    return _create_zip()
 
 
 @pytest.fixture
-def zip_base():
-    yield _create_zip("base/")
+def zip_base() -> io.BytesIO:
+    return _create_zip("base/")
 
 
 @pytest.fixture
-def zip_relative():
-    yield _create_zip("./", False)
+def zip_relative() -> io.BytesIO:
+    return _create_zip("./", False)
 
 
 @pytest.fixture
-def zip_relative_dir():
-    yield _create_zip("./")
+def zip_relative_dir() -> io.BytesIO:
+    return _create_zip("./")
 
 
 @pytest.fixture
-def zip_virtual_dir():
-    yield _create_zip("", False)
+def zip_virtual_dir() -> io.BytesIO:
+    return _create_zip("", False)
 
 
 @pytest.mark.parametrize(
@@ -91,38 +104,68 @@ def zip_virtual_dir():
         ("zip_virtual_dir", ""),
     ],
 )
-def test_filesystems_zip(obj, base, request):
+def test_filesystems_zip(obj: str, base: str, request: pytest.FixtureRequest) -> None:
     fh = request.getfixturevalue(obj)
 
     assert ZipFilesystem.detect(fh)
 
     fs = ZipFilesystem(fh, base)
     assert isinstance(fs, ZipFilesystem)
 
-    assert len(fs.listdir("/")) == 3
+    assert len(fs.listdir("/")) == 5
 
     assert fs.get("./file_1").open().read() == b"file 1 contents"
     assert fs.get("./file_2").open().read() == b"file 2 contents"
+    assert fs.get("./symlink_file").open().read() == b"file 1 contents"
     assert len(list(fs.glob("./dir/*"))) == 100
+    assert len(list(fs.glob("./symlink_dir/*"))) == 100
 
     zfile = fs.get("./file_1")
     zdir = fs.get("./dir")
+    zsymd = fs.get("./symlink_dir")
+    zsymf = fs.get("./symlink_file")
 
     assert zfile.is_file()
     assert not zfile.is_dir()
     assert not zfile.is_symlink()
 
+    with pytest.raises(NotADirectoryError):
+        list(zfile.iterdir())
+
+    with pytest.raises(NotADirectoryError):
+        next(zfile.scandir())
+
+    with pytest.raises(NotASymlinkError):
+        zfile.readlink()
+
     assert zdir.is_dir()
     assert not zdir.is_file()
     assert not zdir.is_symlink()
+    assert len(list(zdir.iterdir())) == 100
+    assert len(list(zdir.scandir())) == 100
+
+    with pytest.raises(IsADirectoryError):
+        zdir.open()
+
+    assert zsymd.is_dir()
+    assert not zsymd.is_file()
+    assert zsymd.is_symlink()
+    assert zsymd.readlink() == "dir/"
+
+    assert not zsymf.is_dir()
+    assert zsymf.is_file()
+    assert zsymf.is_symlink()
+    assert zsymf.readlink() == "file_1"
 
     file1 = zdir.get("1")
     assert file1.is_file()
     assert not file1.is_dir()
     assert not file1.is_symlink()
     assert file1.open().read() == b"contents 1"
 
-    assert zfile.stat().st_mode == 0o100777
+    assert file1.stat() == zsymd.get("1").stat()
+
+    assert zfile.stat().st_mode == 0o100600
     assert zfile.stat(follow_symlinks=False) == zfile.lstat()
 
     if isinstance(zdir, ZipFilesystemEntry):