fix(extractor): stronger implementation of fix_extracted_directory.

1. recursive walking

We re-implemented fix_extracted_directory using os.listdir(). We do not
rely on os.walk because we need to fix the permissions recursively in
order to gain visibility into child directories. If we were to use
os.walk() on a directory containing directories on which we don't have
read permissions would mean we would not fix the content of those
directories.

2. handling ENAMETOOLONG

fix_extracted_directory now handles ENAMETOOLONG exception triggered on
symlinks with overly long target names. When that happens, we skip over
the file.

3. handling concurrent deletion

Someone (or something) can delete an object (file, directory, link, ...)
from the extraction directory as we are walking through it. We're also
handling such cases now so we don't raise FileNotFoundError.

Author: qkaiser

tests/integration/filesystem/extfs/__input__/f_badsymlinks.img

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:f5db6b45d5ce63976001aba342e9928dff1f75ee2ce3033269ca2fcaf5b9f80a
+size 1048576

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/attr_fastlink

@@ -0,0 +1 @@
+foo

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/attr_link

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/bad_link_size

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/high_link

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/long_fastlink

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaҾ

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/long_link

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

tests/integration/filesystem/extfs/__output__/f_badsymlinks.img_extract/lost+found/.gitkeep

@@ -1,4 +1,5 @@
 """File extraction related functions."""
+import errno
 import os
 from pathlib import Path
 
@@ -91,12 +92,24 @@ def fix_symlink(path: Path, outdir: Path, task_result: TaskResult) -> Path:
 
 
 def fix_extracted_directory(outdir: Path, task_result: TaskResult):
+    def _fix_extracted_directory(directory: Path):
+        if not directory.exists():
+            return
+        for path in (directory / p for p in os.listdir(directory)):
+            try:
+                fix_permission(path)
+                if path.is_symlink():
+                    fix_symlink(path, outdir, task_result)
+                    continue
+                if path.is_dir():
+                    _fix_extracted_directory(path)
+            except OSError as e:
+                if e.errno == errno.ENAMETOOLONG:
+                    continue
+                raise e from None
+
     fix_permission(outdir)
-    for path in outdir.rglob("*"):
-        if path.is_symlink():
-            fix_symlink(path, outdir, task_result)
-        else:
-            fix_permission(path)
+    _fix_extracted_directory(outdir)
 
 
 def carve_unknown_chunk(extract_dir: Path, file: File, chunk: UnknownChunk) -> Path: