luci-py/isolateserver.py: Add support for tar archives when downloading.

client/isolateserver.py

Index: client/isolateserver.py
diff --git a/client/isolateserver.py b/client/isolateserver.py
index 22ab89cdefabf1af5b24024fa862765f16ef9d3d..0e1ad010d2513d33da550d19e50c0fd1fdf01d99 100755
--- a/client/isolateserver.py
+++ b/client/isolateserver.py
@@ -18,6 +18,7 @@ import re
 import signal
 import stat
 import sys
+import tarfile
 import tempfile
 import threading
 import time
@@ -169,6 +170,11 @@ def fileobj_path(fileobj):
   if not isinstance(name, unicode):
     name = name.decode(sys.getfilesystemencoding())
 
+  # fs.exists requires an absolute path, otherwise it will fail with an
+  # assertion error.
+  if not os.path.isabs(name):
+      return
+
   if fs.exists(name):
     return name
 
@@ -2107,6 +2113,20 @@ def fetch_isolated(isolated_hash, storage, cache, outdir, use_symlinks):
                     srcfileobj, fullpath, file_mode,
                     use_symlink=use_symlinks)
 
+              elif filetype == 'tar':
+                basedir = os.path.dirname(fullpath)
+                extractor = tarfile.TarFile(fileobj=srcfileobj)

[M-A Ruel, 2016/11/08 14:33:44]

with tarfile.TarFile(fileobj=srcfileobj) as t:
  for ti in t:
...

[mithro, 2016/11/09 00:19:35]

Done.

+                for ti in extractor:
+                  if not ti.isfile():
+                    logging.warning(
+                        "Nonfile (%s) object %s skipped", ti.type, ti.name)
+                    continue
+                  ifd = extractor.extractfile(ti)
+                  fp = os.path.normpath(os.path.join(basedir, ti.name))

[M-A Ruel, 2016/11/08 14:33:44]

if not fp.startswith(basedir):
  logging.error('tar file with path outside root directory')
  raise an error

[mithro, 2016/11/09 00:19:35]

Done.

+                  file_path.ensure_tree(os.path.dirname(fp))
+                  putfile(ifd, fp, 0700, ti.size)
+                extractor.close()
+
               elif filetype == 'ar':
                 basedir = os.path.dirname(fullpath)
                 extractor = arfile.ArFileReader(srcfileobj, fullparse=False)