diff --git a/buck-tools/download_file.py b/buck-tools/download_file.py
new file mode 100755
index 0000000..bd67b50
--- /dev/null
+++ b/buck-tools/download_file.py
@@ -0,0 +1,198 @@
+#!/usr/bin/env python
+# Copyright (C) 2013 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+from hashlib import sha1
+from optparse import OptionParser
+from os import link, makedirs, path, remove
+import shutil
+from subprocess import check_call, CalledProcessError
+from sys import stderr
+from util import hash_file, resolve_url
+from zipfile import ZipFile, BadZipfile, LargeZipFile
+
+GERRIT_HOME = path.expanduser('~/.gerritcodereview')
+CACHE_DIR = path.join(GERRIT_HOME, 'buck-cache', 'downloaded-artifacts')
+# LEGACY_CACHE_DIR is only used to allow existing workspaces to move already
+# downloaded files to the new cache directory.
+# Please remove after 3 months (2015-10-07).
+LEGACY_CACHE_DIR = path.join(GERRIT_HOME, 'buck-cache')
+LOCAL_PROPERTIES = 'local.properties'
+
+
+def safe_mkdirs(d):
+  if path.isdir(d):
+    return
+  try:
+    makedirs(d)
+  except OSError as err:
+    if not path.isdir(d):
+      raise err
+
+
+def download_properties(root_dir):
+  """ Get the download properties.
+
+  First tries to find the properties file in the given root directory,
+  and if not found there, tries in the Gerrit settings folder in the
+  user's home directory.
+
+  Returns a set of download properties, which may be empty.
+
+  """
+  p = {}
+  local_prop = path.join(root_dir, LOCAL_PROPERTIES)
+  if not path.isfile(local_prop):
+    local_prop = path.join(GERRIT_HOME, LOCAL_PROPERTIES)
+  if path.isfile(local_prop):
+    try:
+      with open(local_prop) as fd:
+        for line in fd:
+          if line.startswith('download.'):
+            d = [e.strip() for e in line.split('=', 1)]
+            name, url = d[0], d[1]
+            p[name[len('download.'):]] = url
+    except OSError:
+      pass
+  return p
+
+
+def cache_entry(args):
+  if args.v:
+    h = args.v
+  else:
+    h = sha1(args.u.encode('utf-8')).hexdigest()
+  name = '%s-%s' % (path.basename(args.o), h)
+  return path.join(CACHE_DIR, name)
+
+# Please remove after 3 months (2015-10-07). See LEGACY_CACHE_DIR above.
+def legacy_cache_entry(args):
+  if args.v:
+    h = args.v
+  else:
+    h = sha1(args.u.encode('utf-8')).hexdigest()
+  name = '%s-%s' % (path.basename(args.o), h)
+  return path.join(LEGACY_CACHE_DIR, name)
+
+
+opts = OptionParser()
+opts.add_option('-o', help='local output file')
+opts.add_option('-u', help='URL to download')
+opts.add_option('-v', help='expected content SHA-1')
+opts.add_option('-x', action='append', help='file to delete from ZIP')
+opts.add_option('--exclude_java_sources', action='store_true')
+opts.add_option('--unsign', action='store_true')
+args, _ = opts.parse_args()
+
+root_dir = args.o
+while root_dir:
+  root_dir, n = path.split(root_dir)
+  if n == 'buck-out':
+    break
+
+redirects = download_properties(root_dir)
+cache_ent = cache_entry(args)
+legacy_cache_ent = legacy_cache_entry(args)
+src_url = resolve_url(args.u, redirects)
+
+# Please remove after 3 months (2015-10-07). See LEGACY_CACHE_DIR above.
+if not path.exists(cache_ent) and path.exists(legacy_cache_ent):
+  try:
+    safe_mkdirs(path.dirname(cache_ent))
+  except OSError as err:
+    print('error creating directory %s: %s' %
+          (path.dirname(cache_ent), err), file=stderr)
+    exit(1)
+  shutil.move(legacy_cache_ent, cache_ent)
+
+if not path.exists(cache_ent):
+  try:
+    safe_mkdirs(path.dirname(cache_ent))
+  except OSError as err:
+    print('error creating directory %s: %s' %
+          (path.dirname(cache_ent), err), file=stderr)
+    exit(1)
+
+  print('Download %s' % src_url, file=stderr)
+  try:
+    check_call(['curl', '--proxy-anyauth', '-ksfo', cache_ent, src_url])
+  except OSError as err:
+    print('could not invoke curl: %s\nis curl installed?' % err, file=stderr)
+    exit(1)
+  except CalledProcessError as err:
+    print('error using curl: %s' % err, file=stderr)
+    exit(1)
+
+if args.v:
+  have = hash_file(sha1(), cache_ent).hexdigest()
+  if args.v != have:
+    print((
+      '%s:\n' +
+      'expected %s\n' +
+      'received %s\n') % (src_url, args.v, have), file=stderr)
+    try:
+      remove(cache_ent)
+    except OSError as err:
+      if path.exists(cache_ent):
+        print('error removing %s: %s' % (cache_ent, err), file=stderr)
+    exit(1)
+
+exclude = []
+if args.x:
+  exclude += args.x
+if args.exclude_java_sources:
+  try:
+    with ZipFile(cache_ent, 'r') as zf:
+      for n in zf.namelist():
+        if n.endswith('.java'):
+          exclude.append(n)
+  except (BadZipfile, LargeZipFile) as err:
+    print('error opening %s: %s' % (cache_ent, err), file=stderr)
+    exit(1)
+
+if args.unsign:
+  try:
+    with ZipFile(cache_ent, 'r') as zf:
+      for n in zf.namelist():
+        if (n.endswith('.RSA')
+            or n.endswith('.SF')
+            or n.endswith('.LIST')):
+          exclude.append(n)
+  except (BadZipfile, LargeZipFile) as err:
+    print('error opening %s: %s' % (cache_ent, err), file=stderr)
+    exit(1)
+
+safe_mkdirs(path.dirname(args.o))
+if exclude:
+  try:
+    shutil.copyfile(cache_ent, args.o)
+  except (shutil.Error, IOError) as err:
+    print('error copying to %s: %s' % (args.o, err), file=stderr)
+    exit(1)
+  try:
+    check_call(['zip', '-d', args.o] + exclude)
+  except CalledProcessError as err:
+    print('error removing files from zip: %s' % err, file=stderr)
+    exit(1)
+else:
+  try:
+    link(cache_ent, args.o)
+  except OSError as err:
+    try:
+      shutil.copyfile(cache_ent, args.o)
+    except (shutil.Error, IOError) as err:
+      print('error copying to %s: %s' % (args.o, err), file=stderr)
+      exit(1)