swc-windows-installer.py: Split out zip_install into its own function

This makes it easy to install other packages besides nano.  I've also
added SHA1 checks to avoid installing packages that don't match the
expected hash.  This lets us trust ZipFile.extractall instead of
extracting from a hard-coded list of approved files.

diff --git a/swc-windows-installer.py b/swc-windows-installer.py
index 1ecd7149d7f97e66562b57fa3c9a33f6e958ec16..1904bbb89a844c8c967db12f763e26e1a3d55e26 100755 (executable)
--- a/swc-windows-installer.py
+++ b/swc-windows-installer.py
@@ -20,6 +20,7 @@ To use:
 
 """
 
+import hashlib
 try:  # Python 3
     from io import BytesIO as _BytesIO
 except ImportError:  # Python 2
@@ -32,17 +33,28 @@ except ImportError:  # Python 2
 import zipfile
 
 
+def zip_install(url, sha1, install_directory):
+    """Download and install a zipped bundle of compiled software"""
+    r = _urlopen(url)
+    zip_bytes = r.read()
+    download_sha1 = hashlib.sha1(zip_bytes).hexdigest()
+    if download_sha1 != sha1:
+        raise ValueError(
+            'downloaded {!r} has the wrong SHA1 hash: {} != {}'.format(
+                url, downloaded_sha1, sha1))
+    zip_io = _BytesIO(zip_bytes)
+    zip_file = zipfile.ZipFile(zip_io)
+    if not os.path.isdir(install_directory):
+        os.makedirs(install_directory)
+        zip_file.extractall(install_directory)
+
+
 def install_nano(install_directory):
     """Download and install the nano text editor"""
-    url = "http://www.nano-editor.org/dist/v2.2/NT/nano-2.2.6.zip"
-    r = _urlopen(url)
-    nano_zip_content = _BytesIO(r.read())
-    nano_zip = zipfile.ZipFile(nano_zip_content)
-    nano_files = ['nano.exe', 'cygwin1.dll', 'cygintl-8.dll',
-                  'cygiconv-2.dll', 'cyggcc_s-1.dll']
-    os.makedirs(install_directory)
-    for file_name in nano_files:
-        nano_zip.extract(file_name, install_directory)
+    zip_install(
+        url='http://www.nano-editor.org/dist/v2.2/NT/nano-2.2.6.zip',
+        sha1='f5348208158157060de0a4df339401f36250fe5b',
+        install_directory=install_directory)
 
 
 def create_nosetests_entry_point(python_scripts_directory):
@@ -89,7 +101,7 @@ def main():
     bin_dir = os.path.join(swc_dir, 'bin')
     create_nosetests_entry_point(python_scripts_directory=bin_dir)
     nano_dir = os.path.join(swc_dir, 'lib', 'nano')
-    install_nano(installation_directory=nano_dir)
+    install_nano(install_directory=nano_dir)
     update_bash_profile(extra_paths=(nano_dir, bin_dir))