Issue #63: Initial implementation of a mechanism for securely bootstrapping...

Issue #63: Initial implementation of a mechanism for securely bootstrapping setuptools, leveraging system tools for trust validation.

ez_setup.py

@@ -20,6 +20,7 @@ import tempfile
 import tarfile
 import optparse
 import subprocess
+import platform
 
 from distutils import log
 
@@ -141,6 +142,59 @@ def use_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
         return _do_download(version, download_base, to_dir,
                             download_delay)
 
+def download_file_powershell(url, target):
+    """
+    Download the file at url to target using Powershell (which will validate
+    trust). Raise an exception if the command cannot complete.
+    """
+    target = os.path.abspath(target)
+    cmd = [
+        'powershell',
+        '-Command',
+        "(new-object System.Net.WebClient).DownloadFile(%(url)r, %(target)r)" % vars(),
+    ]
+    subprocess.check_call(cmd)
+
+download_file_powershell.viable = (
+    lambda: platform.name() == 'Windows' and platform.win32_ver()[1] >= '6'
+)
+
+def download_file_insecure(url, target):
+    """
+    Use Python to download the file, even though it cannot authenticate the
+    connection.
+    """
+    try:
+        from urllib.request import urlopen
+    except ImportError:
+        from urllib2 import urlopen
+    src = dst = None
+    try:
+        src = urlopen(url)
+        # Read/write all in one block, so we don't create a corrupt file
+        # if the download is interrupted.
+        data = src.read()
+        dst = open(target, "wb")
+        dst.write(data)
+    finally:
+        if src:
+            src.close()
+        if dst:
+            dst.close()
+
+download_file_insecure.viable = lambda: True
+
+def get_best_downloader():
+    downloaders = [
+        download_file_powershell,
+        #download_file_curl,
+        #download_file_wget,
+        download_file_insecure,
+    ]
+
+    for dl in downloaders:
+        if dl.viable():
+            return dl
 
 def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
                         to_dir=os.curdir, delay=15):
@@ -154,28 +208,13 @@ def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
     """
     # making sure we use the absolute path
     to_dir = os.path.abspath(to_dir)
-    try:
-        from urllib.request import urlopen
-    except ImportError:
-        from urllib2 import urlopen
     tgz_name = "setuptools-%s.tar.gz" % version
     url = download_base + tgz_name
     saveto = os.path.join(to_dir, tgz_name)
-    src = dst = None
     if not os.path.exists(saveto):  # Avoid repeated downloads
-        try:
-            log.warn("Downloading %s", url)
-            src = urlopen(url)
-            # Read/write all in one block, so we don't create a corrupt file
-            # if the download is interrupted.
-            data = src.read()
-            dst = open(saveto, "wb")
-            dst.write(data)
-        finally:
-            if src:
-                src.close()
-            if dst:
-                dst.close()
+        log.warn("Downloading %s", url)
+        downloader = get_best_downloader()
+        downloader(url, saveto)
     return os.path.realpath(saveto)