Do not use any parts of image URL in temporary file names

We currently use the last component, which is:
a) a potential information exposure,
b) can hit file name length limits [1]

Use the master path file name instead, which is always a UUID.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2014630

Change-Id: I2aa1230468132c2b7a8585d691ec180947f89c1e

ironic/drivers/modules/image_cache.py

@@ -161,7 +161,7 @@ class ImageCache(object):
         # TODO(ghe): timeout and retry for downloads
         # TODO(ghe): logging when image cannot be created
         tmp_dir = tempfile.mkdtemp(dir=self.master_dir)
-        tmp_path = os.path.join(tmp_dir, href.split('/')[-1])
+        tmp_path = os.path.join(tmp_dir, os.path.basename(master_path))
 
         try:
             with _concurrency_semaphore:

ironic/tests/unit/drivers/modules/test_image_cache.py

@@ -226,6 +226,28 @@ class TestImageCacheFetch(base.TestCase):
         with open(self.dest_path) as fp:
             self.assertEqual("TEST", fp.read())
 
+    @mock.patch.object(image_cache, '_fetch', autospec=True)
+    def test__download_image_large_url(self, mock_fetch):
+        # A long enough URL may exceed the file name limits of the file system.
+        # Make sure we don't use any parts of the URL anywhere.
+        url = "http://example.com/image.iso?secret=%s" % ("x" * 1000)
+
+        def _fake_fetch(ctx, href, tmp_path, *args):
+            self.assertEqual(url, href)
+            self.assertNotEqual(self.dest_path, tmp_path)
+            self.assertNotEqual(os.path.dirname(tmp_path), self.master_dir)
+            with open(tmp_path, 'w') as fp:
+                fp.write("TEST")
+
+        mock_fetch.side_effect = _fake_fetch
+        self.cache._download_image(url, self.master_path, self.dest_path)
+        self.assertTrue(os.path.isfile(self.dest_path))
+        self.assertTrue(os.path.isfile(self.master_path))
+        self.assertEqual(os.stat(self.dest_path).st_ino,
+                         os.stat(self.master_path).st_ino)
+        with open(self.dest_path) as fp:
+            self.assertEqual("TEST", fp.read())
+
     @mock.patch.object(image_cache, '_fetch', autospec=True)
     @mock.patch.object(image_cache, 'LOG', autospec=True)
     @mock.patch.object(os, 'link', autospec=True)

releasenotes/notes/image-cache-size-28a9072901b98edf.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes ``File name too long`` in the image caching code when a URL contains
+    a long query string.