Make listing contents of local tarball cache more robust

Previously it would crash with a backtrace if there were unexpected
filenames in the directory. It's still not amazingly robust, but I
don't have time to rewrite the whole thing now.

This code seems to have ignored that cachefs.walkfiles() returns
filenames with a preceeding '/', which I have fixed now.

Change-Id: I98b3094bd6c82b26984513ee81a1eab9bf253a34

1 files changed, 12 insertions, 1 deletions

diff --git a/morphlib/localartifactcache.py b/morphlib/localartifactcache.py
index e6695c4e..19125deb 100644
--- a/morphlib/localartifactcache.py
+++ b/morphlib/localartifactcache.py
@@ -129,9 +129,20 @@ class LocalArtifactCache(object):
            returns a [(cache_key, set(artifacts), last_used)]
 
         '''
+        def is_artifact(filename):
+            # This is just enough to avoid crashes from random unpacked
+            # directory trees and temporary files in the cachedir. A
+            # better mechanism is needed. It's not simple to tell
+            # OSFS.walkfiles() to do a non-recursive walk, sadly.
+            return '.' in filename and '/' not in filename
+
         CacheInfo = collections.namedtuple('CacheInfo', ('artifacts', 'mtime'))
         contents = collections.defaultdict(lambda: CacheInfo(set(), 0))
         for filename in self.cachefs.walkfiles():
+            # filenames are returned with a preceeding /.
+            filename = filename[1:]
+            if not is_artifact(filename):  # pragma: no cover
+                continue
             cachekey = filename[:63]
             artifact = filename[65:]
             artifacts, max_mtime = contents[cachekey]
@@ -146,5 +157,5 @@ class LocalArtifactCache(object):
     def remove(self, cachekey):
         '''Remove all artifacts associated with the given cachekey.'''
         for filename in (x for x in self.cachefs.walkfiles()
-                         if x.startswith(cachekey)):
+                         if x[1:].startswith(cachekey)):
             self.cachefs.remove(filename)