CVE-2015-4082

@@ -62,6 +62,7 @@ def do_init(self, args):
         manifest.key = key
         manifest.write()
         repository.commit()
+        Cache(repository, key, manifest, warn_if_unencrypted=False)
         return self.exit_code
 
     def do_check(self, args):

@@ -2,9 +2,11 @@
 from attic.remote import cache_if_remote
 import msgpack
 import os
+import sys
 from binascii import hexlify
 import shutil
 
+from .key import PlaintextKey
 from .helpers import Error, get_cache_dir, decode_dict, st_mtime_ns, unhexlify, UpgradableLock, int_to_bigint, \
     bigint_to_int
 from .hashindex import ChunkIndex
@@ -16,20 +18,38 @@ class Cache(object):
     class RepositoryReplay(Error):
         """Cache is newer than repository, refusing to continue"""
 
-    def __init__(self, repository, key, manifest, path=None, sync=True):
+    class CacheInitAbortedError(Error):
+        """Cache initialization aborted"""
+
+
+    class EncryptionMethodMismatch(Error):
+        """Repository encryption method changed since last acccess, refusing to continue
+        """
+
+    def __init__(self, repository, key, manifest, path=None, sync=True, warn_if_unencrypted=True):
+        self.lock = None
         self.timestamp = None
         self.txn_active = False
         self.repository = repository
         self.key = key
         self.manifest = manifest
         self.path = path or os.path.join(get_cache_dir(), hexlify(repository.id).decode('ascii'))
         if not os.path.exists(self.path):
+            if warn_if_unencrypted and isinstance(key, PlaintextKey):
+                if 'ATTIC_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK' not in os.environ:
+                    print("""Warning: Attempting to access a previously unknown unencrypted repository\n""", file=sys.stderr)
+                    answer = input('Do you want to continue? [yN] ')
+                    if not (answer and answer in 'Yy'):
+                        raise self.CacheInitAbortedError()
             self.create()
         self.open()
         if sync and self.manifest.id != self.manifest_id:
             # If repository is older than the cache something fishy is going on
             if self.timestamp and self.timestamp > manifest.timestamp:
                 raise self.RepositoryReplay()
+            # Make sure an encrypted repository has not been swapped for an unencrypted repository
+            if self.key_type is not None and self.key_type != str(key.TYPE):
+                raise self.EncryptionMethodMismatch()
             self.sync()
             self.commit()
 
@@ -65,11 +85,13 @@ def open(self):
         self.id = self.config.get('cache', 'repository')
         self.manifest_id = unhexlify(self.config.get('cache', 'manifest'))
         self.timestamp = self.config.get('cache', 'timestamp', fallback=None)
+        self.key_type = self.config.get('cache', 'key_type', fallback=None)
         self.chunks = ChunkIndex.read(os.path.join(self.path, 'chunks').encode('utf-8'))
         self.files = None
 
     def close(self):
-        self.lock.release()
+        if self.lock:
+            self.lock.release()
 
     def _read_files(self):
         self.files = {}
@@ -111,6 +133,7 @@ def commit(self):
                         msgpack.pack((path_hash, item), fd)
         self.config.set('cache', 'manifest', hexlify(self.manifest.id).decode('ascii'))
         self.config.set('cache', 'timestamp', self.manifest.timestamp)
+        self.config.set('cache', 'key_type', str(self.key.TYPE))
         with open(os.path.join(self.path, 'config'), 'w') as fd:
             self.config.write(fd)
         self.chunks.write(os.path.join(self.path, 'chunks').encode('utf-8'))

@@ -1,3 +1,5 @@
+from binascii import hexlify
+from configparser import RawConfigParser
 import os
 from io import StringIO
 import stat
@@ -11,6 +13,7 @@
 from attic import xattr
 from attic.archive import Archive, ChunkBuffer
 from attic.archiver import Archiver
+from attic.cache import Cache
 from attic.crypto import bytes_to_long, num_aes_blocks
 from attic.helpers import Manifest
 from attic.remote import RemoteRepository, PathNotAllowed
@@ -41,6 +44,22 @@ def __exit__(self, *args, **kw):
         os.chdir(self.old)
 
 
+class environment_variable:
+    def __init__(self, **values):
+        self.values = values
+        self.old_values = {}
+
+    def __enter__(self):
+        for k, v in self.values.items():
+            self.old_values[k] = os.environ.get(k)
+            os.environ[k] = v
+
+    def __exit__(self, *args, **kw):
+        for k, v in self.old_values.items():
+            if v is not None:
+                os.environ[k] = v
+
+
 class ArchiverTestCaseBase(AtticTestCase):
 
     prefix = ''
@@ -161,11 +180,35 @@ def test_basic_functionality(self):
         info_output = self.attic('info', self.repository_location + '::test')
         self.assert_in('Number of files: 4', info_output)
         shutil.rmtree(self.cache_path)
-        info_output2 = self.attic('info', self.repository_location + '::test')
+        with environment_variable(ATTIC_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK='1'):
+            info_output2 = self.attic('info', self.repository_location + '::test')
         # info_output2 starts with some "initializing cache" text but should
         # end the same way as info_output
         assert info_output2.endswith(info_output)
 
+    def _extract_repository_id(self, path):
+        return Repository(self.repository_path).id
+
+    def _set_repository_id(self, path, id):
+        config = RawConfigParser()
+        config.read(os.path.join(path, 'config'))
+        config.set('repository', 'id', hexlify(id).decode('ascii'))
+        with open(os.path.join(path, 'config'), 'w') as fd:
+            config.write(fd)
+        return Repository(self.repository_path).id
+
+    def test_repository_swap_detection(self):
+        self.create_test_files()
+        os.environ['ATTIC_PASSPHRASE'] = 'passphrase'
+        self.attic('init', '--encryption=passphrase', self.repository_location)
+        repository_id = self._extract_repository_id(self.repository_path)
+        self.attic('create', self.repository_location + '::test', 'input')
+        shutil.rmtree(self.repository_path)
+        self.attic('init', '--encryption=none', self.repository_location)
+        self._set_repository_id(self.repository_path, repository_id)
+        self.assert_equal(repository_id, self._extract_repository_id(self.repository_path))
+        self.assert_raises(Cache.EncryptionMethodMismatch, lambda :self.attic('create', self.repository_location + '::test.2', 'input'))
+
     def test_strip_components(self):
         self.attic('init', self.repository_location)
         self.create_regular_file('dir/file')

@@ -7,6 +7,7 @@ Version 0.15
 ------------
 
 (feature release, released on X)
+- Require approval before accessing previously unknown unencrypted repositories (#271)
 - Fix issue with hash index files larger than 2GB.
 - Fix Python 3.2 compatibility issue with noatime open() (#164)
 - Include missing pyx files in dist files (#168)