repo: do not put objects that we won't get, fixes #1451

we will not get() objects that have a segment entry larger than MAX_OBJECT_SIZE.
thus we should never produce such entries.

also: introduce repository.MAX_DATA_SIZE that gives the max payload size.

borg/repository.py

@@ -731,8 +731,12 @@ class LoggedIO:
         return size, tag, key, data
 
     def write_put(self, id, data, raise_full=False):
+        data_size = len(data)
+        if data_size > MAX_DATA_SIZE:
+            # this would push the segment entry size beyond MAX_OBJECT_SIZE.
+            raise IntegrityError('More than allowed put data [{} > {}]'.format(data_size, MAX_DATA_SIZE))
         fd = self.get_write_fd(raise_full=raise_full)
-        size = len(data) + self.put_header_fmt.size
+        size = data_size + self.put_header_fmt.size
         offset = self.offset
         header = self.header_no_crc_fmt.pack(size, TAG_PUT)
         crc = self.crc_fmt.pack(crc32(data, crc32(id, crc32(header))) & 0xffffffff)
@@ -771,3 +775,6 @@ class LoggedIO:
             self._write_fd.close()
             sync_dir(os.path.dirname(self._write_fd.name))
             self._write_fd = None
+
+
+MAX_DATA_SIZE = MAX_OBJECT_SIZE - LoggedIO.put_header_fmt.size

borg/testsuite/repository.py

@@ -8,7 +8,7 @@ from ..hashindex import NSIndex
 from ..helpers import Location, IntegrityError
 from ..locking import Lock, LockFailed
 from ..remote import RemoteRepository, InvalidRPCMethod
-from ..repository import Repository, LoggedIO, TAG_COMMIT
+from ..repository import Repository, LoggedIO, TAG_COMMIT, MAX_DATA_SIZE
 from . import BaseTestCase
 
 
@@ -128,6 +128,13 @@ class RepositoryTestCase(RepositoryTestCaseBase):
         self.assert_equal(second_half, all[50:])
         self.assert_equal(len(self.repository.list(limit=50)), 50)
 
+    def test_max_data_size(self):
+        max_data = b'x' * MAX_DATA_SIZE
+        self.repository.put(b'00000000000000000000000000000000', max_data)
+        self.assert_equal(self.repository.get(b'00000000000000000000000000000000'), max_data)
+        self.assert_raises(IntegrityError,
+                           lambda: self.repository.put(b'00000000000000000000000000000001', max_data + b'x'))
+
 
 class RepositoryCommitTestCase(RepositoryTestCaseBase):
 

docs/changes.rst

@@ -57,6 +57,14 @@ Security fixes:
 
 - fix security issue with remote repository access, #1428
 
+Bug fixes:
+
+- do not write objects to repository that are bigger than the allowed size,
+  borg will reject reading them, #1451.
+  IMPORTANT: if you created archives with many millions of files or
+             directories, please verify if you can open them successfully,
+             e.g. try a "borg list REPO::ARCHIVE".
+
 
 Version 1.0.7rc1 (2016-08-05)
 -----------------------------