Add public API for fsck, use it before loading metadata

A while ago I did `truncate -s 0 /path/to/repo/00/123.commit`, and expected a
checksum error, but I actually got a validation error due to us loading the
commit into a variant and trying to parse out the parent checksum, etc.

I first started by changing the `load_and_fsck_one_object()` function to
checksum before loading, but the problem is that we do a traverse of all objects
first. Fixing this is going to require an `OSTREE_REPO_COMMIT_TRAVER_FLAG_FSCK`
or something.

In the meantime at least though, let's add a public API to fsck a single object
which *does* checksum cleanly before parsing the object, and change the `fsck`
command to use it.

We then change the fsck binary to do this while iterating over the refs
and finding the commit object.  This way we'll at least get a checksum
first for commit objects, even if not dirtree/dirmeta.

Closes: #1364
Approved by: jlebon

1 files changed, 14 insertions, 2 deletions

diff --git a/tests/test-corruption.sh b/tests/test-corruption.sh
index 8e2aba56..52a8189a 100755
--- a/tests/test-corruption.sh
+++ b/tests/test-corruption.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Copyright (C) 2011 Colin Walters <walters@verbum.org>
+# Copyright (C) 2011,2017 Colin Walters <walters@verbum.org>
 #
 # This library is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -19,7 +19,7 @@
 
 set -euo pipefail
 
-echo "1..3"
+echo "1..4"
 
 . $(dirname $0)/libtest.sh
 
@@ -38,6 +38,18 @@ echo "ok chmod"
 cd ${test_tmpdir}
 rm repo files -rf
 setup_test_repository "bare"
+rev=$($OSTREE rev-parse test2)
+echo -n > repo/objects/${rev:0:2}/${rev:2}.commit
+if $OSTREE fsck -q 2>err.txt; then
+    fatal "fsck unexpectedly succeeded"
+fi
+assert_file_has_content_literal err.txt "Corrupted commit object; checksum expected"
+
+echo "ok metadata checksum"
+
+cd ${test_tmpdir}
+rm repo files -rf
+setup_test_repository "bare"
 rm checkout-test2 -rf
 $OSTREE checkout test2 checkout-test2
 cd checkout-test2