summaryrefslogtreecommitdiff
path: root/include
diff options
context:
space:
mode:
authorPatrick Steinhardt <ps@pks.im>2017-04-10 09:30:08 +0200
committerPatrick Steinhardt <ps@pks.im>2017-04-28 14:05:45 +0200
commit28a0741f1ae6f5e1261c8e73854dda69e7a61067 (patch)
treeb14a8170f8bb853af341a07423bfbd9923ec1997 /include
parentd59dabe5cbee52035810216ab118fa3f63047f2f (diff)
downloadlibgit2-28a0741f1ae6f5e1261c8e73854dda69e7a61067.tar.gz
odb: verify object hashes
The upstream git.git project verifies objects when looking them up from disk. This avoids scenarios where objects have somehow become corrupt on disk, e.g. due to hardware failures or bit flips. While our mantra is usually to follow upstream behavior, we do not do so in this case, as we never check hashes of objects we have just read from disk. To fix this, we create a new error class `GIT_EMISMATCH` which denotes that we have looked up an object with a hashsum mismatch. `odb_read_1` will then, after having read the object from its backend, hash the object and compare the resulting hash to the expected hash. If hashes do not match, it will return an error. This obviously introduces another computation of checksums and could potentially impact performance. Note though that we usually perform I/O operations directly before doing this computation, and as such the actual overhead should be drowned out by I/O. Running our test suite seems to confirm this guess. On a Linux system with best-of-five timings, we had 21.592s with the check enabled and 21.590s with the ckeck disabled. Note though that our test suite mostly contains very small blobs only. It is expected that repositories with bigger blobs may notice an increased hit by this check. In addition to a new test, we also had to change the odb::backend::nonrefreshing test suite, which now triggers a hashsum mismatch when looking up the commit "deadbeef...". This is expected, as the fake backend allocated inside of the test will return an empty object for the OID "deadbeef...", which will obviously not hash back to "deadbeef..." again. We can simply adjust the hash to equal the hash of the empty object here to fix this test.
Diffstat (limited to 'include')
-rw-r--r--include/git2/errors.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/git2/errors.h b/include/git2/errors.h
index 71bff0f9d..6f5580253 100644
--- a/include/git2/errors.h
+++ b/include/git2/errors.h
@@ -54,6 +54,7 @@ typedef enum {
GIT_PASSTHROUGH = -30, /**< Internal only */
GIT_ITEROVER = -31, /**< Signals end of iteration with iterator */
GIT_RETRY = -32, /**< Internal only */
+ GIT_EMISMATCH = -33, /**< Hashsum mismatch in object */
} git_error_code;
/**