[PATCH 3/5] fsck: correctly compute checksums on idx files larger than 4GB
- From
Jeff King <peff@peff.net>
- Date
- Nov 13, 2020, 05:07 UTC
- Message-ID
- <20201113050714.GC744691@coredump.intra.peff.net>
- In-Reply-To
- <20201113050631.GA744608@coredump.intra.peff.net>
When checking the trailing checksum hash of a .idx file, we pass the whole buffer (minus the trailing hash) into a single call to the_hash_algo->update_fn(). But we cast it to an "unsigned int". This comes from c4001d92be (Use off_t when we really mean a file offset., 2007-03-06). That commit started storing the index_size variable as an off_t, but our mozilla-sha1 implementation from the time was limited to a smaller size. Presumably the cast was a way of annotating that we expected .idx files to be small, and so we didn't need to loop (as we do for arbitrarily-large .pack files). Though as an aside it was still wrong, because the mozilla function actually took a signed int.
These days our hash-update functions are defined to take a size_t, so we can pass the whole buffer in directly. The cast is actually causing a buggy truncation!
While we're here, though, let's drop the confusing off_t variable in the first place. We're getting the size not from the filesystem anyway, but from p->index_size, which is a size_t. In fact, we can make the code a bit more readable by dropping our local variable duplicating p->index_size, and instead have one that stores the size of the actual index data, minus the trailing hash.
Signed-off-by: Jeff King <peff@peff.net> --- pack-check.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/pack-check.c b/pack-check.c index db3adf8781..4b089fe8ec 100644 --- a/pack-check.c +++ b/pack-check.c @@ -164,22 +164,22 @@ static int verify_packfile(struct repository *r, int verify_pack_index(struct packed_git *p) { - off_t index_size; + size_t len; const unsigned char *index_base; git_hash_ctx ctx; unsigned char hash[GIT_MAX_RAWSZ]; int err = 0; if (open_pack_index(p)) return error("packfile %s index not opened", p->pack_name); - index_size = p->index_size; index_base = p->index_data; + len = p->index_size - the_hash_algo->rawsz; /* Verify SHA1 sum of the index file */ the_hash_algo->init_fn(&ctx); - the_hash_algo->update_fn(&ctx, index_base, (unsigned int)(index_size - the_hash_algo->rawsz)); + the_hash_algo->update_fn(&ctx, index_base, len); the_hash_algo->final_fn(hash, &ctx); - if (!hasheq(hash, index_base + index_size - the_hash_algo->rawsz)) + if (!hasheq(hash, index_base + len)) err = error("Packfile index for %s hash mismatch", p->pack_name); return err;
-- 2.29.2.705.g306f91dc4e