The object offset chunk has one fixed-size entry for each object in the
midx. But since we don't check its size, we may access out-of-bounds
memory if we see a corrupt or malicious midx file.
Sine the entries are fixed-size, the total length can be known up-front,
and we can just check it while parsing the chunk (this is similar to
what we do when opening pack idx files, which contain a similar offset
table).
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
midx.c | 15 ++++++++++++++-
t/t5319-multi-pack-index.sh | 10 ++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/midx.c b/midx.c
index 98f84fbe61..7b1b45f381 100644
--- a/midx.c
+++ b/midx.c
@@ -88,6 +88,19 @@ static int midx_read_oid_lookup(const unsigned char *chunk_start,
return 0;
}
+static int midx_read_object_offsets(const unsigned char *chunk_start,
+ size_t chunk_size, void *data)
+{
+ struct multi_pack_index *m = data;
+ m->chunk_object_offsets = chunk_start;
+
+ if (chunk_size != st_mult(m->num_objects, MIDX_CHUNK_OFFSET_WIDTH)) {
+ error(_("multi-pack-index object offset chunk is the wrong size"));
+ return 1;
+ }
+ return 0;
+}
+
struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local)
{
struct multi_pack_index *m = NULL;
@@ -164,7 +177,7 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
die(_("multi-pack-index required OID fanout chunk missing or corrupted"));
if (read_chunk(cf, MIDX_CHUNKID_OIDLOOKUP, midx_read_oid_lookup, m))
die(_("multi-pack-index required OID lookup chunk missing or corrupted"));
- if (pair_chunk_unsafe(cf, MIDX_CHUNKID_OBJECTOFFSETS, &m->chunk_object_offsets))
+ if (read_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS, midx_read_object_offsets, m))
die(_("multi-pack-index required object offsets chunk missing or corrupted"));
pair_chunk_unsafe(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets);
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 34f5944142..30687d5452 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -1108,4 +1108,14 @@ test_expect_success 'reader handles unaligned chunks' '
test_cmp expect.err err
'
+test_expect_success 'reader notices too-small object offset chunk' '
+ corrupt_chunk OOFF clear 00000000 &&
+ test_must_fail git log 2>err &&
+ cat >expect <<-\EOF &&
+ error: multi-pack-index object offset chunk is the wrong size
+ fatal: multi-pack-index required object offsets chunk missing or corrupted
+ EOF
+ test_cmp expect err
+'
+
test_done
--
2.42.0.884.g35e1fe1a6a
