midx: check size of object offset chunk
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@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Oct 9, 2023 at 17:05 UTC
0924869b4e27ff9db63e2d85b892244e058fecc3
2 files changed
+24
-1
midx.c
+14
-1
@@ -88,6 +88,19 @@ static int midx_read_oid_lookup(const unsigned char *chunk_start,
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return 0;
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}
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+static int midx_read_object_offsets(const unsigned char *chunk_start,
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+ size_t chunk_size, void *data)
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+{
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+ struct multi_pack_index *m = data;
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+ m->chunk_object_offsets = chunk_start;
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+
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+ if (chunk_size != st_mult(m->num_objects, MIDX_CHUNK_OFFSET_WIDTH)) {
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+ error(_("multi-pack-index object offset chunk is the wrong size"));
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+ return 1;
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+ }
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+ return 0;
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+}
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+
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struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local)
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{
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struct multi_pack_index *m = NULL;
@@ -164,7 +177,7 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
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die(_("multi-pack-index required OID fanout chunk missing or corrupted"));
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if (read_chunk(cf, MIDX_CHUNKID_OIDLOOKUP, midx_read_oid_lookup, m))
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die(_("multi-pack-index required OID lookup chunk missing or corrupted"));
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- if (pair_chunk_unsafe(cf, MIDX_CHUNKID_OBJECTOFFSETS, &m->chunk_object_offsets))
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+ if (read_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS, midx_read_object_offsets, m))
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die(_("multi-pack-index required object offsets chunk missing or corrupted"));
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pair_chunk_unsafe(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets);
t/t5319-multi-pack-index.sh
+10
@@ -1108,4 +1108,14 @@ test_expect_success 'reader handles unaligned chunks' '
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test_cmp expect.err err
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'
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+test_expect_success 'reader notices too-small object offset chunk' '
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+ corrupt_chunk OOFF clear 00000000 &&
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+ test_must_fail git log 2>err &&
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+ cat >expect <<-\EOF &&
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+ error: multi-pack-index object offset chunk is the wrong size
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+ fatal: multi-pack-index required object offsets chunk missing or corrupted
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+ EOF
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+ test_cmp expect err
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+'
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+
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test_done