commit-graph: fix buffer read-overflow
fuzz-commit-graph identified a case where Git will read past the end of a buffer containing a commit graph if the graph's header has an incorrect chunk count. A simple bounds check in parse_commit_graph() prevents this. Signed-off-by: Josh Steadmon <steadmon@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Josh Steadmon committed
Jan 15, 2019 at 14:25 UTC
d2b86fbaa1f6c0606330caf3cc3fdf8984ddc66a
2 files changed
+25
-5
commit-graph.c
+12
-2
@@ -165,10 +165,20 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
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last_chunk_offset = 8;
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chunk_lookup = data + 8;
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for (i = 0; i < graph->num_chunks; i++) {
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- uint32_t chunk_id = get_be32(chunk_lookup + 0);
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- uint64_t chunk_offset = get_be64(chunk_lookup + 4);
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+ uint32_t chunk_id;
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+ uint64_t chunk_offset;
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int chunk_repeated = 0;
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+ if (data + graph_size - chunk_lookup <
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+ GRAPH_CHUNKLOOKUP_WIDTH) {
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+ error(_("chunk lookup table entry missing; graph file may be incomplete"));
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+ free(graph);
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+ return NULL;
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+ }
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+
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+ chunk_id = get_be32(chunk_lookup + 0);
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+ chunk_offset = get_be64(chunk_lookup + 4);
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+
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chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
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if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
t/t5318-commit-graph.sh
+13
-3
@@ -366,9 +366,10 @@ GRAPH_OCTOPUS_DATA_OFFSET=$(($GRAPH_COMMIT_DATA_OFFSET + \
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GRAPH_BYTE_OCTOPUS=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4))
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GRAPH_BYTE_FOOTER=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4 * $NUM_OCTOPUS_EDGES))
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-# usage: corrupt_graph_and_verify <position> <data> <string>
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+# usage: corrupt_graph_and_verify <position> <data> <string> [<zero_pos>]
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# Manipulates the commit-graph file at the position
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-# by inserting the data, then runs 'git commit-graph verify'
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+# by inserting the data, optionally zeroing the file
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+# starting at <zero_pos>, then runs 'git commit-graph verify'
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# and places the output in the file 'err'. Test 'err' for
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# the given string.
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corrupt_graph_and_verify() {
@@ -376,11 +377,15 @@ corrupt_graph_and_verify() {
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data="${2:-\0}"
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grepstr=$3
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cd "$TRASH_DIRECTORY/full" &&
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+ orig_size=$(wc -c < $objdir/info/commit-graph) &&
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+ zero_pos=${4:-${orig_size}} &&
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test_when_finished mv commit-graph-backup $objdir/info/commit-graph &&
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cp $objdir/info/commit-graph commit-graph-backup &&
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printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
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+ dd of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=0 &&
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+ dd if=/dev/zero of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=$(($orig_size - $zero_pos)) &&
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test_must_fail git commit-graph verify 2>test_err &&
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- grep -v "^+" test_err >err
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+ grep -v "^+" test_err >err &&
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test_i18ngrep "$grepstr" err
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}
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@@ -484,6 +489,11 @@ test_expect_success 'detect invalid checksum hash' '
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"incorrect checksum"
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'
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+test_expect_success 'detect incorrect chunk count' '
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+ corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\377" \
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+ "chunk lookup table entry missing" $GRAPH_CHUNK_LOOKUP_OFFSET
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+'
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+
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test_expect_success 'git fsck (checks commit-graph)' '
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cd "$TRASH_DIRECTORY/full" &&
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git fsck &&