| Message ID | 80b5662f30cb87210385a6bd26e037ce39e46b6d.1544729841.git.steadmon@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add commit-graph fuzzer and fix buffer overflow | expand |
On Thu, Dec 13, 2018 at 11:43:57AM -0800, Josh Steadmon wrote: > diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh > index 5fe21db99f..a1b5a75882 100755 > --- a/t/t5318-commit-graph.sh > +++ b/t/t5318-commit-graph.sh > @@ -366,21 +366,26 @@ GRAPH_OCTOPUS_DATA_OFFSET=$(($GRAPH_COMMIT_DATA_OFFSET + \ > GRAPH_BYTE_OCTOPUS=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4)) > GRAPH_BYTE_FOOTER=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4 * $NUM_OCTOPUS_EDGES)) > > -# usage: corrupt_graph_and_verify <position> <data> <string> > +# usage: corrupt_graph_and_verify <position> <data> <string> [<zero_pos>] > # Manipulates the commit-graph file at the position > -# by inserting the data, then runs 'git commit-graph verify' > +# by inserting the data, optionally zeroing the file > +# starting at <zero_pos>, then runs 'git commit-graph verify' > # and places the output in the file 'err'. Test 'err' for > # the given string. > corrupt_graph_and_verify() { > pos=$1 > data="${2:-\0}" > grepstr=$3 > + orig_size=$(wc -c < $objdir/info/commit-graph) && A minor nit: this test script is unusually prudent about which directory/repository each test is executed in, as the first thing each test does is to 'cd' into the right directory. (I think this is a Good Thing, and other test scripts should follow suit if they use a repo other than $TRASH_DIRECTORY.) Though it doesn't cause any immediate issues (the previous test happens to use the same repository), the above line violates this, as it accesses the '.git/.../commit-graph' file ... > + zero_pos=${4:-${orig_size}} && > cd "$TRASH_DIRECTORY/full" && ... before this line could ensure that it's in the right repository. > test_when_finished mv commit-graph-backup $objdir/info/commit-graph && > cp $objdir/info/commit-graph commit-graph-backup && > printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc && > + dd of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=0 && > + dd if=/dev/zero of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=$(($orig_size - $zero_pos)) && > test_must_fail git commit-graph verify 2>test_err && > - grep -v "^+" test_err >err > + grep -v "^+" test_err >err && > test_i18ngrep "$grepstr" err > } > > @@ -484,6 +489,11 @@ test_expect_success 'detect invalid checksum hash' ' > "incorrect checksum" > ' > > +test_expect_success 'detect incorrect chunk count' ' > + corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\377" \ > + "chunk lookup table entry missing" $GRAPH_CHUNK_LOOKUP_OFFSET > +' > + > test_expect_success 'git fsck (checks commit-graph)' ' > cd "$TRASH_DIRECTORY/full" && > git fsck && > -- > 2.20.0.rc2.10.g21101b961a >
On 2019.01.12 11:57, SZEDER Gábor wrote: > On Thu, Dec 13, 2018 at 11:43:57AM -0800, Josh Steadmon wrote: > > diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh > > index 5fe21db99f..a1b5a75882 100755 > > --- a/t/t5318-commit-graph.sh > > +++ b/t/t5318-commit-graph.sh > > @@ -366,21 +366,26 @@ GRAPH_OCTOPUS_DATA_OFFSET=$(($GRAPH_COMMIT_DATA_OFFSET + \ > > GRAPH_BYTE_OCTOPUS=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4)) > > GRAPH_BYTE_FOOTER=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4 * $NUM_OCTOPUS_EDGES)) > > > > -# usage: corrupt_graph_and_verify <position> <data> <string> > > +# usage: corrupt_graph_and_verify <position> <data> <string> [<zero_pos>] > > # Manipulates the commit-graph file at the position > > -# by inserting the data, then runs 'git commit-graph verify' > > +# by inserting the data, optionally zeroing the file > > +# starting at <zero_pos>, then runs 'git commit-graph verify' > > # and places the output in the file 'err'. Test 'err' for > > # the given string. > > corrupt_graph_and_verify() { > > pos=$1 > > data="${2:-\0}" > > grepstr=$3 > > + orig_size=$(wc -c < $objdir/info/commit-graph) && > > A minor nit: this test script is unusually prudent about which > directory/repository each test is executed in, as the first thing each > test does is to 'cd' into the right directory. (I think this is a > Good Thing, and other test scripts should follow suit if they use a > repo other than $TRASH_DIRECTORY.) Though it doesn't cause any > immediate issues (the previous test happens to use the same > repository), the above line violates this, as it accesses the > '.git/.../commit-graph' file ... > > > + zero_pos=${4:-${orig_size}} && > > cd "$TRASH_DIRECTORY/full" && > > ... before this line could ensure that it's in the right repository. Thanks for the catch. Fixed in v5.
diff --git a/commit-graph.c b/commit-graph.c index 07dd410f3c..836d65a1d3 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -165,10 +165,20 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd, last_chunk_offset = 8; chunk_lookup = data + 8; for (i = 0; i < graph->num_chunks; i++) { - uint32_t chunk_id = get_be32(chunk_lookup + 0); - uint64_t chunk_offset = get_be64(chunk_lookup + 4); + uint32_t chunk_id; + uint64_t chunk_offset; int chunk_repeated = 0; + if (data + graph_size - chunk_lookup < + GRAPH_CHUNKLOOKUP_WIDTH) { + error(_("chunk lookup table entry missing; graph file may be incomplete")); + free(graph); + return NULL; + } + + chunk_id = get_be32(chunk_lookup + 0); + chunk_offset = get_be64(chunk_lookup + 4); + chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH; if (chunk_offset > graph_size - GIT_MAX_RAWSZ) { diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh index 5fe21db99f..a1b5a75882 100755 --- a/t/t5318-commit-graph.sh +++ b/t/t5318-commit-graph.sh @@ -366,21 +366,26 @@ GRAPH_OCTOPUS_DATA_OFFSET=$(($GRAPH_COMMIT_DATA_OFFSET + \ GRAPH_BYTE_OCTOPUS=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4)) GRAPH_BYTE_FOOTER=$(($GRAPH_OCTOPUS_DATA_OFFSET + 4 * $NUM_OCTOPUS_EDGES)) -# usage: corrupt_graph_and_verify <position> <data> <string> +# usage: corrupt_graph_and_verify <position> <data> <string> [<zero_pos>] # Manipulates the commit-graph file at the position -# by inserting the data, then runs 'git commit-graph verify' +# by inserting the data, optionally zeroing the file +# starting at <zero_pos>, then runs 'git commit-graph verify' # and places the output in the file 'err'. Test 'err' for # the given string. corrupt_graph_and_verify() { pos=$1 data="${2:-\0}" grepstr=$3 + orig_size=$(wc -c < $objdir/info/commit-graph) && + zero_pos=${4:-${orig_size}} && cd "$TRASH_DIRECTORY/full" && test_when_finished mv commit-graph-backup $objdir/info/commit-graph && cp $objdir/info/commit-graph commit-graph-backup && printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc && + dd of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=0 && + dd if=/dev/zero of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=$(($orig_size - $zero_pos)) && test_must_fail git commit-graph verify 2>test_err && - grep -v "^+" test_err >err + grep -v "^+" test_err >err && test_i18ngrep "$grepstr" err } @@ -484,6 +489,11 @@ test_expect_success 'detect invalid checksum hash' ' "incorrect checksum" ' +test_expect_success 'detect incorrect chunk count' ' + corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\377" \ + "chunk lookup table entry missing" $GRAPH_CHUNK_LOOKUP_OFFSET +' + test_expect_success 'git fsck (checks commit-graph)' ' cd "$TRASH_DIRECTORY/full" && git fsck &&
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> --- commit-graph.c | 14 ++++++++++++-- t/t5318-commit-graph.sh | 16 +++++++++++++--- 2 files changed, 25 insertions(+), 5 deletions(-)