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Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Commit a1283866b (t5313: test bounds-checks of
corrupted/malicious pack/idx files, 2016-02-25) added a test
that requires our corrupted pack index to have two objects.
The entry for the first one remains untouched, but we
corrupt the entry for second one. Since the index stores the
entries in sha1-sorted order, this means that the test must
make sure that the sha1 of the object we expect to be
corrupted ("$object") sorts after the other placeholder
object.
That commit used the HEAD commit as the placeholder, but the
script never calls test_tick. That means that the commit
object (and thus its sha1) depends on the timestamp when the
test script is run. This usually works in practice, because
the sha1 of $object starts with "fff". The commit object
will sort after that only 1 in 4096 times, but when it does
the test will fail.
One obvious solution is to add the test_tick call to get a
deterministic commit sha1. But since we're relying on the
sort order for the test to function, let's make that very
explicit by just generating a second blob with a known sha1.
Reported-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A v2 pack index file can specify an offset within a packfile
of up to 2^64-1 bytes. On a system with a signed 64-bit
off_t, we can represent only up to 2^63-1. This means that a
corrupted .idx file can end up with a negative offset in the
pack code. Our bounds-checking use_pack function looks for
too-large offsets, but not for ones that have wrapped around
to negative. Let's do so, which fixes an out-of-bounds
access demonstrated in t5313.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If a pack .idx file has a corrupted offset for an object, we
may try to access an offset in the .idx or .pack file that
is larger than the file's size. For the .pack case, we have
use_pack() to protect us, which realizes the access is out
of bounds. But if the corrupted value asks us to look in the
.idx file's secondary 64-bit offset table, we blindly add it
to the mmap'd index data and access arbitrary memory.
We can fix this with a simple bounds-check compared to the
size we found when we opened the .idx file.
Note that there's similar code in index-pack that is
triggered only during "index-pack --verify". To support
both, we pull the bounds-check into a separate function,
which dies when it sees a corrupted file.
It would be nice if we could return an error, so that the
pack code could try to find a good copy of the object
elsewhere. Currently nth_packed_object_offset doesn't have
any way to return an error, but it could probably use "0" as
a sentinel value (since no object can start there). This is
the minimal fix, and we can improve the resilience later on
top.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Our on-disk .pack and .idx files may reference other data by
offset. We should make sure that we are not fooled by
corrupt data into accessing memory outside of our mmap'd
boundaries.
This patch adds a series of tests for offsets found in .pack
and .idx files. For the most part we get this right, but
there are two tests of .idx files marked as failures: we do
not bounds-check offsets in the v2 index's extended offset
table, nor do we handle .idx offsets that overflow a signed
off_t.
With these tests, we should have good coverage of all
offsets found in these files. Note that this doesn't cover
.bitmap files, which may have similar bugs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Nguyễn Thái Ngọc Duy
Jeff King