tests/test-lfs-pointer.py

dirs: fix out-of-bounds access in Py3

The hack for mutating Python's variable-length integers that was
ported to py3 in cb3048746dae (dirs: port PyInt code to work on Python
3, 2016-10-08) was reading from ob_digit[1] instead of ob_digit[0] for
some reason. Space for ob_digit[1] would only be allocated for
integers larger than 30 bits, so we ended up writing to unallocated
memory. Also, we would write an integer that's 2^30 times too large,
so we would never free these integers.

Found by AddressSanitizer.

Differential Revision: https://phab.mercurial-scm.org/D7597

from __future__ import absolute_import, print_function

# Import something from Mercurial, so the module loader gets initialized.
from mercurial import pycompat

del pycompat  # unused for now

from hgext.lfs import pointer


def tryparse(text):
    r = {}
    try:
        r = pointer.deserialize(text)
        print('ok')
    except Exception as ex:
        print((b'%s' % ex).decode('ascii'))
    if r:
        text2 = r.serialize()
        if text2 != text:
            print('reconstructed text differs')
    return r


t = (
    b'version https://git-lfs.github.com/spec/v1\n'
    b'oid sha256:4d7a214614ab2935c943f9e0ff69d22eadbb8f32b1'
    b'258daaa5e2ca24d17e2393\n'
    b'size 12345\n'
    b'x-foo extra-information\n'
)

tryparse(b'')
tryparse(t)
tryparse(t.replace(b'git-lfs', b'unknown'))
tryparse(t.replace(b'v1\n', b'v1\n\n'))
tryparse(t.replace(b'sha256', b'ahs256'))
tryparse(t.replace(b'sha256:', b''))
tryparse(t.replace(b'12345', b'0x12345'))
tryparse(t.replace(b'extra-information', b'extra\0information'))
tryparse(t.replace(b'extra-information', b'extra\ninformation'))
tryparse(t.replace(b'x-foo', b'x_foo'))
tryparse(t.replace(b'oid', b'blobid'))
tryparse(t.replace(b'size', b'size-bytes').replace(b'oid', b'object-id'))