* Remove non-test dependencies on asn1crypto.
cryptography.io actually contains two OpenSSL bindings right now, the
expected cffi one, and an optional one hidden in asn1crypto. asn1crypto
contains a lot of things that cryptography.io doesn't use, including a
BER parser and a hand-rolled and not constant-time EC implementation.
Instead, check in a much small DER-only parser in cryptography/hazmat. A
quick benchmark suggests this parser is also faster than asn1crypto:
from __future__ import absolute_import, division, print_function
import timeit
print(timeit.timeit(
"decode_dss_signature(sig)",
setup=r"""
from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature
sig=b"\x30\x2d\x02\x15\x00\xb5\xaf\x30\x78\x67\xfb\x8b\x54\x39\x00\x13\xcc\x67\x02\x0d\xdf\x1f\x2c\x0b\x81\x02\x14\x62\x0d\x3b\x22\xab\x50\x31\x44\x0c\x3e\x35\xea\xb6\xf4\x81\x29\x8f\x9e\x9f\x08"
""",
number=10000))
Python 2.7:
asn1crypto: 0.25
_der.py: 0.098
Python 3.5:
asn1crypto: 0.17
_der.py: 0.10
* Remove test dependencies on asn1crypto.
The remaining use of asn1crypto was some sanity-checking of
Certificates. Add a minimal X.509 parser to extract the relevant fields.
* Add a read_single_element helper function.
The outermost read is a little tedious.
* Address flake8 warnings
* Fix test for long-form vs short-form lengths.
Testing a zero length trips both this check and the non-minimal long
form check. Use a one-byte length to cover the missing branch.
* Remove support for negative integers.
These never come up in valid signatures. Note, however, this does
change public API.
* Update src/cryptography/hazmat/primitives/asymmetric/utils.py
Co-Authored-By: Alex Gaynor <alex.gaynor@gmail.com>
* Review comments
* Avoid hardcoding the serialization of NULL in decode_asn1.py too.