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Fix bug with ECDSA p521 curves #153

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Merged
merged 1 commit into from
Jun 10, 2020
+13 −3
Merged

Fix bug with ECDSA p521 curves #153

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6 changes: 3 additions & 3 deletions signxml/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@

from .exceptions import InvalidSignature, InvalidDigest, InvalidInput, InvalidCertificate # noqa
from .util import (bytes_to_long, long_to_bytes, strip_pem_header, add_pem_header, ensure_bytes, ensure_str, Namespace,
XMLProcessor, iterate_pem, verify_x509_cert_chain)
XMLProcessor, iterate_pem, verify_x509_cert_chain, bits_to_bytes_unit)
from collections import namedtuple

methods = Enum("Methods", "enveloped enveloping detached")
Expand Down Expand Up @@ -382,7 +382,7 @@ def sign(self, data, key=None, passphrase=None, cert=None, reference_uri=None, k
if self.sign_alg.startswith("dsa-") or self.sign_alg.startswith("ecdsa-"):
# Note: The output of the DSA and ECDSA signers is a DER-encoded ASN.1 sequence of two DER integers.
(r, s) = utils.decode_dss_signature(signature)
int_len = key.key_size // 8
int_len = bits_to_bytes_unit(key.key_size)
signature = long_to_bytes(r, blocksize=int_len) + long_to_bytes(s, blocksize=int_len)

signature_value_element.text = ensure_str(b64encode(signature))
Expand Down Expand Up @@ -585,7 +585,7 @@ def _verify_signature_with_pubkey(self, signed_info_c14n, raw_signature, key_val
raise NotImplementedError()

def _encode_dss_signature(self, raw_signature, key_size_bits):
want_raw_signature_len = key_size_bits // 8 * 2
want_raw_signature_len = bits_to_bytes_unit(key_size_bits) * 2
if len(raw_signature) != want_raw_signature_len:
raise InvalidSignature(
"Expected %d byte SignatureValue, got %d"
Expand Down
10 changes: 10 additions & 0 deletions signxml/util/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

from __future__ import absolute_import, division, print_function, unicode_literals

import math
import os, sys, re, struct, textwrap
from xml.etree import ElementTree as stdlibElementTree
from base64 import b64encode, b64decode
Expand Down Expand Up @@ -92,6 +93,15 @@ def long_to_bytes(n, blocksize=0):
return s


def bits_to_bytes_unit(num_of_bits):
"""bits_to_bytes_unit(num_of_bits:int) : int
Convert the unit of measurement for the argument from bits to bytes.

Rounds up to the nearest whole byte.
"""
return int(math.ceil(num_of_bits / 8))


pem_regexp = re.compile("{header}{nl}(.+?){footer}".format(header=PEM_HEADER, nl="\r{0,1}\n", footer=PEM_FOOTER),
flags=re.S)

Expand Down