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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function
import pytest
from cryptography.hazmat._der import (
DERReader, INTEGER, NULL, OCTET_STRING, SEQUENCE, encode_der,
encode_der_integer
)
def test_der_reader_basic():
reader = DERReader(b"123456789")
assert reader.read_byte() == ord(b"1")
assert reader.read_bytes(1).tobytes() == b"2"
assert reader.read_bytes(4).tobytes() == b"3456"
with pytest.raises(ValueError):
reader.read_bytes(4)
assert reader.read_bytes(3).tobytes() == b"789"
# The input is now empty.
with pytest.raises(ValueError):
reader.read_bytes(1)
with pytest.raises(ValueError):
reader.read_byte()
def test_der():
# This input is the following structure, using
# https://github.com/google/der-ascii
#
# SEQUENCE {
# SEQUENCE {
# NULL {}
# INTEGER { 42 }
# OCTET_STRING { "hello" }
# }
# }
der = b"\x30\x0e\x30\x0c\x05\x00\x02\x01\x2a\x04\x05\x68\x65\x6c\x6c\x6f"
reader = DERReader(der)
with pytest.raises(ValueError):
reader.check_empty()
# Parse the outer element.
outer = reader.read_element(SEQUENCE)
reader.check_empty()
assert outer.data.tobytes() == der[2:]
# Parse the outer element with read_any_element.
reader = DERReader(der)
tag, outer2 = reader.read_any_element()
reader.check_empty()
assert tag == SEQUENCE
assert outer2.data.tobytes() == der[2:]
# Parse the outer element with read_single_element.
outer3 = DERReader(der).read_single_element(SEQUENCE)
assert outer3.data.tobytes() == der[2:]
# read_single_element rejects trailing data.
with pytest.raises(ValueError):
DERReader(der + der).read_single_element(SEQUENCE)
# Continue parsing the structure.
inner = outer.read_element(SEQUENCE)
outer.check_empty()
# Parsing a missing optional element should work.
assert inner.read_optional_element(INTEGER) is None
null = inner.read_element(NULL)
null.check_empty()
# Parsing a present optional element should work.
integer = inner.read_optional_element(INTEGER)
assert integer.as_integer() == 42
octet_string = inner.read_element(OCTET_STRING)
assert octet_string.data.tobytes() == b"hello"
# Parsing a missing optional element should work when the input is empty.
inner.check_empty()
assert inner.read_optional_element(INTEGER) is None
# Re-encode the same structure.
der2 = encode_der(
SEQUENCE,
encode_der(
SEQUENCE,
encode_der(NULL),
encode_der(INTEGER, encode_der_integer(42)),
encode_der(OCTET_STRING, b"hello"),
)
)
assert der2 == der
@pytest.mark.parametrize(
"length,header",
[
# Single-byte lengths.
(0, b"\x04\x00"),
(1, b"\x04\x01"),
(2, b"\x04\x02"),
(127, b"\x04\x7f"),
# Long-form lengths.
(128, b"\x04\x81\x80"),
(129, b"\x04\x81\x81"),
(255, b"\x04\x81\xff"),
(0x100, b"\x04\x82\x01\x00"),
(0x101, b"\x04\x82\x01\x01"),
(0xffff, b"\x04\x82\xff\xff"),
(0x10000, b"\x04\x83\x01\x00\x00"),
]
)
def test_der_lengths(length, header):
body = length * b"a"
der = header + body
reader = DERReader(der)
element = reader.read_element(OCTET_STRING)
reader.check_empty()
assert element.data.tobytes() == body
assert encode_der(OCTET_STRING, body) == der
@pytest.mark.parametrize(
"bad_input",
[
# The input ended before the tag.
b"",
# The input ended before the length.
b"\x30",
# The input ended before the second byte of the length.
b"\x30\x81",
# The input ended before the body.
b"\x30\x01",
# The length used long form when it should be short form.
b"\x30\x81\x01\x00",
# The length was not minimally-encoded.
b"\x30\x82\x00\x80" + (0x80 * b"a"),
# Indefinite-length encoding is not valid DER.
b"\x30\x80\x00\x00"
# Tag number (the bottom 5 bits) 31 indicates long form tags, which we
# do not support.
b"\x1f\x00",
b"\x9f\x00",
b"\xbf\x00",
b"\xff\x00",
]
)
def test_der_reader_bad_input(bad_input):
reader = DERReader(bad_input)
with pytest.raises(ValueError):
reader.read_any_element()
def test_der_reader_wrong_tag():
reader = DERReader(b"\x04\x00")
with pytest.raises(ValueError):
reader.read_element(SEQUENCE)
@pytest.mark.parametrize(
"value,der",
[
(0, b'\x00'),
(1, b'\x01'),
(2, b'\x02'),
(3, b'\x03'),
(127, b'\x7f'),
(128, b'\x00\x80'),
(0x112233445566778899aabbccddeeff,
b'\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff'),
]
)
def test_integer(value, der):
assert encode_der_integer(value) == der
assert DERReader(der).as_integer() == value
@pytest.mark.parametrize(
"bad_input",
[
# Zero is encoded as b"\x00", not the empty string.
b"",
# Too many leading zeros.
b"\x00\x00",
b"\x00\x7f",
# Too many leading ones.
b"\xff\xff",
b"\xff\x80",
# Negative integers are not supported.
b"\x80",
b"\x81",
b"\x80\x00\x00",
b"\xff",
]
)
def test_invalid_integer(bad_input):
reader = DERReader(bad_input)
with pytest.raises(ValueError):
reader.as_integer()
def test_invalid_integer_encode():
with pytest.raises(ValueError):
encode_der_integer(-1)
with pytest.raises(ValueError):
encode_der_integer("not an integer")
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