diff --git a/.travis.yml b/.travis.yml index 2aec5d1f..9151a873 100644 --- a/.travis.yml +++ b/.travis.yml @@ -1,3 +1,6 @@ +# workaround for 3.7 not available in default configuration +# travis-ci/travis-ci#9815 +dist: trusty sudo: false language: python cache: pip diff --git a/build-requirements-2.6.txt b/build-requirements-2.6.txt index de0022ee..980e00df 100644 --- a/build-requirements-2.6.txt +++ b/build-requirements-2.6.txt @@ -1,3 +1,4 @@ tox coveralls<1.3.0 idna<2.8 +unittest2 diff --git a/src/ecdsa/der.py b/src/ecdsa/der.py index f7a587ab..3ed7f6c3 100644 --- a/src/ecdsa/der.py +++ b/src/ecdsa/der.py @@ -65,8 +65,8 @@ def encode_number(n): def remove_constructed(string): s0 = string[0] if isinstance(string[0], integer_types) else ord(string[0]) if (s0 & 0xe0) != 0xa0: - raise UnexpectedDER("wanted constructed tag (0xa0-0xbf), got 0x%02x" - % s0) + raise UnexpectedDER("wanted type 'constructed tag' (0xa0-0xbf), " + "got 0x%02x" % s0) tag = s0 & 0x1f length, llen = read_length(string[1:]) body = string[1+llen:1+llen+length] @@ -75,10 +75,15 @@ def remove_constructed(string): def remove_sequence(string): + if not string: + raise UnexpectedDER("Empty string does not encode a sequence") if not string.startswith(b("\x30")): - n = string[0] if isinstance(string[0], integer_types) else ord(string[0]) - raise UnexpectedDER("wanted sequence (0x30), got 0x%02x" % n) + n = string[0] if isinstance(string[0], integer_types) else \ + ord(string[0]) + raise UnexpectedDER("wanted type 'sequence' (0x30), got 0x%02x" % n) length, lengthlength = read_length(string[1:]) + if length > len(string) - 1 - lengthlength: + raise UnexpectedDER("Length longer than the provided buffer") endseq = 1+lengthlength+length return string[1+lengthlength:endseq], string[endseq:] @@ -86,7 +91,7 @@ def remove_sequence(string): def remove_octet_string(string): if not string.startswith(b("\x04")): n = string[0] if isinstance(string[0], integer_types) else ord(string[0]) - raise UnexpectedDER("wanted octetstring (0x04), got 0x%02x" % n) + raise UnexpectedDER("wanted type 'octetstring' (0x04), got 0x%02x" % n) length, llen = read_length(string[1:]) body = string[1+llen:1+llen+length] rest = string[1+llen+length:] @@ -96,7 +101,7 @@ def remove_octet_string(string): def remove_object(string): if not string.startswith(b("\x06")): n = string[0] if isinstance(string[0], integer_types) else ord(string[0]) - raise UnexpectedDER("wanted object (0x06), got 0x%02x" % n) + raise UnexpectedDER("wanted type 'object' (0x06), got 0x%02x" % n) length, lengthlength = read_length(string[1:]) body = string[1+lengthlength:1+lengthlength+length] rest = string[1+lengthlength+length:] @@ -114,14 +119,33 @@ def remove_object(string): def remove_integer(string): + if not string: + raise UnexpectedDER("Empty string is an invalid encoding of an " + "integer") if not string.startswith(b("\x02")): - n = string[0] if isinstance(string[0], integer_types) else ord(string[0]) - raise UnexpectedDER("wanted integer (0x02), got 0x%02x" % n) + n = string[0] if isinstance(string[0], integer_types) \ + else ord(string[0]) + raise UnexpectedDER("wanted type 'integer' (0x02), got 0x%02x" % n) length, llen = read_length(string[1:]) + if length > len(string) - 1 - llen: + raise UnexpectedDER("Length longer than provided buffer") + if length == 0: + raise UnexpectedDER("0-byte long encoding of integer") numberbytes = string[1+llen:1+llen+length] rest = string[1+llen+length:] - nbytes = numberbytes[0] if isinstance(numberbytes[0], integer_types) else ord(numberbytes[0]) - assert nbytes < 0x80 # can't support negative numbers yet + msb = numberbytes[0] if isinstance(numberbytes[0], integer_types) \ + else ord(numberbytes[0]) + if not msb < 0x80: + raise UnexpectedDER("Negative integers are not supported") + # check if the encoding is the minimal one (DER requirement) + if length > 1 and not msb: + # leading zero byte is allowed if the integer would have been + # considered a negative number otherwise + smsb = numberbytes[1] if isinstance(numberbytes[1], integer_types) \ + else ord(numberbytes[1]) + if smsb < 0x80: + raise UnexpectedDER("Invalid encoding of integer, unnecessary " + "zero padding bytes") return int(binascii.hexlify(numberbytes), 16), rest @@ -154,6 +178,8 @@ def encode_length(l): def read_length(string): + if not string: + raise UnexpectedDER("Empty string can't encode valid length value") num = string[0] if isinstance(string[0], integer_types) else ord(string[0]) if not (num & 0x80): # short form @@ -161,8 +187,14 @@ def read_length(string): # else long-form: b0&0x7f is number of additional base256 length bytes, # big-endian llen = num & 0x7f + if not llen: + raise UnexpectedDER("Invalid length encoding, length of length is 0") if llen > len(string)-1: - raise UnexpectedDER("ran out of length bytes") + raise UnexpectedDER("Length of length longer than provided buffer") + # verify that the encoding is minimal possible (DER requirement) + msb = string[1] if isinstance(string[1], integer_types) else ord(string[1]) + if not msb or llen == 1 and msb < 0x80: + raise UnexpectedDER("Not minimal encoding of length") return int(binascii.hexlify(string[1:1+llen]), 16), 1+llen diff --git a/src/ecdsa/keys.py b/src/ecdsa/keys.py index aabc6b46..587d1d6c 100644 --- a/src/ecdsa/keys.py +++ b/src/ecdsa/keys.py @@ -7,7 +7,7 @@ from .ecdsa import RSZeroError from .util import string_to_number, number_to_string, randrange from .util import sigencode_string, sigdecode_string -from .util import oid_ecPublicKey, encoded_oid_ecPublicKey +from .util import oid_ecPublicKey, encoded_oid_ecPublicKey, MalformedSignature from six import PY3, b from hashlib import sha1 @@ -136,11 +136,14 @@ def verify_digest(self, signature, digest, sigdecode=sigdecode_string): "for your digest (%d)" % (self.curve.name, 8 * len(digest))) number = string_to_number(digest) - r, s = sigdecode(signature, self.pubkey.order) + try: + r, s = sigdecode(signature, self.pubkey.order) + except (der.UnexpectedDER, MalformedSignature) as e: + raise BadSignatureError("Malformed formatting of signature", e) sig = ecdsa.Signature(r, s) if self.pubkey.verifies(number, sig): return True - raise BadSignatureError + raise BadSignatureError("Signature verification failed") class SigningKey: diff --git a/src/ecdsa/test_der.py b/src/ecdsa/test_der.py new file mode 100644 index 00000000..76bdfd46 --- /dev/null +++ b/src/ecdsa/test_der.py @@ -0,0 +1,94 @@ + +# compatibility with Python 2.6, for that we need unittest2 package, +# which is not available on 3.3 or 3.4 +try: + import unittest2 as unittest +except ImportError: + import unittest +from .der import remove_integer, UnexpectedDER, read_length +from six import b + +class TestRemoveInteger(unittest.TestCase): + # DER requires the integers to be 0-padded only if they would be + # interpreted as negative, check if those errors are detected + def test_non_minimal_encoding(self): + with self.assertRaises(UnexpectedDER): + remove_integer(b('\x02\x02\x00\x01')) + + def test_negative_with_high_bit_set(self): + with self.assertRaises(UnexpectedDER): + remove_integer(b('\x02\x01\x80')) + + def test_minimal_with_high_bit_set(self): + val, rem = remove_integer(b('\x02\x02\x00\x80')) + + self.assertEqual(val, 0x80) + self.assertFalse(rem) + + def test_two_zero_bytes_with_high_bit_set(self): + with self.assertRaises(UnexpectedDER): + remove_integer(b('\x02\x03\x00\x00\xff')) + + def test_zero_length_integer(self): + with self.assertRaises(UnexpectedDER): + remove_integer(b('\x02\x00')) + + def test_empty_string(self): + with self.assertRaises(UnexpectedDER): + remove_integer(b('')) + + def test_encoding_of_zero(self): + val, rem = remove_integer(b('\x02\x01\x00')) + + self.assertEqual(val, 0) + self.assertFalse(rem) + + def test_encoding_of_127(self): + val, rem = remove_integer(b('\x02\x01\x7f')) + + self.assertEqual(val, 127) + self.assertFalse(rem) + + def test_encoding_of_128(self): + val, rem = remove_integer(b('\x02\x02\x00\x80')) + + self.assertEqual(val, 128) + self.assertFalse(rem) + + +class TestReadLength(unittest.TestCase): + # DER requires the lengths between 0 and 127 to be encoded using the short + # form and lengths above that encoded with minimal number of bytes + # necessary + def test_zero_length(self): + self.assertEqual((0, 1), read_length(b('\x00'))) + + def test_two_byte_zero_length(self): + with self.assertRaises(UnexpectedDER): + read_length(b('\x81\x00')) + + def test_two_byte_small_length(self): + with self.assertRaises(UnexpectedDER): + read_length(b('\x81\x7f')) + + def test_long_form_with_zero_length(self): + with self.assertRaises(UnexpectedDER): + read_length(b('\x80')) + + def test_smallest_two_byte_length(self): + self.assertEqual((128, 2), read_length(b('\x81\x80'))) + + def test_zero_padded_length(self): + with self.assertRaises(UnexpectedDER): + read_length(b('\x82\x00\x80')) + + def test_two_three_byte_length(self): + self.assertEqual((256, 3), read_length(b'\x82\x01\x00')) + + def test_empty_string(self): + with self.assertRaises(UnexpectedDER): + read_length(b('')) + + def test_length_overflow(self): + with self.assertRaises(UnexpectedDER): + read_length(b('\x83\x01\x00')) diff --git a/src/ecdsa/test_malformed_sigs.py b/src/ecdsa/test_malformed_sigs.py new file mode 100644 index 00000000..fffb1b3b --- /dev/null +++ b/src/ecdsa/test_malformed_sigs.py @@ -0,0 +1,87 @@ +from __future__ import with_statement, division + +import pytest +import hashlib + +from six import b, binary_type +from .keys import SigningKey, VerifyingKey +from .keys import BadSignatureError +from .util import sigencode_der, sigencode_string +from .util import sigdecode_der, sigdecode_string +from .curves import curves, NIST256p, NIST521p + +der_sigs = [] +example_data = b("some data to sign") + +# Just NIST256p with SHA256 is 560 test cases, all curves with all hashes is +# few thousand slow test cases; execute the most interesting only + +#for curve in curves: +for curve in [NIST521p]: + #for hash_alg in ["md5", "sha1", "sha224", "sha256", "sha384", "sha512"]: + for hash_alg in ["sha256"]: + key = SigningKey.generate(curve) + signature = key.sign(example_data, hashfunc=getattr(hashlib, hash_alg), + sigencode=sigencode_der) + for pos in range(len(signature)): + for xor in (1<