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Diffstat (limited to 'frozen_deps/ecdsa/der.py')
| -rw-r--r-- | frozen_deps/ecdsa/der.py | 409 |
1 files changed, 409 insertions, 0 deletions
diff --git a/frozen_deps/ecdsa/der.py b/frozen_deps/ecdsa/der.py new file mode 100644 index 0000000..8c1de9b --- /dev/null +++ b/frozen_deps/ecdsa/der.py @@ -0,0 +1,409 @@ +from __future__ import division + +import binascii +import base64 +import warnings +from itertools import chain +from six import int2byte, b, text_type +from ._compat import str_idx_as_int + + +class UnexpectedDER(Exception): + pass + + +def encode_constructed(tag, value): + return int2byte(0xA0 + tag) + encode_length(len(value)) + value + + +def encode_integer(r): + assert r >= 0 # can't support negative numbers yet + h = ("%x" % r).encode() + if len(h) % 2: + h = b("0") + h + s = binascii.unhexlify(h) + num = str_idx_as_int(s, 0) + if num <= 0x7F: + return b("\x02") + encode_length(len(s)) + s + else: + # DER integers are two's complement, so if the first byte is + # 0x80-0xff then we need an extra 0x00 byte to prevent it from + # looking negative. + return b("\x02") + encode_length(len(s) + 1) + b("\x00") + s + + +# sentry object to check if an argument was specified (used to detect +# deprecated calling convention) +_sentry = object() + + +def encode_bitstring(s, unused=_sentry): + """ + Encode a binary string as a BIT STRING using :term:`DER` encoding. + + Note, because there is no native Python object that can encode an actual + bit string, this function only accepts byte strings as the `s` argument. + The byte string is the actual bit string that will be encoded, padded + on the right (least significant bits, looking from big endian perspective) + to the first full byte. If the bit string has a bit length that is multiple + of 8, then the padding should not be included. For correct DER encoding + the padding bits MUST be set to 0. + + Number of bits of padding need to be provided as the `unused` parameter. + In case they are specified as None, it means the number of unused bits + is already encoded in the string as the first byte. + + The deprecated call convention specifies just the `s` parameters and + encodes the number of unused bits as first parameter (same convention + as with None). + + Empty string must be encoded with `unused` specified as 0. + + Future version of python-ecdsa will make specifying the `unused` argument + mandatory. + + :param s: bytes to encode + :type s: bytes like object + :param unused: number of bits at the end of `s` that are unused, must be + between 0 and 7 (inclusive) + :type unused: int or None + + :raises ValueError: when `unused` is too large or too small + + :return: `s` encoded using DER + :rtype: bytes + """ + encoded_unused = b"" + len_extra = 0 + if unused is _sentry: + warnings.warn( + "Legacy call convention used, unused= needs to be specified", + DeprecationWarning, + ) + elif unused is not None: + if not 0 <= unused <= 7: + raise ValueError("unused must be integer between 0 and 7") + if unused: + if not s: + raise ValueError("unused is non-zero but s is empty") + last = str_idx_as_int(s, -1) + if last & (2 ** unused - 1): + raise ValueError("unused bits must be zeros in DER") + encoded_unused = int2byte(unused) + len_extra = 1 + return b("\x03") + encode_length(len(s) + len_extra) + encoded_unused + s + + +def encode_octet_string(s): + return b("\x04") + encode_length(len(s)) + s + + +def encode_oid(first, second, *pieces): + assert 0 <= first < 2 and 0 <= second <= 39 or first == 2 and 0 <= second + body = b"".join( + chain( + [encode_number(40 * first + second)], + (encode_number(p) for p in pieces), + ) + ) + return b"\x06" + encode_length(len(body)) + body + + +def encode_sequence(*encoded_pieces): + total_len = sum([len(p) for p in encoded_pieces]) + return b("\x30") + encode_length(total_len) + b("").join(encoded_pieces) + + +def encode_number(n): + b128_digits = [] + while n: + b128_digits.insert(0, (n & 0x7F) | 0x80) + n = n >> 7 + if not b128_digits: + b128_digits.append(0) + b128_digits[-1] &= 0x7F + return b("").join([int2byte(d) for d in b128_digits]) + + +def is_sequence(string): + return string and string[:1] == b"\x30" + + +def remove_constructed(string): + s0 = str_idx_as_int(string, 0) + if (s0 & 0xE0) != 0xA0: + 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] + rest = string[1 + llen + length :] + return tag, body, rest + + +def remove_sequence(string): + if not string: + raise UnexpectedDER("Empty string does not encode a sequence") + if string[:1] != b"\x30": + n = str_idx_as_int(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:] + + +def remove_octet_string(string): + if string[:1] != b"\x04": + n = str_idx_as_int(string, 0) + 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 :] + return body, rest + + +def remove_object(string): + if not string: + raise UnexpectedDER( + "Empty string does not encode an object identifier" + ) + if string[:1] != b"\x06": + n = str_idx_as_int(string, 0) + 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 :] + if not body: + raise UnexpectedDER("Empty object identifier") + if len(body) != length: + raise UnexpectedDER( + "Length of object identifier longer than the provided buffer" + ) + numbers = [] + while body: + n, ll = read_number(body) + numbers.append(n) + body = body[ll:] + n0 = numbers.pop(0) + if n0 < 80: + first = n0 // 40 + else: + first = 2 + second = n0 - (40 * first) + numbers.insert(0, first) + numbers.insert(1, second) + return tuple(numbers), rest + + +def remove_integer(string): + if not string: + raise UnexpectedDER( + "Empty string is an invalid encoding of an integer" + ) + if string[:1] != b"\x02": + n = str_idx_as_int(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 :] + msb = str_idx_as_int(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 = str_idx_as_int(numberbytes, 1) + if smsb < 0x80: + raise UnexpectedDER( + "Invalid encoding of integer, unnecessary " + "zero padding bytes" + ) + return int(binascii.hexlify(numberbytes), 16), rest + + +def read_number(string): + number = 0 + llen = 0 + if str_idx_as_int(string, 0) == 0x80: + raise UnexpectedDER("Non minimal encoding of OID subidentifier") + # base-128 big endian, with most significant bit set in all but the last + # byte + while True: + if llen >= len(string): + raise UnexpectedDER("ran out of length bytes") + number = number << 7 + d = str_idx_as_int(string, llen) + number += d & 0x7F + llen += 1 + if not d & 0x80: + break + return number, llen + + +def encode_length(l): + assert l >= 0 + if l < 0x80: + return int2byte(l) + s = ("%x" % l).encode() + if len(s) % 2: + s = b("0") + s + s = binascii.unhexlify(s) + llen = len(s) + return int2byte(0x80 | llen) + s + + +def read_length(string): + if not string: + raise UnexpectedDER("Empty string can't encode valid length value") + num = str_idx_as_int(string, 0) + if not (num & 0x80): + # short form + return (num & 0x7F), 1 + # 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("Length of length longer than provided buffer") + # verify that the encoding is minimal possible (DER requirement) + msb = str_idx_as_int(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 + + +def remove_bitstring(string, expect_unused=_sentry): + """ + Remove a BIT STRING object from `string` following :term:`DER`. + + The `expect_unused` can be used to specify if the bit string should + have the amount of unused bits decoded or not. If it's an integer, any + read BIT STRING that has number of unused bits different from specified + value will cause UnexpectedDER exception to be raised (this is especially + useful when decoding BIT STRINGS that have DER encoded object in them; + DER encoding is byte oriented, so the unused bits will always equal 0). + + If the `expect_unused` is specified as None, the first element returned + will be a tuple, with the first value being the extracted bit string + while the second value will be the decoded number of unused bits. + + If the `expect_unused` is unspecified, the decoding of byte with + number of unused bits will not be attempted and the bit string will be + returned as-is, the callee will be required to decode it and verify its + correctness. + + Future version of python will require the `expected_unused` parameter + to be specified. + + :param string: string of bytes to extract the BIT STRING from + :type string: bytes like object + :param expect_unused: number of bits that should be unused in the BIT + STRING, or None, to return it to caller + :type expect_unused: int or None + + :raises UnexpectedDER: when the encoding does not follow DER. + + :return: a tuple with first element being the extracted bit string and + the second being the remaining bytes in the string (if any); if the + `expect_unused` is specified as None, the first element of the returned + tuple will be a tuple itself, with first element being the bit string + as bytes and the second element being the number of unused bits at the + end of the byte array as an integer + :rtype: tuple + """ + if not string: + raise UnexpectedDER("Empty string does not encode a bitstring") + if expect_unused is _sentry: + warnings.warn( + "Legacy call convention used, expect_unused= needs to be" + " specified", + DeprecationWarning, + ) + num = str_idx_as_int(string, 0) + if string[:1] != b"\x03": + raise UnexpectedDER("wanted bitstring (0x03), got 0x%02x" % num) + length, llen = read_length(string[1:]) + if not length: + raise UnexpectedDER("Invalid length of bit string, can't be 0") + body = string[1 + llen : 1 + llen + length] + rest = string[1 + llen + length :] + if expect_unused is not _sentry: + unused = str_idx_as_int(body, 0) + if not 0 <= unused <= 7: + raise UnexpectedDER("Invalid encoding of unused bits") + if expect_unused is not None and expect_unused != unused: + raise UnexpectedDER("Unexpected number of unused bits") + body = body[1:] + if unused: + if not body: + raise UnexpectedDER("Invalid encoding of empty bit string") + last = str_idx_as_int(body, -1) + # verify that all the unused bits are set to zero (DER requirement) + if last & (2 ** unused - 1): + raise UnexpectedDER("Non zero padding bits in bit string") + if expect_unused is None: + body = (body, unused) + return body, rest + + +# SEQUENCE([1, STRING(secexp), cont[0], OBJECT(curvename), cont[1], BINTSTRING) + + +# signatures: (from RFC3279) +# ansi-X9-62 OBJECT IDENTIFIER ::= { +# iso(1) member-body(2) us(840) 10045 } +# +# id-ecSigType OBJECT IDENTIFIER ::= { +# ansi-X9-62 signatures(4) } +# ecdsa-with-SHA1 OBJECT IDENTIFIER ::= { +# id-ecSigType 1 } +# so 1,2,840,10045,4,1 +# so 0x42, .. .. + +# Ecdsa-Sig-Value ::= SEQUENCE { +# r INTEGER, +# s INTEGER } + +# id-public-key-type OBJECT IDENTIFIER ::= { ansi-X9.62 2 } +# +# id-ecPublicKey OBJECT IDENTIFIER ::= { id-publicKeyType 1 } + +# I think the secp224r1 identifier is (t=06,l=05,v=2b81040021) +# secp224r1 OBJECT IDENTIFIER ::= { +# iso(1) identified-organization(3) certicom(132) curve(0) 33 } +# and the secp384r1 is (t=06,l=05,v=2b81040022) +# secp384r1 OBJECT IDENTIFIER ::= { +# iso(1) identified-organization(3) certicom(132) curve(0) 34 } + + +def unpem(pem): + if isinstance(pem, text_type): + pem = pem.encode() + + d = b("").join( + [ + l.strip() + for l in pem.split(b("\n")) + if l and not l.startswith(b("-----")) + ] + ) + return base64.b64decode(d) + + +def topem(der, name): + b64 = base64.b64encode(der) + lines = [("-----BEGIN %s-----\n" % name).encode()] + lines.extend( + [b64[start : start + 64] + b("\n") for start in range(0, len(b64), 64)] + ) + lines.append(("-----END %s-----\n" % name).encode()) + return b("").join(lines) |