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190 lines
6.1 KiB
190 lines
6.1 KiB
import binascii
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import base64
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class UnexpectedDER(Exception):
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pass
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def encode_constructed(tag, value):
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return chr(0xa0+tag) + encode_length(len(value)) + value
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def encode_integer(r):
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assert r >= 0 # can't support negative numbers yet
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h = "%x" % r
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if len(h)%2:
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h = "0" + h
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s = binascii.unhexlify(h)
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if ord(s[0]) <= 0x7f:
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return "\x02" + chr(len(s)) + s
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else:
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# DER integers are two's complement, so if the first byte is
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# 0x80-0xff then we need an extra 0x00 byte to prevent it from
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# looking negative.
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return "\x02" + chr(len(s)+1) + "\x00" + s
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def encode_bitstring(s):
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return "\x03" + encode_length(len(s)) + s
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def encode_octet_string(s):
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return "\x04" + encode_length(len(s)) + s
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def encode_oid(first, second, *pieces):
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assert first <= 2
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assert second <= 39
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encoded_pieces = [chr(40*first+second)] + [encode_number(p)
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for p in pieces]
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body = "".join(encoded_pieces)
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return "\x06" + encode_length(len(body)) + body
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def encode_sequence(*encoded_pieces):
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total_len = sum([len(p) for p in encoded_pieces])
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return "\x30" + encode_length(total_len) + "".join(encoded_pieces)
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def encode_number(n):
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b128_digits = []
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while n:
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b128_digits.insert(0, (n & 0x7f) | 0x80)
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n = n >> 7
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if not b128_digits:
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b128_digits.append(0)
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b128_digits[-1] &= 0x7f
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return "".join([chr(d) for d in b128_digits])
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def remove_constructed(string):
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s0 = ord(string[0])
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if (s0 & 0xe0) != 0xa0:
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raise UnexpectedDER("wanted constructed tag (0xa0-0xbf), got 0x%02x"
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% s0)
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tag = s0 & 0x1f
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length, llen = read_length(string[1:])
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body = string[1+llen:1+llen+length]
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rest = string[1+llen+length:]
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return tag, body, rest
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def remove_sequence(string):
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if not string.startswith("\x30"):
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raise UnexpectedDER("wanted sequence (0x30), got 0x%02x" %
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ord(string[0]))
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length, lengthlength = read_length(string[1:])
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endseq = 1+lengthlength+length
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return string[1+lengthlength:endseq], string[endseq:]
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def remove_octet_string(string):
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if not string.startswith("\x04"):
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raise UnexpectedDER("wanted octetstring (0x04), got 0x%02x" %
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ord(string[0]))
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length, llen = read_length(string[1:])
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body = string[1+llen:1+llen+length]
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rest = string[1+llen+length:]
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return body, rest
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def remove_object(string):
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if not string.startswith("\x06"):
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raise UnexpectedDER("wanted object (0x06), got 0x%02x" %
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ord(string[0]))
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length, lengthlength = read_length(string[1:])
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body = string[1+lengthlength:1+lengthlength+length]
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rest = string[1+lengthlength+length:]
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numbers = []
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while body:
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n, ll = read_number(body)
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numbers.append(n)
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body = body[ll:]
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n0 = numbers.pop(0)
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first = n0//40
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second = n0-(40*first)
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numbers.insert(0, first)
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numbers.insert(1, second)
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return tuple(numbers), rest
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def remove_integer(string):
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if not string.startswith("\x02"):
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raise UnexpectedDER("wanted integer (0x02), got 0x%02x" %
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ord(string[0]))
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length, llen = read_length(string[1:])
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numberbytes = string[1+llen:1+llen+length]
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rest = string[1+llen+length:]
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assert ord(numberbytes[0]) < 0x80 # can't support negative numbers yet
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return int(binascii.hexlify(numberbytes), 16), rest
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def read_number(string):
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number = 0
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llen = 0
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# base-128 big endian, with b7 set in all but the last byte
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while True:
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if llen > len(string):
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raise UnexpectedDER("ran out of length bytes")
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number = number << 7
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d = ord(string[llen])
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number += (d & 0x7f)
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llen += 1
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if not d & 0x80:
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break
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return number, llen
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def encode_length(l):
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assert l >= 0
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if l < 0x80:
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return chr(l)
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s = "%x" % l
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if len(s)%2:
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s = "0"+s
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s = binascii.unhexlify(s)
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llen = len(s)
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return chr(0x80|llen) + s
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def read_length(string):
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if not (ord(string[0]) & 0x80):
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# short form
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return (ord(string[0]) & 0x7f), 1
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# else long-form: b0&0x7f is number of additional base256 length bytes,
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# big-endian
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llen = ord(string[0]) & 0x7f
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if llen > len(string)-1:
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raise UnexpectedDER("ran out of length bytes")
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return int(binascii.hexlify(string[1:1+llen]), 16), 1+llen
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def remove_bitstring(string):
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if not string.startswith("\x03"):
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raise UnexpectedDER("wanted bitstring (0x03), got 0x%02x" %
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ord(string[0]))
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length, llen = read_length(string[1:])
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body = string[1+llen:1+llen+length]
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rest = string[1+llen+length:]
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return body, rest
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# SEQUENCE([1, STRING(secexp), cont[0], OBJECT(curvename), cont[1], BINTSTRING)
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# signatures: (from RFC3279)
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# ansi-X9-62 OBJECT IDENTIFIER ::= {
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# iso(1) member-body(2) us(840) 10045 }
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#
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# id-ecSigType OBJECT IDENTIFIER ::= {
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# ansi-X9-62 signatures(4) }
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# ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
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# id-ecSigType 1 }
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## so 1,2,840,10045,4,1
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## so 0x42, .. ..
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# Ecdsa-Sig-Value ::= SEQUENCE {
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# r INTEGER,
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# s INTEGER }
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# id-public-key-type OBJECT IDENTIFIER ::= { ansi-X9.62 2 }
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#
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# id-ecPublicKey OBJECT IDENTIFIER ::= { id-publicKeyType 1 }
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# I think the secp224r1 identifier is (t=06,l=05,v=2b81040021)
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# secp224r1 OBJECT IDENTIFIER ::= {
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# iso(1) identified-organization(3) certicom(132) curve(0) 33 }
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# and the secp384r1 is (t=06,l=05,v=2b81040022)
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# secp384r1 OBJECT IDENTIFIER ::= {
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# iso(1) identified-organization(3) certicom(132) curve(0) 34 }
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def unpem(pem):
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d = "".join([l.strip() for l in pem.split("\n")
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if l and not l.startswith("-----")])
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return base64.b64decode(d)
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def topem(der, name):
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b64 = base64.b64encode(der)
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lines = ["-----BEGIN %s-----\n" % name]
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lines.extend([b64[start:start+64]+"\n"
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for start in range(0, len(b64), 64)])
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lines.append("-----END %s-----\n" % name)
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return "".join(lines)
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