84 lines
2.4 KiB
Python
84 lines
2.4 KiB
Python
import io
|
|
import hashlib
|
|
import base64
|
|
import ecdsa
|
|
|
|
from . import util
|
|
|
|
import logging
|
|
log = logging.getLogger(__name__)
|
|
|
|
DER_OCTET_STRING = b'\x04'
|
|
|
|
curve = ecdsa.NIST256p
|
|
hashfunc = hashlib.sha256
|
|
|
|
|
|
def fingerprint(blob):
|
|
digest = hashlib.md5(blob).digest()
|
|
return ':'.join('{:02x}'.format(c) for c in bytearray(digest))
|
|
|
|
|
|
def parse_pubkey(blob):
|
|
s = io.BytesIO(blob)
|
|
key_type = util.read_frame(s)
|
|
log.debug('key type: %s', key_type)
|
|
curve_name = util.read_frame(s)
|
|
log.debug('curve name: %s', curve_name)
|
|
point = util.read_frame(s)
|
|
assert s.read() == b''
|
|
_type, point = point[:1], point[1:]
|
|
assert _type == DER_OCTET_STRING
|
|
size = len(point) // 2
|
|
assert len(point) == 2 * size
|
|
coords = (util.bytes2num(point[:size]), util.bytes2num(point[size:]))
|
|
log.debug('coordinates: %s', coords)
|
|
fp = fingerprint(blob)
|
|
|
|
point = ecdsa.ellipticcurve.Point(curve.curve, *coords)
|
|
vk = ecdsa.VerifyingKey.from_public_point(point, curve, hashfunc)
|
|
result = {
|
|
'point': coords,
|
|
'curve': curve_name,
|
|
'fingerprint': fp,
|
|
'type': key_type,
|
|
'blob': blob,
|
|
'size': size,
|
|
'verifying_key': vk
|
|
}
|
|
return result
|
|
|
|
|
|
def parse_public_key(data):
|
|
file_type, base64blob, name = data.split()
|
|
blob = base64.b64decode(base64blob)
|
|
result = parse_pubkey(blob)
|
|
result['name'] = name.encode('ascii')
|
|
assert result['type'] == file_type.encode('ascii')
|
|
log.debug('loaded %s %s', file_type, result['fingerprint'])
|
|
return result
|
|
|
|
|
|
def decompress_pubkey(pub):
|
|
P = curve.curve.p()
|
|
A = curve.curve.a()
|
|
B = curve.curve.b()
|
|
x = util.bytes2num(pub[1:33])
|
|
beta = pow(int(x*x*x+A*x+B), int((P+1)//4), int(P))
|
|
y = (P-beta) if ((beta + ord(pub[0])) % 2) else beta
|
|
return (x, y)
|
|
|
|
|
|
def export_public_key(pubkey, label):
|
|
x, y = decompress_pubkey(pubkey)
|
|
point = ecdsa.ellipticcurve.Point(curve.curve, x, y)
|
|
vk = ecdsa.VerifyingKey.from_public_point(point, curve=curve,
|
|
hashfunc=hashfunc)
|
|
key_type = 'ecdsa-sha2-nistp256'
|
|
curve_name = 'nistp256'
|
|
parts = [key_type, curve_name, DER_OCTET_STRING + vk.to_string()]
|
|
blob = ''.join([util.frame(p) for p in parts])
|
|
log.debug('fingerprint: %s', fingerprint(blob))
|
|
b64 = base64.b64encode(blob)
|
|
return '{} {} {}\n'.format(key_type, b64, label)
|