You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
277 lines
9.1 KiB
Python
277 lines
9.1 KiB
Python
"""GPG protocol utilities."""
|
|
|
|
import base64
|
|
import hashlib
|
|
import logging
|
|
import struct
|
|
|
|
from .. import formats, util
|
|
|
|
log = logging.getLogger(__name__)
|
|
|
|
|
|
def packet(tag, blob):
|
|
"""Create small GPG packet."""
|
|
assert len(blob) < 2**32
|
|
|
|
if len(blob) < 2**8:
|
|
length_type = 0
|
|
elif len(blob) < 2**16:
|
|
length_type = 1
|
|
else:
|
|
length_type = 2
|
|
|
|
fmt = ['>B', '>H', '>L'][length_type]
|
|
leading_byte = 0x80 | (tag << 2) | (length_type)
|
|
return struct.pack('>B', leading_byte) + util.prefix_len(fmt, blob)
|
|
|
|
|
|
def subpacket(subpacket_type, fmt, *values):
|
|
"""Create GPG subpacket."""
|
|
blob = struct.pack(fmt, *values) if values else fmt
|
|
return struct.pack('>B', subpacket_type) + blob
|
|
|
|
|
|
def subpacket_long(subpacket_type, value):
|
|
"""Create GPG subpacket with 32-bit unsigned integer."""
|
|
return subpacket(subpacket_type, '>L', value)
|
|
|
|
|
|
def subpacket_time(value):
|
|
"""Create GPG subpacket with time in seconds (since Epoch)."""
|
|
return subpacket_long(2, value)
|
|
|
|
|
|
def subpacket_byte(subpacket_type, value):
|
|
"""Create GPG subpacket with 8-bit unsigned integer."""
|
|
return subpacket(subpacket_type, '>B', value)
|
|
|
|
|
|
def subpacket_bytes(subpacket_type, values):
|
|
"""Create GPG subpacket with 8-bit unsigned integers."""
|
|
return subpacket(subpacket_type, '>' + 'B'*len(values), *values)
|
|
|
|
|
|
def subpacket_prefix_len(item):
|
|
"""Prefix subpacket length according to RFC 4880 section-5.2.3.1."""
|
|
n = len(item)
|
|
if n >= 8384:
|
|
prefix = b'\xFF' + struct.pack('>L', n)
|
|
elif n >= 192:
|
|
n = n - 192
|
|
prefix = struct.pack('BB', (n // 256) + 192, n % 256)
|
|
else:
|
|
prefix = struct.pack('B', n)
|
|
return prefix + item
|
|
|
|
|
|
def subpackets(*items):
|
|
"""Serialize several GPG subpackets."""
|
|
prefixed = [subpacket_prefix_len(item) for item in items]
|
|
return util.prefix_len('>H', b''.join(prefixed))
|
|
|
|
|
|
def mpi(value):
|
|
"""Serialize multipresicion integer using GPG format."""
|
|
bits = value.bit_length()
|
|
data_size = (bits + 7) // 8
|
|
data_bytes = bytearray(data_size)
|
|
for i in range(data_size):
|
|
data_bytes[i] = value & 0xFF
|
|
value = value >> 8
|
|
|
|
data_bytes.reverse()
|
|
return struct.pack('>H', bits) + bytes(data_bytes)
|
|
|
|
|
|
def _serialize_nist256(vk):
|
|
return mpi((4 << 512) |
|
|
(vk.pubkey.point.x() << 256) |
|
|
(vk.pubkey.point.y()))
|
|
|
|
|
|
def _serialize_ed25519(vk):
|
|
return mpi((0x40 << 256) |
|
|
util.bytes2num(vk.to_bytes()))
|
|
|
|
|
|
def _compute_keygrip(params):
|
|
parts = []
|
|
for name, value in params:
|
|
exp = '{}:{}{}:'.format(len(name), name, len(value))
|
|
parts.append(b'(' + exp.encode('ascii') + value + b')')
|
|
|
|
return hashlib.sha1(b''.join(parts)).digest()
|
|
|
|
|
|
def keygrip_nist256(vk):
|
|
"""Compute keygrip for NIST256 curve public keys."""
|
|
curve = vk.curve.curve
|
|
gen = vk.curve.generator
|
|
g = (4 << 512) | (gen.x() << 256) | gen.y()
|
|
point = vk.pubkey.point
|
|
q = (4 << 512) | (point.x() << 256) | point.y()
|
|
|
|
return _compute_keygrip([
|
|
['p', util.num2bytes(curve.p(), size=32)],
|
|
['a', util.num2bytes(curve.a() % curve.p(), size=32)],
|
|
['b', util.num2bytes(curve.b() % curve.p(), size=32)],
|
|
['g', util.num2bytes(g, size=65)],
|
|
['n', util.num2bytes(vk.curve.order, size=32)],
|
|
['q', util.num2bytes(q, size=65)],
|
|
])
|
|
|
|
|
|
def keygrip_ed25519(vk):
|
|
"""Compute keygrip for Ed25519 public keys."""
|
|
# pylint: disable=line-too-long
|
|
return _compute_keygrip([
|
|
['p', util.num2bytes(0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFED, size=32)], # nopep8
|
|
['a', b'\x01'],
|
|
['b', util.num2bytes(0x2DFC9311D490018C7338BF8688861767FF8FF5B2BEBE27548A14B235ECA6874A, size=32)], # nopep8
|
|
['g', util.num2bytes(0x04216936D3CD6E53FEC0A4E231FDD6DC5C692CC7609525A7B2C9562D608F25D51A6666666666666666666666666666666666666666666666666666666666666658, size=65)], # nopep8
|
|
['n', util.num2bytes(0x1000000000000000000000000000000014DEF9DEA2F79CD65812631A5CF5D3ED, size=32)], # nopep8
|
|
['q', vk.to_bytes()],
|
|
])
|
|
|
|
|
|
def keygrip_curve25519(vk):
|
|
"""Compute keygrip for Curve25519 public keys."""
|
|
# pylint: disable=line-too-long
|
|
return _compute_keygrip([
|
|
['p', util.num2bytes(0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFED, size=32)], # nopep8
|
|
['a', b'\x01\xDB\x41'],
|
|
['b', b'\x01'],
|
|
['g', util.num2bytes(0x04000000000000000000000000000000000000000000000000000000000000000920ae19a1b8a086b4e01edd2c7748d14c923d4d7e6d7c61b229e9c5a27eced3d9, size=65)], # nopep8
|
|
['n', util.num2bytes(0x1000000000000000000000000000000014DEF9DEA2F79CD65812631A5CF5D3ED, size=32)], # nopep8
|
|
['q', vk.to_bytes()],
|
|
])
|
|
|
|
|
|
SUPPORTED_CURVES = {
|
|
formats.CURVE_NIST256: {
|
|
# https://tools.ietf.org/html/rfc6637#section-11
|
|
'oid': b'\x2A\x86\x48\xCE\x3D\x03\x01\x07',
|
|
'algo_id': 19,
|
|
'serialize': _serialize_nist256,
|
|
'keygrip': keygrip_nist256,
|
|
},
|
|
formats.CURVE_ED25519: {
|
|
'oid': b'\x2B\x06\x01\x04\x01\xDA\x47\x0F\x01',
|
|
'algo_id': 22,
|
|
'serialize': _serialize_ed25519,
|
|
'keygrip': keygrip_ed25519,
|
|
},
|
|
formats.ECDH_CURVE25519: {
|
|
'oid': b'\x2B\x06\x01\x04\x01\x97\x55\x01\x05\x01',
|
|
'algo_id': 18,
|
|
'serialize': _serialize_ed25519,
|
|
'keygrip': keygrip_curve25519,
|
|
},
|
|
}
|
|
|
|
ECDH_ALGO_ID = 18
|
|
|
|
CUSTOM_KEY_LABEL = b'TREZOR-GPG' # marks "our" pubkey
|
|
CUSTOM_SUBPACKET_ID = 26 # use "policy URL" subpacket
|
|
CUSTOM_SUBPACKET = subpacket(CUSTOM_SUBPACKET_ID, CUSTOM_KEY_LABEL)
|
|
|
|
|
|
def get_curve_name_by_oid(oid):
|
|
"""Return curve name matching specified OID, or raise KeyError."""
|
|
for curve_name, info in SUPPORTED_CURVES.items():
|
|
if info['oid'] == oid:
|
|
return curve_name
|
|
raise KeyError('Unknown OID: {!r}'.format(oid))
|
|
|
|
|
|
class PublicKey:
|
|
"""GPG representation for public key packets."""
|
|
|
|
def __init__(self, curve_name, created, verifying_key, ecdh=False):
|
|
"""Contruct using a ECDSA VerifyingKey object."""
|
|
self.curve_name = curve_name
|
|
self.curve_info = SUPPORTED_CURVES[curve_name]
|
|
self.created = int(created) # time since Epoch
|
|
self.verifying_key = verifying_key
|
|
self.ecdh = bool(ecdh)
|
|
if ecdh:
|
|
self.algo_id = ECDH_ALGO_ID
|
|
self.ecdh_packet = b'\x03\x01\x08\x07'
|
|
else:
|
|
self.algo_id = self.curve_info['algo_id']
|
|
self.ecdh_packet = b''
|
|
|
|
def keygrip(self):
|
|
"""Compute GPG keygrip of the verifying key."""
|
|
return self.curve_info['keygrip'](self.verifying_key)
|
|
|
|
def data(self):
|
|
"""Data for packet creation."""
|
|
header = struct.pack('>BLB',
|
|
4, # version
|
|
self.created, # creation
|
|
self.algo_id) # public key algorithm ID
|
|
oid = util.prefix_len('>B', self.curve_info['oid'])
|
|
blob = self.curve_info['serialize'](self.verifying_key)
|
|
return header + oid + blob + self.ecdh_packet
|
|
|
|
def data_to_hash(self):
|
|
"""Data for digest computation."""
|
|
return b'\x99' + util.prefix_len('>H', self.data())
|
|
|
|
def _fingerprint(self):
|
|
return hashlib.sha1(self.data_to_hash()).digest()
|
|
|
|
def key_id(self):
|
|
"""Short (8 byte) GPG key ID."""
|
|
return self._fingerprint()[-8:]
|
|
|
|
def __repr__(self):
|
|
"""Short (8 hexadecimal digits) GPG key ID."""
|
|
hex_key_id = util.hexlify(self.key_id())[-8:]
|
|
return 'GPG public key {}/{}'.format(self.curve_name, hex_key_id)
|
|
|
|
__str__ = __repr__
|
|
|
|
|
|
def _split_lines(body, size):
|
|
lines = []
|
|
for i in range(0, len(body), size):
|
|
lines.append(body[i:i+size] + '\n')
|
|
return ''.join(lines)
|
|
|
|
|
|
def armor(blob, type_str):
|
|
"""See https://tools.ietf.org/html/rfc4880#section-6 for details."""
|
|
head = '-----BEGIN PGP {}-----\nVersion: GnuPG v2\n\n'.format(type_str)
|
|
body = base64.b64encode(blob).decode('ascii')
|
|
checksum = base64.b64encode(util.crc24(blob)).decode('ascii')
|
|
tail = '-----END PGP {}-----\n'.format(type_str)
|
|
return head + _split_lines(body, 64) + '=' + checksum + '\n' + tail
|
|
|
|
|
|
def make_signature(signer_func, data_to_sign, public_algo,
|
|
hashed_subpackets, unhashed_subpackets, sig_type=0):
|
|
"""Create new GPG signature."""
|
|
# pylint: disable=too-many-arguments
|
|
header = struct.pack('>BBBB',
|
|
4, # version
|
|
sig_type, # rfc4880 (section-5.2.1)
|
|
public_algo,
|
|
8) # hash_alg (SHA256)
|
|
hashed = subpackets(*hashed_subpackets)
|
|
unhashed = subpackets(*unhashed_subpackets)
|
|
tail = b'\x04\xff' + struct.pack('>L', len(header) + len(hashed))
|
|
data_to_hash = data_to_sign + header + hashed + tail
|
|
|
|
log.debug('hashing %d bytes', len(data_to_hash))
|
|
digest = hashlib.sha256(data_to_hash).digest()
|
|
log.debug('signing digest: %s', util.hexlify(digest))
|
|
params = signer_func(digest=digest)
|
|
sig = b''.join(mpi(p) for p in params)
|
|
|
|
return bytes(header + hashed + unhashed +
|
|
digest[:2] + # used for decoder's sanity check
|
|
sig) # actual ECDSA signature
|