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[WIP] Add support for adding subkeys to NISTP-521 GPG identities #172

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[WIP] Add support for adding subkeys to NISTP-521 GPG identities #172

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13 changes: 13 additions & 0 deletions libagent/gpg/decode.py
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,17 @@ def _parse_nist256p1_pubkey(mpi):
hashfunc=hashlib.sha256)


def _parse_nist521p1_pubkey(mpi):
prefix, x, y = util.split_bits(mpi, 4, 528, 528)
if prefix != 4:
raise ValueError('Invalid MPI prefix: {}'.format(prefix))
point = ecdsa.ellipticcurve.Point(curve=ecdsa.NIST521p.curve,
x=x, y=y)
return ecdsa.VerifyingKey.from_public_point(
point=point, curve=ecdsa.curves.NIST521p,
hashfunc=hashlib.sha512)


def _parse_ed25519_pubkey(mpi):
prefix, value = util.split_bits(mpi, 8, 256)
if prefix != 0x40:
Expand All @@ -73,6 +84,8 @@ def _parse_ed25519_pubkey(mpi):
SUPPORTED_CURVES = {
b'\x2A\x86\x48\xCE\x3D\x03\x01\x07':
(_parse_nist256p1_pubkey, protocol.keygrip_nist256),
b'\x2B\x81\x04\x00\x23':
(_parse_nist521p1_pubkey, protocol.keygrip_nist521),
b'\x2B\x06\x01\x04\x01\xDA\x47\x0F\x01':
(_parse_ed25519_pubkey, protocol.keygrip_ed25519),
b'\x2B\x06\x01\x04\x01\x97\x55\x01\x05\x01':
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18 changes: 18 additions & 0 deletions libagent/gpg/protocol.py
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ def _compute_keygrip(params):
exp = '{}:{}{}:'.format(len(name), name, len(value))
parts.append(b'(' + exp.encode('ascii') + value + b')')

log.debug('keygrip parts: %s', parts)
return hashlib.sha1(b''.join(parts)).digest()


Expand All @@ -122,6 +123,23 @@ def keygrip_nist256(vk):
])


def keygrip_nist521(vk):
"""Compute keygrip for NIST521 curve public keys."""
curve = vk.curve.curve
gen = vk.curve.generator
g = (4 << 1200) | (gen.x() << 600) | gen.y()
point = vk.pubkey.point
q = (4 << 1200) | (point.x() << 600) | point.y()
return _compute_keygrip([
['p', util.num2bytes(curve.p(), size=66)],
['a', util.num2bytes(curve.a() % curve.p(), size=66)],
['b', util.num2bytes(curve.b() % curve.p(), size=66)],
['g', util.num2bytes(g, size=160)],
['n', util.num2bytes(vk.curve.order, size=66)],
['q', util.num2bytes(q, size=160)],
])


def keygrip_ed25519(vk):
"""Compute keygrip for Ed25519 public keys."""
# pylint: disable=line-too-long
Expand Down