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gpg: initial support for ElGamal and DSA

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Doesn't verify anything (yet).
This commit is contained in:
Roman Zeyde
2016-05-18 23:07:57 +03:00
parent bf8f516ef4
commit 3192e570ed
2 changed files with 31 additions and 9 deletions
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6
trezor_agent/gpg/agent.py
View File

@@ -83,6 +83,8 @@ def _parse_ecdsa_sig(args):
return (util.bytes2num(sig_r),
util.bytes2num(sig_s))
_parse_dsa_sig = _parse_ecdsa_sig
def _parse_rsa_sig(args):
(s, sig_s), = args
@@ -94,7 +96,9 @@ def _parse_sig(sig):
label, sig = sig
assert label == 'sig-val'
algo_name = sig[0]
parser = {'rsa': _parse_rsa_sig, 'ecdsa': _parse_ecdsa_sig}[algo_name]
parser = {'rsa': _parse_rsa_sig,
'ecdsa': _parse_ecdsa_sig,
'dsa': _parse_dsa_sig}[algo_name]
return parser(args=sig[1:])

34
trezor_agent/gpg/decode.py
View File

@@ -41,6 +41,11 @@ def parse_mpi(s):
return sum(v << (8 * i) for i, v in enumerate(reversed(blob)))
def parse_mpis(s, n):
"""Parse multiple MPIs from stream."""
return [parse_mpi(s) for _ in range(n)]
def _parse_nist256p1_verifier(mpi):
prefix, x, y = util.split_bits(mpi, 4, 256, 256)
assert prefix == 4
@@ -90,6 +95,9 @@ SUPPORTED_CURVES = {
b'\x2B\x06\x01\x04\x01\xDA\x47\x0F\x01': _parse_ed25519_verifier,
}
RSA_ALGO_IDS = {1, 2, 3}
ELGAMAL_ALGO_ID = 16
DSA_ALGO_ID = 17
ECDSA_ALGO_IDS = {18, 19, 22} # {ecdsa, nist256, ed25519}
@@ -142,8 +150,12 @@ def _parse_signature(stream):
p['hash_prefix'] = stream.readfmt('2s')
if p['pubkey_alg'] in ECDSA_ALGO_IDS:
p['sig'] = (parse_mpi(stream), parse_mpi(stream))
else: # RSA
elif p['pubkey_alg'] in RSA_ALGO_IDS: # RSA
p['sig'] = (parse_mpi(stream),)
elif p['pubkey_alg'] == DSA_ALGO_ID:
p['sig'] = (parse_mpi(stream), parse_mpi(stream))
else:
log.error('unsupported public key algo: %d', p['pubkey_alg'])
assert not stream.read()
return p
@@ -176,12 +188,15 @@ def _parse_pubkey(stream, packet_type='pubkey'):
size, = util.readfmt(leftover, 'B')
p['kdf'] = leftover.read(size)
assert not leftover.read()
else: # RSA
elif p['algo'] == DSA_ALGO_ID:
log.warning('DSA signatures are not verified')
parse_mpis(stream, n=4)
elif p['algo'] == ELGAMAL_ALGO_ID:
log.warning('ElGamal signatures are not verified')
parse_mpis(stream, n=3)
else: # assume RSA
log.debug('parsing RSA key')
n = parse_mpi(stream)
e = parse_mpi(stream)
log.debug('n: %x (%d bits)', n, n.bit_length())
log.debug('e: %x (%d bits)', e, e.bit_length())
n, e = parse_mpis(stream, n=2)
p['verifier'] = _create_rsa_verifier(n, e)
assert not stream.read()
@@ -266,8 +281,11 @@ def load_public_key(stream, use_custom=False):
digest = digest_packets([pubkey, userid, signature])
assert signature['hash_prefix'] == digest[:2]
log.debug('loaded public key "%s"', userid['value'])
verify_digest(pubkey=pubkey, digest=digest,
signature=signature['sig'], label='GPG public key')
if pubkey.get('verifier'):
verify_digest(pubkey=pubkey, digest=digest,
signature=signature['sig'], label='GPG public key')
else:
log.warning('public key %s cannot be verified!', util.hexlify(pubkey['key_id']))
packet = pubkey
while use_custom: