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137 lines
4.2 KiB
Python
137 lines
4.2 KiB
Python
"""GPG-agent utilities."""
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import binascii
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import contextlib
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import logging
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import os
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from . import decode, encode, keyring
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from .. import util
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log = logging.getLogger(__name__)
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def yield_connections(sock):
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"""Run a server on the specified socket."""
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while True:
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log.debug('waiting for connection on %s', sock.getsockname())
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try:
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conn, _ = sock.accept()
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except KeyboardInterrupt:
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return
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conn.settimeout(None)
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log.debug('accepted connection on %s', sock.getsockname())
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yield conn
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def serialize(data):
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"""Serialize data according to ASSUAN protocol."""
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for c in ['%', '\n', '\r']:
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data = data.replace(c, '%{:02X}'.format(ord(c)))
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return data
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def sig_encode(r, s):
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"""Serialize ECDSA signature data into GPG S-expression."""
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r = serialize(util.num2bytes(r, 32))
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s = serialize(util.num2bytes(s, 32))
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return '(7:sig-val(5:ecdsa(1:r32:{})(1:s32:{})))'.format(r, s)
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def pksign(keygrip, digest, algo):
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"""Sign a message digest using a private EC key."""
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assert algo == '8'
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user_id = os.environ['TREZOR_GPG_USER_ID']
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pubkey_dict = decode.load_public_key(
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pubkey_bytes=keyring.export_public_key(user_id=user_id),
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use_custom=True, ecdh=False)
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pubkey, conn = encode.load_from_public_key(pubkey_dict=pubkey_dict)
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with contextlib.closing(conn):
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assert pubkey.keygrip == binascii.unhexlify(keygrip)
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r, s = conn.sign(binascii.unhexlify(digest))
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result = sig_encode(r, s)
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log.debug('result: %r', result)
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return result
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def _serialize_point(data):
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data = '{}:'.format(len(data)) + data
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# https://www.gnupg.org/documentation/manuals/assuan/Server-responses.html
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for c in ['%', '\n', '\r']:
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data = data.replace(c, '%{:02X}'.format(ord(c)))
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return '(5:value' + data + ')'
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def parse_ecdh(line):
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"""Parse ECDH request and return remote public key."""
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prefix, line = line.split(' ', 1)
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assert prefix == 'D'
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exp, leftover = keyring.parse(keyring.unescape(line))
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log.debug('ECDH s-exp: %r', exp)
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assert not leftover
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label, exp = exp
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assert label == b'enc-val'
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assert exp[0] == b'ecdh'
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items = exp[1:]
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log.debug('ECDH parameters: %r', items)
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return dict(items)['e']
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def pkdecrypt(keygrip, conn):
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"""Handle decryption using ECDH."""
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for msg in [b'S INQUIRE_MAXLEN 4096', b'INQUIRE CIPHERTEXT']:
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keyring.sendline(conn, msg)
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line = keyring.recvline(conn)
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assert keyring.recvline(conn) == b'END'
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remote_pubkey = parse_ecdh(line)
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user_id = os.environ['TREZOR_GPG_USER_ID']
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local_pubkey = decode.load_public_key(
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pubkey_bytes=keyring.export_public_key(user_id=user_id),
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use_custom=True, ecdh=True)
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pubkey, conn = encode.load_from_public_key(pubkey_dict=local_pubkey)
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with contextlib.closing(conn):
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assert pubkey.keygrip == binascii.unhexlify(keygrip)
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shared_secret = conn.ecdh(remote_pubkey)
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assert len(shared_secret) == 65
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assert shared_secret[:1] == b'\x04'
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return _serialize_point(shared_secret)
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def handle_connection(conn):
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"""Handle connection from GPG binary using the ASSUAN protocol."""
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keygrip = None
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digest = None
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algo = None
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version = keyring.gpg_version()
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keyring.sendline(conn, b'OK')
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for line in keyring.iterlines(conn):
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parts = line.split(' ')
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command = parts[0]
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args = parts[1:]
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if command in {'RESET', 'OPTION', 'HAVEKEY', 'SETKEYDESC'}:
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pass # reply with OK
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elif command == 'GETINFO':
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keyring.sendline(conn, b'D ' + version)
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elif command == 'AGENT_ID':
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keyring.sendline(conn, b'D TREZOR')
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elif command in {'SIGKEY', 'SETKEY'}:
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keygrip, = args
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elif command == 'SETHASH':
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algo, digest = args
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elif command == 'PKSIGN':
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sig = pksign(keygrip, digest, algo)
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keyring.sendline(conn, b'D ' + sig)
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elif command == 'PKDECRYPT':
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sec = pkdecrypt(keygrip, conn)
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keyring.sendline(conn, b'D ' + sec)
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elif command == 'BYE':
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return
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else:
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log.error('unknown request: %r', line)
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return
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keyring.sendline(conn, b'OK')
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