Split the package into a shared library and separate per-device packages

2026-03-23 19:01:00 +08:00 · 2017-04-27 16:31:17 +03:00
parent eb525e1b62
commit 4af881b3cb
54 changed files with 229 additions and 157 deletions
--- a/libagent/gpg/protocol.py
+++ b/libagent/gpg/protocol.py
@@ -0,0 +1,271 @@
+"""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_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(object):
+    """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