From 949892938735c0cf14a6689d68779c2ce2410585 Mon Sep 17 00:00:00 2001 From: Alex Gaynor Date: Fri, 3 Jun 2016 13:04:26 -0700 Subject: SSH serialization for public keys (#2957) * SSH serialization for public keys * name errors ahoy! * id, ego, superego * dsa support * EC support * Don't keyerror * Documentation OpenSSH * flake8 * fix * bytes bytes bytes * skip curve unsupported * bytes! * Move a function * reorganize code for coverage --- .../hazmat/backends/openssl/backend.py | 55 +++++++++++++++++++++- src/cryptography/hazmat/backends/openssl/dsa.py | 1 + src/cryptography/hazmat/backends/openssl/ec.py | 1 + src/cryptography/hazmat/backends/openssl/rsa.py | 1 + .../hazmat/primitives/serialization.py | 37 ++++++++++----- 5 files changed, 81 insertions(+), 14 deletions(-) (limited to 'src') diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py index d8a681e6..126a881a 100644 --- a/src/cryptography/hazmat/backends/openssl/backend.py +++ b/src/cryptography/hazmat/backends/openssl/backend.py @@ -4,6 +4,7 @@ from __future__ import absolute_import, division, print_function +import base64 import calendar import collections import itertools @@ -1698,11 +1699,23 @@ class Backend(object): self.openssl_assert(res == 1) return self._read_mem_bio(bio) - def _public_key_bytes(self, encoding, format, evp_pkey, cdata): + def _public_key_bytes(self, encoding, format, key, evp_pkey, cdata): if not isinstance(encoding, serialization.Encoding): raise TypeError("encoding must be an item from the Encoding enum") - if format is serialization.PublicFormat.SubjectPublicKeyInfo: + if ( + format is serialization.PublicFormat.OpenSSH or + encoding is serialization.Encoding.OpenSSH + ): + if ( + format is not serialization.PublicFormat.OpenSSH or + encoding is not serialization.Encoding.OpenSSH + ): + raise ValueError( + "OpenSSH format must be used with OpenSSH encoding" + ) + return self._openssh_public_key_bytes(key) + elif format is serialization.PublicFormat.SubjectPublicKeyInfo: if encoding is serialization.Encoding.PEM: write_bio = self._lib.PEM_write_bio_PUBKEY else: @@ -1732,6 +1745,44 @@ class Backend(object): self.openssl_assert(res == 1) return self._read_mem_bio(bio) + def _openssh_public_key_bytes(self, key): + if isinstance(key, rsa.RSAPublicKey): + public_numbers = key.public_numbers() + return b"ssh-rsa " + base64.b64encode( + serialization._ssh_write_string(b"ssh-rsa") + + serialization._ssh_write_mpint(public_numbers.e) + + serialization._ssh_write_mpint(public_numbers.n) + ) + elif isinstance(key, dsa.DSAPublicKey): + public_numbers = key.public_numbers() + parameter_numbers = public_numbers.parameter_numbers + return b"ssh-dss " + base64.b64encode( + serialization._ssh_write_string(b"ssh-dss") + + serialization._ssh_write_mpint(parameter_numbers.p) + + serialization._ssh_write_mpint(parameter_numbers.q) + + serialization._ssh_write_mpint(parameter_numbers.g) + + serialization._ssh_write_mpint(public_numbers.y) + ) + else: + assert isinstance(key, ec.EllipticCurvePublicKey) + public_numbers = key.public_numbers() + try: + curve_name = { + ec.SECP256R1: b"nistp256", + ec.SECP384R1: b"nistp384", + ec.SECP521R1: b"nistp521", + }[type(public_numbers.curve)] + except KeyError: + raise ValueError( + "Only SECP256R1, SECP384R1, and SECP521R1 curves are " + "supported by the SSH public key format" + ) + return b"ecdsa-sha2-" + curve_name + b" " + base64.b64encode( + serialization._ssh_write_string(b"ecdsa-sha2-" + curve_name) + + serialization._ssh_write_string(curve_name) + + serialization._ssh_write_string(public_numbers.encode_point()) + ) + class GetCipherByName(object): def __init__(self, fmt): diff --git a/src/cryptography/hazmat/backends/openssl/dsa.py b/src/cryptography/hazmat/backends/openssl/dsa.py index 5abc3da9..1608df04 100644 --- a/src/cryptography/hazmat/backends/openssl/dsa.py +++ b/src/cryptography/hazmat/backends/openssl/dsa.py @@ -297,6 +297,7 @@ class _DSAPublicKey(object): return self._backend._public_key_bytes( encoding, format, + self, self._evp_pkey, None ) diff --git a/src/cryptography/hazmat/backends/openssl/ec.py b/src/cryptography/hazmat/backends/openssl/ec.py index aa4a7a35..2f476031 100644 --- a/src/cryptography/hazmat/backends/openssl/ec.py +++ b/src/cryptography/hazmat/backends/openssl/ec.py @@ -299,6 +299,7 @@ class _EllipticCurvePublicKey(object): return self._backend._public_key_bytes( encoding, format, + self, self._evp_pkey, None ) diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py index d8458ccc..920bae06 100644 --- a/src/cryptography/hazmat/backends/openssl/rsa.py +++ b/src/cryptography/hazmat/backends/openssl/rsa.py @@ -642,6 +642,7 @@ class _RSAPublicKey(object): return self._backend._public_key_bytes( encoding, format, + self, self._evp_pkey, self._rsa_cdata ) diff --git a/src/cryptography/hazmat/primitives/serialization.py b/src/cryptography/hazmat/primitives/serialization.py index d848e5d4..992fd42f 100644 --- a/src/cryptography/hazmat/primitives/serialization.py +++ b/src/cryptography/hazmat/primitives/serialization.py @@ -59,7 +59,7 @@ def load_ssh_public_key(data, backend): except TypeError: raise ValueError('Key is not in the proper format.') - inner_key_type, rest = _read_next_string(decoded_data) + inner_key_type, rest = _ssh_read_next_string(decoded_data) if inner_key_type != key_type: raise ValueError( @@ -70,8 +70,8 @@ def load_ssh_public_key(data, backend): def _load_ssh_rsa_public_key(key_type, decoded_data, backend): - e, rest = _read_next_mpint(decoded_data) - n, rest = _read_next_mpint(rest) + e, rest = _ssh_read_next_mpint(decoded_data) + n, rest = _ssh_read_next_mpint(rest) if rest: raise ValueError('Key body contains extra bytes.') @@ -80,10 +80,10 @@ def _load_ssh_rsa_public_key(key_type, decoded_data, backend): def _load_ssh_dss_public_key(key_type, decoded_data, backend): - p, rest = _read_next_mpint(decoded_data) - q, rest = _read_next_mpint(rest) - g, rest = _read_next_mpint(rest) - y, rest = _read_next_mpint(rest) + p, rest = _ssh_read_next_mpint(decoded_data) + q, rest = _ssh_read_next_mpint(rest) + g, rest = _ssh_read_next_mpint(rest) + y, rest = _ssh_read_next_mpint(rest) if rest: raise ValueError('Key body contains extra bytes.') @@ -95,8 +95,8 @@ def _load_ssh_dss_public_key(key_type, decoded_data, backend): def _load_ssh_ecdsa_public_key(expected_key_type, decoded_data, backend): - curve_name, rest = _read_next_string(decoded_data) - data, rest = _read_next_string(rest) + curve_name, rest = _ssh_read_next_string(decoded_data) + data, rest = _ssh_read_next_string(rest) if expected_key_type != b"ecdsa-sha2-" + curve_name: raise ValueError( @@ -121,7 +121,7 @@ def _load_ssh_ecdsa_public_key(expected_key_type, decoded_data, backend): return numbers.public_key(backend) -def _read_next_string(data): +def _ssh_read_next_string(data): """ Retrieves the next RFC 4251 string value from the data. @@ -137,22 +137,34 @@ def _read_next_string(data): return data[4:4 + str_len], data[4 + str_len:] -def _read_next_mpint(data): +def _ssh_read_next_mpint(data): """ Reads the next mpint from the data. Currently, all mpints are interpreted as unsigned. """ - mpint_data, rest = _read_next_string(data) + mpint_data, rest = _ssh_read_next_string(data) return ( utils.int_from_bytes(mpint_data, byteorder='big', signed=False), rest ) +def _ssh_write_string(data): + return struct.pack(">I", len(data)) + data + + +def _ssh_write_mpint(value): + data = utils.int_to_bytes(value) + if six.indexbytes(data, 0) & 0x80: + data = b"\x00" + data + return _ssh_write_string(data) + + class Encoding(Enum): PEM = "PEM" DER = "DER" + OpenSSH = "OpenSSH" class PrivateFormat(Enum): @@ -163,6 +175,7 @@ class PrivateFormat(Enum): class PublicFormat(Enum): SubjectPublicKeyInfo = "X.509 subjectPublicKeyInfo with PKCS#1" PKCS1 = "Raw PKCS#1" + OpenSSH = "OpenSSH" @six.add_metaclass(abc.ABCMeta) -- cgit v1.2.3