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New module utils openssh.certificate (#246)
* Initial commit * Adding informational comments * Adding changelog fragment * Fixing CRLF changelog fragment * Refactoring public number parsing and added chaining for writer methods * Adding more descriptive error for invalid certificate data * Fixing signature data parsing * Correcting ed25519 signature type to binary * Applying initial review suggestions and fixing option-list writer * Applying review suggestions * Making OpensshWriter private
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Ajpantuso
GitHub
337
plugins/module_utils/openssh/certificate.py
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337
plugins/module_utils/openssh/certificate.py
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# -*- coding: utf-8 -*-
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#
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# Copyright: (c) 2021, Andrew Pantuso (@ajpantuso) <ajpantuso@gmail.com>
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#
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# Ansible is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# Ansible is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Ansible. If not, see <http://www.gnu.org/licenses/>.
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from __future__ import absolute_import, division, print_function
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__metaclass__ = type
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# Protocol References
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# -------------------
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# https://datatracker.ietf.org/doc/html/rfc4251
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# https://datatracker.ietf.org/doc/html/rfc4253
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# https://datatracker.ietf.org/doc/html/rfc5656
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# https://datatracker.ietf.org/doc/html/rfc8032
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# https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.certkeys?annotate=HEAD
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#
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# Inspired by:
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# ------------
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# https://github.com/pyca/cryptography/blob/main/src/cryptography/hazmat/primitives/serialization/ssh.py
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# https://github.com/paramiko/paramiko/blob/master/paramiko/message.py
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import abc
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import binascii
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import os
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from base64 import b64encode
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from hashlib import sha256
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from ansible.module_utils import six
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from ansible_collections.community.crypto.plugins.module_utils.openssh.utils import (
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OpensshParser,
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_OpensshWriter,
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)
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# See https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.certkeys?annotate=HEAD
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_USER_TYPE = 1
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_HOST_TYPE = 2
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_SSH_TYPE_STRINGS = {
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'rsa': b"ssh-rsa",
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'dsa': b"ssh-dss",
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'ecdsa-nistp256': b"ecdsa-sha2-nistp256",
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'ecdsa-nistp384': b"ecdsa-sha2-nistp384",
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'ecdsa-nistp521': b"ecdsa-sha2-nistp521",
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'ed25519': b"ssh-ed25519",
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}
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_CERT_SUFFIX_V01 = b"-cert-v01@openssh.com"
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# See https://datatracker.ietf.org/doc/html/rfc5656#section-6.1
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_ECDSA_CURVE_IDENTIFIERS = {
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'ecdsa-nistp256': b'nistp256',
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'ecdsa-nistp384': b'nistp384',
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'ecdsa-nistp521': b'nistp521',
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}
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_ECDSA_CURVE_IDENTIFIERS_LOOKUP = {
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b'nistp256': 'ecdsa-nistp256',
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b'nistp384': 'ecdsa-nistp384',
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b'nistp521': 'ecdsa-nistp521',
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}
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@six.add_metaclass(abc.ABCMeta)
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class OpensshCertificateInfo:
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"""Encapsulates all certificate information which is signed by a CA key"""
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def __init__(self,
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nonce=None,
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serial=None,
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cert_type=None,
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key_id=None,
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principals=None,
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valid_after=None,
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valid_before=None,
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critical_options=None,
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extensions=None,
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reserved=None):
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self.nonce = nonce
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self.serial = serial
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self._cert_type = cert_type
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self.key_id = key_id
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self.principals = principals
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self.valid_after = valid_after
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self.valid_before = valid_before
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self.critical_options = critical_options
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self.extensions = extensions
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self.reserved = reserved
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self.type_string = None
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@property
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def cert_type(self):
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if self._cert_type == _USER_TYPE:
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return 'user'
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elif self._cert_type == _HOST_TYPE:
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return 'host'
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else:
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return ''
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@cert_type.setter
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def cert_type(self, cert_type):
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if cert_type == 'user' or cert_type == _USER_TYPE:
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self._cert_type = _USER_TYPE
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elif cert_type == 'host' or cert_type == _HOST_TYPE:
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self._cert_type = _HOST_TYPE
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else:
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raise ValueError("%s is not a valid certificate type" % cert_type)
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@abc.abstractmethod
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def public_key_fingerprint(self):
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pass
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@abc.abstractmethod
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def parse_public_numbers(self, parser):
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pass
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class OpensshRSACertificateInfo(OpensshCertificateInfo):
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def __init__(self, e=None, n=None, **kwargs):
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super(OpensshRSACertificateInfo, self).__init__(**kwargs)
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self.type_string = _SSH_TYPE_STRINGS['rsa'] + _CERT_SUFFIX_V01
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self.e = e
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self.n = n
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# See https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
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def public_key_fingerprint(self):
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if any([self.e is None, self.n is None]):
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return b''
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writer = _OpensshWriter()
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writer.string(_SSH_TYPE_STRINGS['rsa'])
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writer.mpint(self.e)
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writer.mpint(self.n)
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return fingerprint(writer.bytes())
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def parse_public_numbers(self, parser):
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self.e = parser.mpint()
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self.n = parser.mpint()
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class OpensshDSACertificateInfo(OpensshCertificateInfo):
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def __init__(self, p=None, q=None, g=None, y=None, **kwargs):
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super(OpensshDSACertificateInfo, self).__init__(**kwargs)
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self.type_string = _SSH_TYPE_STRINGS['dsa'] + _CERT_SUFFIX_V01
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self.p = p
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self.q = q
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self.g = g
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self.y = y
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# See https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
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def public_key_fingerprint(self):
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if any([self.p is None, self.q is None, self.g is None, self.y is None]):
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return b''
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writer = _OpensshWriter()
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writer.string(_SSH_TYPE_STRINGS['dsa'])
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writer.mpint(self.p)
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writer.mpint(self.q)
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writer.mpint(self.g)
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writer.mpint(self.y)
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return fingerprint(writer.bytes())
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def parse_public_numbers(self, parser):
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self.p = parser.mpint()
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self.q = parser.mpint()
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self.g = parser.mpint()
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self.y = parser.mpint()
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class OpensshECDSACertificateInfo(OpensshCertificateInfo):
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def __init__(self, curve=None, public_key=None, **kwargs):
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super(OpensshECDSACertificateInfo, self).__init__(**kwargs)
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self._curve = None
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if curve is not None:
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self.curve = curve
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self.public_key = public_key
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@property
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def curve(self):
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return self._curve
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@curve.setter
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def curve(self, curve):
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if curve in _ECDSA_CURVE_IDENTIFIERS.values():
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self._curve = curve
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self.type_string = _SSH_TYPE_STRINGS[_ECDSA_CURVE_IDENTIFIERS_LOOKUP[curve]] + _CERT_SUFFIX_V01
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else:
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raise ValueError(
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"Curve must be one of %s" % (b','.join(list(_ECDSA_CURVE_IDENTIFIERS.values()))).decode('UTF-8')
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)
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# See https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
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def public_key_fingerprint(self):
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if any([self.curve is None, self.public_key is None]):
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return b''
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writer = _OpensshWriter()
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writer.string(_SSH_TYPE_STRINGS[_ECDSA_CURVE_IDENTIFIERS_LOOKUP[self.curve]])
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writer.string(self.curve)
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writer.string(self.public_key)
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return fingerprint(writer.bytes())
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def parse_public_numbers(self, parser):
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self.curve = parser.string()
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self.public_key = parser.string()
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class OpensshED25519CertificateInfo(OpensshCertificateInfo):
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def __init__(self, pk=None, **kwargs):
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super(OpensshED25519CertificateInfo, self).__init__(**kwargs)
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self.type_string = _SSH_TYPE_STRINGS['ed25519'] + _CERT_SUFFIX_V01
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self.pk = pk
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def public_key_fingerprint(self):
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if self.pk is None:
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return b''
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writer = _OpensshWriter()
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writer.string(_SSH_TYPE_STRINGS['ed25519'])
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writer.string(self.pk)
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return fingerprint(writer.bytes())
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def parse_public_numbers(self, parser):
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self.pk = parser.string()
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# See https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.certkeys?annotate=HEAD
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class OpensshCertificate(object):
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"""Encapsulates a formatted OpenSSH certificate including signature and signing key"""
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def __init__(self, cert_info, signing_key, signature):
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self.cert_info = cert_info
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self.signing_key = signing_key
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self.signature = signature
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@classmethod
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def load(cls, path):
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if not os.path.exists(path):
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raise ValueError("%s is not a valid path." % path)
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try:
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with open(path, 'rb') as cert_file:
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data = cert_file.read()
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except (IOError, OSError) as e:
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raise ValueError("%s cannot be opened for reading: %s" % (path, e))
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try:
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format_identifier, b64_cert = data.split(b' ')[:2]
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cert = binascii.a2b_base64(b64_cert)
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except (binascii.Error, ValueError):
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raise ValueError("Certificate not in OpenSSH format")
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for key_type, string in _SSH_TYPE_STRINGS.items():
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if format_identifier == string + _CERT_SUFFIX_V01:
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pub_key_type = key_type
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break
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else:
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raise ValueError("Invalid certificate format identifier: %s" % format_identifier)
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parser = OpensshParser(cert)
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if format_identifier != parser.string():
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raise ValueError("Certificate formats do not match")
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try:
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cert_info = cls._parse_cert_info(pub_key_type, parser)
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signing_key = parser.string()
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signature = parser.string()
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except (TypeError, ValueError) as e:
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raise ValueError("Invalid certificate data: %s" % e)
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if parser.remaining_bytes():
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raise ValueError(
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"%s bytes of additional data was not parsed while loading %s" % (parser.remaining_bytes(), path)
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)
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return cls(
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cert_info=cert_info,
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signing_key=signing_key,
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signature=signature,
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)
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def signing_key_fingerprint(self):
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return fingerprint(self.signing_key)
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@staticmethod
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def _parse_cert_info(pub_key_type, parser):
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cert_info = get_cert_info_object(pub_key_type)
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cert_info.nonce = parser.string()
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cert_info.parse_public_numbers(parser)
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cert_info.serial = parser.uint64()
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cert_info.cert_type = parser.uint32()
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cert_info.key_id = parser.string()
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cert_info.principals = parser.string_list()
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cert_info.valid_after = parser.uint64()
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cert_info.valid_before = parser.uint64()
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cert_info.critical_options = parser.option_list()
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cert_info.extensions = parser.option_list()
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cert_info.reserved = parser.string()
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return cert_info
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def fingerprint(public_key):
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"""Generates a SHA256 hash and formats output to resemble ``ssh-keygen``"""
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h = sha256()
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h.update(public_key)
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return b'SHA256:' + b64encode(h.digest()).rstrip(b'=')
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def get_cert_info_object(key_type):
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if key_type == 'rsa':
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cert_info = OpensshRSACertificateInfo()
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elif key_type == 'dsa':
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cert_info = OpensshDSACertificateInfo()
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elif key_type in ('ecdsa-nistp256', 'ecdsa-nistp384', 'ecdsa-nistp521'):
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cert_info = OpensshECDSACertificateInfo()
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elif key_type == 'ed25519':
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cert_info = OpensshED25519CertificateInfo()
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else:
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raise ValueError("%s is not a valid key type" % key_type)
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return cert_info
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