d5a39ad14a
More details by the code author in his blog post at http://adam.younglogic.com/2014/02/compressed-tokens/. Change-Id: I35c5eca2e04a74236bd8c7fb6daab3ea46b59b0e Closes-Bug: #1352314
419 lines
15 KiB
Python
419 lines
15 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Certificate signing functions.
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Call set_subprocess() with the subprocess module. Either Python's
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subprocess or eventlet.green.subprocess can be used.
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If set_subprocess() is not called, this module will pick Python's subprocess
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or eventlet.green.subprocess based on if os module is patched by eventlet.
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"""
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import base64
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import errno
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import hashlib
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import logging
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import textwrap
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import zlib
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import six
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from keystoneclient import exceptions
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from keystoneclient.i18n import _, _LE, _LW
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subprocess = None
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LOG = logging.getLogger(__name__)
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PKI_ASN1_PREFIX = 'MII'
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PKIZ_PREFIX = 'PKIZ_'
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PKIZ_CMS_FORM = 'DER'
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PKI_ASN1_FORM = 'PEM'
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DEFAULT_TOKEN_DIGEST_ALGORITHM = 'sha256'
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# The openssl cms command exits with these status codes.
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# See https://www.openssl.org/docs/apps/cms.html#EXIT_CODES
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class OpensslCmsExitStatus(object):
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SUCCESS = 0
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INPUT_FILE_READ_ERROR = 2
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CREATE_CMS_READ_MIME_ERROR = 3
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def _ensure_subprocess():
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# NOTE(vish): late loading subprocess so we can
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# use the green version if we are in
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# eventlet.
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global subprocess
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if not subprocess:
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try:
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from eventlet import patcher
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if patcher.already_patched:
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from eventlet.green import subprocess
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else:
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import subprocess
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except ImportError:
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import subprocess # noqa
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def set_subprocess(_subprocess=None):
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"""Set subprocess module to use.
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The subprocess could be eventlet.green.subprocess if using eventlet,
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or Python's subprocess otherwise.
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"""
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global subprocess
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subprocess = _subprocess
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def _check_files_accessible(files):
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err = None
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retcode = -1
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try:
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for try_file in files:
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with open(try_file, 'r'):
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pass
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except IOError as e:
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# Catching IOError means there is an issue with
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# the given file.
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err = _('Hit OSError in _process_communicate_handle_oserror()\n'
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'Likely due to %(file)s: %(error)s') % {'file': try_file,
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'error': e.strerror}
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# Emulate openssl behavior, which returns with code 2 when
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# access to a file failed.
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retcode = OpensslCmsExitStatus.INPUT_FILE_READ_ERROR
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return retcode, err
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def _process_communicate_handle_oserror(process, data, files):
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"""Wrapper around process.communicate that checks for OSError."""
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try:
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output, err = process.communicate(data)
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except OSError as e:
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if e.errno != errno.EPIPE:
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raise
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# OSError with EPIPE only occurs with Python 2.6.x/old 2.7.x
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# http://bugs.python.org/issue10963
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# The quick exit is typically caused by the openssl command not being
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# able to read an input file, so check ourselves if can't read a file.
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retcode, err = _check_files_accessible(files)
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if process.stderr:
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msg = process.stderr.read()
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err = err + msg.decode('utf-8')
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output = ''
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else:
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retcode = process.poll()
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if err is not None:
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err = err.decode('utf-8')
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return output, err, retcode
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def _encoding_for_form(inform):
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if inform == PKI_ASN1_FORM:
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encoding = 'UTF-8'
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elif inform == PKIZ_CMS_FORM:
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encoding = 'hex'
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else:
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raise ValueError(
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_('"inform" must be one of: %s') % ','.join((PKI_ASN1_FORM,
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PKIZ_CMS_FORM)))
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return encoding
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def cms_verify(formatted, signing_cert_file_name, ca_file_name,
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inform=PKI_ASN1_FORM):
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"""Verifies the signature of the contents IAW CMS syntax.
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:raises subprocess.CalledProcessError:
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:raises keystoneclient.exceptions.CertificateConfigError: if certificate
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is not configured
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properly.
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"""
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_ensure_subprocess()
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if isinstance(formatted, six.string_types):
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data = bytearray(formatted, _encoding_for_form(inform))
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else:
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data = formatted
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process = subprocess.Popen(['openssl', 'cms', '-verify',
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'-certfile', signing_cert_file_name,
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'-CAfile', ca_file_name,
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'-inform', 'PEM',
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'-nosmimecap', '-nodetach',
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'-nocerts', '-noattr'],
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE,
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close_fds=True)
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output, err, retcode = _process_communicate_handle_oserror(
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process, data, (signing_cert_file_name, ca_file_name))
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# Do not log errors, as some happen in the positive thread
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# instead, catch them in the calling code and log them there.
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# When invoke the openssl with not exist file, return code 2
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# and error msg will be returned.
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# You can get more from
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# http://www.openssl.org/docs/apps/cms.html#EXIT_CODES
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#
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# $ openssl cms -verify -certfile not_exist_file -CAfile
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# not_exist_file -inform PEM -nosmimecap -nodetach
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# -nocerts -noattr
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# Error opening certificate file not_exist_file
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#
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if retcode == OpensslCmsExitStatus.INPUT_FILE_READ_ERROR:
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if err.startswith('Error reading S/MIME message'):
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raise exceptions.CMSError(err)
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else:
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raise exceptions.CertificateConfigError(err)
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elif retcode != OpensslCmsExitStatus.SUCCESS:
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# NOTE(dmllr): Python 2.6 compatibility:
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# CalledProcessError did not have output keyword argument
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e = subprocess.CalledProcessError(retcode, 'openssl')
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e.output = err
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raise e
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return output
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def is_pkiz(token_text):
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"""Determine if a token a cmsz token
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Checks if the string has the prefix that indicates it is a
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Crypto Message Syntax, Z compressed token.
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"""
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return token_text.startswith(PKIZ_PREFIX)
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def pkiz_sign(text,
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signing_cert_file_name,
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signing_key_file_name,
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compression_level=6,
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message_digest=DEFAULT_TOKEN_DIGEST_ALGORITHM):
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signed = cms_sign_data(text,
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signing_cert_file_name,
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signing_key_file_name,
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PKIZ_CMS_FORM,
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message_digest=message_digest)
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compressed = zlib.compress(signed, compression_level)
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encoded = PKIZ_PREFIX + base64.urlsafe_b64encode(
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compressed).decode('utf-8')
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return encoded
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def pkiz_uncompress(signed_text):
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text = signed_text[len(PKIZ_PREFIX):].encode('utf-8')
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unencoded = base64.urlsafe_b64decode(text)
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uncompressed = zlib.decompress(unencoded)
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return uncompressed
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def pkiz_verify(signed_text, signing_cert_file_name, ca_file_name):
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uncompressed = pkiz_uncompress(signed_text)
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return cms_verify(uncompressed, signing_cert_file_name, ca_file_name,
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inform=PKIZ_CMS_FORM)
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# This function is deprecated and will be removed once the ASN1 token format
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# is no longer required. It is only here to be used for testing.
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def token_to_cms(signed_text):
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"""Converts a custom formatted token to a PEM-formatted token.
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See documentation for cms_to_token() for details on the custom formatting.
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"""
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copy_of_text = signed_text.replace('-', '/')
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lines = ['-----BEGIN CMS-----']
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lines += textwrap.wrap(copy_of_text, 64)
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lines.append('-----END CMS-----\n')
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return '\n'.join(lines)
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def verify_token(token, signing_cert_file_name, ca_file_name):
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return cms_verify(token_to_cms(token),
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signing_cert_file_name,
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ca_file_name)
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def is_asn1_token(token):
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"""Determine if a token appears to be PKI-based.
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thx to ayoung for sorting this out.
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base64 decoded hex representation of MII is 3082::
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In [3]: binascii.hexlify(base64.b64decode('MII='))
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Out[3]: '3082'
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re: http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
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::
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pg4: For tags from 0 to 30 the first octet is the identfier
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pg10: Hex 30 means sequence, followed by the length of that sequence.
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pg5: Second octet is the length octet
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first bit indicates short or long form, next 7 bits encode the
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number of subsequent octets that make up the content length octets
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as an unsigned binary int
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82 = 10000010 (first bit indicates long form)
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0000010 = 2 octets of content length
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so read the next 2 octets to get the length of the content.
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In the case of a very large content length there could be a requirement to
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have more than 2 octets to designate the content length, therefore
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requiring us to check for MIM, MIQ, etc.
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::
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In [4]: base64.b64encode(binascii.a2b_hex('3083'))
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Out[4]: 'MIM='
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In [5]: base64.b64encode(binascii.a2b_hex('3084'))
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Out[5]: 'MIQ='
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Checking for MI would become invalid at 16 octets of content length
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10010000 = 90
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In [6]: base64.b64encode(binascii.a2b_hex('3090'))
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Out[6]: 'MJA='
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Checking for just M is insufficient
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But we will only check for MII:
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Max length of the content using 2 octets is 3FFF or 16383.
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It's not practical to support a token of this length or greater in http
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therefore, we will check for MII only and ignore the case of larger tokens
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"""
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return token[:3] == PKI_ASN1_PREFIX
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def is_ans1_token(token):
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"""Deprecated. Use is_asn1_token() instead."""
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LOG.warning(_LW('The function is_ans1_token() is deprecated, '
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'use is_asn1_token() instead.'))
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return is_asn1_token(token)
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def cms_sign_text(data_to_sign, signing_cert_file_name, signing_key_file_name,
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message_digest=DEFAULT_TOKEN_DIGEST_ALGORITHM):
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return cms_sign_data(data_to_sign, signing_cert_file_name,
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signing_key_file_name, message_digest=message_digest)
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def cms_sign_data(data_to_sign, signing_cert_file_name, signing_key_file_name,
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outform=PKI_ASN1_FORM,
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message_digest=DEFAULT_TOKEN_DIGEST_ALGORITHM):
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"""Uses OpenSSL to sign a document.
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Produces a Base64 encoding of a DER formatted CMS Document
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http://en.wikipedia.org/wiki/Cryptographic_Message_Syntax
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:param data_to_sign: data to sign
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:param signing_cert_file_name: path to the X509 certificate containing
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the public key associated with the private key used to sign the data
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:param signing_key_file_name: path to the private key used to sign
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the data
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:param outform: Format for the signed document PKIZ_CMS_FORM or
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PKI_ASN1_FORM
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:param message_digest: Digest algorithm to use when signing or resigning
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"""
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_ensure_subprocess()
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if isinstance(data_to_sign, six.string_types):
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data = bytearray(data_to_sign, encoding='utf-8')
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else:
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data = data_to_sign
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process = subprocess.Popen(['openssl', 'cms', '-sign',
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'-signer', signing_cert_file_name,
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'-inkey', signing_key_file_name,
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'-outform', 'PEM',
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'-nosmimecap', '-nodetach',
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'-nocerts', '-noattr',
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'-md', message_digest, ],
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE,
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close_fds=True)
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output, err, retcode = _process_communicate_handle_oserror(
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process, data, (signing_cert_file_name, signing_key_file_name))
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if retcode != OpensslCmsExitStatus.SUCCESS or ('Error' in err):
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if retcode == OpensslCmsExitStatus.CREATE_CMS_READ_MIME_ERROR:
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LOG.error(_LE('Signing error: Unable to load certificate - '
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'ensure you have configured PKI with '
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'"keystone-manage pki_setup"'))
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else:
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LOG.error(_LE('Signing error: %s'), err)
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raise subprocess.CalledProcessError(retcode, 'openssl')
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if outform == PKI_ASN1_FORM:
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return output.decode('utf-8')
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else:
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return output
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def cms_sign_token(text, signing_cert_file_name, signing_key_file_name,
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message_digest=DEFAULT_TOKEN_DIGEST_ALGORITHM):
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output = cms_sign_data(text, signing_cert_file_name, signing_key_file_name,
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message_digest=message_digest)
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return cms_to_token(output)
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def cms_to_token(cms_text):
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"""Converts a CMS-signed token in PEM format to a custom URL-safe format.
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The conversion consists of replacing '/' char in the PEM-formatted token
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with the '-' char and doing other such textual replacements to make the
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result marshallable via HTTP. The return value can thus be used as the
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value of a HTTP header such as "X-Auth-Token".
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This ad-hoc conversion is an unfortunate oversight since the returned
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value now does not conform to any of the standard variants of base64
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encoding. It would have been better to use base64url encoding (either on
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the PEM formatted text or, perhaps even better, on the inner CMS-signed
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binary value without any PEM formatting). In any case, the same conversion
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is done in reverse in the other direction (for token verification), so
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there are no correctness issues here. Note that the non-standard encoding
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of the token will be preserved so as to not break backward compatibility.
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The conversion issue is detailed by the code author in a blog post at
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http://adam.younglogic.com/2014/02/compressed-tokens/.
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"""
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start_delim = '-----BEGIN CMS-----'
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end_delim = '-----END CMS-----'
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signed_text = cms_text
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signed_text = signed_text.replace('/', '-')
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signed_text = signed_text.replace(start_delim, '')
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signed_text = signed_text.replace(end_delim, '')
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signed_text = signed_text.replace('\n', '')
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return signed_text
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def cms_hash_token(token_id, mode='md5'):
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"""Hash PKI tokens.
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return: for asn1 or pkiz tokens, returns the hash of the passed in token
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otherwise, returns what it was passed in.
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"""
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if token_id is None:
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return None
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if is_asn1_token(token_id) or is_pkiz(token_id):
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hasher = hashlib.new(mode)
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if isinstance(token_id, six.text_type):
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token_id = token_id.encode('utf-8')
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hasher.update(token_id)
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return hasher.hexdigest()
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else:
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return token_id
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