509 lines
17 KiB
Python
509 lines
17 KiB
Python
# Copyright 2013 Red Hat, Inc.
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#
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# 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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"""
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PEM formatted data is used frequently in conjunction with X509 PKI as
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a data exchange mechanism for binary data. The acronym PEM stands for
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Privacy Enhanced Mail as defined in RFC-1421. Contrary to expectation
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the PEM format in common use has little to do with RFC-1421. Instead
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what we know as PEM format grew out of the need for a data exchange
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mechanism largely by the influence of OpenSSL. Other X509
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implementations have adopted it.
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Unfortunately PEM format has never been officially standarized. It's
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basic format is as follows:
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1) A header consisting of 5 hyphens followed by the word BEGIN and a
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single space. Then an upper case string describing the contents of the
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PEM block, this is followed by 5 hyphens and a newline.
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2) Binary data (typically in DER ASN.1 format) encoded in base64. The
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base64 text is line wrapped so that each line of base64 is 64
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characters long and terminated with a newline. The last line of base64
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text may be less than 64 characters. The content and format of the
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binary data is entirely dependent upon the type of data announced in
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the header and footer.
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3) A footer in the exact same as the header except the word BEGIN is
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replaced by END. The content name in both the header and footer should
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exactly match.
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The above is called a PEM block. It is permissible for multiple PEM
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blocks to appear in a single file or block of text. This is often used
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when specifying multiple X509 certificates.
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An example PEM block for a certificate is:
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-----BEGIN CERTIFICATE-----
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MIIC0TCCAjqgAwIBAgIJANsHKV73HYOwMA0GCSqGSIb3DQEBBQUAMIGeMQowCAYD
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VQQFEwE1MQswCQYDVQQGEwJVUzELMAkGA1UECBMCQ0ExEjAQBgNVBAcTCVN1bm55
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dmFsZTESMBAGA1UEChMJT3BlblN0YWNrMREwDwYDVQQLEwhLZXlzdG9uZTElMCMG
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CSqGSIb3DQEJARYWa2V5c3RvbmVAb3BlbnN0YWNrLm9yZzEUMBIGA1UEAxMLU2Vs
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ZiBTaWduZWQwIBcNMTIxMTA1MTgxODI0WhgPMjA3MTA0MzAxODE4MjRaMIGeMQow
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CAYDVQQFEwE1MQswCQYDVQQGEwJVUzELMAkGA1UECBMCQ0ExEjAQBgNVBAcTCVN1
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bm55dmFsZTESMBAGA1UEChMJT3BlblN0YWNrMREwDwYDVQQLEwhLZXlzdG9uZTEl
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MCMGCSqGSIb3DQEJARYWa2V5c3RvbmVAb3BlbnN0YWNrLm9yZzEUMBIGA1UEAxML
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U2VsZiBTaWduZWQwgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBALzI17ExCaqd
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r7xY2Q5CBZ1bW1lsrXxS8eNJRdQtskDuQVAluY03/OGZd8HQYiiY/ci2tYy7BNIC
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bh5GaO95eqTDykJR3liOYE/tHbY6puQlj2ZivmhlSd2d5d7lF0/H28RQsLu9VktM
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uw6q9DpDm35jfrr8LgSeA3MdVqcS/4OhAgMBAAGjEzARMA8GA1UdEwEB/wQFMAMB
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Af8wDQYJKoZIhvcNAQEFBQADgYEAjSQND7i1dNZtLKpWgX+JqMr3BdVlM15mFeVr
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C26ZspZjZVY5okdozO9gU3xcwRe4Cg30sKFOe6EBQKpkTZucFOXwBtD3h6dWJrdD
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c+m/CL/rs0GatDavbaIT2vv405SQUQooCdVh72LYel+4/a6xmRd7fQx3iEXN9QYj
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vmHJUcA=
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-----END CERTIFICATE-----
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PEM format is safe for transmission in 7-bit ASCII systems
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(i.e. standard email). Since 7-bit ASCII is a proper subset of UTF-8
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and Latin-1 it is not affected by transcoding between those
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charsets. Nor is PEM format affected by the choice of line
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endings. This makes PEM format particularity attractive for transport
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and storage of binary data.
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This module provides a number of utilities supporting the generation
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and consumption of PEM formatted data including:
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* parse text and find all PEM blocks contained in the
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text. Information on the location of the block in the text, the
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type of PEM block, and it's base64 and binary data contents.
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* parse text assumed to contain PEM data and return the binary
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data.
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* test if a block of text is a PEM block
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* convert base64 text into a formatted PEM block
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* convert binary data into a formatted PEM block
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* access to the valid PEM types and their headers
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"""
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import base64
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import re
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import six
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from keystone.common import base64utils
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from keystone.i18n import _
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PEM_TYPE_TO_HEADER = {
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u'cms': u'CMS',
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u'dsa-private': u'DSA PRIVATE KEY',
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u'dsa-public': u'DSA PUBLIC KEY',
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u'ecdsa-public': u'ECDSA PUBLIC KEY',
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u'ec-private': u'EC PRIVATE KEY',
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u'pkcs7': u'PKCS7',
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u'pkcs7-signed': u'PKCS',
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u'pkcs8': u'ENCRYPTED PRIVATE KEY',
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u'private-key': u'PRIVATE KEY',
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u'public-key': u'PUBLIC KEY',
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u'rsa-private': u'RSA PRIVATE KEY',
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u'rsa-public': u'RSA PUBLIC KEY',
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u'cert': u'CERTIFICATE',
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u'crl': u'X509 CRL',
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u'cert-pair': u'CERTIFICATE PAIR',
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u'csr': u'CERTIFICATE REQUEST',
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}
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# This is not a 1-to-1 reverse map of PEM_TYPE_TO_HEADER
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# because it includes deprecated headers that map to 1 pem_type.
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PEM_HEADER_TO_TYPE = {
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u'CMS': u'cms',
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u'DSA PRIVATE KEY': u'dsa-private',
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u'DSA PUBLIC KEY': u'dsa-public',
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u'ECDSA PUBLIC KEY': u'ecdsa-public',
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u'EC PRIVATE KEY': u'ec-private',
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u'PKCS7': u'pkcs7',
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u'PKCS': u'pkcs7-signed',
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u'ENCRYPTED PRIVATE KEY': u'pkcs8',
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u'PRIVATE KEY': u'private-key',
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u'PUBLIC KEY': u'public-key',
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u'RSA PRIVATE KEY': u'rsa-private',
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u'RSA PUBLIC KEY': u'rsa-public',
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u'CERTIFICATE': u'cert',
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u'X509 CERTIFICATE': u'cert',
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u'CERTIFICATE PAIR': u'cert-pair',
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u'X509 CRL': u'crl',
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u'CERTIFICATE REQUEST': u'csr',
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u'NEW CERTIFICATE REQUEST': u'csr',
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}
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# List of valid pem_types
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pem_types = sorted(PEM_TYPE_TO_HEADER.keys())
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# List of valid pem_headers
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pem_headers = sorted(PEM_TYPE_TO_HEADER.values())
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_pem_begin_re = re.compile(r'^-{5}BEGIN\s+([^-]+)-{5}\s*$', re.MULTILINE)
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_pem_end_re = re.compile(r'^-{5}END\s+([^-]+)-{5}\s*$', re.MULTILINE)
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class PEMParseResult(object):
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"""Information returned when a PEM block is found in text.
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PEMParseResult contains information about a PEM block discovered
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while parsing text. The following properties are defined:
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pem_type
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A short hand name for the type of the PEM data, e.g. cert,
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csr, crl, cms, key. Valid pem_types are listed in pem_types.
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When the pem_type is set the pem_header is updated to match it.
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pem_header
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The text following '-----BEGIN ' in the PEM header.
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Common examples are:
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-----BEGIN CERTIFICATE-----
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-----BEGIN CMS-----
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Thus the pem_header would be CERTIFICATE and CMS respectively.
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When the pem_header is set the pem_type is updated to match it.
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pem_start, pem_end
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The beginning and ending positions of the PEM block
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including the PEM header and footer.
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base64_start, base64_end
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The beginning and ending positions of the base64 data
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contained inside the PEM header and footer. Includes trailing
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new line
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binary_data
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The decoded base64 data. None if not decoded.
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"""
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def __init__(self, pem_type=None, pem_header=None,
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pem_start=None, pem_end=None,
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base64_start=None, base64_end=None,
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binary_data=None):
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self._pem_type = None
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self._pem_header = None
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if pem_type is not None:
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self.pem_type = pem_type
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if pem_header is not None:
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self.pem_header = pem_header
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self.pem_start = pem_start
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self.pem_end = pem_end
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self.base64_start = base64_start
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self.base64_end = base64_end
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self.binary_data = binary_data
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@property
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def pem_type(self):
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return self._pem_type
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@pem_type.setter
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def pem_type(self, pem_type):
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if pem_type is None:
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self._pem_type = None
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self._pem_header = None
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else:
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pem_header = PEM_TYPE_TO_HEADER.get(pem_type)
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if pem_header is None:
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raise ValueError(_('unknown pem_type "%(pem_type)s", '
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'valid types are: %(valid_pem_types)s') %
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{'pem_type': pem_type,
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'valid_pem_types': ', '.join(pem_types)})
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self._pem_type = pem_type
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self._pem_header = pem_header
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@property
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def pem_header(self):
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return self._pem_header
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@pem_header.setter
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def pem_header(self, pem_header):
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if pem_header is None:
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self._pem_type = None
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self._pem_header = None
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else:
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pem_type = PEM_HEADER_TO_TYPE.get(pem_header)
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if pem_type is None:
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raise ValueError(_('unknown pem header "%(pem_header)s", '
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'valid headers are: '
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'%(valid_pem_headers)s') %
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{'pem_header': pem_header,
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'valid_pem_headers':
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', '.join("'%s'" %
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[x for x in pem_headers])})
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self._pem_type = pem_type
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self._pem_header = pem_header
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def pem_search(text, start=0):
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"""Search for a block of PEM formatted data
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Search for a PEM block in a text string. The search begins at
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start. If a PEM block is found a PEMParseResult object is
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returned, otherwise if no PEM block is found None is returned.
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If the pem_type is not the same in both the header and footer
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a ValueError is raised.
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The start and end positions are suitable for use as slices into
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the text. To search for multiple PEM blocks pass pem_end as the
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start position for the next iteration. Terminate the iteration
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when None is returned. Example::
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start = 0
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while True:
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block = pem_search(text, start)
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if block is None:
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break
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base64_data = text[block.base64_start : block.base64_end]
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start = block.pem_end
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:param text: the text to search for PEM blocks
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:type text: string
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:param start: the position in text to start searching from (default: 0)
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:type start: int
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:returns: PEMParseResult or None if not found
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:raises: ValueError
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"""
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match = _pem_begin_re.search(text, pos=start)
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if match:
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pem_start = match.start()
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begin_text = match.group(0)
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base64_start = min(len(text), match.end() + 1)
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begin_pem_header = match.group(1).strip()
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match = _pem_end_re.search(text, pos=base64_start)
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if match:
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pem_end = min(len(text), match.end() + 1)
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base64_end = match.start()
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end_pem_header = match.group(1).strip()
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else:
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raise ValueError(_('failed to find end matching "%s"') %
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begin_text)
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if begin_pem_header != end_pem_header:
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raise ValueError(_('beginning & end PEM headers do not match '
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'(%(begin_pem_header)s'
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'!= '
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'%(end_pem_header)s)') %
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{'begin_pem_header': begin_pem_header,
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'end_pem_header': end_pem_header})
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else:
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return None
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result = PEMParseResult(pem_header=begin_pem_header,
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pem_start=pem_start, pem_end=pem_end,
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base64_start=base64_start, base64_end=base64_end)
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return result
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def parse_pem(text, pem_type=None, max_items=None):
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"""Scan text for PEM data, return list of PEM items
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The input text is scanned for PEM blocks, for each one found a
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PEMParseResult is constructed and added to the return list.
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pem_type operates as a filter on the type of PEM desired. If
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pem_type is specified only those PEM blocks which match will be
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included. The pem_type is a logical name, not the actual text in
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the pem header (e.g. 'cert'). If the pem_type is None all PEM
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blocks are returned.
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If max_items is specified the result is limited to that number of
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items.
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The return value is a list of PEMParseResult objects. The
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PEMParseResult provides complete information about the PEM block
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including the decoded binary data for the PEM block. The list is
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ordered in the same order as found in the text.
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Examples::
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# Get all certs
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certs = parse_pem(text, 'cert')
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# Get the first cert
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try:
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binary_cert = parse_pem(text, 'cert', 1)[0].binary_data
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except IndexError:
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raise ValueError('no cert found')
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:param text: The text to search for PEM blocks
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:type text: string
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:param pem_type: Only return data for this pem_type.
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Valid types are: csr, cert, crl, cms, key.
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If pem_type is None no filtering is performed.
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(default: None)
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:type pem_type: string or None
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:param max_items: Limit the number of blocks returned. (default: None)
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:type max_items: int or None
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:return: List of PEMParseResult, one for each PEM block found
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:raises: ValueError, InvalidBase64Error
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"""
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pem_blocks = []
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start = 0
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while True:
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block = pem_search(text, start)
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if block is None:
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break
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start = block.pem_end
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if pem_type is None:
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pem_blocks.append(block)
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else:
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try:
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if block.pem_type == pem_type:
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pem_blocks.append(block)
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except KeyError:
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raise ValueError(_('unknown pem_type: "%s"') % (pem_type))
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if max_items is not None and len(pem_blocks) >= max_items:
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break
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for block in pem_blocks:
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base64_data = text[block.base64_start:block.base64_end]
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try:
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binary_data = base64.b64decode(base64_data)
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except Exception as e:
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block.binary_data = None
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raise base64utils.InvalidBase64Error(
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_('failed to base64 decode %(pem_type)s PEM at position'
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'%(position)d: %(err_msg)s') %
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{'pem_type': block.pem_type,
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'position': block.pem_start,
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'err_msg': six.text_type(e)})
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else:
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block.binary_data = binary_data
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return pem_blocks
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def get_pem_data(text, pem_type='cert'):
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"""Scan text for PEM data, return binary contents
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The input text is scanned for a PEM block which matches the pem_type.
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If found the binary data contained in the PEM block is returned.
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If no PEM block is found or it does not match the specified pem type
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None is returned.
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:param text: The text to search for the PEM block
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:type text: string
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:param pem_type: Only return data for this pem_type.
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Valid types are: csr, cert, crl, cms, key.
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(default: 'cert')
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:type pem_type: string
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:return: binary data or None if not found.
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"""
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blocks = parse_pem(text, pem_type, 1)
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if not blocks:
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return None
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return blocks[0].binary_data
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def is_pem(text, pem_type='cert'):
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"""Does this text contain a PEM block.
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Check for the existence of a PEM formatted block in the
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text, if one is found verify it's contents can be base64
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decoded, if so return True. Return False otherwise.
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:param text: The text to search for PEM blocks
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:type text: string
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:param pem_type: Only return data for this pem_type.
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Valid types are: csr, cert, crl, cms, key.
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(default: 'cert')
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:type pem_type: string
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:returns: bool -- True if text contains PEM matching the pem_type,
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False otherwise.
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"""
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try:
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pem_blocks = parse_pem(text, pem_type, max_items=1)
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except base64utils.InvalidBase64Error:
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return False
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if pem_blocks:
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return True
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else:
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return False
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def base64_to_pem(base64_text, pem_type='cert'):
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"""Format string of base64 text into PEM format
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Input is assumed to consist only of members of the base64 alphabet
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(i.e no whitepace). Use one of the filter functions from
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base64utils to assure the input is clean
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(i.e. strip_whitespace()).
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:param base64_text: text containing ONLY base64 alphabet
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characters to be inserted into PEM output.
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:type base64_text: string
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:param pem_type: Produce a PEM block for this type.
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Valid types are: csr, cert, crl, cms, key.
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(default: 'cert')
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:type pem_type: string
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:returns: string -- PEM formatted text
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|
|
"""
|
|
pem_header = PEM_TYPE_TO_HEADER[pem_type]
|
|
buf = six.StringIO()
|
|
|
|
buf.write(u'-----BEGIN %s-----' % pem_header)
|
|
buf.write(u'\n')
|
|
|
|
for line in base64utils.base64_wrap_iter(base64_text, width=64):
|
|
buf.write(line)
|
|
buf.write(u'\n')
|
|
|
|
buf.write(u'-----END %s-----' % pem_header)
|
|
buf.write(u'\n')
|
|
|
|
text = buf.getvalue()
|
|
buf.close()
|
|
return text
|
|
|
|
|
|
def binary_to_pem(binary_data, pem_type='cert'):
|
|
"""Format binary data into PEM format
|
|
|
|
Example:
|
|
|
|
# get the certificate binary data in DER format
|
|
der_data = certificate.der
|
|
# convert the DER binary data into a PEM
|
|
pem = binary_to_pem(der_data, 'cert')
|
|
|
|
|
|
:param binary_data: binary data to encapsulate into PEM
|
|
:type binary_data: buffer
|
|
:param pem_type: Produce a PEM block for this type.
|
|
Valid types are: csr, cert, crl, cms, key.
|
|
(default: 'cert')
|
|
:type pem_type: string
|
|
:returns: string -- PEM formatted text
|
|
|
|
"""
|
|
base64_text = base64.b64encode(binary_data)
|
|
return base64_to_pem(base64_text, pem_type)
|