freeipa/ipalib/pkcs10.py

# Authors:
#   Rob Crittenden <rcritten@redhat.com>
#
# Copyright (C) 2010  Red Hat
# see file 'COPYING' for use and warranty information
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from __future__ import print_function

import sys
import base64
import nss.nss as nss
from pyasn1.type import univ, namedtype, tag
from pyasn1.codec.der import decoder
import six
from ipalib import x509

if six.PY3:
    unicode = str

PEM = 0
DER = 1

def get_subject(csr, datatype=PEM):
    """
    Given a CSR return the subject value.

    This returns an nss.DN object.
    """
    request = load_certificate_request(csr, datatype)
    try:
        return request.subject
    finally:
        del request

def get_extensions(csr, datatype=PEM):
    """
    Given a CSR return OIDs of certificate extensions.

    The return value is a tuple of strings
    """
    request = load_certificate_request(csr, datatype)

    # Work around a bug in python-nss where nss.oid_dotted_decimal
    # errors on unrecognised OIDs
    #
    # https://bugzilla.redhat.com/show_bug.cgi?id=1246729
    #
    def get_prefixed_oid_str(ext):
        """Returns a string like 'OID.1.2...'."""
        if ext.oid_tag == 0:
            return repr(ext)
        else:
            return nss.oid_dotted_decimal(ext.oid)

    return tuple(get_prefixed_oid_str(ext)[4:]
                 for ext in request.extensions)


def get_subjectaltname(csr, datatype=PEM):
    """
    Given a CSR return the subjectaltname value, if any.

    The return value is a tuple of strings or None
    """
    request = load_certificate_request(csr, datatype)
    for extension in request.extensions:
        if extension.oid_tag == nss.SEC_OID_X509_SUBJECT_ALT_NAME:
            break
    else:
        return None
    del request

    return x509.decode_generalnames(extension.value)


# Unfortunately, NSS can only parse the extension request attribute, so
# we have to parse friendly name ourselves (see RFC 2986)
class _Attribute(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('type', univ.ObjectIdentifier()),
        namedtype.NamedType('values', univ.Set()),
        )

class _Attributes(univ.SetOf):
    componentType = _Attribute()

class _CertificationRequestInfo(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('version', univ.Integer()),
        namedtype.NamedType('subject', univ.Sequence()),
        namedtype.NamedType('subjectPublicKeyInfo', univ.Sequence()),
        namedtype.OptionalNamedType('attributes', _Attributes().subtype(
            implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 0)))
        )

class _CertificationRequest(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('certificationRequestInfo',
                            _CertificationRequestInfo()),
        namedtype.NamedType('signatureAlgorithm', univ.Sequence()),
        namedtype.NamedType('signatureValue', univ.BitString()),
        )

_FRIENDLYNAME = univ.ObjectIdentifier('1.2.840.113549.1.9.20')

def get_friendlyname(csr, datatype=PEM):
    """
    Given a CSR return the value of the friendlyname attribute, if any.

    The return value is a string.
    """
    if datatype == PEM:
        csr = strip_header(csr)
        csr = base64.b64decode(csr)

    csr = decoder.decode(csr, asn1Spec=_CertificationRequest())[0]
    for attribute in csr['certificationRequestInfo']['attributes']:
        if attribute['type'] == _FRIENDLYNAME:
            return unicode(attribute['values'][0])

    return None

def strip_header(csr):
    """
    Remove the header and footer from a CSR.
    """
    headerlen = 40
    s = csr.find("-----BEGIN NEW CERTIFICATE REQUEST-----")
    if s == -1:
        headerlen = 36
        s = csr.find("-----BEGIN CERTIFICATE REQUEST-----")
    if s >= 0:
        e = csr.find("-----END")
        csr = csr[s+headerlen:e]

    return csr

def load_certificate_request(csr, datatype=PEM):
    """
    Given a base64-encoded certificate request, with or without the
    header/footer, return a request object.
    """
    if datatype == PEM:
        csr = strip_header(csr)
        csr = base64.b64decode(csr)

    # A fail-safe so we can always read a CSR. python-nss/NSS will segfault
    # otherwise
    if not nss.nss_is_initialized():
        nss.nss_init_nodb()

    return nss.CertificateRequest(csr)

if __name__ == '__main__':
    nss.nss_init_nodb()

    # Read PEM request from stdin and print out its components

    csrlines = sys.stdin.readlines()
    csr = ''.join(csrlines)

    print(load_certificate_request(csr))
    print(get_subject(csr))
    print(get_subjectaltname(csr))
    print(get_friendlyname(csr))