# Authors:
#   Jan Cholasta <jcholast@redhat.com>
#
# Copyright (C) 2014  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/>.
#

"""
LDAP shared certificate store.
"""

from nss.error import NSPRError
from pyasn1.error import PyAsn1Error

from ipapython.dn import DN
from ipapython.certdb import get_ca_nickname
from ipalib import errors, x509


def _parse_cert(dercert):
    try:
        subject = x509.get_subject(dercert, x509.DER)
        issuer = x509.get_issuer(dercert, x509.DER)
        serial_number = x509.get_serial_number(dercert, x509.DER)
        public_key_info = x509.get_der_public_key_info(dercert, x509.DER)
    except (NSPRError, PyAsn1Error), e:
        raise ValueError("failed to decode certificate: %s" % e)

    subject = str(subject).replace('\\;', '\\3b')
    issuer = str(issuer).replace('\\;', '\\3b')
    issuer_serial = '%s;%s' % (issuer, serial_number)

    return subject, issuer_serial, public_key_info


def init_ca_entry(entry, dercert, nickname, trusted, ext_key_usage):
    """
    Initialize certificate store entry for a CA certificate.
    """
    subject, issuer_serial, public_key = _parse_cert(dercert)

    if ext_key_usage is not None:
        try:
            cert_eku = x509.get_ext_key_usage(dercert, x509.DER)
        except NSPRError, e:
            raise ValueError("failed to decode certificate: %s" % e)
        if cert_eku is not None:
            cert_eku -= {x509.EKU_SERVER_AUTH, x509.EKU_CLIENT_AUTH,
                         x509.EKU_EMAIL_PROTECTION, x509.EKU_CODE_SIGNING,
                         x509.EKU_ANY, x509.EKU_PLACEHOLDER}
            ext_key_usage = ext_key_usage | cert_eku

    entry['objectClass'] = ['ipaCertificate', 'pkiCA', 'ipaKeyPolicy']
    entry['cn'] = [nickname]

    entry['ipaCertSubject'] = [subject]
    entry['ipaCertIssuerSerial'] = [issuer_serial]
    entry['ipaPublicKey'] = [public_key]
    entry['cACertificate;binary'] = [dercert]

    if trusted is not None:
        entry['ipaKeyTrust'] = ['trusted' if trusted else 'distrusted']
    if ext_key_usage is not None:
        ext_key_usage = list(ext_key_usage)
        if not ext_key_usage:
            ext_key_usage.append(x509.EKU_PLACEHOLDER)
        entry['ipaKeyExtUsage'] = ext_key_usage


def update_compat_ca(ldap, base_dn, dercert):
    """
    Update the CA certificate in cn=CAcert,cn=ipa,cn=etc,SUFFIX.
    """
    dn = DN(('cn', 'CAcert'), ('cn', 'ipa'), ('cn', 'etc'), base_dn)
    try:
        entry = ldap.get_entry(dn, attrs_list=['cACertificate;binary'])
        entry.single_value['cACertificate;binary'] = dercert
        ldap.update_entry(entry)
    except errors.NotFound:
        entry = ldap.make_entry(dn)
        entry['objectClass'] = ['nsContainer', 'pkiCA']
        entry.single_value['cn'] = 'CAcert'
        entry.single_value['cACertificate;binary'] = dercert
        ldap.add_entry(entry)
    except errors.EmptyModlist:
        pass


def clean_old_config(ldap, base_dn, dn, config_ipa, config_compat):
    """
    Remove ipaCA and compatCA flags from their previous carriers.
    """
    if not config_ipa and not config_compat:
        return

    try:
        result, truncated = ldap.find_entries(
            base_dn=DN(('cn', 'certificates'), ('cn', 'ipa'), ('cn', 'etc'),
                       base_dn),
            filter='(|(ipaConfigString=ipaCA)(ipaConfigString=compatCA))',
            attrs_list=['ipaConfigString'])
    except errors.NotFound:
        return

    for entry in result:
        if entry.dn == dn:
            continue
        for config in list(entry['ipaConfigString']):
            if config.lower() == 'ipaca' and config_ipa:
                entry['ipaConfigString'].remove(config)
            elif config.lower() == 'compatca' and config_compat:
                entry['ipaConfigString'].remove(config)
        try:
            ldap.update_entry(entry)
        except errors.EmptyModlist:
            pass


def add_ca_cert(ldap, base_dn, dercert, nickname, trusted=None,
                ext_key_usage=None, config_ipa=False, config_compat=False):
    """
    Add new entry for a CA certificate to the certificate store.
    """
    container_dn = DN(('cn', 'certificates'), ('cn', 'ipa'), ('cn', 'etc'),
                      base_dn)
    dn = DN(('cn', nickname), container_dn)
    entry = ldap.make_entry(dn)

    init_ca_entry(entry, dercert, nickname, trusted, ext_key_usage)

    if config_ipa:
        entry.setdefault('ipaConfigString', []).append('ipaCA')
    if config_compat:
        entry.setdefault('ipaConfigString', []).append('compatCA')

    if config_compat:
        update_compat_ca(ldap, base_dn, dercert)

    ldap.add_entry(entry)
    clean_old_config(ldap, base_dn, dn, config_ipa, config_compat)


def update_ca_cert(ldap, base_dn, dercert, trusted=None, ext_key_usage=None,
                   config_ipa=False, config_compat=False):
    """
    Update existing entry for a CA certificate in the certificate store.
    """
    subject, issuer_serial, public_key = _parse_cert(dercert)

    filter = ldap.make_filter({'ipaCertSubject': subject})
    result, truncated = ldap.find_entries(
        base_dn=DN(('cn', 'certificates'), ('cn', 'ipa'), ('cn', 'etc'),
                   base_dn),
        filter=filter,
        attrs_list=['cn', 'ipaCertSubject', 'ipaCertIssuerSerial',
                    'ipaPublicKey', 'ipaKeyTrust', 'ipaKeyExtUsage',
                    'ipaConfigString', 'cACertificate;binary'])
    entry = result[0]
    dn = entry.dn

    for old_cert in entry['cACertificate;binary']:
        # Check if we are adding a new cert
        if old_cert == dercert:
            break
    else:
        # We are adding a new cert, validate it
        if entry.single_value['ipaCertSubject'].lower() != subject.lower():
            raise ValueError("subject name mismatch")
        if entry.single_value['ipaPublicKey'] != public_key:
            raise ValueError("subject public key info mismatch")
        entry['ipaCertIssuerSerial'].append(issuer_serial)
        entry['cACertificate;binary'].append(dercert)

    # Update key trust
    if trusted is not None:
        old_trust = entry.single_value.get('ipaKeyTrust')
        new_trust = 'trusted' if trusted else 'distrusted'
        if old_trust is not None and old_trust.lower() != new_trust:
            raise ValueError("inconsistent trust")
        entry.single_value['ipaKeyTrust'] = new_trust

    # Update extended key usage
    if trusted is not False:
        if ext_key_usage is not None:
            old_eku = set(entry.get('ipaKeyExtUsage', []))
            old_eku.discard(x509.EKU_PLACEHOLDER)
            new_eku = old_eku | ext_key_usage
            if not new_eku:
                new_eku.add(x509.EKU_PLACEHOLDER)
            entry['ipaKeyExtUsage'] = list(new_eku)
    else:
        entry.pop('ipaKeyExtUsage', None)

    # Update configuration flags
    is_ipa = False
    is_compat = False
    for config in entry.get('ipaConfigString', []):
        if config.lower() == 'ipaca':
            is_ipa = True
        elif config.lower() == 'compatca':
            is_compat = True
    if config_ipa and not is_ipa:
        entry.setdefault('ipaConfigString', []).append('ipaCA')
    if config_compat and not is_compat:
        entry.setdefault('ipaConfigString', []).append('compatCA')

    if is_compat or config_compat:
        update_compat_ca(ldap, base_dn, dercert)

    ldap.update_entry(entry)
    clean_old_config(ldap, base_dn, dn, config_ipa, config_compat)


def put_ca_cert(ldap, base_dn, dercert, nickname, trusted=None,
                ext_key_usage=None, config_ipa=False, config_compat=False):
    """
    Add or update entry for a CA certificate in the certificate store.
    """
    try:
        update_ca_cert(ldap, base_dn, dercert, trusted, ext_key_usage,
                       config_ipa=config_ipa, config_compat=config_compat)
    except errors.NotFound:
        add_ca_cert(ldap, base_dn, dercert, nickname, trusted, ext_key_usage,
                    config_ipa=config_ipa, config_compat=config_compat)
    except errors.EmptyModlist:
        pass


def make_compat_ca_certs(certs, realm, ipa_ca_subject):
    """
    Make CA certificates and associated key policy from DER certificates.
    """
    result = []

    for cert in certs:
        subject, issuer_serial, public_key_info = _parse_cert(cert)
        subject = DN(subject)

        if ipa_ca_subject is not None and subject == DN(ipa_ca_subject):
            nickname = get_ca_nickname(realm)
            ext_key_usage = {x509.EKU_SERVER_AUTH,
                             x509.EKU_CLIENT_AUTH,
                             x509.EKU_EMAIL_PROTECTION,
                             x509.EKU_CODE_SIGNING}
        else:
            nickname = str(subject)
            ext_key_usage = {x509.EKU_SERVER_AUTH}

        result.append((cert, nickname, True, ext_key_usage))

    return result


def get_ca_certs(ldap, base_dn, compat_realm, compat_ipa_ca,
                 filter_subject=None):
    """
    Get CA certificates and associated key policy from the certificate store.
    """
    if filter_subject is not None:
        if not isinstance(filter_subject, list):
            filter_subject = [filter_subject]
        filter_subject = [str(subj).replace('\\;', '\\3b')
                          for subj in filter_subject]

    certs = []
    config_dn = DN(('cn', 'ipa'), ('cn', 'etc'), base_dn)
    container_dn = DN(('cn', 'certificates'), config_dn)
    try:
        # Search the certificate store for CA certificate entries
        filters = ['(objectClass=ipaCertificate)', '(objectClass=pkiCA)']
        if filter_subject:
            filter = ldap.make_filter({'ipaCertSubject': filter_subject})
            filters.append(filter)
        result, truncated = ldap.find_entries(
            base_dn=container_dn,
            filter=ldap.combine_filters(filters, ldap.MATCH_ALL),
            attrs_list=['cn', 'ipaCertSubject', 'ipaCertIssuerSerial',
                        'ipaPublicKey', 'ipaKeyTrust', 'ipaKeyExtUsage',
                        'cACertificate;binary'])

        for entry in result:
            nickname = entry.single_value['cn']
            trusted = entry.single_value.get('ipaKeyTrust', 'unknown').lower()
            if trusted == 'trusted':
                trusted = True
            elif trusted == 'distrusted':
                trusted = False
            else:
                trusted = None
            ext_key_usage = entry.get('ipaKeyExtUsage')
            if ext_key_usage is not None:
                ext_key_usage = set(str(p) for p in ext_key_usage)
                ext_key_usage.discard(x509.EKU_PLACEHOLDER)

            for cert in entry.get('cACertificate;binary', []):
                try:
                    _parse_cert(cert)
                except ValueError:
                    certs = []
                    break
                certs.append((cert, nickname, trusted, ext_key_usage))
    except errors.NotFound:
        try:
            ldap.get_entry(container_dn, [''])
        except errors.NotFound:
            # Fallback to cn=CAcert,cn=ipa,cn=etc,SUFFIX
            dn = DN(('cn', 'CAcert'), config_dn)
            entry = ldap.get_entry(dn, ['cACertificate;binary'])

            cert = entry.single_value['cACertificate;binary']
            try:
                subject, issuer_serial, public_key_info = _parse_cert(cert)
            except ValueError:
                pass
            else:
                if filter_subject is not None and subject not in filter_subject:
                    raise errors.NotFound(reason="no matching entry found")

                if compat_ipa_ca:
                    ca_subject = subject
                else:
                    ca_subject = None
                certs = make_compat_ca_certs([cert], compat_realm, ca_subject)

    if certs:
        return certs
    else:
        raise errors.NotFound(reason="no such entry")


def trust_flags_to_key_policy(trust_flags):
    """
    Convert certutil trust flags to certificate store key policy.
    """
    if 'p' in trust_flags:
        if 'C' in trust_flags or 'P' in trust_flags or 'T' in trust_flags:
            raise ValueError("cannot be both trusted and not trusted")
        return False, None, None
    elif 'C' in trust_flags or 'T' in trust_flags:
        if 'P' in trust_flags:
            raise ValueError("cannot be both CA and not CA")
        ca = True
    elif 'P' in trust_flags:
        ca = False
    else:
        return None, None, set()

    trust_flags = trust_flags.split(',')
    ext_key_usage = set()
    for i, kp in enumerate((x509.EKU_SERVER_AUTH,
                            x509.EKU_EMAIL_PROTECTION,
                            x509.EKU_CODE_SIGNING)):
        if 'C' in trust_flags[i] or 'P' in trust_flags[i]:
            ext_key_usage.add(kp)
    if 'T' in trust_flags[0]:
        ext_key_usage.add(x509.EKU_CLIENT_AUTH)

    return True, ca, ext_key_usage


def key_policy_to_trust_flags(trusted, ca, ext_key_usage):
    """
    Convert certificate store key policy to certutil trust flags.
    """
    if trusted is False:
        return 'p,p,p'
    elif trusted is None or ca is None:
        return ',,'
    elif ext_key_usage is None:
        if ca:
            return 'CT,C,C'
        else:
            return 'P,P,P'

    trust_flags = ['', '', '']
    for i, kp in enumerate((x509.EKU_SERVER_AUTH,
                            x509.EKU_EMAIL_PROTECTION,
                            x509.EKU_CODE_SIGNING)):
        if kp in ext_key_usage:
            trust_flags[i] += ('C' if ca else 'P')
    if ca and x509.EKU_CLIENT_AUTH in ext_key_usage:
        trust_flags[0] += 'T'

    trust_flags = ','.join(trust_flags)
    return trust_flags


def put_ca_cert_nss(ldap, base_dn, dercert, nickname, trust_flags,
                    config_ipa=False, config_compat=False):
    """
    Add or update entry for a CA certificate in the certificate store.
    """
    trusted, ca, ext_key_usage = trust_flags_to_key_policy(trust_flags)
    if ca is False:
        raise ValueError("must be CA certificate")

    put_ca_cert(ldap, base_dn, dercert, nickname, trusted, ext_key_usage,
                config_ipa, config_compat)


def get_ca_certs_nss(ldap, base_dn, compat_realm, compat_ipa_ca,
                     filter_subject=None):
    """
    Get CA certificates and associated trust flags from the certificate store.
    """
    nss_certs = []

    certs = get_ca_certs(ldap, base_dn, compat_realm, compat_ipa_ca,
                         filter_subject=filter_subject)
    for cert, nickname, trusted, ext_key_usage in certs:
        trust_flags = key_policy_to_trust_flags(trusted, True, ext_key_usage)
        nss_certs.append((cert, nickname, trust_flags))

    return nss_certs