Implement OTP token importing

This patch adds support for importing tokens using RFC 6030 key container
files. This includes decryption support. For sysadmin sanity, any tokens
which fail to add will be written to the output file for examination. The
main use case here is where a small subset of a large set of tokens fails
to validate or add. Using the output file, the sysadmin can attempt to
recover these specific tokens.

This code is implemented as a server-side script. However, it doesn't
actually need to run on the server. This was done because importing is an
odd fit for the IPA command framework:
1. We need to write an output file.
2. The operation may be long-running (thousands of tokens).
3. Only admins need to perform this task and it only happens infrequently.

https://fedorahosted.org/freeipa/ticket/4261

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

1 files changed, 530 insertions, 0 deletions

diff --git a/ipaserver/install/ipa_otptoken_import.py b/ipaserver/install/ipa_otptoken_import.py
new file mode 100644
index 000000000..31a690201
--- /dev/null
+++ b/ipaserver/install/ipa_otptoken_import.py
@@ -0,0 +1,530 @@
+# Authors: Nathaniel McCallum <npmccallum@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/>.
+#
+
+import abc
+import base64
+import datetime
+import hashlib
+import hmac
+import os
+import uuid
+import struct
+
+from lxml import etree
+import dateutil.parser
+import dateutil.tz
+import nss.nss as nss
+import krbV
+
+from ipapython import admintool
+from ipalib import api, errors
+from ipaserver.plugins.ldap2 import ldap2
+
+
+class ValidationError(Exception):
+    pass
+
+
+def fetchAll(element, xpath, conv=lambda x: x):
+    return map(conv, element.xpath(xpath, namespaces={
+        "pskc": "urn:ietf:params:xml:ns:keyprov:pskc",
+        "xenc11": "http://www.w3.org/2009/xmlenc11#",
+        "xenc": "http://www.w3.org/2001/04/xmlenc#",
+        "ds": "http://www.w3.org/2000/09/xmldsig#",
+    }))
+
+
+def fetch(element, xpath, conv=lambda x: x, default=None):
+    result = fetchAll(element, xpath, conv)
+    return result[0] if result else default
+
+
+def convertDate(value):
+    "Converts an ISO 8601 string into a UTC datetime object."
+
+    dt = dateutil.parser.parse(value)
+
+    if dt.tzinfo is None:
+        dt = datetime.datetime(*dt.timetuple()[0:6],
+                               tzinfo=dateutil.tz.tzlocal())
+
+    return dt.astimezone(dateutil.tz.tzutc())
+
+
+def convertTokenType(value):
+    "Converts token algorithm URI to token type string."
+
+    return {
+        "urn:ietf:params:xml:ns:keyprov:pskc:hotp": u"hotp",
+        "urn:ietf:params:xml:ns:keyprov:pskc#hotp": u"hotp",
+        "urn:ietf:params:xml:ns:keyprov:pskc:totp": u"totp",
+        "urn:ietf:params:xml:ns:keyprov:pskc#totp": u"totp",
+    }.get(value.lower(), None)
+
+
+def convertHashName(value):
+    "Converts hash names to their canonical names."
+
+    return {
+        "sha1":    u"sha1",
+        "sha224":  u"sha224",
+        "sha256":  u"sha256",
+        "sha384":  u"sha384",
+        "sha512":  u"sha512",
+        "sha-1":   u"sha1",
+        "sha-224": u"sha224",
+        "sha-256": u"sha256",
+        "sha-384": u"sha384",
+        "sha-512": u"sha512",
+    }.get(value.lower(), u"sha1")
+
+
+def convertHMACType(value):
+    "Converts HMAC URI to hashlib object."
+
+    return {
+        "http://www.w3.org/2000/09/xmldsig#hmac-sha1":        hashlib.sha1,
+        "http://www.w3.org/2001/04/xmldsig-more#hmac-sha224": hashlib.sha224,
+        "http://www.w3.org/2001/04/xmldsig-more#hmac-sha256": hashlib.sha256,
+        "http://www.w3.org/2001/04/xmldsig-more#hmac-sha384": hashlib.sha384,
+        "http://www.w3.org/2001/04/xmldsig-more#hmac-sha512": hashlib.sha512,
+    }.get(value.lower(), hashlib.sha1)
+
+
+def convertAlgorithm(value):
+    "Converts encryption URI to (mech, ivlen)."
+
+    return {
+        "http://www.w3.org/2001/04/xmlenc#aes128-cbc":        (nss.CKM_AES_CBC_PAD, 128),
+        "http://www.w3.org/2001/04/xmlenc#aes192-cbc":        (nss.CKM_AES_CBC_PAD, 192),
+        "http://www.w3.org/2001/04/xmlenc#aes256-cbc":        (nss.CKM_AES_CBC_PAD, 256),
+        "http://www.w3.org/2001/04/xmlenc#tripledes-cbc":     (nss.CKM_DES3_CBC_PAD, 64),
+        "http://www.w3.org/2001/04/xmldsig-more#camellia128": (nss.CKM_CAMELLIA_CBC_PAD, 128),
+        "http://www.w3.org/2001/04/xmldsig-more#camellia192": (nss.CKM_CAMELLIA_CBC_PAD, 192),
+        "http://www.w3.org/2001/04/xmldsig-more#camellia256": (nss.CKM_CAMELLIA_CBC_PAD, 256),
+
+        # TODO: add support for these formats.
+        # "http://www.w3.org/2001/04/xmlenc#kw-aes128": "kw-aes128",
+        # "http://www.w3.org/2001/04/xmlenc#kw-aes192": "kw-aes192",
+        # "http://www.w3.org/2001/04/xmlenc#kw-aes256": "kw-aes256",
+        # "http://www.w3.org/2001/04/xmlenc#kw-tripledes": "kw-tripledes",
+        # "http://www.w3.org/2001/04/xmldsig-more#kw-camellia128": "kw-camellia128",
+        # "http://www.w3.org/2001/04/xmldsig-more#kw-camellia192": "kw-camellia192",
+        # "http://www.w3.org/2001/04/xmldsig-more#kw-camellia256": "kw-camellia256",
+    }.get(value.lower(), (None, None))
+
+
+def convertEncrypted(value, decryptor=None, pconv=base64.b64decode, econv=lambda x: x):
+    "Converts a value element, decrypting if necessary. See RFC 6030."
+
+    v = fetch(value, "./pskc:PlainValue/text()", pconv)
+    if v is not None:
+        return v
+
+    mac = fetch(value, "./pskc:ValueMAC/text()", base64.b64decode)
+    ev = fetch(value, "./pskc:EncryptedValue")
+    if ev is not None and decryptor is not None:
+        return econv(decryptor(ev, mac))
+
+    return None
+
+
+class XMLKeyDerivation(object):
+    "Interface for XML Encryption 1.1 key derivation."
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def __init__(self, enckey):
+        "Sets up key derivation parameters from the parent XML entity."
+
+    @abc.abstractmethod
+    def derive(self, masterkey):
+        "Derives a key from the master key."
+
+
+class PBKDF2KeyDerivation(XMLKeyDerivation):
+    def __init__(self, enckey):
+        params = fetch(enckey, "./xenc11:DerivedKey/xenc11:KeyDerivationMethod/xenc11:PBKDF2-params")
+        if params is None:
+            raise ValueError("XML file is missing PBKDF2 parameters!")
+
+        self.salt = fetch(params, "./xenc11:Salt/xenc11:Specified/text()", base64.b64decode)
+        self.iter = fetch(params, "./xenc11:IterationCount/text()", int)
+        self.klen = fetch(params, "./xenc11:KeyLength/text()", int)
+        self.hmod = fetch(params, "./xenc11:PRF/@Algorithm", convertHMACType, hashlib.sha1)
+
+        if self.salt is None:
+            raise ValueError("XML file is missing PBKDF2 salt!")
+
+        if self.iter is None:
+            raise ValueError("XML file is missing PBKDF2 iteration count!")
+
+        if self.klen is None:
+            raise ValueError("XML file is missing PBKDF2 key length!")
+
+    def derive(self, masterkey):
+        mac = hmac.HMAC(masterkey, None, self.hmod)
+
+        # Figure out how many blocks we will have to combine
+        # to expand the master key to the desired length.
+        blocks = self.klen // mac.digest_size
+        if self.klen % mac.digest_size != 0:
+            blocks += 1
+
+        # Loop through each block adding it to the derived key.
+        dk = []
+        for i in xrange(1, blocks + 1):
+            # Set initial values.
+            last = self.salt + struct.pack('>I', i)
+            hash = [0] * mac.digest_size
+
+            # Perform n iterations.
+            for j in xrange(self.iter):
+                tmp = mac.copy()
+                tmp.update(last)
+                last = tmp.digest()
+
+                # XOR the previous hash with the new hash.
+                for k in xrange(mac.digest_size):
+                    hash[k] ^= ord(last[k])
+
+            # Add block to derived key.
+            dk.extend(hash)
+
+        return ''.join([chr(c) for c in dk])[:self.klen]
+
+
+def convertKeyDerivation(value):
+    "Converts key derivation URI to a BaseKeyDerivation class."
+
+    return {
+        "http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#pbkdf2": PBKDF2KeyDerivation,
+    }.get(value.lower(), None)
+
+
+class XMLDecryptor(object):
+    """This decrypts values from XML as specified in:
+        * http://www.w3.org/TR/xmlenc-core/
+        * RFC 6931"""
+
+    def __init__(self, key, hmac=None):
+        self.__key = nss.SecItem(key)
+        self.__hmac = hmac
+
+    def __call__(self, element, mac=None):
+        (mech, ivlen) = fetch(element, "./xenc:EncryptionMethod/@Algorithm", convertAlgorithm)
+        data = fetch(element, "./xenc:CipherData/xenc:CipherValue/text()", base64.b64decode)
+
+        # If a MAC is present, perform validation.
+        if mac:
+            tmp = self.__hmac.copy()
+            tmp.update(data)
+            if tmp.digest() != mac:
+                raise ValidationError("MAC validation failed!")
+
+        # Decrypt the data.
+        slot = nss.get_best_slot(mech)
+        key = nss.import_sym_key(slot, mech, nss.PK11_OriginUnwrap, nss.CKA_ENCRYPT, self.__key)
+        iv = nss.param_from_iv(mech, nss.SecItem(data[0:ivlen/8]))
+        ctx = nss.create_context_by_sym_key(mech, nss.CKA_DECRYPT, key, iv)
+        out = ctx.cipher_op(data[ivlen / 8:])
+        out += ctx.digest_final()
+        return out
+
+
+class PSKCKeyPackage(object):
+    _XML = {
+        'pskc:DeviceInfo': {
+            'pskc:IssueNo/text()':      ('issueno',      unicode),
+            'pskc:ExpiryDate/text()':   ('notafter.hw',  convertDate),
+            'pskc:Manufacturer/text()': ('vendor',       unicode),
+            'pskc:Model/text()':        ('model',        unicode),
+            'pskc:SerialNo/text()':     ('serial',       unicode),
+            'pskc:StartDate/text()':    ('notbefore.hw', convertDate),
+            'pskc:UserId/text()':       ('owner',        unicode),
+        },
+
+        'pskc:Key': {
+            '@Algorithm':               ('type',        convertTokenType),
+            '@Id':                      ('id',          unicode),
+            'pskc:FriendlyName/text()': ('description', unicode),
+            'pskc:Issuer/text()':       ('issuer',      unicode),
+            'pskc:KeyReference/text()': ('keyref',      unicode),
+
+            'pskc:AlgorithmParameters': {
+                'pskc:Suite/text()':               ('algorithm',  convertHashName),
+                'pskc:ResponseFormat/@CheckDigit': ('checkdigit', unicode),
+                'pskc:ResponseFormat/@Encoding':   ('encoding',   unicode),
+                'pskc:ResponseFormat/@Length':     ('digits',     int),
+            },
+
+            'pskc:Data': {
+                'pskc:Counter':      ('counter',  lambda v, d: convertEncrypted(v, d, long, long)),
+                'pskc:Secret':       ('key',      convertEncrypted),
+                'pskc:Time':         ('time',     lambda v, d: convertEncrypted(v, d, int, int)),
+                'pskc:TimeDrift':    ('offset',   lambda v, d: convertEncrypted(v, d, int, int)),
+                'pskc:TimeInterval': ('interval', lambda v, d: convertEncrypted(v, d, int, int)),
+            },
+
+            'pskc:Policy': {
+                'pskc:ExpiryDate/text()':    ('notafter.sw',  convertDate),
+                'pskc:KeyUsage/text()':      ('keyusage',     unicode),
+                'pskc:NumberOfTransactions': ('maxtransact',  lambda v: v),
+                'pskc:PINPolicy':            ('pinpolicy',    lambda v: v),
+                'pskc:StartDate/text()':     ('notbefore.sw', convertDate),
+            },
+        },
+    }
+
+    _MAP = (
+        ('type',        'type',                    lambda v, o: v.strip()),
+        ('description', 'description',             lambda v, o: v.strip()),
+        ('vendor',      'ipatokenvendor',          lambda v, o: v.strip()),
+        ('model',       'ipatokenmodel',           lambda v, o: v.strip()),
+        ('serial',      'ipatokenserial',          lambda v, o: v.strip()),
+        ('issueno',     'ipatokenserial',          lambda v, o: o.get('ipatokenserial', '') + '-' + v.strip()),
+        ('key',         'ipatokenotpkey',          lambda v, o: unicode(base64.b32encode(v))),
+        ('digits',      'ipatokenotpdigits',       lambda v, o: v),
+        ('algorithm',   'ipatokenotpalgorithm',    lambda v, o: v),
+        ('counter',     'ipatokenhotpcounter',     lambda v, o: v),
+        ('interval',    'ipatokentotptimestep',    lambda v, o: v),
+        ('offset',      'ipatokentotpclockoffset', lambda v, o: o.get('ipatokentotptimestep', 30) * v),
+    )
+
+    def __init__(self, element, decryptor):
+        self.__element = element
+        self.__decryptor = decryptor
+        self.__id = None
+        self.__options = None
+
+    @property
+    def id(self):
+        if self.__id is None:
+            self.__process()
+
+        return self.__id
+
+    @property
+    def options(self):
+        if self.__options is None:
+            self.__process()
+
+        return self.__options
+
+    def remove(self):
+        self.__element.getparent().remove(self.__element)
+
+    def __process(self):
+        # Parse and validate.
+        data = self.__parse(self.__decryptor, self.__element, ".", self._XML)
+        self.__validate(data)
+
+        # Copy values into output.
+        options = {}
+        for (dk, ok, f) in self._MAP:
+            if dk in data:
+                options[ok] = f(data[dk], options)
+
+        # Copy validity dates.
+        self.__dates(options, data, 'notbefore', max)
+        self.__dates(options, data, 'notafter', min)
+
+        # Save attributes.
+        self.__options = options
+        self.__id = data.get('id', uuid.uuid4())
+
+    def __parse(self, decryptor, element, prefix, table):
+        "Recursively parses the xml from a table."
+
+        data = {}
+        for k, v in table.items():
+            path = prefix + "/" + k
+
+            if isinstance(v, dict):
+                data.update(self.__parse(decryptor, element, path, v))
+                continue
+
+            result = fetch(element, path)
+            if result is not None:
+                if getattr(getattr(v[1], "func_code", None), "co_argcount", 0) > 1:
+                    data[v[0]] = v[1](result, decryptor)
+                else:
+                    data[v[0]] = v[1](result)
+
+        return data
+
+    def __validate(self, data):
+        "Validates the parsed data."
+
+        if 'type' not in data or data['type'] not in ('totp', 'hotp'):
+            raise ValidationError("Unsupported token type!")
+
+        if 'key' not in data:
+            if 'keyref' in data:
+                raise ValidationError("Referenced keys are not supported!")
+            raise ValidationError("Key not found in token!")
+
+        if data.get('checkdigit', 'FALSE').upper() != 'FALSE':
+            raise ValidationError("CheckDigit not supported!")
+
+        if data.get('maxtransact', None) is not None:
+            raise ValidationError('NumberOfTransactions policy not supported!')
+
+        if data.get('pinpolicy', None) is not None:
+            raise ValidationError('PINPolicy policy not supported!')
+
+        if data.get('time', 0) != 0:
+            raise ValidationError('Specified time is not supported!')
+
+        encoding = data.get('encoding', 'DECIMAL').upper()
+        if encoding != 'DECIMAL':
+            raise ValidationError('Unsupported encoding: %s!' % encoding)
+
+        usage = data.get('keyusage', 'OTP')
+        if usage != 'OTP':
+            raise ValidationError('Unsupported key usage: %s' % usage)
+
+    def __dates(self, out, data, key, reducer):
+        dates = (data.get(key + '.sw', None), data.get(key + '.hw', None))
+        dates = filter(lambda x: x is not None, dates)
+        if dates:
+            out['ipatoken' + key] = unicode(reducer(dates).strftime("%Y%m%d%H%M%SZ"))
+
+
+class PSKCDocument(object):
+    @property
+    def keyname(self):
+        return self.__keyname
+
+    def __init__(self, filename):
+        self.__keyname = None
+        self.__decryptor = None
+        self.__doc = etree.parse(filename)
+        self.__mkey = fetch(self.__doc, "./pskc:MACMethod/pskc:MACKey")
+        self.__algo = fetch(self.__doc, "./pskc:MACMethod/@Algorithm", convertHMACType)
+
+        self.__keypackages = fetchAll(self.__doc, "./pskc:KeyPackage")
+        if not self.__keypackages:
+            raise ValueError("PSKC file is invalid!")
+
+        self.__enckey = fetch(self.__doc, "./pskc:EncryptionKey")
+        if self.__enckey is not None:
+            # Check for x509 key.
+            x509key = fetch(self.__enckey, "./ds:X509Data")
+            if x509key is not None:
+                raise NotImplementedError("X.509 keys are not currently supported!")
+
+            # Get the keyname.
+            self.__keyname = fetch(self.__enckey, "./ds:KeyName/text()")
+            if self.__keyname is None:
+                self.__keyname = fetch(self.__enckey,
+                                       "./xenc11:DerivedKey/xenc11:MasterKeyName/text()")
+
+    def setKey(self, key):
+        # Derive the enckey if required.
+        kd = fetch(self.__enckey,
+                   "./xenc11:DerivedKey/xenc11:KeyDerivationMethod/@Algorithm",
+                   convertKeyDerivation)
+        if kd is not None:
+            key = kd(self.__enckey).derive(key)
+
+        # Load the decryptor.
+        self.__decryptor = XMLDecryptor(key)
+        if self.__mkey is not None and self.__algo is not None:
+            tmp = hmac.HMAC(self.__decryptor(self.__mkey), digestmod=self.__algo)
+            self.__decryptor = XMLDecryptor(key, tmp)
+
+    def getKeyPackages(self):
+        for kp in self.__keypackages:
+            yield PSKCKeyPackage(kp, self.__decryptor)
+
+    def save(self, dest):
+        self.__doc.write(dest)
+
+
+class OTPTokenImport(admintool.AdminTool):
+    command_name = 'ipa-otptoken-import'
+    description = "Import OTP tokens."
+    usage = "%prog [options] <PSKC file> <output file>"
+
+    @classmethod
+    def main(cls, argv):
+        nss.nss_init_nodb()
+        try:
+            super(OTPTokenImport, cls).main(argv)
+        finally:
+            nss.nss_shutdown()
+
+    @classmethod
+    def add_options(cls, parser):
+        super(OTPTokenImport, cls).add_options(parser)
+
+        parser.add_option("-k", "--keyfile", dest="keyfile",
+                          help="File containing the key used to decrypt token secrets")
+
+    def validate_options(self):
+        super(OTPTokenImport, self).validate_options()
+
+        # Parse the file.
+        if len(self.args) < 1:
+            raise admintool.ScriptError("Import file required!")
+        self.doc = PSKCDocument(self.args[0])
+
+        # Get the output file.
+        if len(self.args) < 2:
+            raise admintool.ScriptError("Output file required!")
+        self.output = self.args[1]
+        if os.path.exists(self.output):
+            raise admintool.ScriptError("Output file already exists!")
+
+        # Verify a key is provided if one is needed.
+        if self.doc.keyname is not None:
+            if self.safe_options.keyfile is None:
+                raise admintool.ScriptError("Encryption key required: %s!" % self.doc.keyname)
+
+            # Load the keyfile.
+            with open(self.safe_options.keyfile) as f:
+                self.doc.setKey(f.read())
+
+    def run(self):
+        api.bootstrap(in_server=True)
+        api.finalize()
+
+        conn = ldap2()
+        try:
+            ccache = krbV.default_context().default_ccache()
+            conn.connect(ccache=ccache)
+        except (krbV.Krb5Error, errors.ACIError):
+            raise admintool.ScriptError("Unable to connect to LDAP! Did you kinit?")
+
+        try:
+            # Parse tokens
+            for keypkg in self.doc.getKeyPackages():
+                try:
+                    api.Command.otptoken_add(keypkg.id, **keypkg.options)
+                except Exception as e:
+                    self.log.warn("Error adding token: %s", e)
+                else:
+                    self.log.info("Added token: %s", keypkg.id)
+                    keypkg.remove()
+        finally:
+            conn.disconnect()
+
+        # Write out the XML file without the tokens that succeeded.
+        self.doc.save(self.output)