# $Id$
#
# Copyright (C) 2014  Dragon Research Labs ("DRL")
# Portions copyright (C) 2009--2013  Internet Systems Consortium ("ISC")
# Portions copyright (C) 2007--2008  American Registry for Internet Numbers ("ARIN")
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notices and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND DRL, ISC, AND ARIN DISCLAIM ALL
# WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL DRL,
# ISC, OR ARIN BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""
One X.509 implementation to rule them all...

...and in the darkness hide the twisty maze of partially-overlapping
X.509 support packages in Python.

Once upon a time we were using four separate partially-overlapping
implementions of X.509 and related protocols.  Over the years this has
collapsed down to one, but the interface module we built on top of the
previous mess has itself become heavily embedded in the code base.  So
this is a bit more complicated (not to mention baroque) than one might
expect for a module that had grown in a saner fashion.  We clean up
bits of it from time to time.  Some day this may all make sense.
"""

import rpki.POW
import base64
import lxml.etree
import os
import subprocess
import email.mime.application
import email.utils
import logging
import mailbox
import time
import rpki.exceptions
import rpki.resource_set
import rpki.oids
import rpki.sundial
import rpki.log
import rpki.relaxng

logger = logging.getLogger(__name__)

def base64_with_linebreaks(der):
    """
    Encode DER (really, anything) as Base64 text, with linebreaks to
    keep the result (sort of) readable.
    """

    b = base64.b64encode(der)
    n = len(b)
    return "\n" + "\n".join(b[i : min(i + 64, n)] for i in xrange(0, n, 64)) + "\n"

def looks_like_PEM(text):
    """
    Guess whether text looks like a PEM encoding.
    """

    i = text.find("-----BEGIN ")
    return i >= 0 and text.find("\n-----END ", i) > i

def first_uri_matching_prefix(xia, prefix):
    """
    Find first URI in a sequence of AIA or SIA URIs which matches a
    particular prefix string.  Returns the URI if found, otherwise None.
    """

    if xia is not None:
        for uri in xia:
            if uri.startswith(prefix):
                return uri
    return None

def first_rsync_uri(xia):
    """
    Find first rsync URI in a sequence of AIA or SIA URIs.
    Returns the URI if found, otherwise None.
    """

    return first_uri_matching_prefix(xia, "rsync://")

def first_http_uri(xia):
    """
    Find first HTTP URI in a sequence of AIA or SIA URIs.
    Returns the URI if found, otherwise None.
    """

    return first_uri_matching_prefix(xia, "http://")

def first_https_uri(xia):
    """
    Find first HTTPS URI in a sequence of AIA or SIA URIs.
    Returns the URI if found, otherwise None.
    """

    return first_uri_matching_prefix(xia, "https://")

def sha1(data):
    """
    Calculate SHA-1 digest of some data.
    Convenience wrapper around rpki.POW.Digest class.
    """

    d = rpki.POW.Digest(rpki.POW.SHA1_DIGEST)
    d.update(data)
    return d.digest()

def sha256(data):
    """
    Calculate SHA-256 digest of some data.
    Convenience wrapper around rpki.POW.Digest class.
    """

    d = rpki.POW.Digest(rpki.POW.SHA256_DIGEST)
    d.update(data)
    return d.digest()


class X501DN(object):
    """
    Class to hold an X.501 Distinguished Name.

    This is nothing like a complete implementation, just enough for our
    purposes.  See RFC 5280 4.1.2.4 for the ASN.1 details.  In brief:

      - A DN is a SEQUENCE OF RDNs.

      - A RDN is a SET OF AttributeAndValues; in practice, multi-value
        RDNs are rare, so an RDN is almost always a set with a single
        element.

      - An AttributeAndValue is a SEQUENCE consisting of a OID and a
        value, where a whole bunch of things including both syntax and
        semantics of the value are determined by the OID.

      - The value is some kind of ASN.1 string; there are far too many
        encoding options options, most of which are either strongly
        discouraged or outright forbidden by the PKIX profile, but which
        persist for historical reasons.  The only ones PKIX actually
        likes are PrintableString and UTF8String, but there are nuances
        and special cases where some of the others are required.

    The RPKI profile further restricts DNs to a single mandatory
    CommonName attribute with a single optional SerialNumber attribute
    (not to be confused with the certificate serial number).

    BPKI certificates should (we hope) follow the general PKIX guideline
    but the ones we construct ourselves are likely to be relatively
    simple.
    """

    def __init__(self, dn):
        assert isinstance(dn, tuple)
        self.dn = dn

    def __str__(self):
        return "".join("/" + "+".join("%s=%s" % (rpki.oids.oid2name(a[0]), a[1])
                                      for a in rdn)
                       for rdn in self.dn)

    def __cmp__(self, other):
        return cmp(self.dn, other.dn)

    def __repr__(self):
        return rpki.log.log_repr(self, str(self))

    def _debug(self):
        logger.debug("++ %r %r", self, self.dn)

    @classmethod
    def from_cn(cls, cn, sn = None):
        assert isinstance(cn, (str, unicode))
        if isinstance(sn, (int, long)):
            sn = "%08X" % sn
        elif isinstance(sn, (str, unicode)):
            assert all(c in "0123456789abcdefABCDEF" for c in sn)
            sn = str(sn)
        if sn is not None:
            dn = (((rpki.oids.commonName, cn),), ((rpki.oids.serialNumber, sn),))
        else:
            dn = (((rpki.oids.commonName, cn),),)
        return cls(dn)

    @classmethod
    def from_POW(cls, dn):
        return cls(dn)

    def get_POW(self):
        return self.dn

    def extract_cn_and_sn(self):
        cn = None
        sn = None

        for rdn in self.dn:
            if len(rdn) == 1 and len(rdn[0]) == 2:
                oid = rdn[0][0]
                val = rdn[0][1]
                if oid == rpki.oids.commonName and cn is None:
                    cn = val
                    continue
                if oid == rpki.oids.serialNumber and sn is None:
                    sn = val
                    continue
            raise rpki.exceptions.BadX510DN("Bad subject name: %s" % (self.dn,))

        if cn is None:
            raise rpki.exceptions.BadX510DN("Subject name is missing CN: %s" % (self.dn,))

        return cn, sn


class DER_object(object):
    """
    Virtual class to hold a generic DER object.
    """

    ## @var formats
    # Formats supported in this object.  This is kind of redundant now
    # that we're down to a single ASN.1 package and everything supports
    # the same DER and POW formats, it's mostly historical baggage from
    # the days when we had three different ASN.1 encoders, each with its
    # own low-level Python object format.  Clean up, some day.
    formats = ("DER", "POW")

    ## @var POW_class
    # Class of underlying POW object.  Concrete subclasses must supply this.
    POW_class = None

    ## Other attributes that self.clear() should whack.
    other_clear = ()

    ## @var DER
    # DER value of this object
    DER = None

    ## @var failure_threshold
    # Rate-limiting interval between whines about Auto_update objects.
    failure_threshold = rpki.sundial.timedelta(minutes = 5)

    def empty(self):
        """
        Test whether this object is empty.
        """

        return all(getattr(self, a, None) is None for a in self.formats)

    def clear(self):
        """
        Make this object empty.
        """

        for a in self.formats + self.other_clear:
            setattr(self, a, None)
        self.filename = None
        self.timestamp = None
        self.lastfail = None

    def __init__(self, **kw):
        """
        Initialize a DER_object.
        """

        self.clear()
        if len(kw):
            self.set(**kw)

    def set(self, **kw):
        """
        Set this object by setting one of its known formats.

        This method only allows one to set one format at a time.
        Subsequent calls will clear the object first.  The point of all
        this is to let the object's internal converters handle mustering
        the object into whatever format you need at the moment.
        """

        if len(kw) == 1:
            name = kw.keys()[0]
            if name in self.formats:
                self.clear()
                setattr(self, name, kw[name])
                return
            if name == "PEM":
                self.clear()
                self._set_PEM(kw[name])
                return
            if name == "Base64":
                self.clear()
                self.DER = base64.b64decode(kw[name])
                return
            if name == "Auto_update":
                self.filename = kw[name]
                self.check_auto_update()
                return
            if name in ("PEM_file", "DER_file", "Auto_file"):
                f = open(kw[name], "rb")
                value = f.read()
                f.close()
                self.clear()
                if name == "PEM_file" or (name == "Auto_file" and looks_like_PEM(value)):
                    self._set_PEM(value)
                else:
                    self.DER = value
                return
        raise rpki.exceptions.DERObjectConversionError("Can't honor conversion request %r" % (kw,))

    def check_auto_update(self):
        """
        Check for updates to a DER object that auto-updates from a file.
        """

        # pylint: disable=W0201

        if self.filename is None:
            return
        try:
            filename = self.filename
            timestamp = os.stat(self.filename).st_mtime
            if self.timestamp is None or self.timestamp < timestamp:
                logger.debug("Updating %s, timestamp %s",
                             filename, rpki.sundial.datetime.fromtimestamp(timestamp))
                f = open(filename, "rb")
                value = f.read()
                f.close()
                self.clear()
                if looks_like_PEM(value):
                    self._set_PEM(value)
                else:
                    self.DER = value
                self.filename = filename
                self.timestamp = timestamp
        except (IOError, OSError), e:
            now = rpki.sundial.now()
            if self.lastfail is None or now > self.lastfail + self.failure_threshold:
                logger.warning("Could not auto_update %r (last failure %s): %s", self, self.lastfail, e)
            self.lastfail = now
        else:
            self.lastfail = None

    @property
    def mtime(self):
        """
        Retrieve os.stat().st_mtime for auto-update files.
        """

        return os.stat(self.filename).st_mtime

    def check(self):
        """
        Perform basic checks on a DER object.
        """

        self.check_auto_update()
        assert not self.empty()

    def _set_PEM(self, pem):
        """
        Set the POW value of this object based on a PEM input value.
        Subclasses may need to override this.
        """

        # pylint: disable=W0201
        assert self.empty()
        self.POW = self.POW_class.pemRead(pem)

    def get_DER(self):
        """
        Get the DER value of this object.
        Subclasses may need to override this method.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWrite()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this object.
        Subclasses may need to override this method.
        """

        # pylint: disable=E0203,W0201
        self.check()
        if not self.POW:
            self.POW = self.POW_class.derRead(self.get_DER())
        return self.POW

    def get_Base64(self):
        """
        Get the Base64 encoding of the DER value of this object.
        """

        return base64_with_linebreaks(self.get_DER())

    def get_PEM(self):
        """
        Get the PEM representation of this object.
        """

        return self.get_POW().pemWrite()

    def __cmp__(self, other):
        """
        Compare two DER-encoded objects.
        """

        if self is None and other is None:
            return 0
        elif self is None:
            return -1
        elif other is None:
            return 1
        elif isinstance(other, str):
            return cmp(self.get_DER(), other)
        else:
            return cmp(self.get_DER(), other.get_DER())

    def hSKI(self):
        """
        Return hexadecimal string representation of SKI for this object.
        Only work for subclasses that implement get_SKI().
        """

        ski = self.get_SKI()
        return ":".join(("%02X" % ord(i) for i in ski)) if ski else ""

    def gSKI(self):
        """
        Calculate g(SKI) for this object.  Only work for subclasses
        that implement get_SKI().
        """

        return base64.urlsafe_b64encode(self.get_SKI()).rstrip("=")

    def hAKI(self):
        """
        Return hexadecimal string representation of AKI for this
        object.  Only work for subclasses that implement get_AKI().
        """

        aki = self.get_AKI()
        return ":".join(("%02X" % ord(i) for i in aki)) if aki else ""

    def gAKI(self):
        """
        Calculate g(AKI) for this object.  Only work for subclasses
        that implement get_AKI().
        """

        return base64.urlsafe_b64encode(self.get_AKI()).rstrip("=")

    def get_AKI(self):
        """
        Get the AKI extension from this object, if supported.
        """

        return self.get_POW().getAKI()

    def get_SKI(self):
        """
        Get the SKI extension from this object, if supported.
        """

        return self.get_POW().getSKI()

    def get_EKU(self):
        """
        Get the Extended Key Usage extension from this object, if supported.
        """

        return self.get_POW().getEKU()

    def get_SIA(self):
        """
        Get the SIA extension from this object.  Only works for subclasses
        that support getSIA().
        """

        return self.get_POW().getSIA()

    def get_sia_directory_uri(self):
        """
        Get SIA directory (id-ad-caRepository) URI from this object.
        Only works for subclasses that support getSIA().
        """

        sia = self.get_POW().getSIA()
        return None if sia is None else first_rsync_uri(sia[0])

    def get_sia_manifest_uri(self):
        """
        Get SIA manifest (id-ad-rpkiManifest) URI from this object.
        Only works for subclasses that support getSIA().
        """

        sia = self.get_POW().getSIA()
        return None if sia is None else first_rsync_uri(sia[1])

    def get_sia_object_uri(self):
        """
        Get SIA object (id-ad-signedObject) URI from this object.
        Only works for subclasses that support getSIA().
        """

        sia = self.get_POW().getSIA()
        return None if sia is None else first_rsync_uri(sia[2])

    def get_sia_rrdp_notify(self):
        """
        Get SIA RRDP (id-ad-rpkiNotify) URI from this object.
        We prefer HTTPS over HTTP if both are present.
        Only works for subclasses that support getSIA().
        """

        sia = self.get_POW().getSIA()
        return None if sia is None else first_https_uri(sia[3]) or first_http_uri(sia[3])

    def get_AIA(self):
        """
        Get the SIA extension from this object.  Only works for subclasses
        that support getAIA().
        """

        return self.get_POW().getAIA()

    def get_aia_uri(self):
        """
        Get AIA (id-ad-caIssuers) URI from this object.
        Only works for subclasses that support getAIA().
        """

        return first_rsync_uri(self.get_POW().getAIA())

    def get_basicConstraints(self):
        """
        Get the basicConstraints extension from this object.  Only works
        for subclasses that support getExtension().
        """

        return self.get_POW().getBasicConstraints()

    def is_CA(self):
        """
        Return True if and only if object has the basicConstraints
        extension and its cA value is true.
        """

        basicConstraints = self.get_basicConstraints()
        return basicConstraints is not None and basicConstraints[0]

    def get_3779resources(self):
        """
        Get RFC 3779 resources as rpki.resource_set objects.
        """

        resources = rpki.resource_set.resource_bag.from_POW_rfc3779(self.get_POW().getRFC3779())
        try:
            resources.valid_until = self.getNotAfter()          # pylint: disable=E1101
        except AttributeError:
            pass
        return resources

    @classmethod
    def from_sql(cls, x):
        """
        Convert from SQL storage format.
        """

        return cls(DER = x)

    def to_sql(self):
        """
        Convert to SQL storage format.
        """

        return self.get_DER()

    def dumpasn1(self):
        """
        Pretty print an ASN.1 DER object using cryptlib dumpasn1 tool.
        Use a temporary file rather than popen4() because dumpasn1 uses
        seek() when decoding ASN.1 content nested in OCTET STRING values.
        """

        ret = None
        fn = "dumpasn1.%d.tmp" % os.getpid()
        try:
            f = open(fn, "wb")
            f.write(self.get_DER())
            f.close()
            p = subprocess.Popen(("dumpasn1", "-a", fn), stdout = subprocess.PIPE, stderr = subprocess.STDOUT)
            ret = "\n".join(x for x in p.communicate()[0].splitlines() if x.startswith(" "))
        except Exception, e:
            ret = "[Could not run dumpasn1: %s]" % e
        finally:
            os.unlink(fn)
        return ret

    def tracking_data(self, uri):
        """
        Return a string containing data we want to log when tracking how
        objects move through the RPKI system.  Subclasses may wrap this to
        provide more information, but should make sure to include at least
        this information at the start of the tracking line.
        """

        # pylint: disable=E1101

        try:
            return "%s %s %s" % (uri, self.creation_timestamp, "".join(("%02X" % ord(b) for b in sha1(self.get_DER()))))
        except:
            return uri

    def __getstate__(self):
        """
        Pickling protocol -- pickle the DER encoding.
        """

        return self.get_DER()

    def __setstate__(self, state):
        """
        Pickling protocol -- unpickle the DER encoding.
        """

        self.set(DER = state)

class X509(DER_object):
    """
    X.509 certificates.

    This class is designed to hold all the different representations of
    X.509 certs we're using and convert between them.  X.509 support in
    Python a nasty maze of half-cooked stuff (except perhaps for
    cryptlib, which is just different).  Users of this module should not
    have to care about this implementation nightmare.
    """

    POW_class = rpki.POW.X509

    def getIssuer(self):
        """
        Get the issuer of this certificate.
        """

        return X501DN.from_POW(self.get_POW().getIssuer())

    def getSubject(self):
        """
        Get the subject of this certificate.
        """

        return X501DN.from_POW(self.get_POW().getSubject())

    def getNotBefore(self):
        """
        Get the inception time of this certificate.
        """

        return self.get_POW().getNotBefore()

    def getNotAfter(self):
        """
        Get the expiration time of this certificate.
        """

        return self.get_POW().getNotAfter()

    def getSerial(self):
        """
        Get the serial number of this certificate.
        """

        return self.get_POW().getSerial()

    def getPublicKey(self):
        """
        Extract the public key from this certificate.
        """

        return PublicKey(POW = self.get_POW().getPublicKey())

    def get_SKI(self):
        """
        Get the SKI extension from this object.
        """

        return self.get_POW().getSKI()

    def expired(self):
        """
        Test whether this certificate has expired.
        """

        return self.getNotAfter() <= rpki.sundial.now()

    def issue(self, keypair, subject_key, serial, sia, aia, crldp, notAfter,
              cn = None, resources = None, is_ca = True, notBefore = None,
              sn = None, eku = None):
        """
        Issue an RPKI certificate.
        """

        assert aia is not None and crldp is not None

        assert eku is None or not is_ca

        return self._issue(
            keypair     = keypair,
            subject_key = subject_key,
            serial      = serial,
            sia         = sia,
            aia         = aia,
            crldp       = crldp,
            notBefore   = notBefore,
            notAfter    = notAfter,
            cn          = cn,
            sn          = sn,
            resources   = resources,
            is_ca       = is_ca,
            aki         = self.get_SKI(),
            issuer_name = self.getSubject(),
            eku         = eku)


    @classmethod
    def self_certify(cls, keypair, subject_key, serial, sia, notAfter,
                     cn = None, resources = None, notBefore = None,
                     sn = None):
        """
        Generate a self-certified RPKI certificate.
        """

        ski = subject_key.get_SKI()

        if cn is None:
            cn = "".join(("%02X" % ord(i) for i in ski))

        return cls._issue(
            keypair     = keypair,
            subject_key = subject_key,
            serial      = serial,
            sia         = sia,
            aia         = None,
            crldp       = None,
            notBefore   = notBefore,
            notAfter    = notAfter,
            cn          = cn,
            sn          = sn,
            resources   = resources,
            is_ca       = True,
            aki         = ski,
            issuer_name = X501DN.from_cn(cn, sn),
            eku         = None)


    @classmethod
    def _issue(cls, keypair, subject_key, serial, sia, aia, crldp, notAfter,
               cn, sn, resources, is_ca, aki, issuer_name, notBefore, eku):
        """
        Common code to issue an RPKI certificate.
        """

        if sia is not None:
            assert len(sia) == 4 and sia[3]
            sia = tuple((str(s),) if isinstance(s, (str, unicode)) else s for s in sia)

        now = rpki.sundial.now()
        ski = subject_key.get_SKI()

        if notBefore is None:
            notBefore = now

        if cn is None:
            cn = "".join(("%02X" % ord(i) for i in ski))

        if now >= notAfter:
            raise rpki.exceptions.PastNotAfter("notAfter value %s is already in the past" % notAfter)

        if notBefore >= notAfter:
            raise rpki.exceptions.NullValidityInterval("notAfter value %s predates notBefore value %s" %
                                                       (notAfter, notBefore))

        cert = rpki.POW.X509()

        cert.setVersion(2)
        cert.setSerial(serial)
        cert.setIssuer(issuer_name.get_POW())
        cert.setSubject(X501DN.from_cn(cn, sn).get_POW())
        cert.setNotBefore(notBefore)
        cert.setNotAfter(notAfter)
        cert.setPublicKey(subject_key.get_POW())
        cert.setSKI(ski)
        cert.setAKI(aki)
        cert.setCertificatePolicies((rpki.oids.id_cp_ipAddr_asNumber,))

        if crldp is not None:
            cert.setCRLDP((crldp,))

        if aia is not None:
            cert.setAIA((aia,))

        if is_ca:
            cert.setBasicConstraints(True, None)
            cert.setKeyUsage(frozenset(("keyCertSign", "cRLSign")))

        else:
            cert.setKeyUsage(frozenset(("digitalSignature",)))

        assert sia is not None or not is_ca

        if sia is not None:
            caRepository, rpkiManifest, signedObject, rpkiNotify = sia
            cert.setSIA(
                (caRepository,) if isinstance(caRepository, str) else caRepository,
                (rpkiManifest,) if isinstance(rpkiManifest, str) else rpkiManifest,
                (signedObject,) if isinstance(signedObject, str) else signedObject,
                (rpkiNotify,)   if isinstance(rpkiNotify, str)   else rpkiNotify)

        if resources is not None:
            cert.setRFC3779(
                asn  = ("inherit" if resources.asn.inherit else
                        ((r.min, r.max) for r in resources.asn)),
                ipv4 = ("inherit" if resources.v4.inherit else
                        ((r.min, r.max) for r in resources.v4)),
                ipv6 = ("inherit" if resources.v6.inherit else
                        ((r.min, r.max) for r in resources.v6)))

        if eku is not None:
            assert not is_ca
            cert.setEKU(eku)

        cert.sign(keypair.get_POW(), rpki.POW.SHA256_DIGEST)

        return cls(POW = cert)

    def bpki_cross_certify(self, keypair, source_cert, serial, notAfter,
                           now = None, pathLenConstraint = 0):
        """
        Issue a BPKI certificate with values taking from an existing certificate.
        """

        return self.bpki_certify(
            keypair      = keypair,
            subject_name = source_cert.getSubject(),
            subject_key  = source_cert.getPublicKey(),
            serial       = serial,
            notAfter     = notAfter,
            now          = now,
            pathLenConstraint = pathLenConstraint,
            is_ca        = True)

    @classmethod
    def bpki_self_certify(cls, keypair, subject_name, serial, notAfter,
                          now = None, pathLenConstraint = None):
        """
        Issue a self-signed BPKI CA certificate.
        """

        return cls._bpki_certify(
            keypair      = keypair,
            issuer_name  = subject_name,
            subject_name = subject_name,
            subject_key  = keypair.get_public(),
            serial       = serial,
            now          = now,
            notAfter     = notAfter,
            pathLenConstraint = pathLenConstraint,
            is_ca        = True)

    def bpki_certify(self, keypair, subject_name, subject_key, serial, notAfter, is_ca,
                     now = None, pathLenConstraint = None):
        """
        Issue a normal BPKI certificate.
        """

        assert keypair.get_public() == self.getPublicKey()
        return self._bpki_certify(
            keypair      = keypair,
            issuer_name  = self.getSubject(),
            subject_name = subject_name,
            subject_key  = subject_key,
            serial       = serial,
            now          = now,
            notAfter     = notAfter,
            pathLenConstraint = pathLenConstraint,
            is_ca        = is_ca)

    @classmethod
    def _bpki_certify(cls, keypair, issuer_name, subject_name, subject_key,
                      serial, now, notAfter, pathLenConstraint, is_ca):
        """
        Issue a BPKI certificate.  This internal method does the real
        work, after one of the wrapper methods has extracted the relevant
        fields.
        """

        if now is None:
            now = rpki.sundial.now()

        issuer_key = keypair.get_public()

        assert (issuer_key == subject_key) == (issuer_name == subject_name)
        assert is_ca or issuer_name != subject_name
        assert is_ca or pathLenConstraint is None
        assert pathLenConstraint is None or (isinstance(pathLenConstraint, (int, long)) and
                                             pathLenConstraint >= 0)

        cert = rpki.POW.X509()
        cert.setVersion(2)
        cert.setSerial(serial)
        cert.setIssuer(issuer_name.get_POW())
        cert.setSubject(subject_name.get_POW())
        cert.setNotBefore(now)
        cert.setNotAfter(notAfter)
        cert.setPublicKey(subject_key.get_POW())
        cert.setSKI(subject_key.get_POW().calculateSKI())
        if issuer_key != subject_key:
            cert.setAKI(issuer_key.get_POW().calculateSKI())
        if is_ca:
            cert.setBasicConstraints(True, pathLenConstraint)
        cert.sign(keypair.get_POW(), rpki.POW.SHA256_DIGEST)
        return cls(POW = cert)

    @classmethod
    def normalize_chain(cls, chain):
        """
        Normalize a chain of certificates into a tuple of X509 objects.
        Given all the glue certificates needed for BPKI cross
        certification, it's easiest to allow sloppy arguments to the CMS
        validation methods and provide a single method that normalizes the
        allowed cases.  So this method allows X509, None, lists, and
        tuples, and returns a tuple of X509 objects.
        """

        if isinstance(chain, cls):
            chain = (chain,)
        return tuple(x for x in chain if x is not None)

    @property
    def creation_timestamp(self):
        """
        Time at which this object was created.
        """

        return self.getNotBefore()

class PKCS10(DER_object):
    """
    Class to hold a PKCS #10 request.
    """

    POW_class = rpki.POW.PKCS10

    ## @var expected_ca_keyUsage
    # KeyUsage extension flags expected for CA requests.

    expected_ca_keyUsage = frozenset(("keyCertSign", "cRLSign"))

    ## @var allowed_extensions
    # Extensions allowed by RPKI profile.

    allowed_extensions = frozenset((rpki.oids.basicConstraints,
                                    rpki.oids.keyUsage,
                                    rpki.oids.subjectInfoAccess,
                                    rpki.oids.extendedKeyUsage))


    def get_DER(self):
        """
        Get the DER value of this certification request.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWrite()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this certification request.
        """

        # pylint: disable=E0203,W0201
        self.check()
        if not self.POW:
            self.POW = rpki.POW.PKCS10.derRead(self.get_DER())
        return self.POW

    def getSubject(self):
        """
        Extract the subject name from this certification request.
        """

        return X501DN.from_POW(self.get_POW().getSubject())

    def getPublicKey(self):
        """
        Extract the public key from this certification request.
        """

        return PublicKey(POW = self.get_POW().getPublicKey())

    def get_SKI(self):
        """
        Compute SKI for public key from this certification request.
        """

        return self.getPublicKey().get_SKI()


    def check_valid_request_common(self):
        """
        Common code for checking this certification requests to see
        whether they conform to the RPKI certificate profile.

        Throws an exception if the request isn't valid, so if this method
        returns at all, the request is ok.

        You probably don't want to call this directly, as it only performs
        the checks that are common to all RPKI certificates.
        """

        if not self.get_POW().verify():
            raise rpki.exceptions.BadPKCS10("PKCS #10 signature check failed")

        ver = self.get_POW().getVersion()

        if ver != 0:
            raise rpki.exceptions.BadPKCS10("PKCS #10 request has bad version number %s" % ver)

        ku = self.get_POW().getKeyUsage()

        if ku is not None and self.expected_ca_keyUsage != ku:
            raise rpki.exceptions.BadPKCS10("PKCS #10 keyUsage doesn't match profile: %r" % ku)

        forbidden_extensions = self.get_POW().getExtensionOIDs() - self.allowed_extensions

        if forbidden_extensions:
            raise rpki.exceptions.BadExtension("Forbidden extension%s in PKCS #10 certificate request: %s" % (
                "" if len(forbidden_extensions) == 1 else "s",
                ", ".join(forbidden_extensions)))


    def check_valid_request_ca(self):
        """
        Check this certification request to see whether it's a valid
        request for an RPKI CA certificate.

        Throws an exception if the request isn't valid, so if this method
        returns at all, the request is ok.
        """

        self.check_valid_request_common()

        alg = self.get_POW().getSignatureAlgorithm()
        bc  = self.get_POW().getBasicConstraints()
        eku = self.get_POW().getEKU()
        sia = self.get_POW().getSIA()

        if alg != rpki.oids.sha256WithRSAEncryption:
            raise rpki.exceptions.BadPKCS10("PKCS #10 has bad signature algorithm for CA: %s" % alg)

        if bc is None or not bc[0] or bc[1] is not None:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA bad basicConstraints")

        if eku is not None:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA EKU not allowed")

        if sia is None:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA missing")

        caRepository, rpkiManifest, signedObject, rpkiNotify = sia

        logger.debug("check_valid_request_ca(): sia: %r", sia)

        if signedObject:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA must not have id-ad-signedObject")

        if not caRepository:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA must have id-ad-caRepository")

        if not any(uri.startswith("rsync://") for uri in caRepository):
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA id-ad-caRepository contains no rsync URIs")

        if any(uri.startswith("rsync://") and not uri.endswith("/") for uri in caRepository):
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA id-ad-caRepository does not end with slash")

        if not rpkiManifest:
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA must have id-ad-rpkiManifest")

        if not any(uri.startswith("rsync://") for uri in rpkiManifest):
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA id-ad-rpkiManifest contains no rsync URIs")

        if any(uri.startswith("rsync://") and uri.endswith("/") for uri in rpkiManifest):
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA id-ad-rpkiManifest ends with slash")

        if any(not uri.startswith("http://") and not uri.startswith("https://") for uri in rpkiNotify):
            raise rpki.exceptions.BadPKCS10("PKCS #10 CA SIA id-ad-rpkiNotify neither HTTP nor HTTPS")

    def check_valid_request_ee(self):
        """
        Check this certification request to see whether it's a valid
        request for an RPKI EE certificate.

        Throws an exception if the request isn't valid, so if this method
        returns at all, the request is ok.

        We're a bit less strict here than we are for either CA
        certificates or BGPSEC router certificates, because the profile is
        less tightly nailed down for unspecified-use RPKI EE certificates.
        Future specific purposes may impose tighter constraints.

        Note that this method does NOT apply to so-called "infrastructure"
        EE certificates (eg, the EE certificates embedded in manifests and
        ROAs); those are constrained fairly tightly, but they're also
        generated internally so we don't need to check them as user or
        protocol input.
        """

        self.check_valid_request_common()

        alg = self.get_POW().getSignatureAlgorithm()
        bc  = self.get_POW().getBasicConstraints()
        sia = self.get_POW().getSIA()

        logger.debug("check_valid_request_ee(): sia: %r", sia)

        caRepository, rpkiManifest, signedObject, rpkiNotify = sia or (None, None, None, None)

        if alg not in (rpki.oids.sha256WithRSAEncryption, rpki.oids.ecdsa_with_SHA256):
            raise rpki.exceptions.BadPKCS10("PKCS #10 has bad signature algorithm for EE: %s" % alg)

        if bc is not None and (bc[0] or bc[1] is not None):
            raise rpki.exceptions.BadPKCS10("PKCS #10 EE has bad basicConstraints")

        if caRepository:
            raise rpki.exceptions.BadPKCS10("PKCS #10 EE must not have id-ad-caRepository")

        if rpkiManifest:
            raise rpki.exceptions.BadPKCS10("PKCS #10 EE must not have id-ad-rpkiManifest")

        if signedObject and not any(uri.startswith("rsync://") for uri in signedObject):
            raise rpki.exceptions.BadPKCS10("PKCS #10 EE SIA id-ad-signedObject contains no rsync URIs")

        if rpkiNotify and any(not uri.startswith("http://") and not uri.startswith("https://") for uri in rpkiNotify):
            raise rpki.exceptions.BadPKCS10("PKCS #10 EE SIA id-ad-rpkiNotify neither HTTP nor HTTPS")

    def check_valid_request_router(self):
        """
        Check this certification request to see whether it's a valid
        request for a BGPSEC router certificate.

        Throws an exception if the request isn't valid, so if this method
        returns at all, the request is ok.

        draft-ietf-sidr-bgpsec-pki-profiles 3.2 says follow RFC 6487 3
        except where explicitly overriden, and does not override for SIA.
        But draft-ietf-sidr-bgpsec-pki-profiles also says that router
        certificates don't get SIA, while RFC 6487 requires SIA.  So what
        do we do with SIA in PKCS #10 for router certificates?

        For the moment, ignore it, but make sure we don't include it in
        the certificate when we get to the code that generates that.
        """

        self.check_valid_request_ee()

        alg  = self.get_POW().getSignatureAlgorithm()
        eku  = self.get_POW().getEKU()

        if alg != rpki.oids.ecdsa_with_SHA256:
            raise rpki.exceptions.BadPKCS10("PKCS #10 has bad signature algorithm for router: %s" % alg)

        # Not really clear to me whether PKCS #10 should have EKU or not, so allow
        # either, but insist that it be the right one if present.

        if eku is not None and rpki.oids.id_kp_bgpsec_router not in eku:
            raise rpki.exceptions.BadPKCS10("PKCS #10 router must have EKU")


    @classmethod
    def create(cls, keypair, exts = None, is_ca = False,
               caRepository = None, rpkiManifest = None, signedObject = None,
               cn = None, sn = None, eku = None, rpkiNotify = None):
        """
        Create a new request for a given keypair.
        """

        if cn is None:
            cn = "".join(("%02X" % ord(i) for i in keypair.get_SKI()))

        req = rpki.POW.PKCS10()
        req.setVersion(0)
        req.setSubject(X501DN.from_cn(cn, sn).get_POW())
        req.setPublicKey(keypair.get_POW())

        if is_ca:
            req.setBasicConstraints(True, None)
            req.setKeyUsage(cls.expected_ca_keyUsage)

        sia = (caRepository, rpkiManifest, signedObject, rpkiNotify)
        if not all(s is None for s in sia):
            req.setSIA(*tuple([str(s)] if isinstance(s, (str, unicode)) else s for s in sia))

        if eku:
            req.setEKU(eku)

        req.sign(keypair.get_POW(), rpki.POW.SHA256_DIGEST)
        return cls(POW = req)

## @var generate_insecure_debug_only_rsa_key
# Debugging hack to let us save throwaway RSA keys from one debug
# session to the next.  DO NOT USE THIS IN PRODUCTION.

generate_insecure_debug_only_rsa_key = None

class insecure_debug_only_rsa_key_generator(object):

    def __init__(self, filename, keyno = 0):
        try:
            try:
                import gdbm as dbm_du_jour
            except ImportError:
                import dbm as dbm_du_jour
            self.keyno = long(keyno)
            self.filename = filename
            self.db = dbm_du_jour.open(filename, "c")
        except:
            logger.warning("insecure_debug_only_rsa_key_generator initialization FAILED, hack inoperative")
            raise

    def __call__(self):
        k = str(self.keyno)
        try:
            v = rpki.POW.Asymmetric.derReadPrivate(self.db[k])
        except KeyError:
            v = rpki.POW.Asymmetric.generateRSA(2048)
            self.db[k] = v.derWritePrivate()
        self.keyno += 1
        return v


class PrivateKey(DER_object):
    """
    Class to hold a Public/Private key pair.
    """

    POW_class = rpki.POW.Asymmetric

    def get_DER(self):
        """
        Get the DER value of this keypair.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWritePrivate()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this keypair.
        """

        # pylint: disable=E0203,W0201
        self.check()
        if not self.POW:
            self.POW = rpki.POW.Asymmetric.derReadPrivate(self.get_DER())
        return self.POW

    def get_PEM(self):
        """
        Get the PEM representation of this keypair.
        """

        return self.get_POW().pemWritePrivate()

    def _set_PEM(self, pem):
        """
        Set the POW value of this keypair from a PEM string.
        """

        # pylint: disable=W0201
        assert self.empty()
        self.POW = self.POW_class.pemReadPrivate(pem)

    def get_public_DER(self):
        """
        Get the DER encoding of the public key from this keypair.
        """

        return self.get_POW().derWritePublic()

    def get_SKI(self):
        """
        Calculate the SKI of this keypair.
        """

        return self.get_POW().calculateSKI()

    def get_public(self):
        """
        Convert the public key of this keypair into a PublicKey object.
        """

        return PublicKey(DER = self.get_public_DER())

class PublicKey(DER_object):
    """
    Class to hold a public key.
    """

    POW_class = rpki.POW.Asymmetric

    def get_DER(self):
        """
        Get the DER value of this public key.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWritePublic()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this public key.
        """

        # pylint: disable=E0203,W0201
        self.check()
        if not self.POW:
            self.POW = rpki.POW.Asymmetric.derReadPublic(self.get_DER())
        return self.POW

    def get_PEM(self):
        """
        Get the PEM representation of this public key.
        """

        return self.get_POW().pemWritePublic()

    def _set_PEM(self, pem):
        """
        Set the POW value of this public key from a PEM string.
        """

        # pylint: disable=W0201
        assert self.empty()
        self.POW = self.POW_class.pemReadPublic(pem)

    def get_SKI(self):
        """
        Calculate the SKI of this public key.
        """

        return self.get_POW().calculateSKI()

class KeyParams(DER_object):
    """
    Wrapper for OpenSSL's asymmetric key parameter classes.
    """

    POW_class = rpki.POW.AsymmetricParams

    @classmethod
    def generateEC(cls, curve = rpki.POW.EC_P256_CURVE):
        return cls(POW = rpki.POW.AsymmetricParams.generateEC(curve = curve))

class RSA(PrivateKey):
    """
    Class to hold an RSA key pair.
    """

    @classmethod
    def generate(cls, keylength = 2048, quiet = False):
        """
        Generate a new keypair.
        """

        if not quiet:
            logger.debug("Generating new %d-bit RSA key", keylength)
        if generate_insecure_debug_only_rsa_key is not None:
            return cls(POW = generate_insecure_debug_only_rsa_key())
        else:
            return cls(POW = rpki.POW.Asymmetric.generateRSA(keylength))

class ECDSA(PrivateKey):
    """
    Class to hold an ECDSA key pair.
    """

    @classmethod
    def generate(cls, params = None, quiet = False):
        """
        Generate a new keypair.
        """

        if params is None:
            if not quiet:
                logger.debug("Generating new ECDSA key parameters")
            params = KeyParams.generateEC()

        assert isinstance(params, KeyParams)

        if not quiet:
            logger.debug("Generating new ECDSA key")

        return cls(POW = rpki.POW.Asymmetric.generateFromParams(params.get_POW()))

class CMS_object(DER_object):
    """
    Abstract class to hold a CMS object.
    """

    econtent_oid = rpki.oids.id_data
    POW_class = rpki.POW.CMS

    ## @var dump_on_verify_failure
    # Set this to True to get dumpasn1 dumps of ASN.1 on CMS verify failures.

    dump_on_verify_failure = True

    ## @var debug_cms_certs
    # Set this to True to log a lot of chatter about CMS certificates.

    debug_cms_certs = False

    ## @var dump_using_dumpasn1
    # Set this to use external dumpasn1 program, which is prettier and
    # more informative than OpenSSL's CMS text dump, but which won't
    # work if the dumpasn1 program isn't installed.

    dump_using_dumpasn1 = False

    ## @var require_crls
    # Set this to False to make CMS CRLs optional in the cases where we
    # would otherwise require them.  Some day this option should go away
    # and CRLs should be uncondtionally mandatory in such cases.

    require_crls = False

    ## @var allow_extra_certs
    # Set this to True to allow CMS messages to contain CA certificates.

    allow_extra_certs = False

    ## @var allow_extra_crls
    # Set this to True to allow CMS messages to contain multiple CRLs.

    allow_extra_crls = False

    ## @var print_on_der_error
    # Set this to True to log alleged DER when we have trouble parsing
    # it, in case it's really a Perl backtrace or something.

    print_on_der_error = True

    def get_DER(self):
        """
        Get the DER value of this CMS_object.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWrite()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this CMS_object.
        """

        # pylint: disable=E0203,W0201
        self.check()
        if not self.POW:
            self.POW = self.POW_class.derRead(self.get_DER())
        return self.POW

    def get_signingTime(self):
        """
        Extract signingTime from CMS signed attributes.
        """

        return self.get_POW().signingTime()

    def verify(self, ta):
        """
        Verify CMS wrapper and store inner content.
        """

        try:
            cms = self.get_POW()
        except:
            if self.print_on_der_error:
                logger.debug("Problem parsing DER CMS message, might not really be DER: %r",
                             self.get_DER())
            raise rpki.exceptions.UnparsableCMSDER

        if cms.eContentType() != self.econtent_oid:
            raise rpki.exceptions.WrongEContentType("Got CMS eContentType %s, expected %s" % (
                cms.eContentType(), self.econtent_oid))

        certs = [X509(POW = x) for x in cms.certs()]
        crls  = [CRL(POW = c) for c in cms.crls()]

        if self.debug_cms_certs:
            for x in certs:
                logger.debug("Received CMS cert issuer %s subject %s SKI %s",
                             x.getIssuer(), x.getSubject(), x.hSKI())
            for c in crls:
                logger.debug("Received CMS CRL issuer %r", c.getIssuer())

        now = rpki.sundial.now()

        trusted_ee = None
        trusted_ca = []
        untrusted_ee = None

        for x in X509.normalize_chain(ta):
            if self.debug_cms_certs:
                logger.debug("CMS trusted cert issuer %s subject %s SKI %s",
                             x.getIssuer(), x.getSubject(), x.hSKI())
            if x.getNotAfter() < now:
                raise rpki.exceptions.TrustedCMSCertHasExpired("Trusted CMS certificate has expired",
                                                               "%s (%s)" % (x.getSubject(), x.hSKI()))
            if x.is_CA():
                trusted_ca.append(x)
            else:
                if trusted_ee is None:
                    trusted_ee = x
                else:
                    raise rpki.exceptions.MultipleCMSEECert("Multiple CMS EE certificates", *("%s (%s)" % (
                        x.getSubject(), x.hSKI()) for x in ta if not x.is_CA()))

        if trusted_ee:
            if self.debug_cms_certs:
                logger.debug("Trusted CMS EE cert issuer %s subject %s SKI %s",
                             trusted_ee.getIssuer(), trusted_ee.getSubject(), trusted_ee.hSKI())
            if len(certs) > 1 or (len(certs) == 1 and
                                  (certs[0].getSubject() != trusted_ee.getSubject() or
                                   certs[0].getPublicKey() != trusted_ee.getPublicKey())):
                raise rpki.exceptions.UnexpectedCMSCerts("Unexpected CMS certificates", *("%s (%s)" % (
                    x.getSubject(), x.hSKI()) for x in certs))
            if crls:
                raise rpki.exceptions.UnexpectedCMSCRLs("Unexpected CRLs", *("%s (%s)" % (
                    c.getIssuer(), c.hAKI()) for c in crls))

        else:
            untrusted_ee = [x for x in certs if not x.is_CA()]
            if len(untrusted_ee) < 1:
                raise rpki.exceptions.MissingCMSEEcert
            if len(untrusted_ee) > 1 or (not self.allow_extra_certs and len(certs) > len(untrusted_ee)):
                raise rpki.exceptions.UnexpectedCMSCerts("Unexpected CMS certificates", *("%s (%s)" % (
                    x.getSubject(), x.hSKI()) for x in certs))
            untrusted_ee = untrusted_ee[0]
            if len(crls) < 1:
                if self.require_crls:
                    raise rpki.exceptions.MissingCMSCRL
                else:
                    logger.warning("MISSING CMS CRL!  Ignoring per self.require_crls setting")
            if len(crls) > 1 and not self.allow_extra_crls:
                raise rpki.exceptions.UnexpectedCMSCRLs("Unexpected CRLs", *("%s (%s)" % (
                    c.getIssuer(), c.hAKI()) for c in crls))

        for x in certs:
            if x.getNotAfter() < now:
                raise rpki.exceptions.CMSCertHasExpired("CMS certificate has expired", "%s (%s)" % (
                    x.getSubject(), x.hSKI()))

        for c in crls:
            if c.getNextUpdate() < now:
                logger.warning("Stale BPKI CMS CRL (%s %s %s)", c.getNextUpdate(), c.getIssuer(), c.hAKI())

        # XXX Verify certificate chain via X.509 machinery, not CMS
        # machinery.  Awful mess due to history, needs cleanup, but
        # get it working again first.

        cert = (trusted_ee or untrusted_ee).get_POW()

        cert.verify(trusted = (x.get_POW() for x in trusted_ca),
                    crl     = crls[0].get_POW() if untrusted_ee and crls else None)

        try:
            # XXX This isn't right yet, but let's test before gettting more complicated
            #
            # Aside from all the type and exception abominations, the
            # main problem here is that we're no longer verifying the
            # certificate chain, just the CMS signature.  Certificate
            # verificaiton is a separate step under the new scheme,
            # and probably comes before this, but let's write down
            # what the problem is before it gets lost...

            content = cms.verify(certs = (x.get_POW() for x in X509.normalize_chain(ta)),
                                 flags = rpki.POW.CMS_NO_SIGNER_CERT_VERIFY)
        except:
            if self.dump_on_verify_failure:
                if self.dump_using_dumpasn1:
                    dbg = self.dumpasn1()
                else:
                    dbg = cms.pprint()
                logger.warning("CMS verification failed, dumping ASN.1 (%d octets):", len(self.get_DER()))
                for line in dbg.splitlines():
                    logger.warning(line)

            # XXX Old code replaced rpki.POW exception with this.  For
            # debugging I'd rather see what POW has to say; decide
            # later whether to keep this change.
            #
            #raise rpki.exceptions.CMSVerificationFailed("CMS verification failed")
            raise

        return content

    def extract(self):
        """
        Extract and store inner content from CMS wrapper without verifying
        the CMS.

        DANGER WILL ROBINSON!!!

        Do not use this method on unvalidated data.  Use the verify()
        method instead.

        If you don't understand this warning, don't use this method.
        """

        try:
            cms = self.get_POW()
        except:
            raise rpki.exceptions.UnparsableCMSDER

        if cms.eContentType() != self.econtent_oid:
            raise rpki.exceptions.WrongEContentType("Got CMS eContentType %s, expected %s" % (
                cms.eContentType(), self.econtent_oid))

        return cms.verify(flags = (rpki.POW.CMS_NOCRL | rpki.POW.CMS_NO_SIGNER_CERT_VERIFY |
                                   rpki.POW.CMS_NO_ATTR_VERIFY | rpki.POW.CMS_NO_CONTENT_VERIFY))


    def sign(self, keypair, certs, crls = None, no_certs = False):
        """
        Sign and wrap inner content.
        """

        if isinstance(certs, X509):
            cert = certs
            certs = ()
        else:
            cert = certs[0]
            certs = certs[1:]

        if crls is None:
            crls = ()
        elif isinstance(crls, CRL):
            crls = (crls,)

        if self.debug_cms_certs:
            logger.debug("Signing with cert issuer %s subject %s SKI %s",
                         cert.getIssuer(), cert.getSubject(), cert.hSKI())
            for i, c in enumerate(certs):
                logger.debug("Additional cert %d issuer %s subject %s SKI %s",
                             i, c.getIssuer(), c.getSubject(), c.hSKI())

        self._sign(cert.get_POW(),
                   keypair.get_POW(),
                   [x.get_POW() for x in certs],
                   [c.get_POW() for c in crls],
                   rpki.POW.CMS_NOCERTS if no_certs else 0)

    def _sign(self, cert, keypair, certs, crls, flags):
        raise NotImplementedError

    @property
    def creation_timestamp(self):
        """
        Time at which this object was created.
        """

        return self.get_signingTime()


class Wrapped_CMS_object(CMS_object):
    """
    Abstract class to hold CMS objects wrapping non-DER content (eg, XML
    or VCard).

    CMS-wrapped objects are a little different from the other DER_object
    types because the signed object is CMS wrapping some other kind of
    inner content.  A Wrapped_CMS_object is the outer CMS wrapped object
    so that the usual DER and PEM operations do the obvious things, and
    the inner content is handle via separate methods.
    """

    other_clear = ("content",)

    def get_content(self):
        """
        Get the inner content of this Wrapped_CMS_object.
        """

        if self.content is None:
            raise rpki.exceptions.CMSContentNotSet("Inner content of CMS object %r is not set" % self)
        return self.content

    def set_content(self, content):
        """
        Set the (inner) content of this Wrapped_CMS_object, clearing the wrapper.
        """

        # pylint: disable=W0201
        self.clear()
        self.content = content

    def verify(self, ta):
        """
        Verify CMS wrapper and store inner content.
        """

        self.decode(CMS_object.verify(self, ta))
        return self.get_content()

    def extract(self):
        """
        Extract and store inner content from CMS wrapper without verifying
        the CMS.

        DANGER WILL ROBINSON!!!

        Do not use this method on unvalidated data.  Use the verify()
        method instead.

        If you don't understand this warning, don't use this method.
        """

        self.decode(CMS_object.extract(self))
        return self.get_content()

    def extract_if_needed(self):
        """
        Extract inner content if needed.  See caveats for .extract(), do
        not use unless you really know what you are doing.
        """

        if self.content is None:
            self.extract()

    def _sign(self, cert, keypair, certs, crls, flags):
        """
        Internal method to call POW to do CMS signature.  This is split
        out from the .sign() API method to handle differences in how
        different CMS-based POW classes handle the inner content.
        """

        # pylint: disable=W0201
        cms = self.POW_class()
        cms.sign(cert, keypair, self.encode(), certs, crls, self.econtent_oid, flags)
        self.POW = cms

    def decode(self, whatever):
        raise NotImplementedError

    def encode(self):
        raise NotImplementedError


class DER_CMS_object(CMS_object):
    """
    Abstract class for CMS-based objects with DER-encoded content
    handled by C-level subclasses of rpki.POW.CMS.
    """

    def _sign(self, cert, keypair, certs, crls, flags):
        self.get_POW().sign(cert, keypair, certs, crls, self.econtent_oid, flags)


    def extract_if_needed(self):
        """
        Extract inner content if needed.  See caveats for .extract(), do
        not use unless you really know what you are doing.
        """

        try:
            self.get_POW().getVersion()
        except rpki.POW.NotVerifiedError:
            self.extract()


class SignedManifest(DER_CMS_object):
    """
    Class to hold a signed manifest.
    """

    econtent_oid = rpki.oids.id_ct_rpkiManifest
    POW_class = rpki.POW.Manifest

    def getThisUpdate(self):
        """
        Get thisUpdate value from this manifest.
        """

        return self.get_POW().getThisUpdate()

    def getNextUpdate(self):
        """
        Get nextUpdate value from this manifest.
        """

        return self.get_POW().getNextUpdate()

    @classmethod
    def build(cls, serial, thisUpdate, nextUpdate, names_and_objs, keypair, certs, version = 0):
        """
        Build a signed manifest.
        """

        filelist = []
        for name, obj in names_and_objs:
            filelist.append((name.rpartition("/")[2], sha256(obj.get_DER())))
        filelist.sort(key = lambda x: x[0])

        obj = cls.POW_class()
        obj.setVersion(version)
        obj.setManifestNumber(serial)
        obj.setThisUpdate(thisUpdate)
        obj.setNextUpdate(nextUpdate)
        obj.setAlgorithm(rpki.oids.id_sha256)
        obj.addFiles(filelist)

        self = cls(POW = obj)
        self.sign(keypair, certs)
        return self

class ROA(DER_CMS_object):
    """
    Class to hold a signed ROA.
    """

    econtent_oid = rpki.oids.id_ct_routeOriginAttestation
    POW_class = rpki.POW.ROA

    @classmethod
    def build(cls, asn, ipv4, ipv6, keypair, certs, version = 0):
        """
        Build a ROA.
        """

        ipv4 = ipv4.to_POW_roa_tuple() if ipv4 else None
        ipv6 = ipv6.to_POW_roa_tuple() if ipv6 else None
        obj = cls.POW_class()
        obj.setVersion(version)
        obj.setASID(asn)
        obj.setPrefixes(ipv4 = ipv4, ipv6 = ipv6)
        self = cls(POW = obj)
        self.sign(keypair, certs)
        return self

    def tracking_data(self, uri):
        """
        Return a string containing data we want to log when tracking how
        objects move through the RPKI system.
        """

        msg = DER_CMS_object.tracking_data(self, uri)
        try:
            self.extract_if_needed()
            asn = self.get_POW().getASID()
            text = []
            for prefixes in self.get_POW().getPrefixes():
                if prefixes is not None:
                    for prefix, prefixlen, maxprefixlen in prefixes:
                        if maxprefixlen is None or prefixlen == maxprefixlen:
                            text.append("%s/%s" % (prefix, prefixlen))
                        else:
                            text.append("%s/%s-%s" % (prefix, prefixlen, maxprefixlen))
            text.sort()
            msg = "%s %s %s" % (msg, asn, ",".join(text))
        except:
            pass
        return msg

class DeadDrop(object):
    """
    Dead-drop utility for storing copies of CMS messages for debugging or
    audit.  At the moment this uses Maildir mailbox format, as it has
    approximately the right properties and a number of useful tools for
    manipulating it already exist.
    """

    def __init__(self, name):
        self.name = name
        self.pid = os.getpid()
        self.maildir = mailbox.Maildir(name, factory = None, create = True)
        self.warned = False

    def dump(self, obj):
        try:
            now = time.time()
            msg = email.mime.application.MIMEApplication(obj.get_DER(), "x-rpki")
            msg["Date"] = email.utils.formatdate(now)
            msg["Subject"] = "Process %s dump of %r" % (self.pid, obj)
            msg["Message-ID"] = email.utils.make_msgid()
            msg["X-RPKI-PID"] = str(self.pid)
            msg["X-RPKI-Object"] = repr(obj)
            msg["X-RPKI-Timestamp"] = "%f" % now
            self.maildir.add(msg)
            self.warned = False
        except Exception, e:
            if not self.warned:
                logger.warning("Could not write to mailbox %s: %s", self.name, e)
                self.warned = True

class XML_CMS_object(Wrapped_CMS_object):
    """
    Class to hold CMS-wrapped XML protocol data.
    """

    econtent_oid = rpki.oids.id_ct_xml
    encoding = None
    schema   = None

    ## @var dump_outbound_cms
    # If set, we write all outbound XML-CMS PDUs to disk, for debugging.
    # If set, value should be a DeadDrop object.

    dump_outbound_cms = None

    ## @var dump_inbound_cms
    # If set, we write all inbound XML-CMS PDUs to disk, for debugging.
    # If set, value should be a DeadDrop object.

    dump_inbound_cms = None

    ## @var check_inbound_schema
    # If set, perform RelaxNG schema check on inbound messages.

    check_inbound_schema = True

    ## @var check_outbound_schema
    # If set, perform RelaxNG schema check on outbound messages.

    check_outbound_schema = True

    def encode(self):
        """
        Encode inner content for signing.
        """

        return lxml.etree.tostring(self.get_content(),
                                   pretty_print = True,
                                   encoding = self.encoding,
                                   xml_declaration = True)

    def decode(self, xml):
        """
        Decode XML and set inner content.
        """

        # pylint: disable=W0201
        self.content = lxml.etree.fromstring(xml)

    def pretty_print_content(self):
        """
        Pretty print XML content of this message.
        """

        return lxml.etree.tostring(self.get_content(),
                                   pretty_print = True,
                                   encoding = self.encoding,
                                   xml_declaration = True)

    def schema_check(self):
        """
        Handle XML RelaxNG schema check.
        """

        try:
            self.schema.assertValid(self.get_content())
        except lxml.etree.DocumentInvalid:
            logger.error("PDU failed schema check")
            for line in self.pretty_print_content().splitlines():
                logger.warning(line)
            raise

    def dump_to_disk(self, prefix):
        """
        Write DER of current message to disk, for debugging.
        """

        f = open(prefix + rpki.sundial.now().isoformat() + "Z.cms", "wb")
        f.write(self.get_DER())
        f.close()

    def wrap(self, msg, keypair, certs, crls = None):
        """
        Wrap an XML PDU in CMS and return its DER encoding.
        """

        self.set_content(msg)
        if self.check_outbound_schema:
            self.schema_check()
        self.sign(keypair, certs, crls)
        if self.dump_outbound_cms:
            self.dump_outbound_cms.dump(self)
        return self.get_DER()

    def unwrap(self, ta):
        """
        Unwrap a CMS-wrapped XML PDU and return Python objects.
        """

        if self.dump_inbound_cms:
            self.dump_inbound_cms.dump(self)
        self.verify(ta)
        if self.check_inbound_schema:
            self.schema_check()
        return self.get_content()

    def check_replay(self, timestamp, *context):
        """
        Check CMS signing-time in this object against a recorded
        timestamp.  Raises an exception if the recorded timestamp is more
        recent, otherwise returns the new timestamp.
        """

        new_timestamp = self.get_signingTime()
        if timestamp is not None and timestamp > new_timestamp:
            if context:
                context = " (" + " ".join(context) + ")"
            raise rpki.exceptions.CMSReplay(
                "CMS replay: last message %s, this message %s%s" % (
                    timestamp, new_timestamp, context))
        return new_timestamp

    def check_replay_sql(self, obj, *context):
        """
        Like .check_replay() but gets recorded timestamp from
        "last_cms_timestamp" field of an SQL object and stores the new
        timestamp back in that same field.
        """

        obj.last_cms_timestamp = self.check_replay(obj.last_cms_timestamp, *context)
        obj.save()

class SignedReferral(XML_CMS_object):
    encoding = "us-ascii"
    schema = rpki.relaxng.oob_setup

class Ghostbuster(Wrapped_CMS_object):
    """
    Class to hold Ghostbusters record (CMS-wrapped VCard).  This is
    quite minimal because we treat the VCard as an opaque byte string
    managed by the back-end.
    """

    econtent_oid = rpki.oids.id_ct_rpkiGhostbusters

    def encode(self):
        """
        Encode inner content for signing.  At the moment we're treating
        the VCard as an opaque byte string, so no encoding needed here.
        """

        return self.get_content()

    def decode(self, vcard):
        """
        Decode XML and set inner content.  At the moment we're treating
        the VCard as an opaque byte string, so no encoding needed here.
        """

        # pylint: disable=W0201
        self.content = vcard

    @classmethod
    def build(cls, vcard, keypair, certs):
        """
        Build a Ghostbuster record.
        """

        self = cls()
        self.set_content(vcard)
        self.sign(keypair, certs)
        return self


class CRL(DER_object):
    """
    Class to hold a Certificate Revocation List.
    """

    POW_class = rpki.POW.CRL

    def get_DER(self):
        """
        Get the DER value of this CRL.
        """

        self.check()
        if self.DER:
            return self.DER
        if self.POW:
            self.DER = self.POW.derWrite()
            return self.get_DER()
        raise rpki.exceptions.DERObjectConversionError("No conversion path to DER available")

    def get_POW(self):
        """
        Get the rpki.POW value of this CRL.
        """

        # pylint: disable=W0201,E0203
        self.check()
        if not self.POW:
            self.POW = rpki.POW.CRL.derRead(self.get_DER())
        return self.POW

    def getThisUpdate(self):
        """
        Get thisUpdate value from this CRL.
        """

        return self.get_POW().getThisUpdate()

    def getNextUpdate(self):
        """
        Get nextUpdate value from this CRL.
        """

        return self.get_POW().getNextUpdate()

    def getIssuer(self):
        """
        Get issuer value of this CRL.
        """

        return X501DN.from_POW(self.get_POW().getIssuer())

    def getCRLNumber(self):
        """
        Get CRL Number value for this CRL.
        """

        return self.get_POW().getCRLNumber()

    @classmethod
    def generate(cls, keypair, issuer, serial, thisUpdate, nextUpdate, revokedCertificates, version = 1):
        """
        Generate a new CRL.
        """

        crl = rpki.POW.CRL()
        crl.setVersion(version)
        crl.setIssuer(issuer.getSubject().get_POW())
        crl.setThisUpdate(thisUpdate)
        crl.setNextUpdate(nextUpdate)
        crl.setAKI(issuer.get_SKI())
        crl.setCRLNumber(serial)
        crl.addRevocations(revokedCertificates)
        crl.sign(keypair.get_POW())
        return cls(POW = crl)

    @property
    def creation_timestamp(self):
        """
        Time at which this object was created.
        """

        return self.getThisUpdate()

## @var uri_dispatch_map
# Map of known URI filename extensions and corresponding classes.

uri_dispatch_map = {
    ".cer" : X509,
    ".crl" : CRL,
    ".gbr" : Ghostbuster,
    ".mft" : SignedManifest,
    ".mnf" : SignedManifest,
    ".roa" : ROA }

def uri_dispatch(uri):
    """
    Return the Python class object corresponding to a given URI.
    """

    return uri_dispatch_map[os.path.splitext(uri)[1]]