# Modified from an example in the Python ASN.1 package to read certificate
# files and extract key bits.  More recent versions of m2crypto support this
# more directly.

import sys, string, base64
from pyasn1.type import tag,namedtype,namedval,univ,constraint,char,useful
from pyasn1.codec.der import decoder, encoder
from pyasn1 import error

from M2Crypto import EVP

# Would be autogenerated from ASN.1 source by a ASN.1 parser
# X.509 spec (rfc2459)

MAX = 64  # XXX ?

class DirectoryString(univ.Choice):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('teletexString', char.TeletexString().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))),
        namedtype.NamedType('printableString', char.PrintableString().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))),
        namedtype.NamedType('universalString', char.UniversalString().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))),
        namedtype.NamedType('utf8String', char.UTF8String().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))),
        namedtype.NamedType('bmpString', char.BMPString().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))),
        namedtype.NamedType('ia5String', char.IA5String().subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX))) # hm, this should not be here!? XXX
        )

class AttributeValue(DirectoryString): pass

class AttributeType(univ.ObjectIdentifier): pass

class AttributeTypeAndValue(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('type', AttributeType()),
        namedtype.NamedType('value', AttributeValue())
        )

class RelativeDistinguishedName(univ.SetOf):
    componentType = AttributeTypeAndValue()

class RDNSequence(univ.SequenceOf):
    componentType = RelativeDistinguishedName()

class Name(univ.Choice):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('', RDNSequence())
        )
                          
class AlgorithmIdentifier(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('algorithm', univ.ObjectIdentifier()),
        namedtype.OptionalNamedType('parameters', univ.Null())
        # XXX syntax screwed?
#        namedtype.OptionalNamedType('parameters', univ.ObjectIdentifier())
        )

class Extension(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('extnID', univ.ObjectIdentifier()),
        namedtype.DefaultedNamedType('critical', univ.Boolean('False')),
        namedtype.NamedType('extnValue', univ.OctetString())
        )

class Extensions(univ.SequenceOf):
    componentType = Extension()
    sizeSpec = univ.SequenceOf.sizeSpec + constraint.ValueSizeConstraint(1, MAX)

class SubjectPublicKeyInfo(univ.Sequence):
     componentType = namedtype.NamedTypes(
         namedtype.NamedType('algorithm', AlgorithmIdentifier()),
         namedtype.NamedType('subjectPublicKey', univ.BitString())
         )

class UniqueIdentifier(univ.BitString): pass

class Time(univ.Choice):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('utcTime', useful.UTCTime()),
        namedtype.NamedType('generalTime', useful.GeneralizedTime())
        )
    
class Validity(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('notBefore', Time()),
        namedtype.NamedType('notAfter', Time())
        )

class CertificateSerialNumber(univ.Integer): pass

class Version(univ.Integer):
    namedValues = namedval.NamedValues(
        ('v1', 0), ('v2', 1), ('v3', 2)
        )

class TBSCertificate(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.DefaultedNamedType('version', Version('v1', tagSet=Version.tagSet.tagExplicitly(tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 0)))),
        namedtype.NamedType('serialNumber', CertificateSerialNumber()),
        namedtype.NamedType('signature', AlgorithmIdentifier()),
        namedtype.NamedType('issuer', Name()),
        namedtype.NamedType('validity', Validity()),
        namedtype.NamedType('subject', Name()),
        namedtype.NamedType('subjectPublicKeyInfo', SubjectPublicKeyInfo()),
        namedtype.OptionalNamedType('issuerUniqueID', UniqueIdentifier().subtype(implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 1))),
        namedtype.OptionalNamedType('subjectUniqueID', UniqueIdentifier().subtype(implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 2))),
        namedtype.OptionalNamedType('extensions', Extensions().subtype(explicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 3)))
        )

class Certificate(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('tbsCertificate', TBSCertificate()),
        namedtype.NamedType('signatureAlgorithm', AlgorithmIdentifier()),
        namedtype.NamedType('signatureValue', univ.BitString())
        )

# end of ASN.1 data structures


def get_bits(substrate):
    certType = Certificate()
    cert = decoder.decode(substrate, asn1Spec=certType)[0]
    n = cert
    for name in ('tbsCertificate', 'subjectPublicKeyInfo', 
	    'subjectPublicKey'):
	n = n.getComponentByName(name)
	if n == None: raise RuntimeException("Bad cert")

    b = []
    for i in range(0, len(n), 8):
	v = 0
	for j in range(0, 8):
	    v = (v << 1) + n[i+j]
	b.append(v)

    return str().join([chr(x) for x in b])


def get_key_bits_from_file(fname):
    stSpam, stHam, stDump = 0, 1, 2
    state = stSpam

    f = open(fname)

    for certLine in f:
	certLine = string.strip(certLine)
	if state == stSpam:
	    if certLine == '-----BEGIN CERTIFICATE-----':
		substrate = ""
		state = stHam
		continue
	if state == stHam:
	    if certLine == '-----END CERTIFICATE-----':
		state = stDump
	    else:
		substrate = substrate + base64.b64decode(certLine)
	if state == stDump:
	    f.close()
	    return get_bits(substrate)

def get_key_bits_from_cert(cert):
    return get_bits(cert.as_der())