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python-rsa / rsa / asn1.py

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'''ASN.1 definitions.

Not all ASN.1-handling code use these definitions, but when it does, they should be here.
'''

from pyasn1.type import univ, namedtype, tag

class PubKeyHeader(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('oid', univ.ObjectIdentifier()),
        namedtype.NamedType('parameters', univ.Null()),
    )

class OpenSSLPubKey(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('header', PubKeyHeader()),
        
        # This little hack (the implicit tag) allows us to get a Bit String as Octet String
        namedtype.NamedType('key', univ.OctetString().subtype(
                                          implicitTag=tag.Tag(tagClass=0, tagFormat=0, tagId=3))),
    )


class AsnPubKey(univ.Sequence):
    '''ASN.1 contents of DER encoded public key:
    
    RSAPublicKey ::= SEQUENCE {
         modulus           INTEGER,  -- n
         publicExponent    INTEGER,  -- e
    '''

    componentType = namedtype.NamedTypes(
        namedtype.NamedType('modulus', univ.Integer()),
        namedtype.NamedType('publicExponent', univ.Integer()),
    )