This is a script which tests for the bug in https://github.com/akkornel/syncrepl/issues/18

syncrepl_issue18_test.py

#!/bin/env python3

import pyasn1
from pyasn1.type import constraint, namedtype, namedval, univ
from pyasn1.codec.ber.decoder import decode
from uuid import UUID

# These come from Python-LDAP's syncrepl module.
# They're definitions for pyasn1 to understand what it's parsing.

class syncUUID(univ.OctetString):
    subtypeSpec = constraint.ValueSizeConstraint(16,16)

class syncCookie(univ.OctetString):
    pass

class syncStateOp(univ.Enumerated):
    namedValues = namedval.NamedValues(
        ('present', 0),
        ('add', 1),
        ('modify', 2),
        ('delete', 3)
    )
    subtypeSpec = univ.Enumerated.subtypeSpec + constraint.SingleValueConstraint(0,1,2,3)

class syncStateValue(univ.Sequence):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('state', syncStateOp()),
        namedtype.NamedType('entryUUID', syncUUID()),
        namedtype.OptionalNamedType('cookie', syncCookie())
    )

# Now, let's take our ASN.1 and decode it.

asn1_binary = b'0\x15\n\x01\x01\x04\x10\xe1\xd5\x7fN#O\x105\x97\xa2MV\x06\x18\x0co'
asn1_decoded = decode(asn1_binary,
    asn1Spec = syncStateValue()
)

# Break out each item from the decoded ASN.1

decoded_state = asn1_decoded[0].getComponentByName('state')
decoded_uuid = asn1_decoded[0].getComponentByName('entryUUID')
decoded_cookie = asn1_decoded[0].getComponentByName('cookie')

# Now, try to print it.
# Note that PyASN.1 is lazy, so it doesn't evaluate everything until now.

print('pyasn1 version is', pyasn1.__version__)
print('state is', decoded_state)
print('uuid is', UUID(bytes=bytes(decoded_uuid)))
print('cookie is', decoded_cookie)