`add_related` breaks existing ObjectProperties parent Objects

[gtback]

The current implementation of add_related (used to relate two different objects together) is currently broken. If you create three ObjectProperties (A, B and C), and run the following:

A.add_related(B, ...)
C.add_related(A, ...)

then the relationship between A and B will be broken. This is due to the fact that relationships are between Objects, but the add_related function operates on the contained ObjectProperties. add_related creates a new RelatedObject (see here) as the parent of the ObjectProperties that is being added. Thus, the relationship between A and B is severed as a result of the second call.

A workaround is to switch the order of these calls. This is not a 100% solution for more complicated sets of relationships, but should hopefully help until we can fix this.

C.add_related(A, ...)
A.add_related(B, ...)

Thanks to @brlogan for identifying this bug.

[gtback]

As a more concrete example:

from cybox.objects.artifact_object import Artifact
from cybox.objects.email_message_object import EmailMessage, Attachments
from cybox.objects.file_object import File
filename = "example.txt"
data = "blah blah blah contents of file"

f = File()
f.file_name = filename
a = Artifact(data, Artifact.TYPE_FILE)
f.add_related(a, "Child_Of") # This is the A.add_related(B, ...)

m = EmailMessage()
m.from_ = "bob@example.com"
m.subject = "this is an email"
m.attachments = Attachments()
m.add_related(f, "Contains", inline=True) # This is C.add_related(A, ...)
# Move it to here: 
# f.add_related(a, "Child_Of")
m.attachments.append(f.parent.id_)

[brlogan]

Thanks for looking into this, @gtback!