[ldns-users] Missing NULL check in ldns_rr_compare_ds

[Max Liebkies]

Hi,

I recently stumbled over a segfault in the Python ldns wrapper in the
ldns_rr_compare_ds method. I seem to have been calling the method with
at least one argument being None. As the underlying C method clones both
ldns_rr structs first but doesn't check the return value of
ldns_rr_clone, the subsequent calls to ldns_rr_set_ttl will segfault.

How to reproduce with python:
>>> from ldns import ldns_rr_compare_ds
>>> ldns_rr_compare_ds(None, None)

Please see the attached patch for a fix in rr.c

Cheers,
Max

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