A couple of potential security bugs

[nalind]

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Hi, I got a couple of bug reports today that affect the client library. #1332508 is largely about checks that we have around getenv() no longer being sufficient, and #1332493 is about avoiding inadvertently switching to querying MIT's hesiod data.

I've got a proposed patch attached to each, and can open PRs for merging them, but if you'd prefer a different approach, I'm happy to rework them or wait.

[achernya]

Patch in #1332508 looks good as-is, submit a PR.

#1153517 I am not so sure about. Hesiod fundamentally does not support DNSSEC; root accounts/injection should be prevented by using something like nss_nonlocal. I'd say submit a separate PR for it, but I'll have to involve some other MIT Athena people for comment before merging it.

[nalind]

Okay, will do. Thanks!