Free HMAC context when garbage collected #38
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This PR fix a memory leak on
NewHMAC(). The returned instance owns aC.GO_HMAC_CTX_PTRallocated usingC.malloc. The logic to free the context memory resides inopensslHMAC.finalize, which should be called automatically when the hmac instance is garbage collected.The problem is that Go doesn't know it has to call
opensslHMAC.finalize, we have to instruct it by callingruntime.SetFinalizer(hmac, (*opensslHMAC).finalize)just after instantiating the hmac. And we are not doing that. We used to do it when we initially port RedHat codebase but, at some point, that call was unintentionally removed.A
C.GO_HMAC_CTX_PTRweights around 300 bytes, so we are leaking that amount on everyNewHMAC()call, which means ~1GB of memory is lost every 3 milions calls.Found via fuzzing.