crypto: Fix bug when using old hmac context

Symptom: Using an old context (that had already been passed as argument to either
hmac_upgrade or hmac_final) could cause VM crash or worse.

Reason: Only a shallow copy (memcpy) of the context was made causing
a new context to partly mutate its parent context into an inconsistent
state.

Problem: Only OpenSSL v1.0 supports deep copy of hmac context. It is thus
not possible to implement a functional interface for older OpenSSL
versions (0.9.8) which still have wide spread use.

Solution: Change hmac contexts into a mutable state using NIF resources.
Document reuse of old contexts as undefined.

Future: If a need for reusing old context variables arise, a new hmac_copy
function could be introduced that is only supported for OpenSSL v1.0.

0 files changed, 0 insertions, 0 deletions