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<a href="https://gitlab.com/tobhe">Tobias Heider</a> created a merge request: <a href="https://gitlab.com/gnutls/gnutls/-/merge_requests/1554">!1554</a>
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Project:Branches: tobhe/gnutls:gmp_alloc to gnutls/gnutls:master
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Author: Tobias Heider
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<p dir="auto">I am trying to figure out to make sure that all intermediate products of cryptographic operations (e.g. private key generation) are safely zeroized. FIPS140-3 requires zeroization of all intermediate key generation values as well as the internal RBG state, but I think this would also be useful hardening for normal operation.</p>
<p dir="auto">gnutls outsources these cryptographic operations to nettle, which in turn uses GMP internally to
store a lot of sensitive data.
The <a href="http://www.lysator.liu.se/~nisse/nettle/nettle.html#index-rsa_005fprivate_005fkey_005fclear" rel="nofollow noreferrer noopener" target="_blank">nettle documentation</a> for the <code>rsa_private_key_clear()</code> function mentions that the
caller can change the default behavior by overriding the GMP allocator as described <a href="https://gmplib.org/manual/Custom-Allocation#Custom-Allocation" rel="nofollow noreferrer noopener" target="_blank">here</a>.</p>
<p dir="auto">This MR replaces the GMP <code>realloc()</code> and <code>free()</code> functions with safe alternatives that use
<code>explicit_bzero()</code> to zeroize any discarded memory.</p>
<p dir="auto">Feedback and ideas for improvement welcome</p>
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