Introduce soter_wipe() function #488
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Add a utility function to securely wipe memory region. We have quite a few places in our code where this can be useful, and it's a good function to export for the users (of Soter). It's implemented via OPENSSL_cleanse() function on both OpenSSL and BoringSSL. That's an old function available since OpenSSL 1.0.2 so we should not run into any compatibility issues (and we *do* recommend using latest OpenSSL anyway). Note that it intentionally accepts `void*`, not `uint8_t*` (just like free() does). Implicit cast is expected here and allow wiping any object without warnings from compiler.
Replace ad-hoc memset() calls with soter_wipe(). This ensures that these calls will not be optimized out by the compiler in release build mode.
ilammy
requested review from
Lagovas,
ignatk,
storojs72 and
vixentael
as code owners
ilammy
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vixentael
approved these changes
Jul 3, 2019
Lagovas
approved these changes
Jul 3, 2019
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It's a good security practice to wipe out sensitive data from memory once it's no longer needed. Straightforward approach to this is to call
memset(data, 0, size)before freeing the keys or something. However, compilers often optimize memset() implementation and end up optimizing out that call completely since they see that the data is freed. We can prevent that.Add a utility function to securely wipe memory region. We have quite a few places in our code where this can be useful, and it's a good function to export for the users (of Soter).
It's implemented via
OPENSSL_cleanse()function on both OpenSSL and BoringSSL. That's an old function available since OpenSSL 1.0.2 so we should not run into any compatibility issues (and we do recommend using latest OpenSSL anyway).Note that it intentionally accepts
void*, notuint8_t*(just like free() does). Implicit cast is expected here and allow wiping any object without warnings from compiler.Replace ad-hoc memset() calls with soter_wipe(). This ensures that these calls will not be optimized out by the compiler in release build mode.