Le 16/11/2021 à 12:20, Sandy Harris a écrit :
Fairly often we want to clear some memory in crypto code; it holds things we are done using and do not want to leave lying around where an enemy might discover them. Typical examples are crypto keys or random numbers we have generated and used for output. The obvious way to do this is with memset(address,0,bytes) but there is a problem with that; because we are done using that memory, the compiler may optimise away the "useless" memset() call. Using memzero_explicit(address,bytes) instead solves the problem; that function is designed to resist the optimisation. There are well over 100 memset() calls in .c files in the crypto and security directories. I looked at them all and found about a dozen in eight files that I thought should be changed to memzero_explicit(). Here they are as patches 1 to 8 in this series. I did read some code & think moderately carefully, but I do not know the code deeply & it is possible I have made some errors. I think false positives (making unnecessary changes) are more likely than false negatives (not catching necessary changes).
I see no point in doing 8 separate patches that all have the same subject and the exact same light description.
I think it would be better to have a single patch with all the changes, and use the cover letter description as description for that patch.
Christophe
