Hi Tudor, On Thu, Nov 02, 2017 at 12:55:56PM +0200, Tudor Ambarus wrote: > Hi, Eric, > > On 11/02/2017 12:25 AM, Eric Biggers wrote: > >When setting the secret with the software Diffie-Hellman implementation, > >if allocating 'g' failed (e.g. if it was longer than > >MAX_EXTERN_MPI_BITS), then 'p' was freed twice: once immediately, and > >once later when the crypto_kpp tfm was destroyed. Fix it by using > >dh_free_ctx() in the error paths, as that sets the pointers to NULL. > > Other solution would be to have just an one-line patch that sets p to > NULL after freeing it. The benefit of just setting p to NULL and not > using dh_free_ctx() is that you'll spare some cpu cycles. If g fails, > g and a will already be NULL, so freeing them and set them to NULL is > redundant. > > However, if you decide to always use dh_free_ctx(), you'll have to get > rid of dh_clear_params(), because it will be used just in dh_free_ctx(). > You can copy dh_clear_params() body to dh_free_ctx(). >
This is on an error path, so a few cycles don't matter. I would much rather have the simpler code, with less chance to introduce exploitable bugs. Yes, I should inline dh_clear_params() into dh_free_ctx(). Eric
