Implement server-side support for sk-ecdsa U2F-backed keys (#142) * Implement server-side support for sk-ecdsa U2F-backed keys * Fix out-of-bounds read on normal ecdsa-sha2-[identifier] keys * Fix one more potential out-of-bounds read * Check if nistp256 curve is used in sk-ecdsa-sha2- key It's the only allowed curve per PROTOCOL.u2f specification * Implement server-side support for sk-ed25519 FIDO2-backed keys * Keys with type sk-* make no sense as host keys, so they should be disabled * fix typo * Make sk-ecdsa call buf_ecdsa_verify This reduces code duplication, the SK code just handles the different message format. * Reduce sk specific code The application id can be stored in signkey, then we don't need to call sk-specific functions from svr-authpubkey * Remove debugging output, which causes compilation errors with DEBUG_TRACE disabled * Proper cleanup of sk_app Co-authored-by: Matt Johnston <[email protected]>

#include "tommath_private.h"
#ifdef BN_MP_SHRINK_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* shrink a bignum */
mp_err mp_shrink(mp_int *a)
{
   mp_digit *tmp;
   int alloc = MP_MAX(MP_MIN_PREC, a->used);
   if (a->alloc != alloc) {
      if ((tmp = (mp_digit *) MP_REALLOC(a->dp,
                                         (size_t)a->alloc * sizeof(mp_digit),
                                         (size_t)alloc * sizeof(mp_digit))) == NULL) {
         return MP_MEM;
      }
      a->dp    = tmp;
      a->alloc = alloc;
   }
   return MP_OKAY;
}
#endif