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_REDUCE_2K_SETUP_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* determines the setup value */
mp_err mp_reduce_2k_setup(const mp_int *a, mp_digit *d)
{
   mp_err err;
   mp_int tmp;
   int    p;

   if ((err = mp_init(&tmp)) != MP_OKAY) {
      return err;
   }

   p = mp_count_bits(a);
   if ((err = mp_2expt(&tmp, p)) != MP_OKAY) {
      mp_clear(&tmp);
      return err;
   }

   if ((err = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
      mp_clear(&tmp);
      return err;
   }

   *d = tmp.dp[0];
   mp_clear(&tmp);
   return MP_OKAY;
}
#endif