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

/* computes b = a*a */
mp_err mp_sqr(const mp_int *a, mp_int *b)
{
   mp_err err;
   if (MP_HAS(S_MP_TOOM_SQR) && /* use Toom-Cook? */
       (a->used >= MP_TOOM_SQR_CUTOFF)) {
      err = s_mp_toom_sqr(a, b);
   } else if (MP_HAS(S_MP_KARATSUBA_SQR) &&  /* Karatsuba? */
              (a->used >= MP_KARATSUBA_SQR_CUTOFF)) {
      err = s_mp_karatsuba_sqr(a, b);
   } else if (MP_HAS(S_MP_SQR_FAST) && /* can we use the fast comba multiplier? */
              (((a->used * 2) + 1) < MP_WARRAY) &&
              (a->used < (MP_MAXFAST / 2))) {
      err = s_mp_sqr_fast(a, b);
   } else if (MP_HAS(S_MP_SQR)) {
      err = s_mp_sqr(a, b);
   } else {
      err = MP_VAL;
   }
   b->sign = MP_ZPOS;
   return err;
}
#endif