Mercurial > dropbear
view libtommath/bn_mp_montgomery_setup.c @ 1855:35d504d59c05
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]>
author | egor-duda <egor-duda@users.noreply.github.com> |
---|---|
date | Sat, 22 Jan 2022 16:53:04 +0300 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_MP_MONTGOMERY_SETUP_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* setups the montgomery reduction stuff */ mp_err mp_montgomery_setup(const mp_int *n, mp_digit *rho) { mp_digit x, b; /* fast inversion mod 2**k * * Based on the fact that * * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) * => 2*X*A - X*X*A*A = 1 * => 2*(1) - (1) = 1 */ b = n->dp[0]; if ((b & 1u) == 0u) { return MP_VAL; } x = (((b + 2u) & 4u) << 1) + b; /* here x*a==1 mod 2**4 */ x *= 2u - (b * x); /* here x*a==1 mod 2**8 */ #if !defined(MP_8BIT) x *= 2u - (b * x); /* here x*a==1 mod 2**16 */ #endif #if defined(MP_64BIT) || !(defined(MP_8BIT) || defined(MP_16BIT)) x *= 2u - (b * x); /* here x*a==1 mod 2**32 */ #endif #ifdef MP_64BIT x *= 2u - (b * x); /* here x*a==1 mod 2**64 */ #endif /* rho = -1/m mod b */ *rho = (mp_digit)(((mp_word)1 << (mp_word)MP_DIGIT_BIT) - x) & MP_MASK; return MP_OKAY; } #endif