openssl/crypto/include/internal/bn_int.h
Andy Polyakov 8df98cd988 bn/bn_{div|shift}.c: introduce fixed-top interfaces.
Fixed-top interfaces tolerate zero-padded inputs and facilitate
constant-time-ness. bn_div_fixed_top tolerates zero-padded dividend,
but not divisor. It's argued that divisor's length is public even
when value is secret.

[extended tests]

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7589)

(cherry picked from commit 3a4a88f436)
2018-12-05 10:38:22 +00:00

90 lines
3.4 KiB
C

/*
* Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#ifndef HEADER_BN_INT_H
# define HEADER_BN_INT_H
# include <openssl/bn.h>
# include <limits.h>
BIGNUM *bn_wexpand(BIGNUM *a, int words);
BIGNUM *bn_expand2(BIGNUM *a, int words);
void bn_correct_top(BIGNUM *a);
/*
* Determine the modified width-(w+1) Non-Adjacent Form (wNAF) of 'scalar'.
* This is an array r[] of values that are either zero or odd with an
* absolute value less than 2^w satisfying scalar = \sum_j r[j]*2^j where at
* most one of any w+1 consecutive digits is non-zero with the exception that
* the most significant digit may be only w-1 zeros away from that next
* non-zero digit.
*/
signed char *bn_compute_wNAF(const BIGNUM *scalar, int w, size_t *ret_len);
int bn_get_top(const BIGNUM *a);
int bn_get_dmax(const BIGNUM *a);
/* Set all words to zero */
void bn_set_all_zero(BIGNUM *a);
/*
* Copy the internal BIGNUM words into out which holds size elements (and size
* must be bigger than top)
*/
int bn_copy_words(BN_ULONG *out, const BIGNUM *in, int size);
BN_ULONG *bn_get_words(const BIGNUM *a);
/*
* Set the internal data words in a to point to words which contains size
* elements. The BN_FLG_STATIC_DATA flag is set
*/
void bn_set_static_words(BIGNUM *a, const BN_ULONG *words, int size);
/*
* Copy words into the BIGNUM |a|, reallocating space as necessary.
* The negative flag of |a| is not modified.
* Returns 1 on success and 0 on failure.
*/
/*
* |num_words| is int because bn_expand2 takes an int. This is an internal
* function so we simply trust callers not to pass negative values.
*/
int bn_set_words(BIGNUM *a, const BN_ULONG *words, int num_words);
/*
* Some BIGNUM functions assume most significant limb to be non-zero, which
* is customarily arranged by bn_correct_top. Output from below functions
* is not processed with bn_correct_top, and for this reason it may not be
* returned out of public API. It may only be passed internally into other
* functions known to support non-minimal or zero-padded BIGNUMs. Even
* though the goal is to facilitate constant-time-ness, not each subroutine
* is constant-time by itself. They all have pre-conditions, consult source
* code...
*/
int bn_mul_mont_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
BN_MONT_CTX *mont, BN_CTX *ctx);
int bn_to_mont_fixed_top(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
BN_CTX *ctx);
int bn_from_mont_fixed_top(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
BN_CTX *ctx);
int bn_mod_add_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
const BIGNUM *m);
int bn_mod_sub_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
const BIGNUM *m);
int bn_mul_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
int bn_sqr_fixed_top(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx);
int bn_lshift_fixed_top(BIGNUM *r, const BIGNUM *a, int n);
int bn_rshift_fixed_top(BIGNUM *r, const BIGNUM *a, int n);
int bn_div_fixed_top(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m,
const BIGNUM *d, BN_CTX *ctx);
#endif