Mercurial > dropbear
view libtommath/bn_fast_s_mp_mul_high_digs.c @ 1665:7c17995bcdfb
Improve address logging on early exit messages (#83)
Change 'Early exit' and 'Exit before auth' messages to include the IP
address & port as part of the message.
This allows log scanning utilities such as 'fail2ban' to obtain the
offending IP address as part of the failure event instead of extracting
the PID from the message and then scanning the log again for match
'child connection from' messages
Signed-off-by: Kevin Darbyshire-Bryant <[email protected]>
author | Kevin Darbyshire-Bryant <6500011+ldir-EDB0@users.noreply.github.com> |
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date | Wed, 18 Mar 2020 15:28:56 +0000 |
parents | f52919ffd3b1 |
children |
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#include "tommath_private.h" #ifdef BN_FAST_S_MP_MUL_HIGH_DIGS_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is a library that provides multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library was designed directly after the MPI library by * Michael Fromberger but has been written from scratch with * additional optimizations in place. * * SPDX-License-Identifier: Unlicense */ /* this is a modified version of fast_s_mul_digs that only produces * output digits *above* digs. See the comments for fast_s_mul_digs * to see how it works. * * This is used in the Barrett reduction since for one of the multiplications * only the higher digits were needed. This essentially halves the work. * * Based on Algorithm 14.12 on pp.595 of HAC. */ int fast_s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs) { int olduse, res, pa, ix, iz; mp_digit W[MP_WARRAY]; mp_word _W; /* grow the destination as required */ pa = a->used + b->used; if (c->alloc < pa) { if ((res = mp_grow(c, pa)) != MP_OKAY) { return res; } } /* number of output digits to produce */ pa = a->used + b->used; _W = 0; for (ix = digs; ix < pa; ix++) { int tx, ty, iy; mp_digit *tmpx, *tmpy; /* get offsets into the two bignums */ ty = MIN(b->used-1, ix); tx = ix - ty; /* setup temp aliases */ tmpx = a->dp + tx; tmpy = b->dp + ty; /* this is the number of times the loop will iterrate, essentially its while (tx++ < a->used && ty-- >= 0) { ... } */ iy = MIN(a->used-tx, ty+1); /* execute loop */ for (iz = 0; iz < iy; iz++) { _W += (mp_word)*tmpx++ * (mp_word)*tmpy--; } /* store term */ W[ix] = (mp_digit)_W & MP_MASK; /* make next carry */ _W = _W >> (mp_word)DIGIT_BIT; } /* setup dest */ olduse = c->used; c->used = pa; { mp_digit *tmpc; tmpc = c->dp + digs; for (ix = digs; ix < pa; ix++) { /* now extract the previous digit [below the carry] */ *tmpc++ = W[ix]; } /* clear unused digits [that existed in the old copy of c] */ for (; ix < olduse; ix++) { *tmpc++ = 0; } } mp_clamp(c); return MP_OKAY; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */