Mercurial > dropbear
view libtommath/bn_mp_dr_reduce.c @ 1629:258b57b208ae
Fix for issue successfull login of disabled user (#78)
This commit introduces fix for scenario:
1. Root login disabled on dropbear
2. PAM authentication model enabled
While login as root user, after prompt for password
user is being notified about login failrue, but
after second attempt of prompt for password within
same session, login becames succesfull.
Signed-off-by: Pawel Rapkiewicz <[email protected]>
author | vincentto13 <33652988+vincentto13@users.noreply.github.com> |
---|---|
date | Wed, 20 Mar 2019 15:03:40 +0100 |
parents | 8bba51a55704 |
children | f52919ffd3b1 |
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#include <tommath_private.h> #ifdef BN_MP_DR_REDUCE_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. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, [email protected], http://libtom.org */ /* reduce "x" in place modulo "n" using the Diminished Radix algorithm. * * Based on algorithm from the paper * * "Generating Efficient Primes for Discrete Log Cryptosystems" * Chae Hoon Lim, Pil Joong Lee, * POSTECH Information Research Laboratories * * The modulus must be of a special format [see manual] * * Has been modified to use algorithm 7.10 from the LTM book instead * * Input x must be in the range 0 <= x <= (n-1)**2 */ int mp_dr_reduce (mp_int * x, mp_int * n, mp_digit k) { int err, i, m; mp_word r; mp_digit mu, *tmpx1, *tmpx2; /* m = digits in modulus */ m = n->used; /* ensure that "x" has at least 2m digits */ if (x->alloc < (m + m)) { if ((err = mp_grow (x, m + m)) != MP_OKAY) { return err; } } /* top of loop, this is where the code resumes if * another reduction pass is required. */ top: /* aliases for digits */ /* alias for lower half of x */ tmpx1 = x->dp; /* alias for upper half of x, or x/B**m */ tmpx2 = x->dp + m; /* set carry to zero */ mu = 0; /* compute (x mod B**m) + k * [x/B**m] inline and inplace */ for (i = 0; i < m; i++) { r = (((mp_word)*tmpx2++) * (mp_word)k) + *tmpx1 + mu; *tmpx1++ = (mp_digit)(r & MP_MASK); mu = (mp_digit)(r >> ((mp_word)DIGIT_BIT)); } /* set final carry */ *tmpx1++ = mu; /* zero words above m */ for (i = m + 1; i < x->used; i++) { *tmpx1++ = 0; } /* clamp, sub and return */ mp_clamp (x); /* if x >= n then subtract and reduce again * Each successive "recursion" makes the input smaller and smaller. */ if (mp_cmp_mag (x, n) != MP_LT) { if ((err = s_mp_sub(x, n, x)) != MP_OKAY) { return err; } goto top; } return MP_OKAY; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */