Mercurial > dropbear
view libtommath/bn_mp_rshd.c @ 1861:2b3a8026a6ce
Add re-exec for server
This allows ASLR to re-randomize the address
space for every connection, preventing some
vulnerabilities from being exploitable by
repeated probing.
Overhead (memory and time) is yet to be confirmed.
At present this is only enabled on Linux. Other BSD platforms
with fexecve() would probably also work though have not been tested.
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sun, 30 Jan 2022 10:14:56 +0800 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_MP_RSHD_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* shift right a certain amount of digits */ void mp_rshd(mp_int *a, int b) { int x; mp_digit *bottom, *top; /* if b <= 0 then ignore it */ if (b <= 0) { return; } /* if b > used then simply zero it and return */ if (a->used <= b) { mp_zero(a); return; } /* shift the digits down */ /* bottom */ bottom = a->dp; /* top [offset into digits] */ top = a->dp + b; /* this is implemented as a sliding window where * the window is b-digits long and digits from * the top of the window are copied to the bottom * * e.g. b-2 | b-1 | b0 | b1 | b2 | ... | bb | ----> /\ | ----> \-------------------/ ----> */ for (x = 0; x < (a->used - b); x++) { *bottom++ = *top++; } /* zero the top digits */ MP_ZERO_DIGITS(bottom, a->used - x); /* remove excess digits */ a->used -= b; } #endif