Mercurial > dropbear
view libtommath/bn_mp_is_square.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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line source
#include "tommath_private.h" #ifdef BN_MP_IS_SQUARE_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* Check if remainders are possible squares - fast exclude non-squares */ static const char rem_128[128] = { 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1 }; static const char rem_105[105] = { 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1 }; /* Store non-zero to ret if arg is square, and zero if not */ mp_err mp_is_square(const mp_int *arg, mp_bool *ret) { mp_err err; mp_digit c; mp_int t; unsigned long r; /* Default to Non-square :) */ *ret = MP_NO; if (arg->sign == MP_NEG) { return MP_VAL; } if (MP_IS_ZERO(arg)) { return MP_OKAY; } /* First check mod 128 (suppose that MP_DIGIT_BIT is at least 7) */ if (rem_128[127u & arg->dp[0]] == (char)1) { return MP_OKAY; } /* Next check mod 105 (3*5*7) */ if ((err = mp_mod_d(arg, 105uL, &c)) != MP_OKAY) { return err; } if (rem_105[c] == (char)1) { return MP_OKAY; } if ((err = mp_init_u32(&t, 11u*13u*17u*19u*23u*29u*31u)) != MP_OKAY) { return err; } if ((err = mp_mod(arg, &t, &t)) != MP_OKAY) { goto LBL_ERR; } r = mp_get_u32(&t); /* Check for other prime modules, note it's not an ERROR but we must * free "t" so the easiest way is to goto LBL_ERR. We know that err * is already equal to MP_OKAY from the mp_mod call */ if (((1uL<<(r%11uL)) & 0x5C4uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%13uL)) & 0x9E4uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%17uL)) & 0x5CE8uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%19uL)) & 0x4F50CuL) != 0uL) goto LBL_ERR; if (((1uL<<(r%23uL)) & 0x7ACCA0uL) != 0uL) goto LBL_ERR; if (((1uL<<(r%29uL)) & 0xC2EDD0CuL) != 0uL) goto LBL_ERR; if (((1uL<<(r%31uL)) & 0x6DE2B848uL) != 0uL) goto LBL_ERR; /* Final check - is sqr(sqrt(arg)) == arg ? */ if ((err = mp_sqrt(arg, &t)) != MP_OKAY) { goto LBL_ERR; } if ((err = mp_sqr(&t, &t)) != MP_OKAY) { goto LBL_ERR; } *ret = (mp_cmp_mag(&t, arg) == MP_EQ) ? MP_YES : MP_NO; LBL_ERR: mp_clear(&t); return err; } #endif