diff options
author | Stefan Metzmacher <metze@samba.org> | 2022-01-19 13:15:45 +0100 |
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committer | Joseph Sutton <jsutton@samba.org> | 2022-01-19 21:41:59 +0000 |
commit | 7055827b8ffd3823c1240ba3f0b619dd6068cd51 (patch) | |
tree | abb14aa7455bde7b1b33b706123c57ccfc28fcaa /third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c | |
parent | 1954e50f266256c9e153c9613f49f9d9f5dbf67b (diff) | |
download | samba-7055827b8ffd3823c1240ba3f0b619dd6068cd51.tar.gz |
HEIMDAL: move code from source4/heimdal* to third_party/heimdal*
This makes it clearer that we always want to do heimdal changes
via the lorikeet-heimdal repository.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Autobuild-User(master): Joseph Sutton <jsutton@samba.org>
Autobuild-Date(master): Wed Jan 19 21:41:59 UTC 2022 on sn-devel-184
Diffstat (limited to 'third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c')
-rw-r--r-- | third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c new file mode 100644 index 00000000000..682ded84505 --- /dev/null +++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_s_mp_exptmod_fast.c @@ -0,0 +1,254 @@ +#include "tommath_private.h" +#ifdef BN_S_MP_EXPTMOD_FAST_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +/* computes Y == G**X mod P, HAC pp.616, Algorithm 14.85 + * + * Uses a left-to-right k-ary sliding window to compute the modular exponentiation. + * The value of k changes based on the size of the exponent. + * + * Uses Montgomery or Diminished Radix reduction [whichever appropriate] + */ + +#ifdef MP_LOW_MEM +# define TAB_SIZE 32 +# define MAX_WINSIZE 5 +#else +# define TAB_SIZE 256 +# define MAX_WINSIZE 0 +#endif + +mp_err s_mp_exptmod_fast(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y, int redmode) +{ + mp_int M[TAB_SIZE], res; + mp_digit buf, mp; + int bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize; + mp_err err; + + /* use a pointer to the reduction algorithm. This allows us to use + * one of many reduction algorithms without modding the guts of + * the code with if statements everywhere. + */ + mp_err(*redux)(mp_int *x, const mp_int *n, mp_digit rho); + + /* find window size */ + x = mp_count_bits(X); + if (x <= 7) { + winsize = 2; + } else if (x <= 36) { + winsize = 3; + } else if (x <= 140) { + winsize = 4; + } else if (x <= 450) { + winsize = 5; + } else if (x <= 1303) { + winsize = 6; + } else if (x <= 3529) { + winsize = 7; + } else { + winsize = 8; + } + + winsize = MAX_WINSIZE ? MP_MIN(MAX_WINSIZE, winsize) : winsize; + + /* init M array */ + /* init first cell */ + if ((err = mp_init_size(&M[1], P->alloc)) != MP_OKAY) { + return err; + } + + /* now init the second half of the array */ + for (x = 1<<(winsize-1); x < (1 << winsize); x++) { + if ((err = mp_init_size(&M[x], P->alloc)) != MP_OKAY) { + for (y = 1<<(winsize-1); y < x; y++) { + mp_clear(&M[y]); + } + mp_clear(&M[1]); + return err; + } + } + + /* determine and setup reduction code */ + if (redmode == 0) { + if (MP_HAS(MP_MONTGOMERY_SETUP)) { + /* now setup montgomery */ + if ((err = mp_montgomery_setup(P, &mp)) != MP_OKAY) goto LBL_M; + } else { + err = MP_VAL; + goto LBL_M; + } + + /* automatically pick the comba one if available (saves quite a few calls/ifs) */ + if (MP_HAS(S_MP_MONTGOMERY_REDUCE_FAST) && + (((P->used * 2) + 1) < MP_WARRAY) && + (P->used < MP_MAXFAST)) { + redux = s_mp_montgomery_reduce_fast; + } else if (MP_HAS(MP_MONTGOMERY_REDUCE)) { + /* use slower baseline Montgomery method */ + redux = mp_montgomery_reduce; + } else { + err = MP_VAL; + goto LBL_M; + } + } else if (redmode == 1) { + if (MP_HAS(MP_DR_SETUP) && MP_HAS(MP_DR_REDUCE)) { + /* setup DR reduction for moduli of the form B**k - b */ + mp_dr_setup(P, &mp); + redux = mp_dr_reduce; + } else { + err = MP_VAL; + goto LBL_M; + } + } else if (MP_HAS(MP_REDUCE_2K_SETUP) && MP_HAS(MP_REDUCE_2K)) { + /* setup DR reduction for moduli of the form 2**k - b */ + if ((err = mp_reduce_2k_setup(P, &mp)) != MP_OKAY) goto LBL_M; + redux = mp_reduce_2k; + } else { + err = MP_VAL; + goto LBL_M; + } + + /* setup result */ + if ((err = mp_init_size(&res, P->alloc)) != MP_OKAY) goto LBL_M; + + /* create M table + * + + * + * The first half of the table is not computed though accept for M[0] and M[1] + */ + + if (redmode == 0) { + if (MP_HAS(MP_MONTGOMERY_CALC_NORMALIZATION)) { + /* now we need R mod m */ + if ((err = mp_montgomery_calc_normalization(&res, P)) != MP_OKAY) goto LBL_RES; + + /* now set M[1] to G * R mod m */ + if ((err = mp_mulmod(G, &res, P, &M[1])) != MP_OKAY) goto LBL_RES; + } else { + err = MP_VAL; + goto LBL_RES; + } + } else { + mp_set(&res, 1uL); + if ((err = mp_mod(G, P, &M[1])) != MP_OKAY) goto LBL_RES; + } + + /* compute the value at M[1<<(winsize-1)] by squaring M[1] (winsize-1) times */ + if ((err = mp_copy(&M[1], &M[(size_t)1 << (winsize - 1)])) != MP_OKAY) goto LBL_RES; + + for (x = 0; x < (winsize - 1); x++) { + if ((err = mp_sqr(&M[(size_t)1 << (winsize - 1)], &M[(size_t)1 << (winsize - 1)])) != MP_OKAY) goto LBL_RES; + if ((err = redux(&M[(size_t)1 << (winsize - 1)], P, mp)) != MP_OKAY) goto LBL_RES; + } + + /* create upper table */ + for (x = (1 << (winsize - 1)) + 1; x < (1 << winsize); x++) { + if ((err = mp_mul(&M[x - 1], &M[1], &M[x])) != MP_OKAY) goto LBL_RES; + if ((err = redux(&M[x], P, mp)) != MP_OKAY) goto LBL_RES; + } + + /* set initial mode and bit cnt */ + mode = 0; + bitcnt = 1; + buf = 0; + digidx = X->used - 1; + bitcpy = 0; + bitbuf = 0; + + for (;;) { + /* grab next digit as required */ + if (--bitcnt == 0) { + /* if digidx == -1 we are out of digits so break */ + if (digidx == -1) { + break; + } + /* read next digit and reset bitcnt */ + buf = X->dp[digidx--]; + bitcnt = (int)MP_DIGIT_BIT; + } + + /* grab the next msb from the exponent */ + y = (mp_digit)(buf >> (MP_DIGIT_BIT - 1)) & 1uL; + buf <<= (mp_digit)1; + + /* if the bit is zero and mode == 0 then we ignore it + * These represent the leading zero bits before the first 1 bit + * in the exponent. Technically this opt is not required but it + * does lower the # of trivial squaring/reductions used + */ + if ((mode == 0) && (y == 0)) { + continue; + } + + /* if the bit is zero and mode == 1 then we square */ + if ((mode == 1) && (y == 0)) { + if ((err = mp_sqr(&res, &res)) != MP_OKAY) goto LBL_RES; + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + continue; + } + + /* else we add it to the window */ + bitbuf |= (y << (winsize - ++bitcpy)); + mode = 2; + + if (bitcpy == winsize) { + /* ok window is filled so square as required and multiply */ + /* square first */ + for (x = 0; x < winsize; x++) { + if ((err = mp_sqr(&res, &res)) != MP_OKAY) goto LBL_RES; + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + } + + /* then multiply */ + if ((err = mp_mul(&res, &M[bitbuf], &res)) != MP_OKAY) goto LBL_RES; + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + + /* empty window and reset */ + bitcpy = 0; + bitbuf = 0; + mode = 1; + } + } + + /* if bits remain then square/multiply */ + if ((mode == 2) && (bitcpy > 0)) { + /* square then multiply if the bit is set */ + for (x = 0; x < bitcpy; x++) { + if ((err = mp_sqr(&res, &res)) != MP_OKAY) goto LBL_RES; + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + + /* get next bit of the window */ + bitbuf <<= 1; + if ((bitbuf & (1 << winsize)) != 0) { + /* then multiply */ + if ((err = mp_mul(&res, &M[1], &res)) != MP_OKAY) goto LBL_RES; + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + } + } + } + + if (redmode == 0) { + /* fixup result if Montgomery reduction is used + * recall that any value in a Montgomery system is + * actually multiplied by R mod n. So we have + * to reduce one more time to cancel out the factor + * of R. + */ + if ((err = redux(&res, P, mp)) != MP_OKAY) goto LBL_RES; + } + + /* swap res with Y */ + mp_exch(&res, Y); + err = MP_OKAY; +LBL_RES: + mp_clear(&res); +LBL_M: + mp_clear(&M[1]); + for (x = 1<<(winsize-1); x < (1 << winsize); x++) { + mp_clear(&M[x]); + } + return err; +} +#endif |