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Save a temporary in BN_mod_exp_mont's w=1 case.

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BN_mod_exp_mont is most commonly used in RSA verification, where the exponent
sizes are small enough to use 1-bit "windows". There's no need to allocate the
extra BIGNUM.

Change-Id: I14fb523dfae7d77d2cec10a0209f09f22031d1af
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/35327
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2019-03-15 13:46:04 -05:00 committed by Adam Langley
parent 1c71844ef5
commit c93be52c9e
1 changed files with 4 additions and 3 deletions
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7
crypto/fipsmodule/bn/exponentiation.c
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@ -614,10 +614,9 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
BN_MONT_CTX *new_mont = NULL;
BN_CTX_start(ctx);
BIGNUM *d = BN_CTX_get(ctx);
BIGNUM *r = BN_CTX_get(ctx);
val[0] = BN_CTX_get(ctx);
if (!d || !r || !val[0]) {
if (r == NULL || val[0] == NULL) {
goto err;
}
@ -639,7 +638,9 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
goto err;
}
if (window > 1) {
if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) {
BIGNUM *d = BN_CTX_get(ctx);
if (d == NULL ||
!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) {
goto err;
}
for (int i = 1; i < 1 << (window - 1); i++) {