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Exp mod: tidy up temporary storage allocation

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Signed-off-by: Janos Follath <janos.follath@arm.com>
This commit is contained in:
Janos Follath 2024-02-21 09:26:36 +00:00
parent 0512d178e0
commit 424c2655b9
1 changed files with 13 additions and 12 deletions
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25
library/bignum.c
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@ -1624,10 +1624,17 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
return ret;
}
/*
* Allocate working memory for mbedtls_mpi_core_exp_mod()
*/
size_t T_limbs = mbedtls_mpi_core_exp_mod_working_limbs(N->n, E->n);
mbedtls_mpi_uint *T = (mbedtls_mpi_uint*) mbedtls_calloc(T_limbs, sizeof(mbedtls_mpi_uint));
if (T == NULL) {
return MBEDTLS_ERR_MPI_ALLOC_FAILED;
}
mbedtls_mpi RR;
mbedtls_mpi_init(&RR);
mbedtls_mpi T;
mbedtls_mpi_init(&T);
/*
* If 1st call, pre-compute R^2 mod N
@ -1669,20 +1676,14 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
}
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(X, N->n));
/*
* Allocate working memory for mbedtls_mpi_core_exp_mod()
*/
size_t T_limbs = mbedtls_mpi_core_exp_mod_working_limbs(N->n, E->n);
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&T, T_limbs));
/*
* Convert to and from Montgomery around mbedtls_mpi_core_exp_mod().
*/
mbedtls_mpi_uint mm = mbedtls_mpi_core_montmul_init(N->p);
mbedtls_mpi_core_to_mont_rep(X->p, X->p, N->p, N->n, mm, RR.p, T.p);
mbedtls_mpi_core_to_mont_rep(X->p, X->p, N->p, N->n, mm, RR.p, T);
mbedtls_mpi_core_exp_mod(X->p, X->p, N->p, N->n, E->p, E->n, RR.p,
T.p);
mbedtls_mpi_core_from_mont_rep(X->p, X->p, N->p, N->n, mm, T.p);
T);
mbedtls_mpi_core_from_mont_rep(X->p, X->p, N->p, N->n, mm, T);
/*
* Correct for negative A.
@ -1694,7 +1695,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
cleanup:
mbedtls_mpi_free(&T);
mbedtls_mpi_zeroize_and_free(T, T_limbs);
if (prec_RR == NULL || prec_RR->p == NULL) {
mbedtls_mpi_free(&RR);