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Adjust mpi_gcd_modinv_odd() internals

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Signed-off-by: Felix Conway <felix.conway@arm.com>
This commit is contained in:
Felix Conway
2025-08-06 09:54:11 +01:00
parent 49a2bc4750
commit a1c95e378a
1 changed files with 11 additions and 8 deletions
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19
library/bignum.c
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@@ -1774,11 +1774,11 @@ int mbedtls_mpi_gcd_modinv_odd(mbedtls_mpi *G,
G = &local_g;
}
/* We can't modify the values of G or I before use in the main function,
* as they could be aliased to A or N. */
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(G, N->n));
G->s = 1;
if (I != NULL) {
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(I, N->n));
I->s = 1;
}
T = mbedtls_calloc(sizeof(mbedtls_mpi_uint) * N->n, T_factor);
@@ -1787,16 +1787,19 @@ int mbedtls_mpi_gcd_modinv_odd(mbedtls_mpi *G,
goto cleanup;
}
/* We have to handle G and I carefully as they could be aliased
* to A or N. */
mbedtls_mpi_uint *Ip = I != NULL ? I->p : NULL;
/* If A is 0 (null), then A->p would be null, which would be an issue if
* A->p was passed to mbedtls_mpi_core_gcd_modinv_odd below. */
/* If A is 0 (null), then A->p would be null, and A->n would be 0,
* which would be an issue if A->p and A->n were passed to
* mbedtls_mpi_core_gcd_modinv_odd below. */
const mbedtls_mpi_uint *Ap = A->p != NULL ? A->p : &zero;
size_t An = A->p == NULL ? 0 : A->n;
An = A->n <= N->n ? A->n : N->n;
size_t An = A->n >= N->n ? N->n : A->p != NULL ? A->n : 1;
mbedtls_mpi_core_gcd_modinv_odd(G->p, Ip, Ap, An, N->p, N->n, T);
G->s = 1;
if (I != NULL) {
I->s = 1;
}
if (G->n > N->n) {
memset(G->p + N->n, 0, ciL * (G->n - N->n));
}