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ecp: align mbedtls_ecp_mod_p448_raw() with others

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The size checks were wrong, and the removed comment was misleading:
this is not about tests, it's just the normal way to wrap a "new bignum"
(aka "raw") function, that expects a fixed number of limbs, to a "legacy
bignum" function, that accepts any size (and allocates).

Also, this aligns ecp_mod_p448() and mbedtls_ecp_mod_p448_raw() with all
other ecp_mod_pXXX() and mbedtls_ecp_mod_pXXX_raw() functions.

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>
This commit is contained in:
Manuel Pégourié-Gonnard
2026-05-18 10:45:11 +02:00
parent 0f8a09a99c
commit 83ed698713
1 changed files with 2 additions and 15 deletions
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library/ecp_curves.c
+2 -15
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@@ -5476,14 +5476,8 @@ static int ecp_mod_p448(mbedtls_mpi *N)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t expected_width = BITS_TO_LIMBS(448) * 2;
/* This is required as some tests and use cases do not pass in a Bignum of
* the correct size, and expect the growth to be done automatically, which
* will no longer happen. */
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
ret = mbedtls_ecp_mod_p448_raw(N->p, N->n);
ret = mbedtls_ecp_mod_p448_raw(N->p, expected_width);
cleanup:
return ret;
}
@@ -5506,18 +5500,11 @@ int mbedtls_ecp_mod_p448_raw(mbedtls_mpi_uint *X, size_t X_limbs)
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if (X_limbs != BITS_TO_LIMBS(448) * 2) {
return 0;
}
size_t M_limbs = X_limbs - (P448_WIDTH);
if (M_limbs > P448_WIDTH) {
/* Shouldn't be called with X larger than 2^896! */
return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
}
/* Both M and Q require an extra limb to catch carries. */
M_limbs++;
size_t M_limbs = BITS_TO_LIMBS(448) + 1;
const size_t Q_limbs = M_limbs;
mbedtls_mpi_uint *M = NULL;