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Prevent mpi_mod_write from corrupting the input

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Allocate a working buffer to store the converted value needed for the
mpi_mod_write function.

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
This commit is contained in:
Gabor Mezei 2023-03-27 15:49:24 +02:00
parent 0048d15036
commit 2f73edbbc4
No known key found for this signature in database
GPG key ID: F072ACA227ACD71D
1 changed files with 25 additions and 17 deletions
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42
library/bignum_mod.c
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@ -383,38 +383,46 @@ int mbedtls_mpi_mod_write(const mbedtls_mpi_mod_residue *r,
size_t buflen, size_t buflen,
mbedtls_mpi_mod_ext_rep ext_rep) mbedtls_mpi_mod_ext_rep ext_rep)
{ {
int ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
/* Do our best to check if r and m have been set up */ /* Do our best to check if r and m have been set up */
if (r->limbs == 0 || N->limbs == 0) { if (r->limbs == 0 || N->limbs == 0) {
goto cleanup; return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
} }
if (r->limbs != N->limbs) { if (r->limbs != N->limbs) {
return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
}
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi_uint *working_memory = r->p;
size_t working_memory_len = sizeof(mbedtls_mpi_uint) * r->limbs;
if (N->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY) {
working_memory = mbedtls_calloc(r->limbs, sizeof(mbedtls_mpi_uint));
if (working_memory == NULL) {
ret = MBEDTLS_ERR_MPI_ALLOC_FAILED;
goto cleanup; goto cleanup;
} }
if (N->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY) { memcpy(working_memory, r->p, working_memory_len);
ret = mbedtls_mpi_mod_raw_from_mont_rep(r->p, N);
ret = mbedtls_mpi_mod_raw_from_mont_rep(working_memory, N);
if (ret != 0) { if (ret != 0) {
goto cleanup; goto cleanup;
} }
} }
ret = mbedtls_mpi_mod_raw_write(r->p, N, buf, buflen, ext_rep); ret = mbedtls_mpi_mod_raw_write(working_memory, N, buf, buflen, ext_rep);
if (N->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY) {
/* If this fails, the value of r is corrupted and we want to return
* this error (as opposed to the error code from the write above) to
* let the caller know. If it succeeds, we want to return the error
* code from write above. */
int conv_ret = mbedtls_mpi_mod_raw_to_mont_rep(r->p, N);
if (ret == 0) {
ret = conv_ret;
}
}
cleanup: cleanup:
if (N->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY &&
working_memory != NULL) {
mbedtls_platform_zeroize(working_memory, working_memory_len);
mbedtls_free(working_memory);
}
return ret; return ret;
} }
/* END MERGE SLOT 7 */ /* END MERGE SLOT 7 */