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psa: let mbedtls_ecc_group_from_psa() accept only exact bit lengths

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Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
This commit is contained in:
Valerio Setti 2023-12-29 11:46:44 +01:00
parent dc33200b74
commit 0e608807e3
3 changed files with 17 additions and 24 deletions
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9
include/mbedtls/psa_util.h
View file

@ -126,16 +126,11 @@ psa_ecc_family_t mbedtls_ecc_group_to_psa(mbedtls_ecp_group_id grpid,
* \param curve A PSA elliptic curve identifier
* (`PSA_ECC_FAMILY_xxx`).
* \param bits The bit-length of a private key on \p curve.
* \param bits_is_sloppy If true, \p bits may be the bit-length rounded up
* to the nearest multiple of 8. This allows the caller
* to infer the exact curve from the length of a key
* which is supplied as a byte string.
*
* \return The corresponding Mbed TLS elliptic curve identifier
* (`MBEDTLS_ECP_DP_xxx`).
* \return #MBEDTLS_ECP_DP_NONE if \c curve is not recognized.
* \return #MBEDTLS_ECP_DP_NONE if \p bits is not
* correct for \p curve.
* \return #MBEDTLS_ECP_DP_NONE if the combination of \c curve
* and \p bits is not recognized.
*/
mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t curve,
size_t bits);

30
library/psa_crypto_ecp.c
View file

@ -32,13 +32,16 @@
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH)
/* Helper function to verify if the provided EC's family and key bit size are
* valid. */
static int check_ecc_parameters(psa_ecc_family_t family, size_t bits, int allow_bit_size_roundup)
/* Helper function to verify if the provided EC's family and key bit size are valid.
*
* Note: "bits" parameter is used both as input and output and it might be updated
* in case provided input value is not multiple of 8 ("sloppy" bits).
*/
static int check_ecc_parameters(psa_ecc_family_t family, size_t *bits)
{
switch (family) {
case PSA_ECC_FAMILY_SECP_R1:
switch (bits) {
switch (*bits) {
case 192:
case 224:
case 256:
@ -46,14 +49,13 @@ static int check_ecc_parameters(psa_ecc_family_t family, size_t bits, int allow_
case 521:
return PSA_SUCCESS;
case 528:
if (allow_bit_size_roundup) {
return PSA_SUCCESS;
}
*bits = 521;
return PSA_SUCCESS;
}
break;
case PSA_ECC_FAMILY_BRAINPOOL_P_R1:
switch (bits) {
switch (*bits) {
case 256:
case 384:
case 512:
@ -62,19 +64,18 @@ static int check_ecc_parameters(psa_ecc_family_t family, size_t bits, int allow_
break;
case PSA_ECC_FAMILY_MONTGOMERY:
switch (bits) {
switch (*bits) {
case 448:
case 255:
return PSA_SUCCESS;
case 256:
if (allow_bit_size_roundup) {
return PSA_SUCCESS;
}
*bits = 255;
return PSA_SUCCESS;
}
break;
case PSA_ECC_FAMILY_SECP_K1:
switch (bits) {
switch (*bits) {
case 192:
case 224:
case 256:
@ -136,8 +137,7 @@ psa_status_t mbedtls_psa_ecp_load_representation(
}
mbedtls_ecp_keypair_init(ecp);
status = check_ecc_parameters(PSA_KEY_TYPE_ECC_GET_FAMILY(type), curve_bits,
!explicit_bits);
status = check_ecc_parameters(PSA_KEY_TYPE_ECC_GET_FAMILY(type), &curve_bits);
if (status != PSA_SUCCESS) {
goto exit;
}

2
library/psa_util.c
View file

@ -276,7 +276,6 @@ mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t curve,
#endif
#if defined(PSA_WANT_ECC_SECP_R1_521)
case 521:
case 528:
return MBEDTLS_ECP_DP_SECP521R1;
#endif
}
@ -303,7 +302,6 @@ mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t curve,
switch (bits) {
#if defined(PSA_WANT_ECC_MONTGOMERY_255)
case 255:
case 256:
return MBEDTLS_ECP_DP_CURVE25519;
#endif
#if defined(PSA_WANT_ECC_MONTGOMERY_448)