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Add support for hmac-secret-mc extension.

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Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos
2025-08-28 01:04:09 +02:00
parent 73a7856866
commit 292a9e8d8a
2 changed files with 94 additions and 2 deletions
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3
src/fido/cbor_get_info.c
View File

@@ -38,12 +38,13 @@ int cbor_get_info() {
CBOR_CHECK(cbor_encoder_close_container(&mapEncoder, &arrayEncoder));
CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x02));
CBOR_CHECK(cbor_encoder_create_array(&mapEncoder, &arrayEncoder, 6));
CBOR_CHECK(cbor_encoder_create_array(&mapEncoder, &arrayEncoder, 7));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "credBlob"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "credProtect"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "hmac-secret"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "largeBlobKey"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "minPinLength"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "hmac-secret-mc"));
CBOR_CHECK(cbor_encode_text_stringz(&arrayEncoder, "thirdPartyPayment"));
CBOR_CHECK(cbor_encoder_close_container(&mapEncoder, &arrayEncoder));

93
src/fido/cbor_make_credential.c
View File

@@ -26,6 +26,7 @@
#include "mbedtls/sha256.h"
#include "random.h"
#include "pico_keys.h"
#include "crypto_utils.h"
int cbor_make_credential(const uint8_t *data, size_t len) {
CborParser parser;
@@ -39,7 +40,10 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
PublicKeyCredentialDescriptor excludeList[MAX_CREDENTIAL_COUNT_IN_LIST] = { 0 };
size_t excludeList_len = 0;
CredOptions options = { 0 };
uint64_t pinUvAuthProtocol = 0, enterpriseAttestation = 0;
uint64_t pinUvAuthProtocol = 0, enterpriseAttestation = 0, hmacSecretPinUvAuthProtocol = 1;
int64_t kty = 2, hmac_alg = 0, crv = 0;
CborByteString kax = { 0 }, kay = { 0 }, salt_enc = { 0 }, salt_auth = { 0 };
bool hmac_secret_mc = false;
uint8_t *aut_data = NULL;
size_t resp_size = 0;
CredExtensions extensions = { 0 };
@@ -127,6 +131,31 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
CBOR_PARSE_MAP_START(_f1, 2)
{
CBOR_FIELD_GET_KEY_TEXT(2);
if (strcmp(_fd2, "hmac-secret-mc") == 0) {
hmac_secret_mc = true;
uint64_t ukey = 0;
CBOR_PARSE_MAP_START(_f2, 3)
{
CBOR_FIELD_GET_UINT(ukey, 3);
if (ukey == 0x01) {
CBOR_CHECK(COSE_read_key(&_f3, &kty, &hmac_alg, &crv, &kax, &kay));
}
else if (ukey == 0x02) {
CBOR_FIELD_GET_BYTES(salt_enc, 3);
}
else if (ukey == 0x03) {
CBOR_FIELD_GET_BYTES(salt_auth, 3);
}
else if (ukey == 0x04) {
CBOR_FIELD_GET_UINT(hmacSecretPinUvAuthProtocol, 3);
}
else {
CBOR_ADVANCE(3);
}
}
CBOR_PARSE_MAP_END(_f2, 3);
continue;
}
CBOR_FIELD_KEY_TEXT_VAL_BOOL(2, "hmac-secret", extensions.hmac_secret);
CBOR_FIELD_KEY_TEXT_VAL_UINT(2, "credProtect", extensions.credProtect);
CBOR_FIELD_KEY_TEXT_VAL_BOOL(2, "minPinLength", extensions.minPinLength);
@@ -313,6 +342,10 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
CBOR_ERROR(CTAP2_ERR_INVALID_OPTION);
}
if (hmac_secret_mc && extensions.hmac_secret != ptrue) {
CBOR_ERROR(CTAP2_ERR_MISSING_PARAMETER);
}
if (options.up == ptrue || options.up == NULL) { //14.1
if (pinUvAuthParam.present == true) {
if (getUserPresentFlagValue() == false) {
@@ -372,6 +405,9 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
if (extensions.credBlob.present == true) {
l++;
}
if (hmac_secret_mc) {
l++;
}
if (l > 0) {
CBOR_CHECK(cbor_encoder_create_map(&encoder, &mapEncoder, l));
if (extensions.credBlob.present == true) {
@@ -392,6 +428,57 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder, "minPinLength"));
CBOR_CHECK(cbor_encode_uint(&mapEncoder, minPinLen));
}
if (hmac_secret_mc) {
CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder, "hmac-secret-mc"));
uint8_t sharedSecret[64] = {0};
mbedtls_ecp_point Qp;
mbedtls_ecp_point_init(&Qp);
mbedtls_mpi_lset(&Qp.Z, 1);
if (mbedtls_mpi_read_binary(&Qp.X, kax.data, kax.len) != 0) {
mbedtls_ecp_point_free(&Qp);
CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
}
if (mbedtls_mpi_read_binary(&Qp.Y, kay.data, kay.len) != 0) {
mbedtls_ecp_point_free(&Qp);
CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
}
int ret = ecdh((uint8_t)hmacSecretPinUvAuthProtocol, &Qp, sharedSecret);
mbedtls_ecp_point_free(&Qp);
if (ret != 0) {
mbedtls_platform_zeroize(sharedSecret, sizeof(sharedSecret));
CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
}
if (verify((uint8_t)hmacSecretPinUvAuthProtocol, sharedSecret, salt_enc.data, (uint16_t)salt_enc.len, salt_auth.data) != 0) {
mbedtls_platform_zeroize(sharedSecret, sizeof(sharedSecret));
CBOR_ERROR(CTAP2_ERR_EXTENSION_FIRST);
}
uint8_t salt_dec[64] = {0}, poff = ((uint8_t)hmacSecretPinUvAuthProtocol - 1) * IV_SIZE;
ret = decrypt((uint8_t)hmacSecretPinUvAuthProtocol, sharedSecret, salt_enc.data, (uint16_t)salt_enc.len, salt_dec);
if (ret != 0) {
mbedtls_platform_zeroize(sharedSecret, sizeof(sharedSecret));
CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
}
uint8_t cred_random[64] = {0}, *crd = NULL;
ret = credential_derive_hmac_key(cred_id, cred_id_len, cred_random);
if (ret != 0) {
mbedtls_platform_zeroize(sharedSecret, sizeof(sharedSecret));
CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
}
if (flags & FIDO2_AUT_FLAG_UV) {
crd = cred_random + 32;
}
else {
crd = cred_random;
}
uint8_t out1[64] = {0}, hmac_res[80] = {0};
mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), crd, 32, salt_dec, 32, out1);
if ((uint8_t)salt_enc.len == 64 + poff) {
mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), crd, 32, salt_dec + 32, 32, out1 + 32);
}
encrypt((uint8_t)hmacSecretPinUvAuthProtocol, sharedSecret, out1, (uint16_t)(salt_enc.len - poff), hmac_res);
CBOR_CHECK(cbor_encode_byte_string(&mapEncoder, hmac_res, salt_enc.len));
}
CBOR_CHECK(cbor_encoder_close_container(&encoder, &mapEncoder));
ext_len = cbor_encoder_get_buffer_size(&encoder, ext);
@@ -569,6 +656,10 @@ err:
CBOR_FREE_BYTE_STRING(user.id);
CBOR_FREE_BYTE_STRING(user.displayName);
CBOR_FREE_BYTE_STRING(user.parent.name);
CBOR_FREE_BYTE_STRING(kax);
CBOR_FREE_BYTE_STRING(kay);
CBOR_FREE_BYTE_STRING(salt_enc);
CBOR_FREE_BYTE_STRING(salt_auth);
if (extensions.present == true) {
CBOR_FREE_BYTE_STRING(extensions.credBlob);
}