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Added functions for writing COSE keys.

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Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos 2023-08-17 01:19:27 +02:00
parent b2c4e0e1c1
commit 63e15b19bb
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GPG Key ID: C0095B7870A4CCD3
2 changed files with 84 additions and 0 deletions
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77
src/fido/cbor.c
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@ -24,6 +24,7 @@
#include "usb.h"
#include "apdu.h"
#include "management.h"
#include "ctap2_cbor.h"
const bool _btrue = true, _bfalse = false;
@ -127,3 +128,79 @@ int cbor_process(uint8_t last_cmd, const uint8_t *data, size_t len) {
res_APDU_size = 0;
return 1;
}
CborError COSE_key_params(int crv, int alg, mbedtls_ecp_group *grp, mbedtls_ecp_point *Q, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
CborError error = CborNoError;
int kty = 1;
if (crv == FIDO2_CURVE_P256 || crv == FIDO2_CURVE_P384 || crv == FIDO2_CURVE_P521 || crv == FIDO2_CURVE_P256K1) {
kty = 2;
}
CBOR_CHECK(cbor_encoder_create_map(mapEncoderParent, mapEncoder, 5));
CBOR_CHECK(cbor_encode_uint(mapEncoder, 1));
CBOR_CHECK(cbor_encode_uint(mapEncoder, kty));
CBOR_CHECK(cbor_encode_uint(mapEncoder, 3));
CBOR_CHECK(cbor_encode_negative_int(mapEncoder, -alg));
CBOR_CHECK(cbor_encode_negative_int(mapEncoder, 1));
CBOR_CHECK(cbor_encode_uint(mapEncoder, crv));
CBOR_CHECK(cbor_encode_negative_int(mapEncoder, 2));
uint8_t pkey[67];
if (kty == 2) {
size_t plen = mbedtls_mpi_size(&grp->P);
CBOR_CHECK(mbedtls_mpi_write_binary(&Q->X, pkey, plen));
CBOR_CHECK(cbor_encode_byte_string(mapEncoder, pkey, plen));
CBOR_CHECK(cbor_encode_negative_int(mapEncoder, 3));
CBOR_CHECK(mbedtls_mpi_write_binary(&Q->Y, pkey, plen));
CBOR_CHECK(cbor_encode_byte_string(mapEncoder, pkey, plen));
}
else {
size_t olen = 0;
CBOR_CHECK(mbedtls_ecp_point_write_binary(grp, Q, MBEDTLS_ECP_PF_COMPRESSED, &olen, pkey, sizeof(pkey)));
CBOR_CHECK(cbor_encode_byte_string(mapEncoder, pkey, olen));
}
CBOR_CHECK(cbor_encoder_close_container(mapEncoderParent, mapEncoder));
err:
return error;
}
CborError COSE_key(mbedtls_ecp_keypair *key, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
int crv = mbedtls_curve_to_fido(key->grp.id), alg = 0;
if (key->grp.id == MBEDTLS_ECP_DP_SECP256R1) {
alg = FIDO2_ALG_ES256;
}
else if (key->grp.id == MBEDTLS_ECP_DP_SECP384R1) {
alg = FIDO2_ALG_ES384;
}
else if (key->grp.id == MBEDTLS_ECP_DP_SECP521R1) {
alg = FIDO2_ALG_ES512;
}
else if (key->grp.id == MBEDTLS_ECP_DP_SECP256K1) {
alg = FIDO2_ALG_ES256K;
}
else if (key->grp.id == MBEDTLS_ECP_DP_CURVE25519) {
alg = FIDO2_ALG_ECDH_ES_HKDF_256;
}
return COSE_key_params(crv, alg, &key->grp, &key->Q, mapEncoderParent, mapEncoder);
}
CborError COSE_key_shared(mbedtls_ecdh_context *key, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
int crv = mbedtls_curve_to_fido(key->ctx.mbed_ecdh.grp.id), alg = FIDO2_ALG_ECDH_ES_HKDF_256;
return COSE_key_params(crv, alg, &key->ctx.mbed_ecdh.grp, &key->ctx.mbed_ecdh.Q, mapEncoderParent, mapEncoder);
}
CborError COSE_public_key(int alg, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
CborError error = CborNoError;
CBOR_CHECK(cbor_encoder_create_map(mapEncoderParent, mapEncoder, 2));
CBOR_CHECK(cbor_encode_text_stringz(mapEncoder, "alg"));
CBOR_CHECK(cbor_encode_negative_int(mapEncoder, -alg));
CBOR_CHECK(cbor_encode_text_stringz(mapEncoder, "type"));
CBOR_CHECK(cbor_encode_text_stringz(mapEncoder, "public-key"));
CBOR_CHECK(cbor_encoder_close_container(mapEncoderParent, mapEncoder));
err:
return error;
}

7
src/fido/ctap2_cbor.h
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@ -19,6 +19,9 @@
#define _CTAP2_CBOR_H_
#include "cbor.h"
#include "common.h"
#include "mbedtls/ecp.h"
#include "mbedtls/ecdh.h"
extern uint8_t *driver_prepare_response();
extern void driver_exec_finished(size_t size_next);
@ -237,4 +240,8 @@ typedef struct CborCharString {
CBOR_CHECK(cbor_encode_boolean(&(p), v == ptrue ? true : false)); \
} } while (0)
extern CborError COSE_key(mbedtls_ecp_keypair *, CborEncoder *, CborEncoder *);
extern CborError COSE_key_shared(mbedtls_ecdh_context *key, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder);
extern CborError COSE_public_key(int alg, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder);
#endif //_CTAP2_CBOR_H_