Arduino/pico-fido
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Instead of generating a new keypair, all keys are derived from the master key.

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Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos
2022-09-05 11:30:49 +02:00
parent 65b14960ce
commit ed0a798f63
2 changed files with 130 additions and 17 deletions
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133
src/fido/fido.c
View File

@@ -15,6 +15,7 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "common.h"
#include "fido.h"
#include "hsm.h"
#include "apdu.h"
@@ -22,6 +23,11 @@
#include "files.h"
#include "file.h"
#include "random.h"
#include "mbedtls/ecdsa.h"
#include "mbedtls/x509_crt.h"
#include "mbedtls/hkdf.h"
#include "pk_wrap.h"
#include "crypto_utils.h"
#include <stdio.h>
void init_fido();
@@ -44,34 +50,137 @@ app_t *fido_select(app_t *a) {
void __attribute__ ((constructor)) fido_ctor() {
register_app(fido_select);
fido_select(&apps[0]);
//fido_select(&apps[0]);
}
int fido_unload() {
return CCID_OK;
}
void scan_files() {
ef_mkek = search_by_fid(EF_MKEK, NULL, SPECIFY_EF);
if (ef_mkek) {
if (!ef_mkek->data) {
printf("MKEK is empty. Initializing with default password\r\n");
uint8_t tmp_mkek[MKEK_SIZE];
const uint8_t *rd = random_bytes_get(MKEK_IV_SIZE+MKEK_KEY_SIZE);
memcpy(tmp_mkek, rd, MKEK_IV_SIZE+MKEK_KEY_SIZE);
flash_write_data_to_file(ef_mkek, tmp_mkek, MKEK_SIZE);
int x509_create_cert(mbedtls_ecdsa_context *ecdsa, uint8_t *buffer, size_t buffer_size) {
mbedtls_x509write_cert ctx;
mbedtls_x509write_crt_init(&ctx);
mbedtls_x509write_crt_set_version(&ctx, MBEDTLS_X509_CRT_VERSION_3);
mbedtls_x509write_crt_set_validity(&ctx, "20220901000000", "20320831235959" );
mbedtls_x509write_crt_set_issuer_name(&ctx, "C=ES,O=Pico HSM,CN=Pico FIDO");
mbedtls_x509write_crt_set_subject_name(&ctx, "C=ES,O=Pico HSM,CN=Pico FIDO");
mbedtls_mpi serial;
mbedtls_mpi_init(&serial);
mbedtls_mpi_fill_random(&serial, 32, random_gen, NULL);
mbedtls_x509write_crt_set_serial(&ctx, &serial);
mbedtls_pk_context key;
mbedtls_pk_init(&key);
mbedtls_pk_setup(&key, mbedtls_pk_info_from_type(MBEDTLS_PK_ECKEY));
key.pk_ctx = ecdsa;
mbedtls_x509write_crt_set_subject_key(&ctx, &key);
mbedtls_x509write_crt_set_issuer_key(&ctx, &key);
mbedtls_x509write_crt_set_md_alg(&ctx, MBEDTLS_MD_SHA256);
mbedtls_x509write_crt_set_basic_constraints(&ctx, 0, 0);
mbedtls_x509write_crt_set_subject_key_identifier(&ctx);
mbedtls_x509write_crt_set_authority_key_identifier(&ctx);
mbedtls_x509write_crt_set_key_usage(&ctx, MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_KEY_CERT_SIGN);
int ret = mbedtls_x509write_crt_der(&ctx, buffer, buffer_size, random_gen, NULL);
return ret;
}
int load_keydev(uint8_t *key) {
if (!ef_keydev || file_get_size(ef_keydev) == 0)
return CCID_ERR_MEMORY_FATAL;
memcpy(key, file_get_data(ef_keydev), file_get_size(ef_keydev));
//return mkek_decrypt(key, file_get_size(ef_keydev));
return CCID_OK;
}
int derive_key(const uint8_t *app_id, bool new_key, uint8_t *key_handle, mbedtls_ecdsa_context *key) {
const int entries = KEY_PATH_LEN / sizeof(uint32_t);
uint8_t outk[64] = {0};
int r = 0;
memset(outk, 0, sizeof(outk));
if ((r = load_keydev(outk)) != CCID_OK)
return r;
const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA512);
for (int i = 0; i < entries; i++)
{
if (new_key == true) {
uint32_t val = 0x80000000 | *((uint32_t *)random_bytes_get(sizeof(uint32_t)));
memcpy(&key_handle[i*sizeof(uint32_t)], &val, sizeof(uint32_t));
}
if ((r = mbedtls_hkdf(md_info, &key_handle[i], sizeof(uint32_t), outk, 32, outk + 32, 32, outk, sizeof(outk))) != 0)
{
mbedtls_platform_zeroize(outk, sizeof(outk));
return r;
}
}
if ((r = mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), outk, 32, app_id, 32, key_handle + 32)) != 0)
{
mbedtls_platform_zeroize(outk, sizeof(outk));
return r;
}
mbedtls_ecp_group_load(&key->grp, MBEDTLS_ECP_DP_SECP256R1);
r = mbedtls_ecp_read_key(MBEDTLS_ECP_DP_SECP256R1, key, outk, 32);
mbedtls_platform_zeroize(outk, sizeof(outk));
if (r != 0)
return r;
return mbedtls_ecp_mul(&key->grp, &key->Q, &key->d, &key->grp.G, random_gen, NULL );
}
int scan_files() {
ef_keydev = search_by_fid(EF_KEY_DEV, NULL, SPECIFY_EF);
if (ef_keydev) {
if (!ef_keydev->data) {
printf("KEY DEVICE is empty. Generating SECP256R1 curve...");
mbedtls_ecdsa_context ecdsa;
mbedtls_ecdsa_init(&ecdsa);
uint8_t index = 0;
int ret = mbedtls_ecdsa_genkey(&ecdsa, MBEDTLS_ECP_DP_SECP256R1, random_gen, &index);
if (ret != 0) {
mbedtls_ecdsa_free(&ecdsa);
return ret;
}
uint8_t kdata[32];
int key_size = mbedtls_mpi_size(&ecdsa.d);
mbedtls_mpi_write_binary(&ecdsa.d, kdata, key_size);
//ret = mkek_encrypt(kdata, key_size);
if (ret != CCID_OK) {
mbedtls_ecdsa_free(&ecdsa);
return ret;
}
ret = flash_write_data_to_file(ef_keydev, kdata, key_size);
mbedtls_platform_zeroize(kdata, sizeof(kdata));
if (ret != CCID_OK) {
mbedtls_ecdsa_free(&ecdsa);
return ret;
}
uint8_t cert[4096];
ret = x509_create_cert(&ecdsa, cert, sizeof(cert));
mbedtls_ecdsa_free(&ecdsa);
if (ret <= 0)
return ret;
ef_certdev = search_by_fid(EF_EE_DEV, NULL, SPECIFY_EF);
if (!ef_certdev)
return CCID_ERR_MEMORY_FATAL;
flash_write_data_to_file(ef_certdev, cert + sizeof(cert) - ret, ret);
DEBUG_PAYLOAD(cert + sizeof(cert) - ret, ret);
printf(" done!\n");
}
}
else {
printf("FATAL ERROR: PIN1 not found in memory!\r\n");
printf("FATAL ERROR: KEY DEV not found in memory!\r\n");
}
ef_certdev = search_by_fid(EF_EE_DEV, NULL, SPECIFY_EF);
if (ef_certdev) {
}
else {
printf("FATAL ERROR: MKEK not found in memory!\r\n");
}
low_flash_available();
return CCID_OK;
}
void scan_all() {
scan_flash();
scan_files();
}
void init_fido() {

14
src/fido/fido.h
View File

@@ -18,12 +18,16 @@
#ifndef _FIDO_H_
#define _FIDO_H_
#define U2F_PUBKEY_LEN 65
#define KEY_PATH_LEN 32
#include <stdlib.h>
#include "pico/stdlib.h"
#include "common.h"
#include "mbedtls/ecdsa.h"
#define U2F_PUBKEY_LEN (65)
#define KEY_PATH_LEN (32)
#define SHA256_DIGEST_LENGTH (32)
#define KEY_HANDLE_LEN (KEY_PATH_LEN + SHA256_DIGEST_LENGTH)
#define MKEK_IV_SIZE 16
#define MKEK_KEY_SIZE 32
#define MKEK_SIZE (MKEK_IV_SIZE+MKEK_KEY_SIZE)
extern int derive_key(const uint8_t *app_id, bool new_key, uint8_t *key_handle, mbedtls_ecdsa_context *key);
#endif //_FIDO_H