/*
* Copyright (c) 2020-2022 Yubico AB. All rights reserved.
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file.
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <stdio.h>
#include <string.h>
#include "fido.h"
#include "fido/param.h"
#include "iso7816.h"
#define TX_CHUNK_SIZE 240
static const uint8_t aid[] = { 0xa0, 0x00, 0x00, 0x06, 0x47, 0x2f, 0x00, 0x01 };
static const uint8_t v_u2f[] = { 'U', '2', 'F', '_', 'V', '2' };
static const uint8_t v_fido[] = { 'F', 'I', 'D', 'O', '_', '2', '_', '0' };
static int
tx_short_apdu(fido_dev_t *d, const iso7816_header_t *h, const uint8_t *payload,
uint8_t payload_len, uint8_t cla_flags)
{
uint8_t apdu[5 + UINT8_MAX + 1];
uint8_t sw[2];
size_t apdu_len;
int ok = -1;
memset(&apdu, 0, sizeof(apdu));
apdu[0] = h->cla | cla_flags;
apdu[1] = h->ins;
apdu[2] = h->p1;
apdu[3] = h->p2;
apdu[4] = payload_len;
memcpy(&apdu[5], payload, payload_len);
apdu_len = (size_t)(5 + payload_len + 1);
if (d->io.write(d->io_handle, apdu, apdu_len) < 0) {
fido_log_debug("%s: write", __func__);
goto fail;
}
if (cla_flags & 0x10) {
if (d->io.read(d->io_handle, sw, sizeof(sw), -1) != 2) {
fido_log_debug("%s: read", __func__);
goto fail;
}
if ((sw[0] << 8 | sw[1]) != SW_NO_ERROR) {
fido_log_debug("%s: unexpected sw", __func__);
goto fail;
}
}
ok = 0;
fail:
explicit_bzero(apdu, sizeof(apdu));
return ok;
}
static int
nfc_do_tx(fido_dev_t *d, const uint8_t *apdu_ptr, size_t apdu_len)
{
iso7816_header_t h;
if (fido_buf_read(&apdu_ptr, &apdu_len, &h, sizeof(h)) < 0) {
fido_log_debug("%s: header", __func__);
return -1;
}
if (apdu_len < 2) {
fido_log_debug("%s: apdu_len %zu", __func__, apdu_len);
return -1;
}
apdu_len -= 2; /* trim le1 le2 */
while (apdu_len > TX_CHUNK_SIZE) {
if (tx_short_apdu(d, &h, apdu_ptr, TX_CHUNK_SIZE, 0x10) < 0) {
fido_log_debug("%s: chain", __func__);
return -1;
}
apdu_ptr += TX_CHUNK_SIZE;
apdu_len -= TX_CHUNK_SIZE;
}
if (tx_short_apdu(d, &h, apdu_ptr, (uint8_t)apdu_len, 0) < 0) {
fido_log_debug("%s: tx_short_apdu", __func__);
return -1;
}
return 0;
}
int
fido_nfc_tx(fido_dev_t *d, uint8_t cmd, const unsigned char *buf, size_t count)
{
iso7816_apdu_t *apdu = NULL;
const uint8_t *ptr;
size_t len;
int ok = -1;
switch (cmd) {
case CTAP_CMD_INIT: /* select */
if ((apdu = iso7816_new(0, 0xa4, 0x04, sizeof(aid))) == NULL ||
iso7816_add(apdu, aid, sizeof(aid)) < 0) {
fido_log_debug("%s: iso7816", __func__);
goto fail;
}
break;
case CTAP_CMD_CBOR: /* wrap cbor */
if (count > UINT16_MAX || (apdu = iso7816_new(0x80, 0x10, 0x00,
(uint16_t)count)) == NULL ||
iso7816_add(apdu, buf, count) < 0) {
fido_log_debug("%s: iso7816", __func__);
goto fail;
}
break;
case CTAP_CMD_MSG: /* already an apdu */
break;
default:
fido_log_debug("%s: cmd=%02x", __func__, cmd);
goto fail;
}
if (apdu != NULL) {
ptr = iso7816_ptr(apdu);
len = iso7816_len(apdu);
} else {
ptr = buf;
len = count;
}
if (nfc_do_tx(d, ptr, len) < 0) {
fido_log_debug("%s: nfc_do_tx", __func__);
goto fail;
}
ok = 0;
fail:
iso7816_free(&apdu);
return ok;
}
static int
rx_init(fido_dev_t *d, unsigned char *buf, size_t count, int ms)
{
fido_ctap_info_t *attr = (fido_ctap_info_t *)buf;
uint8_t f[64];
int n;
if (count != sizeof(*attr)) {
fido_log_debug("%s: count=%zu", __func__, count);
return -1;
}
memset(attr, 0, sizeof(*attr));
if ((n = d->io.read(d->io_handle, f, sizeof(f), ms)) < 2 ||
(f[n - 2] << 8 | f[n - 1]) != SW_NO_ERROR) {
fido_log_debug("%s: read", __func__);
return -1;
}
n -= 2;
if (n == sizeof(v_u2f) && memcmp(f, v_u2f, sizeof(v_u2f)) == 0)
attr->flags = FIDO_CAP_CBOR;
else if (n == sizeof(v_fido) && memcmp(f, v_fido, sizeof(v_fido)) == 0)
attr->flags = FIDO_CAP_CBOR | FIDO_CAP_NMSG;
else {
fido_log_debug("%s: unknown version string", __func__);
#ifdef FIDO_FUZZ
attr->flags = FIDO_CAP_CBOR | FIDO_CAP_NMSG;
#else
return -1;
#endif
}
memcpy(&attr->nonce, &d->nonce, sizeof(attr->nonce)); /* XXX */
return (int)count;
}
static int
tx_get_response(fido_dev_t *d, uint8_t count)
{
uint8_t apdu[5];
memset(apdu, 0, sizeof(apdu));
apdu[1] = 0xc0; /* GET_RESPONSE */
apdu[4] = count;
if (d->io.write(d->io_handle, apdu, sizeof(apdu)) < 0) {
fido_log_debug("%s: write", __func__);
return -1;
}
return 0;
}
static int
rx_apdu(fido_dev_t *d, uint8_t sw[2], unsigned char **buf, size_t *count, int *ms)
{
uint8_t f[256 + 2];
struct timespec ts;
int n, ok = -1;
if (fido_time_now(&ts) != 0)
goto fail;
if ((n = d->io.read(d->io_handle, f, sizeof(f), *ms)) < 2) {
fido_log_debug("%s: read", __func__);
goto fail;
}
if (fido_time_delta(&ts, ms) != 0)
goto fail;
if (fido_buf_write(buf, count, f, (size_t)(n - 2)) < 0) {
fido_log_debug("%s: fido_buf_write", __func__);
goto fail;
}
memcpy(sw, f + n - 2, 2);
ok = 0;
fail:
explicit_bzero(f, sizeof(f));
return ok;
}
static int
rx_msg(fido_dev_t *d, unsigned char *buf, size_t count, int ms)
{
uint8_t sw[2];
const size_t bufsiz = count;
if (rx_apdu(d, sw, &buf, &count, &ms) < 0) {
fido_log_debug("%s: preamble", __func__);
return -1;
}
while (sw[0] == SW1_MORE_DATA)
if (tx_get_response(d, sw[1]) < 0 ||
rx_apdu(d, sw, &buf, &count, &ms) < 0) {
fido_log_debug("%s: chain", __func__);
return -1;
}
if (fido_buf_write(&buf, &count, sw, sizeof(sw)) < 0) {
fido_log_debug("%s: sw", __func__);
return -1;
}
if (bufsiz - count > INT_MAX) {
fido_log_debug("%s: bufsiz", __func__);
return -1;
}
return (int)(bufsiz - count);
}
static int
rx_cbor(fido_dev_t *d, unsigned char *buf, size_t count, int ms)
{
int r;
if ((r = rx_msg(d, buf, count, ms)) < 2)
return -1;
return r - 2;
}
int
fido_nfc_rx(fido_dev_t *d, uint8_t cmd, unsigned char *buf, size_t count, int ms)
{
switch (cmd) {
case CTAP_CMD_INIT:
return rx_init(d, buf, count, ms);
case CTAP_CMD_CBOR:
return rx_cbor(d, buf, count, ms);
case CTAP_CMD_MSG:
return rx_msg(d, buf, count, ms);
default:
fido_log_debug("%s: cmd=%02x", __func__, cmd);
return -1;
}
}
bool
nfc_is_fido(const char *path)
{
bool fido = false;
fido_dev_t *d;
int r;
if ((d = fido_dev_new()) == NULL) {
fido_log_debug("%s: fido_dev_new", __func__);
goto fail;
}
/* fido_dev_open selects the fido applet */
if ((r = fido_dev_open(d, path)) != FIDO_OK) {
fido_log_debug("%s: fido_dev_open: 0x%x", __func__, r);
goto fail;
}
if ((r = fido_dev_close(d)) != FIDO_OK) {
fido_log_debug("%s: fido_dev_close: 0x%x", __func__, r);
goto fail;
}
fido = true;
fail:
fido_dev_free(&d);
return fido;
}
#ifdef USE_NFC
bool
fido_is_nfc(const char *path)
{
return strncmp(path, FIDO_NFC_PREFIX, strlen(FIDO_NFC_PREFIX)) == 0;
}
int
fido_dev_set_nfc(fido_dev_t *d)
{
if (d->io_handle != NULL) {
fido_log_debug("%s: device open", __func__);
return -1;
}
d->io_own = true;
d->io = (fido_dev_io_t) {
fido_nfc_open,
fido_nfc_close,
fido_nfc_read,
fido_nfc_write,
};
d->transport = (fido_dev_transport_t) {
fido_nfc_rx,
fido_nfc_tx,
};
return 0;
}
#endif /* USE_NFC */
