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openssh-portable/sk-usbhid.c

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/* $OpenBSD: sk-usbhid.c,v 1.34 2021/11/03 22:00:56 deraadt Exp $ */
/*
* Copyright (c) 2019 Markus Friedl
* Copyright (c) 2020 Pedro Martelletto
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "includes.h"
#ifdef ENABLE_SK_INTERNAL
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stddef.h>
#include <stdarg.h>
#include <time.h>
#ifdef HAVE_SHA2_H
#include <sha2.h>
#endif
/*
* Almost every use of OpenSSL in this file is for ECDSA-NISTP256.
* This is strictly a larger hammer than necessary, but it reduces changes
* with upstream.
*/
#ifndef OPENSSL_HAS_ECC
# undef WITH_OPENSSL
#endif
#ifdef WITH_OPENSSL
#include <openssl/opensslv.h>
#include <openssl/crypto.h>
#include <openssl/bn.h>
#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/evp.h>
#endif /* WITH_OPENSSL */
#include <fido.h>
#include <fido/credman.h>
/* backwards compat for libfido2 */
#ifndef HAVE_FIDO_CRED_PROT
#define fido_cred_prot(x) (0)
#endif
#ifndef HAVE_FIDO_CRED_SET_PROT
#define fido_cred_set_prot(x, y) (FIDO_ERR_UNSUPPORTED_OPTION)
#endif
#ifndef HAVE_FIDO_DEV_SUPPORTS_CRED_PROT
#define fido_dev_supports_cred_prot(x) (0)
#endif
#ifndef HAVE_FIDO_DEV_GET_TOUCH_BEGIN
#define fido_dev_get_touch_begin(x) (FIDO_ERR_UNSUPPORTED_OPTION)
#endif
#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS
#define fido_dev_get_touch_status(x, y, z) (FIDO_ERR_UNSUPPORTED_OPTION)
#endif
#ifndef FIDO_CRED_PROT_UV_REQUIRED
#define FIDO_CRED_PROT_UV_REQUIRED 0
#endif
#ifndef FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID
#define FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID 0
#endif
#ifndef SK_STANDALONE
# include "log.h"
# include "xmalloc.h"
# include "misc.h"
/*
* If building as part of OpenSSH, then rename exported functions.
* This must be done before including sk-api.h.
*/
# define sk_api_version ssh_sk_api_version
# define sk_enroll ssh_sk_enroll
# define sk_sign ssh_sk_sign
# define sk_load_resident_keys ssh_sk_load_resident_keys
#endif /* !SK_STANDALONE */
#include "sk-api.h"
/* #define SK_DEBUG 1 */
#ifdef SK_DEBUG
#define SSH_FIDO_INIT_ARG FIDO_DEBUG
#else
#define SSH_FIDO_INIT_ARG 0
#endif
#define MAX_FIDO_DEVICES 8
#define FIDO_POLL_MS 50
#define SELECT_MS 15000
#define POLL_SLEEP_NS 200000000
/* Compatibility with OpenSSH 1.0.x */
#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
#define ECDSA_SIG_get0(sig, pr, ps) \
do { \
(*pr) = sig->r; \
(*ps) = sig->s; \
} while (0)
#endif
#ifndef FIDO_ERR_OPERATION_DENIED
#define FIDO_ERR_OPERATION_DENIED 0x27
#endif
struct sk_usbhid {
fido_dev_t *dev;
char *path;
};
/* Return the version of the middleware API */
uint32_t sk_api_version(void);
/* Enroll a U2F key (private key generation) */
int sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
const char *application, uint8_t flags, const char *pin,
struct sk_option **options, struct sk_enroll_response **enroll_response);
/* Sign a challenge */
int sk_sign(uint32_t alg, const uint8_t *data, size_t data_len,
const char *application, const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, const char *pin, struct sk_option **options,
struct sk_sign_response **sign_response);
/* Load resident keys */
int sk_load_resident_keys(const char *pin, struct sk_option **options,
struct sk_resident_key ***rks, size_t *nrks);
static void skdebug(const char *func, const char *fmt, ...)
__attribute__((__format__ (printf, 2, 3)));
static void
skdebug(const char *func, const char *fmt, ...)
{
#if !defined(SK_STANDALONE)
char *msg;
va_list ap;
va_start(ap, fmt);
xvasprintf(&msg, fmt, ap);
va_end(ap);
debug("%s: %s", func, msg);
free(msg);
#elif defined(SK_DEBUG)
va_list ap;
va_start(ap, fmt);
fprintf(stderr, "%s: ", func);
vfprintf(stderr, fmt, ap);
fputc('\n', stderr);
va_end(ap);
#else
(void)func; /* XXX */
(void)fmt; /* XXX */
#endif
}
uint32_t
sk_api_version(void)
{
return SSH_SK_VERSION_MAJOR;
}
static struct sk_usbhid *
sk_open(const char *path)
{
struct sk_usbhid *sk;
int r;
if (path == NULL) {
skdebug(__func__, "path == NULL");
return NULL;
}
if ((sk = calloc(1, sizeof(*sk))) == NULL) {
skdebug(__func__, "calloc sk failed");
return NULL;
}
if ((sk->path = strdup(path)) == NULL) {
skdebug(__func__, "strdup path failed");
free(sk);
return NULL;
}
if ((sk->dev = fido_dev_new()) == NULL) {
skdebug(__func__, "fido_dev_new failed");
free(sk->path);
free(sk);
return NULL;
}
if ((r = fido_dev_open(sk->dev, sk->path)) != FIDO_OK) {
skdebug(__func__, "fido_dev_open %s failed: %s", sk->path,
fido_strerr(r));
fido_dev_free(&sk->dev);
free(sk->path);
free(sk);
return NULL;
}
return sk;
}
static void
sk_close(struct sk_usbhid *sk)
{
if (sk == NULL)
return;
fido_dev_cancel(sk->dev); /* cancel any pending operation */
fido_dev_close(sk->dev);
fido_dev_free(&sk->dev);
free(sk->path);
free(sk);
}
static struct sk_usbhid **
sk_openv(const fido_dev_info_t *devlist, size_t ndevs, size_t *nopen)
{
const fido_dev_info_t *di;
struct sk_usbhid **skv;
size_t i;
*nopen = 0;
if ((skv = calloc(ndevs, sizeof(*skv))) == NULL) {
skdebug(__func__, "calloc skv failed");
return NULL;
}
for (i = 0; i < ndevs; i++) {
if ((di = fido_dev_info_ptr(devlist, i)) == NULL)
skdebug(__func__, "fido_dev_info_ptr failed");
else if ((skv[*nopen] = sk_open(fido_dev_info_path(di))) == NULL)
skdebug(__func__, "sk_open failed");
else
(*nopen)++;
}
if (*nopen == 0) {
for (i = 0; i < ndevs; i++)
sk_close(skv[i]);
free(skv);
skv = NULL;
}
return skv;
}
static void
sk_closev(struct sk_usbhid **skv, size_t nsk)
{
size_t i;
for (i = 0; i < nsk; i++)
sk_close(skv[i]);
free(skv);
}
static int
sk_touch_begin(struct sk_usbhid **skv, size_t nsk)
{
size_t i, ok = 0;
int r;
for (i = 0; i < nsk; i++)
if ((r = fido_dev_get_touch_begin(skv[i]->dev)) != FIDO_OK)
skdebug(__func__, "fido_dev_get_touch_begin %s failed:"
" %s", skv[i]->path, fido_strerr(r));
else
ok++;
return ok ? 0 : -1;
}
static int
sk_touch_poll(struct sk_usbhid **skv, size_t nsk, int *touch, size_t *idx)
{
struct timespec ts_pause;
size_t npoll, i;
int r;
ts_pause.tv_sec = 0;
ts_pause.tv_nsec = POLL_SLEEP_NS;
nanosleep(&ts_pause, NULL);
npoll = nsk;
for (i = 0; i < nsk; i++) {
if (skv[i] == NULL)
continue; /* device discarded */
skdebug(__func__, "polling %s", skv[i]->path);
if ((r = fido_dev_get_touch_status(skv[i]->dev, touch,
FIDO_POLL_MS)) != FIDO_OK) {
skdebug(__func__, "fido_dev_get_touch_status %s: %s",
skv[i]->path, fido_strerr(r));
sk_close(skv[i]); /* discard device */
skv[i] = NULL;
if (--npoll == 0) {
skdebug(__func__, "no device left to poll");
return -1;
}
} else if (*touch) {
*idx = i;
return 0;
}
}
*touch = 0;
return 0;
}
/* Calculate SHA256(m) */
static int
sha256_mem(const void *m, size_t mlen, u_char *d, size_t dlen)
{
#ifdef WITH_OPENSSL
u_int mdlen;
#else
SHA2_CTX ctx;
#endif
if (dlen != 32)
return -1;
#ifdef WITH_OPENSSL
mdlen = dlen;
if (!EVP_Digest(m, mlen, d, &mdlen, EVP_sha256(), NULL))
return -1;
#else
SHA256Init(&ctx);
SHA256Update(&ctx, (const uint8_t *)m, mlen);
SHA256Final(d, &ctx);
#endif
return 0;
}
/* Check if the specified key handle exists on a given sk. */
static int
sk_try(const struct sk_usbhid *sk, const char *application,
const uint8_t *key_handle, size_t key_handle_len)
{
fido_assert_t *assert = NULL;
/* generate an invalid signature on FIDO2 tokens */
const char *data = "";
uint8_t message[32];
int r = FIDO_ERR_INTERNAL;
if (sha256_mem(data, strlen(data), message, sizeof(message)) != 0) {
skdebug(__func__, "hash message failed");
goto out;
}
if ((assert = fido_assert_new()) == NULL) {
skdebug(__func__, "fido_assert_new failed");
goto out;
}
if ((r = fido_assert_set_clientdata_hash(assert, message,
sizeof(message))) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_clientdata_hash: %s",
fido_strerr(r));
goto out;
}
if ((r = fido_assert_set_rp(assert, application)) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_rp: %s", fido_strerr(r));
goto out;
}
if ((r = fido_assert_allow_cred(assert, key_handle,
key_handle_len)) != FIDO_OK) {
skdebug(__func__, "fido_assert_allow_cred: %s", fido_strerr(r));
goto out;
}
if ((r = fido_assert_set_up(assert, FIDO_OPT_FALSE)) != FIDO_OK) {
skdebug(__func__, "fido_assert_up: %s", fido_strerr(r));
goto out;
}
r = fido_dev_get_assert(sk->dev, assert, NULL);
skdebug(__func__, "fido_dev_get_assert: %s", fido_strerr(r));
if (r == FIDO_ERR_USER_PRESENCE_REQUIRED) {
/* U2F tokens may return this */
r = FIDO_OK;
}
out:
fido_assert_free(&assert);
return r != FIDO_OK ? -1 : 0;
}
static struct sk_usbhid *
sk_select_by_cred(const fido_dev_info_t *devlist, size_t ndevs,
const char *application, const uint8_t *key_handle, size_t key_handle_len)
{
struct sk_usbhid **skv, *sk;
size_t skvcnt, i;
if ((skv = sk_openv(devlist, ndevs, &skvcnt)) == NULL) {
skdebug(__func__, "sk_openv failed");
return NULL;
}
if (skvcnt == 1) {
sk = skv[0];
skv[0] = NULL;
goto out;
}
sk = NULL;
for (i = 0; i < skvcnt; i++) {
if (sk_try(skv[i], application, key_handle,
key_handle_len) == 0) {
sk = skv[i];
skv[i] = NULL;
skdebug(__func__, "found key in %s", sk->path);
break;
}
}
out:
sk_closev(skv, skvcnt);
return sk;
}
static struct sk_usbhid *
sk_select_by_touch(const fido_dev_info_t *devlist, size_t ndevs)
{
struct sk_usbhid **skv, *sk;
struct timeval tv_start, tv_now, tv_delta;
size_t skvcnt, idx;
int touch, ms_remain;
if ((skv = sk_openv(devlist, ndevs, &skvcnt)) == NULL) {
skdebug(__func__, "sk_openv failed");
return NULL;
}
sk = NULL;
if (skvcnt < 2) {
if (skvcnt == 1) {
/* single candidate */
sk = skv[0];
skv[0] = NULL;
}
goto out;
}
#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS
skdebug(__func__, "libfido2 version does not support a feature needed for multiple tokens. Please upgrade to >=1.5.0");
goto out;
#endif
if (sk_touch_begin(skv, skvcnt) == -1) {
skdebug(__func__, "sk_touch_begin failed");
goto out;
}
monotime_tv(&tv_start);
do {
if (sk_touch_poll(skv, skvcnt, &touch, &idx) == -1) {
skdebug(__func__, "sk_touch_poll failed");
goto out;
}
if (touch) {
sk = skv[idx];
skv[idx] = NULL;
goto out;
}
monotime_tv(&tv_now);
timersub(&tv_now, &tv_start, &tv_delta);
ms_remain = SELECT_MS - tv_delta.tv_sec * 1000 -
tv_delta.tv_usec / 1000;
} while (ms_remain >= FIDO_POLL_MS);
skdebug(__func__, "timeout");
out:
sk_closev(skv, skvcnt);
return sk;
}
static struct sk_usbhid *
sk_probe(const char *application, const uint8_t *key_handle,
size_t key_handle_len)
{
struct sk_usbhid *sk;
fido_dev_info_t *devlist;
size_t ndevs;
int r;
if ((devlist = fido_dev_info_new(MAX_FIDO_DEVICES)) == NULL) {
skdebug(__func__, "fido_dev_info_new failed");
return NULL;
}
if ((r = fido_dev_info_manifest(devlist, MAX_FIDO_DEVICES,
&ndevs)) != FIDO_OK) {
skdebug(__func__, "fido_dev_info_manifest failed: %s",
fido_strerr(r));
fido_dev_info_free(&devlist, MAX_FIDO_DEVICES);
return NULL;
}
skdebug(__func__, "%zu device(s) detected", ndevs);
if (ndevs == 0) {
sk = NULL;
} else if (application != NULL && key_handle != NULL) {
skdebug(__func__, "selecting sk by cred");
sk = sk_select_by_cred(devlist, ndevs, application, key_handle,
key_handle_len);
} else {
skdebug(__func__, "selecting sk by touch");
sk = sk_select_by_touch(devlist, ndevs);
}
fido_dev_info_free(&devlist, MAX_FIDO_DEVICES);
return sk;
}
static int
check_sk_options(fido_dev_t *dev, const char *opt, int *ret)
{
fido_cbor_info_t *info;
char * const *name;
const bool *value;
size_t len, i;
int r;
*ret = -1;
if (!fido_dev_is_fido2(dev)) {
skdebug(__func__, "device is not fido2");
return 0;
}
if ((info = fido_cbor_info_new()) == NULL) {
skdebug(__func__, "fido_cbor_info_new failed");
return -1;
}
if ((r = fido_dev_get_cbor_info(dev, info)) != FIDO_OK) {
skdebug(__func__, "fido_dev_get_cbor_info: %s", fido_strerr(r));
fido_cbor_info_free(&info);
return -1;
}
name = fido_cbor_info_options_name_ptr(info);
value = fido_cbor_info_options_value_ptr(info);
len = fido_cbor_info_options_len(info);
for (i = 0; i < len; i++) {
if (!strcmp(name[i], opt)) {
*ret = value[i];
break;
}
}
fido_cbor_info_free(&info);
if (*ret == -1)
skdebug(__func__, "option %s is unknown", opt);
else
skdebug(__func__, "option %s is %s", opt, *ret ? "on" : "off");
return 0;
}
#ifdef WITH_OPENSSL
/*
* The key returned via fido_cred_pubkey_ptr() is in affine coordinates,
* but the API expects a SEC1 octet string.
*/
static int
pack_public_key_ecdsa(const fido_cred_t *cred,
struct sk_enroll_response *response)
{
const uint8_t *ptr;
BIGNUM *x = NULL, *y = NULL;
EC_POINT *q = NULL;
EC_GROUP *g = NULL;
int ret = -1;
response->public_key = NULL;
response->public_key_len = 0;
if ((x = BN_new()) == NULL ||
(y = BN_new()) == NULL ||
(g = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)) == NULL ||
(q = EC_POINT_new(g)) == NULL) {
skdebug(__func__, "libcrypto setup failed");
goto out;
}
if ((ptr = fido_cred_pubkey_ptr(cred)) == NULL) {
skdebug(__func__, "fido_cred_pubkey_ptr failed");
goto out;
}
if (fido_cred_pubkey_len(cred) != 64) {
skdebug(__func__, "bad fido_cred_pubkey_len %zu",
fido_cred_pubkey_len(cred));
goto out;
}
if (BN_bin2bn(ptr, 32, x) == NULL ||
BN_bin2bn(ptr + 32, 32, y) == NULL) {
skdebug(__func__, "BN_bin2bn failed");
goto out;
}
if (EC_POINT_set_affine_coordinates_GFp(g, q, x, y, NULL) != 1) {
skdebug(__func__, "EC_POINT_set_affine_coordinates_GFp failed");
goto out;
}
response->public_key_len = EC_POINT_point2oct(g, q,
POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL);
if (response->public_key_len == 0 || response->public_key_len > 2048) {
skdebug(__func__, "bad pubkey length %zu",
response->public_key_len);
goto out;
}
if ((response->public_key = malloc(response->public_key_len)) == NULL) {
skdebug(__func__, "malloc pubkey failed");
goto out;
}
if (EC_POINT_point2oct(g, q, POINT_CONVERSION_UNCOMPRESSED,
response->public_key, response->public_key_len, NULL) == 0) {
skdebug(__func__, "EC_POINT_point2oct failed");
goto out;
}
/* success */
ret = 0;
out:
if (ret != 0 && response->public_key != NULL) {
memset(response->public_key, 0, response->public_key_len);
free(response->public_key);
response->public_key = NULL;
}
EC_POINT_free(q);
EC_GROUP_free(g);
BN_clear_free(x);
BN_clear_free(y);
return ret;
}
#endif /* WITH_OPENSSL */
static int
pack_public_key_ed25519(const fido_cred_t *cred,
struct sk_enroll_response *response)
{
const uint8_t *ptr;
size_t len;
int ret = -1;
response->public_key = NULL;
response->public_key_len = 0;
if ((len = fido_cred_pubkey_len(cred)) != 32) {
skdebug(__func__, "bad fido_cred_pubkey_len len %zu", len);
goto out;
}
if ((ptr = fido_cred_pubkey_ptr(cred)) == NULL) {
skdebug(__func__, "fido_cred_pubkey_ptr failed");
goto out;
}
response->public_key_len = len;
if ((response->public_key = malloc(response->public_key_len)) == NULL) {
skdebug(__func__, "malloc pubkey failed");
goto out;
}
memcpy(response->public_key, ptr, len);
ret = 0;
out:
if (ret != 0)
free(response->public_key);
return ret;
}
static int
pack_public_key(uint32_t alg, const fido_cred_t *cred,
struct sk_enroll_response *response)
{
switch(alg) {
#ifdef WITH_OPENSSL
case SSH_SK_ECDSA:
return pack_public_key_ecdsa(cred, response);
#endif /* WITH_OPENSSL */
case SSH_SK_ED25519:
return pack_public_key_ed25519(cred, response);
default:
return -1;
}
}
static int
fidoerr_to_skerr(int fidoerr)
{
switch (fidoerr) {
case FIDO_ERR_UNSUPPORTED_OPTION:
case FIDO_ERR_UNSUPPORTED_ALGORITHM:
return SSH_SK_ERR_UNSUPPORTED;
case FIDO_ERR_PIN_REQUIRED:
case FIDO_ERR_PIN_INVALID:
case FIDO_ERR_OPERATION_DENIED:
return SSH_SK_ERR_PIN_REQUIRED;
default:
return -1;
}
}
static int
check_enroll_options(struct sk_option **options, char **devicep,
uint8_t *user_id, size_t user_id_len)
{
size_t i;
if (options == NULL)
return 0;
for (i = 0; options[i] != NULL; i++) {
if (strcmp(options[i]->name, "device") == 0) {
if ((*devicep = strdup(options[i]->value)) == NULL) {
skdebug(__func__, "strdup device failed");
return -1;
}
skdebug(__func__, "requested device %s", *devicep);
} else if (strcmp(options[i]->name, "user") == 0) {
if (strlcpy(user_id, options[i]->value, user_id_len) >=
user_id_len) {
skdebug(__func__, "user too long");
return -1;
}
skdebug(__func__, "requested user %s",
(char *)user_id);
} else {
skdebug(__func__, "requested unsupported option %s",
options[i]->name);
if (options[i]->required) {
skdebug(__func__, "unknown required option");
return -1;
}
}
}
return 0;
}
int
sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
const char *application, uint8_t flags, const char *pin,
struct sk_option **options, struct sk_enroll_response **enroll_response)
{
fido_cred_t *cred = NULL;
const uint8_t *ptr;
uint8_t user_id[32], chall_hash[32];
struct sk_usbhid *sk = NULL;
struct sk_enroll_response *response = NULL;
size_t len;
int credprot;
int internal_uv;
int cose_alg;
int ret = SSH_SK_ERR_GENERAL;
int r;
char *device = NULL;
fido_init(SSH_FIDO_INIT_ARG);
if (enroll_response == NULL) {
skdebug(__func__, "enroll_response == NULL");
goto out;
}
*enroll_response = NULL;
memset(user_id, 0, sizeof(user_id));
if (check_enroll_options(options, &device, user_id,
sizeof(user_id)) != 0)
goto out; /* error already logged */
switch(alg) {
#ifdef WITH_OPENSSL
case SSH_SK_ECDSA:
cose_alg = COSE_ES256;
break;
#endif /* WITH_OPENSSL */
case SSH_SK_ED25519:
cose_alg = COSE_EDDSA;
break;
default:
skdebug(__func__, "unsupported key type %d", alg);
goto out;
}
if (device != NULL)
sk = sk_open(device);
else
sk = sk_probe(NULL, NULL, 0);
if (sk == NULL) {
skdebug(__func__, "failed to find sk");
goto out;
}
skdebug(__func__, "using device %s", sk->path);
if ((cred = fido_cred_new()) == NULL) {
skdebug(__func__, "fido_cred_new failed");
goto out;
}
if ((r = fido_cred_set_type(cred, cose_alg)) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_type: %s", fido_strerr(r));
goto out;
}
if (sha256_mem(challenge, challenge_len,
chall_hash, sizeof(chall_hash)) != 0) {
skdebug(__func__, "hash challenge failed");
goto out;
}
if ((r = fido_cred_set_clientdata_hash(cred, chall_hash,
sizeof(chall_hash))) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_clientdata_hash: %s",
fido_strerr(r));
goto out;
}
if ((r = fido_cred_set_rk(cred, (flags & SSH_SK_RESIDENT_KEY) != 0 ?
FIDO_OPT_TRUE : FIDO_OPT_OMIT)) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_rk: %s", fido_strerr(r));
goto out;
}
if ((r = fido_cred_set_user(cred, user_id, sizeof(user_id),
"openssh", "openssh", NULL)) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_user: %s", fido_strerr(r));
goto out;
}
if ((r = fido_cred_set_rp(cred, application, NULL)) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_rp: %s", fido_strerr(r));
goto out;
}
if ((flags & (SSH_SK_RESIDENT_KEY|SSH_SK_USER_VERIFICATION_REQD)) != 0) {
#if !defined(HAVE_FIDO_DEV_SUPPORTS_CRED_PROT) || \
!defined(HAVE_FIDO_CRED_SET_PROT)
skdebug(__func__, "libfido2 version does not support a feature required for this operation. Please upgrade to >=1.5.0");
ret = SSH_SK_ERR_UNSUPPORTED;
goto out;
credprot = 0; (void)credprot; /* avoid warning */
#endif
if (!fido_dev_supports_cred_prot(sk->dev)) {
skdebug(__func__, "%s does not support credprot, "
"refusing to create unprotected "
"resident/verify-required key", sk->path);
ret = SSH_SK_ERR_UNSUPPORTED;
goto out;
}
if ((flags & SSH_SK_USER_VERIFICATION_REQD))
credprot = FIDO_CRED_PROT_UV_REQUIRED;
else
credprot = FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID;
if ((r = fido_cred_set_prot(cred, credprot)) != FIDO_OK) {
skdebug(__func__, "fido_cred_set_prot: %s",
fido_strerr(r));
ret = fidoerr_to_skerr(r);
goto out;
}
}
if ((r = fido_dev_make_cred(sk->dev, cred, pin)) != FIDO_OK) {
skdebug(__func__, "fido_dev_make_cred: %s", fido_strerr(r));
ret = fidoerr_to_skerr(r);
goto out;
}
if (fido_cred_x5c_ptr(cred) != NULL) {
if ((r = fido_cred_verify(cred)) != FIDO_OK) {
skdebug(__func__, "fido_cred_verify: %s",
fido_strerr(r));
goto out;
}
} else {
skdebug(__func__, "self-attested credential");
if ((r = fido_cred_verify_self(cred)) != FIDO_OK) {
skdebug(__func__, "fido_cred_verify_self: %s",
fido_strerr(r));
goto out;
}
}
if ((response = calloc(1, sizeof(*response))) == NULL) {
skdebug(__func__, "calloc response failed");
goto out;
}
response->flags = flags;
if ((flags & SSH_SK_USER_VERIFICATION_REQD)) {
if (check_sk_options(sk->dev, "uv", &internal_uv) == 0 &&
internal_uv != -1) {
/* user verification handled by token */
response->flags &= ~SSH_SK_USER_VERIFICATION_REQD;
}
}
if (pack_public_key(alg, cred, response) != 0) {
skdebug(__func__, "pack_public_key failed");
goto out;
}
if ((ptr = fido_cred_id_ptr(cred)) != NULL) {
len = fido_cred_id_len(cred);
if ((response->key_handle = calloc(1, len)) == NULL) {
skdebug(__func__, "calloc key handle failed");
goto out;
}
memcpy(response->key_handle, ptr, len);
response->key_handle_len = len;
}
if ((ptr = fido_cred_sig_ptr(cred)) != NULL) {
len = fido_cred_sig_len(cred);
if ((response->signature = calloc(1, len)) == NULL) {
skdebug(__func__, "calloc signature failed");
goto out;
}
memcpy(response->signature, ptr, len);
response->signature_len = len;
}
if ((ptr = fido_cred_x5c_ptr(cred)) != NULL) {
len = fido_cred_x5c_len(cred);
skdebug(__func__, "attestation cert len=%zu", len);
if ((response->attestation_cert = calloc(1, len)) == NULL) {
skdebug(__func__, "calloc attestation cert failed");
goto out;
}
memcpy(response->attestation_cert, ptr, len);
response->attestation_cert_len = len;
}
if ((ptr = fido_cred_authdata_ptr(cred)) != NULL) {
len = fido_cred_authdata_len(cred);
skdebug(__func__, "authdata len=%zu", len);
if ((response->authdata = calloc(1, len)) == NULL) {
skdebug(__func__, "calloc authdata failed");
goto out;
}
memcpy(response->authdata, ptr, len);
response->authdata_len = len;
}
*enroll_response = response;
response = NULL;
ret = 0;
out:
free(device);
if (response != NULL) {
free(response->public_key);
free(response->key_handle);
free(response->signature);
free(response->attestation_cert);
free(response->authdata);
free(response);
}
sk_close(sk);
fido_cred_free(&cred);
return ret;
}
#ifdef WITH_OPENSSL
static int
pack_sig_ecdsa(fido_assert_t *assert, struct sk_sign_response *response)
{
ECDSA_SIG *sig = NULL;
const BIGNUM *sig_r, *sig_s;
const unsigned char *cp;
size_t sig_len;
int ret = -1;
cp = fido_assert_sig_ptr(assert, 0);
sig_len = fido_assert_sig_len(assert, 0);
if ((sig = d2i_ECDSA_SIG(NULL, &cp, sig_len)) == NULL) {
skdebug(__func__, "d2i_ECDSA_SIG failed");
goto out;
}
ECDSA_SIG_get0(sig, &sig_r, &sig_s);
response->sig_r_len = BN_num_bytes(sig_r);
response->sig_s_len = BN_num_bytes(sig_s);
if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL ||
(response->sig_s = calloc(1, response->sig_s_len)) == NULL) {
skdebug(__func__, "calloc signature failed");
goto out;
}
BN_bn2bin(sig_r, response->sig_r);
BN_bn2bin(sig_s, response->sig_s);
ret = 0;
out:
ECDSA_SIG_free(sig);
if (ret != 0) {
free(response->sig_r);
free(response->sig_s);
response->sig_r = NULL;
response->sig_s = NULL;
}
return ret;
}
#endif /* WITH_OPENSSL */
static int
pack_sig_ed25519(fido_assert_t *assert, struct sk_sign_response *response)
{
const unsigned char *ptr;
size_t len;
int ret = -1;
ptr = fido_assert_sig_ptr(assert, 0);
len = fido_assert_sig_len(assert, 0);
if (len != 64) {
skdebug(__func__, "bad length %zu", len);
goto out;
}
response->sig_r_len = len;
if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL) {
skdebug(__func__, "calloc signature failed");
goto out;
}
memcpy(response->sig_r, ptr, len);
ret = 0;
out:
if (ret != 0) {
free(response->sig_r);
response->sig_r = NULL;
}
return ret;
}
static int
pack_sig(uint32_t alg, fido_assert_t *assert,
struct sk_sign_response *response)
{
switch(alg) {
#ifdef WITH_OPENSSL
case SSH_SK_ECDSA:
return pack_sig_ecdsa(assert, response);
#endif /* WITH_OPENSSL */
case SSH_SK_ED25519:
return pack_sig_ed25519(assert, response);
default:
return -1;
}
}
/* Checks sk_options for sk_sign() and sk_load_resident_keys() */
static int
check_sign_load_resident_options(struct sk_option **options, char **devicep)
{
size_t i;
if (options == NULL)
return 0;
for (i = 0; options[i] != NULL; i++) {
if (strcmp(options[i]->name, "device") == 0) {
if ((*devicep = strdup(options[i]->value)) == NULL) {
skdebug(__func__, "strdup device failed");
return -1;
}
skdebug(__func__, "requested device %s", *devicep);
} else {
skdebug(__func__, "requested unsupported option %s",
options[i]->name);
if (options[i]->required) {
skdebug(__func__, "unknown required option");
return -1;
}
}
}
return 0;
}
int
sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
const char *application,
const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, const char *pin, struct sk_option **options,
struct sk_sign_response **sign_response)
{
fido_assert_t *assert = NULL;
char *device = NULL;
struct sk_usbhid *sk = NULL;
struct sk_sign_response *response = NULL;
uint8_t message[32];
int ret = SSH_SK_ERR_GENERAL, internal_uv;
int r;
fido_init(SSH_FIDO_INIT_ARG);
if (sign_response == NULL) {
skdebug(__func__, "sign_response == NULL");
goto out;
}
*sign_response = NULL;
if (check_sign_load_resident_options(options, &device) != 0)
goto out; /* error already logged */
/* hash data to be signed before it goes to the security key */
if ((r = sha256_mem(data, datalen, message, sizeof(message))) != 0) {
skdebug(__func__, "hash message failed");
goto out;
}
if (device != NULL)
sk = sk_open(device);
else if (pin != NULL || (flags & SSH_SK_USER_VERIFICATION_REQD))
sk = sk_probe(NULL, NULL, 0);
else
sk = sk_probe(application, key_handle, key_handle_len);
if (sk == NULL) {
skdebug(__func__, "failed to find sk");
goto out;
}
if ((assert = fido_assert_new()) == NULL) {
skdebug(__func__, "fido_assert_new failed");
goto out;
}
if ((r = fido_assert_set_clientdata_hash(assert, message,
sizeof(message))) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_clientdata_hash: %s",
fido_strerr(r));
goto out;
}
if ((r = fido_assert_set_rp(assert, application)) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_rp: %s", fido_strerr(r));
goto out;
}
if ((r = fido_assert_allow_cred(assert, key_handle,
key_handle_len)) != FIDO_OK) {
skdebug(__func__, "fido_assert_allow_cred: %s", fido_strerr(r));
goto out;
}
if ((r = fido_assert_set_up(assert,
(flags & SSH_SK_USER_PRESENCE_REQD) ?
FIDO_OPT_TRUE : FIDO_OPT_FALSE)) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_up: %s", fido_strerr(r));
goto out;
}
if (pin == NULL && (flags & SSH_SK_USER_VERIFICATION_REQD)) {
if (check_sk_options(sk->dev, "uv", &internal_uv) < 0 ||
internal_uv != 1) {
skdebug(__func__, "check_sk_options uv");
ret = SSH_SK_ERR_PIN_REQUIRED;
goto out;
}
if ((r = fido_assert_set_uv(assert,
FIDO_OPT_TRUE)) != FIDO_OK) {
skdebug(__func__, "fido_assert_set_uv: %s",
fido_strerr(r));
ret = fidoerr_to_skerr(r);
goto out;
}
}
if ((r = fido_dev_get_assert(sk->dev, assert, pin)) != FIDO_OK) {
skdebug(__func__, "fido_dev_get_assert: %s", fido_strerr(r));
ret = fidoerr_to_skerr(r);
goto out;
}
if ((response = calloc(1, sizeof(*response))) == NULL) {
skdebug(__func__, "calloc response failed");
goto out;
}
response->flags = fido_assert_flags(assert, 0);
response->counter = fido_assert_sigcount(assert, 0);
if (pack_sig(alg, assert, response) != 0) {
skdebug(__func__, "pack_sig failed");
goto out;
}
*sign_response = response;
response = NULL;
ret = 0;
out:
explicit_bzero(message, sizeof(message));
free(device);
if (response != NULL) {
free(response->sig_r);
free(response->sig_s);
free(response);
}
sk_close(sk);
fido_assert_free(&assert);
return ret;
}
static int
read_rks(struct sk_usbhid *sk, const char *pin,
struct sk_resident_key ***rksp, size_t *nrksp)
{
int ret = SSH_SK_ERR_GENERAL, r = -1, internal_uv;
fido_credman_metadata_t *metadata = NULL;
fido_credman_rp_t *rp = NULL;
fido_credman_rk_t *rk = NULL;
size_t i, j, nrp, nrk, user_id_len;
const fido_cred_t *cred;
const char *rp_id, *rp_name, *user_name;
struct sk_resident_key *srk = NULL, **tmp;
const u_char *user_id;
if (pin == NULL) {
skdebug(__func__, "no PIN specified");
ret = SSH_SK_ERR_PIN_REQUIRED;
goto out;
}
if ((metadata = fido_credman_metadata_new()) == NULL) {
skdebug(__func__, "alloc failed");
goto out;
}
if (check_sk_options(sk->dev, "uv", &internal_uv) != 0) {
skdebug(__func__, "check_sk_options failed");
goto out;
}
if ((r = fido_credman_get_dev_metadata(sk->dev, metadata, pin)) != 0) {
if (r == FIDO_ERR_INVALID_COMMAND) {
skdebug(__func__, "device %s does not support "
"resident keys", sk->path);
ret = 0;
goto out;
}
skdebug(__func__, "get metadata for %s failed: %s",
sk->path, fido_strerr(r));
ret = fidoerr_to_skerr(r);
goto out;
}
skdebug(__func__, "existing %llu, remaining %llu",
(unsigned long long)fido_credman_rk_existing(metadata),
(unsigned long long)fido_credman_rk_remaining(metadata));
if ((rp = fido_credman_rp_new()) == NULL) {
skdebug(__func__, "alloc rp failed");
goto out;
}
if ((r = fido_credman_get_dev_rp(sk->dev, rp, pin)) != 0) {
skdebug(__func__, "get RPs for %s failed: %s",
sk->path, fido_strerr(r));
goto out;
}
nrp = fido_credman_rp_count(rp);
skdebug(__func__, "Device %s has resident keys for %zu RPs",
sk->path, nrp);
/* Iterate over RP IDs that have resident keys */
for (i = 0; i < nrp; i++) {
rp_id = fido_credman_rp_id(rp, i);
rp_name = fido_credman_rp_name(rp, i);
skdebug(__func__, "rp %zu: name=\"%s\" id=\"%s\" hashlen=%zu",
i, rp_name == NULL ? "(none)" : rp_name,
rp_id == NULL ? "(none)" : rp_id,
fido_credman_rp_id_hash_len(rp, i));
/* Skip non-SSH RP IDs */
if (rp_id == NULL ||
strncasecmp(fido_credman_rp_id(rp, i), "ssh:", 4) != 0)
continue;
fido_credman_rk_free(&rk);
if ((rk = fido_credman_rk_new()) == NULL) {
skdebug(__func__, "alloc rk failed");
goto out;
}
if ((r = fido_credman_get_dev_rk(sk->dev,
fido_credman_rp_id(rp, i), rk, pin)) != 0) {
skdebug(__func__, "get RKs for %s slot %zu failed: %s",
sk->path, i, fido_strerr(r));
goto out;
}
nrk = fido_credman_rk_count(rk);
skdebug(__func__, "RP \"%s\" has %zu resident keys",
fido_credman_rp_id(rp, i), nrk);
/* Iterate over resident keys for this RP ID */
for (j = 0; j < nrk; j++) {
if ((cred = fido_credman_rk(rk, j)) == NULL) {
skdebug(__func__, "no RK in slot %zu", j);
continue;
}
if ((user_name = fido_cred_user_name(cred)) == NULL)
user_name = "";
user_id = fido_cred_user_id_ptr(cred);
user_id_len = fido_cred_user_id_len(cred);
skdebug(__func__, "Device %s RP \"%s\" user \"%s\" "
"uidlen %zu slot %zu: type %d flags 0x%02x "
"prot 0x%02x", sk->path, rp_id, user_name,
user_id_len, j, fido_cred_type(cred),
fido_cred_flags(cred), fido_cred_prot(cred));
/* build response entry */
if ((srk = calloc(1, sizeof(*srk))) == NULL ||
(srk->key.key_handle = calloc(1,
fido_cred_id_len(cred))) == NULL ||
(srk->application = strdup(rp_id)) == NULL ||
(user_id_len > 0 &&
(srk->user_id = calloc(1, user_id_len)) == NULL)) {
skdebug(__func__, "alloc sk_resident_key");
goto out;
}
srk->key.key_handle_len = fido_cred_id_len(cred);
memcpy(srk->key.key_handle, fido_cred_id_ptr(cred),
srk->key.key_handle_len);
srk->user_id_len = user_id_len;
if (srk->user_id_len != 0)
memcpy(srk->user_id, user_id, srk->user_id_len);
switch (fido_cred_type(cred)) {
case COSE_ES256:
srk->alg = SSH_SK_ECDSA;
break;
case COSE_EDDSA:
srk->alg = SSH_SK_ED25519;
break;
default:
skdebug(__func__, "unsupported key type %d",
fido_cred_type(cred));
goto out; /* XXX free rk and continue */
}
if (fido_cred_prot(cred) == FIDO_CRED_PROT_UV_REQUIRED
&& internal_uv == -1)
srk->flags |= SSH_SK_USER_VERIFICATION_REQD;
if ((r = pack_public_key(srk->alg, cred,
&srk->key)) != 0) {
skdebug(__func__, "pack public key failed");
goto out;
}
/* append */
if ((tmp = recallocarray(*rksp, *nrksp, (*nrksp) + 1,
sizeof(**rksp))) == NULL) {
skdebug(__func__, "alloc rksp");
goto out;
}
*rksp = tmp;
(*rksp)[(*nrksp)++] = srk;
srk = NULL;
}
}
/* Success */
ret = 0;
out:
if (srk != NULL) {
free(srk->application);
freezero(srk->key.public_key, srk->key.public_key_len);
freezero(srk->key.key_handle, srk->key.key_handle_len);
freezero(srk->user_id, srk->user_id_len);
freezero(srk, sizeof(*srk));
}
fido_credman_rp_free(&rp);
fido_credman_rk_free(&rk);
fido_credman_metadata_free(&metadata);
return ret;
}
int
sk_load_resident_keys(const char *pin, struct sk_option **options,
struct sk_resident_key ***rksp, size_t *nrksp)
{
int ret = SSH_SK_ERR_GENERAL, r = -1;
size_t i, nrks = 0;
struct sk_resident_key **rks = NULL;
struct sk_usbhid *sk = NULL;
char *device = NULL;
*rksp = NULL;
*nrksp = 0;
fido_init(SSH_FIDO_INIT_ARG);
if (check_sign_load_resident_options(options, &device) != 0)
goto out; /* error already logged */
if (device != NULL)
sk = sk_open(device);
else
sk = sk_probe(NULL, NULL, 0);
if (sk == NULL) {
skdebug(__func__, "failed to find sk");
goto out;
}
skdebug(__func__, "trying %s", sk->path);
if ((r = read_rks(sk, pin, &rks, &nrks)) != 0) {
skdebug(__func__, "read_rks failed for %s", sk->path);
ret = r;
goto out;
}
/* success, unless we have no keys but a specific error */
if (nrks > 0 || ret == SSH_SK_ERR_GENERAL)
ret = 0;
*rksp = rks;
*nrksp = nrks;
rks = NULL;
nrks = 0;
out:
sk_close(sk);
for (i = 0; i < nrks; i++) {
free(rks[i]->application);
freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
freezero(rks[i]->user_id, rks[i]->user_id_len);
freezero(rks[i], sizeof(*rks[i]));
}
free(rks);
return ret;
}
#endif /* ENABLE_SK_INTERNAL */
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