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533 lines
14 KiB
533 lines
14 KiB
/*
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* Copyright (c) 2019 Markus Friedl
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "includes.h"
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#ifdef HAVE_STDINT_H
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#include <stdint.h>
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#endif
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <stddef.h>
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#include <stdarg.h>
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#include "crypto_api.h"
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#include "sk-api.h"
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#include <openssl/opensslv.h>
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#include <openssl/crypto.h>
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#include <openssl/evp.h>
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#include <openssl/bn.h>
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#include <openssl/ec.h>
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#include <openssl/ecdsa.h>
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#include <openssl/pem.h>
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/* #define SK_DEBUG 1 */
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/* Compatibility with OpenSSH 1.0.x */
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#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
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#define ECDSA_SIG_get0(sig, pr, ps) \
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do { \
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(*pr) = sig->r; \
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(*ps) = sig->s; \
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} while (0)
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#endif
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#if SSH_SK_VERSION_MAJOR != 0x00050000
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# error SK API has changed, sk-dummy.c needs an update
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#endif
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static void skdebug(const char *func, const char *fmt, ...)
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__attribute__((__format__ (printf, 2, 3)));
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static void
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skdebug(const char *func, const char *fmt, ...)
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{
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#if defined(SK_DEBUG)
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va_list ap;
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va_start(ap, fmt);
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fprintf(stderr, "sk-dummy %s: ", func);
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vfprintf(stderr, fmt, ap);
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fputc('\n', stderr);
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va_end(ap);
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#else
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(void)func; /* XXX */
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(void)fmt; /* XXX */
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#endif
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}
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uint32_t
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sk_api_version(void)
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{
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return SSH_SK_VERSION_MAJOR;
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}
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static int
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pack_key_ecdsa(struct sk_enroll_response *response)
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{
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#ifdef OPENSSL_HAS_ECC
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EC_KEY *key = NULL;
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const EC_GROUP *g;
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const EC_POINT *q;
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int ret = -1;
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long privlen;
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BIO *bio = NULL;
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char *privptr;
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response->public_key = NULL;
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response->public_key_len = 0;
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response->key_handle = NULL;
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response->key_handle_len = 0;
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if ((key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1)) == NULL) {
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skdebug(__func__, "EC_KEY_new_by_curve_name");
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goto out;
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}
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if (EC_KEY_generate_key(key) != 1) {
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skdebug(__func__, "EC_KEY_generate_key");
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goto out;
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}
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EC_KEY_set_asn1_flag(key, OPENSSL_EC_NAMED_CURVE);
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if ((bio = BIO_new(BIO_s_mem())) == NULL ||
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(g = EC_KEY_get0_group(key)) == NULL ||
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(q = EC_KEY_get0_public_key(key)) == NULL) {
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skdebug(__func__, "couldn't get key parameters");
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goto out;
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}
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response->public_key_len = EC_POINT_point2oct(g, q,
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POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL);
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if (response->public_key_len == 0 || response->public_key_len > 2048) {
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skdebug(__func__, "bad pubkey length %zu",
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response->public_key_len);
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goto out;
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}
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if ((response->public_key = malloc(response->public_key_len)) == NULL) {
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skdebug(__func__, "malloc pubkey failed");
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goto out;
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}
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if (EC_POINT_point2oct(g, q, POINT_CONVERSION_UNCOMPRESSED,
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response->public_key, response->public_key_len, NULL) == 0) {
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skdebug(__func__, "EC_POINT_point2oct failed");
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goto out;
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}
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/* Key handle contains PEM encoded private key */
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if (!PEM_write_bio_ECPrivateKey(bio, key, NULL, NULL, 0, NULL, NULL)) {
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skdebug(__func__, "PEM_write_bio_ECPrivateKey failed");
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goto out;
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}
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if ((privlen = BIO_get_mem_data(bio, &privptr)) <= 0) {
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skdebug(__func__, "BIO_get_mem_data failed");
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goto out;
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}
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if ((response->key_handle = malloc(privlen)) == NULL) {
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skdebug(__func__, "malloc key_handle failed");
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goto out;
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}
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response->key_handle_len = (size_t)privlen;
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memcpy(response->key_handle, privptr, response->key_handle_len);
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/* success */
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ret = 0;
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out:
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if (ret != 0) {
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if (response->public_key != NULL) {
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memset(response->public_key, 0,
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response->public_key_len);
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free(response->public_key);
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response->public_key = NULL;
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}
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if (response->key_handle != NULL) {
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memset(response->key_handle, 0,
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response->key_handle_len);
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free(response->key_handle);
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response->key_handle = NULL;
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}
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}
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BIO_free(bio);
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EC_KEY_free(key);
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return ret;
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#else
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return -1;
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#endif
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}
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static int
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pack_key_ed25519(struct sk_enroll_response *response)
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{
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int ret = -1;
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u_char pk[crypto_sign_ed25519_PUBLICKEYBYTES];
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u_char sk[crypto_sign_ed25519_SECRETKEYBYTES];
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response->public_key = NULL;
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response->public_key_len = 0;
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response->key_handle = NULL;
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response->key_handle_len = 0;
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memset(pk, 0, sizeof(pk));
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memset(sk, 0, sizeof(sk));
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crypto_sign_ed25519_keypair(pk, sk);
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response->public_key_len = sizeof(pk);
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if ((response->public_key = malloc(response->public_key_len)) == NULL) {
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skdebug(__func__, "malloc pubkey failed");
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goto out;
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}
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memcpy(response->public_key, pk, sizeof(pk));
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/* Key handle contains sk */
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response->key_handle_len = sizeof(sk);
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if ((response->key_handle = malloc(response->key_handle_len)) == NULL) {
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skdebug(__func__, "malloc key_handle failed");
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goto out;
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}
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memcpy(response->key_handle, sk, sizeof(sk));
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/* success */
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ret = 0;
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out:
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if (ret != 0)
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free(response->public_key);
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return ret;
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}
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static int
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check_options(struct sk_option **options)
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{
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size_t i;
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if (options == NULL)
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return 0;
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for (i = 0; options[i] != NULL; i++) {
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skdebug(__func__, "requested unsupported option %s",
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options[i]->name);
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if (options[i]->required) {
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skdebug(__func__, "unknown required option");
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return -1;
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}
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}
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return 0;
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}
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int
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sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
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const char *application, uint8_t flags, const char *pin,
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struct sk_option **options, struct sk_enroll_response **enroll_response)
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{
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struct sk_enroll_response *response = NULL;
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int ret = SSH_SK_ERR_GENERAL;
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(void)flags; /* XXX; unused */
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if (enroll_response == NULL) {
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skdebug(__func__, "enroll_response == NULL");
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goto out;
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}
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*enroll_response = NULL;
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if (check_options(options) != 0)
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goto out; /* error already logged */
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if ((response = calloc(1, sizeof(*response))) == NULL) {
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skdebug(__func__, "calloc response failed");
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goto out;
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}
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switch(alg) {
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case SSH_SK_ECDSA:
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if (pack_key_ecdsa(response) != 0)
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goto out;
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break;
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case SSH_SK_ED25519:
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if (pack_key_ed25519(response) != 0)
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goto out;
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break;
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default:
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skdebug(__func__, "unsupported key type %d", alg);
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return -1;
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}
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/* Have to return something here */
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if ((response->signature = calloc(1, 1)) == NULL) {
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skdebug(__func__, "calloc signature failed");
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goto out;
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}
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response->signature_len = 0;
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*enroll_response = response;
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response = NULL;
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ret = 0;
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out:
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if (response != NULL) {
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free(response->public_key);
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free(response->key_handle);
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free(response->signature);
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free(response->attestation_cert);
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free(response);
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}
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return ret;
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}
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static void
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dump(const char *preamble, const void *sv, size_t l)
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{
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#ifdef SK_DEBUG
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const u_char *s = (const u_char *)sv;
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size_t i;
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fprintf(stderr, "%s (len %zu):\n", preamble, l);
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for (i = 0; i < l; i++) {
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if (i % 16 == 0)
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fprintf(stderr, "%04zu: ", i);
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fprintf(stderr, "%02x", s[i]);
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if (i % 16 == 15 || i == l - 1)
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fprintf(stderr, "\n");
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}
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#endif
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}
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static int
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sig_ecdsa(const uint8_t *message, size_t message_len,
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const char *application, uint32_t counter, uint8_t flags,
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const uint8_t *key_handle, size_t key_handle_len,
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struct sk_sign_response *response)
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{
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#ifdef OPENSSL_HAS_ECC
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ECDSA_SIG *sig = NULL;
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const BIGNUM *sig_r, *sig_s;
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int ret = -1;
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BIO *bio = NULL;
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EVP_PKEY *pk = NULL;
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EC_KEY *ec = NULL;
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SHA256_CTX ctx;
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uint8_t apphash[SHA256_DIGEST_LENGTH];
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uint8_t sighash[SHA256_DIGEST_LENGTH];
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uint8_t countbuf[4];
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/* Decode EC_KEY from key handle */
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if ((bio = BIO_new(BIO_s_mem())) == NULL ||
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BIO_write(bio, key_handle, key_handle_len) != (int)key_handle_len) {
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skdebug(__func__, "BIO setup failed");
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goto out;
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}
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if ((pk = PEM_read_bio_PrivateKey(bio, NULL, NULL, "")) == NULL) {
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skdebug(__func__, "PEM_read_bio_PrivateKey failed");
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goto out;
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}
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if (EVP_PKEY_base_id(pk) != EVP_PKEY_EC) {
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skdebug(__func__, "Not an EC key: %d", EVP_PKEY_base_id(pk));
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goto out;
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}
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if ((ec = EVP_PKEY_get1_EC_KEY(pk)) == NULL) {
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skdebug(__func__, "EVP_PKEY_get1_EC_KEY failed");
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goto out;
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}
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/* Expect message to be pre-hashed */
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if (message_len != SHA256_DIGEST_LENGTH) {
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skdebug(__func__, "bad message len %zu", message_len);
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goto out;
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}
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/* Prepare data to be signed */
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dump("message", message, message_len);
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SHA256_Init(&ctx);
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SHA256_Update(&ctx, application, strlen(application));
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SHA256_Final(apphash, &ctx);
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dump("apphash", apphash, sizeof(apphash));
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countbuf[0] = (counter >> 24) & 0xff;
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countbuf[1] = (counter >> 16) & 0xff;
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countbuf[2] = (counter >> 8) & 0xff;
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countbuf[3] = counter & 0xff;
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dump("countbuf", countbuf, sizeof(countbuf));
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dump("flags", &flags, sizeof(flags));
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SHA256_Init(&ctx);
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SHA256_Update(&ctx, apphash, sizeof(apphash));
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SHA256_Update(&ctx, &flags, sizeof(flags));
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SHA256_Update(&ctx, countbuf, sizeof(countbuf));
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SHA256_Update(&ctx, message, message_len);
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SHA256_Final(sighash, &ctx);
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dump("sighash", sighash, sizeof(sighash));
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/* create and encode signature */
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if ((sig = ECDSA_do_sign(sighash, sizeof(sighash), ec)) == NULL) {
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skdebug(__func__, "ECDSA_do_sign failed");
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goto out;
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}
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ECDSA_SIG_get0(sig, &sig_r, &sig_s);
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response->sig_r_len = BN_num_bytes(sig_r);
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response->sig_s_len = BN_num_bytes(sig_s);
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if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL ||
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(response->sig_s = calloc(1, response->sig_s_len)) == NULL) {
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skdebug(__func__, "calloc signature failed");
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goto out;
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}
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BN_bn2bin(sig_r, response->sig_r);
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BN_bn2bin(sig_s, response->sig_s);
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ret = 0;
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out:
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explicit_bzero(&ctx, sizeof(ctx));
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explicit_bzero(&apphash, sizeof(apphash));
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explicit_bzero(&sighash, sizeof(sighash));
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ECDSA_SIG_free(sig);
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if (ret != 0) {
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free(response->sig_r);
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free(response->sig_s);
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response->sig_r = NULL;
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response->sig_s = NULL;
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}
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BIO_free(bio);
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EC_KEY_free(ec);
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EVP_PKEY_free(pk);
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return ret;
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#else
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return -1;
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#endif
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}
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static int
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sig_ed25519(const uint8_t *message, size_t message_len,
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const char *application, uint32_t counter, uint8_t flags,
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const uint8_t *key_handle, size_t key_handle_len,
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struct sk_sign_response *response)
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{
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size_t o;
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int ret = -1;
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SHA256_CTX ctx;
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uint8_t apphash[SHA256_DIGEST_LENGTH];
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uint8_t signbuf[sizeof(apphash) + sizeof(flags) +
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sizeof(counter) + SHA256_DIGEST_LENGTH];
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uint8_t sig[crypto_sign_ed25519_BYTES + sizeof(signbuf)];
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unsigned long long smlen;
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if (key_handle_len != crypto_sign_ed25519_SECRETKEYBYTES) {
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skdebug(__func__, "bad key handle length %zu", key_handle_len);
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goto out;
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}
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/* Expect message to be pre-hashed */
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if (message_len != SHA256_DIGEST_LENGTH) {
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skdebug(__func__, "bad message len %zu", message_len);
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goto out;
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}
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/* Prepare data to be signed */
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dump("message", message, message_len);
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SHA256_Init(&ctx);
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SHA256_Update(&ctx, application, strlen(application));
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SHA256_Final(apphash, &ctx);
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dump("apphash", apphash, sizeof(apphash));
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memcpy(signbuf, apphash, sizeof(apphash));
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o = sizeof(apphash);
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signbuf[o++] = flags;
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signbuf[o++] = (counter >> 24) & 0xff;
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signbuf[o++] = (counter >> 16) & 0xff;
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signbuf[o++] = (counter >> 8) & 0xff;
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signbuf[o++] = counter & 0xff;
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memcpy(signbuf + o, message, message_len);
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o += message_len;
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if (o != sizeof(signbuf)) {
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skdebug(__func__, "bad sign buf len %zu, expected %zu",
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o, sizeof(signbuf));
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goto out;
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}
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dump("signbuf", signbuf, sizeof(signbuf));
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/* create and encode signature */
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smlen = sizeof(signbuf);
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if (crypto_sign_ed25519(sig, &smlen, signbuf, sizeof(signbuf),
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key_handle) != 0) {
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skdebug(__func__, "crypto_sign_ed25519 failed");
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goto out;
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}
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if (smlen <= sizeof(signbuf)) {
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skdebug(__func__, "bad sign smlen %llu, expected min %zu",
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smlen, sizeof(signbuf) + 1);
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goto out;
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}
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response->sig_r_len = (size_t)(smlen - sizeof(signbuf));
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if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL) {
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skdebug(__func__, "calloc signature failed");
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goto out;
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}
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memcpy(response->sig_r, sig, response->sig_r_len);
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dump("sig_r", response->sig_r, response->sig_r_len);
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ret = 0;
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out:
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explicit_bzero(&ctx, sizeof(ctx));
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explicit_bzero(&apphash, sizeof(apphash));
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explicit_bzero(&signbuf, sizeof(signbuf));
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explicit_bzero(&sig, sizeof(sig));
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if (ret != 0) {
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free(response->sig_r);
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response->sig_r = NULL;
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}
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return ret;
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}
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|
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int
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sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
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const char *application, const uint8_t *key_handle, size_t key_handle_len,
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uint8_t flags, const char *pin, struct sk_option **options,
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struct sk_sign_response **sign_response)
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{
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struct sk_sign_response *response = NULL;
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int ret = SSH_SK_ERR_GENERAL;
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SHA256_CTX ctx;
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uint8_t message[32];
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|
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if (sign_response == NULL) {
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skdebug(__func__, "sign_response == NULL");
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goto out;
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}
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*sign_response = NULL;
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if (check_options(options) != 0)
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|
goto out; /* error already logged */
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|
if ((response = calloc(1, sizeof(*response))) == NULL) {
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|
skdebug(__func__, "calloc response failed");
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goto out;
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}
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SHA256_Init(&ctx);
|
|
SHA256_Update(&ctx, data, datalen);
|
|
SHA256_Final(message, &ctx);
|
|
response->flags = flags;
|
|
response->counter = 0x12345678;
|
|
switch(alg) {
|
|
case SSH_SK_ECDSA:
|
|
if (sig_ecdsa(message, sizeof(message), application,
|
|
response->counter, flags, key_handle, key_handle_len,
|
|
response) != 0)
|
|
goto out;
|
|
break;
|
|
case SSH_SK_ED25519:
|
|
if (sig_ed25519(message, sizeof(message), application,
|
|
response->counter, flags, key_handle, key_handle_len,
|
|
response) != 0)
|
|
goto out;
|
|
break;
|
|
default:
|
|
skdebug(__func__, "unsupported key type %d", alg);
|
|
return -1;
|
|
}
|
|
*sign_response = response;
|
|
response = NULL;
|
|
ret = 0;
|
|
out:
|
|
explicit_bzero(message, sizeof(message));
|
|
if (response != NULL) {
|
|
free(response->sig_r);
|
|
free(response->sig_s);
|
|
free(response);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int
|
|
sk_load_resident_keys(const char *pin, struct sk_option **options,
|
|
struct sk_resident_key ***rks, size_t *nrks)
|
|
{
|
|
return SSH_SK_ERR_UNSUPPORTED;
|
|
}
|