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b556cc3cbf
OpenBSD-Commit-ID: 7672d9d0278b4bf656a12d3aab0c0bfe92a8ae47
531 lines
14 KiB
C
531 lines
14 KiB
C
/* $OpenBSD: ssh-sk.c,v 1.9 2019/11/12 19:34:40 markus Exp $ */
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/*
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* Copyright (c) 2019 Google LLC
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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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/* #define DEBUG_SK 1 */
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#include "includes.h"
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#ifdef ENABLE_SK
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#include <dlfcn.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdio.h>
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#include <openssl/objects.h>
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#include <openssl/ec.h>
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#include "log.h"
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#include "misc.h"
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#include "sshbuf.h"
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#include "sshkey.h"
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#include "ssherr.h"
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#include "digest.h"
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#include "ssh-sk.h"
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#include "sk-api.h"
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#include "crypto_api.h"
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struct sshsk_provider {
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char *path;
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void *dlhandle;
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/* Return the version of the middleware API */
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uint32_t (*sk_api_version)(void);
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/* Enroll a U2F key (private key generation) */
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int (*sk_enroll)(int alg, const uint8_t *challenge,
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size_t challenge_len, const char *application, uint8_t flags,
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struct sk_enroll_response **enroll_response);
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/* Sign a challenge */
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int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
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const char *application,
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const uint8_t *key_handle, size_t key_handle_len,
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uint8_t flags, struct sk_sign_response **sign_response);
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};
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static void
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sshsk_free(struct sshsk_provider *p)
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{
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if (p == NULL)
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return;
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free(p->path);
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if (p->dlhandle != NULL)
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dlclose(p->dlhandle);
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free(p);
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}
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static struct sshsk_provider *
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sshsk_open(const char *path)
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{
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struct sshsk_provider *ret = NULL;
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uint32_t version;
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if ((ret = calloc(1, sizeof(*ret))) == NULL) {
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error("%s: calloc failed", __func__);
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return NULL;
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}
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if ((ret->path = strdup(path)) == NULL) {
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error("%s: strdup failed", __func__);
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goto fail;
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}
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if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL) {
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error("Security key provider %s dlopen failed: %s",
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path, dlerror());
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goto fail;
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}
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if ((ret->sk_api_version = dlsym(ret->dlhandle,
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"sk_api_version")) == NULL) {
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error("Security key provider %s dlsym(sk_api_version) "
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"failed: %s", path, dlerror());
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goto fail;
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}
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version = ret->sk_api_version();
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debug("%s: provider %s implements version 0x%08lx", __func__,
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ret->path, (u_long)version);
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if ((version & SSH_SK_VERSION_MAJOR_MASK) != SSH_SK_VERSION_MAJOR) {
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error("Security key provider %s implements unsupported version "
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"0x%08lx (supported: 0x%08lx)", path, (u_long)version,
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(u_long)SSH_SK_VERSION_MAJOR);
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goto fail;
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}
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if ((ret->sk_enroll = dlsym(ret->dlhandle, "sk_enroll")) == NULL) {
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error("Security key provider %s dlsym(sk_enroll) "
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"failed: %s", path, dlerror());
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goto fail;
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}
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if ((ret->sk_sign = dlsym(ret->dlhandle, "sk_sign")) == NULL) {
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error("Security key provider %s dlsym(sk_sign) failed: %s",
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path, dlerror());
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goto fail;
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}
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/* success */
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return ret;
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fail:
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sshsk_free(ret);
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return NULL;
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}
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static void
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sshsk_free_enroll_response(struct sk_enroll_response *r)
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{
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if (r == NULL)
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return;
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freezero(r->key_handle, r->key_handle_len);
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freezero(r->public_key, r->public_key_len);
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freezero(r->signature, r->signature_len);
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freezero(r->attestation_cert, r->attestation_cert_len);
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freezero(r, sizeof(*r));
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};
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static void
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sshsk_free_sign_response(struct sk_sign_response *r)
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{
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if (r == NULL)
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return;
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freezero(r->sig_r, r->sig_r_len);
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freezero(r->sig_s, r->sig_s_len);
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freezero(r, sizeof(*r));
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};
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/* Assemble key from response */
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static int
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sshsk_ecdsa_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
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{
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struct sshkey *key = NULL;
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struct sshbuf *b = NULL;
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EC_POINT *q = NULL;
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int r;
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*keyp = NULL;
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if ((key = sshkey_new(KEY_ECDSA_SK)) == NULL) {
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error("%s: sshkey_new failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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key->ecdsa_nid = NID_X9_62_prime256v1;
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if ((key->ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
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(q = EC_POINT_new(EC_KEY_get0_group(key->ecdsa))) == NULL ||
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(b = sshbuf_new()) == NULL) {
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error("%s: allocation failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshbuf_put_string(b,
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resp->public_key, resp->public_key_len)) != 0) {
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error("%s: buffer error: %s", __func__, ssh_err(r));
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goto out;
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}
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if ((r = sshbuf_get_ec(b, q, EC_KEY_get0_group(key->ecdsa))) != 0) {
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error("%s: parse key: %s", __func__, ssh_err(r));
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (sshkey_ec_validate_public(EC_KEY_get0_group(key->ecdsa), q) != 0) {
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error("Security key returned invalid ECDSA key");
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r = SSH_ERR_KEY_INVALID_EC_VALUE;
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goto out;
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}
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if (EC_KEY_set_public_key(key->ecdsa, q) != 1) {
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/* XXX assume it is a allocation error */
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error("%s: allocation failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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/* success */
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*keyp = key;
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key = NULL; /* transferred */
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r = 0;
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out:
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EC_POINT_free(q);
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sshkey_free(key);
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sshbuf_free(b);
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return r;
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}
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static int
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sshsk_ed25519_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
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{
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struct sshkey *key = NULL;
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int r;
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*keyp = NULL;
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if (resp->public_key_len != ED25519_PK_SZ) {
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error("%s: invalid size: %zu", __func__, resp->public_key_len);
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if ((key = sshkey_new(KEY_ED25519_SK)) == NULL) {
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error("%s: sshkey_new failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((key->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL) {
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error("%s: malloc failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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memcpy(key->ed25519_pk, resp->public_key, ED25519_PK_SZ);
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/* success */
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*keyp = key;
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key = NULL; /* transferred */
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r = 0;
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out:
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sshkey_free(key);
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return r;
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}
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int
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sshsk_enroll(int type, const char *provider_path, const char *application,
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uint8_t flags, struct sshbuf *challenge_buf, struct sshkey **keyp,
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struct sshbuf *attest)
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{
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struct sshsk_provider *skp = NULL;
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struct sshkey *key = NULL;
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u_char randchall[32];
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const u_char *challenge;
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size_t challenge_len;
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struct sk_enroll_response *resp = NULL;
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int r = SSH_ERR_INTERNAL_ERROR;
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int alg;
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*keyp = NULL;
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if (attest)
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sshbuf_reset(attest);
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switch (type) {
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case KEY_ECDSA_SK:
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alg = SSH_SK_ECDSA;
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break;
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case KEY_ED25519_SK:
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alg = SSH_SK_ED25519;
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break;
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default:
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error("%s: unsupported key type", __func__);
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r = SSH_ERR_INVALID_ARGUMENT;
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goto out;
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}
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if (provider_path == NULL) {
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error("%s: missing provider", __func__);
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r = SSH_ERR_INVALID_ARGUMENT;
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goto out;
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}
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if (application == NULL || *application == '\0') {
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error("%s: missing application", __func__);
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r = SSH_ERR_INVALID_ARGUMENT;
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goto out;
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}
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if (challenge_buf == NULL) {
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debug("%s: using random challenge", __func__);
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arc4random_buf(randchall, sizeof(randchall));
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challenge = randchall;
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challenge_len = sizeof(randchall);
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} else if (sshbuf_len(challenge_buf) == 0) {
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error("Missing enrollment challenge");
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r = SSH_ERR_INVALID_ARGUMENT;
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goto out;
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} else {
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challenge = sshbuf_ptr(challenge_buf);
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challenge_len = sshbuf_len(challenge_buf);
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debug3("%s: using explicit challenge len=%zd",
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__func__, challenge_len);
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}
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if ((skp = sshsk_open(provider_path)) == NULL) {
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r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
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goto out;
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}
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/* XXX validate flags? */
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/* enroll key */
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if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
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flags, &resp)) != 0) {
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error("Security key provider %s returned failure %d",
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provider_path, r);
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r = SSH_ERR_INVALID_FORMAT; /* XXX error codes in API? */
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goto out;
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}
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/* Check response validity */
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if (resp->public_key == NULL || resp->key_handle == NULL ||
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resp->signature == NULL || resp->attestation_cert == NULL) {
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error("%s: sk_enroll response invalid", __func__);
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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switch (type) {
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case KEY_ECDSA_SK:
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if ((r = sshsk_ecdsa_assemble(resp, &key)) != 0)
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goto out;
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break;
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case KEY_ED25519_SK:
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if ((r = sshsk_ed25519_assemble(resp, &key)) != 0)
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goto out;
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break;
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}
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key->sk_flags = flags;
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if ((key->sk_key_handle = sshbuf_new()) == NULL ||
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(key->sk_reserved = sshbuf_new()) == NULL) {
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error("%s: allocation failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((key->sk_application = strdup(application)) == NULL) {
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error("%s: strdup application failed", __func__);
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshbuf_put(key->sk_key_handle, resp->key_handle,
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resp->key_handle_len)) != 0) {
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error("%s: buffer error: %s", __func__, ssh_err(r));
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goto out;
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}
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/* Optionally fill in the attestation information */
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if (attest != NULL) {
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if ((r = sshbuf_put_cstring(attest, "sk-attest-v00")) != 0 ||
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(r = sshbuf_put_u32(attest, 1)) != 0 || /* XXX U2F ver */
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(r = sshbuf_put_string(attest,
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resp->attestation_cert, resp->attestation_cert_len)) != 0 ||
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(r = sshbuf_put_string(attest,
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resp->signature, resp->signature_len)) != 0 ||
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(r = sshbuf_put_u32(attest, flags)) != 0 || /* XXX right? */
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(r = sshbuf_put_string(attest, NULL, 0)) != 0) {
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error("%s: buffer error: %s", __func__, ssh_err(r));
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goto out;
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}
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}
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/* success */
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*keyp = key;
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key = NULL; /* transferred */
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r = 0;
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out:
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sshsk_free(skp);
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sshkey_free(key);
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sshsk_free_enroll_response(resp);
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explicit_bzero(randchall, sizeof(randchall));
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return r;
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}
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static int
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sshsk_ecdsa_sig(struct sk_sign_response *resp, struct sshbuf *sig)
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{
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struct sshbuf *inner_sig = NULL;
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int r = SSH_ERR_INTERNAL_ERROR;
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/* Check response validity */
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if (resp->sig_r == NULL || resp->sig_r == NULL) {
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error("%s: sk_sign response invalid", __func__);
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if ((inner_sig = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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/* Prepare and append inner signature object */
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if ((r = sshbuf_put_bignum2_bytes(inner_sig,
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resp->sig_r, resp->sig_r_len)) != 0 ||
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(r = sshbuf_put_bignum2_bytes(inner_sig,
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resp->sig_s, resp->sig_s_len)) != 0 ||
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(r = sshbuf_put_u8(inner_sig, resp->flags)) != 0 ||
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(r = sshbuf_put_u32(inner_sig, resp->counter)) != 0) {
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debug("%s: buffer error: %s", __func__, ssh_err(r));
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goto out;
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}
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if ((r = sshbuf_put_stringb(sig, inner_sig)) != 0) {
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debug("%s: buffer error: %s", __func__, ssh_err(r));
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goto out;
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}
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#ifdef DEBUG_SK
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fprintf(stderr, "%s: sig_r:\n", __func__);
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sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
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fprintf(stderr, "%s: sig_s:\n", __func__);
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sshbuf_dump_data(resp->sig_s, resp->sig_s_len, stderr);
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fprintf(stderr, "%s: inner:\n", __func__);
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sshbuf_dump(inner_sig, stderr);
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|
#endif
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r = 0;
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out:
|
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sshbuf_free(inner_sig);
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return r;
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}
|
|
|
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static int
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sshsk_ed25519_sig(struct sk_sign_response *resp, struct sshbuf *sig)
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|
{
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int r = SSH_ERR_INTERNAL_ERROR;
|
|
|
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/* Check response validity */
|
|
if (resp->sig_r == NULL) {
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error("%s: sk_sign response invalid", __func__);
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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|
}
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|
if ((r = sshbuf_put_string(sig,
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resp->sig_r, resp->sig_r_len)) != 0 ||
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(r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
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|
(r = sshbuf_put_u32(sig, resp->counter)) != 0) {
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|
debug("%s: buffer error: %s", __func__, ssh_err(r));
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|
goto out;
|
|
}
|
|
#ifdef DEBUG_SK
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|
fprintf(stderr, "%s: sig_r:\n", __func__);
|
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sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
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|
#endif
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r = 0;
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out:
|
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return 0;
|
|
}
|
|
|
|
int
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sshsk_sign(const char *provider_path, const struct sshkey *key,
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u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
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u_int compat)
|
|
{
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struct sshsk_provider *skp = NULL;
|
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int r = SSH_ERR_INTERNAL_ERROR;
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|
int type, alg;
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|
struct sk_sign_response *resp = NULL;
|
|
struct sshbuf *inner_sig = NULL, *sig = NULL;
|
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uint8_t message[32];
|
|
|
|
if (sigp != NULL)
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|
*sigp = NULL;
|
|
if (lenp != NULL)
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|
*lenp = 0;
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|
type = sshkey_type_plain(key->type);
|
|
switch (type) {
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case KEY_ECDSA_SK:
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|
alg = SSH_SK_ECDSA;
|
|
break;
|
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case KEY_ED25519_SK:
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alg = SSH_SK_ED25519;
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break;
|
|
default:
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return SSH_ERR_INVALID_ARGUMENT;
|
|
}
|
|
if (provider_path == NULL ||
|
|
key->sk_key_handle == NULL ||
|
|
key->sk_application == NULL || *key->sk_application == '\0') {
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|
r = SSH_ERR_INVALID_ARGUMENT;
|
|
goto out;
|
|
}
|
|
if ((skp = sshsk_open(provider_path)) == NULL) {
|
|
r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
|
|
goto out;
|
|
}
|
|
|
|
/* hash data to be signed before it goes to the security key */
|
|
if ((r = ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen,
|
|
message, sizeof(message))) != 0) {
|
|
error("%s: hash application failed: %s", __func__, ssh_err(r));
|
|
r = SSH_ERR_INTERNAL_ERROR;
|
|
goto out;
|
|
}
|
|
if ((r = skp->sk_sign(alg, message, sizeof(message),
|
|
key->sk_application,
|
|
sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
|
|
key->sk_flags, &resp)) != 0) {
|
|
debug("%s: sk_sign failed with code %d", __func__, r);
|
|
goto out;
|
|
}
|
|
/* Assemble signature */
|
|
if ((sig = sshbuf_new()) == NULL) {
|
|
r = SSH_ERR_ALLOC_FAIL;
|
|
goto out;
|
|
}
|
|
if ((r = sshbuf_put_cstring(sig, sshkey_ssh_name_plain(key))) != 0) {
|
|
debug("%s: buffer error (outer): %s", __func__, ssh_err(r));
|
|
goto out;
|
|
}
|
|
switch (type) {
|
|
case KEY_ECDSA_SK:
|
|
if ((r = sshsk_ecdsa_sig(resp, sig)) != 0)
|
|
goto out;
|
|
break;
|
|
case KEY_ED25519_SK:
|
|
if ((r = sshsk_ed25519_sig(resp, sig)) != 0)
|
|
goto out;
|
|
break;
|
|
}
|
|
#ifdef DEBUG_SK
|
|
fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
|
|
__func__, resp->flags, resp->counter);
|
|
fprintf(stderr, "%s: hashed message:\n", __func__);
|
|
sshbuf_dump_data(message, sizeof(message), stderr);
|
|
fprintf(stderr, "%s: sigbuf:\n", __func__);
|
|
sshbuf_dump(sig, stderr);
|
|
#endif
|
|
if (sigp != NULL) {
|
|
if ((*sigp = malloc(sshbuf_len(sig))) == NULL) {
|
|
r = SSH_ERR_ALLOC_FAIL;
|
|
goto out;
|
|
}
|
|
memcpy(*sigp, sshbuf_ptr(sig), sshbuf_len(sig));
|
|
}
|
|
if (lenp != NULL)
|
|
*lenp = sshbuf_len(sig);
|
|
/* success */
|
|
r = 0;
|
|
out:
|
|
explicit_bzero(message, sizeof(message));
|
|
sshsk_free(skp);
|
|
sshsk_free_sign_response(resp);
|
|
sshbuf_free(sig);
|
|
sshbuf_free(inner_sig);
|
|
return r;
|
|
}
|
|
#endif /* ENABLE_SK */
|