ssh-xmss.c - third_party/openssh-portable - Git at Google

 /* $OpenBSD: ssh-xmss.c,v 1.14 2022/10/28 00:44:44 djm Exp $*/
 /*
  * Copyright (c) 2017 Stefan-Lukas Gazdag.
  * Copyright (c) 2017 Markus Friedl.
  *
  * 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 WITH_XMSS

 #define SSHKEY_INTERNAL
 #include <sys/types.h>
 #include <limits.h>

 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
 #ifdef HAVE_STDINT_H
 # include <stdint.h>
 #endif
 #include <unistd.h>

 #include "log.h"
 #include "sshbuf.h"
 #include "sshkey.h"
 #include "sshkey-xmss.h"
 #include "ssherr.h"
 #include "ssh.h"

 #include "xmss_fast.h"

 static void
 ssh_xmss_cleanup(struct sshkey *k)
 {
 	freezero(k->xmss_pk, sshkey_xmss_pklen(k));
 	freezero(k->xmss_sk, sshkey_xmss_sklen(k));
 	sshkey_xmss_free_state(k);
 	free(k->xmss_name);
 	free(k->xmss_filename);
 	k->xmss_pk = NULL;
 	k->xmss_sk = NULL;
 	k->xmss_name = NULL;
 	k->xmss_filename = NULL;
 }

 static int
 ssh_xmss_equal(const struct sshkey *a, const struct sshkey *b)
 {
 	if (a->xmss_pk == NULL || b->xmss_pk == NULL)
 		return 0;
 	if (sshkey_xmss_pklen(a) != sshkey_xmss_pklen(b))
 		return 0;
 	if (memcmp(a->xmss_pk, b->xmss_pk, sshkey_xmss_pklen(a)) != 0)
 		return 0;
 	return 1;
 }

 static int
 ssh_xmss_serialize_public(const struct sshkey *key, struct sshbuf *b,
     enum sshkey_serialize_rep opts)
 {
 	int r;

 	if (key->xmss_name == NULL || key->xmss_pk == NULL ||
 	    sshkey_xmss_pklen(key) == 0)
 		return SSH_ERR_INVALID_ARGUMENT;
 	if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
 	    (r = sshbuf_put_string(b, key->xmss_pk,
 	    sshkey_xmss_pklen(key))) != 0 ||
 	    (r = sshkey_xmss_serialize_pk_info(key, b, opts)) != 0)
 		return r;

 	return 0;
 }

 static int
 ssh_xmss_serialize_private(const struct sshkey *key, struct sshbuf *b,
     enum sshkey_serialize_rep opts)
 {
 	int r;

 	if (key->xmss_name == NULL)
 		return SSH_ERR_INVALID_ARGUMENT;
 	/* Note: can't reuse ssh_xmss_serialize_public because of sk order */
 	if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
 	    (r = sshbuf_put_string(b, key->xmss_pk,
 	    sshkey_xmss_pklen(key))) != 0 ||
 	    (r = sshbuf_put_string(b, key->xmss_sk,
 	    sshkey_xmss_sklen(key))) != 0 ||
 	    (r = sshkey_xmss_serialize_state_opt(key, b, opts)) != 0)
 		return r;

 	return 0;
 }

 static int
 ssh_xmss_copy_public(const struct sshkey *from, struct sshkey *to)
 {
 	int r = SSH_ERR_INTERNAL_ERROR;
 	u_int32_t left;
 	size_t pklen;

 	if ((r = sshkey_xmss_init(to, from->xmss_name)) != 0)
 		return r;
 	if (from->xmss_pk == NULL)
 		return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */

 	if ((pklen = sshkey_xmss_pklen(from)) == 0 ||
 	    sshkey_xmss_pklen(to) != pklen)
 		return SSH_ERR_INTERNAL_ERROR;
 	if ((to->xmss_pk = malloc(pklen)) == NULL)
 		return SSH_ERR_ALLOC_FAIL;
 	memcpy(to->xmss_pk, from->xmss_pk, pklen);
 	/* simulate number of signatures left on pubkey */
 	left = sshkey_xmss_signatures_left(from);
 	if (left)
 		sshkey_xmss_enable_maxsign(to, left);
 	return 0;
 }

 static int
 ssh_xmss_deserialize_public(const char *ktype, struct sshbuf *b,
     struct sshkey *key)
 {
 	size_t len = 0;
 	char *xmss_name = NULL;
 	u_char *pk = NULL;
 	int ret = SSH_ERR_INTERNAL_ERROR;

 	if ((ret = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0)
 		goto out;
 	if ((ret = sshkey_xmss_init(key, xmss_name)) != 0)
 		goto out;
 	if ((ret = sshbuf_get_string(b, &pk, &len)) != 0)
 		goto out;
 	if (len == 0 || len != sshkey_xmss_pklen(key)) {
 		ret = SSH_ERR_INVALID_FORMAT;
 		goto out;
 	}
 	key->xmss_pk = pk;
 	pk = NULL;
 	if (!sshkey_is_cert(key) &&
 	    (ret = sshkey_xmss_deserialize_pk_info(key, b)) != 0)
 		goto out;
 	/* success */
 	ret = 0;
  out:
 	free(xmss_name);
 	freezero(pk, len);
 	return ret;
 }

 static int
 ssh_xmss_deserialize_private(const char *ktype, struct sshbuf *b,
     struct sshkey *key)
 {
 	int r;
 	char *xmss_name = NULL;
 	size_t pklen = 0, sklen = 0;
 	u_char *xmss_pk = NULL, *xmss_sk = NULL;

 	/* Note: can't reuse ssh_xmss_deserialize_public because of sk order */
 	if ((r = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0 ||
 	    (r = sshbuf_get_string(b, &xmss_pk, &pklen)) != 0 ||
 	    (r = sshbuf_get_string(b, &xmss_sk, &sklen)) != 0)
 		goto out;
 	if (!sshkey_is_cert(key) &&
 	    (r = sshkey_xmss_init(key, xmss_name)) != 0)
 		goto out;
 	if (pklen != sshkey_xmss_pklen(key) ||
 	    sklen != sshkey_xmss_sklen(key)) {
 		r = SSH_ERR_INVALID_FORMAT;
 		goto out;
 	}
 	key->xmss_pk = xmss_pk;
 	key->xmss_sk = xmss_sk;
 	xmss_pk = xmss_sk = NULL;
 	/* optional internal state */
 	if ((r = sshkey_xmss_deserialize_state_opt(key, b)) != 0)
 		goto out;
 	/* success */
 	r = 0;
  out:
 	free(xmss_name);
 	freezero(xmss_pk, pklen);
 	freezero(xmss_sk, sklen);
 	return r;
 }

 static int
 ssh_xmss_sign(struct sshkey *key,
     u_char **sigp, size_t *lenp,
     const u_char *data, size_t datalen,
     const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
 {
 	u_char *sig = NULL;
 	size_t slen = 0, len = 0, required_siglen;
 	unsigned long long smlen;
 	int r, ret;
 	struct sshbuf *b = NULL;

 	if (lenp != NULL)
 		*lenp = 0;
 	if (sigp != NULL)
 		*sigp = NULL;

 	if (key == NULL ||
 	    sshkey_type_plain(key->type) != KEY_XMSS ||
 	    key->xmss_sk == NULL ||
 	    sshkey_xmss_params(key) == NULL)
 		return SSH_ERR_INVALID_ARGUMENT;
 	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
 		return r;
 	if (datalen >= INT_MAX - required_siglen)
 		return SSH_ERR_INVALID_ARGUMENT;
 	smlen = slen = datalen + required_siglen;
 	if ((sig = malloc(slen)) == NULL)
 		return SSH_ERR_ALLOC_FAIL;
 	if ((r = sshkey_xmss_get_state(key, 1)) != 0)
 		goto out;
 	if ((ret = xmss_sign(key->xmss_sk, sshkey_xmss_bds_state(key), sig, &smlen,
 	    data, datalen, sshkey_xmss_params(key))) != 0 || smlen <= datalen) {
 		r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
 		goto out;
 	}
 	/* encode signature */
 	if ((b = sshbuf_new()) == NULL) {
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
 	}
 	if ((r = sshbuf_put_cstring(b, "ssh-xmss@openssh.com")) != 0 ||
 	    (r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
 		goto out;
 	len = sshbuf_len(b);
 	if (sigp != NULL) {
 		if ((*sigp = malloc(len)) == NULL) {
 			r = SSH_ERR_ALLOC_FAIL;
 			goto out;
 		}
 		memcpy(*sigp, sshbuf_ptr(b), len);
 	}
 	if (lenp != NULL)
 		*lenp = len;
 	/* success */
 	r = 0;
  out:
 	if ((ret = sshkey_xmss_update_state(key, 1)) != 0) {
 		/* discard signature since we cannot update the state */
 		if (r == 0 && sigp != NULL && *sigp != NULL) {
 			explicit_bzero(*sigp, len);
 			free(*sigp);
 		}
 		if (sigp != NULL)
 			*sigp = NULL;
 		if (lenp != NULL)
 			*lenp = 0;
 		r = ret;
 	}
 	sshbuf_free(b);
 	if (sig != NULL)
 		freezero(sig, slen);

 	return r;
 }

 static int
 ssh_xmss_verify(const struct sshkey *key,
     const u_char *sig, size_t siglen,
     const u_char *data, size_t dlen, const char *alg, u_int compat,
     struct sshkey_sig_details **detailsp)
 {
 	struct sshbuf *b = NULL;
 	char *ktype = NULL;
 	const u_char *sigblob;
 	u_char *sm = NULL, *m = NULL;
 	size_t len, required_siglen;
 	unsigned long long smlen = 0, mlen = 0;
 	int r, ret;

 	if (key == NULL ||
 	    sshkey_type_plain(key->type) != KEY_XMSS ||
 	    key->xmss_pk == NULL ||
 	    sshkey_xmss_params(key) == NULL ||
 	    sig == NULL || siglen == 0)
 		return SSH_ERR_INVALID_ARGUMENT;
 	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
 		return r;
 	if (dlen >= INT_MAX - required_siglen)
 		return SSH_ERR_INVALID_ARGUMENT;

 	if ((b = sshbuf_from(sig, siglen)) == NULL)
 		return SSH_ERR_ALLOC_FAIL;
 	if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
 	    (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
 		goto out;
 	if (strcmp("ssh-xmss@openssh.com", ktype) != 0) {
 		r = SSH_ERR_KEY_TYPE_MISMATCH;
 		goto out;
 	}
 	if (sshbuf_len(b) != 0) {
 		r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
 		goto out;
 	}
 	if (len != required_siglen) {
 		r = SSH_ERR_INVALID_FORMAT;
 		goto out;
 	}
 	if (dlen >= SIZE_MAX - len) {
 		r = SSH_ERR_INVALID_ARGUMENT;
 		goto out;
 	}
 	smlen = len + dlen;
 	mlen = smlen;
 	if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
 	}
 	memcpy(sm, sigblob, len);
 	memcpy(sm+len, data, dlen);
 	if ((ret = xmss_sign_open(m, &mlen, sm, smlen,
 	    key->xmss_pk, sshkey_xmss_params(key))) != 0) {
 		debug2_f("xmss_sign_open failed: %d", ret);
 	}
 	if (ret != 0 || mlen != dlen) {
 		r = SSH_ERR_SIGNATURE_INVALID;
 		goto out;
 	}
 	/* XXX compare 'm' and 'data' ? */
 	/* success */
 	r = 0;
  out:
 	if (sm != NULL)
 		freezero(sm, smlen);
 	if (m != NULL)
 		freezero(m, smlen);
 	sshbuf_free(b);
 	free(ktype);
 	return r;
 }

 static const struct sshkey_impl_funcs sshkey_xmss_funcs = {
 	/* .size = */		NULL,
 	/* .alloc = */		NULL,
 	/* .cleanup = */	ssh_xmss_cleanup,
 	/* .equal = */		ssh_xmss_equal,
 	/* .ssh_serialize_public = */ ssh_xmss_serialize_public,
 	/* .ssh_deserialize_public = */ ssh_xmss_deserialize_public,
 	/* .ssh_serialize_private = */ ssh_xmss_serialize_private,
 	/* .ssh_deserialize_private = */ ssh_xmss_deserialize_private,
 	/* .generate = */	sshkey_xmss_generate_private_key,
 	/* .copy_public = */	ssh_xmss_copy_public,
 	/* .sign = */		ssh_xmss_sign,
 	/* .verify = */		ssh_xmss_verify,
 };

 const struct sshkey_impl sshkey_xmss_impl = {
 	/* .name = */		"ssh-xmss@openssh.com",
 	/* .shortname = */	"XMSS",
 	/* .sigalg = */		NULL,
 	/* .type = */		KEY_XMSS,
 	/* .nid = */		0,
 	/* .cert = */		0,
 	/* .sigonly = */	0,
 	/* .keybits = */	256,
 	/* .funcs = */		&sshkey_xmss_funcs,
 };

 const struct sshkey_impl sshkey_xmss_cert_impl = {
 	/* .name = */		"ssh-xmss-cert-v01@openssh.com",
 	/* .shortname = */	"XMSS-CERT",
 	/* .sigalg = */		NULL,
 	/* .type = */		KEY_XMSS_CERT,
 	/* .nid = */		0,
 	/* .cert = */		1,
 	/* .sigonly = */	0,
 	/* .keybits = */	256,
 	/* .funcs = */		&sshkey_xmss_funcs,
 };
 #endif /* WITH_XMSS */
	/* $OpenBSD: ssh-xmss.c,v 1.14 2022/10/28 00:44:44 djm Exp $*/
	/*
	* Copyright (c) 2017 Stefan-Lukas Gazdag.
	* Copyright (c) 2017 Markus Friedl.
	*
	* 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 WITH_XMSS

	#define SSHKEY_INTERNAL
	#include <sys/types.h>
	#include <limits.h>

	#include <stdlib.h>
	#include <string.h>
	#include <stdarg.h>
	#ifdef HAVE_STDINT_H
	# include <stdint.h>
	#endif
	#include <unistd.h>

	#include "log.h"
	#include "sshbuf.h"
	#include "sshkey.h"
	#include "sshkey-xmss.h"
	#include "ssherr.h"
	#include "ssh.h"

	#include "xmss_fast.h"

	static void
	ssh_xmss_cleanup(struct sshkey *k)
	{
	freezero(k->xmss_pk, sshkey_xmss_pklen(k));
	freezero(k->xmss_sk, sshkey_xmss_sklen(k));
	sshkey_xmss_free_state(k);
	free(k->xmss_name);
	free(k->xmss_filename);
	k->xmss_pk = NULL;
	k->xmss_sk = NULL;
	k->xmss_name = NULL;
	k->xmss_filename = NULL;
	}

	static int
	ssh_xmss_equal(const struct sshkey a, const struct sshkey b)
	{
	if (a->xmss_pk == NULL \|\| b->xmss_pk == NULL)
	return 0;
	if (sshkey_xmss_pklen(a) != sshkey_xmss_pklen(b))
	return 0;
	if (memcmp(a->xmss_pk, b->xmss_pk, sshkey_xmss_pklen(a)) != 0)
	return 0;
	return 1;
	}

	static int
	ssh_xmss_serialize_public(const struct sshkey key, struct sshbuf b,
	enum sshkey_serialize_rep opts)
	{
	int r;

	if (key->xmss_name == NULL \|\| key->xmss_pk == NULL \|\|
	sshkey_xmss_pklen(key) == 0)
	return SSH_ERR_INVALID_ARGUMENT;
	if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 \|\|
	(r = sshbuf_put_string(b, key->xmss_pk,
	sshkey_xmss_pklen(key))) != 0 \|\|
	(r = sshkey_xmss_serialize_pk_info(key, b, opts)) != 0)
	return r;

	return 0;
	}

	static int
	ssh_xmss_serialize_private(const struct sshkey key, struct sshbuf b,
	enum sshkey_serialize_rep opts)
	{
	int r;

	if (key->xmss_name == NULL)
	return SSH_ERR_INVALID_ARGUMENT;
	/* Note: can't reuse ssh_xmss_serialize_public because of sk order */
	if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 \|\|
	(r = sshbuf_put_string(b, key->xmss_pk,
	sshkey_xmss_pklen(key))) != 0 \|\|
	(r = sshbuf_put_string(b, key->xmss_sk,
	sshkey_xmss_sklen(key))) != 0 \|\|
	(r = sshkey_xmss_serialize_state_opt(key, b, opts)) != 0)
	return r;

	return 0;
	}

	static int
	ssh_xmss_copy_public(const struct sshkey from, struct sshkey to)
	{
	int r = SSH_ERR_INTERNAL_ERROR;
	u_int32_t left;
	size_t pklen;

	if ((r = sshkey_xmss_init(to, from->xmss_name)) != 0)
	return r;
	if (from->xmss_pk == NULL)
	return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */

	if ((pklen = sshkey_xmss_pklen(from)) == 0 \|\|
	sshkey_xmss_pklen(to) != pklen)
	return SSH_ERR_INTERNAL_ERROR;
	if ((to->xmss_pk = malloc(pklen)) == NULL)
	return SSH_ERR_ALLOC_FAIL;
	memcpy(to->xmss_pk, from->xmss_pk, pklen);
	/* simulate number of signatures left on pubkey */
	left = sshkey_xmss_signatures_left(from);
	if (left)
	sshkey_xmss_enable_maxsign(to, left);
	return 0;
	}

	static int
	ssh_xmss_deserialize_public(const char ktype, struct sshbuf b,
	struct sshkey *key)
	{
	size_t len = 0;
	char *xmss_name = NULL;
	u_char *pk = NULL;
	int ret = SSH_ERR_INTERNAL_ERROR;

	if ((ret = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0)
	goto out;
	if ((ret = sshkey_xmss_init(key, xmss_name)) != 0)
	goto out;
	if ((ret = sshbuf_get_string(b, &pk, &len)) != 0)
	goto out;
	if (len == 0 \|\| len != sshkey_xmss_pklen(key)) {
	ret = SSH_ERR_INVALID_FORMAT;
	goto out;
	}
	key->xmss_pk = pk;
	pk = NULL;
	if (!sshkey_is_cert(key) &&
	(ret = sshkey_xmss_deserialize_pk_info(key, b)) != 0)
	goto out;
	/* success */
	ret = 0;
	out:
	free(xmss_name);
	freezero(pk, len);
	return ret;
	}

	static int
	ssh_xmss_deserialize_private(const char ktype, struct sshbuf b,
	struct sshkey *key)
	{
	int r;
	char *xmss_name = NULL;
	size_t pklen = 0, sklen = 0;
	u_char xmss_pk = NULL, xmss_sk = NULL;

	/* Note: can't reuse ssh_xmss_deserialize_public because of sk order */
	if ((r = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0 \|\|
	(r = sshbuf_get_string(b, &xmss_pk, &pklen)) != 0 \|\|
	(r = sshbuf_get_string(b, &xmss_sk, &sklen)) != 0)
	goto out;
	if (!sshkey_is_cert(key) &&
	(r = sshkey_xmss_init(key, xmss_name)) != 0)
	goto out;
	if (pklen != sshkey_xmss_pklen(key) \|\|
	sklen != sshkey_xmss_sklen(key)) {
	r = SSH_ERR_INVALID_FORMAT;
	goto out;
	}
	key->xmss_pk = xmss_pk;
	key->xmss_sk = xmss_sk;
	xmss_pk = xmss_sk = NULL;
	/* optional internal state */
	if ((r = sshkey_xmss_deserialize_state_opt(key, b)) != 0)
	goto out;
	/* success */
	r = 0;
	out:
	free(xmss_name);
	freezero(xmss_pk, pklen);
	freezero(xmss_sk, sklen);
	return r;
	}

	static int
	ssh_xmss_sign(struct sshkey *key,
	u_char *sigp, size_t lenp,
	const u_char *data, size_t datalen,
	const char alg, const char sk_provider, const char *sk_pin, u_int compat)
	{
	u_char *sig = NULL;
	size_t slen = 0, len = 0, required_siglen;
	unsigned long long smlen;
	int r, ret;
	struct sshbuf *b = NULL;

	if (lenp != NULL)
	*lenp = 0;
	if (sigp != NULL)
	*sigp = NULL;

	if (key == NULL \|\|
	sshkey_type_plain(key->type) != KEY_XMSS \|\|
	key->xmss_sk == NULL \|\|
	sshkey_xmss_params(key) == NULL)
	return SSH_ERR_INVALID_ARGUMENT;
	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
	return r;
	if (datalen >= INT_MAX - required_siglen)
	return SSH_ERR_INVALID_ARGUMENT;
	smlen = slen = datalen + required_siglen;
	if ((sig = malloc(slen)) == NULL)
	return SSH_ERR_ALLOC_FAIL;
	if ((r = sshkey_xmss_get_state(key, 1)) != 0)
	goto out;
	if ((ret = xmss_sign(key->xmss_sk, sshkey_xmss_bds_state(key), sig, &smlen,
	data, datalen, sshkey_xmss_params(key))) != 0 \|\| smlen <= datalen) {
	r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
	goto out;
	}
	/* encode signature */
	if ((b = sshbuf_new()) == NULL) {
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	if ((r = sshbuf_put_cstring(b, "ssh-xmss@openssh.com")) != 0 \|\|
	(r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
	goto out;
	len = sshbuf_len(b);
	if (sigp != NULL) {
	if ((*sigp = malloc(len)) == NULL) {
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	memcpy(*sigp, sshbuf_ptr(b), len);
	}
	if (lenp != NULL)
	*lenp = len;
	/* success */
	r = 0;
	out:
	if ((ret = sshkey_xmss_update_state(key, 1)) != 0) {
	/* discard signature since we cannot update the state */
	if (r == 0 && sigp != NULL && *sigp != NULL) {
	explicit_bzero(*sigp, len);
	free(*sigp);
	}
	if (sigp != NULL)
	*sigp = NULL;
	if (lenp != NULL)
	*lenp = 0;
	r = ret;
	}
	sshbuf_free(b);
	if (sig != NULL)
	freezero(sig, slen);

	return r;
	}

	static int
	ssh_xmss_verify(const struct sshkey *key,
	const u_char *sig, size_t siglen,
	const u_char data, size_t dlen, const char alg, u_int compat,
	struct sshkey_sig_details **detailsp)
	{
	struct sshbuf *b = NULL;
	char *ktype = NULL;
	const u_char *sigblob;
	u_char sm = NULL, m = NULL;
	size_t len, required_siglen;
	unsigned long long smlen = 0, mlen = 0;
	int r, ret;

	if (key == NULL \|\|
	sshkey_type_plain(key->type) != KEY_XMSS \|\|
	key->xmss_pk == NULL \|\|
	sshkey_xmss_params(key) == NULL \|\|
	sig == NULL \|\| siglen == 0)
	return SSH_ERR_INVALID_ARGUMENT;
	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
	return r;
	if (dlen >= INT_MAX - required_siglen)
	return SSH_ERR_INVALID_ARGUMENT;

	if ((b = sshbuf_from(sig, siglen)) == NULL)
	return SSH_ERR_ALLOC_FAIL;
	if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 \|\|
	(r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
	goto out;
	if (strcmp("ssh-xmss@openssh.com", ktype) != 0) {
	r = SSH_ERR_KEY_TYPE_MISMATCH;
	goto out;
	}
	if (sshbuf_len(b) != 0) {
	r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
	goto out;
	}
	if (len != required_siglen) {
	r = SSH_ERR_INVALID_FORMAT;
	goto out;
	}
	if (dlen >= SIZE_MAX - len) {
	r = SSH_ERR_INVALID_ARGUMENT;
	goto out;
	}
	smlen = len + dlen;
	mlen = smlen;
	if ((sm = malloc(smlen)) == NULL \|\| (m = malloc(mlen)) == NULL) {
	r = SSH_ERR_ALLOC_FAIL;
	goto out;
	}
	memcpy(sm, sigblob, len);
	memcpy(sm+len, data, dlen);
	if ((ret = xmss_sign_open(m, &mlen, sm, smlen,
	key->xmss_pk, sshkey_xmss_params(key))) != 0) {
	debug2_f("xmss_sign_open failed: %d", ret);
	}
	if (ret != 0 \|\| mlen != dlen) {
	r = SSH_ERR_SIGNATURE_INVALID;
	goto out;
	}
	/* XXX compare 'm' and 'data' ? */
	/* success */
	r = 0;
	out:
	if (sm != NULL)
	freezero(sm, smlen);
	if (m != NULL)
	freezero(m, smlen);
	sshbuf_free(b);
	free(ktype);
	return r;
	}

	static const struct sshkey_impl_funcs sshkey_xmss_funcs = {
	/* .size = */ NULL,
	/* .alloc = */ NULL,
	/* .cleanup = */ ssh_xmss_cleanup,
	/* .equal = */ ssh_xmss_equal,
	/* .ssh_serialize_public = */ ssh_xmss_serialize_public,
	/* .ssh_deserialize_public = */ ssh_xmss_deserialize_public,
	/* .ssh_serialize_private = */ ssh_xmss_serialize_private,
	/* .ssh_deserialize_private = */ ssh_xmss_deserialize_private,
	/* .generate = */ sshkey_xmss_generate_private_key,
	/* .copy_public = */ ssh_xmss_copy_public,
	/* .sign = */ ssh_xmss_sign,
	/* .verify = */ ssh_xmss_verify,
	};

	const struct sshkey_impl sshkey_xmss_impl = {
	/* .name = */ "ssh-xmss@openssh.com",
	/* .shortname = */ "XMSS",
	/* .sigalg = */ NULL,
	/* .type = */ KEY_XMSS,
	/* .nid = */ 0,
	/* .cert = */ 0,
	/* .sigonly = */ 0,
	/* .keybits = */ 256,
	/* .funcs = */ &sshkey_xmss_funcs,
	};

	const struct sshkey_impl sshkey_xmss_cert_impl = {
	/* .name = */ "ssh-xmss-cert-v01@openssh.com",
	/* .shortname = */ "XMSS-CERT",
	/* .sigalg = */ NULL,
	/* .type = */ KEY_XMSS_CERT,
	/* .nid = */ 0,
	/* .cert = */ 1,
	/* .sigonly = */ 0,
	/* .keybits = */ 256,
	/* .funcs = */ &sshkey_xmss_funcs,
	};
	#endif /* WITH_XMSS */