Adding upstream version 1:9.6p1.upstream/1%9.6p1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1113 insertions, 0 deletions

diff --git a/sshkey-xmss.c b/sshkey-xmss.c
new file mode 100644
index 0000000..818aba9
--- /dev/null
+++ b/sshkey-xmss.c
@@ -0,0 +1,1113 @@
+/* $OpenBSD: sshkey-xmss.c,v 1.12 2022/10/28 00:39:29 djm Exp $ */
+/*
+ * Copyright (c) 2017 Markus Friedl.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+#ifdef WITH_XMSS
+
+#include <sys/types.h>
+#include <sys/uio.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#ifdef HAVE_SYS_FILE_H
+# include <sys/file.h>
+#endif
+
+#include "ssh2.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+#include "cipher.h"
+#include "sshkey.h"
+#include "sshkey-xmss.h"
+#include "atomicio.h"
+#include "log.h"
+
+#include "xmss_fast.h"
+
+/* opaque internal XMSS state */
+#define XMSS_MAGIC		"xmss-state-v1"
+#define XMSS_CIPHERNAME		"aes256-gcm@openssh.com"
+struct ssh_xmss_state {
+	xmss_params	params;
+	u_int32_t	n, w, h, k;
+
+	bds_state	bds;
+	u_char		*stack;
+	u_int32_t	stackoffset;
+	u_char		*stacklevels;
+	u_char		*auth;
+	u_char		*keep;
+	u_char		*th_nodes;
+	u_char		*retain;
+	treehash_inst	*treehash;
+
+	u_int32_t	idx;		/* state read from file */
+	u_int32_t	maxidx;		/* restricted # of signatures */
+	int		have_state;	/* .state file exists */
+	int		lockfd;		/* locked in sshkey_xmss_get_state() */
+	u_char		allow_update;	/* allow sshkey_xmss_update_state() */
+	char		*enc_ciphername;/* encrypt state with cipher */
+	u_char		*enc_keyiv;	/* encrypt state with key */
+	u_int32_t	enc_keyiv_len;	/* length of enc_keyiv */
+};
+
+int	 sshkey_xmss_init_bds_state(struct sshkey *);
+int	 sshkey_xmss_init_enc_key(struct sshkey *, const char *);
+void	 sshkey_xmss_free_bds(struct sshkey *);
+int	 sshkey_xmss_get_state_from_file(struct sshkey *, const char *,
+	    int *, int);
+int	 sshkey_xmss_encrypt_state(const struct sshkey *, struct sshbuf *,
+	    struct sshbuf **);
+int	 sshkey_xmss_decrypt_state(const struct sshkey *, struct sshbuf *,
+	    struct sshbuf **);
+int	 sshkey_xmss_serialize_enc_key(const struct sshkey *, struct sshbuf *);
+int	 sshkey_xmss_deserialize_enc_key(struct sshkey *, struct sshbuf *);
+
+#define PRINT(...) do { if (printerror) sshlog(__FILE__, __func__, __LINE__, \
+    0, SYSLOG_LEVEL_ERROR, NULL, __VA_ARGS__); } while (0)
+
+int
+sshkey_xmss_init(struct sshkey *key, const char *name)
+{
+	struct ssh_xmss_state *state;
+
+	if (key->xmss_state != NULL)
+		return SSH_ERR_INVALID_FORMAT;
+	if (name == NULL)
+		return SSH_ERR_INVALID_FORMAT;
+	state = calloc(sizeof(struct ssh_xmss_state), 1);
+	if (state == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if (strcmp(name, XMSS_SHA2_256_W16_H10_NAME) == 0) {
+		state->n = 32;
+		state->w = 16;
+		state->h = 10;
+	} else if (strcmp(name, XMSS_SHA2_256_W16_H16_NAME) == 0) {
+		state->n = 32;
+		state->w = 16;
+		state->h = 16;
+	} else if (strcmp(name, XMSS_SHA2_256_W16_H20_NAME) == 0) {
+		state->n = 32;
+		state->w = 16;
+		state->h = 20;
+	} else {
+		free(state);
+		return SSH_ERR_KEY_TYPE_UNKNOWN;
+	}
+	if ((key->xmss_name = strdup(name)) == NULL) {
+		free(state);
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	state->k = 2;	/* XXX hardcoded */
+	state->lockfd = -1;
+	if (xmss_set_params(&state->params, state->n, state->h, state->w,
+	    state->k) != 0) {
+		free(state);
+		return SSH_ERR_INVALID_FORMAT;
+	}
+	key->xmss_state = state;
+	return 0;
+}
+
+void
+sshkey_xmss_free_state(struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	sshkey_xmss_free_bds(key);
+	if (state) {
+		if (state->enc_keyiv) {
+			explicit_bzero(state->enc_keyiv, state->enc_keyiv_len);
+			free(state->enc_keyiv);
+		}
+		free(state->enc_ciphername);
+		free(state);
+	}
+	key->xmss_state = NULL;
+}
+
+#define SSH_XMSS_K2_MAGIC	"k=2"
+#define num_stack(x)		((x->h+1)*(x->n))
+#define num_stacklevels(x)	(x->h+1)
+#define num_auth(x)		((x->h)*(x->n))
+#define num_keep(x)		((x->h >> 1)*(x->n))
+#define num_th_nodes(x)		((x->h - x->k)*(x->n))
+#define num_retain(x)		(((1ULL << x->k) - x->k - 1) * (x->n))
+#define num_treehash(x)		((x->h) - (x->k))
+
+int
+sshkey_xmss_init_bds_state(struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+	u_int32_t i;
+
+	state->stackoffset = 0;
+	if ((state->stack = calloc(num_stack(state), 1)) == NULL ||
+	    (state->stacklevels = calloc(num_stacklevels(state), 1))== NULL ||
+	    (state->auth = calloc(num_auth(state), 1)) == NULL ||
+	    (state->keep = calloc(num_keep(state), 1)) == NULL ||
+	    (state->th_nodes = calloc(num_th_nodes(state), 1)) == NULL ||
+	    (state->retain = calloc(num_retain(state), 1)) == NULL ||
+	    (state->treehash = calloc(num_treehash(state),
+	    sizeof(treehash_inst))) == NULL) {
+		sshkey_xmss_free_bds(key);
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	for (i = 0; i < state->h - state->k; i++)
+		state->treehash[i].node = &state->th_nodes[state->n*i];
+	xmss_set_bds_state(&state->bds, state->stack, state->stackoffset,
+	    state->stacklevels, state->auth, state->keep, state->treehash,
+	    state->retain, 0);
+	return 0;
+}
+
+void
+sshkey_xmss_free_bds(struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (state == NULL)
+		return;
+	free(state->stack);
+	free(state->stacklevels);
+	free(state->auth);
+	free(state->keep);
+	free(state->th_nodes);
+	free(state->retain);
+	free(state->treehash);
+	state->stack = NULL;
+	state->stacklevels = NULL;
+	state->auth = NULL;
+	state->keep = NULL;
+	state->th_nodes = NULL;
+	state->retain = NULL;
+	state->treehash = NULL;
+}
+
+void *
+sshkey_xmss_params(const struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (state == NULL)
+		return NULL;
+	return &state->params;
+}
+
+void *
+sshkey_xmss_bds_state(const struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (state == NULL)
+		return NULL;
+	return &state->bds;
+}
+
+int
+sshkey_xmss_siglen(const struct sshkey *key, size_t *lenp)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (lenp == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (state == NULL)
+		return SSH_ERR_INVALID_FORMAT;
+	*lenp = 4 + state->n +
+	    state->params.wots_par.keysize +
+	    state->h * state->n;
+	return 0;
+}
+
+size_t
+sshkey_xmss_pklen(const struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (state == NULL)
+		return 0;
+	return state->n * 2;
+}
+
+size_t
+sshkey_xmss_sklen(const struct sshkey *key)
+{
+	struct ssh_xmss_state *state = key->xmss_state;
+
+	if (state == NULL)
+		return 0;
+	return state->n * 4 + 4;
+}
+
+int
+sshkey_xmss_init_enc_key(struct sshkey *k, const char *ciphername)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	const struct sshcipher *cipher;
+	size_t keylen = 0, ivlen = 0;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((cipher = cipher_by_name(ciphername)) == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	if ((state->enc_ciphername = strdup(ciphername)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	keylen = cipher_keylen(cipher);
+	ivlen = cipher_ivlen(cipher);
+	state->enc_keyiv_len = keylen + ivlen;
+	if ((state->enc_keyiv = calloc(state->enc_keyiv_len, 1)) == NULL) {
+		free(state->enc_ciphername);
+		state->enc_ciphername = NULL;
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	arc4random_buf(state->enc_keyiv, state->enc_keyiv_len);
+	return 0;
+}
+
+int
+sshkey_xmss_serialize_enc_key(const struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	int r;
+
+	if (state == NULL || state->enc_keyiv == NULL ||
+	    state->enc_ciphername == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshbuf_put_cstring(b, state->enc_ciphername)) != 0 ||
+	    (r = sshbuf_put_string(b, state->enc_keyiv,
+	    state->enc_keyiv_len)) != 0)
+		return r;
+	return 0;
+}
+
+int
+sshkey_xmss_deserialize_enc_key(struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	size_t len;
+	int r;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshbuf_get_cstring(b, &state->enc_ciphername, NULL)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->enc_keyiv, &len)) != 0)
+		return r;
+	state->enc_keyiv_len = len;
+	return 0;
+}
+
+int
+sshkey_xmss_serialize_pk_info(const struct sshkey *k, struct sshbuf *b,
+    enum sshkey_serialize_rep opts)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	u_char have_info = 1;
+	u_int32_t idx;
+	int r;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (opts != SSHKEY_SERIALIZE_INFO)
+		return 0;
+	idx = k->xmss_sk ? PEEK_U32(k->xmss_sk) : state->idx;
+	if ((r = sshbuf_put_u8(b, have_info)) != 0 ||
+	    (r = sshbuf_put_u32(b, idx)) != 0 ||
+	    (r = sshbuf_put_u32(b, state->maxidx)) != 0)
+		return r;
+	return 0;
+}
+
+int
+sshkey_xmss_deserialize_pk_info(struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	u_char have_info;
+	int r;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	/* optional */
+	if (sshbuf_len(b) == 0)
+		return 0;
+	if ((r = sshbuf_get_u8(b, &have_info)) != 0)
+		return r;
+	if (have_info != 1)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshbuf_get_u32(b, &state->idx)) != 0 ||
+	    (r = sshbuf_get_u32(b, &state->maxidx)) != 0)
+		return r;
+	return 0;
+}
+
+int
+sshkey_xmss_generate_private_key(struct sshkey *k, int bits)
+{
+	int r;
+	const char *name;
+
+	if (bits == 10) {
+		name = XMSS_SHA2_256_W16_H10_NAME;
+	} else if (bits == 16) {
+		name = XMSS_SHA2_256_W16_H16_NAME;
+	} else if (bits == 20) {
+		name = XMSS_SHA2_256_W16_H20_NAME;
+	} else {
+		name = XMSS_DEFAULT_NAME;
+	}
+	if ((r = sshkey_xmss_init(k, name)) != 0 ||
+	    (r = sshkey_xmss_init_bds_state(k)) != 0 ||
+	    (r = sshkey_xmss_init_enc_key(k, XMSS_CIPHERNAME)) != 0)
+		return r;
+	if ((k->xmss_pk = malloc(sshkey_xmss_pklen(k))) == NULL ||
+	    (k->xmss_sk = malloc(sshkey_xmss_sklen(k))) == NULL) {
+		return SSH_ERR_ALLOC_FAIL;
+	}
+	xmss_keypair(k->xmss_pk, k->xmss_sk, sshkey_xmss_bds_state(k),
+	    sshkey_xmss_params(k));
+	return 0;
+}
+
+int
+sshkey_xmss_get_state_from_file(struct sshkey *k, const char *filename,
+    int *have_file, int printerror)
+{
+	struct sshbuf *b = NULL, *enc = NULL;
+	int ret = SSH_ERR_SYSTEM_ERROR, r, fd = -1;
+	u_int32_t len;
+	unsigned char buf[4], *data = NULL;
+
+	*have_file = 0;
+	if ((fd = open(filename, O_RDONLY)) >= 0) {
+		*have_file = 1;
+		if (atomicio(read, fd, buf, sizeof(buf)) != sizeof(buf)) {
+			PRINT("corrupt state file: %s", filename);
+			goto done;
+		}
+		len = PEEK_U32(buf);
+		if ((data = calloc(len, 1)) == NULL) {
+			ret = SSH_ERR_ALLOC_FAIL;
+			goto done;
+		}
+		if (atomicio(read, fd, data, len) != len) {
+			PRINT("cannot read blob: %s", filename);
+			goto done;
+		}
+		if ((enc = sshbuf_from(data, len)) == NULL) {
+			ret = SSH_ERR_ALLOC_FAIL;
+			goto done;
+		}
+		sshkey_xmss_free_bds(k);
+		if ((r = sshkey_xmss_decrypt_state(k, enc, &b)) != 0) {
+			ret = r;
+			goto done;
+		}
+		if ((r = sshkey_xmss_deserialize_state(k, b)) != 0) {
+			ret = r;
+			goto done;
+		}
+		ret = 0;
+	}
+done:
+	if (fd != -1)
+		close(fd);
+	free(data);
+	sshbuf_free(enc);
+	sshbuf_free(b);
+	return ret;
+}
+
+int
+sshkey_xmss_get_state(const struct sshkey *k, int printerror)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	u_int32_t idx = 0;
+	char *filename = NULL;
+	char *statefile = NULL, *ostatefile = NULL, *lockfile = NULL;
+	int lockfd = -1, have_state = 0, have_ostate, tries = 0;
+	int ret = SSH_ERR_INVALID_ARGUMENT, r;
+
+	if (state == NULL)
+		goto done;
+	/*
+	 * If maxidx is set, then we are allowed a limited number
+	 * of signatures, but don't need to access the disk.
+	 * Otherwise we need to deal with the on-disk state.
+	 */
+	if (state->maxidx) {
+		/* xmss_sk always contains the current state */
+		idx = PEEK_U32(k->xmss_sk);
+		if (idx < state->maxidx) {
+			state->allow_update = 1;
+			return 0;
+		}
+		return SSH_ERR_INVALID_ARGUMENT;
+	}
+	if ((filename = k->xmss_filename) == NULL)
+		goto done;
+	if (asprintf(&lockfile, "%s.lock", filename) == -1 ||
+	    asprintf(&statefile, "%s.state", filename) == -1 ||
+	    asprintf(&ostatefile, "%s.ostate", filename) == -1) {
+		ret = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+	if ((lockfd = open(lockfile, O_CREAT|O_RDONLY, 0600)) == -1) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("cannot open/create: %s", lockfile);
+		goto done;
+	}
+	while (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
+		if (errno != EWOULDBLOCK) {
+			ret = SSH_ERR_SYSTEM_ERROR;
+			PRINT("cannot lock: %s", lockfile);
+			goto done;
+		}
+		if (++tries > 10) {
+			ret = SSH_ERR_SYSTEM_ERROR;
+			PRINT("giving up on: %s", lockfile);
+			goto done;
+		}
+		usleep(1000*100*tries);
+	}
+	/* XXX no longer const */
+	if ((r = sshkey_xmss_get_state_from_file((struct sshkey *)k,
+	    statefile, &have_state, printerror)) != 0) {
+		if ((r = sshkey_xmss_get_state_from_file((struct sshkey *)k,
+		    ostatefile, &have_ostate, printerror)) == 0) {
+			state->allow_update = 1;
+			r = sshkey_xmss_forward_state(k, 1);
+			state->idx = PEEK_U32(k->xmss_sk);
+			state->allow_update = 0;
+		}
+	}
+	if (!have_state && !have_ostate) {
+		/* check that bds state is initialized */
+		if (state->bds.auth == NULL)
+			goto done;
+		PRINT("start from scratch idx 0: %u", state->idx);
+	} else if (r != 0) {
+		ret = r;
+		goto done;
+	}
+	if (state->idx + 1 < state->idx) {
+		PRINT("state wrap: %u", state->idx);
+		goto done;
+	}
+	state->have_state = have_state;
+	state->lockfd = lockfd;
+	state->allow_update = 1;
+	lockfd = -1;
+	ret = 0;
+done:
+	if (lockfd != -1)
+		close(lockfd);
+	free(lockfile);
+	free(statefile);
+	free(ostatefile);
+	return ret;
+}
+
+int
+sshkey_xmss_forward_state(const struct sshkey *k, u_int32_t reserve)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	u_char *sig = NULL;
+	size_t required_siglen;
+	unsigned long long smlen;
+	u_char data;
+	int ret, r;
+
+	if (state == NULL || !state->allow_update)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (reserve == 0)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (state->idx + reserve <= state->idx)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshkey_xmss_siglen(k, &required_siglen)) != 0)
+		return r;
+	if ((sig = malloc(required_siglen)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	while (reserve-- > 0) {
+		state->idx = PEEK_U32(k->xmss_sk);
+		smlen = required_siglen;
+		if ((ret = xmss_sign(k->xmss_sk, sshkey_xmss_bds_state(k),
+		    sig, &smlen, &data, 0, sshkey_xmss_params(k))) != 0) {
+			r = SSH_ERR_INVALID_ARGUMENT;
+			break;
+		}
+	}
+	free(sig);
+	return r;
+}
+
+int
+sshkey_xmss_update_state(const struct sshkey *k, int printerror)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	struct sshbuf *b = NULL, *enc = NULL;
+	u_int32_t idx = 0;
+	unsigned char buf[4];
+	char *filename = NULL;
+	char *statefile = NULL, *ostatefile = NULL, *nstatefile = NULL;
+	int fd = -1;
+	int ret = SSH_ERR_INVALID_ARGUMENT;
+
+	if (state == NULL || !state->allow_update)
+		return ret;
+	if (state->maxidx) {
+		/* no update since the number of signatures is limited */
+		ret = 0;
+		goto done;
+	}
+	idx = PEEK_U32(k->xmss_sk);
+	if (idx == state->idx) {
+		/* no signature happened, no need to update */
+		ret = 0;
+		goto done;
+	} else if (idx != state->idx + 1) {
+		PRINT("more than one signature happened: idx %u state %u",
+		    idx, state->idx);
+		goto done;
+	}
+	state->idx = idx;
+	if ((filename = k->xmss_filename) == NULL)
+		goto done;
+	if (asprintf(&statefile, "%s.state", filename) == -1 ||
+	    asprintf(&ostatefile, "%s.ostate", filename) == -1 ||
+	    asprintf(&nstatefile, "%s.nstate", filename) == -1) {
+		ret = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+	unlink(nstatefile);
+	if ((b = sshbuf_new()) == NULL) {
+		ret = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+	if ((ret = sshkey_xmss_serialize_state(k, b)) != 0) {
+		PRINT("SERLIALIZE FAILED: %d", ret);
+		goto done;
+	}
+	if ((ret = sshkey_xmss_encrypt_state(k, b, &enc)) != 0) {
+		PRINT("ENCRYPT FAILED: %d", ret);
+		goto done;
+	}
+	if ((fd = open(nstatefile, O_CREAT|O_WRONLY|O_EXCL, 0600)) == -1) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("open new state file: %s", nstatefile);
+		goto done;
+	}
+	POKE_U32(buf, sshbuf_len(enc));
+	if (atomicio(vwrite, fd, buf, sizeof(buf)) != sizeof(buf)) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("write new state file hdr: %s", nstatefile);
+		close(fd);
+		goto done;
+	}
+	if (atomicio(vwrite, fd, sshbuf_mutable_ptr(enc), sshbuf_len(enc)) !=
+	    sshbuf_len(enc)) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("write new state file data: %s", nstatefile);
+		close(fd);
+		goto done;
+	}
+	if (fsync(fd) == -1) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("sync new state file: %s", nstatefile);
+		close(fd);
+		goto done;
+	}
+	if (close(fd) == -1) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("close new state file: %s", nstatefile);
+		goto done;
+	}
+	if (state->have_state) {
+		unlink(ostatefile);
+		if (link(statefile, ostatefile)) {
+			ret = SSH_ERR_SYSTEM_ERROR;
+			PRINT("backup state %s to %s", statefile, ostatefile);
+			goto done;
+		}
+	}
+	if (rename(nstatefile, statefile) == -1) {
+		ret = SSH_ERR_SYSTEM_ERROR;
+		PRINT("rename %s to %s", nstatefile, statefile);
+		goto done;
+	}
+	ret = 0;
+done:
+	if (state->lockfd != -1) {
+		close(state->lockfd);
+		state->lockfd = -1;
+	}
+	if (nstatefile)
+		unlink(nstatefile);
+	free(statefile);
+	free(ostatefile);
+	free(nstatefile);
+	sshbuf_free(b);
+	sshbuf_free(enc);
+	return ret;
+}
+
+int
+sshkey_xmss_serialize_state(const struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	treehash_inst *th;
+	u_int32_t i, node;
+	int r;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (state->stack == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	state->stackoffset = state->bds.stackoffset;	/* copy back */
+	if ((r = sshbuf_put_cstring(b, SSH_XMSS_K2_MAGIC)) != 0 ||
+	    (r = sshbuf_put_u32(b, state->idx)) != 0 ||
+	    (r = sshbuf_put_string(b, state->stack, num_stack(state))) != 0 ||
+	    (r = sshbuf_put_u32(b, state->stackoffset)) != 0 ||
+	    (r = sshbuf_put_string(b, state->stacklevels, num_stacklevels(state))) != 0 ||
+	    (r = sshbuf_put_string(b, state->auth, num_auth(state))) != 0 ||
+	    (r = sshbuf_put_string(b, state->keep, num_keep(state))) != 0 ||
+	    (r = sshbuf_put_string(b, state->th_nodes, num_th_nodes(state))) != 0 ||
+	    (r = sshbuf_put_string(b, state->retain, num_retain(state))) != 0 ||
+	    (r = sshbuf_put_u32(b, num_treehash(state))) != 0)
+		return r;
+	for (i = 0; i < num_treehash(state); i++) {
+		th = &state->treehash[i];
+		node = th->node - state->th_nodes;
+		if ((r = sshbuf_put_u32(b, th->h)) != 0 ||
+		    (r = sshbuf_put_u32(b, th->next_idx)) != 0 ||
+		    (r = sshbuf_put_u32(b, th->stackusage)) != 0 ||
+		    (r = sshbuf_put_u8(b, th->completed)) != 0 ||
+		    (r = sshbuf_put_u32(b, node)) != 0)
+			return r;
+	}
+	return 0;
+}
+
+int
+sshkey_xmss_serialize_state_opt(const struct sshkey *k, struct sshbuf *b,
+    enum sshkey_serialize_rep opts)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	int r = SSH_ERR_INVALID_ARGUMENT;
+	u_char have_stack, have_filename, have_enc;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshbuf_put_u8(b, opts)) != 0)
+		return r;
+	switch (opts) {
+	case SSHKEY_SERIALIZE_STATE:
+		r = sshkey_xmss_serialize_state(k, b);
+		break;
+	case SSHKEY_SERIALIZE_FULL:
+		if ((r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
+			return r;
+		r = sshkey_xmss_serialize_state(k, b);
+		break;
+	case SSHKEY_SERIALIZE_SHIELD:
+		/* all of stack/filename/enc are optional */
+		have_stack = state->stack != NULL;
+		if ((r = sshbuf_put_u8(b, have_stack)) != 0)
+			return r;
+		if (have_stack) {
+			state->idx = PEEK_U32(k->xmss_sk);	/* update */
+			if ((r = sshkey_xmss_serialize_state(k, b)) != 0)
+				return r;
+		}
+		have_filename = k->xmss_filename != NULL;
+		if ((r = sshbuf_put_u8(b, have_filename)) != 0)
+			return r;
+		if (have_filename &&
+		    (r = sshbuf_put_cstring(b, k->xmss_filename)) != 0)
+			return r;
+		have_enc = state->enc_keyiv != NULL;
+		if ((r = sshbuf_put_u8(b, have_enc)) != 0)
+			return r;
+		if (have_enc &&
+		    (r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_put_u32(b, state->maxidx)) != 0 ||
+		    (r = sshbuf_put_u8(b, state->allow_update)) != 0)
+			return r;
+		break;
+	case SSHKEY_SERIALIZE_DEFAULT:
+		r = 0;
+		break;
+	default:
+		r = SSH_ERR_INVALID_ARGUMENT;
+		break;
+	}
+	return r;
+}
+
+int
+sshkey_xmss_deserialize_state(struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	treehash_inst *th;
+	u_int32_t i, lh, node;
+	size_t ls, lsl, la, lk, ln, lr;
+	char *magic;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (state == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (k->xmss_sk == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((state->treehash = calloc(num_treehash(state),
+	    sizeof(treehash_inst))) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_get_cstring(b, &magic, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(b, &state->idx)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->stack, &ls)) != 0 ||
+	    (r = sshbuf_get_u32(b, &state->stackoffset)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->stacklevels, &lsl)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->auth, &la)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->keep, &lk)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->th_nodes, &ln)) != 0 ||
+	    (r = sshbuf_get_string(b, &state->retain, &lr)) != 0 ||
+	    (r = sshbuf_get_u32(b, &lh)) != 0)
+		goto out;
+	if (strcmp(magic, SSH_XMSS_K2_MAGIC) != 0) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	/* XXX check stackoffset */
+	if (ls != num_stack(state) ||
+	    lsl != num_stacklevels(state) ||
+	    la != num_auth(state) ||
+	    lk != num_keep(state) ||
+	    ln != num_th_nodes(state) ||
+	    lr != num_retain(state) ||
+	    lh != num_treehash(state)) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	for (i = 0; i < num_treehash(state); i++) {
+		th = &state->treehash[i];
+		if ((r = sshbuf_get_u32(b, &th->h)) != 0 ||
+		    (r = sshbuf_get_u32(b, &th->next_idx)) != 0 ||
+		    (r = sshbuf_get_u32(b, &th->stackusage)) != 0 ||
+		    (r = sshbuf_get_u8(b, &th->completed)) != 0 ||
+		    (r = sshbuf_get_u32(b, &node)) != 0)
+			goto out;
+		if (node < num_th_nodes(state))
+			th->node = &state->th_nodes[node];
+	}
+	POKE_U32(k->xmss_sk, state->idx);
+	xmss_set_bds_state(&state->bds, state->stack, state->stackoffset,
+	    state->stacklevels, state->auth, state->keep, state->treehash,
+	    state->retain, 0);
+	/* success */
+	r = 0;
+ out:
+	free(magic);
+	return r;
+}
+
+int
+sshkey_xmss_deserialize_state_opt(struct sshkey *k, struct sshbuf *b)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	enum sshkey_serialize_rep opts;
+	u_char have_state, have_stack, have_filename, have_enc;
+	int r;
+
+	if ((r = sshbuf_get_u8(b, &have_state)) != 0)
+		return r;
+
+	opts = have_state;
+	switch (opts) {
+	case SSHKEY_SERIALIZE_DEFAULT:
+		r = 0;
+		break;
+	case SSHKEY_SERIALIZE_SHIELD:
+		if ((r = sshbuf_get_u8(b, &have_stack)) != 0)
+			return r;
+		if (have_stack &&
+		    (r = sshkey_xmss_deserialize_state(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_get_u8(b, &have_filename)) != 0)
+			return r;
+		if (have_filename &&
+		    (r = sshbuf_get_cstring(b, &k->xmss_filename, NULL)) != 0)
+			return r;
+		if ((r = sshbuf_get_u8(b, &have_enc)) != 0)
+			return r;
+		if (have_enc &&
+		    (r = sshkey_xmss_deserialize_enc_key(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_get_u32(b, &state->maxidx)) != 0 ||
+		    (r = sshbuf_get_u8(b, &state->allow_update)) != 0)
+			return r;
+		break;
+	case SSHKEY_SERIALIZE_STATE:
+		if ((r = sshkey_xmss_deserialize_state(k, b)) != 0)
+			return r;
+		break;
+	case SSHKEY_SERIALIZE_FULL:
+		if ((r = sshkey_xmss_deserialize_enc_key(k, b)) != 0 ||
+		    (r = sshkey_xmss_deserialize_state(k, b)) != 0)
+			return r;
+		break;
+	default:
+		r = SSH_ERR_INVALID_FORMAT;
+		break;
+	}
+	return r;
+}
+
+int
+sshkey_xmss_encrypt_state(const struct sshkey *k, struct sshbuf *b,
+   struct sshbuf **retp)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	struct sshbuf *encrypted = NULL, *encoded = NULL, *padded = NULL;
+	struct sshcipher_ctx *ciphercontext = NULL;
+	const struct sshcipher *cipher;
+	u_char *cp, *key, *iv = NULL;
+	size_t i, keylen, ivlen, blocksize, authlen, encrypted_len, aadlen;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (retp != NULL)
+		*retp = NULL;
+	if (state == NULL ||
+	    state->enc_keyiv == NULL ||
+	    state->enc_ciphername == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	if ((cipher = cipher_by_name(state->enc_ciphername)) == NULL) {
+		r = SSH_ERR_INTERNAL_ERROR;
+		goto out;
+	}
+	blocksize = cipher_blocksize(cipher);
+	keylen = cipher_keylen(cipher);
+	ivlen = cipher_ivlen(cipher);
+	authlen = cipher_authlen(cipher);
+	if (state->enc_keyiv_len != keylen + ivlen) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	key = state->enc_keyiv;
+	if ((encrypted = sshbuf_new()) == NULL ||
+	    (encoded = sshbuf_new()) == NULL ||
+	    (padded = sshbuf_new()) == NULL ||
+	    (iv = malloc(ivlen)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+
+	/* replace first 4 bytes of IV with index to ensure uniqueness */
+	memcpy(iv, key + keylen, ivlen);
+	POKE_U32(iv, state->idx);
+
+	if ((r = sshbuf_put(encoded, XMSS_MAGIC, sizeof(XMSS_MAGIC))) != 0 ||
+	    (r = sshbuf_put_u32(encoded, state->idx)) != 0)
+		goto out;
+
+	/* padded state will be encrypted */
+	if ((r = sshbuf_putb(padded, b)) != 0)
+		goto out;
+	i = 0;
+	while (sshbuf_len(padded) % blocksize) {
+		if ((r = sshbuf_put_u8(padded, ++i & 0xff)) != 0)
+			goto out;
+	}
+	encrypted_len = sshbuf_len(padded);
+
+	/* header including the length of state is used as AAD */
+	if ((r = sshbuf_put_u32(encoded, encrypted_len)) != 0)
+		goto out;
+	aadlen = sshbuf_len(encoded);
+
+	/* concat header and state */
+	if ((r = sshbuf_putb(encoded, padded)) != 0)
+		goto out;
+
+	/* reserve space for encryption of encoded data plus auth tag */
+	/* encrypt at offset addlen */
+	if ((r = sshbuf_reserve(encrypted,
+	    encrypted_len + aadlen + authlen, &cp)) != 0 ||
+	    (r = cipher_init(&ciphercontext, cipher, key, keylen,
+	    iv, ivlen, 1)) != 0 ||
+	    (r = cipher_crypt(ciphercontext, 0, cp, sshbuf_ptr(encoded),
+	    encrypted_len, aadlen, authlen)) != 0)
+		goto out;
+
+	/* success */
+	r = 0;
+ out:
+	if (retp != NULL) {
+		*retp = encrypted;
+		encrypted = NULL;
+	}
+	sshbuf_free(padded);
+	sshbuf_free(encoded);
+	sshbuf_free(encrypted);
+	cipher_free(ciphercontext);
+	free(iv);
+	return r;
+}
+
+int
+sshkey_xmss_decrypt_state(const struct sshkey *k, struct sshbuf *encoded,
+   struct sshbuf **retp)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	struct sshbuf *copy = NULL, *decrypted = NULL;
+	struct sshcipher_ctx *ciphercontext = NULL;
+	const struct sshcipher *cipher = NULL;
+	u_char *key, *iv = NULL, *dp;
+	size_t keylen, ivlen, authlen, aadlen;
+	u_int blocksize, encrypted_len, index;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (retp != NULL)
+		*retp = NULL;
+	if (state == NULL ||
+	    state->enc_keyiv == NULL ||
+	    state->enc_ciphername == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	if ((cipher = cipher_by_name(state->enc_ciphername)) == NULL) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	blocksize = cipher_blocksize(cipher);
+	keylen = cipher_keylen(cipher);
+	ivlen = cipher_ivlen(cipher);
+	authlen = cipher_authlen(cipher);
+	if (state->enc_keyiv_len != keylen + ivlen) {
+		r = SSH_ERR_INTERNAL_ERROR;
+		goto out;
+	}
+	key = state->enc_keyiv;
+
+	if ((copy = sshbuf_fromb(encoded)) == NULL ||
+	    (decrypted = sshbuf_new()) == NULL ||
+	    (iv = malloc(ivlen)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+
+	/* check magic */
+	if (sshbuf_len(encoded) < sizeof(XMSS_MAGIC) ||
+	    memcmp(sshbuf_ptr(encoded), XMSS_MAGIC, sizeof(XMSS_MAGIC))) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	/* parse public portion */
+	if ((r = sshbuf_consume(encoded, sizeof(XMSS_MAGIC))) != 0 ||
+	    (r = sshbuf_get_u32(encoded, &index)) != 0 ||
+	    (r = sshbuf_get_u32(encoded, &encrypted_len)) != 0)
+		goto out;
+
+	/* check size of encrypted key blob */
+	if (encrypted_len < blocksize || (encrypted_len % blocksize) != 0) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	/* check that an appropriate amount of auth data is present */
+	if (sshbuf_len(encoded) < authlen ||
+	    sshbuf_len(encoded) - authlen < encrypted_len) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+
+	aadlen = sshbuf_len(copy) - sshbuf_len(encoded);
+
+	/* replace first 4 bytes of IV with index to ensure uniqueness */
+	memcpy(iv, key + keylen, ivlen);
+	POKE_U32(iv, index);
+
+	/* decrypt private state of key */
+	if ((r = sshbuf_reserve(decrypted, aadlen + encrypted_len, &dp)) != 0 ||
+	    (r = cipher_init(&ciphercontext, cipher, key, keylen,
+	    iv, ivlen, 0)) != 0 ||
+	    (r = cipher_crypt(ciphercontext, 0, dp, sshbuf_ptr(copy),
+	    encrypted_len, aadlen, authlen)) != 0)
+		goto out;
+
+	/* there should be no trailing data */
+	if ((r = sshbuf_consume(encoded, encrypted_len + authlen)) != 0)
+		goto out;
+	if (sshbuf_len(encoded) != 0) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+
+	/* remove AAD */
+	if ((r = sshbuf_consume(decrypted, aadlen)) != 0)
+		goto out;
+	/* XXX encrypted includes unchecked padding */
+
+	/* success */
+	r = 0;
+	if (retp != NULL) {
+		*retp = decrypted;
+		decrypted = NULL;
+	}
+ out:
+	cipher_free(ciphercontext);
+	sshbuf_free(copy);
+	sshbuf_free(decrypted);
+	free(iv);
+	return r;
+}
+
+u_int32_t
+sshkey_xmss_signatures_left(const struct sshkey *k)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+	u_int32_t idx;
+
+	if (sshkey_type_plain(k->type) == KEY_XMSS && state &&
+	    state->maxidx) {
+		idx = k->xmss_sk ? PEEK_U32(k->xmss_sk) : state->idx;
+		if (idx < state->maxidx)
+			return state->maxidx - idx;
+	}
+	return 0;
+}
+
+int
+sshkey_xmss_enable_maxsign(struct sshkey *k, u_int32_t maxsign)
+{
+	struct ssh_xmss_state *state = k->xmss_state;
+
+	if (sshkey_type_plain(k->type) != KEY_XMSS)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if (maxsign == 0)
+		return 0;
+	if (state->idx + maxsign < state->idx)
+		return SSH_ERR_INVALID_ARGUMENT;
+	state->maxidx = state->idx + maxsign;
+	return 0;
+}
+#endif /* WITH_XMSS */