Exemplo n.º 1
0
int
ciphers_valid(const char *names)
{
	const Cipher *c;
	char *cipher_list, *cp;
	char *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	cipher_list = cp = xstrdup(names);
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	    (p = strsep(&cp, CIPHER_SEP))) {
		c = cipher_by_name(p);
		if (c == NULL || (c->number != SSH_CIPHER_SSH2 && 
c->number != SSH_CIPHER_NONE)) {
			debug("bad cipher %s [%s]", p, names);
			free(cipher_list);
			return 0;
		} else {
			debug3("cipher ok: %s [%s]", p, names);
		}
	}
	debug3("ciphers ok: [%s]", names);
	free(cipher_list);
	return 1;
}
Exemplo n.º 2
0
/* Export key state after authentication */
Newkeys *
mm_newkeys_from_blob(u_char *blob, int blen)
{
	Buffer b;
	u_int len;
	Newkeys *newkey = NULL;
	Enc *enc;
	Mac *mac;
	Comp *comp;

	debug3("%s: %p(%d)", __func__, blob, blen);
#ifdef DEBUG_PK
	dump_base64(stderr, blob, blen);
#endif
	buffer_init(&b);
	buffer_append(&b, blob, blen);

	newkey = xmalloc(sizeof(*newkey));
	enc = &newkey->enc;
	mac = &newkey->mac;
	comp = &newkey->comp;

	/* Enc structure */
	enc->name = buffer_get_string(&b, NULL);
	buffer_get(&b, &enc->cipher, sizeof(enc->cipher));
	enc->enabled = buffer_get_int(&b);
	enc->block_size = buffer_get_int(&b);
	enc->key = buffer_get_string(&b, &enc->key_len);
	enc->iv = buffer_get_string(&b, &len);
	if (len != enc->block_size)
		fatal("%s: bad ivlen: expected %u != %u", __func__,
		    enc->block_size, len);

	if (enc->name == NULL || cipher_by_name(enc->name) != enc->cipher)
		fatal("%s: bad cipher name %s or pointer %p", __func__,
		    enc->name, enc->cipher);

	/* Mac structure */
	mac->name = buffer_get_string(&b, NULL);
	if (mac->name == NULL || mac_setup(mac, mac->name) == -1)
		fatal("%s: can not setup mac %s", __func__, mac->name);
	mac->enabled = buffer_get_int(&b);
	mac->key = buffer_get_string(&b, &len);
	if (len > mac->key_len)
		fatal("%s: bad mac key length: %u > %d", __func__, len,
		    mac->key_len);
	mac->key_len = len;

	/* Comp structure */
	comp->type = buffer_get_int(&b);
	comp->enabled = buffer_get_int(&b);
	comp->name = buffer_get_string(&b, NULL);

	len = buffer_len(&b);
	if (len != 0)
		error("newkeys_from_blob: remaining bytes in blob %u", len);
	buffer_free(&b);
	return (newkey);
}
Exemplo n.º 3
0
int
cipher_number(const char *name)
{
	Cipher *c;
	if (name == NULL)
		return -1;
	c = cipher_by_name(name);
	return (c==NULL) ? -1 : c->number;
}
Exemplo n.º 4
0
int PEM_get_EVP_CIPHER_INFO(char *header, EVP_CIPHER_INFO *cipher)
	{
	const EVP_CIPHER *enc=NULL;
	char *p,c;
	char **header_pp = &header;

	cipher->cipher=NULL;
	if ((header == NULL) || (*header == '\0') || (*header == '\n'))
		return(1);
	if (strncmp(header,"Proc-Type: ",11) != 0)
		{ OPENSSL_PUT_ERROR(PEM, PEM_get_EVP_CIPHER_INFO, PEM_R_NOT_PROC_TYPE); return(0); }
	header+=11;
	if (*header != '4') return(0); header++;
	if (*header != ',') return(0); header++;
	if (strncmp(header,"ENCRYPTED",9) != 0)
		{ OPENSSL_PUT_ERROR(PEM, PEM_get_EVP_CIPHER_INFO, PEM_R_NOT_ENCRYPTED); return(0); }
	for (; (*header != '\n') && (*header != '\0'); header++)
		;
	if (*header == '\0')
		{ OPENSSL_PUT_ERROR(PEM, PEM_get_EVP_CIPHER_INFO, PEM_R_SHORT_HEADER); return(0); }
	header++;
	if (strncmp(header,"DEK-Info: ",10) != 0)
		{ OPENSSL_PUT_ERROR(PEM, PEM_get_EVP_CIPHER_INFO, PEM_R_NOT_DEK_INFO); return(0); }
	header+=10;

	p=header;
	for (;;)
		{
		c= *header;
		if (!(	((c >= 'A') && (c <= 'Z')) || (c == '-') ||
			((c >= '0') && (c <= '9'))))
			break;
		header++;
		}
	*header='\0';
	cipher->cipher=enc=cipher_by_name(p);
	*header=c;
	header++;

	if (enc == NULL)
		{
		OPENSSL_PUT_ERROR(PEM, PEM_get_EVP_CIPHER_INFO, PEM_R_UNSUPPORTED_ENCRYPTION);
		return(0);
		}
	if (!load_iv(header_pp,&(cipher->iv[0]),EVP_CIPHER_iv_length(enc)))
		return(0);

	return(1);
	}
Exemplo n.º 5
0
static void
choose_enc(Enc *enc, char *client, char *server)
{
	char *name = match_list(client, server, NULL);
	if (name == NULL)
		fatal("no matching cipher found: client %s server %s", client, server);
	if ((enc->cipher = cipher_by_name(name)) == NULL)
		fatal("matching cipher is not supported: %s", name);
	enc->name = name;
	enc->enabled = 0;
	enc->iv = NULL;
	enc->key = NULL;
	enc->key_len = cipher_keylen(enc->cipher);
	enc->block_size = cipher_blocksize(enc->cipher);
}
Exemplo n.º 6
0
int
ciphers_valid(const char *names)
{
	Cipher *c;
	char *cipher_list, *cp;
	char *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	cipher_list = cp = xstrdup(names);
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	    (p = strsep(&cp, CIPHER_SEP))) {
		c = cipher_by_name(p);
#ifdef NONE_CIPHER_ENABLED
		if (c == NULL || (c->number != SSH_CIPHER_SSH2 &&
		    c->number != SSH_CIPHER_NONE)) {
#else
		if (c == NULL || (c->number != SSH_CIPHER_SSH2)) {
#endif
			debug("bad cipher %s [%s]", p, names);
			xfree(cipher_list);
			return 0;
		} else {
			debug3("cipher ok: %s [%s]", p, names);
		}
	}
	debug3("ciphers ok: [%s]", names);
	xfree(cipher_list);
	return 1;
}

/*
 * Parses the name of the cipher.  Returns the number of the corresponding
 * cipher, or -1 on error.
 */

int
cipher_number(const char *name)
{
	Cipher *c;
	if (name == NULL)
		return -1;
	for (c = ciphers; c->name != NULL; c++)
		if (strcasecmp(c->name, name) == 0)
			return c->number;
	return -1;
}
Exemplo n.º 7
0
static int
choose_enc(Enc *enc, char *client, char *server)
{
	char *name = match_list(client, server, NULL);

	if (name == NULL)
		return SSH_ERR_NO_CIPHER_ALG_MATCH;
	if ((enc->cipher = cipher_by_name(name)) == NULL)
		return SSH_ERR_INTERNAL_ERROR;
	enc->name = name;
	enc->enabled = 0;
	enc->iv = NULL;
	enc->key = NULL;
	enc->key_len = cipher_keylen(enc->cipher);
	enc->block_size = cipher_blocksize(enc->cipher);
	return 0;
}
Exemplo n.º 8
0
int
ciphers_valid(const char *names)
{
	const struct sshcipher *c;
	char *cipher_list, *cp;
	char *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	if ((cipher_list = cp = strdup(names)) == NULL)
		return 0;
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	    (p = strsep(&cp, CIPHER_SEP))) {
		c = cipher_by_name(p);
		if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
			free(cipher_list);
			return 0;
		}
	}
	free(cipher_list);
	return 1;
}
Exemplo n.º 9
0
int
ciphers_valid(const char *names)
{
	struct sshcipher *c;
	char *cipher_list, *cp;
	char *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	if ((cipher_list = cp = strdup(names)) == NULL)
		return 0;
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	    (p = strsep(&cp, CIPHER_SEP))) {
		c = cipher_by_name(p);
		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
			free(cipher_list);
			return 0;
		}
	}
	free(cipher_list);
	return 1;
}
Exemplo n.º 10
0
/** Constructor.
 * @param key encryption key, can be any string, will be processed to meet
 * the cipher's requirements.
 * @param cipher_name Cipher combination to use, currently supported are
 * aes-128-ecb, aes-128-cbc, aes-256-ecb, and aes-256-cbc
 */
BufferEncryptor::BufferEncryptor(const std::string &key, std::string cipher_name)
{
#ifdef HAVE_LIBCRYPTO
  cipher_ = cipher_by_name(cipher_name.c_str());
  cipher_id_ = cipher_name_to_id(cipher_name.c_str());

  const size_t key_size = EVP_CIPHER_key_length(cipher_);
  const size_t iv_size = EVP_CIPHER_iv_length(cipher_);
  key_ = (unsigned char *)malloc(key_size);
  unsigned char iv[iv_size];
  if( ! EVP_BytesToKey(cipher_, EVP_sha256(), NULL,
		       (const unsigned char *)key.c_str(), key.size(), 8, key_, iv))
  {
    throw std::runtime_error("Failed to generate key");
  }

  if (!RAND_bytes((unsigned char *)&iv_, sizeof(iv_))) {
    throw std::runtime_error("Failed to generate IV");
  }
#else
    throw std::runtime_error("Encryption support not available");
#endif
}
Exemplo n.º 11
0
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;
}
Exemplo n.º 12
0
int
ciphers_valid(const char *names)
{
	const Cipher *c;
	char *cipher_list, *cp;
	char *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	cipher_list = cp = xstrdup(names);
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	    (p = strsep(&cp, CIPHER_SEP))) {
		c = cipher_by_name(p);
#ifdef NONE_CIPHER_ENABLED
		if (c == NULL || (c->number != SSH_CIPHER_SSH2 &&
		    c->number != SSH_CIPHER_NONE)) {
#else
		if (c == NULL || (c->number != SSH_CIPHER_SSH2)) {
#endif
			debug("bad cipher %s [%s]", p, names);
			free(cipher_list);
			return 0;
		}
	}
	debug3("ciphers ok: [%s]", names);
	free(cipher_list);
	return 1;
}

/*
 * Parses the name of the cipher.  Returns the number of the corresponding
 * cipher, or -1 on error.
 */

int
cipher_number(const char *name)
{
	const Cipher *c;
	if (name == NULL)
		return -1;
	for (c = ciphers; c->name != NULL; c++)
		if (strcasecmp(c->name, name) == 0)
			return c->number;
	return -1;
}

char *
cipher_name(int id)
{
	const Cipher *c = cipher_by_number(id);
	return (c==NULL) ? "<unknown>" : c->name;
}

void
cipher_init(CipherContext *cc, const Cipher *cipher,
    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
    int do_encrypt)
{
	static int dowarn = 1;
#ifdef SSH_OLD_EVP
	EVP_CIPHER *type;
#else
	const EVP_CIPHER *type;
	int klen;
#endif
	u_char *junk, *discard;

	if (cipher->number == SSH_CIPHER_DES) {
		if (dowarn) {
			error("Warning: use of DES is strongly discouraged "
			    "due to cryptographic weaknesses");
			dowarn = 0;
		}
		if (keylen > 8)
			keylen = 8;
	}
	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
	cc->encrypt = do_encrypt;

	if (keylen < cipher->key_len)
		fatal("cipher_init: key length %d is insufficient for %s.",
		    keylen, cipher->name);
	if (iv != NULL && ivlen < cipher_ivlen(cipher))
		fatal("cipher_init: iv length %d is insufficient for %s.",
		    ivlen, cipher->name);
	cc->cipher = cipher;

	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
		chachapoly_init(&cc->cp_ctx, key, keylen);
		return;
	}
	type = (*cipher->evptype)();
	EVP_CIPHER_CTX_init(&cc->evp);
#ifdef SSH_OLD_EVP
	if (type->key_len > 0 && type->key_len != keylen) {
		debug("cipher_init: set keylen (%d -> %d)",
		    type->key_len, keylen);
		type->key_len = keylen;
	}
	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
	    (do_encrypt == CIPHER_ENCRYPT));
#else
	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
		fatal("cipher_init: EVP_CipherInit failed for %s",
		    cipher->name);
	if (cipher_authlen(cipher) &&
	    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
	    -1, (u_char *)iv))
		fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s",
		    cipher->name);
	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
	if (klen > 0 && keylen != (u_int)klen) {
		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
			fatal("cipher_init: set keylen failed (%d -> %d)",
			    klen, keylen);
	}
	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
		    cipher->name);
#endif

	if (cipher->discard_len > 0) {
		junk = xmalloc(cipher->discard_len);
		discard = xmalloc(cipher->discard_len);
		if (EVP_Cipher(&cc->evp, discard, junk,
		    cipher->discard_len) == 0)
			fatal("evp_crypt: EVP_Cipher failed during discard");
		explicit_bzero(discard, cipher->discard_len);
		free(junk);
		free(discard);
	}
}

/*
 * cipher_crypt() operates as following:
 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
 * Theses bytes are treated as additional authenticated data for
 * authenticated encryption modes.
 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
 * This tag is written on encryption and verified on decryption.
 * Both 'aadlen' and 'authlen' can be set to 0.
 * cipher_crypt() returns 0 on success and -1 if the decryption integrity
 * check fails.
 */
int
cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src,
    u_int len, u_int aadlen, u_int authlen)
{
	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
		return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, len,
		    aadlen, authlen, cc->encrypt);
	if (authlen) {
		u_char lastiv[1];

		if (authlen != cipher_authlen(cc->cipher))
			fatal("%s: authlen mismatch %d", __func__, authlen);
		/* increment IV */
		if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
		    1, lastiv))
			fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
		/* set tag on decyption */
		if (!cc->encrypt &&
		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG,
		    authlen, (u_char *)src + aadlen + len))
			fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__);
	}
	if (aadlen) {
		if (authlen &&
		    EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0)
			fatal("%s: EVP_Cipher(aad) failed", __func__);
		memcpy(dest, src, aadlen);
	}
	if (len % cc->cipher->block_size)
		fatal("%s: bad plaintext length %d", __func__, len);
	if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen,
	    len) < 0)
		fatal("%s: EVP_Cipher failed", __func__);
	if (authlen) {
		/* compute tag (on encrypt) or verify tag (on decrypt) */
		if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) {
			if (cc->encrypt)
				fatal("%s: EVP_Cipher(final) failed", __func__);
			else
				return -1;
		}
		if (cc->encrypt &&
		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG,
		    authlen, dest + aadlen + len))
			fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__);
	}
	return 0;
}

/* Extract the packet length, including any decryption necessary beforehand */
int
cipher_get_length(CipherContext *cc, u_int *plenp, u_int seqnr,
    const u_char *cp, u_int len)
{
	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
		return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
		    cp, len);
	if (len < 4)
		return -1;
	*plenp = get_u32(cp);
	return 0;
}

void
cipher_cleanup(CipherContext *cc)
{
	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
		explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
	else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
}

/*
 * Selects the cipher, and keys if by computing the MD5 checksum of the
 * passphrase and using the resulting 16 bytes as the key.
 */

void
cipher_set_key_string(CipherContext *cc, const Cipher *cipher,
    const char *passphrase, int do_encrypt)
{
	u_char digest[16];

	if (ssh_digest_memory(SSH_DIGEST_MD5, passphrase, strlen(passphrase),
	    digest, sizeof(digest)) < 0)
		fatal("%s: md5 failed", __func__);

	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);

	explicit_bzero(digest, sizeof(digest));
}
Exemplo n.º 13
0
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) < encrypted_len + authlen) {
		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;
}
Exemplo n.º 14
0
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;
}