/*
 * Modifications for Lustre
 *
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 *
 * Author: Eric Mei <ericm@clusterfs.com>
 */

/*
 *  linux/net/sunrpc/gss_krb5_mech.c
 *  linux/net/sunrpc/gss_krb5_crypto.c
 *  linux/net/sunrpc/gss_krb5_seal.c
 *  linux/net/sunrpc/gss_krb5_seqnum.c
 *  linux/net/sunrpc/gss_krb5_unseal.c
 *
 *  Copyright (c) 2001 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Andy Adamson <andros@umich.edu>
 *  J. Bruce Fields <bfields@umich.edu>
 *
 *  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.
 *  3. Neither the name of the University nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED ``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 REGENTS OR CONTRIBUTORS 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.
 *
 */

#define DEBUG_SUBSYSTEM S_SEC
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/mutex.h>
#include <linux/crypto.h>

#include <obd.h>
#include <obd_class.h>
#include <obd_support.h>
#include <lustre/lustre_idl.h>
#include <lustre_net.h>
#include <lustre_import.h>
#include <lustre_sec.h>

#include "gss_err.h"
#include "gss_internal.h"
#include "gss_api.h"
#include "gss_asn1.h"
#include "gss_krb5.h"

static spinlock_t krb5_seq_lock;

struct krb5_enctype {
	char	   *ke_dispname;
	char	   *ke_enc_name;	    /* linux tfm name */
	char	   *ke_hash_name;	   /* linux tfm name */
	int	     ke_enc_mode;	    /* linux tfm mode */
	int	     ke_hash_size;	   /* checksum size */
	int	     ke_conf_size;	   /* confounder size */
	unsigned int    ke_hash_hmac:1;	 /* is hmac? */
};

/*
 * NOTE: for aes128-cts and aes256-cts, MIT implementation use CTS encryption.
 * but currently we simply CBC with padding, because linux doesn't support CTS
 * yet. this need to be fixed in the future.
 */
static struct krb5_enctype enctypes[] = {
	[ENCTYPE_DES_CBC_RAW] = {	       /* des-cbc-md5 */
		"des-cbc-md5",
		"cbc(des)",
		"md5",
		0,
		16,
		8,
		0,
	},
	[ENCTYPE_DES3_CBC_RAW] = {	      /* des3-hmac-sha1 */
		"des3-hmac-sha1",
		"cbc(des3_ede)",
		"hmac(sha1)",
		0,
		20,
		8,
		1,
	},
	[ENCTYPE_AES128_CTS_HMAC_SHA1_96] = {   /* aes128-cts */
		"aes128-cts-hmac-sha1-96",
		"cbc(aes)",
		"hmac(sha1)",
		0,
		12,
		16,
		1,
	},
	[ENCTYPE_AES256_CTS_HMAC_SHA1_96] = {   /* aes256-cts */
		"aes256-cts-hmac-sha1-96",
		"cbc(aes)",
		"hmac(sha1)",
		0,
		12,
		16,
		1,
	},
	[ENCTYPE_ARCFOUR_HMAC] = {	      /* arcfour-hmac-md5 */
		"arcfour-hmac-md5",
		"ecb(arc4)",
		"hmac(md5)",
		0,
		16,
		8,
		1,
	},
};

#define MAX_ENCTYPES    sizeof(enctypes)/sizeof(struct krb5_enctype)

static const char * enctype2str(__u32 enctype)
{
	if (enctype < MAX_ENCTYPES && enctypes[enctype].ke_dispname)
		return enctypes[enctype].ke_dispname;

	return "unknown";
}

static
int keyblock_init(struct krb5_keyblock *kb, char *alg_name, int alg_mode)
{
	kb->kb_tfm = crypto_alloc_blkcipher(alg_name, alg_mode, 0);
	if (IS_ERR(kb->kb_tfm)) {
		CERROR("failed to alloc tfm: %s, mode %d\n",
		       alg_name, alg_mode);
		return -1;
	}

	if (crypto_blkcipher_setkey(kb->kb_tfm, kb->kb_key.data, kb->kb_key.len)) {
		CERROR("failed to set %s key, len %d\n",
		       alg_name, kb->kb_key.len);
		return -1;
	}

	return 0;
}

static
int krb5_init_keys(struct krb5_ctx *kctx)
{
	struct krb5_enctype *ke;

	if (kctx->kc_enctype >= MAX_ENCTYPES ||
	    enctypes[kctx->kc_enctype].ke_hash_size == 0) {
		CERROR("unsupported enctype %x\n", kctx->kc_enctype);
		return -1;
	}

	ke = &enctypes[kctx->kc_enctype];

	/* tfm arc4 is stateful, user should alloc-use-free by his own */
	if (kctx->kc_enctype != ENCTYPE_ARCFOUR_HMAC &&
	    keyblock_init(&kctx->kc_keye, ke->ke_enc_name, ke->ke_enc_mode))
		return -1;

	/* tfm hmac is stateful, user should alloc-use-free by his own */
	if (ke->ke_hash_hmac == 0 &&
	    keyblock_init(&kctx->kc_keyi, ke->ke_enc_name, ke->ke_enc_mode))
		return -1;
	if (ke->ke_hash_hmac == 0 &&
	    keyblock_init(&kctx->kc_keyc, ke->ke_enc_name, ke->ke_enc_mode))
		return -1;

	return 0;
}

static
void keyblock_free(struct krb5_keyblock *kb)
{
	rawobj_free(&kb->kb_key);
	if (kb->kb_tfm)
		crypto_free_blkcipher(kb->kb_tfm);
}

static
int keyblock_dup(struct krb5_keyblock *new, struct krb5_keyblock *kb)
{
	return rawobj_dup(&new->kb_key, &kb->kb_key);
}

static
int get_bytes(char **ptr, const char *end, void *res, int len)
{
	char *p, *q;
	p = *ptr;
	q = p + len;
	if (q > end || q < p)
		return -1;
	memcpy(res, p, len);
	*ptr = q;
	return 0;
}

static
int get_rawobj(char **ptr, const char *end, rawobj_t *res)
{
	char   *p, *q;
	__u32   len;

	p = *ptr;
	if (get_bytes(&p, end, &len, sizeof(len)))
		return -1;

	q = p + len;
	if (q > end || q < p)
		return -1;

	OBD_ALLOC_LARGE(res->data, len);
	if (!res->data)
		return -1;

	res->len = len;
	memcpy(res->data, p, len);
	*ptr = q;
	return 0;
}

static
int get_keyblock(char **ptr, const char *end,
		 struct krb5_keyblock *kb, __u32 keysize)
{
	char *buf;

	OBD_ALLOC_LARGE(buf, keysize);
	if (buf == NULL)
		return -1;

	if (get_bytes(ptr, end, buf, keysize)) {
		OBD_FREE_LARGE(buf, keysize);
		return -1;
	}

	kb->kb_key.len = keysize;
	kb->kb_key.data = buf;
	return 0;
}

static
void delete_context_kerberos(struct krb5_ctx *kctx)
{
	rawobj_free(&kctx->kc_mech_used);

	keyblock_free(&kctx->kc_keye);
	keyblock_free(&kctx->kc_keyi);
	keyblock_free(&kctx->kc_keyc);
}

static
__u32 import_context_rfc1964(struct krb5_ctx *kctx, char *p, char *end)
{
	unsigned int    tmp_uint, keysize;

	/* seed_init flag */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)))
		goto out_err;
	kctx->kc_seed_init = (tmp_uint != 0);

	/* seed */
	if (get_bytes(&p, end, kctx->kc_seed, sizeof(kctx->kc_seed)))
		goto out_err;

	/* sign/seal algorithm, not really used now */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)) ||
	    get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)))
		goto out_err;

	/* end time */
	if (get_bytes(&p, end, &kctx->kc_endtime, sizeof(kctx->kc_endtime)))
		goto out_err;

	/* seq send */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)))
		goto out_err;
	kctx->kc_seq_send = tmp_uint;

	/* mech oid */
	if (get_rawobj(&p, end, &kctx->kc_mech_used))
		goto out_err;

	/* old style enc/seq keys in format:
	 *   - enctype (u32)
	 *   - keysize (u32)
	 *   - keydata
	 * we decompose them to fit into the new context
	 */

	/* enc key */
	if (get_bytes(&p, end, &kctx->kc_enctype, sizeof(kctx->kc_enctype)))
		goto out_err;

	if (get_bytes(&p, end, &keysize, sizeof(keysize)))
		goto out_err;

	if (get_keyblock(&p, end, &kctx->kc_keye, keysize))
		goto out_err;

	/* seq key */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)) ||
	    tmp_uint != kctx->kc_enctype)
		goto out_err;

	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)) ||
	    tmp_uint != keysize)
		goto out_err;

	if (get_keyblock(&p, end, &kctx->kc_keyc, keysize))
		goto out_err;

	/* old style fallback */
	if (keyblock_dup(&kctx->kc_keyi, &kctx->kc_keyc))
		goto out_err;

	if (p != end)
		goto out_err;

	CDEBUG(D_SEC, "successfully imported rfc1964 context\n");
	return 0;
out_err:
	return GSS_S_FAILURE;
}

/* Flags for version 2 context flags */
#define KRB5_CTX_FLAG_INITIATOR		0x00000001
#define KRB5_CTX_FLAG_CFX		0x00000002
#define KRB5_CTX_FLAG_ACCEPTOR_SUBKEY	0x00000004

static
__u32 import_context_rfc4121(struct krb5_ctx *kctx, char *p, char *end)
{
	unsigned int    tmp_uint, keysize;

	/* end time */
	if (get_bytes(&p, end, &kctx->kc_endtime, sizeof(kctx->kc_endtime)))
		goto out_err;

	/* flags */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)))
		goto out_err;

	if (tmp_uint & KRB5_CTX_FLAG_INITIATOR)
		kctx->kc_initiate = 1;
	if (tmp_uint & KRB5_CTX_FLAG_CFX)
		kctx->kc_cfx = 1;
	if (tmp_uint & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY)
		kctx->kc_have_acceptor_subkey = 1;

	/* seq send */
	if (get_bytes(&p, end, &kctx->kc_seq_send, sizeof(kctx->kc_seq_send)))
		goto out_err;

	/* enctype */
	if (get_bytes(&p, end, &kctx->kc_enctype, sizeof(kctx->kc_enctype)))
		goto out_err;

	/* size of each key */
	if (get_bytes(&p, end, &keysize, sizeof(keysize)))
		goto out_err;

	/* number of keys - should always be 3 */
	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint)))
		goto out_err;

	if (tmp_uint != 3) {
		CERROR("Invalid number of keys: %u\n", tmp_uint);
		goto out_err;
	}

	/* ke */
	if (get_keyblock(&p, end, &kctx->kc_keye, keysize))
		goto out_err;
	/* ki */
	if (get_keyblock(&p, end, &kctx->kc_keyi, keysize))
		goto out_err;
	/* ki */
	if (get_keyblock(&p, end, &kctx->kc_keyc, keysize))
		goto out_err;

	CDEBUG(D_SEC, "successfully imported v2 context\n");
	return 0;
out_err:
	return GSS_S_FAILURE;
}

/*
 * The whole purpose here is trying to keep user level gss context parsing
 * from nfs-utils unchanged as possible as we can, they are not quite mature
 * yet, and many stuff still not clear, like heimdal etc.
 */
static
__u32 gss_import_sec_context_kerberos(rawobj_t *inbuf,
				      struct gss_ctx *gctx)
{
	struct krb5_ctx *kctx;
	char	    *p = (char *) inbuf->data;
	char	    *end = (char *) (inbuf->data + inbuf->len);
	unsigned int     tmp_uint, rc;

	if (get_bytes(&p, end, &tmp_uint, sizeof(tmp_uint))) {
		CERROR("Fail to read version\n");
		return GSS_S_FAILURE;
	}

	/* only support 0, 1 for the moment */
	if (tmp_uint > 2) {
		CERROR("Invalid version %u\n", tmp_uint);
		return GSS_S_FAILURE;
	}

	OBD_ALLOC_PTR(kctx);
	if (!kctx)
		return GSS_S_FAILURE;

	if (tmp_uint == 0 || tmp_uint == 1) {
		kctx->kc_initiate = tmp_uint;
		rc = import_context_rfc1964(kctx, p, end);
	} else {
		rc = import_context_rfc4121(kctx, p, end);
	}

	if (rc == 0)
		rc = krb5_init_keys(kctx);

	if (rc) {
		delete_context_kerberos(kctx);
		OBD_FREE_PTR(kctx);

		return GSS_S_FAILURE;
	}

	gctx->internal_ctx_id = kctx;
	return GSS_S_COMPLETE;
}

static
__u32 gss_copy_reverse_context_kerberos(struct gss_ctx *gctx,
					struct gss_ctx *gctx_new)
{
	struct krb5_ctx *kctx = gctx->internal_ctx_id;
	struct krb5_ctx *knew;

	OBD_ALLOC_PTR(knew);
	if (!knew)
		return GSS_S_FAILURE;

	knew->kc_initiate = kctx->kc_initiate ? 0 : 1;
	knew->kc_cfx = kctx->kc_cfx;
	knew->kc_seed_init = kctx->kc_seed_init;
	knew->kc_have_acceptor_subkey = kctx->kc_have_acceptor_subkey;
	knew->kc_endtime = kctx->kc_endtime;

	memcpy(knew->kc_seed, kctx->kc_seed, sizeof(kctx->kc_seed));
	knew->kc_seq_send = kctx->kc_seq_recv;
	knew->kc_seq_recv = kctx->kc_seq_send;
	knew->kc_enctype = kctx->kc_enctype;

	if (rawobj_dup(&knew->kc_mech_used, &kctx->kc_mech_used))
		goto out_err;

	if (keyblock_dup(&knew->kc_keye, &kctx->kc_keye))
		goto out_err;
	if (keyblock_dup(&knew->kc_keyi, &kctx->kc_keyi))
		goto out_err;
	if (keyblock_dup(&knew->kc_keyc, &kctx->kc_keyc))
		goto out_err;
	if (krb5_init_keys(knew))
		goto out_err;

	gctx_new->internal_ctx_id = knew;
	CDEBUG(D_SEC, "successfully copied reverse context\n");
	return GSS_S_COMPLETE;

out_err:
	delete_context_kerberos(knew);
	OBD_FREE_PTR(knew);
	return GSS_S_FAILURE;
}

static
__u32 gss_inquire_context_kerberos(struct gss_ctx *gctx,
				   unsigned long  *endtime)
{
	struct krb5_ctx *kctx = gctx->internal_ctx_id;

	*endtime = (unsigned long) ((__u32) kctx->kc_endtime);
	return GSS_S_COMPLETE;
}

static
void gss_delete_sec_context_kerberos(void *internal_ctx)
{
	struct krb5_ctx *kctx = internal_ctx;

	delete_context_kerberos(kctx);
	OBD_FREE_PTR(kctx);
}

static
void buf_to_sg(struct scatterlist *sg, void *ptr, int len)
{
	sg_set_buf(sg, ptr, len);
}

static
__u32 krb5_encrypt(struct crypto_blkcipher *tfm,
		   int decrypt,
		   void * iv,
		   void * in,
		   void * out,
		   int length)
{
	struct blkcipher_desc desc;
	struct scatterlist    sg;
	__u8 local_iv[16] = {0};
	__u32 ret = -EINVAL;

	LASSERT(tfm);
	desc.tfm  = tfm;
	desc.info = local_iv;
	desc.flags= 0;

	if (length % crypto_blkcipher_blocksize(tfm) != 0) {
		CERROR("output length %d mismatch blocksize %d\n",
		       length, crypto_blkcipher_blocksize(tfm));
		goto out;
	}

	if (crypto_blkcipher_ivsize(tfm) > 16) {
		CERROR("iv size too large %d\n", crypto_blkcipher_ivsize(tfm));
		goto out;
	}

	if (iv)
		memcpy(local_iv, iv, crypto_blkcipher_ivsize(tfm));

	memcpy(out, in, length);
	buf_to_sg(&sg, out, length);

	if (decrypt)
		ret = crypto_blkcipher_decrypt_iv(&desc, &sg, &sg, length);
	else
		ret = crypto_blkcipher_encrypt_iv(&desc, &sg, &sg, length);

out:
	return(ret);
}


static inline
int krb5_digest_hmac(struct crypto_hash *tfm,
		     rawobj_t *key,
		     struct krb5_header *khdr,
		     int msgcnt, rawobj_t *msgs,
		     int iovcnt, lnet_kiov_t *iovs,
		     rawobj_t *cksum)
{
	struct hash_desc   desc;
	struct scatterlist sg[1];
	int		i;

	crypto_hash_setkey(tfm, key->data, key->len);
	desc.tfm  = tfm;
	desc.flags= 0;

	crypto_hash_init(&desc);

	for (i = 0; i < msgcnt; i++) {
		if (msgs[i].len == 0)
			continue;
		buf_to_sg(sg, (char *) msgs[i].data, msgs[i].len);
		crypto_hash_update(&desc, sg, msgs[i].len);
	}

	for (i = 0; i < iovcnt; i++) {
		if (iovs[i].kiov_len == 0)
			continue;

		sg_set_page(&sg[0], iovs[i].kiov_page, iovs[i].kiov_len,
			    iovs[i].kiov_offset);
		crypto_hash_update(&desc, sg, iovs[i].kiov_len);
	}

	if (khdr) {
		buf_to_sg(sg, (char *) khdr, sizeof(*khdr));
		crypto_hash_update(&desc, sg, sizeof(*khdr));
	}

	return crypto_hash_final(&desc, cksum->data);
}


static inline
int krb5_digest_norm(struct crypto_hash *tfm,
		     struct krb5_keyblock *kb,
		     struct krb5_header *khdr,
		     int msgcnt, rawobj_t *msgs,
		     int iovcnt, lnet_kiov_t *iovs,
		     rawobj_t *cksum)
{
	struct hash_desc   desc;
	struct scatterlist sg[1];
	int		i;

	LASSERT(kb->kb_tfm);
	desc.tfm  = tfm;
	desc.flags= 0;

	crypto_hash_init(&desc);

	for (i = 0; i < msgcnt; i++) {
		if (msgs[i].len == 0)
			continue;
		buf_to_sg(sg, (char *) msgs[i].data, msgs[i].len);
		crypto_hash_update(&desc, sg, msgs[i].len);
	}

	for (i = 0; i < iovcnt; i++) {
		if (iovs[i].kiov_len == 0)
			continue;

		sg_set_page(&sg[0], iovs[i].kiov_page, iovs[i].kiov_len,
			    iovs[i].kiov_offset);
		crypto_hash_update(&desc, sg, iovs[i].kiov_len);
	}

	if (khdr) {
		buf_to_sg(sg, (char *) khdr, sizeof(*khdr));
		crypto_hash_update(&desc, sg, sizeof(*khdr));
	}

	crypto_hash_final(&desc, cksum->data);

	return krb5_encrypt(kb->kb_tfm, 0, NULL, cksum->data,
			    cksum->data, cksum->len);
}

/*
 * compute (keyed/keyless) checksum against the plain text which appended
 * with krb5 wire token header.
 */
static
__s32 krb5_make_checksum(__u32 enctype,
			 struct krb5_keyblock *kb,
			 struct krb5_header *khdr,
			 int msgcnt, rawobj_t *msgs,
			 int iovcnt, lnet_kiov_t *iovs,
			 rawobj_t *cksum)
{
	struct krb5_enctype   *ke = &enctypes[enctype];
	struct crypto_hash *tfm;
	__u32		  code = GSS_S_FAILURE;
	int		    rc;

	if (!(tfm = ll_crypto_alloc_hash(ke->ke_hash_name, 0, 0))) {
		CERROR("failed to alloc TFM: %s\n", ke->ke_hash_name);
		return GSS_S_FAILURE;
	}

	cksum->len = crypto_hash_digestsize(tfm);
	OBD_ALLOC_LARGE(cksum->data, cksum->len);
	if (!cksum->data) {
		cksum->len = 0;
		goto out_tfm;
	}

	if (ke->ke_hash_hmac)
		rc = krb5_digest_hmac(tfm, &kb->kb_key,
				      khdr, msgcnt, msgs, iovcnt, iovs, cksum);
	else
		rc = krb5_digest_norm(tfm, kb,
				      khdr, msgcnt, msgs, iovcnt, iovs, cksum);

	if (rc == 0)
		code = GSS_S_COMPLETE;
out_tfm:
	crypto_free_hash(tfm);
	return code;
}

static void fill_krb5_header(struct krb5_ctx *kctx,
			     struct krb5_header *khdr,
			     int privacy)
{
	unsigned char acceptor_flag;

	acceptor_flag = kctx->kc_initiate ? 0 : FLAG_SENDER_IS_ACCEPTOR;

	if (privacy) {
		khdr->kh_tok_id = cpu_to_be16(KG_TOK_WRAP_MSG);
		khdr->kh_flags = acceptor_flag | FLAG_WRAP_CONFIDENTIAL;
		khdr->kh_ec = cpu_to_be16(0);
		khdr->kh_rrc = cpu_to_be16(0);
	} else {
		khdr->kh_tok_id = cpu_to_be16(KG_TOK_MIC_MSG);
		khdr->kh_flags = acceptor_flag;
		khdr->kh_ec = cpu_to_be16(0xffff);
		khdr->kh_rrc = cpu_to_be16(0xffff);
	}

	khdr->kh_filler = 0xff;
	spin_lock(&krb5_seq_lock);
	khdr->kh_seq = cpu_to_be64(kctx->kc_seq_send++);
	spin_unlock(&krb5_seq_lock);
}

static __u32 verify_krb5_header(struct krb5_ctx *kctx,
				struct krb5_header *khdr,
				int privacy)
{
	unsigned char acceptor_flag;
	__u16	 tok_id, ec_rrc;

	acceptor_flag = kctx->kc_initiate ? FLAG_SENDER_IS_ACCEPTOR : 0;

	if (privacy) {
		tok_id = KG_TOK_WRAP_MSG;
		ec_rrc = 0x0;
	} else {
		tok_id = KG_TOK_MIC_MSG;
		ec_rrc = 0xffff;
	}

	/* sanity checks */
	if (be16_to_cpu(khdr->kh_tok_id) != tok_id) {
		CERROR("bad token id\n");
		return GSS_S_DEFECTIVE_TOKEN;
	}
	if ((khdr->kh_flags & FLAG_SENDER_IS_ACCEPTOR) != acceptor_flag) {
		CERROR("bad direction flag\n");
		return GSS_S_BAD_SIG;
	}
	if (privacy && (khdr->kh_flags & FLAG_WRAP_CONFIDENTIAL) == 0) {
		CERROR("missing confidential flag\n");
		return GSS_S_BAD_SIG;
	}
	if (khdr->kh_filler != 0xff) {
		CERROR("bad filler\n");
		return GSS_S_DEFECTIVE_TOKEN;
	}
	if (be16_to_cpu(khdr->kh_ec) != ec_rrc ||
	    be16_to_cpu(khdr->kh_rrc) != ec_rrc) {
		CERROR("bad EC or RRC\n");
		return GSS_S_DEFECTIVE_TOKEN;
	}
	return GSS_S_COMPLETE;
}

static
__u32 gss_get_mic_kerberos(struct gss_ctx *gctx,
			   int msgcnt,
			   rawobj_t *msgs,
			   int iovcnt,
			   lnet_kiov_t *iovs,
			   rawobj_t *token)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	rawobj_t	     cksum = RAWOBJ_EMPTY;

	/* fill krb5 header */
	LASSERT(token->len >= sizeof(*khdr));
	khdr = (struct krb5_header *) token->data;
	fill_krb5_header(kctx, khdr, 0);

	/* checksum */
	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyc,
			       khdr, msgcnt, msgs, iovcnt, iovs, &cksum))
		return GSS_S_FAILURE;

	LASSERT(cksum.len >= ke->ke_hash_size);
	LASSERT(token->len >= sizeof(*khdr) + ke->ke_hash_size);
	memcpy(khdr + 1, cksum.data + cksum.len - ke->ke_hash_size,
	       ke->ke_hash_size);

	token->len = sizeof(*khdr) + ke->ke_hash_size;
	rawobj_free(&cksum);
	return GSS_S_COMPLETE;
}

static
__u32 gss_verify_mic_kerberos(struct gss_ctx *gctx,
			      int msgcnt,
			      rawobj_t *msgs,
			      int iovcnt,
			      lnet_kiov_t *iovs,
			      rawobj_t *token)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	rawobj_t	     cksum = RAWOBJ_EMPTY;
	__u32		major;

	if (token->len < sizeof(*khdr)) {
		CERROR("short signature: %u\n", token->len);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	khdr = (struct krb5_header *) token->data;

	major = verify_krb5_header(kctx, khdr, 0);
	if (major != GSS_S_COMPLETE) {
		CERROR("bad krb5 header\n");
		return major;
	}

	if (token->len < sizeof(*khdr) + ke->ke_hash_size) {
		CERROR("short signature: %u, require %d\n",
		       token->len, (int) sizeof(*khdr) + ke->ke_hash_size);
		return GSS_S_FAILURE;
	}

	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyc,
			       khdr, msgcnt, msgs, iovcnt, iovs, &cksum)) {
		CERROR("failed to make checksum\n");
		return GSS_S_FAILURE;
	}

	LASSERT(cksum.len >= ke->ke_hash_size);
	if (memcmp(khdr + 1, cksum.data + cksum.len - ke->ke_hash_size,
		   ke->ke_hash_size)) {
		CERROR("checksum mismatch\n");
		rawobj_free(&cksum);
		return GSS_S_BAD_SIG;
	}

	rawobj_free(&cksum);
	return GSS_S_COMPLETE;
}

static
int add_padding(rawobj_t *msg, int msg_buflen, int blocksize)
{
	int padding;

	padding = (blocksize - (msg->len & (blocksize - 1))) &
		  (blocksize - 1);
	if (!padding)
		return 0;

	if (msg->len + padding > msg_buflen) {
		CERROR("bufsize %u too small: datalen %u, padding %u\n",
			msg_buflen, msg->len, padding);
		return -EINVAL;
	}

	memset(msg->data + msg->len, padding, padding);
	msg->len += padding;
	return 0;
}

static
int krb5_encrypt_rawobjs(struct crypto_blkcipher *tfm,
			 int mode_ecb,
			 int inobj_cnt,
			 rawobj_t *inobjs,
			 rawobj_t *outobj,
			 int enc)
{
	struct blkcipher_desc desc;
	struct scatterlist    src, dst;
	__u8		  local_iv[16] = {0}, *buf;
	__u32		 datalen = 0;
	int		   i, rc;

	buf = outobj->data;
	desc.tfm  = tfm;
	desc.info = local_iv;
	desc.flags = 0;

	for (i = 0; i < inobj_cnt; i++) {
		LASSERT(buf + inobjs[i].len <= outobj->data + outobj->len);

		buf_to_sg(&src, inobjs[i].data, inobjs[i].len);
		buf_to_sg(&dst, buf, outobj->len - datalen);

		if (mode_ecb) {
			if (enc)
				rc = crypto_blkcipher_encrypt(
					&desc, &dst, &src, src.length);
			else
				rc = crypto_blkcipher_decrypt(
					&desc, &dst, &src, src.length);
		} else {
			if (enc)
				rc = crypto_blkcipher_encrypt_iv(
					&desc, &dst, &src, src.length);
			else
				rc = crypto_blkcipher_decrypt_iv(
					&desc, &dst, &src, src.length);
		}

		if (rc) {
			CERROR("encrypt error %d\n", rc);
			return rc;
		}

		datalen += inobjs[i].len;
		buf += inobjs[i].len;
	}

	outobj->len = datalen;
	return 0;
}

/*
 * if adj_nob != 0, we adjust desc->bd_nob to the actual cipher text size.
 */
static
int krb5_encrypt_bulk(struct crypto_blkcipher *tfm,
		      struct krb5_header *khdr,
		      char *confounder,
		      struct ptlrpc_bulk_desc *desc,
		      rawobj_t *cipher,
		      int adj_nob)
{
	struct blkcipher_desc   ciph_desc;
	__u8		    local_iv[16] = {0};
	struct scatterlist      src, dst;
	int		     blocksize, i, rc, nob = 0;

	LASSERT(desc->bd_iov_count);
	LASSERT(desc->bd_enc_iov);

	blocksize = crypto_blkcipher_blocksize(tfm);
	LASSERT(blocksize > 1);
	LASSERT(cipher->len == blocksize + sizeof(*khdr));

	ciph_desc.tfm  = tfm;
	ciph_desc.info = local_iv;
	ciph_desc.flags = 0;

	/* encrypt confounder */
	buf_to_sg(&src, confounder, blocksize);
	buf_to_sg(&dst, cipher->data, blocksize);

	rc = crypto_blkcipher_encrypt_iv(&ciph_desc, &dst, &src, blocksize);
	if (rc) {
		CERROR("error to encrypt confounder: %d\n", rc);
		return rc;
	}

	/* encrypt clear pages */
	for (i = 0; i < desc->bd_iov_count; i++) {
		sg_set_page(&src, desc->bd_iov[i].kiov_page,
			    (desc->bd_iov[i].kiov_len + blocksize - 1) &
			    (~(blocksize - 1)),
			    desc->bd_iov[i].kiov_offset);
		if (adj_nob)
			nob += src.length;
		sg_set_page(&dst, desc->bd_enc_iov[i].kiov_page, src.length,
			    src.offset);

		desc->bd_enc_iov[i].kiov_offset = dst.offset;
		desc->bd_enc_iov[i].kiov_len = dst.length;

		rc = crypto_blkcipher_encrypt_iv(&ciph_desc, &dst, &src,
						    src.length);
		if (rc) {
			CERROR("error to encrypt page: %d\n", rc);
			return rc;
		}
	}

	/* encrypt krb5 header */
	buf_to_sg(&src, khdr, sizeof(*khdr));
	buf_to_sg(&dst, cipher->data + blocksize, sizeof(*khdr));

	rc = crypto_blkcipher_encrypt_iv(&ciph_desc,
					    &dst, &src, sizeof(*khdr));
	if (rc) {
		CERROR("error to encrypt krb5 header: %d\n", rc);
		return rc;
	}

	if (adj_nob)
		desc->bd_nob = nob;

	return 0;
}

/*
 * desc->bd_nob_transferred is the size of cipher text received.
 * desc->bd_nob is the target size of plain text supposed to be.
 *
 * if adj_nob != 0, we adjust each page's kiov_len to the actual
 * plain text size.
 * - for client read: we don't know data size for each page, so
 *   bd_iov[]->kiov_len is set to PAGE_SIZE, but actual data received might
 *   be smaller, so we need to adjust it according to bd_enc_iov[]->kiov_len.
 *   this means we DO NOT support the situation that server send an odd size
 *   data in a page which is not the last one.
 * - for server write: we knows exactly data size for each page being expected,
 *   thus kiov_len is accurate already, so we should not adjust it at all.
 *   and bd_enc_iov[]->kiov_len should be round_up(bd_iov[]->kiov_len) which
 *   should have been done by prep_bulk().
 */
static
int krb5_decrypt_bulk(struct crypto_blkcipher *tfm,
		      struct krb5_header *khdr,
		      struct ptlrpc_bulk_desc *desc,
		      rawobj_t *cipher,
		      rawobj_t *plain,
		      int adj_nob)
{
	struct blkcipher_desc   ciph_desc;
	__u8		    local_iv[16] = {0};
	struct scatterlist      src, dst;
	int		     ct_nob = 0, pt_nob = 0;
	int		     blocksize, i, rc;

	LASSERT(desc->bd_iov_count);
	LASSERT(desc->bd_enc_iov);
	LASSERT(desc->bd_nob_transferred);

	blocksize = crypto_blkcipher_blocksize(tfm);
	LASSERT(blocksize > 1);
	LASSERT(cipher->len == blocksize + sizeof(*khdr));

	ciph_desc.tfm  = tfm;
	ciph_desc.info = local_iv;
	ciph_desc.flags = 0;

	if (desc->bd_nob_transferred % blocksize) {
		CERROR("odd transferred nob: %d\n", desc->bd_nob_transferred);
		return -EPROTO;
	}

	/* decrypt head (confounder) */
	buf_to_sg(&src, cipher->data, blocksize);
	buf_to_sg(&dst, plain->data, blocksize);

	rc = crypto_blkcipher_decrypt_iv(&ciph_desc, &dst, &src, blocksize);
	if (rc) {
		CERROR("error to decrypt confounder: %d\n", rc);
		return rc;
	}

	for (i = 0; i < desc->bd_iov_count && ct_nob < desc->bd_nob_transferred;
	     i++) {
		if (desc->bd_enc_iov[i].kiov_offset % blocksize != 0 ||
		    desc->bd_enc_iov[i].kiov_len % blocksize != 0) {
			CERROR("page %d: odd offset %u len %u, blocksize %d\n",
			       i, desc->bd_enc_iov[i].kiov_offset,
			       desc->bd_enc_iov[i].kiov_len, blocksize);
			return -EFAULT;
		}

		if (adj_nob) {
			if (ct_nob + desc->bd_enc_iov[i].kiov_len >
			    desc->bd_nob_transferred)
				desc->bd_enc_iov[i].kiov_len =
					desc->bd_nob_transferred - ct_nob;

			desc->bd_iov[i].kiov_len = desc->bd_enc_iov[i].kiov_len;
			if (pt_nob + desc->bd_enc_iov[i].kiov_len >desc->bd_nob)
				desc->bd_iov[i].kiov_len = desc->bd_nob -pt_nob;
		} else {
			/* this should be guaranteed by LNET */
			LASSERT(ct_nob + desc->bd_enc_iov[i].kiov_len <=
				desc->bd_nob_transferred);
			LASSERT(desc->bd_iov[i].kiov_len <=
				desc->bd_enc_iov[i].kiov_len);
		}

		if (desc->bd_enc_iov[i].kiov_len == 0)
			continue;

		sg_set_page(&src, desc->bd_enc_iov[i].kiov_page,
			    desc->bd_enc_iov[i].kiov_len,
			    desc->bd_enc_iov[i].kiov_offset);
		dst = src;
		if (desc->bd_iov[i].kiov_len % blocksize == 0)
			sg_assign_page(&dst, desc->bd_iov[i].kiov_page);

		rc = crypto_blkcipher_decrypt_iv(&ciph_desc, &dst, &src,
						    src.length);
		if (rc) {
			CERROR("error to decrypt page: %d\n", rc);
			return rc;
		}

		if (desc->bd_iov[i].kiov_len % blocksize != 0) {
			memcpy(page_address(desc->bd_iov[i].kiov_page) +
			       desc->bd_iov[i].kiov_offset,
			       page_address(desc->bd_enc_iov[i].kiov_page) +
			       desc->bd_iov[i].kiov_offset,
			       desc->bd_iov[i].kiov_len);
		}

		ct_nob += desc->bd_enc_iov[i].kiov_len;
		pt_nob += desc->bd_iov[i].kiov_len;
	}

	if (unlikely(ct_nob != desc->bd_nob_transferred)) {
		CERROR("%d cipher text transferred but only %d decrypted\n",
		       desc->bd_nob_transferred, ct_nob);
		return -EFAULT;
	}

	if (unlikely(!adj_nob && pt_nob != desc->bd_nob)) {
		CERROR("%d plain text expected but only %d received\n",
		       desc->bd_nob, pt_nob);
		return -EFAULT;
	}

	/* if needed, clear up the rest unused iovs */
	if (adj_nob)
		while (i < desc->bd_iov_count)
			desc->bd_iov[i++].kiov_len = 0;

	/* decrypt tail (krb5 header) */
	buf_to_sg(&src, cipher->data + blocksize, sizeof(*khdr));
	buf_to_sg(&dst, cipher->data + blocksize, sizeof(*khdr));

	rc = crypto_blkcipher_decrypt_iv(&ciph_desc,
					    &dst, &src, sizeof(*khdr));
	if (rc) {
		CERROR("error to decrypt tail: %d\n", rc);
		return rc;
	}

	if (memcmp(cipher->data + blocksize, khdr, sizeof(*khdr))) {
		CERROR("krb5 header doesn't match\n");
		return -EACCES;
	}

	return 0;
}

static
__u32 gss_wrap_kerberos(struct gss_ctx *gctx,
			rawobj_t *gsshdr,
			rawobj_t *msg,
			int msg_buflen,
			rawobj_t *token)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	int		  blocksize;
	rawobj_t	     cksum = RAWOBJ_EMPTY;
	rawobj_t	     data_desc[3], cipher;
	__u8		 conf[GSS_MAX_CIPHER_BLOCK];
	int		  rc = 0;

	LASSERT(ke);
	LASSERT(ke->ke_conf_size <= GSS_MAX_CIPHER_BLOCK);
	LASSERT(kctx->kc_keye.kb_tfm == NULL ||
		ke->ke_conf_size >=
		crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm));

	/*
	 * final token format:
	 * ---------------------------------------------------
	 * | krb5 header | cipher text | checksum (16 bytes) |
	 * ---------------------------------------------------
	 */

	/* fill krb5 header */
	LASSERT(token->len >= sizeof(*khdr));
	khdr = (struct krb5_header *) token->data;
	fill_krb5_header(kctx, khdr, 1);

	/* generate confounder */
	cfs_get_random_bytes(conf, ke->ke_conf_size);

	/* get encryption blocksize. note kc_keye might not associated with
	 * a tfm, currently only for arcfour-hmac */
	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		LASSERT(kctx->kc_keye.kb_tfm == NULL);
		blocksize = 1;
	} else {
		LASSERT(kctx->kc_keye.kb_tfm);
		blocksize = crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm);
	}
	LASSERT(blocksize <= ke->ke_conf_size);

	/* padding the message */
	if (add_padding(msg, msg_buflen, blocksize))
		return GSS_S_FAILURE;

	/*
	 * clear text layout for checksum:
	 * ------------------------------------------------------
	 * | confounder | gss header | clear msgs | krb5 header |
	 * ------------------------------------------------------
	 */
	data_desc[0].data = conf;
	data_desc[0].len = ke->ke_conf_size;
	data_desc[1].data = gsshdr->data;
	data_desc[1].len = gsshdr->len;
	data_desc[2].data = msg->data;
	data_desc[2].len = msg->len;

	/* compute checksum */
	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyi,
			       khdr, 3, data_desc, 0, NULL, &cksum))
		return GSS_S_FAILURE;
	LASSERT(cksum.len >= ke->ke_hash_size);

	/*
	 * clear text layout for encryption:
	 * -----------------------------------------
	 * | confounder | clear msgs | krb5 header |
	 * -----------------------------------------
	 */
	data_desc[0].data = conf;
	data_desc[0].len = ke->ke_conf_size;
	data_desc[1].data = msg->data;
	data_desc[1].len = msg->len;
	data_desc[2].data = (__u8 *) khdr;
	data_desc[2].len = sizeof(*khdr);

	/* cipher text will be directly inplace */
	cipher.data = (__u8 *) (khdr + 1);
	cipher.len = token->len - sizeof(*khdr);
	LASSERT(cipher.len >= ke->ke_conf_size + msg->len + sizeof(*khdr));

	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		rawobj_t		 arc4_keye;
		struct crypto_blkcipher *arc4_tfm;

		if (krb5_make_checksum(ENCTYPE_ARCFOUR_HMAC, &kctx->kc_keyi,
				       NULL, 1, &cksum, 0, NULL, &arc4_keye)) {
			CERROR("failed to obtain arc4 enc key\n");
			GOTO(arc4_out, rc = -EACCES);
		}

		arc4_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 0);
		if (IS_ERR(arc4_tfm)) {
			CERROR("failed to alloc tfm arc4 in ECB mode\n");
			GOTO(arc4_out_key, rc = -EACCES);
		}

		if (crypto_blkcipher_setkey(arc4_tfm, arc4_keye.data,
					       arc4_keye.len)) {
			CERROR("failed to set arc4 key, len %d\n",
			       arc4_keye.len);
			GOTO(arc4_out_tfm, rc = -EACCES);
		}

		rc = krb5_encrypt_rawobjs(arc4_tfm, 1,
					  3, data_desc, &cipher, 1);
arc4_out_tfm:
		crypto_free_blkcipher(arc4_tfm);
arc4_out_key:
		rawobj_free(&arc4_keye);
arc4_out:
		do {} while (0); /* just to avoid compile warning */
	} else {
		rc = krb5_encrypt_rawobjs(kctx->kc_keye.kb_tfm, 0,
					  3, data_desc, &cipher, 1);
	}

	if (rc != 0) {
		rawobj_free(&cksum);
		return GSS_S_FAILURE;
	}

	/* fill in checksum */
	LASSERT(token->len >= sizeof(*khdr) + cipher.len + ke->ke_hash_size);
	memcpy((char *)(khdr + 1) + cipher.len,
	       cksum.data + cksum.len - ke->ke_hash_size,
	       ke->ke_hash_size);
	rawobj_free(&cksum);

	/* final token length */
	token->len = sizeof(*khdr) + cipher.len + ke->ke_hash_size;
	return GSS_S_COMPLETE;
}

static
__u32 gss_prep_bulk_kerberos(struct gss_ctx *gctx,
			     struct ptlrpc_bulk_desc *desc)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	int		  blocksize, i;

	LASSERT(desc->bd_iov_count);
	LASSERT(desc->bd_enc_iov);
	LASSERT(kctx->kc_keye.kb_tfm);

	blocksize = crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm);

	for (i = 0; i < desc->bd_iov_count; i++) {
		LASSERT(desc->bd_enc_iov[i].kiov_page);
		/*
		 * offset should always start at page boundary of either
		 * client or server side.
		 */
		if (desc->bd_iov[i].kiov_offset & blocksize) {
			CERROR("odd offset %d in page %d\n",
			       desc->bd_iov[i].kiov_offset, i);
			return GSS_S_FAILURE;
		}

		desc->bd_enc_iov[i].kiov_offset = desc->bd_iov[i].kiov_offset;
		desc->bd_enc_iov[i].kiov_len = (desc->bd_iov[i].kiov_len +
						blocksize - 1) & (~(blocksize - 1));
	}

	return GSS_S_COMPLETE;
}

static
__u32 gss_wrap_bulk_kerberos(struct gss_ctx *gctx,
			     struct ptlrpc_bulk_desc *desc,
			     rawobj_t *token, int adj_nob)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	int		  blocksize;
	rawobj_t	     cksum = RAWOBJ_EMPTY;
	rawobj_t	     data_desc[1], cipher;
	__u8		 conf[GSS_MAX_CIPHER_BLOCK];
	int		  rc = 0;

	LASSERT(ke);
	LASSERT(ke->ke_conf_size <= GSS_MAX_CIPHER_BLOCK);

	/*
	 * final token format:
	 * --------------------------------------------------
	 * | krb5 header | head/tail cipher text | checksum |
	 * --------------------------------------------------
	 */

	/* fill krb5 header */
	LASSERT(token->len >= sizeof(*khdr));
	khdr = (struct krb5_header *) token->data;
	fill_krb5_header(kctx, khdr, 1);

	/* generate confounder */
	cfs_get_random_bytes(conf, ke->ke_conf_size);

	/* get encryption blocksize. note kc_keye might not associated with
	 * a tfm, currently only for arcfour-hmac */
	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		LASSERT(kctx->kc_keye.kb_tfm == NULL);
		blocksize = 1;
	} else {
		LASSERT(kctx->kc_keye.kb_tfm);
		blocksize = crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm);
	}

	/*
	 * we assume the size of krb5_header (16 bytes) must be n * blocksize.
	 * the bulk token size would be exactly (sizeof(krb5_header) +
	 * blocksize + sizeof(krb5_header) + hashsize)
	 */
	LASSERT(blocksize <= ke->ke_conf_size);
	LASSERT(sizeof(*khdr) >= blocksize && sizeof(*khdr) % blocksize == 0);
	LASSERT(token->len >= sizeof(*khdr) + blocksize + sizeof(*khdr) + 16);

	/*
	 * clear text layout for checksum:
	 * ------------------------------------------
	 * | confounder | clear pages | krb5 header |
	 * ------------------------------------------
	 */
	data_desc[0].data = conf;
	data_desc[0].len = ke->ke_conf_size;

	/* compute checksum */
	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyi,
			       khdr, 1, data_desc,
			       desc->bd_iov_count, desc->bd_iov,
			       &cksum))
		return GSS_S_FAILURE;
	LASSERT(cksum.len >= ke->ke_hash_size);

	/*
	 * clear text layout for encryption:
	 * ------------------------------------------
	 * | confounder | clear pages | krb5 header |
	 * ------------------------------------------
	 *	|	      |	     |
	 *	----------  (cipher pages)   |
	 * result token:   |		   |
	 * -------------------------------------------
	 * | krb5 header | cipher text | cipher text |
	 * -------------------------------------------
	 */
	data_desc[0].data = conf;
	data_desc[0].len = ke->ke_conf_size;

	cipher.data = (__u8 *) (khdr + 1);
	cipher.len = blocksize + sizeof(*khdr);

	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		LBUG();
		rc = 0;
	} else {
		rc = krb5_encrypt_bulk(kctx->kc_keye.kb_tfm, khdr,
				       conf, desc, &cipher, adj_nob);
	}

	if (rc != 0) {
		rawobj_free(&cksum);
		return GSS_S_FAILURE;
	}

	/* fill in checksum */
	LASSERT(token->len >= sizeof(*khdr) + cipher.len + ke->ke_hash_size);
	memcpy((char *)(khdr + 1) + cipher.len,
	       cksum.data + cksum.len - ke->ke_hash_size,
	       ke->ke_hash_size);
	rawobj_free(&cksum);

	/* final token length */
	token->len = sizeof(*khdr) + cipher.len + ke->ke_hash_size;
	return GSS_S_COMPLETE;
}

static
__u32 gss_unwrap_kerberos(struct gss_ctx  *gctx,
			  rawobj_t	*gsshdr,
			  rawobj_t	*token,
			  rawobj_t	*msg)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	unsigned char       *tmpbuf;
	int		  blocksize, bodysize;
	rawobj_t	     cksum = RAWOBJ_EMPTY;
	rawobj_t	     cipher_in, plain_out;
	rawobj_t	     hash_objs[3];
	int		  rc = 0;
	__u32		major;

	LASSERT(ke);

	if (token->len < sizeof(*khdr)) {
		CERROR("short signature: %u\n", token->len);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	khdr = (struct krb5_header *) token->data;

	major = verify_krb5_header(kctx, khdr, 1);
	if (major != GSS_S_COMPLETE) {
		CERROR("bad krb5 header\n");
		return major;
	}

	/* block size */
	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		LASSERT(kctx->kc_keye.kb_tfm == NULL);
		blocksize = 1;
	} else {
		LASSERT(kctx->kc_keye.kb_tfm);
		blocksize = crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm);
	}

	/* expected token layout:
	 * ----------------------------------------
	 * | krb5 header | cipher text | checksum |
	 * ----------------------------------------
	 */
	bodysize = token->len - sizeof(*khdr) - ke->ke_hash_size;

	if (bodysize % blocksize) {
		CERROR("odd bodysize %d\n", bodysize);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	if (bodysize <= ke->ke_conf_size + sizeof(*khdr)) {
		CERROR("incomplete token: bodysize %d\n", bodysize);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	if (msg->len < bodysize - ke->ke_conf_size - sizeof(*khdr)) {
		CERROR("buffer too small: %u, require %d\n",
		       msg->len, bodysize - ke->ke_conf_size);
		return GSS_S_FAILURE;
	}

	/* decrypting */
	OBD_ALLOC_LARGE(tmpbuf, bodysize);
	if (!tmpbuf)
		return GSS_S_FAILURE;

	major = GSS_S_FAILURE;

	cipher_in.data = (__u8 *) (khdr + 1);
	cipher_in.len = bodysize;
	plain_out.data = tmpbuf;
	plain_out.len = bodysize;

	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		rawobj_t		 arc4_keye;
		struct crypto_blkcipher *arc4_tfm;

		cksum.data = token->data + token->len - ke->ke_hash_size;
		cksum.len = ke->ke_hash_size;

		if (krb5_make_checksum(ENCTYPE_ARCFOUR_HMAC, &kctx->kc_keyi,
				       NULL, 1, &cksum, 0, NULL, &arc4_keye)) {
			CERROR("failed to obtain arc4 enc key\n");
			GOTO(arc4_out, rc = -EACCES);
		}

		arc4_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 0);
		if (IS_ERR(arc4_tfm)) {
			CERROR("failed to alloc tfm arc4 in ECB mode\n");
			GOTO(arc4_out_key, rc = -EACCES);
		}

		if (crypto_blkcipher_setkey(arc4_tfm,
					 arc4_keye.data, arc4_keye.len)) {
			CERROR("failed to set arc4 key, len %d\n",
			       arc4_keye.len);
			GOTO(arc4_out_tfm, rc = -EACCES);
		}

		rc = krb5_encrypt_rawobjs(arc4_tfm, 1,
					  1, &cipher_in, &plain_out, 0);
arc4_out_tfm:
		crypto_free_blkcipher(arc4_tfm);
arc4_out_key:
		rawobj_free(&arc4_keye);
arc4_out:
		cksum = RAWOBJ_EMPTY;
	} else {
		rc = krb5_encrypt_rawobjs(kctx->kc_keye.kb_tfm, 0,
					  1, &cipher_in, &plain_out, 0);
	}

	if (rc != 0) {
		CERROR("error decrypt\n");
		goto out_free;
	}
	LASSERT(plain_out.len == bodysize);

	/* expected clear text layout:
	 * -----------------------------------------
	 * | confounder | clear msgs | krb5 header |
	 * -----------------------------------------
	 */

	/* verify krb5 header in token is not modified */
	if (memcmp(khdr, plain_out.data + plain_out.len - sizeof(*khdr),
		   sizeof(*khdr))) {
		CERROR("decrypted krb5 header mismatch\n");
		goto out_free;
	}

	/* verify checksum, compose clear text as layout:
	 * ------------------------------------------------------
	 * | confounder | gss header | clear msgs | krb5 header |
	 * ------------------------------------------------------
	 */
	hash_objs[0].len = ke->ke_conf_size;
	hash_objs[0].data = plain_out.data;
	hash_objs[1].len = gsshdr->len;
	hash_objs[1].data = gsshdr->data;
	hash_objs[2].len = plain_out.len - ke->ke_conf_size - sizeof(*khdr);
	hash_objs[2].data = plain_out.data + ke->ke_conf_size;
	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyi,
			       khdr, 3, hash_objs, 0, NULL, &cksum))
		goto out_free;

	LASSERT(cksum.len >= ke->ke_hash_size);
	if (memcmp((char *)(khdr + 1) + bodysize,
		   cksum.data + cksum.len - ke->ke_hash_size,
		   ke->ke_hash_size)) {
		CERROR("checksum mismatch\n");
		goto out_free;
	}

	msg->len =  bodysize - ke->ke_conf_size - sizeof(*khdr);
	memcpy(msg->data, tmpbuf + ke->ke_conf_size, msg->len);

	major = GSS_S_COMPLETE;
out_free:
	OBD_FREE_LARGE(tmpbuf, bodysize);
	rawobj_free(&cksum);
	return major;
}

static
__u32 gss_unwrap_bulk_kerberos(struct gss_ctx *gctx,
			       struct ptlrpc_bulk_desc *desc,
			       rawobj_t *token, int adj_nob)
{
	struct krb5_ctx     *kctx = gctx->internal_ctx_id;
	struct krb5_enctype *ke = &enctypes[kctx->kc_enctype];
	struct krb5_header  *khdr;
	int		  blocksize;
	rawobj_t	     cksum = RAWOBJ_EMPTY;
	rawobj_t	     cipher, plain;
	rawobj_t	     data_desc[1];
	int		  rc;
	__u32		major;

	LASSERT(ke);

	if (token->len < sizeof(*khdr)) {
		CERROR("short signature: %u\n", token->len);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	khdr = (struct krb5_header *) token->data;

	major = verify_krb5_header(kctx, khdr, 1);
	if (major != GSS_S_COMPLETE) {
		CERROR("bad krb5 header\n");
		return major;
	}

	/* block size */
	if (kctx->kc_enctype == ENCTYPE_ARCFOUR_HMAC) {
		LASSERT(kctx->kc_keye.kb_tfm == NULL);
		blocksize = 1;
		LBUG();
	} else {
		LASSERT(kctx->kc_keye.kb_tfm);
		blocksize = crypto_blkcipher_blocksize(kctx->kc_keye.kb_tfm);
	}
	LASSERT(sizeof(*khdr) >= blocksize && sizeof(*khdr) % blocksize == 0);

	/*
	 * token format is expected as:
	 * -----------------------------------------------
	 * | krb5 header | head/tail cipher text | cksum |
	 * -----------------------------------------------
	 */
	if (token->len < sizeof(*khdr) + blocksize + sizeof(*khdr) +
			 ke->ke_hash_size) {
		CERROR("short token size: %u\n", token->len);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	cipher.data = (__u8 *) (khdr + 1);
	cipher.len = blocksize + sizeof(*khdr);
	plain.data = cipher.data;
	plain.len = cipher.len;

	rc = krb5_decrypt_bulk(kctx->kc_keye.kb_tfm, khdr,
			       desc, &cipher, &plain, adj_nob);
	if (rc)
		return GSS_S_DEFECTIVE_TOKEN;

	/*
	 * verify checksum, compose clear text as layout:
	 * ------------------------------------------
	 * | confounder | clear pages | krb5 header |
	 * ------------------------------------------
	 */
	data_desc[0].data = plain.data;
	data_desc[0].len = blocksize;

	if (krb5_make_checksum(kctx->kc_enctype, &kctx->kc_keyi,
			       khdr, 1, data_desc,
			       desc->bd_iov_count, desc->bd_iov,
			       &cksum))
		return GSS_S_FAILURE;
	LASSERT(cksum.len >= ke->ke_hash_size);

	if (memcmp(plain.data + blocksize + sizeof(*khdr),
		   cksum.data + cksum.len - ke->ke_hash_size,
		   ke->ke_hash_size)) {
		CERROR("checksum mismatch\n");
		rawobj_free(&cksum);
		return GSS_S_BAD_SIG;
	}

	rawobj_free(&cksum);
	return GSS_S_COMPLETE;
}

int gss_display_kerberos(struct gss_ctx	*ctx,
			 char		  *buf,
			 int		    bufsize)
{
	struct krb5_ctx    *kctx = ctx->internal_ctx_id;
	int		 written;

	written = snprintf(buf, bufsize, "krb5 (%s)",
			   enctype2str(kctx->kc_enctype));
	return written;
}

static struct gss_api_ops gss_kerberos_ops = {
	.gss_import_sec_context     = gss_import_sec_context_kerberos,
	.gss_copy_reverse_context   = gss_copy_reverse_context_kerberos,
	.gss_inquire_context	= gss_inquire_context_kerberos,
	.gss_get_mic		= gss_get_mic_kerberos,
	.gss_verify_mic	     = gss_verify_mic_kerberos,
	.gss_wrap		   = gss_wrap_kerberos,
	.gss_unwrap		 = gss_unwrap_kerberos,
	.gss_prep_bulk	      = gss_prep_bulk_kerberos,
	.gss_wrap_bulk	      = gss_wrap_bulk_kerberos,
	.gss_unwrap_bulk	    = gss_unwrap_bulk_kerberos,
	.gss_delete_sec_context     = gss_delete_sec_context_kerberos,
	.gss_display		= gss_display_kerberos,
};

static struct subflavor_desc gss_kerberos_sfs[] = {
	{
		.sf_subflavor   = SPTLRPC_SUBFLVR_KRB5N,
		.sf_qop	 = 0,
		.sf_service     = SPTLRPC_SVC_NULL,
		.sf_name	= "krb5n"
	},
	{
		.sf_subflavor   = SPTLRPC_SUBFLVR_KRB5A,
		.sf_qop	 = 0,
		.sf_service     = SPTLRPC_SVC_AUTH,
		.sf_name	= "krb5a"
	},
	{
		.sf_subflavor   = SPTLRPC_SUBFLVR_KRB5I,
		.sf_qop	 = 0,
		.sf_service     = SPTLRPC_SVC_INTG,
		.sf_name	= "krb5i"
	},
	{
		.sf_subflavor   = SPTLRPC_SUBFLVR_KRB5P,
		.sf_qop	 = 0,
		.sf_service     = SPTLRPC_SVC_PRIV,
		.sf_name	= "krb5p"
	},
};

/*
 * currently we leave module owner NULL
 */
static struct gss_api_mech gss_kerberos_mech = {
	.gm_owner       = NULL, /*THIS_MODULE, */
	.gm_name	= "krb5",
	.gm_oid	 = (rawobj_t)
				{9, "\052\206\110\206\367\022\001\002\002"},
	.gm_ops	 = &gss_kerberos_ops,
	.gm_sf_num      = 4,
	.gm_sfs	 = gss_kerberos_sfs,
};

int __init init_kerberos_module(void)
{
	int status;

	spin_lock_init(&krb5_seq_lock);

	status = lgss_mech_register(&gss_kerberos_mech);
	if (status)
		CERROR("Failed to register kerberos gss mechanism!\n");
	return status;
}

void __exit cleanup_kerberos_module(void)
{
	lgss_mech_unregister(&gss_kerberos_mech);
}