net/rxrpc/ar-key.c

/* RxRPC key management
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * RxRPC keys should have a description of describing their purpose:
 *	"afs@CAMBRIDGE.REDHAT.COM>
 */

#include <crypto/skcipher.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/key-type.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <keys/rxrpc-type.h>
#include <keys/user-type.h>
#include "ar-internal.h"

static int rxrpc_vet_description_s(const char *);
static int rxrpc_preparse(struct key_preparsed_payload *);
static int rxrpc_preparse_s(struct key_preparsed_payload *);
static void rxrpc_free_preparse(struct key_preparsed_payload *);
static void rxrpc_free_preparse_s(struct key_preparsed_payload *);
static void rxrpc_destroy(struct key *);
static void rxrpc_destroy_s(struct key *);
static void rxrpc_describe(const struct key *, struct seq_file *);
static long rxrpc_read(const struct key *, char __user *, size_t);

/*
 * rxrpc defined keys take an arbitrary string as the description and an
 * arbitrary blob of data as the payload
 */
struct key_type key_type_rxrpc = {
	.name		= "rxrpc",
	.preparse	= rxrpc_preparse,
	.free_preparse	= rxrpc_free_preparse,
	.instantiate	= generic_key_instantiate,
	.destroy	= rxrpc_destroy,
	.describe	= rxrpc_describe,
	.read		= rxrpc_read,
};
EXPORT_SYMBOL(key_type_rxrpc);

/*
 * rxrpc server defined keys take "<serviceId>:<securityIndex>" as the
 * description and an 8-byte decryption key as the payload
 */
struct key_type key_type_rxrpc_s = {
	.name		= "rxrpc_s",
	.vet_description = rxrpc_vet_description_s,
	.preparse	= rxrpc_preparse_s,
	.free_preparse	= rxrpc_free_preparse_s,
	.instantiate	= generic_key_instantiate,
	.destroy	= rxrpc_destroy_s,
	.describe	= rxrpc_describe,
};

/*
 * Vet the description for an RxRPC server key
 */
static int rxrpc_vet_description_s(const char *desc)
{
	unsigned long num;
	char *p;

	num = simple_strtoul(desc, &p, 10);
	if (*p != ':' || num > 65535)
		return -EINVAL;
	num = simple_strtoul(p + 1, &p, 10);
	if (*p || num < 1 || num > 255)
		return -EINVAL;
	return 0;
}

/*
 * parse an RxKAD type XDR format token
 * - the caller guarantees we have at least 4 words
 */
static int rxrpc_preparse_xdr_rxkad(struct key_preparsed_payload *prep,
				    size_t datalen,
				    const __be32 *xdr, unsigned int toklen)
{
	struct rxrpc_key_token *token, **pptoken;
	size_t plen;
	u32 tktlen;

	_enter(",{%x,%x,%x,%x},%u",
	       ntohl(xdr[0]), ntohl(xdr[1]), ntohl(xdr[2]), ntohl(xdr[3]),
	       toklen);

	if (toklen <= 8 * 4)
		return -EKEYREJECTED;
	tktlen = ntohl(xdr[7]);
	_debug("tktlen: %x", tktlen);
	if (tktlen > AFSTOKEN_RK_TIX_MAX)
		return -EKEYREJECTED;
	if (toklen < 8 * 4 + tktlen)
		return -EKEYREJECTED;

	plen = sizeof(*token) + sizeof(*token->kad) + tktlen;
	prep->quotalen = datalen + plen;

	plen -= sizeof(*token);
	token = kzalloc(sizeof(*token), GFP_KERNEL);
	if (!token)
		return -ENOMEM;

	token->kad = kzalloc(plen, GFP_KERNEL);
	if (!token->kad) {
		kfree(token);
		return -ENOMEM;
	}

	token->security_index	= RXRPC_SECURITY_RXKAD;
	token->kad->ticket_len	= tktlen;
	token->kad->vice_id	= ntohl(xdr[0]);
	token->kad->kvno	= ntohl(xdr[1]);
	token->kad->start	= ntohl(xdr[4]);
	token->kad->expiry	= ntohl(xdr[5]);
	token->kad->primary_flag = ntohl(xdr[6]);
	memcpy(&token->kad->session_key, &xdr[2], 8);
	memcpy(&token->kad->ticket, &xdr[8], tktlen);

	_debug("SCIX: %u", token->security_index);
	_debug("TLEN: %u", token->kad->ticket_len);
	_debug("EXPY: %x", token->kad->expiry);
	_debug("KVNO: %u", token->kad->kvno);
	_debug("PRIM: %u", token->kad->primary_flag);
	_debug("SKEY: %02x%02x%02x%02x%02x%02x%02x%02x",
	       token->kad->session_key[0], token->kad->session_key[1],
	       token->kad->session_key[2], token->kad->session_key[3],
	       token->kad->session_key[4], token->kad->session_key[5],
	       token->kad->session_key[6], token->kad->session_key[7]);
	if (token->kad->ticket_len >= 8)
		_debug("TCKT: %02x%02x%02x%02x%02x%02x%02x%02x",
		       token->kad->ticket[0], token->kad->ticket[1],
		       token->kad->ticket[2], token->kad->ticket[3],
		       token->kad->ticket[4], token->kad->ticket[5],
		       token->kad->ticket[6], token->kad->ticket[7]);

	/* count the number of tokens attached */
	prep->payload.data[1] = (void *)((unsigned long)prep->payload.data[1] + 1);

	/* attach the data */
	for (pptoken = (struct rxrpc_key_token **)&prep->payload.data[0];
	     *pptoken;
	     pptoken = &(*pptoken)->next)
		continue;
	*pptoken = token;
	if (token->kad->expiry < prep->expiry)
		prep->expiry = token->kad->expiry;

	_leave(" = 0");
	return 0;
}

static void rxrpc_free_krb5_principal(struct krb5_principal *princ)
{
	int loop;

	if (princ->name_parts) {
		for (loop = princ->n_name_parts - 1; loop >= 0; loop--)
			kfree(princ->name_parts[loop]);
		kfree(princ->name_parts);
	}
	kfree(princ->realm);
}

static void rxrpc_free_krb5_tagged(struct krb5_tagged_data *td)
{
	kfree(td->data);
}

/*
 * free up an RxK5 token
 */
static void rxrpc_rxk5_free(struct rxk5_key *rxk5)
{
	int loop;

	rxrpc_free_krb5_principal(&rxk5->client);
	rxrpc_free_krb5_principal(&rxk5->server);
	rxrpc_free_krb5_tagged(&rxk5->session);

	if (rxk5->addresses) {
		for (loop = rxk5->n_addresses - 1; loop >= 0; loop--)
			rxrpc_free_krb5_tagged(&rxk5->addresses[loop]);
		kfree(rxk5->addresses);
	}
	if (rxk5->authdata) {
		for (loop = rxk5->n_authdata - 1; loop >= 0; loop--)
			rxrpc_free_krb5_tagged(&rxk5->authdata[loop]);
		kfree(rxk5->authdata);
	}

	kfree(rxk5->ticket);
	kfree(rxk5->ticket2);
	kfree(rxk5);
}

/*
 * extract a krb5 principal
 */
static int rxrpc_krb5_decode_principal(struct krb5_principal *princ,
				       const __be32 **_xdr,
				       unsigned int *_toklen)
{
	const __be32 *xdr = *_xdr;
	unsigned int toklen = *_toklen, n_parts, loop, tmp;

	/* there must be at least one name, and at least #names+1 length
	 * words */
	if (toklen <= 12)
		return -EINVAL;

	_enter(",{%x,%x,%x},%u",
	       ntohl(xdr[0]), ntohl(xdr[1]), ntohl(xdr[2]), toklen);

	n_parts = ntohl(*xdr++);
	toklen -= 4;
	if (n_parts <= 0 || n_parts > AFSTOKEN_K5_COMPONENTS_MAX)
		return -EINVAL;
	princ->n_name_parts = n_parts;

	if (toklen <= (n_parts + 1) * 4)
		return -EINVAL;

	princ->name_parts = kcalloc(n_parts, sizeof(char *), GFP_KERNEL);
	if (!princ->name_parts)
		return -ENOMEM;

	for (loop = 0; loop < n_parts; loop++) {
		if (toklen < 4)
			return -EINVAL;
		tmp = ntohl(*xdr++);
		toklen -= 4;
		if (tmp <= 0 || tmp > AFSTOKEN_STRING_MAX)
			return -EINVAL;
		if (tmp > toklen)
			return -EINVAL;
		princ->name_parts[loop] = kmalloc(tmp + 1, GFP_KERNEL);
		if (!princ->name_parts[loop])
			return -ENOMEM;
		memcpy(princ->name_parts[loop], xdr, tmp);
		princ->name_parts[loop][tmp] = 0;
		tmp = (tmp + 3) & ~3;
		toklen -= tmp;
		xdr += tmp >> 2;
	}

	if (toklen < 4)
		return -EINVAL;
	tmp = ntohl(*xdr++);
	toklen -= 4;
	if (tmp <= 0 || tmp > AFSTOKEN_K5_REALM_MAX)
		return -EINVAL;
	if (tmp > toklen)
		return -EINVAL;
	princ->realm = kmalloc(tmp + 1, GFP_KERNEL);
	if (!princ->realm)
		return -ENOMEM;
	memcpy(princ->realm, xdr, tmp);
	princ->realm[tmp] = 0;
	tmp = (tmp + 3) & ~3;
	toklen -= tmp;
	xdr += tmp >> 2;

	_debug("%s/...@%s", princ->name_parts[0], princ->realm);

	*_xdr = xdr;
	*_toklen = toklen;
	_leave(" = 0 [toklen=%u]", toklen);
	return 0;
}

/*
 * extract a piece of krb5 tagged data
 */
static int rxrpc_krb5_decode_tagged_data(struct krb5_tagged_data *td,
					 size_t max_data_size,
					 const __be32 **_xdr,
					 unsigned int *_toklen)
{
	const __be32 *xdr = *_xdr;
	unsigned int toklen = *_toklen, len;

	/* there must be at least one tag and one length word */
	if (toklen <= 8)
		return -EINVAL;

	_enter(",%zu,{%x,%x},%u",
	       max_data_size, ntohl(xdr[0]), ntohl(xdr[1]), toklen);

	td->tag = ntohl(*xdr++);
	len = ntohl(*xdr++);
	toklen -= 8;
	if (len > max_data_size)
		return -EINVAL;
	td->data_len = len;

	if (len > 0) {
		td->data = kmemdup(xdr, len, GFP_KERNEL);
		if (!td->data)
			return -ENOMEM;
		len = (len + 3) & ~3;
		toklen -= len;
		xdr += len >> 2;
	}

	_debug("tag %x len %x", td->tag, td->data_len);

	*_xdr = xdr;
	*_toklen = toklen;
	_leave(" = 0 [toklen=%u]", toklen);
	return 0;
}

/*
 * extract an array of tagged data
 */
static int rxrpc_krb5_decode_tagged_array(struct krb5_tagged_data **_td,
					  u8 *_n_elem,
					  u8 max_n_elem,
					  size_t max_elem_size,
					  const __be32 **_xdr,
					  unsigned int *_toklen)
{
	struct krb5_tagged_data *td;
	const __be32 *xdr = *_xdr;
	unsigned int toklen = *_toklen, n_elem, loop;
	int ret;

	/* there must be at least one count */
	if (toklen < 4)
		return -EINVAL;

	_enter(",,%u,%zu,{%x},%u",
	       max_n_elem, max_elem_size, ntohl(xdr[0]), toklen);

	n_elem = ntohl(*xdr++);
	toklen -= 4;
	if (n_elem > max_n_elem)
		return -EINVAL;
	*_n_elem = n_elem;
	if (n_elem > 0) {
		if (toklen <= (n_elem + 1) * 4)
			return -EINVAL;

		_debug("n_elem %d", n_elem);

		td = kcalloc(n_elem, sizeof(struct krb5_tagged_data),
			     GFP_KERNEL);
		if (!td)
			return -ENOMEM;
		*_td = td;

		for (loop = 0; loop < n_elem; loop++) {
			ret = rxrpc_krb5_decode_tagged_data(&td[loop],
							    max_elem_size,
							    &xdr, &toklen);
			if (ret < 0)
				return ret;
		}
	}

	*_xdr = xdr;
	*_toklen = toklen;
	_leave(" = 0 [toklen=%u]", toklen);
	return 0;
}

/*
 * extract a krb5 ticket
 */
static int rxrpc_krb5_decode_ticket(u8 **_ticket, u16 *_tktlen,
				    const __be32 **_xdr, unsigned int *_toklen)
{
	const __be32 *xdr = *_xdr;
	unsigned int toklen = *_toklen, len;

	/* there must be at least one length word */
	if (toklen <= 4)
		return -EINVAL;

	_enter(",{%x},%u", ntohl(xdr[0]), toklen);

	len = ntohl(*xdr++);
	toklen -= 4;
	if (len > AFSTOKEN_K5_TIX_MAX)
		return -EINVAL;
	*_tktlen = len;

	_debug("ticket len %u", len);

	if (len > 0) {
		*_ticket = kmemdup(xdr, len, GFP_KERNEL);
		if (!*_ticket)
			return -ENOMEM;
		len = (len + 3) & ~3;
		toklen -= len;
		xdr += len >> 2;
	}

	*_xdr = xdr;
	*_toklen = toklen;
	_leave(" = 0 [toklen=%u]", toklen);
	return 0;
}

/*
 * parse an RxK5 type XDR format token
 * - the caller guarantees we have at least 4 words
 */
static int rxrpc_preparse_xdr_rxk5(struct key_preparsed_payload *prep,
				   size_t datalen,
				   const __be32 *xdr, unsigned int toklen)
{
	struct rxrpc_key_token *token, **pptoken;
	struct rxk5_key *rxk5;
	const __be32 *end_xdr = xdr + (toklen >> 2);
	int ret;

	_enter(",{%x,%x,%x,%x},%u",
	       ntohl(xdr[0]), ntohl(xdr[1]), ntohl(xdr[2]), ntohl(xdr[3]),
	       toklen);

	/* reserve some payload space for this subkey - the length of the token
	 * is a reasonable approximation */
	prep->quotalen = datalen + toklen;

	token = kzalloc(sizeof(*token), GFP_KERNEL);
	if (!token)
		return -ENOMEM;

	rxk5 = kzalloc(sizeof(*rxk5), GFP_KERNEL);
	if (!rxk5) {
		kfree(token);
		return -ENOMEM;
	}

	token->security_index = RXRPC_SECURITY_RXK5;
	token->k5 = rxk5;

	/* extract the principals */
	ret = rxrpc_krb5_decode_principal(&rxk5->client, &xdr, &toklen);
	if (ret < 0)
		goto error;
	ret = rxrpc_krb5_decode_principal(&rxk5->server, &xdr, &toklen);
	if (ret < 0)
		goto error;

	/* extract the session key and the encoding type (the tag field ->
	 * ENCTYPE_xxx) */
	ret = rxrpc_krb5_decode_tagged_data(&rxk5->session, AFSTOKEN_DATA_MAX,
					    &xdr, &toklen);
	if (ret < 0)
		goto error;

	if (toklen < 4 * 8 + 2 * 4)
		goto inval;
	rxk5->authtime	= be64_to_cpup((const __be64 *) xdr);
	xdr += 2;
	rxk5->starttime	= be64_to_cpup((const __be64 *) xdr);
	xdr += 2;
	rxk5->endtime	= be64_to_cpup((const __be64 *) xdr);
	xdr += 2;
	rxk5->renew_till = be64_to_cpup((const __be64 *) xdr);
	xdr += 2;
	rxk5->is_skey = ntohl(*xdr++);
	rxk5->flags = ntohl(*xdr++);
	toklen -= 4 * 8 + 2 * 4;

	_debug("times: a=%llx s=%llx e=%llx rt=%llx",
	       rxk5->authtime, rxk5->starttime, rxk5->endtime,
	       rxk5->renew_till);
	_debug("is_skey=%x flags=%x", rxk5->is_skey, rxk5->flags);

	/* extract the permitted client addresses */
	ret = rxrpc_krb5_decode_tagged_array(&rxk5->addresses,
					     &rxk5->n_addresses,
					     AFSTOKEN_K5_ADDRESSES_MAX,
					     AFSTOKEN_DATA_MAX,
					     &xdr, &toklen);
	if (ret < 0)
		goto error;

	ASSERTCMP((end_xdr - xdr) << 2, ==, toklen);

	/* extract the tickets */
	ret = rxrpc_krb5_decode_ticket(&rxk5->ticket, &rxk5->ticket_len,
				       &xdr, &toklen);
	if (ret < 0)
		goto error;
	ret = rxrpc_krb5_decode_ticket(&rxk5->ticket2, &rxk5->ticket2_len,
				       &xdr, &toklen);
	if (ret < 0)
		goto error;

	ASSERTCMP((end_xdr - xdr) << 2, ==, toklen);

	/* extract the typed auth data */
	ret = rxrpc_krb5_decode_tagged_array(&rxk5->authdata,
					     &rxk5->n_authdata,
					     AFSTOKEN_K5_AUTHDATA_MAX,
					     AFSTOKEN_BDATALN_MAX,
					     &xdr, &toklen);
	if (ret < 0)
		goto error;

	ASSERTCMP((end_xdr - xdr) << 2, ==, toklen);

	if (toklen != 0)
		goto inval;

	/* attach the payload */
	for (pptoken = (struct rxrpc_key_token **)&prep->payload.data[0];
	     *pptoken;
	     pptoken = &(*pptoken)->next)
		continue;
	*pptoken = token;
	if (token->kad->expiry < prep->expiry)
		prep->expiry = token->kad->expiry;

	_leave(" = 0");
	return 0;

inval:
	ret = -EINVAL;
error:
	rxrpc_rxk5_free(rxk5);
	kfree(token);
	_leave(" = %d", ret);
	return ret;
}

/*
 * attempt to parse the data as the XDR format
 * - the caller guarantees we have more than 7 words
 */
static int rxrpc_preparse_xdr(struct key_preparsed_payload *prep)
{
	const __be32 *xdr = prep->data, *token;
	const char *cp;
	unsigned int len, tmp, loop, ntoken, toklen, sec_ix;
	size_t datalen = prep->datalen;
	int ret;

	_enter(",{%x,%x,%x,%x},%zu",
	       ntohl(xdr[0]), ntohl(xdr[1]), ntohl(xdr[2]), ntohl(xdr[3]),
	       prep->datalen);

	if (datalen > AFSTOKEN_LENGTH_MAX)
		goto not_xdr;

	/* XDR is an array of __be32's */
	if (datalen & 3)
		goto not_xdr;

	/* the flags should be 0 (the setpag bit must be handled by
	 * userspace) */
	if (ntohl(*xdr++) != 0)
		goto not_xdr;
	datalen -= 4;

	/* check the cell name */
	len = ntohl(*xdr++);
	if (len < 1 || len > AFSTOKEN_CELL_MAX)
		goto not_xdr;
	datalen -= 4;
	tmp = (len + 3) & ~3;
	if (tmp > datalen)
		goto not_xdr;

	cp = (const char *) xdr;
	for (loop = 0; loop < len; loop++)
		if (!isprint(cp[loop]))
			goto not_xdr;
	if (len < tmp)
		for (; loop < tmp; loop++)
			if (cp[loop])
				goto not_xdr;
	_debug("cellname: [%u/%u] '%*.*s'",
	       len, tmp, len, len, (const char *) xdr);
	datalen -= tmp;
	xdr += tmp >> 2;

	/* get the token count */
	if (datalen < 12)
		goto not_xdr;
	ntoken = ntohl(*xdr++);
	datalen -= 4;
	_debug("ntoken: %x", ntoken);
	if (ntoken < 1 || ntoken > AFSTOKEN_MAX)
		goto not_xdr;

	/* check each token wrapper */
	token = xdr;
	loop = ntoken;
	do {
		if (datalen < 8)
			goto not_xdr;
		toklen = ntohl(*xdr++);
		sec_ix = ntohl(*xdr);
		datalen -= 4;
		_debug("token: [%x/%zx] %x", toklen, datalen, sec_ix);
		if (toklen < 20 || toklen > datalen)
			goto not_xdr;
		datalen -= (toklen + 3) & ~3;
		xdr += (toklen + 3) >> 2;

	} while (--loop > 0);

	_debug("remainder: %zu", datalen);
	if (datalen != 0)
		goto not_xdr;

	/* okay: we're going to assume it's valid XDR format
	 * - we ignore the cellname, relying on the key to be correctly named
	 */
	do {
		xdr = token;
		toklen = ntohl(*xdr++);
		token = xdr + ((toklen + 3) >> 2);
		sec_ix = ntohl(*xdr++);
		toklen -= 4;

		_debug("TOKEN type=%u [%p-%p]", sec_ix, xdr, token);

		switch (sec_ix) {
		case RXRPC_SECURITY_RXKAD:
			ret = rxrpc_preparse_xdr_rxkad(prep, datalen, xdr, toklen);
			if (ret != 0)
				goto error;
			break;

		case RXRPC_SECURITY_RXK5:
			ret = rxrpc_preparse_xdr_rxk5(prep, datalen, xdr, toklen);
			if (ret != 0)
				goto error;
			break;

		default:
			ret = -EPROTONOSUPPORT;
			goto error;
		}

	} while (--ntoken > 0);

	_leave(" = 0");
	return 0;

not_xdr:
	_leave(" = -EPROTO");
	return -EPROTO;
error:
	_leave(" = %d", ret);
	return ret;
}

/*
 * Preparse an rxrpc defined key.
 *
 * Data should be of the form:
 *	OFFSET	LEN	CONTENT
 *	0	4	key interface version number
 *	4	2	security index (type)
 *	6	2	ticket length
 *	8	4	key expiry time (time_t)
 *	12	4	kvno
 *	16	8	session key
 *	24	[len]	ticket
 *
 * if no data is provided, then a no-security key is made
 */
static int rxrpc_preparse(struct key_preparsed_payload *prep)
{
	const struct rxrpc_key_data_v1 *v1;
	struct rxrpc_key_token *token, **pp;
	size_t plen;
	u32 kver;
	int ret;

	_enter("%zu", prep->datalen);

	/* handle a no-security key */
	if (!prep->data && prep->datalen == 0)
		return 0;

	/* determine if the XDR payload format is being used */
	if (prep->datalen > 7 * 4) {
		ret = rxrpc_preparse_xdr(prep);
		if (ret != -EPROTO)
			return ret;
	}

	/* get the key interface version number */
	ret = -EINVAL;
	if (prep->datalen <= 4 || !prep->data)
		goto error;
	memcpy(&kver, prep->data, sizeof(kver));
	prep->data += sizeof(kver);
	prep->datalen -= sizeof(kver);

	_debug("KEY I/F VERSION: %u", kver);

	ret = -EKEYREJECTED;
	if (kver != 1)
		goto error;

	/* deal with a version 1 key */
	ret = -EINVAL;
	if (prep->datalen < sizeof(*v1))
		goto error;

	v1 = prep->data;
	if (prep->datalen != sizeof(*v1) + v1->ticket_length)
		goto error;

	_debug("SCIX: %u", v1->security_index);
	_debug("TLEN: %u", v1->ticket_length);
	_debug("EXPY: %x", v1->expiry);
	_debug("KVNO: %u", v1->kvno);
	_debug("SKEY: %02x%02x%02x%02x%02x%02x%02x%02x",
	       v1->session_key[0], v1->session_key[1],
	       v1->session_key[2], v1->session_key[3],
	       v1->session_key[4], v1->session_key[5],
	       v1->session_key[6], v1->session_key[7]);
	if (v1->ticket_length >= 8)
		_debug("TCKT: %02x%02x%02x%02x%02x%02x%02x%02x",
		       v1->ticket[0], v1->ticket[1],
		       v1->ticket[2], v1->ticket[3],
		       v1->ticket[4], v1->ticket[5],
		       v1->ticket[6], v1->ticket[7]);

	ret = -EPROTONOSUPPORT;
	if (v1->security_index != RXRPC_SECURITY_RXKAD)
		goto error;

	plen = sizeof(*token->kad) + v1->ticket_length;
	prep->quotalen = plen + sizeof(*token);

	ret = -ENOMEM;
	token = kzalloc(sizeof(*token), GFP_KERNEL);
	if (!token)
		goto error;
	token->kad = kzalloc(plen, GFP_KERNEL);
	if (!token->kad)
		goto error_free;

	token->security_index		= RXRPC_SECURITY_RXKAD;
	token->kad->ticket_len		= v1->ticket_length;
	token->kad->expiry		= v1->expiry;
	token->kad->kvno		= v1->kvno;
	memcpy(&token->kad->session_key, &v1->session_key, 8);
	memcpy(&token->kad->ticket, v1->ticket, v1->ticket_length);

	/* count the number of tokens attached */
	prep->payload.data[1] = (void *)((unsigned long)prep->payload.data[1] + 1);

	/* attach the data */
	pp = (struct rxrpc_key_token **)&prep->payload.data[0];
	while (*pp)
		pp = &(*pp)->next;
	*pp = token;
	if (token->kad->expiry < prep->expiry)
		prep->expiry = token->kad->expiry;
	token = NULL;
	ret = 0;

error_free:
	kfree(token);
error:
	return ret;
}

/*
 * Free token list.
 */
static void rxrpc_free_token_list(struct rxrpc_key_token *token)
{
	struct rxrpc_key_token *next;

	for (; token; token = next) {
		next = token->next;
		switch (token->security_index) {
		case RXRPC_SECURITY_RXKAD:
			kfree(token->kad);
			break;
		case RXRPC_SECURITY_RXK5:
			if (token->k5)
				rxrpc_rxk5_free(token->k5);
			break;
		default:
			printk(KERN_ERR "Unknown token type %x on rxrpc key\n",
			       token->security_index);
			BUG();
		}

		kfree(token);
	}
}

/*
 * Clean up preparse data.
 */
static void rxrpc_free_preparse(struct key_preparsed_payload *prep)
{
	rxrpc_free_token_list(prep->payload.data[0]);
}

/*
 * Preparse a server secret key.
 *
 * The data should be the 8-byte secret key.
 */
static int rxrpc_preparse_s(struct key_preparsed_payload *prep)
{
	struct crypto_skcipher *ci;

	_enter("%zu", prep->datalen);

	if (prep->datalen != 8)
		return -EINVAL;

	memcpy(&prep->payload.data[2], prep->data, 8);

	ci = crypto_alloc_skcipher("pcbc(des)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(ci)) {
		_leave(" = %ld", PTR_ERR(ci));
		return PTR_ERR(ci);
	}

	if (crypto_skcipher_setkey(ci, prep->data, 8) < 0)
		BUG();

	prep->payload.data[0] = ci;
	_leave(" = 0");
	return 0;
}

/*
 * Clean up preparse data.
 */
static void rxrpc_free_preparse_s(struct key_preparsed_payload *prep)
{
	if (prep->payload.data[0])
		crypto_free_skcipher(prep->payload.data[0]);
}

/*
 * dispose of the data dangling from the corpse of a rxrpc key
 */
static void rxrpc_destroy(struct key *key)
{
	rxrpc_free_token_list(key->payload.data[0]);
}

/*
 * dispose of the data dangling from the corpse of a rxrpc key
 */
static void rxrpc_destroy_s(struct key *key)
{
	if (key->payload.data[0]) {
		crypto_free_skcipher(key->payload.data[0]);
		key->payload.data[0] = NULL;
	}
}

/*
 * describe the rxrpc key
 */
static void rxrpc_describe(const struct key *key, struct seq_file *m)
{
	seq_puts(m, key->description);
}

/*
 * grab the security key for a socket
 */
int rxrpc_request_key(struct rxrpc_sock *rx, char __user *optval, int optlen)
{
	struct key *key;
	char *description;

	_enter("");

	if (optlen <= 0 || optlen > PAGE_SIZE - 1)
		return -EINVAL;

	description = memdup_user_nul(optval, optlen);
	if (IS_ERR(description))
		return PTR_ERR(description);

	key = request_key(&key_type_rxrpc, description, NULL);
	if (IS_ERR(key)) {
		kfree(description);
		_leave(" = %ld", PTR_ERR(key));
		return PTR_ERR(key);
	}

	rx->key = key;
	kfree(description);
	_leave(" = 0 [key %x]", key->serial);
	return 0;
}

/*
 * grab the security keyring for a server socket
 */
int rxrpc_server_keyring(struct rxrpc_sock *rx, char __user *optval,
			 int optlen)
{
	struct key *key;
	char *description;

	_enter("");

	if (optlen <= 0 || optlen > PAGE_SIZE - 1)
		return -EINVAL;

	description = memdup_user_nul(optval, optlen);
	if (IS_ERR(description))
		return PTR_ERR(description);

	key = request_key(&key_type_keyring, description, NULL);
	if (IS_ERR(key)) {
		kfree(description);
		_leave(" = %ld", PTR_ERR(key));
		return PTR_ERR(key);
	}

	rx->securities = key;
	kfree(description);
	_leave(" = 0 [key %x]", key->serial);
	return 0;
}

/*
 * generate a server data key
 */
int rxrpc_get_server_data_key(struct rxrpc_connection *conn,
			      const void *session_key,
			      time_t expiry,
			      u32 kvno)
{
	const struct cred *cred = current_cred();
	struct key *key;
	int ret;

	struct {
		u32 kver;
		struct rxrpc_key_data_v1 v1;
	} data;

	_enter("");

	key = key_alloc(&key_type_rxrpc, "x",
			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, 0,
			KEY_ALLOC_NOT_IN_QUOTA, NULL);
	if (IS_ERR(key)) {
		_leave(" = -ENOMEM [alloc %ld]", PTR_ERR(key));
		return -ENOMEM;
	}

	_debug("key %d", key_serial(key));

	data.kver = 1;
	data.v1.security_index = RXRPC_SECURITY_RXKAD;
	data.v1.ticket_length = 0;
	data.v1.expiry = expiry;
	data.v1.kvno = 0;

	memcpy(&data.v1.session_key, session_key, sizeof(data.v1.session_key));

	ret = key_instantiate_and_link(key, &data, sizeof(data), NULL, NULL);
	if (ret < 0)
		goto error;

	conn->key = key;
	_leave(" = 0 [%d]", key_serial(key));
	return 0;

error:
	key_revoke(key);
	key_put(key);
	_leave(" = -ENOMEM [ins %d]", ret);
	return -ENOMEM;
}
EXPORT_SYMBOL(rxrpc_get_server_data_key);

/**
 * rxrpc_get_null_key - Generate a null RxRPC key
 * @keyname: The name to give the key.
 *
 * Generate a null RxRPC key that can be used to indicate anonymous security is
 * required for a particular domain.
 */
struct key *rxrpc_get_null_key(const char *keyname)
{
	const struct cred *cred = current_cred();
	struct key *key;
	int ret;

	key = key_alloc(&key_type_rxrpc, keyname,
			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
			KEY_POS_SEARCH, KEY_ALLOC_NOT_IN_QUOTA, NULL);
	if (IS_ERR(key))
		return key;

	ret = key_instantiate_and_link(key, NULL, 0, NULL, NULL);
	if (ret < 0) {
		key_revoke(key);
		key_put(key);
		return ERR_PTR(ret);
	}

	return key;
}
EXPORT_SYMBOL(rxrpc_get_null_key);

/*
 * read the contents of an rxrpc key
 * - this returns the result in XDR form
 */
static long rxrpc_read(const struct key *key,
		       char __user *buffer, size_t buflen)
{
	const struct rxrpc_key_token *token;
	const struct krb5_principal *princ;
	size_t size;
	__be32 __user *xdr, *oldxdr;
	u32 cnlen, toksize, ntoks, tok, zero;
	u16 toksizes[AFSTOKEN_MAX];
	int loop;

	_enter("");

	/* we don't know what form we should return non-AFS keys in */
	if (memcmp(key->description, "afs@", 4) != 0)
		return -EOPNOTSUPP;
	cnlen = strlen(key->description + 4);

#define RND(X) (((X) + 3) & ~3)

	/* AFS keys we return in XDR form, so we need to work out the size of
	 * the XDR */
	size = 2 * 4;	/* flags, cellname len */
	size += RND(cnlen);	/* cellname */
	size += 1 * 4;	/* token count */

	ntoks = 0;
	for (token = key->payload.data[0]; token; token = token->next) {
		toksize = 4;	/* sec index */

		switch (token->security_index) {
		case RXRPC_SECURITY_RXKAD:
			toksize += 8 * 4;	/* viceid, kvno, key*2, begin,
						 * end, primary, tktlen */
			toksize += RND(token->kad->ticket_len);
			break;

		case RXRPC_SECURITY_RXK5:
			princ = &token->k5->client;
			toksize += 4 + princ->n_name_parts * 4;
			for (loop = 0; loop < princ->n_name_parts; loop++)
				toksize += RND(strlen(princ->name_parts[loop]));
			toksize += 4 + RND(strlen(princ->realm));

			princ = &token->k5->server;
			toksize += 4 + princ->n_name_parts * 4;
			for (loop = 0; loop < princ->n_name_parts; loop++)
				toksize += RND(strlen(princ->name_parts[loop]));
			toksize += 4 + RND(strlen(princ->realm));

			toksize += 8 + RND(token->k5->session.data_len);

			toksize += 4 * 8 + 2 * 4;

			toksize += 4 + token->k5->n_addresses * 8;
			for (loop = 0; loop < token->k5->n_addresses; loop++)
				toksize += RND(token->k5->addresses[loop].data_len);

			toksize += 4 + RND(token->k5->ticket_len);
			toksize += 4 + RND(token->k5->ticket2_len);

			toksize += 4 + token->k5->n_authdata * 8;
			for (loop = 0; loop < token->k5->n_authdata; loop++)
				toksize += RND(token->k5->authdata[loop].data_len);
			break;

		default: /* we have a ticket we can't encode */
			BUG();
			continue;
		}

		_debug("token[%u]: toksize=%u", ntoks, toksize);
		ASSERTCMP(toksize, <=, AFSTOKEN_LENGTH_MAX);

		toksizes[ntoks++] = toksize;
		size += toksize + 4; /* each token has a length word */
	}

#undef RND

	if (!buffer || buflen < size)
		return size;

	xdr = (__be32 __user *) buffer;
	zero = 0;
#define ENCODE(x)				\
	do {					\
		__be32 y = htonl(x);		\
		if (put_user(y, xdr++) < 0)	\
			goto fault;		\
	} while(0)
#define ENCODE_DATA(l, s)						\
	do {								\
		u32 _l = (l);						\
		ENCODE(l);						\
		if (copy_to_user(xdr, (s), _l) != 0)			\
			goto fault;					\
		if (_l & 3 &&						\
		    copy_to_user((u8 __user *)xdr + _l, &zero, 4 - (_l & 3)) != 0) \
			goto fault;					\
		xdr += (_l + 3) >> 2;					\
	} while(0)
#define ENCODE64(x)					\
	do {						\
		__be64 y = cpu_to_be64(x);		\
		if (copy_to_user(xdr, &y, 8) != 0)	\
			goto fault;			\
		xdr += 8 >> 2;				\
	} while(0)
#define ENCODE_STR(s)				\
	do {					\
		const char *_s = (s);		\
		ENCODE_DATA(strlen(_s), _s);	\
	} while(0)

	ENCODE(0);					/* flags */
	ENCODE_DATA(cnlen, key->description + 4);	/* cellname */
	ENCODE(ntoks);

	tok = 0;
	for (token = key->payload.data[0]; token; token = token->next) {
		toksize = toksizes[tok++];
		ENCODE(toksize);
		oldxdr = xdr;
		ENCODE(token->security_index);

		switch (token->security_index) {
		case RXRPC_SECURITY_RXKAD:
			ENCODE(token->kad->vice_id);
			ENCODE(token->kad->kvno);
			ENCODE_DATA(8, token->kad->session_key);
			ENCODE(token->kad->start);
			ENCODE(token->kad->expiry);
			ENCODE(token->kad->primary_flag);
			ENCODE_DATA(token->kad->ticket_len, token->kad->ticket);
			break;

		case RXRPC_SECURITY_RXK5:
			princ = &token->k5->client;
			ENCODE(princ->n_name_parts);
			for (loop = 0; loop < princ->n_name_parts; loop++)
				ENCODE_STR(princ->name_parts[loop]);
			ENCODE_STR(princ->realm);

			princ = &token->k5->server;
			ENCODE(princ->n_name_parts);
			for (loop = 0; loop < princ->n_name_parts; loop++)
				ENCODE_STR(princ->name_parts[loop]);
			ENCODE_STR(princ->realm);

			ENCODE(token->k5->session.tag);
			ENCODE_DATA(token->k5->session.data_len,
				    token->k5->session.data);

			ENCODE64(token->k5->authtime);
			ENCODE64(token->k5->starttime);
			ENCODE64(token->k5->endtime);
			ENCODE64(token->k5->renew_till);
			ENCODE(token->k5->is_skey);
			ENCODE(token->k5->flags);

			ENCODE(token->k5->n_addresses);
			for (loop = 0; loop < token->k5->n_addresses; loop++) {
				ENCODE(token->k5->addresses[loop].tag);
				ENCODE_DATA(token->k5->addresses[loop].data_len,
					    token->k5->addresses[loop].data);
			}

			ENCODE_DATA(token->k5->ticket_len, token->k5->ticket);
			ENCODE_DATA(token->k5->ticket2_len, token->k5->ticket2);

			ENCODE(token->k5->n_authdata);
			for (loop = 0; loop < token->k5->n_authdata; loop++) {
				ENCODE(token->k5->authdata[loop].tag);
				ENCODE_DATA(token->k5->authdata[loop].data_len,
					    token->k5->authdata[loop].data);
			}
			break;

		default:
			BUG();
			break;
		}

		ASSERTCMP((unsigned long)xdr - (unsigned long)oldxdr, ==,
			  toksize);
	}

#undef ENCODE_STR
#undef ENCODE_DATA
#undef ENCODE64
#undef ENCODE

	ASSERTCMP(tok, ==, ntoks);
	ASSERTCMP((char __user *) xdr - buffer, ==, size);
	_leave(" = %zu", size);
	return size;

fault:
	_leave(" = -EFAULT");
	return -EFAULT;
}