[linux-2.6-block.git] / net / dns_resolver / dns_key.c

/* Key type used to cache DNS lookups made by the kernel
 *
 * See Documentation/networking/dns_resolver.txt
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Author(s): Igor Mammedov (niallain@gmail.com)
 *              Steve French (sfrench@us.ibm.com)
 *              Wang Lei (wang840925@gmail.com)
 *		David Howells (dhowells@redhat.com)
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/keyctl.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <linux/dns_resolver.h>
#include <keys/dns_resolver-type.h>
#include <keys/user-type.h>
#include "internal.h"

MODULE_DESCRIPTION("DNS Resolver");
MODULE_AUTHOR("Wang Lei");
MODULE_LICENSE("GPL");

unsigned int dns_resolver_debug;
module_param_named(debug, dns_resolver_debug, uint, 0644);
MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");

const struct cred *dns_resolver_cache;

#define	DNS_ERRORNO_OPTION	"dnserror"

/*
 * Preparse instantiation data for a dns_resolver key.
 *
 * For normal hostname lookups, the data must be a NUL-terminated string, with
 * the NUL char accounted in datalen.
 *
 * If the data contains a '#' characters, then we take the clause after each
 * one to be an option of the form 'key=value'.  The actual data of interest is
 * the string leading up to the first '#'.  For instance:
 *
 *        "ip1,ip2,...#foo=bar"
 *
 * For server list requests, the data must begin with a NUL char and be
 * followed by a byte indicating the version of the data format.  Version 1
 * looks something like (note this is packed):
 *
 *	u8      Non-string marker (ie. 0)
 *	u8	Content (DNS_PAYLOAD_IS_*)
 *	u8	Version (e.g. 1)
 *	u8	Source of server list
 *	u8	Lookup status of server list
 *	u8	Number of servers
 *	foreach-server {
 *		__le16	Name length
 *		__le16	Priority (as per SRV record, low first)
 *		__le16	Weight (as per SRV record, higher first)
 *		__le16	Port
 *		u8	Source of address list
 *		u8	Lookup status of address list
 *		u8	Protocol (DNS_SERVER_PROTOCOL_*)
 *		u8	Number of addresses
 *		char[]	Name (not NUL-terminated)
 *		foreach-address {
 *			u8		Family (DNS_ADDRESS_IS_*)
 *			union {
 *				u8[4]	ipv4_addr
 *				u8[16]	ipv6_addr
 *			}
 *		}
 *	}
 *
 */
static int
dns_resolver_preparse(struct key_preparsed_payload *prep)
{
	const struct dns_payload_header *bin;
	struct user_key_payload *upayload;
	unsigned long derrno;
	int ret;
	int datalen = prep->datalen, result_len = 0;
	const char *data = prep->data, *end, *opt;

	if (datalen <= 1 || !data)
		return -EINVAL;

	if (data[0] == 0) {
		/* It may be a server list. */
		if (datalen <= sizeof(*bin))
			return -EINVAL;

		bin = (const struct dns_payload_header *)data;
		kenter("[%u,%u],%u", bin->content, bin->version, datalen);
		if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) {
			pr_warn_ratelimited(
				"dns_resolver: Unsupported content type (%u)\n",
				bin->content);
			return -EINVAL;
		}

		if (bin->version != 1) {
			pr_warn_ratelimited(
				"dns_resolver: Unsupported server list version (%u)\n",
				bin->version);
			return -EINVAL;
		}

		result_len = datalen;
		goto store_result;
	}

	kenter("'%*.*s',%u", datalen, datalen, data, datalen);

	if (!data || data[datalen - 1] != '\0')
		return -EINVAL;
	datalen--;

	/* deal with any options embedded in the data */
	end = data + datalen;
	opt = memchr(data, '#', datalen);
	if (!opt) {
		/* no options: the entire data is the result */
		kdebug("no options");
		result_len = datalen;
	} else {
		const char *next_opt;

		result_len = opt - data;
		opt++;
		kdebug("options: '%s'", opt);
		do {
			int opt_len, opt_nlen;
			const char *eq;
			char optval[128];

			next_opt = memchr(opt, '#', end - opt) ?: end;
			opt_len = next_opt - opt;
			if (opt_len <= 0 || opt_len > sizeof(optval)) {
				pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n",
						    opt_len);
				return -EINVAL;
			}

			eq = memchr(opt, '=', opt_len);
			if (eq) {
				opt_nlen = eq - opt;
				eq++;
				memcpy(optval, eq, next_opt - eq);
				optval[next_opt - eq] = '\0';
			} else {
				opt_nlen = opt_len;
				optval[0] = '\0';
			}

			kdebug("option '%*.*s' val '%s'",
			       opt_nlen, opt_nlen, opt, optval);

			/* see if it's an error number representing a DNS error
			 * that's to be recorded as the result in this key */
			if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
			    memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
				kdebug("dns error number option");

				ret = kstrtoul(optval, 10, &derrno);
				if (ret < 0)
					goto bad_option_value;

				if (derrno < 1 || derrno > 511)
					goto bad_option_value;

				kdebug("dns error no. = %lu", derrno);
				prep->payload.data[dns_key_error] = ERR_PTR(-derrno);
				continue;
			}

		bad_option_value:
			pr_warn_ratelimited("Option '%*.*s' to dns_resolver key: bad/missing value\n",
					    opt_nlen, opt_nlen, opt);
			return -EINVAL;
		} while (opt = next_opt + 1, opt < end);
	}

	/* don't cache the result if we're caching an error saying there's no
	 * result */
	if (prep->payload.data[dns_key_error]) {
		kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error]));
		return 0;
	}

store_result:
	kdebug("store result");
	prep->quotalen = result_len;

	upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL);
	if (!upayload) {
		kleave(" = -ENOMEM");
		return -ENOMEM;
	}

	upayload->datalen = result_len;
	memcpy(upayload->data, data, result_len);
	upayload->data[result_len] = '\0';

	prep->payload.data[dns_key_data] = upayload;
	kleave(" = 0");
	return 0;
}

/*
 * Clean up the preparse data
 */
static void dns_resolver_free_preparse(struct key_preparsed_payload *prep)
{
	pr_devel("==>%s()\n", __func__);

	kfree(prep->payload.data[dns_key_data]);
}

/*
 * The description is of the form "[<type>:]<domain_name>"
 *
 * The domain name may be a simple name or an absolute domain name (which
 * should end with a period).  The domain name is case-independent.
 */
static bool dns_resolver_cmp(const struct key *key,
			     const struct key_match_data *match_data)
{
	int slen, dlen, ret = 0;
	const char *src = key->description, *dsp = match_data->raw_data;

	kenter("%s,%s", src, dsp);

	if (!src || !dsp)
		goto no_match;

	if (strcasecmp(src, dsp) == 0)
		goto matched;

	slen = strlen(src);
	dlen = strlen(dsp);
	if (slen <= 0 || dlen <= 0)
		goto no_match;
	if (src[slen - 1] == '.')
		slen--;
	if (dsp[dlen - 1] == '.')
		dlen--;
	if (slen != dlen || strncasecmp(src, dsp, slen) != 0)
		goto no_match;

matched:
	ret = 1;
no_match:
	kleave(" = %d", ret);
	return ret;
}

/*
 * Preparse the match criterion.
 */
static int dns_resolver_match_preparse(struct key_match_data *match_data)
{
	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
	match_data->cmp = dns_resolver_cmp;
	return 0;
}

/*
 * Describe a DNS key
 */
static void dns_resolver_describe(const struct key *key, struct seq_file *m)
{
	seq_puts(m, key->description);
	if (key_is_positive(key)) {
		int err = PTR_ERR(key->payload.data[dns_key_error]);

		if (err)
			seq_printf(m, ": %d", err);
		else
			seq_printf(m, ": %u", key->datalen);
	}
}

/*
 * read the DNS data
 * - the key's semaphore is read-locked
 */
static long dns_resolver_read(const struct key *key,
			      char __user *buffer, size_t buflen)
{
	int err = PTR_ERR(key->payload.data[dns_key_error]);

	if (err)
		return err;

	return user_read(key, buffer, buflen);
}

struct key_type key_type_dns_resolver = {
	.name		= "dns_resolver",
	.flags		= KEY_TYPE_NET_DOMAIN,
	.preparse	= dns_resolver_preparse,
	.free_preparse	= dns_resolver_free_preparse,
	.instantiate	= generic_key_instantiate,
	.match_preparse	= dns_resolver_match_preparse,
	.revoke		= user_revoke,
	.destroy	= user_destroy,
	.describe	= dns_resolver_describe,
	.read		= dns_resolver_read,
};

static int __init init_dns_resolver(void)
{
	struct cred *cred;
	struct key *keyring;
	int ret;

	/* create an override credential set with a special thread keyring in
	 * which DNS requests are cached
	 *
	 * this is used to prevent malicious redirections from being installed
	 * with add_key().
	 */
	cred = prepare_kernel_cred(NULL);
	if (!cred)
		return -ENOMEM;

	keyring = keyring_alloc(".dns_resolver",
				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
				KEY_USR_VIEW | KEY_USR_READ,
				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
	if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto failed_put_cred;
	}

	ret = register_key_type(&key_type_dns_resolver);
	if (ret < 0)
		goto failed_put_key;

	/* instruct request_key() to use this special keyring as a cache for
	 * the results it looks up */
	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
	cred->thread_keyring = keyring;
	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
	dns_resolver_cache = cred;

	kdebug("DNS resolver keyring: %d\n", key_serial(keyring));
	return 0;

failed_put_key:
	key_put(keyring);
failed_put_cred:
	put_cred(cred);
	return ret;
}

static void __exit exit_dns_resolver(void)
{
	key_revoke(dns_resolver_cache->thread_keyring);
	unregister_key_type(&key_type_dns_resolver);
	put_cred(dns_resolver_cache);
}

module_init(init_dns_resolver)
module_exit(exit_dns_resolver)
MODULE_LICENSE("GPL");
Commit	Line	Data
1a4240f4 WL	1	/* Key type used to cache DNS lookups made by the kernel
	2	*
	3	* See Documentation/networking/dns_resolver.txt
	4	*
	5	* Copyright (c) 2007 Igor Mammedov
	6	* Author(s): Igor Mammedov (niallain@gmail.com)
	7	* Steve French (sfrench@us.ibm.com)
	8	* Wang Lei (wang840925@gmail.com)
	9	* David Howells (dhowells@redhat.com)
	10	*
	11	* This library is free software; you can redistribute it and/or modify
	12	* it under the terms of the GNU Lesser General Public License as published
	13	* by the Free Software Foundation; either version 2.1 of the License, or
	14	* (at your option) any later version.
	15	*
	16	* This library is distributed in the hope that it will be useful,
	17	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
	19	* the GNU Lesser General Public License for more details.
	20	*
	21	* You should have received a copy of the GNU Lesser General Public License
c057b190	22	* along with this library; if not, see <http://www.gnu.org/licenses/>.
1a4240f4 WL	23	*/
	24	#include <linux/module.h>
	25	#include <linux/moduleparam.h>
	26	#include <linux/slab.h>
	27	#include <linux/string.h>
	28	#include <linux/kernel.h>
	29	#include <linux/keyctl.h>
af352fe9	30	#include <linux/err.h>
4a2d7892	31	#include <linux/seq_file.h>
bbb4c432	32	#include <linux/dns_resolver.h>
1a4240f4 WL	33	#include <keys/dns_resolver-type.h>
	34	#include <keys/user-type.h>
	35	#include "internal.h"
	36
	37	MODULE_DESCRIPTION("DNS Resolver");
	38	MODULE_AUTHOR("Wang Lei");
	39	MODULE_LICENSE("GPL");
	40
95c96174	41	unsigned int dns_resolver_debug;
d6444062	42	module_param_named(debug, dns_resolver_debug, uint, 0644);
1a4240f4 WL	43	MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
	44
	45	const struct cred *dns_resolver_cache;
	46
4a2d7892 WL	47	#define DNS_ERRORNO_OPTION "dnserror"
4a2d7892 WL	48
1a4240f4	49	/*
d46d4942	50	* Preparse instantiation data for a dns_resolver key.
1a4240f4	51	*
bbb4c432 DH	52	* For normal hostname lookups, the data must be a NUL-terminated string, with
bbb4c432 DH	53	* the NUL char accounted in datalen.
1a4240f4 WL	54	*
	55	* If the data contains a '#' characters, then we take the clause after each
	56	* one to be an option of the form 'key=value'. The actual data of interest is
	57	* the string leading up to the first '#'. For instance:
	58	*
	59	* "ip1,ip2,...#foo=bar"
bbb4c432 DH	60	*
	61	* For server list requests, the data must begin with a NUL char and be
	62	* followed by a byte indicating the version of the data format. Version 1
	63	* looks something like (note this is packed):
	64	*
	65	* u8 Non-string marker (ie. 0)
	66	* u8 Content (DNS_PAYLOAD_IS_*)
	67	* u8 Version (e.g. 1)
	68	* u8 Source of server list
	69	* u8 Lookup status of server list
	70	* u8 Number of servers
	71	* foreach-server {
	72	* __le16 Name length
	73	* __le16 Priority (as per SRV record, low first)
	74	* __le16 Weight (as per SRV record, higher first)
	75	* __le16 Port
	76	* u8 Source of address list
	77	* u8 Lookup status of address list
	78	* u8 Protocol (DNS_SERVER_PROTOCOL_*)
	79	* u8 Number of addresses
	80	* char[] Name (not NUL-terminated)
	81	* foreach-address {
	82	* u8 Family (DNS_ADDRESS_IS_*)
	83	* union {
	84	* u8[4] ipv4_addr
	85	* u8[16] ipv6_addr
	86	* }
	87	* }
	88	* }
	89	*
1a4240f4 WL	90	*/
1a4240f4 WL	91	static int
d46d4942	92	dns_resolver_preparse(struct key_preparsed_payload *prep)
1a4240f4	93	{
bbb4c432	94	const struct dns_payload_header *bin;
1a4240f4	95	struct user_key_payload *upayload;
4a2d7892	96	unsigned long derrno;
1a4240f4	97	int ret;
d46d4942	98	int datalen = prep->datalen, result_len = 0;
cf7f601c	99	const char data = prep->data, end, *opt;
1a4240f4	100
bbb4c432 DH	101	if (datalen <= 1 \|\| !data)
	102	return -EINVAL;
	103
	104	if (data[0] == 0) {
	105	/* It may be a server list. */
	106	if (datalen <= sizeof(*bin))
	107	return -EINVAL;
	108
	109	bin = (const struct dns_payload_header *)data;
	110	kenter("[%u,%u],%u", bin->content, bin->version, datalen);
	111	if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) {
	112	pr_warn_ratelimited(
	113	"dns_resolver: Unsupported content type (%u)\n",
	114	bin->content);
	115	return -EINVAL;
	116	}
	117
	118	if (bin->version != 1) {
	119	pr_warn_ratelimited(
	120	"dns_resolver: Unsupported server list version (%u)\n",
	121	bin->version);
	122	return -EINVAL;
	123	}
	124
	125	result_len = datalen;
	126	goto store_result;
	127	}
	128
d46d4942	129	kenter("'%.s',%u", datalen, datalen, data, datalen);
1a4240f4	130
bbb4c432	131	if (!data \|\| data[datalen - 1] != '\0')
1a4240f4 WL	132	return -EINVAL;
	133	datalen--;
	134
	135	/* deal with any options embedded in the data */
4a2d7892	136	end = data + datalen;
1a4240f4 WL	137	opt = memchr(data, '#', datalen);
1a4240f4 WL	138	if (!opt) {
4a2d7892 WL	139	/* no options: the entire data is the result */
	140	kdebug("no options");
	141	result_len = datalen;
	142	} else {
	143	const char *next_opt;
	144
	145	result_len = opt - data;
	146	opt++;
	147	kdebug("options: '%s'", opt);
	148	do {
c604cb76	149	int opt_len, opt_nlen;
4a2d7892	150	const char *eq;
c604cb76	151	char optval[128];
4a2d7892 WL	152
	153	next_opt = memchr(opt, '#', end - opt) ?: end;
	154	opt_len = next_opt - opt;
c604cb76	155	if (opt_len <= 0 \|\| opt_len > sizeof(optval)) {
9c438d7a EB	156	pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n",
9c438d7a EB	157	opt_len);
4a2d7892 WL	158	return -EINVAL;
	159	}
	160
c604cb76 EB	161	eq = memchr(opt, '=', opt_len);
	162	if (eq) {
	163	opt_nlen = eq - opt;
	164	eq++;
	165	memcpy(optval, eq, next_opt - eq);
	166	optval[next_opt - eq] = '\0';
	167	} else {
	168	opt_nlen = opt_len;
	169	optval[0] = '\0';
	170	}
4a2d7892	171
c604cb76 EB	172	kdebug("option '%.s' val '%s'",
c604cb76 EB	173	opt_nlen, opt_nlen, opt, optval);
4a2d7892 WL	174
	175	/* see if it's an error number representing a DNS error
	176	* that's to be recorded as the result in this key */
	177	if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
	178	memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
	179	kdebug("dns error number option");
4a2d7892	180
c604cb76	181	ret = kstrtoul(optval, 10, &derrno);
4a2d7892 WL	182	if (ret < 0)
	183	goto bad_option_value;
	184
	185	if (derrno < 1 \|\| derrno > 511)
	186	goto bad_option_value;
	187
	188	kdebug("dns error no. = %lu", derrno);
146aa8b1	189	prep->payload.data[dns_key_error] = ERR_PTR(-derrno);
4a2d7892 WL	190	continue;
	191	}
	192
	193	bad_option_value:
9c438d7a EB	194	pr_warn_ratelimited("Option '%.s' to dns_resolver key: bad/missing value\n",
9c438d7a EB	195	opt_nlen, opt_nlen, opt);
4a2d7892 WL	196	return -EINVAL;
4a2d7892 WL	197	} while (opt = next_opt + 1, opt < end);
1a4240f4 WL	198	}
1a4240f4 WL	199
4a2d7892 WL	200	/* don't cache the result if we're caching an error saying there's no
4a2d7892 WL	201	* result */
146aa8b1 DH	202	if (prep->payload.data[dns_key_error]) {
146aa8b1 DH	203	kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error]));
4a2d7892 WL	204	return 0;
	205	}
	206
bbb4c432	207	store_result:
4a2d7892	208	kdebug("store result");
d46d4942	209	prep->quotalen = result_len;
1a4240f4 WL	210
	211	upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL);
	212	if (!upayload) {
	213	kleave(" = -ENOMEM");
	214	return -ENOMEM;
	215	}
	216
	217	upayload->datalen = result_len;
	218	memcpy(upayload->data, data, result_len);
	219	upayload->data[result_len] = '\0';
1a4240f4	220
146aa8b1	221	prep->payload.data[dns_key_data] = upayload;
1a4240f4 WL	222	kleave(" = 0");
	223	return 0;
	224	}
	225
d46d4942 DH	226	/*
	227	* Clean up the preparse data
	228	*/
	229	static void dns_resolver_free_preparse(struct key_preparsed_payload *prep)
	230	{
	231	pr_devel("==>%s()\n", __func__);
	232
146aa8b1	233	kfree(prep->payload.data[dns_key_data]);
d46d4942 DH	234	}
d46d4942 DH	235
1a4240f4 WL	236	/*
	237	* The description is of the form "[<type>:]<domain_name>"
	238	*
	239	* The domain name may be a simple name or an absolute domain name (which
	240	* should end with a period). The domain name is case-independent.
	241	*/
0c903ab6 DH	242	static bool dns_resolver_cmp(const struct key *key,
0c903ab6 DH	243	const struct key_match_data *match_data)
1a4240f4 WL	244	{
1a4240f4 WL	245	int slen, dlen, ret = 0;
46291959	246	const char src = key->description, dsp = match_data->raw_data;
1a4240f4 WL	247
	248	kenter("%s,%s", src, dsp);
	249
	250	if (!src \|\| !dsp)
	251	goto no_match;
	252
	253	if (strcasecmp(src, dsp) == 0)
	254	goto matched;
	255
	256	slen = strlen(src);
	257	dlen = strlen(dsp);
	258	if (slen <= 0 \|\| dlen <= 0)
	259	goto no_match;
	260	if (src[slen - 1] == '.')
	261	slen--;
	262	if (dsp[dlen - 1] == '.')
	263	dlen--;
	264	if (slen != dlen \|\| strncasecmp(src, dsp, slen) != 0)
	265	goto no_match;
	266
	267	matched:
	268	ret = 1;
	269	no_match:
	270	kleave(" = %d", ret);
	271	return ret;
	272	}
	273
c06cfb08 DH	274	/*
	275	* Preparse the match criterion.
	276	*/
	277	static int dns_resolver_match_preparse(struct key_match_data *match_data)
	278	{
	279	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
	280	match_data->cmp = dns_resolver_cmp;
	281	return 0;
	282	}
	283
4a2d7892 WL	284	/*
	285	* Describe a DNS key
	286	*/
	287	static void dns_resolver_describe(const struct key key, struct seq_file m)
	288	{
4a2d7892	289	seq_puts(m, key->description);
363b02da	290	if (key_is_positive(key)) {
146aa8b1 DH	291	int err = PTR_ERR(key->payload.data[dns_key_error]);
146aa8b1 DH	292
78b7280c DH	293	if (err)
	294	seq_printf(m, ": %d", err);
	295	else
	296	seq_printf(m, ": %u", key->datalen);
	297	}
4a2d7892 WL	298	}
4a2d7892 WL	299
1362fa07 DH	300	/*
	301	* read the DNS data
	302	* - the key's semaphore is read-locked
	303	*/
	304	static long dns_resolver_read(const struct key *key,
	305	char __user *buffer, size_t buflen)
	306	{
146aa8b1 DH	307	int err = PTR_ERR(key->payload.data[dns_key_error]);
	308
	309	if (err)
	310	return err;
1362fa07 DH	311
	312	return user_read(key, buffer, buflen);
	313	}
	314
1a4240f4 WL	315	struct key_type key_type_dns_resolver = {
1a4240f4 WL	316	.name = "dns_resolver",
9b242610	317	.flags = KEY_TYPE_NET_DOMAIN,
d46d4942 DH	318	.preparse = dns_resolver_preparse,
	319	.free_preparse = dns_resolver_free_preparse,
	320	.instantiate = generic_key_instantiate,
c06cfb08	321	.match_preparse = dns_resolver_match_preparse,
1a4240f4 WL	322	.revoke = user_revoke,
1a4240f4 WL	323	.destroy = user_destroy,
4a2d7892	324	.describe = dns_resolver_describe,
1362fa07	325	.read = dns_resolver_read,
1a4240f4 WL	326	};
	327
	328	static int __init init_dns_resolver(void)
	329	{
	330	struct cred *cred;
	331	struct key *keyring;
	332	int ret;
	333
1a4240f4 WL	334	/* create an override credential set with a special thread keyring in
	335	* which DNS requests are cached
	336	*
	337	* this is used to prevent malicious redirections from being installed
	338	* with add_key().
	339	*/
	340	cred = prepare_kernel_cred(NULL);
	341	if (!cred)
	342	return -ENOMEM;
	343
2a74dbb9 LT	344	keyring = keyring_alloc(".dns_resolver",
2a74dbb9 LT	345	GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
028db3e2 LT	346	(KEY_POS_ALL & ~KEY_POS_SETATTR) \|
028db3e2 LT	347	KEY_USR_VIEW \| KEY_USR_READ,
5ac7eace	348	KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
1a4240f4 WL	349	if (IS_ERR(keyring)) {
	350	ret = PTR_ERR(keyring);
	351	goto failed_put_cred;
	352	}
	353
1a4240f4 WL	354	ret = register_key_type(&key_type_dns_resolver);
	355	if (ret < 0)
	356	goto failed_put_key;
	357
	358	/* instruct request_key() to use this special keyring as a cache for
	359	* the results it looks up */
700920eb	360	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
1a4240f4 WL	361	cred->thread_keyring = keyring;
	362	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
	363	dns_resolver_cache = cred;
	364
	365	kdebug("DNS resolver keyring: %d\n", key_serial(keyring));
	366	return 0;
	367
	368	failed_put_key:
	369	key_put(keyring);
	370	failed_put_cred:
	371	put_cred(cred);
	372	return ret;
	373	}
	374
	375	static void __exit exit_dns_resolver(void)
	376	{
	377	key_revoke(dns_resolver_cache->thread_keyring);
	378	unregister_key_type(&key_type_dns_resolver);
	379	put_cred(dns_resolver_cache);
1a4240f4 WL	380	}
	381
	382	module_init(init_dns_resolver)
	383	module_exit(exit_dns_resolver)
	384	MODULE_LICENSE("GPL");