cipso_ipv4.c

linux 内核源代码

/*
 * CIPSO - Commercial IP Security Option
 *
 * This is an implementation of the CIPSO 2.2 protocol as specified in
 * draft-ietf-cipso-ipsecurity-01.txt with additional tag types as found in
 * FIPS-188, copies of both documents can be found in the Documentation
 * directory.  While CIPSO never became a full IETF RFC standard many vendors
 * have chosen to adopt the protocol and over the years it has become a
 * de-facto standard for labeled networking.
 *
 * Author: Paul Moore <[e-mail]>
 *
 */

/*
 * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
 *
 * 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.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program;  if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/jhash.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/netlabel.h>
#include <net/cipso_ipv4.h>
#include <asm/atomic.h>
#include <asm/bug.h>
#include <asm/unaligned.h>

struct cipso_v4_domhsh_entry {
	char *domain;
	u32 valid;
	struct list_head list;
	struct rcu_head rcu;
};

/* List of available DOI definitions */
/* XXX - Updates should be minimal so having a single lock for the
 * cipso_v4_doi_list and the cipso_v4_doi_list->dom_list should be
 * okay. */
/* XXX - This currently assumes a minimal number of different DOIs in use,
 * if in practice there are a lot of different DOIs this list should
 * probably be turned into a hash table or something similar so we
 * can do quick lookups. */
static DEFINE_SPINLOCK(cipso_v4_doi_list_lock);
static struct list_head cipso_v4_doi_list = LIST_HEAD_INIT(cipso_v4_doi_list);

/* Label mapping cache */
int cipso_v4_cache_enabled = 1;
int cipso_v4_cache_bucketsize = 10;
#define CIPSO_V4_CACHE_BUCKETBITS     7
#define CIPSO_V4_CACHE_BUCKETS        (1 << CIPSO_V4_CACHE_BUCKETBITS)
#define CIPSO_V4_CACHE_REORDERLIMIT   10
struct cipso_v4_map_cache_bkt {
	spinlock_t lock;
	u32 size;
	struct list_head list;
};
struct cipso_v4_map_cache_entry {
	u32 hash;
	unsigned char *key;
	size_t key_len;

	struct netlbl_lsm_cache *lsm_data;

	u32 activity;
	struct list_head list;
};
static struct cipso_v4_map_cache_bkt *cipso_v4_cache = NULL;

/* Restricted bitmap (tag #1) flags */
int cipso_v4_rbm_optfmt = 0;
int cipso_v4_rbm_strictvalid = 1;

/*
 * Protocol Constants
 */

/* Maximum size of the CIPSO IP option, derived from the fact that the maximum
 * IPv4 header size is 60 bytes and the base IPv4 header is 20 bytes long. */
#define CIPSO_V4_OPT_LEN_MAX          40

/* Length of the base CIPSO option, this includes the option type (1 byte), the
 * option length (1 byte), and the DOI (4 bytes). */
#define CIPSO_V4_HDR_LEN              6

/* Base length of the restrictive category bitmap tag (tag #1). */
#define CIPSO_V4_TAG_RBM_BLEN         4

/* Base length of the enumerated category tag (tag #2). */
#define CIPSO_V4_TAG_ENUM_BLEN        4

/* Base length of the ranged categories bitmap tag (tag #5). */
#define CIPSO_V4_TAG_RNG_BLEN         4
/* The maximum number of category ranges permitted in the ranged category tag
 * (tag #5).  You may note that the IETF draft states that the maximum number
 * of category ranges is 7, but if the low end of the last category range is
 * zero then it is possibile to fit 8 category ranges because the zero should
 * be omitted. */
#define CIPSO_V4_TAG_RNG_CAT_MAX      8

/*
 * Helper Functions
 */

/**
 * cipso_v4_bitmap_walk - Walk a bitmap looking for a bit
 * @bitmap: the bitmap
 * @bitmap_len: length in bits
 * @offset: starting offset
 * @state: if non-zero, look for a set (1) bit else look for a cleared (0) bit
 *
 * Description:
 * Starting at @offset, walk the bitmap from left to right until either the
 * desired bit is found or we reach the end.  Return the bit offset, -1 if
 * not found, or -2 if error.
 */
static int cipso_v4_bitmap_walk(const unsigned char *bitmap,
				u32 bitmap_len,
				u32 offset,
				u8 state)
{
	u32 bit_spot;
	u32 byte_offset;
	unsigned char bitmask;
	unsigned char byte;

	/* gcc always rounds to zero when doing integer division */
	byte_offset = offset / 8;
	byte = bitmap[byte_offset];
	bit_spot = offset;
	bitmask = 0x80 >> (offset % 8);

	while (bit_spot < bitmap_len) {
		if ((state && (byte & bitmask) == bitmask) ||
		    (state == 0 && (byte & bitmask) == 0))
			return bit_spot;

		bit_spot++;
		bitmask >>= 1;
		if (bitmask == 0) {
			byte = bitmap[++byte_offset];
			bitmask = 0x80;
		}
	}

	return -1;
}

/**
 * cipso_v4_bitmap_setbit - Sets a single bit in a bitmap
 * @bitmap: the bitmap
 * @bit: the bit
 * @state: if non-zero, set the bit (1) else clear the bit (0)
 *
 * Description:
 * Set a single bit in the bitmask.  Returns zero on success, negative values
 * on error.
 */
static void cipso_v4_bitmap_setbit(unsigned char *bitmap,
				   u32 bit,
				   u8 state)
{
	u32 byte_spot;
	u8 bitmask;

	/* gcc always rounds to zero when doing integer division */
	byte_spot = bit / 8;
	bitmask = 0x80 >> (bit % 8);
	if (state)
		bitmap[byte_spot] |= bitmask;
	else
		bitmap[byte_spot] &= ~bitmask;
}

/**
 * cipso_v4_doi_domhsh_free - Frees a domain list entry
 * @entry: the entry's RCU field
 *
 * Description:
 * This function is designed to be used as a callback to the call_rcu()
 * function so that the memory allocated to a domain list entry can be released
 * safely.
 *
 */
static void cipso_v4_doi_domhsh_free(struct rcu_head *entry)
{
	struct cipso_v4_domhsh_entry *ptr;

	ptr = container_of(entry, struct cipso_v4_domhsh_entry, rcu);
	kfree(ptr->domain);
	kfree(ptr);
}

/**
 * cipso_v4_cache_entry_free - Frees a cache entry
 * @entry: the entry to free
 *
 * Description:
 * This function frees the memory associated with a cache entry including the
 * LSM cache data if there are no longer any users, i.e. reference count == 0.
 *
 */
static void cipso_v4_cache_entry_free(struct cipso_v4_map_cache_entry *entry)
{
	if (entry->lsm_data)
		netlbl_secattr_cache_free(entry->lsm_data);
	kfree(entry->key);
	kfree(entry);
}

/**
 * cipso_v4_map_cache_hash - Hashing function for the CIPSO cache
 * @key: the hash key
 * @key_len: the length of the key in bytes
 *
 * Description:
 * The CIPSO tag hashing function.  Returns a 32-bit hash value.
 *
 */
static u32 cipso_v4_map_cache_hash(const unsigned char *key, u32 key_len)
{
	return jhash(key, key_len, 0);
}

/*
 * Label Mapping Cache Functions
 */

/**
 * cipso_v4_cache_init - Initialize the CIPSO cache
 *
 * Description:
 * Initializes the CIPSO label mapping cache, this function should be called
 * before any of the other functions defined in this file.  Returns zero on
 * success, negative values on error.
 *
 */
static int cipso_v4_cache_init(void)
{
	u32 iter;

	cipso_v4_cache = kcalloc(CIPSO_V4_CACHE_BUCKETS,
				 sizeof(struct cipso_v4_map_cache_bkt),
				 GFP_KERNEL);
	if (cipso_v4_cache == NULL)
		return -ENOMEM;

	for (iter = 0; iter < CIPSO_V4_CACHE_BUCKETS; iter++) {
		spin_lock_init(&cipso_v4_cache[iter].lock);
		cipso_v4_cache[iter].size = 0;
		INIT_LIST_HEAD(&cipso_v4_cache[iter].list);
	}

	return 0;
}

/**
 * cipso_v4_cache_invalidate - Invalidates the current CIPSO cache
 *
 * Description:
 * Invalidates and frees any entries in the CIPSO cache.  Returns zero on
 * success and negative values on failure.
 *
 */
void cipso_v4_cache_invalidate(void)
{
	struct cipso_v4_map_cache_entry *entry, *tmp_entry;
	u32 iter;

	for (iter = 0; iter < CIPSO_V4_CACHE_BUCKETS; iter++) {
		spin_lock_bh(&cipso_v4_cache[iter].lock);
		list_for_each_entry_safe(entry,
					 tmp_entry,
					 &cipso_v4_cache[iter].list, list) {
			list_del(&entry->list);
			cipso_v4_cache_entry_free(entry);
		}
		cipso_v4_cache[iter].size = 0;
		spin_unlock_bh(&cipso_v4_cache[iter].lock);
	}

	return;
}

/**
 * cipso_v4_cache_check - Check the CIPSO cache for a label mapping
 * @key: the buffer to check
 * @key_len: buffer length in bytes
 * @secattr: the security attribute struct to use
 *
 * Description:
 * This function checks the cache to see if a label mapping already exists for
 * the given key.  If there is a match then the cache is adjusted and the
 * @secattr struct is populated with the correct LSM security attributes.  The
 * cache is adjusted in the following manner if the entry is not already the
 * first in the cache bucket:
 *
 *  1. The cache entry's activity counter is incremented
 *  2. The previous (higher ranking) entry's activity counter is decremented
 *  3. If the difference between the two activity counters is geater than
 *     CIPSO_V4_CACHE_REORDERLIMIT the two entries are swapped
 *
 * Returns zero on success, -ENOENT for a cache miss, and other negative values
 * on error.
 *
 */
static int cipso_v4_cache_check(const unsigned char *key,
				u32 key_len,
				struct netlbl_lsm_secattr *secattr)
{
	u32 bkt;
	struct cipso_v4_map_cache_entry *entry;
	struct cipso_v4_map_cache_entry *prev_entry = NULL;
	u32 hash;

	if (!cipso_v4_cache_enabled)
		return -ENOENT;

	hash = cipso_v4_map_cache_hash(key, key_len);
	bkt = hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
	spin_lock_bh(&cipso_v4_cache[bkt].lock);
	list_for_each_entry(entry, &cipso_v4_cache[bkt].list, list) {
		if (entry->hash == hash &&
		    entry->key_len == key_len &&
		    memcmp(entry->key, key, key_len) == 0) {
			entry->activity += 1;
			atomic_inc(&entry->lsm_data->refcount);
			secattr->cache = entry->lsm_data;
			secattr->flags |= NETLBL_SECATTR_CACHE;
			if (prev_entry == NULL) {
				spin_unlock_bh(&cipso_v4_cache[bkt].lock);
				return 0;
			}

			if (prev_entry->activity > 0)
				prev_entry->activity -= 1;
			if (entry->activity > prev_entry->activity &&
			    entry->activity - prev_entry->activity >
			    CIPSO_V4_CACHE_REORDERLIMIT) {
				__list_del(entry->list.prev, entry->list.next);
				__list_add(&entry->list,
					   prev_entry->list.prev,
					   &prev_entry->list);
			}

			spin_unlock_bh(&cipso_v4_cache[bkt].lock);
			return 0;
		}
		prev_entry = entry;
	}
	spin_unlock_bh(&cipso_v4_cache[bkt].lock);

	return -ENOENT;
}

/**
 * cipso_v4_cache_add - Add an entry to the CIPSO cache
 * @skb: the packet
 * @secattr: the packet's security attributes
 *
 * Description:
 * Add a new entry into the CIPSO label mapping cache.  Add the new entry to
 * head of the cache bucket's list, if the cache bucket is out of room remove
 * the last entry in the list first.  It is important to note that there is
 * currently no checking for duplicate keys.  Returns zero on success,
 * negative values on failure.
 *
 */
int cipso_v4_cache_add(const struct sk_buff *skb,
		       const struct netlbl_lsm_secattr *secattr)
{
	int ret_val = -EPERM;
	u32 bkt;
	struct cipso_v4_map_cache_entry *entry = NULL;
	struct cipso_v4_map_cache_entry *old_entry = NULL;
	unsigned char *cipso_ptr;
	u32 cipso_ptr_len;

	if (!cipso_v4_cache_enabled || cipso_v4_cache_bucketsize <= 0)
		return 0;

	cipso_ptr = CIPSO_V4_OPTPTR(skb);
	cipso_ptr_len = cipso_ptr[1];

	entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
	if (entry == NULL)
		return -ENOMEM;
	entry->key = kmemdup(cipso_ptr, cipso_ptr_len, GFP_ATOMIC);
	if (entry->key == NULL) {
		ret_val = -ENOMEM;
		goto cache_add_failure;
	}
	entry->key_len = cipso_ptr_len;
	entry->hash = cipso_v4_map_cache_hash(cipso_ptr, cipso_ptr_len);
	atomic_inc(&secattr->cache->refcount);
	entry->lsm_data = secattr->cache;

	bkt = entry->hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
	spin_lock_bh(&cipso_v4_cache[bkt].lock);
	if (cipso_v4_cache[bkt].size < cipso_v4_cache_bucketsize) {
		list_add(&entry->list, &cipso_v4_cache[bkt].list);
		cipso_v4_cache[bkt].size += 1;
	} else {
		old_entry = list_entry(cipso_v4_cache[bkt].list.prev,
				       struct cipso_v4_map_cache_entry, list);
		list_del(&old_entry->list);
		list_add(&entry->list, &cipso_v4_cache[bkt].list);
		cipso_v4_cache_entry_free(old_entry);
	}
	spin_unlock_bh(&cipso_v4_cache[bkt].lock);

	return 0;

cache_add_failure:
	if (entry)
		cipso_v4_cache_entry_free(entry);
	return ret_val;
}

/*
 * DOI List Functions
 */

/**
 * cipso_v4_doi_search - Searches for a DOI definition
 * @doi: the DOI to search for
 *
 * Description:
 * Search the DOI definition list for a DOI definition with a DOI value that
 * matches @doi.  The caller is responsibile for calling rcu_read_[un]lock().
 * Returns a pointer to the DOI definition on success and NULL on failure.
 */
static struct cipso_v4_doi *cipso_v4_doi_search(u32 doi)
{
	struct cipso_v4_doi *iter;

	list_for_each_entry_rcu(iter, &cipso_v4_doi_list, list)
		if (iter->doi == doi && iter->valid)
			return iter;
	return NULL;
}

/**
 * cipso_v4_doi_add - Add a new DOI to the CIPSO protocol engine
 * @doi_def: the DOI structure
 *
 * Description:
 * The caller defines a new DOI for use by the CIPSO engine and calls this
 * function to add it to the list of acceptable domains.  The caller must
 * ensure that the mapping table specified in @doi_def->map meets all of the
 * requirements of the mapping type (see cipso_ipv4.h for details).  Returns
 * zero on success and non-zero on failure.
 *
 */
int cipso_v4_doi_add(struct cipso_v4_doi *doi_def)
{
	u32 iter;

	if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
		return -EINVAL;